How can insulin resistance be improved?

High-quality nutrition, reduction of unfavorable glycemic stress, regular movement, and breaking up sedentary time can improve insulin sensitivity and glucose management. Human studies and meta-analysis support these effects, but the response varies according to conditions and consistency; normal glycemia does not exclude metabolic compensations, and diagnoses or treatments require an appropriate evaluation.

What is the relationship between insulin, inflammation, and chronic diseases?

Insulin and inflammation influence each other through lipid metabolism and cellular signals that regulate growth, energy use, and immune activity; persistent imbalances can accompany various chronic diseases. The evidence includes human studies, epidemiological associations, and mechanisms in cells and animals, but it does not demonstrate a single cause nor does it authorize attributing every pathology to insulin.

Do vitamin and mineral supplements prevent chronic diseases?

No: vitamin and mineral supplements do not automatically prevent chronic diseases. Human studies and meta-analysis indicate benefits primarily when correcting a deficiency or addressing specific needs, while clinical results vary between nutrients and conditions. Mechanisms observed in cells or animals are not equivalent to clinical benefits, and adequacy must be assessed individually.

What is the Life Pathway and how does it link metabolism and chronic diseases?

The Life Pathway is an interpretive perspective that links insulin signaling, energy availability, stress, inflammation, and immunity to cellular responses and the effects of lifestyle. It is based on clinical results, epidemiological associations, and studies on cells and animals. It is not a new molecular pathway nor a single explanation for diseases, because the same signals change function according to tissue and context.

Scientific Book

The Choice to Live in Health or in Disease

“The Choice to Live in Health or in Disease” is the book by A. Colonnese and R. Panzironi that explores the relationship between nutrition, metabolism, insulin, inflammation and the immune system. Drawing on scientific evidence, it examines the biological mechanisms involved in the development of chronic diseases and the role of nutrition, physical activity, stress and micronutrients. A journey in science communication to understand how the body works, recognise risk factors and make informed everyday choices aimed at prevention, health and well-being.

Dott. A. Colonnese¹ORCID Dott. A. Colonnese , R. Panzironi²ORCID R. Panzironi

1 Nutritional Biologist, Italy
2 Independent researcher, Italy

The Choice to Live in Health or in Disease · ISBN 979-12-82692-03-8

DOI lsh.en.libro

Published 05/11/2026
Updated 05/11/2026

LIFE PATHWAY
INSULIN SIGNALLING
INSULIN RESISTANCE
PI3K/AKT/MTOR
AMPK

Life Pathway: diagram of membrane receptors and the IRS, PI3K, AKT, AMPK, TSC1/TSC2, mTOR, REDD1, and HIF-1α pathways that link nutrition, stress, nutrients, and cellular metabolism — The Life Pathway integrates membrane receptors and signals from glutamate, insulin, dopamine, vitamin D, lactate, and glucose with the IRS-1/2–PI3K–AKT, AMPK–TSC1/TSC2–mTOR, and REDD1–HIF-1α pathways, connecting stress, nutrients, and metabolism to protein synthesis and cellular homeostasis, the cornerstone of the choice between health and disease.

ABSTRACT

The book “The Choice to Live in Health or in Disease”, by Dr A. Colonnese and R. Panzironi, explores the relationships between nutrition, metabolic regulation, immunity and chronic disease. Health emerges as the dynamic result of the interaction between cellular processes, environmental conditions and behaviour, without individual choices being able to fully determine the risk of disease.

The response to a meal involves glycaemic variability, pancreatic secretion, hepatic clearance and insulin sensitivity. From the insulin receptor, the signal passes through IRS-1/2, PI3K and AKT, integrating with mTORC1, mTORC2, AMPK, HIF-1α, REDD1 and TSC1/TSC2. These regulators coordinate energy availability, protein synthesis, autophagy and adaptation to stress. The links with lipid metabolism, prostaglandins and immunometabolism help to interpret inflammation and immune differentiation, including the Th17/Treg balance. The function of each pathway depends on the context: signals needed for repair can sustain pathological processes under different conditions.

The evidence considered covers diabetes, autoimmunity, neurodegeneration, cancer and atherosclerosis, showing how shared circuits take on different roles depending on tissues and conditions. Epidemiological associations, clinical studies and experimental models call for distinct interpretations. Diet, physical activity, smoking, social relationships, stress and sleep rhythms interact with these processes. Vitamins, magnesium, omega-3s, melatonin and the bioactive compounds of spices offer further examples of cellular regulation.

The concept of the Life Pathway proposes an integrated reading of metabolic, energy and environmental networks, without identifying a new molecular pathway. This interpretive framework links biological mechanisms and everyday behaviour, supporting realistic, individualised preventive choices that are compatible with appropriate care. It remains necessary to clarify the clinical relevance of experimental mechanisms, avoiding single explanations for multifactorial diseases, distinguishing biological plausibility from evidence of efficacy and recognising the contribution of genetic, environmental and social factors as well.

We have reached the end of this book. Before we part ways, we would like to retrace the journey that has taken us from dietary habits to cellular signals, and from chronic diseases to the possibilities offered by prevention. These conclusions gather the meaning of each individual stage and reconnect them, so that what we have encountered can become knowledge applicable to daily life.

Our intention, as authors, has been to guide the reader through the biological mechanisms that contribute to health. Knowing why a behavior matters can make the desire to change it more concrete. A meal, a walk, rest, and a meaningful relationship take on a different value when we understand that they can influence how the body uses energy, copes with stress, and maintains its functions.

The title The Choice to Live in Health or Disease expresses this possibility of participation. Health also depends on genetic, environmental, and social factors that we do not choose, and no one voluntarily decides to become ill. However, there are habits we can intervene on, with different possibilities for each person. The awareness we wish to promote concerns precisely this space: recognizing what we can improve, without turning illness into a fault or prevention into a promise of invulnerability.

By following the research, we have encountered clinical results, epidemiological associations, and mechanisms studied in the laboratory. Each level contributes to our understanding, but answers different questions. Maintaining this distinction allows us to recognize opportunities without attributing the value of certainty to hypotheses. It is also the prerequisite for combining a conscious lifestyle with appropriate medical care, while respecting the complexity of the individual.

We will therefore resume the journey in the order in which it developed, allowing what unites apparently distant topics to emerge. At the end, we will give a name to the perspective that runs through them: Life Pathway, the editorial proposal with which we bring together the communication between metabolism, environment, and cellular adaptation. To understand its meaning, let us return to the point where it all began: our relationship with food.

Nutrition and changes in our habits

The first chapter invited us to view nutrition as part of our biological and daily history. Eating is a habitual act, often performed without questioning what happens afterward. Yet, the choice of foods, their processing, and the way they are combined help determine the body's responses. From this observation, the question that guided this book was born: how much of the metabolic conditions we encounter today is intertwined with habits repeated over time?

The reference to the Mediterranean dietary tradition brought us back to the quality of the meal and its overall composition. Its value, from this perspective, lies in the attention paid to food and the variety of nutritional sources. To recover this meaning, we must look beyond the name given to a diet and consider what is actually consumed, in the quantities and combinations that characterize real life.

We thus began to shift the focus from calories alone to the metabolic response. Two meals can provide energy and produce different effects on the rate of nutrient absorption, glycemia, and insulin secretion. This difference does not exhaust the nutritional value of foods, but it helps us understand why our relationship with food deserves a broader assessment than simple energy counting.

The first result of this reflection is greater attention to the consistency of habits. Metabolic health is built through behaviors that are repeated, within personal and environmental conditions that can make them easier or more difficult. For this reason, a useful dietary choice must be able to fit into daily life, maintaining nutritional adequacy and sustainability. Knowledge serves to make such choices understandable, preventing them from depending solely on prohibitions or momentary enthusiasm.

With this perspective, our journey found its concrete starting point. Food introduces substances that the body must recognize, distribute, and utilize; the response to this intake tells us something about its capacity for adaptation. Following the fate of glucose allowed us to enter into this process and understand why a value measured in the blood is only part of the story.

Glycemia and insulin in the meal response

We have moved from food to the response that a meal produces in the body. Absorbed glucose reaches the blood, while the pancreas and tissues coordinate its use. Glycemia describes one result of this work: to interpret it, one must consider the processes that determined it. The quantity of carbohydrates, the structure of the food, fiber, processing, and the composition of the meal all contribute to the speed at which glucose becomes available.

In this framework, we encountered the glycemic index and glycemic load. The former helps to compare the response to different sources of carbohydrates; the latter also introduces the quantity consumed. These are analytical tools to be placed within the context of the meal and individual characteristics. Proteins, fats, and fiber, in fact, modify digestion, absorption, and hormonal response, making the evaluation of a food through a single number insufficient.

Insulin also requires the same attention. Its secretion responds to glucose, but it integrates additional signals, including amino acids and intestinal hormones. The Food Insulin Index has helped us recognize that an insulin response does not automatically coincide with a glycemic one. Furthermore, before fully reaching peripheral circulation, insulin passes through the liver, which removes a portion of it. The measured concentration therefore depends on both pancreatic production and clearance, that is, the removal of the hormone.

This distinction has also expanded the significance of tests. Fasting glycemia captures a baseline condition; glycated hemoglobin provides information on average glucose exposure; the glucose tolerance test observes the response to a defined stimulus. In the chapter, the focus on one-hour glycemia showed us how some signs of difficulty can emerge before more evident alterations. However, none of these data, when considered in isolation, tells the whole story of metabolic function.

The conclusion is an invitation to view metabolism over time. An apparently preserved glycemia can be sustained by an increasing burden on regulatory systems. Understanding this possibility allows us to value prevention and the overall assessment of the individual. The next step was therefore to observe what happens when fluctuations increase and the collaboration between the pancreas, liver, and tissues begins to lose efficiency.

Glycemic variability and alterations preceding diabetes

Tracking glucose over time has allowed us to recognize a dimension that a single measurement leaves hidden: glycemic variability. Glucose fluctuates physiologically, but the amplitude and frequency of these excursions can change along the path toward prediabetes and diabetes. Continuous monitoring and its indicators have made these trends observable, showing how a similar average can be accompanied by different daily profiles.

The research examined links greater glycemic instability to oxidative stress, inflammation, and vascular alterations. Experimental models also show how intermittent exposure to high glucose concentrations can damage pancreatic β-cells. These observations have helped us understand a possible circuit: the difficulty in regulating glucose can increase the burden on the very cells that participate in its regulation.

Pancreatic function must therefore be interpreted in relation to the needs of the tissues. A high amount of insulin does not guarantee an adequate response if sensitivity to the hormone is reduced. For the same reason, the circulating concentration alone does not describe how much the pancreas is producing. The liver, through insulin clearance, modifies the body's exposure to the hormone; a reduction in this process can contribute to hyperinsulinemia even without an equivalent increase in secretion.

It is here that we delved into one of the central themes of the work: the bidirectional relationship between hyperinsulinemia and insulin resistance. Resistance can induce a compensatory response from the pancreas; in some contexts, high and persistent insulin exposure can, in turn, contribute to tissue desensitization. Secretion, removal, and cellular response influence each other, with a weight that changes between individuals and phases of metabolic dysfunction.

This interpretation makes the gradual nature of the deterioration more understandable. The appearance of overt hyperglycemia can be preceded by years of adaptations, during which the system maintains certain results at the cost of a growing imbalance. The interest in these transitions concerns the possibility of recognizing an unfavorable trajectory early on, through an appropriate assessment. To understand how a signal can progressively lose effectiveness, we then entered the cell, following the proteins that translate the insulin message into action.

Insulin signaling and the cell's ability to adapt

Entering the insulin pathway meant observing what happens after the hormone binds to its receptor. IRS1 and IRS2 participate in transmitting the message, PI3K supports its propagation, and AKT helps transform it into metabolic and survival responses. Nutrient availability thus becomes information capable of guiding glucose utilization, synthesis, and resource conservation.

The pathway then reaches the TSC1/TSC2 system and mTOR, one of the main integration points between energy, nutrients, and growth signals. We have distinguished between mTORC1 and mTORC2, complexes with different and interconnected functions. The former participates in the control of synthesis and autophagy; the latter contributes, among other functions, to the regulation of AKT. This distinction is necessary to understand why modifying mTOR can have different consequences depending on the context.

When mTORC1 is persistently stimulated, the circuit involving S6K1 can attenuate the upstream signal, interfering with IRS. A physiological control system can thus participate in reducing the insulin response. On the other hand, compromising necessary mTOR functions can also alter metabolism. The message that has emerged is therefore the need to preserve appropriate regulation: growth, repair, and turnover require different times and conditions.

In this network, we encountered HIF-1α and REDD1. The former connects metabolic signals to cellular adaptation, especially in relation to oxygenation; the latter participates in the stress response and can contain mTORC1 through the TSC system. These regulators show how the cell integrates information arriving from multiple directions. Food is one of them, along with energy status and tissue conditions.

The value of this stage does not lie in memorizing all the acronyms. It lies in recognizing that the insulin response depends on a distributed and regulated communication, the effectiveness of which can change over time. Insulin maintains an indispensable role; understanding its excesses and alterations means protecting the quality of its signal. From here, we moved on to a broader consequence: the same circuits that guide metabolism can interact with those that support inflammation.

The dialogue between metabolism and inflammation

The link with inflammation has taken us beyond energy distribution. We have observed how persistent metabolic stimulation can influence the availability of substances used to produce inflammatory mediators. From this perspective, hyperinsulinemia represents one of the possible elements of an altered biological environment, capable of intertwining with the processes through which cells communicate damage or a state of activation.

The path described starts from lipid metabolism. Through SREBP-1c and desaturase enzymes, insulin signaling can contribute to modifying the production of arachidonic acid. This fatty acid belongs to normal membrane physiology and constitutes the precursor of various mediators. Its presence becomes relevant to the inflammatory cascade when other signals allow for its release and utilization.

We followed this second step through MAPK/ERK, intracellular calcium, and cPLA2α, the enzyme that can make arachidonic acid available from membrane phospholipids. Subsequently, COX-2 participates in the production of prostaglandin E2. In the contexts described, the prostaglandin signal, mediated by the EP4 receptor, can communicate with EGFR and return to involve PI3K, AKT, and mTOR. Lipid metabolism and growth signaling can therefore enter into circuits of mutual influence.

This sequence has allowed us to attribute a concrete meaning to the expression metabolic inflammation. A change in the use of nutrients can contribute to changing the messages received by neighboring cells, with effects on the tissue environment. The reconstruction of a mechanism shows a biological possibility; its actual relevance depends on the intensity of the stimulus, the duration, and the other conditions present in the organism.

Attention has therefore shifted from the mediators to the cells that produce and interpret them. The macrophage can recruit other defenses, release cytokines, and influence repair. An intracellular phenomenon thus assumes a collective dimension, involving tissues and organs. To understand how a response is initiated, amplified, and finally contained, it has become necessary to understand the immune system and the energy mechanisms that support its various functions.

The immune system and its metabolic balance

With the immune system, we have encountered a network capable of recognizing threats, organizing responses, and limiting tissue damage. Innate immunity offers a first line of intervention, while adaptive immunity develops more specific responses through T and B lymphocytes. Collaboration between these systems requires communication, energy, and control: activation is necessary, but so is terminating a response once it has fulfilled its function.

Immune cells adapt their metabolism to the task at hand. Inflammatory programs are often accompanied by an increased reliance on glycolysis, while certain regulatory and repair functions depend more heavily on oxidative metabolism. Describing macrophages as M1 and M2 has helped us navigate this distinction, although these represent simplifications of more variable cellular behaviors. From this relationship between function and energy, immunometabolism is born.

mTOR and AMPK participate in coordinating these programs. mTORC1 supports processes necessary for the activation and growth of effector cells; AMPK contributes to energy adaptation and can limit costly anabolic activities. HIF-1α links part of this signaling to glycolysis and immune differentiation. The same proteins we have already encountered in metabolism thus acquire further significance: they help guide how the body's defenses utilize their resources.

The relationship between Th17 and Treg cells has made this connection particularly evident. The former participate in inflammatory responses; the latter help maintain tolerance toward the body. FOXP3 is essential for the identity and regulatory function of Tregs. Research on rapamycin, glucocorticoids, and vitamin D has shown that intervening in metabolic signals can modify these balances, with effects dependent on the cells and conditions studied.

We have therefore understood that an effective defense requires proportion, duration, and the capacity for regulation. Indiscriminately boosting immunity does not describe a sufficient biological goal; it is necessary to preserve the response appropriate to the context. This awareness has prepared us to examine autoimmune diseases, in which tolerance can deteriorate and immune activation can contribute to damage. The first step of this transition has led us to the joints, where rheumatoid arthritis makes the dialogue between inflammation and metabolism tangible.

Rheumatoid arthritis and joint response metabolism

In rheumatoid arthritis, the molecular pathway has encountered a disease that can profoundly affect movement, pain, and daily life. Joint inflammation involves immune cells and synovial tissues within a complex autoimmune process. Observing it through the lens of immunometabolism has allowed us to broaden our understanding of what sustains the inflammatory response, while keeping the person and the concrete consequences of the disease at the center.

The first element that emerged concerns the balance between lymphocyte populations. Th17 cells and their mediators can contribute to inflammation, while Treg cells participate in its containment. The relationships between Tfh, Tfr, and B lymphocytes also help us understand the production of autoantibodies. When these systems do not coordinate properly, the response can persist over time and progressively involve the joint environment.

The research considered has also documented alterations in insulin sensitivity, present in some patients even in the early stages and not solely explained by glucocorticoid treatments. This finding suggests a continuous interaction between inflammatory activity and metabolism.

mTOR represents one of the points where these aspects can converge. Its activity participates in effector cell programs, synovial proliferation, and angiogenesis. Through HIF-1α and glycolysis, growth signals can support the energy requirements of the cells involved. Studies on mTOR inhibitors show the interest in this connection as a research target. Vitamin D has also been examined for its relationship with immune tolerance and disease activity.

The lesson we take away concerns the breadth of our perspective. Controlling the disease requires specific treatments, while metabolic health constitutes a relevant dimension of overall patient care. Understanding these relationships helps explain why seemingly distant organs and systems can influence one another. From the joint, we then moved on to the skin: in psoriasis, an immediately visible manifestation has shown us once again processes that extend beyond the tissue in which they appear.

Psoriasis and signals crossing the skin

Psoriasis has taught us to look beyond the surface. Skin manifestations make visible a condition in which keratinocyte proliferation, immune activity, and inflammatory mediators influence one another. The skin thus becomes the place where we can observe the effects of altered biological communication, without the size of a lesion alone describing the complexity of the person presenting it.

Focusing on Th17 cells, IL-17, and other mediators has brought us back to the relationship between effector response and regulatory control. Treg cells may become less effective or lose stability in an inflammatory environment. Meanwhile, keratinocytes actively participate in the process, modifying their growth and communication with the body's defenses. The persistence of inflammation therefore depends on multiple players, which contribute to maintaining the altered skin microenvironment.

This dimension is accompanied by a metabolic one. In the studies examined, hyperinsulinemia and reduced insulin sensitivity were observed even in people without overt diabetes and, in some cases, without obesity. This finding invites us to consider conditions that may remain inconspicuous if one only looks at glycemia or weight. Cardiovascular and metabolic associations reinforce the importance of a comprehensive assessment, beyond the treatment of skin manifestations.

In psoriatic tissue, we have identified PI3K/AKT/mTOR and HIF-1α. These signals can support the glycolytic metabolism necessary for epidermal proliferation and the activity of certain immune cells. Research into their modulation shows how the control of growth and the control of inflammation can share targets. Vitamin D adds another link, through the regulation of skin differentiation and immunity.

This stage has brought us closer to a concrete awareness: taking care of health means also considering what is not immediately visible. The disease does not define the person and does not authorize judgments about their habits. Instead, it offers a reason to integrate knowledge and identify diverse needs. This same perspective becomes even more necessary when autoimmunity can affect different organs, as we encountered in systemic lupus erythematosus.

Lupus and the complexity of immune tolerance

In systemic lupus erythematosus, we have encountered a loss of tolerance capable of involving different organs and manifesting with highly variable clinical pictures. This diversity has reminded us how important it is to maintain an overall perspective. Autoantibodies and B-cell activation represent part of the process, embedded in a network of relationships between defenses, tissues, and metabolic signals.

The balances between Tfh and Tfr, as well as those between Th17 and Treg, have shown the importance of the systems that coordinate and contain the response. When certain effector programs prevail and regulation becomes insufficient, the ability to maintain inflammation can increase. Metabolism accompanies these changes: glycolysis, glutamine utilization, and mitochondrial activity contribute to providing the resources necessary for the different cell populations.

The insulin alterations described in studies have further expanded the picture. Reduced insulin sensitivity can be present even with normal glycemia and during clinically inactive phases. Its observation in different populations suggests that metabolic interaction deserves attention, without automatically attributing it to a single drug or a single characteristic of the disease. Here too, the direction of these relationships requires a cautious and contextual interpretation.

mTOR and HIF-1α have offered us a link between these levels. Their activity can support glycolytic programs and effector responses, while alterations in autophagy and mitochondria contribute to the cellular picture. Studies on sirolimus have shown how some of these connections can become the subject of therapeutic research. Vitamin D has been considered for its relationship with immune status and the balance between regulatory and effector populations.

The value of this stage lies in having brought us closer to a complex disease while maintaining the distinction between shared mechanisms and individual characteristics. A common network helps to formulate questions and interpret observations; the choice of treatments requires specific evidence and evaluations. With this focus, we have moved on to another environment where tolerance is essential every day: the gut, which must reconcile contact with the outside world, nutrient absorption, and protection of the organism.

The gut and maintenance of the immune barrier

In chronic inflammatory bowel diseases, the relationship between defense and tolerance takes on immediate significance. The intestinal mucosa participates in absorption while simultaneously serving as an interface with the external environment. Crohn's disease and ulcerative colitis present significant differences, but they share a persistent or recurrent inflammatory response that can profoundly affect quality of life and nutritional status.

The journey has highlighted the role of Th17 and Treg populations, along with that of macrophages and epithelial cells. The issue concerns the ability to maintain a proportionate response, protecting the tissue while addressing stimuli. Immune activity requires energy, and metabolic programs help guide it. For this reason, the barrier and defenses cannot be understood by separating them from the energy conditions of the cells.

Associations between metabolic indicators, such as the TyG index, and disease risk have opened up a further perspective. These data suggest possible links between metabolic dysfunction and intestinal inflammation, helping us recognize that gut health is part of the framework of the entire organism, with influences that can proceed in both directions.

We have found mTOR and HIF-1α in the programs that support glycolysis and inflammatory activity. In the models examined, the modulation of these pathways can modify immune populations, autophagy, and barrier integrity. Studies with mTOR inhibitors and natural compounds have provided research insights, while observations on vitamin D have drawn attention to nutritional status and immune regulation. The function of each signal remains linked to the cell type and the context.

From this stage, the value of care that considers inflammation, nutrition, and general conditions together emerges. Biological understanding makes it clearer why an intestinal problem can have consequences that extend beyond the digestive system. The same dialogue between immunity and metabolism is found in tissues with very different needs. In the next chapter, we followed it to the nervous system, where multiple sclerosis brings the protection and repair of myelin to the forefront.

Multiple sclerosis and nervous system protection

With multiple sclerosis, the focus has shifted toward a tissue where communication requires particularly delicate organization. The autoimmune involvement of myelin is accompanied by inflammation processes that can alter neurological function. Understanding the metabolic component has allowed us to add a further question to the description of the damage: what resources and signals support the cells that promote it and those that attempt to repair it?

Research on Treg cells has highlighted the role of tolerance, while Th1, Th17, and the relationships between T and B lymphocytes have shown different contributions to the autoimmune response. Microglia, part of the nervous system's defenses, also participate in building the inflammatory environment. The metabolism of individual populations thus becomes relevant for understanding how they are activated and how they maintain their function within the tissue.

In the studies examined, alterations in insulin sensitivity and increased insulin responses were also observed in the early stages of the disease. The connection with inflammatory markers and disability suggests an interplay that deserves attention. The presence of these relationships expands the assessment of the individual, without allowing multiple sclerosis to be reduced to a single metabolic alteration or automatically deducing a definitive intervention.

The most important distinction that emerged concerns mTOR. In some immune compartments, its activity can support pathogenic programs; in oligodendrocytes, however, it contributes to functions necessary for myelination. HIF-1α and glycolysis complete the link with effector responses. Experiments on pathway modulation must therefore be interpreted while keeping in mind different cells, timings, and objectives. Vitamin D also enters this network, with associations and results that must be read according to the level of evidence.

This stage makes a principle of the entire book particularly clear: the same protein can participate in both dysfunction and recovery, depending on the context in which it operates. Health requires coordination between defense and repair. After observing this need in the nervous system, we followed the relationship between autoimmunity and metabolism in a gland that helps regulate the body's activity: the thyroid, the protagonist of the subsequent reflection on Hashimoto's disease.

Hashimoto and the interplay between immunity and thyroid function

Hashimoto's thyroiditis has allowed us to observe the intersection between the immune system and endocrine regulation. The loss of tolerance toward thyroid components can be accompanied by progressive damage to the gland, with consequences that depend on residual function and individual progression. Following this process has helped us understand why the assessment of an endocrine autoimmune disease must consider multiple levels simultaneously.

We have identified the imbalance between Th17 and Treg cells and the role of regulatory populations in containing the response. Within the tissue, oxidative stress, autophagy, and growth signals can influence the ability of cells to remain functional. Autoimmunity therefore involves a dialogue between the defenses and the conditions of the target cells, which in turn participate in the environment in which the response develops.

Observations on insulin resistance have added a metabolic dimension. In the studies considered, reduced insulin sensitivity was documented even in people with preserved thyroid function. This association suggests that autoimmunity and metabolism can interact beyond the effects of hormonal variations. The weight of the different factors remains individual and requires a comprehensive reading, in which visceral adiposity and other concomitant conditions play a role.

At the molecular level, PI3K/AKT/mTOR and HIF-1α link growth, autophagy, and the energy programs of immune cells. Experimental results with rapamycin and other compounds show how the modulation of these signals can reduce some aspects of damage in the models studied. Vitamin D has been analyzed for its effects on autoantibodies and immune regulation. These observations enrich our biological understanding, while keeping preclinical results distinct from established therapies.

The takeaway message concerns the possibility of recognizing complementary needs: preserving endocrine function, monitoring the autoimmune process, and considering metabolic and nutritional status. Knowledge of these connections helps to avoid a fragmented interpretation of tests and symptoms. From this gland, we have moved on to the pancreas, where the loss of tolerance specifically affects the cells that produce the hormone that has accompanied us from the beginning: insulin, which is essential for understanding type 1 diabetes.

Type 1 diabetes and pancreatic cell loss

In type 1 diabetes, the link between immunity and metabolism becomes particularly evident. The autoimmune response damages pancreatic β-cells, progressively reducing the ability to produce insulin. The hormone we have followed as a metabolic signal takes on the concrete meaning here of a function that must be replaced when it fails. This characteristic distinguishes the disease and makes it essential to preserve its specificity throughout this discussion.

The journey has shown that tolerance depends on the function of Tregs, as well as their number. Insufficient regulation can leave room for autoreactive populations, including those that participate in the response against pancreatic cells. Research on the expansion or transfer of Tregs has illustrated the interest in strategies capable of recovering more selective control of the immune response.

Insulin sensitivity can also modify the clinical picture. In some at-risk subjects and in people with established disease, reduced efficacy of available insulin has been observed. This element can increase metabolic complexity without replacing the central role of the autoimmune loss of β-cells. The availability of the hormone and the response of the tissues are different dimensions, which can influence each other in determining glycemic control.

mTOR, HIF-1α, and glycolysis participate in the energy programs of effector cells, while AMPK and autophagy have also been examined in relation to the resilience of pancreatic cells. Studies on rapamycin have highlighted the opportunities and limitations of a modulation that must respect different functions. Vitamin D has been considered for its possible relationships with tolerance and metabolism, without such results modifying the need for insulin therapy when indicated.

The lesson of this chapter is therefore twofold: to recognize shared mechanisms and to protect clinical differences. Metabolic care accompanies a disease whose autoimmune origin can also be attributed to a dietary choice. Understanding this step allows us to address the next one with greater precision. In type 2 diabetes, in fact, the loss of pancreatic function is part of a different history, in which tissue sensitivity, secretion, and insulin clearance take on characteristic relationships.

Type 2 diabetes and progressive metabolic deterioration

Type 2 diabetes has brought us back to the early signals encountered at the beginning of this work, showing how they can fit into a long and complex process. Increased glycemia is a central element of the diagnosis, but the disease involves the interaction between the pancreas, liver, muscle, and adipose tissue. Over time, it can be accompanied by complications affecting numerous organs, making the systemic dimension of the metabolic imbalance evident.

Postprandial excursions and glycemic variability can increase before more stable hyperglycemia occurs. Meal composition influences these responses and offers one of the areas for intervention. Studies on low carb dietary strategies have shown potential benefits for glycemic control, which should be interpreted in conjunction with food quality, adherence, and individual needs. The value of a strategy is also measured by the ability to maintain it adequately over time.

The deterioration of β-cells includes alterations in the early insulin response and the ability to compensate for the body's demands. In parallel, a reduction in insulin clearance can increase exposure to insulin. Hyperinsulinemia and insulin resistance can thus contribute to mutually reinforcing cycles. There is, therefore, a dynamic relationship between the production, removal, and efficacy of the hormone.

Inside the cell, the feedback of mTORC1 and S6K1 on IRS helps us understand one of the mechanisms that can reduce signal quality. AMPK, on the other hand, highlights the ability to adapt to energy demand and support resource utilization. When the imbalance persists, oxidative stress, glucotoxicity, lipotoxicity, and mitochondrial difficulties can converge on the pancreas, reducing its functional capacity.

The preventive significance of this reconstruction is recognizing that the metabolic course develops over time and can be addressed through appropriate nutritional interventions at different stages. A diagnosis requires treatment; the signals that precede it deserve attention and evaluation. This vision has then led us beyond peripheral metabolism, toward an organ that continuously depends on the availability of energy: the brain. In Alzheimer's, we have observed how insulin signaling, glucose utilization, and cellular maintenance can intertwine with neurological deterioration.

Alzheimer's and brain metabolism fragility

In the chapter dedicated to Alzheimer's, we broadened the perspective on neurodegeneration, adding the issue of the brain's energy balance to the accumulation of beta-amyloid and tau. Neurons must maintain communication, integrity, and the turnover of their components. When these functions lose coordination, the alterations can influence each other, contributing to the progressive vulnerability of the networks that support memory and cognitive abilities.

Reduced brain response to insulin was examined as part of this framework and can be observed even in the absence of diabetes. The described models link insulin signaling to beta-amyloid management, protein processing, and autophagy. The IDE enzyme, involved in the degradation of both insulin and beta-amyloid, introduces another possible point of interaction, the relevance of which depends on the biological context.

mTOR participates in functions necessary for synaptic plasticity and memory. However, its altered regulation can be accompanied by a reduced capacity for turnover and the accumulation of harmful components. Feedback on IRS and the regulation of AKT and GSK3β also help to reconstruct possible links with tau modifications. Understanding these mechanisms requires preserving the physiological role of the very proteins involved in the dysfunction.

We also followed glutamate, whose communication must be controlled to avoid excessive excitation. Alterations in its release and removal can aggravate neuronal stress. Meanwhile, mitochondrial difficulties and modifications of the GLUT1 and GLUT3 transporters can reduce the effective availability of energy. HIF-1α enters this network as a regulator of metabolic responses, once again showing effects linked to the tissue and conditions considered.

The chapter has therefore provided us with an interpretation in which proteins, signals, and metabolism participate in the same biological problem. Metabolic associations do not equate to a single explanation for Alzheimer's, but they contribute to understanding its complexity. From a tissue struggling to maintain its functions, we have moved to cells capable of reorganizing resources to support pathological growth. It is this change in perspective that introduced us to the metabolism of tumors.

Tumors and the organization of the metabolic microenvironment

In tumors, we have observed how a cell can modify its use of resources and its communication with the surrounding environment. Genetic alterations maintain an essential role, while metabolism, growth signals, and interactions with other cells contribute to the complexity of the process. The perspective of this work has led us to follow these connections, distinguishing what supports a biological possibility from what demonstrates a therapeutic benefit.

Insulin also transmits growth and survival signals. Epidemiological associations between hyperinsulinemia, insulin resistance, and certain oncological conditions have raised questions about the metabolic context in which neoplasms develop. Through PI3K, AKT, and mTOR, these signals can interact with synthesis and proliferation programs. However, their significance depends on the characteristics of the tumor and the alterations present in the cells.

Growth requires materials as well as energy. The Warburg effect describes the increased reliance on glycolysis, even when oxygen is available, observed in many neoplastic cells. HIF-1α contributes to adaptation to oxygenation conditions and to the regulation of transporters and enzymes. Glucose thus enters metabolic programs that can support the construction of new cellular components and the production of lactate.

Lactate itself has expanded our understanding. Through MCT1 and MCT4, it can be exchanged between cells, becoming a resource in certain compartments of the tumor. Its signaling activity and the processes of lactylation link metabolism and cellular regulation. Tumor-associated fibroblasts participate in these exchanges: in the reverse Warburg effect, some stromal cells provide metabolites that can be used by neoplastic cells. The tumor tissue thus appears as a cooperative and heterogeneous environment.

This organization interacts with the systems that control damage and proliferation. p53 contributes to cellular surveillance; the relationship between AKT, MDM2, and p53 shows how survival signals can interfere with this protection. AMPK and TSC1/TSC2 add connections to the control of mTOR. Tumor development therefore also depends on the ability of altered cells to overcome the limits normally imposed on growth.

The microenvironment also includes immune defenses. Hypoxia, lactate, and adenosine can foster conditions that reduce the effectiveness of the antitumor response. CD39 and CD73 participate in the production of adenosine, while its receptors transmit its effects. Macrophages and Tregs can take on functions that, in this context, favor tolerance toward the tumor. Finally, VEGF links metabolic adaptation to the formation of new blood vessels.

This stage has helped us understand how the same mechanism can have different effects depending on the context: curbing the immune response can protect against the damage of autoimmunity, but it can also weaken defenses against a tumor. Studying metabolism therefore allows us to better understand these balances and opens up new research perspectives. Following the thread that connects metabolism, lipids, and inflammation, we then shifted our focus from the blood vessels that feed the tumor to the arterial wall, to understand how these factors contribute to the development of atherosclerosis.

Atherosclerosis and vascular wall protection

In atherosclerosis, we encounter a process that can develop slowly before a cardiovascular event makes it evident. The arterial wall actively participates in flow regulation, immune communication, and lipid management. The endothelium, the inner lining of blood vessels, provides a privileged vantage point for understanding how the quality of metabolic signals can influence vascular health.

Under physiological conditions, the IRS/PI3K/AKT pathway contributes to activating eNOS and producing nitric oxide. This molecule promotes vasodilation and supports the protective functions of the endothelium. When insulin signaling loses efficacy, this contribution may be reduced. This chapter has thus reminded us that insulin retains important actions for vascular physiology and that its concentration must be interpreted in conjunction with tissue response.

The reduction in endothelial protection is intertwined with inflammation and the adhesion of immune cells. Signals such as NF-κB and VCAM-1 participate in leukocyte recruitment, while lipoproteins present in the wall can undergo oxidative modifications. Oxidized LDL are recognized by receptors such as CD36, which facilitate their entry into macrophages. Lipid accumulation contributes to the formation of foam cells, which are characteristic components of atherosclerotic lesions.

CD36 has shown us how uptake and signaling can proceed together. In macrophages, it contributes to inflammatory responses and lipid accumulation; on platelets, it can participate in increasing reactivity to stimuli. PI3K/AKT/mTOR and autophagy add links to the cells' ability to manage lipids. These processes belong to a network in which insulin metabolism, oxidative stress, and the vascular environment can influence one another.

This reconstruction has made the concept of long-term prevention more concrete. Vascular health depends on the combination of risk factors and appropriate care, while the metabolic dimension helps us understand some less visible connections. After following these relationships in pathologies, it was necessary to return to daily life. Nutrition, introduced at the beginning as a starting point, has reappeared with a broader meaning: as one of the repeated exposures through which we can help modify the biological context of the organism.

Dietary quality in daily prevention

Returning to nutrition after examining various pathologies has allowed us to better understand its role as a risk factor. Every meal triggers glycemic and insulin responses which, when repeated over time, can contribute to altering metabolic balance. Attention has focused primarily on the quantity and quality of carbohydrates: rapidly digestible foods and portions with a high glycemic load can produce more marked increases in glucose and a greater demand for insulin.

The research examined has associated a high glycemic index, a high glycemic load, and a greater insulinemic potential of the diet with an increased risk of type 2 diabetes and, in various populations, of general, cardiovascular, and oncological mortality. These results suggest that dietary quality deserves attention beyond just weight control. In prediabetes, in particular, a high glycemic load has been associated with a greater probability of progression toward the disease.

Cardiovascular involvement has shown us how the consequences can extend to blood vessels. Repeated glycemic excursions can promote oxidative stress, inflammation, and endothelial dysfunction, processes that contribute to the vulnerability of the arterial wall. Associations with coronary heart disease, atherosclerosis, and stroke fit into this framework. Studies on dementia and Alzheimer's have also drawn attention to dietary glycemic exposure, without demonstrating that it directly causes neurodegeneration.

In the oncological field, hyperinsulinemia and signaling of the PI3K/AKT/mTOR axis offer possible links between nutrition, cell growth, and survival. In autoimmunity, however, alterations in insulin sensitivity suggest an interaction with inflammation, but do not prove that reducing glycemic load prevents these diseases.

Intervention studies have therefore indicated some concrete possibilities. Diets with a lower glycemic index and load can improve insulinemia, HOMA-IR, and certain inflammatory markers; low carb strategies can promote glycemic control and improve triglycerides and hepatic steatosis. However, the effects depend on the overall quality of the diet, the substitute foods, and the continuity of the intervention.

The concluding message therefore concerns the ability to reduce unfavorable metabolic stress through appropriate portions, quality food sources, and meals tailored to individual needs. Understanding these relationships makes daily choices more conscious. Their effect then intertwines with the use of nutrients: hence the transition to movement, which increases the energy demand of muscles and contributes to glucose regulation.

Movement and alternating between work and recovery

After observing how nutrition influences nutrient availability, we explored how movement conditions their utilization. Prolonged sedentary behavior reduces the energy demand of muscles and can promote alterations in insulin sensitivity. The studies examined associate the accumulation of hours spent sitting with an increase in mortality and cardiovascular and metabolic risk, also drawing attention to the duration of consecutive periods of immobility.

This aspect allowed us to distinguish between exercise and movement distributed throughout the day. Engaging in physical activity is important, but spending many consecutive hours sitting can maintain a component of risk even in people who exercise. Breaking up immobility and replacing part of it with light activity therefore represents a concrete opportunity. Research on daily steps shows benefits even in the transition from inactivity to relatively modest amounts of movement, which is particularly relevant for the elderly and frail individuals.

The link with insulin resistance makes the biological significance of these observations clearer. Even short periods of marked reduction in activity can worsen the tissue response to insulin. Conversely, aerobic exercise, resistance training, and combined programs can improve glucose uptake, mitochondrial function, and indicators of insulin sensitivity. These effects can appear even without significant weight loss: the benefit directly concerns muscle function.

During contraction, the consumption of ATP, the main cellular energy resource, increases. AMPK helps recognize this increased demand and promotes the processes necessary to satisfy it, supporting the use of fatty acids and glucose uptake through GLUT4. Movement thus modifies the ability of cells to utilize available nutrients.

This response is coordinated with mTOR, which is involved in protein synthesis, repair, and muscle adaptation. The relationship between the two pathways varies according to the type of exercise, its intensity, and the recovery phase. Autophagy and mitochondrial turnover also participate in these adaptations, contributing to the maintenance of cellular efficiency.

The conclusion is therefore concrete: reducing sedentary time, breaking up long periods of sitting, and practicing physical activity appropriate to one's condition are complementary behaviors. Their consistency supports glucose regulation and muscle functionality, offering benefits that go beyond caloric expenditure. Alongside these favorable habits, we then examined an exposure capable of compromising metabolism and vascular health: smoking, the impact of which also involves the circuits that make it difficult to stop consumption.

Smoking and the circuits that maintain addiction

After observing how physical activity supports metabolic health, we examined an exposure capable of compromising it: smoking. Its effects reach the lungs, blood vessels, and tissues, also involving the brain's addiction circuits. The research analyzed shows that even a few cigarettes a day increase cardiovascular risk and mortality. Reducing consumption, therefore, does not eliminate the risk associated with exposure.

The damage develops through processes that can reinforce each other. Oxidative stress and inflammation compromise endothelial function, while increased platelet reactivity promotes thrombus formation. In parallel, the carcinogenic substances in tobacco can damage DNA. Quitting progressively alters this trajectory, offering cardiovascular, respiratory, and oncological benefits even after years of consumption.

The metabolic involvement brought us back to insulin signaling. In smokers, lower insulin sensitivity and alterations associated with the quantity and duration of exposure have been documented. Nicotine can contribute to these effects even independently of combustion. In experimental models, the modulation of mTOR and alterations in IRS-1 help explain how the effectiveness of the insulin response can be reduced, increasing the body's need for compensation.

These same signals take on further significance in tumor processes. Nicotine and NNK, a carcinogenic tobacco nitrosamine, can involve nicotinic receptors and activate PI3K/AKT/mTOR. In the models studied, this pathway supports proliferation, angiogenesis, and resistance to cell death. NNK can also cause DNA alterations: genetic damage and survival signals can thus converge, favoring the persistence of altered cells.

Electronic cigarettes also require attention. The absence of combustion reduces exposure to some toxins, but it does not make aerosols harmless, as they can contain nicotine, aldehydes, ultrafine particles, and metals. Different products present different profiles, and combined use with traditional cigarettes maintains exposure to the harms of smoking.

The difficulty of stopping consumption is ultimately explained by addiction circuits. Nicotine increases dopamine release in reward systems; synaptic plasticity processes, in which mTOR also participates, help consolidate the associations between the substance, gratification, and habits.

Understanding these mechanisms means recognizing both the value of cessation and the need to support those who undertake it. Knowledge of the risks can be motivating, while an appropriate program helps maintain the change. From here, we moved on to the role of social relationships, which can offer concrete support for health care and managing difficulties.

Social relationships and biological responses to loneliness

After examining smoking and the difficulties associated with addiction, we explored another factor that can influence health: the lack of meaningful relationships. The studies analyzed associate social isolation and persistent loneliness with an increase in mortality and cardiovascular risk. The quality of our bonds therefore takes on concrete value, as it can influence both daily behaviors and the biological systems through which we cope with stress.

An evolutionary perspective has helped us understand this relationship. Cooperation, resource sharing, and social learning have supported human survival. Even today, being able to count on others makes it easier to manage difficulties and practice self-care. Observations on isolation during childhood and adolescence also suggest that vulnerability can begin early, associating with greater inflammation and cardiometabolic alterations in later years.

Part of the risk is mediated through habits. Isolation can be accompanied by less adequate nutrition, nutritional deficiencies, increased tobacco use, less physical activity, and difficulty in adhering to medical treatments. These conditions can accumulate and reinforce one another. Social support, on the other hand, can make lifestyle changes more achievable and foster their consistency. The quality of relationships is what matters most: having numerous contacts does not guarantee feeling heard, understood, or supported.

The connection also extends to metabolism. The research examined associates loneliness and poor social support with insulin resistance and alterations in glycemic regulation. A possible explanation involves the hypothalamic-pituitary-adrenal axis: persistent loneliness can be accompanied by changes in the stress response and cortisol rhythms, influencing the availability and utilization of energy.

At the cellular level, in fact, glucocorticoids can induce REDD1, which, through TSC1/TSC2, contributes to containing mTORC1 activity. This response temporarily limits energy-intensive processes, such as protein synthesis, but prolonged activation of stress signals can promote catabolism and metabolic dysfunction. Other experimental evidence shows that the impairment of mTORC2 can interfere with AKT, AS160, and GLUT4, reducing glucose uptake; these mechanisms help interpret the link between stress and metabolism.

The conclusion is that health also requires attention to relational conditions. Recognizing loneliness and fostering reliable bonds can support daily self-care and reduce the burden of difficulties. To better understand how these experiences reach our tissues, the journey continued with stress and the hormonal signals that connect personal experience to metabolic regulation.

Chronic stress and metabolic regulation

After exploring the role of social relationships, we followed the primary link between daily experiences and metabolic regulation: the stress response. When faced with a threat, whether real or perceived, the body activates systems that make the necessary resources available to cope with it. The risk arises when this pressure persists and recovery becomes insufficient, promoting alterations in hormonal regulation and energy utilization.

At the center of this response, we find the hypothalamic-pituitary-adrenal axis and cortisol. The research examined describes changes in its daily rhythm and the awakening response, along with associations with hypertension and metabolic alterations. Chronic stress can therefore affect health through a dysregulation of the neuroendocrine response, which does not necessarily coincide with a constant increase in cortisol in every person.

Metabolically, cortisol increases hepatic glucose production and can reduce its utilization in peripheral tissues. Interference with IRS-1, PI3K/AKT, and the mechanisms that mobilize GLUT4 can make insulin action less effective. Initially, the pancreas may compensate by producing more insulin and maintaining an apparently normal glycemia. This compensation helps explain why an alteration in insulin sensitivity can develop before an evident increase in glucose, even independently of obesity.

The connection to cellular regulation also involves REDD1, a protein whose expression can be induced by glucocorticoids. Through TSC1/TSC2, REDD1 contributes to reducing mTORC1 activity and protein synthesis. A temporary response can support adaptation; if prolonged, it can contribute to catabolism and muscle mass loss. Evidence on the impairment of mTORC2 also shows possible consequences on AKT activation, but this mechanism must be distinguished from the mere reduction of mTORC1.

The pathway finally reaches the AKT–AS160–GLUT4 system. The phosphorylation of AS160 by AKT promotes the transfer of vesicles containing GLUT4 to the membrane, increasing glucose entry, especially in muscle and adipose tissue. Alterations in signaling or vesicle trafficking can hinder this process and contribute to insulin resistance.

We have thus understood why persistent stress represents a risk factor to be considered alongside diet, physical activity, and other personal conditions. Recognizing sources of overload and enabling recovery means paying attention to metabolic health as well. To complete this understanding, we have therefore traced back to the origin of the response: the brain circuits that transform the perception of a threat into hormonal signals capable of reaching the entire organism.

From nerve signal to hormonal response

After observing the effects of cortisol on metabolism, we traced the pathway back to understand how the stress response originates. Before hormones reach the tissues, the brain must recognize a threat—whether real or perceived—and coordinate the signals necessary to address it. The risk arises when this activation is prolonged and the systems meant to contain it fail to facilitate adequate recovery.

Glutamate, the primary excitatory neurotransmitter, participates in the communication between the involved circuits. Its activity is intertwined with mTOR, which contributes to the function and plasticity of synapses. Astrocytes maintain the balance of this communication by removing glutamate from the extracellular space and participating in its recycling. In the experimental models described, altered regulation of mTOR can compromise these functions, promoting glutamate accumulation, increased excitability, and neuroinflammatory signals.

This connection has shown us how the metabolic conditions of cells can influence the activity of neural networks. Glutamatergic signals also reach the neurons that produce orexin, located in the lateral hypothalamus. Orexin supports wakefulness and helps activate alertness systems, creating connections through which the response can be maintained and amplified.

Among the structures involved is the locus coeruleus, a brain nucleus that produces noradrenaline. The convergence of orexinergic and glutamatergic signals promotes its activation, preparing the body for attention and action. This response is functional when it accompanies a temporary need; its persistence, however, can hinder the return to conditions compatible with rest and recovery.

The transition to the endocrine response involves the paraventricular nucleus of the hypothalamus. Noradrenergic signals help regulate the neurons that produce CRH, the hormone that stimulates the anterior pituitary to release ACTH. The latter reaches the adrenal cortex and induces the production of cortisol. Through this network, brain activation takes on a systemic dimension, modifying energy availability, cardiovascular function, and immune system activity.

Circadian rhythms and negative feedback normally help regulate the response. When stress persists, hormonal rhythmicity, sensitivity to glucocorticoids, and the control of inflammation can be altered. The circuits described are therefore important links between the perception of a threat and biological consequences, within a broader and more complex regulation.

The conclusion concerns the ability to recover after activation: protecting health also means recognizing the conditions that keep the body on alert. The functioning of these networks also depends on the resources available to the cells. From here, the path has brought us back to nutrition, delving into the role of vitamins and minerals in supporting metabolic homeostasis.

Micronutrients and nutritional adequacy

After exploring the stress response, we examined another condition capable of compromising the body's balance: micronutrient deficiency. Vitamins, minerals, and trace elements are necessary to produce energy, support immune defenses, repair DNA, and maintain antioxidant protection. Insufficient availability can therefore weaken multiple functions simultaneously, even when the diet provides sufficient or excessive calories.

This is the meaning of so-called hidden hunger: eating enough does not guarantee that you are consuming everything your cells need. Overweight and obesity can coexist with nutritional deficiencies, making an assessment based solely on weight insufficient. The research examined associates a better micronutritional quality of the diet with lower overall mortality and, in various populations, lower cardiovascular and oncological mortality. These observations highlight the importance of food composition, beyond its energy content.

The link with insulin resistance makes this risk more concrete. Magnesium, zinc, calcium, potassium, and vitamin D participate, with different roles, in insulin secretion, ATP production, mitochondrial function, and the transmission of signals that allow for glucose utilization. Insufficient availability can interfere with these processes and be accompanied by oxidative stress and inflammation. In profiles characterized by multiple deficiencies, higher HOMA-IR values and poorer glycemic control have been observed.

However, the relationship can proceed in both directions. The deficiencies found in people with type 2 diabetes, including those of vitamin D, magnesium, and vitamin B12, do not necessarily represent the initial cause of the metabolic dysfunction, but can accompany or promote it. Understanding this dynamic helps to assess individual needs without attributing every alteration to a single nutrient.

Vulnerability can also begin before birth. The maternal nutritional environment contributes to pancreatic development and the metabolic regulation of the offspring. Experimental studies show that deficiencies during pregnancy and breastfeeding can modify energy and epigenetic programs, leaving effects that emerge later. These results underscore the value of nutritional adequacy in the early stages of life.

Prevention therefore requires attention to the quality and variety of the diet, along with the recognition of actual insufficiencies. Supplementation can be useful when it corrects a deficiency or meets specific needs; in people who are already adequately nourished, indiscriminately increasing vitamins and minerals does not guarantee further benefits. From this distinction, we started to delve into individual nutrients, beginning with vitamin D and its contribution to immune and metabolic regulation.

Vitamin D and the regulation of cellular functions

After recognizing the consequences of micronutrient deficiencies, we explored vitamin D, encountering functions that extend beyond the maintenance of bone health. Through the VDR receptor, present in numerous tissues, its active form helps regulate cellular programs involved in immunity, metabolism, and the stress response. This distribution helps explain why its role has been studied in different organs and conditions.

On an immune level, vitamin D participates in the coordination between defense and tolerance. It can influence antigen-presenting cells, contain certain pro-inflammatory responses, and promote the activity of regulatory T cells. It also contributes to the maintenance of the intestinal and respiratory barriers, which represent a fundamental interface between the organism and the environment. These functions offer a biological basis for interpreting the associations between vitamin deficiency, inflammation, and autoimmunity.

The link with metabolism primarily concerns pancreatic function and the response to insulin. The research examined suggests that vitamin D may act on β-cells, the inflammatory environment, and the sensitivity of peripheral tissues. Some supplementation studies have documented improvements in glycemic and insulin parameters, especially in people with insufficient initial levels. However, the extent of the benefits remains variable and depends on the characteristics of the participants and the intervention.

To understand these effects, we delved into intracellular mechanisms. In experimental models, VDR activation can increase the expression of REDD1, which, through TSC1/TSC2, helps contain mTORC1. This regulation can limit proliferative signals and promote autophagy, the process by which cells degrade and recycle part of their own components. The significance of the effect depends on the tissue and the conditions studied.

Alongside this pathway, we encountered AMPK, which is involved in energy adaptation. Research on hepatic steatosis, the gut, and osteoarthritis suggests links with glucose utilization, fat oxidation, and the management of cellular stress. Other studies have explored possible effects in diabetic nephropathy and neurological conditions, while many applications remain to be clinically confirmed.

In oncology, too, it is necessary to distinguish the results: some meta-analyses on supplementation have detected a reduction in cancer mortality, without demonstrating a significant decrease in new cases. Molecular and clinical observations therefore answer different questions.

The value of vitamin D emerges from its participation in essential functions and the possibility of correcting an insufficiency when present. Supporting its adequacy means contributing to the normal functioning of the organism, as part of comprehensive health care. From this regulation of cellular programs, we moved on to vitamin C, exploring its contribution to oxidative protection, tissue integrity, and the control of oxygenation responses.

Vitamin C: between tissue integrity and cellular response

After exploring vitamin D, we encountered another essential element for maintaining health in vitamin C. Humans cannot synthesize it and must obtain it through their diet. Its availability supports antioxidant protection, tissue formation, iron absorption, and various immune system functions. It also contributes to the synthesis of molecules involved in nerve signaling and to the activity of enzymes that participate in the regulation of gene expression.

One of its fundamental functions concerns collagen, a structural protein present in the skin, tendons, ligaments, bones, and vascular walls. Vitamin C acts as a cofactor for the enzymes necessary for its proper formation, promoting modifications that stabilize its structure. This contribution helps us understand its role in tissue integrity and repair processes, as well as the consequences of a prolonged deficiency.

Structural protection is directly linked to immune defenses. The skin and mucous membranes constitute the first barriers against external agents, while vitamin C also supports the activity of cells that intervene when these barriers are breached. It promotes neutrophil migration and phagocytosis—the ability to engulf and eliminate microorganisms—and participates in the processes that accompany the resolution of inflammation. The research examined also describes an involvement in the functions of Natural Killer cells and the maturation of T lymphocytes.

During infections, the consumption of vitamin C may increase, but its physiological functions must be distinguished from the results of supplementation. Studies on the common cold show limited benefits, particularly regarding the duration of symptoms under certain conditions, without demonstrating general prevention of the infection.

A further connection concerns HIF-1α, a protein that coordinates part of the cellular response to oxygen scarcity. Vitamin C supports the activity of hydroxylases which, when oxygen and other cofactors are available, help limit its stability and activity. This regulation affects programs related to glucose utilization, lactate production, and the formation of new blood vessels.

In oncological models, the relationship with HIF-1α has opened research perspectives on metabolism and the tumor microenvironment. Even high concentrations achievable via intravenous administration have been studied for their effects on the oxidative balance of neoplastic cells. However, these results belong to conditions different from dietary intake and do not demonstrate an anti-tumor efficacy of ordinary supplementation.

Vitamin C therefore emerges as a nutrient necessary to support complementary functions: protecting, building, repairing, and regulating. Ensuring an adequate intake contributes to the normal functioning of the body. From tissue integrity, we then moved on to the composition of cell membranes, exploring the relationship between structure, communication, and inflammation control with omega-3.

Omega-3 and cell membrane composition

After exploring the contribution of vitamin C to tissue integrity, we turned our attention to cell membranes. Here, EPA and DHA, two important omega-3 fatty acids, participate in the structure through which cells receive and transmit signals. Their incorporation modifies the lipid composition of the membranes and can influence the functioning of systems involved in communication, immunity, and metabolism.

The studies examined have documented this process in the heart, red blood cells, platelets, and immune cells. Incorporation occurs progressively and, in various compartments, is accompanied by a reduction in the proportion of arachidonic acid. This changes the availability of the precursors used to produce lipid mediators, helping to modulate the inflammatory response. This relationship should be interpreted by considering the physiological functions of both families of fatty acids, without attributing an exclusively unfavorable role to omega-6s.

These modifications lead to links with various areas of health. Research has reported favorable effects on certain cardiovascular, inflammatory, and metabolic parameters, while studies on autoimmune diseases have investigated the regulation of immune responses. In the nervous system, interest primarily concerns neuroinflammation and the maintenance of neuronal function. However, the applications explored in Alzheimer's, Parkinson's, and oncology present different levels of evidence and do not demonstrate generalizable therapeutic efficacy.

A key aspect concerns insulin sensitivity. EPA and DHA can help modulate adipose tissue inflammation, creating conditions potentially more favorable to the insulin response. Some studies conducted on gestational diabetes, polycystic ovary syndrome, and pediatric obesity have observed improvements in metabolic indicators. The results remain heterogeneous and depend on the characteristics of the individuals and the interventions.

To understand these effects, we also followed intracellular signaling. In specific experimental models, arachidonic acid can involve PI3K/AKT/mTOR; modifying its availability in membranes could therefore influence part of these signals. Other research shows that EPA and DHA can contain mTOR activity and, under certain conditions, promote autophagy, contributing to the turnover of cellular components.

AMPK completes this connection with energy regulation. Its activation, observed in various models, can participate in the effects of omega-3 on metabolism, inflammation, and the control of mTOR. These mechanisms help interpret the observations, while keeping biological plausibility distinct from proven clinical benefits.

The nutritional significance of omega-3 therefore lies in their contribution to cellular structure and regulation. An adequate intake is part of the overall quality of one's diet, while supplementation requires an assessment of individual needs. From the composition of the membranes, we then moved on to the timing of biological responses: with melatonin, we explored how daily rhythms, rest, and cellular maintenance participate in the same balance.

Melatonin and the coordination of biological rhythms

After exploring the role of omega-3 in cell membranes, we observed how the body's functioning also depends on the regularity of its rhythms. Melatonin, produced by the pineal gland and also in various peripheral tissues, participates in circadian signaling and the coordination between activity and rest. The research examined also describes its antioxidant, anti-inflammatory, and immunomodulatory actions, with possible effects on mitochondrial functionality.

The most well-known connection concerns sleep. Melatonin helps synchronize the processes that accompany the transition from wakefulness to rest. Clinical studies have documented, under specific conditions, a reduction in the time required to fall asleep and improvements in certain sleep parameters. However, the magnitude of the effects varies according to the disorder, individual characteristics, and the method of administration.

To understand its action, we followed the MT1 receptor, through which some signals are transmitted to nerve cells. In the experimental models described, this receptor participates in the regulation of the circuits that organize sleep phases. In the locus coeruleus, the reduction in the activity of noradrenergic neurons accompanies the transition to states of lower alertness and is particularly marked during REM sleep.

These circuits communicate with the orexinergic neurons of the lateral hypothalamus, which support wakefulness and stimulate alertness systems. Experimental research suggests that melatonin may also modulate their activity through MT1, contributing to the transition toward rest. We have thus encountered structures already seen in stress, understanding how much activation and recovery depend on coordinated regulation.

The presence of receptors in the pancreas, intestine, blood vessels, and immune cells extends this communication beyond the brain. Melatonin can influence insulin secretion, glucose metabolism, vascular tone, and inflammatory responses. These connections show how the circadian signal participates in the organization of the entire organism's functions.

A further aspect concerns cellular maintenance. In the models studied, melatonin modulates autophagy, through which cellular components are degraded and recycled, and mitophagy, dedicated to the removal of compromised mitochondria. AMPK and mTORC1 participate in this regulation, linking energy availability, synthesis, and turnover. The effects depend on the tissue and conditions: maintaining these processes efficiently requires appropriate modulation.

Melatonin has therefore helped us understand the relationship between biological rhythms, rest, and cellular balance. Its physiological functions offer a broad perspective, while therapeutic applications require specific evidence. From this temporal organization, we have moved on to magnesium, which is necessary for numerous reactions that support energy production and signal transmission.

Magnesium and the functioning of metabolic reactions

After exploring the relationship between melatonin, rest, and cellular maintenance, we encountered magnesium as an element necessary for the functioning of numerous biological processes. This mineral participates in hundreds of enzymatic reactions involved in energy production and utilization, nerve transmission, and muscle activity. It also contributes to vitamin D metabolism, demonstrating how the effectiveness of nutrients also depends on the availability of the cofactors necessary for their use.

Its role extends to cardiovascular regulation. The clinical studies examined have documented moderate reductions in blood pressure with supplementation, especially in people with hypertension or insufficient availability of the mineral. Epidemiological research also associates a higher dietary intake of magnesium with a lower risk of stroke, type 2 diabetes, and other cardiometabolic outcomes. These observations should be interpreted in the context of overall diet, because foods that provide magnesium also supply other useful substances.

Its participation in nerve and muscle function has suggested further areas of research. Some studies report benefits for recovery after exercise, certain sleep parameters, and symptoms of anxiety or depression. A particularly important connection concerns insulin sensitivity. Magnesium contributes to the reactions that support insulin receptor activity and the transmission of signals necessary for glucose utilization. Insufficient availability can interfere with these processes and be accompanied by inflammation and oxidative stress. Some meta-analysis and clinical trials have observed improvements in HOMA-IR and glycemic parameters, especially in people with metabolic alterations or a deficiency of the mineral.

The relationship can become reciprocal: metabolic dysfunction can promote the loss of magnesium, while insufficiency can make the insulin response less efficient. Correcting a deficiency therefore takes on concrete significance in supporting normal cellular functions.

In experimental models, we also followed the connections with AMPK, mTOR, and autophagy. Under certain conditions, magnesium can influence these systems, contributing to energy regulation and the recycling of cellular components; the effects described in bone tissue, the liver, and tumor models depend on the context.

The concluding message therefore concerns adequacy: ensuring magnesium intake means supporting reactions that are essential for health, while supplementation must respond to individual needs. From this nutritional foundation, we moved on to spices, exploring how their bioactive compounds can interact with some of the same metabolic signals.

Spices and their metabolic links

The last six chapters have brought our attention back to familiar ingredients, showing the biological complexity that can hide behind an aroma. Cinnamon, turmeric, cloves, oregano, black pepper, and ginger contain compounds capable of interacting with inflammatory and metabolic signals. Considering them together allows us to recognize the common thread that links them, while simultaneously acknowledging the differences in the evidence available for each.

Cinnamon introduced us to cinnamaldehyde, cinnamic acid, and polyphenols. Clinical studies have reported results on certain glycemic and lipid parameters, with variability also linked to the formulations used. In experimental models, the relationship with GLUT4 and AMPK offers possible explanations for the metabolic effects. Observations regarding PI3K/AKT/mTOR, HIF-1α, and autophagy, however, belong to specific contexts, including tumor models, and require an interpretation distinct from the use of the spice in a meal.

Turmeric expanded this theme through curcumin and other curcuminoids. The modulation of NF-κB, oxidative stress, and cytokines has established a link with inflammation. Clinical results on joint pain and metabolic indicators have shown promise, but also differences between preparations. Bioavailability has become an essential part of the interpretation: the amount ingested does not necessarily coincide with the amount that reaches the tissues or produces the effects observed in the laboratory.

In tumor models, curcumin can influence proliferation, apoptosis, autophagy, and ferroptosis. In other tissues, AMPK and mTOR participate in protection and adaptation responses. This diversity confirms that a molecule does not possess a single effect independent of the context. The goal of research is to understand where, how, and under what conditions a property can translate into a useful result.

With cloves, we primarily encountered eugenol. The antioxidant, anti-inflammatory, and antimicrobial properties described experimentally have opened perspectives on different tissues. The first clinical observations on extracts and glycemic parameters represent an interesting level of evidence, but one that is still limited compared to the breadth of the mechanisms explored. The involvement of AMPK, GLUT4, and autophagy makes the metabolic interest understandable, without allowing us to attribute the effects of every studied preparation to culinary use.

Oregano added carvacrol and thymol to this network. In the models examined, the modulation of oxidative stress and inflammation is accompanied by effects on insulin signaling and liver metabolism. IRS, AKT, AS160, and GLUT4 reappear in the pathway that facilitates glucose utilization. In other contexts, the reduction of proliferative signals involves PI3K/AKT/mTOR. The presence of common targets helps in forming hypotheses, but it does not make a compound equivalent to a drug that acts on part of the same network.

Black pepper led us to piperine and an additional aspect: the ability to modify the bioavailability of other substances. Associations with curcumin have been studied under various conditions, making it necessary to distinguish the effects of the combination from those of the individual components. In preclinical models, piperine, AMPK, and GLUT4 are linked to glucose uptake, while autophagy and growth signals appear in neurological and oncological studies. The modification of absorption and metabolism also explains the potential for interactions with drugs and supplements.

Finally, ginger brought many of these connections together through gingerols and shogaols. Clinical results on glycemia, glycated hemoglobin, and other metabolic indicators are encouraging, albeit with outcomes that are not always uniform. In muscle models, 6-gingerol can involve AMPK, AS160, and GLUT4; 6-shogaol has also been studied for the modulation of proliferative signals and autophagy. Observations on the intestinal barrier have brought the path back to the communication between inflammation and tissue integrity.

Viewed together, the six spices show a common point: diet introduces substances that can have biological activity beyond their energy contribution. However, the strength of the conclusions varies according to what has been studied. A cellular experiment, a standardized extract, and a culinary quantity do not represent the same exposure. Doses, absorption, and the individual's conditions determine the distance between a molecular property and a possible benefit.

Their culinary use can contribute to the variety and pleasure of a meal, while extracts require their own evaluation. No spice alone summarizes the value of an adequate diet or replaces medical treatment. The significance of these chapters has been to show, through different examples, the return of the same biological nodes: insulin, AMPK, mTOR, inflammation, and cell turnover. From this convergence, we can now take the final step and name the perspective that has connected the entire work.

Life Pathway as a unified editorial proposal

At this point, we can recognize more clearly the thread that connects the book. We have followed glucose from the meal to the tissues, observed insulin as a message, and delved into the proteins that translate it. We then encountered those same networks in immunity, in pathologies, and in responses to daily behaviors. The concept of the “Life Pathway” stems from the desire to make this continuity readable and constitutes the editorial proposal with which we wish to conclude the work.

With this name, we define the integrated functional network through which metabolic, energetic, and environmental signals converge into cellular responses. At the center of our reading, we find the pathway that runs from the insulin receptor through IRS-1/2, PI3K, and AKT, along with the regulators and effectors that expand its meaning. mTOR represents one of the main nodes of this integration; AMPK, HIF-1α, REDD1, and TSC1/TSC2 contribute to connecting energy, oxygenation, nutrient availability, and stress conditions.

The novelty we propose is both editorial and interpretive: to bring these connections together into a recognizable perspective, capable of guiding the reader through topics often addressed separately. The “Life Pathway” does not designate the discovery of a new molecular pathway distinct from those already known. It is the name assigned in this work to an integrated reading of their relationships. Its value is measured by its ability to clarify connections while preserving the complexity and limitations of available knowledge.

This clarification also allows us to understand the role of insulin. The hormone signals the availability of resources and contributes to using, storing, and allocating them for synthesis. The quality of the response depends on secretion, clearance, and tissue sensitivity. Persistent hyperinsulinemia can become part of dysfunction circuits, but the network receives many other signals, and not all diseases stem from a single insulin alteration. The “Life Pathway” preserves these relationships without flattening them into a universal sequence.

The principle that emerges concerns the capacity for modulation. A cell must be able to grow when needed, use energy during a demand, repair structures, and recycle compromised components. mTOR and AMPK participate in this coordination, with functions that change according to tissue and timing. HIF-1α contributes to metabolic adaptation; REDD1 and the TSC system introduce control signals. Health also depends on the ability to alternate appropriate programs, keeping the response proportional to conditions.

This is why we have encountered different effects of the same pathway. In muscle, synthesis signals support recovery; in some tumor cells, they can favor pathological growth. Tregs help contain autoimmunity, but in the tumor microenvironment, they can hinder the antitumor response. Autophagy contributes to turnover, while its role varies according to the condition. The unified perspective gains value precisely when it helps us interpret such differences, avoiding absolute labels for individual molecules.

The “Life Pathway” connects this complexity to daily life. Nutrition modifies nutrient availability and hormonal responses; movement increases energy demand and supports adaptations; stress, sleep, and relationships interact with neuroendocrine systems. Smoking introduces harmful exposures and involves addiction circuits. Micronutrients and lipids participate in the functioning and structure of cells. These factors meet in the organism and contribute, with different weights, to the context in which it must remain efficient.

The awareness we wish to leave the reader with stems from this vision. A habit gains meaning when we understand which functions it can support and why its continuity matters. Changing may mean making nutrition more adequate, finding opportunities for movement, protecting rest, and addressing smoking with appropriate support. Every path must consider the person's health, possibilities, and life conditions, so as to transform knowledge into realistic actions.

The choice referred to in the book's title finds its most responsible meaning here. We can participate in the care of our health, even without controlling every factor that determines it. Getting sick does not prove that one has made poor choices, just as favorable behavior does not guarantee the absence of disease. However, knowing the mechanisms allows us to recognize a space for action and to attribute value to the changes we can sustain, alongside the necessary treatments and evaluations.

With the “Life Pathway,” we therefore offer the reader a tool to hold together what they have learned. The journey ends on the narrative level, but the questions that guided it can accompany everyday decisions: what conditions am I offering my organism, what needs am I neglecting, what change can I make stable? The purpose of this work is this greater conscious participation. Understanding what happens inside us can help us take care of it with more continuity, competence, and respect for the biological complexity of life.

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What we know

Human studies show that meal composition, including the quantity and quality of carbohydrates, alters glycemia and the insulin response beyond what calories alone would suggest.
Meta-analysis and human studies indicate that physical activity and breaking up sedentary time improve insulin sensitivity, muscle glucose uptake, and cardiometabolic health, even without weight loss.
Studies on cells and animals document that mTOR and AMPK, regulators of growth and energy availability, link insulin signaling, metabolism, inflammation, immunity, and cell turnover.

FAQ

How can insulin resistance be improved?

High-quality nutrition, reduction of unfavorable glycemic stress, regular movement, and breaking up sedentary time can improve insulin sensitivity and glucose management. Human studies and meta-analysis support these effects, but the response varies according to conditions and consistency; normal glycemia does not exclude metabolic compensations, and diagnoses or treatments require an appropriate evaluation.
What is the relationship between insulin, inflammation, and chronic diseases?

Insulin and inflammation influence each other through lipid metabolism and cellular signals that regulate growth, energy use, and immune activity; persistent imbalances can accompany various chronic diseases. The evidence includes human studies, epidemiological associations, and mechanisms in cells and animals, but it does not demonstrate a single cause nor does it authorize attributing every pathology to insulin.
Do vitamin and mineral supplements prevent chronic diseases?

No: vitamin and mineral supplements do not automatically prevent chronic diseases. Human studies and meta-analysis indicate benefits primarily when correcting a deficiency or addressing specific needs, while clinical results vary between nutrients and conditions. Mechanisms observed in cells or animals are not equivalent to clinical benefits, and adequacy must be assessed individually.
What is the Life Pathway and how does it link metabolism and chronic diseases?

The Life Pathway is an interpretive perspective that links insulin signaling, energy availability, stress, inflammation, and immunity to cellular responses and the effects of lifestyle. It is based on clinical results, epidemiological associations, and studies on cells and animals. It is not a new molecular pathway nor a single explanation for diseases, because the same signals change function according to tissue and context.

References

Chapter 1 · Nutrition and changes in our habits (29)

[1] Stone agers in the fast lane: chronic degenerative diseases in evolutionary perspective

Eaton et al., 1988

Am J Med. 1988 Apr;84(4):739-49.

DOI PubMed

[2] Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets

Cordain et al., 2000

Am J Clin Nutr. 2000 Mar;71(3):682-92.

DOI PubMed

[3] Evolution of the human diet: linking our ancestral diet to modern functional foods as a means of chronic disease prevention

Jew et al., 2009

J Med Food. 2009 Oct;12(5):925-34.

DOI PubMed

[4] Paleolithic nutrition: twenty-five years later

Konner et al., 2010

Nutr Clin Pract. 2010 Dec;25(6):594-602.

DOI PubMed

[5] Por que comemos o que comemos?

Zucoloto, 2008

Editora Mauad. Rio de Janeiro. FS (2008)

[6] Australian aboriginal plant foods: a consideration of their nutritional composition and health implications

Brand-Miller et al., 1998

Nutr Res Rev. 1998 Jun;11(1):5-23.

DOI PubMed

[7] Origins and evolution of the Western diet: health implications for the 21st century

Cordain et al., 2005

Am J Clin Nutr. 2005 Feb;81(2):341-54.

DOI PubMed

[8] Evolution of the human feeding behavior

Zucoloto, 2011

Psychology & Neuroscience, 2011 4(1), 131–141.

DOI

[9] Starvation in humans: evolutionary background and contemporary implications

Prentice, 2005

Mech Ageing Dev. 2005 Sep;126(9):976-81.

DOI PubMed

[10] Animal source foods and human health during evolution

Larsen, 2003

J Nutr. 2003 Nov;133(11 Suppl 2):3893S-3897S.

DOI PubMed

[11] The paleo diet: lose weight and get healthy by eating the food you were designed to eat.

Cordain, 2002

New York: Wiley. 2002.

[12] Sedentary lifestyle a disease from XXI century

Rodulfo, 2019

Clin Investig Arterioscler. 2019 Sep-Oct;31(5):233-240.

DOI PubMed

[13] Amitriptyline at an Environmentally Relevant Concentration Alters the Profile of Metabolites Beyond Monoamines in Gilt-Head Bream

Ziarrusta et al., 2019

Environ Toxicol Chem. 2019 May;38(5):965-977. Epub 2019 Apr 2.

DOI PubMed

[14] Climate change and overfishing increase neurotoxicant in marine predators

Schartup et al., 2019

Nature. 2019 Aug;572(7771):648-650. Epub 2019 Aug 7.

DOI PubMed

[15] International table of glycemic index and glycemic load values: 2002

Foster-Powell et al., 2002

Am J Clin Nutr. 2002 Jul;76(1):5-56.

DOI PubMed

[16] Assessing the evolution of wheat grain traits during the last 166 years using archived samples

Ben Mariem et al., 2020

Sci Rep. 2020 Dec 11;10(1):21828.