Age-dependent effect of every-other-day feeding and aerobic exercise in ubiquinone levels and related antioxidant activities in mice muscle

CYB5R3 overexpression preserves skeletal muscle mitochondria and autophagic signaling in aged transgenic mice

Cytochrome b₅ reductase 3 (CYB5R3) overexpression activates respiratory metabolism and exerts prolongevity effects in transgenic mice, mimicking some of the salutary effects of calorie restriction. The aim of our study was to understand how CYB5R3 overexpression targets key pathways that modulate the rate of aging in skeletal muscle, a postmitotic tissue with a greater contribution to resting energy expenditure. Mitochondrial function, autophagy and mitophagy markers were evaluated in mouse hind limb skeletal muscles from young-adult (7 months old) and old (24 months old) males of wild-type and CYB5R3-overexpressing genotypes. Ultrastructure of subsarcolemmal and intermyofibrillar mitochondria was studied by electron microscopy in red gastrocnemius. CYB5R3, which was efficiently overexpressed and targeted to skeletal muscle mitochondria regardless of age, increased the abundance of complexes I, II, and IV in old mice and prevented the age-related decrease of complexes I, III, IV, and V and the mitofusin MFN-2. ATP was significantly decreased by aging, which was prevented by CYB5R3 overexpression. Coenzyme Q and the mitochondrial biogenesis markers TFAM and NRF-1 were also significantly diminished by aging, but CYB5R3 overexpression did not protect against these declines. Both aging and CYB5R3 overexpression upregulated SIRT3 and the mitochondrial fission markers FIS1 and DRP-1, although with different outcomes on mitochondrial ultrastructure: old wild-type mice exhibited mitochondrial fragmentation whereas CYB5R3 overexpression increased mitochondrial size in old transgenic mice concomitant with an improvement of autophagic recycling. Interventions aimed at stimulating CYB5R3 could represent a valuable strategy to counteract the deleterious effects of aging in skeletal muscle.

Levels of Plasma Coenzyme Q10 Are Associated with Physical Capacity and Cardiovascular Risk in the Elderly

Coenzyme Q₁₀ (CoQ₁₀) is an essential factor for mitochondrial activity and antioxidant protection of cells, tissues and plasma lipoproteins. Its deficiency has been associated with aging progression in animals and humans. To determine if CoQ₁₀ levels in plasma can be associated with frailty in elderly people (aged > 65), we studied the relationship of CoQ₁₀ levels in blood with other parameters in plasma and with the physical activity and capacity in aged people. Our results indicate that high CoQ₁₀ levels are directly associated with lower cardiovascular risk measured by the quotient total cholesterol/HDL cholesterol. Furthermore, high CoQ₁₀ levels were found in people showing higher physical activity, stronger muscle capacity. CoQ₁₀ also showed a strong inverse relationship with sedentarism and the up and go test, which is considered to be a frailty index. Interestingly, we found gender differences, indicating stronger correlations in women than in men. The importance of the maintenance of CoQ₁₀ levels in elderly people to avoid sarcopenia and frailty in elderly people is discussed.

Cellular Models for Primary CoQ Deficiency Pathogenesis Study

Primary coenzyme Q₁₀ (CoQ) deficiency includes a heterogeneous group of mitochondrial diseases characterized by low mitochondrial levels of CoQ due to decreased endogenous biosynthesis rate. These diseases respond to CoQ treatment mainly at the early stages of the disease. The advances in the next generation sequencing (NGS) as whole-exome sequencing (WES) and whole-genome sequencing (WGS) have increased the discoveries of mutations in either gene already described to participate in CoQ biosynthesis or new genes also involved in this pathway. However, these technologies usually provide many mutations in genes whose pathogenic effect must be validated. To functionally validate the impact of gene variations in the disease’s onset and progression, different cell models are commonly used. We review here the use of yeast strains for functional complementation of human genes, dermal skin fibroblasts from patients as an excellent tool to demonstrate the biochemical and genetic mechanisms of these diseases and the development of human-induced pluripotent stem cells (hiPSCs) and iPSC-derived organoids for the study of the pathogenesis and treatment approaches.

Regulation of coenzyme Q biosynthesis pathway in eukaryotes

Coenzyme Q (CoQ, ubiquinone/ubiquinol) is a ubiquitous and unique molecule that drives electrons in mitochondrial respiratory chain and an obligatory step for multiple metabolic pathways in aerobic metabolism. Alteration of CoQ biosynthesis or its redox stage are causing mitochondrial dysfunctions as hallmark of heterogeneous disorders as mitochondrial/metabolic, cardiovascular, and age-associated diseases. Regulation of CoQ biosynthesis pathway is demonstrated to affect all steps of proteins production of this pathway, posttranslational modifications and protein-protein-lipid interactions inside mitochondria. There is a bi-directional relationship between CoQ and the epigenome in which not only the CoQ status determines the epigenetic regulation of many genes, but CoQ biosynthesis is also a target for epigenetic regulation, which adds another layer of complexity to the many pathways by which CoQ levels are regulated by environmental and developmental signals to fulfill its functions in eukaryotic aerobic metabolism.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

Coenzyme Q redox signalling and longevity

Mitochondria are the powerhouses of the cell. They produce a significant amount of the energy we need to grow, survive and reproduce. The same system that generates energy in the form of ATP also produces Reactive Oxygen Species (ROS). Mitochondrial Reactive Oxygen Species (mtROS) were considered for many years toxic by-products of metabolism, responsible for ageing and many degenerative diseases. Today, we know that mtROS are essential redox messengers required to determine cell fate and maintain cellular homeostasis. Most mtROS are produced by respiratory complex I (CI) and complex III (CIII). How and when CI and CIII produce ROS is determined by the redox state of the Coenzyme Q (CoQ) pool and the proton motive force (pmf) generated during respiration. During ageing, there is an accumulation of defective mitochondria that generate high levels of mtROS. This causes oxidative stress and disrupts redox signalling. Here, we review how mtROS are generated in young and old mitochondria and how CI and CIII derived ROS control physiological and pathological processes. Finally, we discuss why damaged mitochondria amass during ageing as well as methods to preserve mitochondrial redox signalling with age.

Dietary Restriction and Oxidative Stress: Friends or Enemies?

Significance: It is well established that lifestyle and dietary habits have a tremendous impact on life span, the rate of aging, and the onset/progression of age-related diseases. Specifically, dietary restriction (DR) and other healthy dietary patterns are usually accompanied by physical activity and differ from Western diet that is rich in fat and sugars. Moreover, as the generation of reactive oxidative species is the major causative factor of aging, while DR could modify the level of oxidative stress, it has been proposed that DR increases both survival and longevity. Recent Advances: Despite the documented links between DR, aging, and oxidative stress, many issues remain to be addressed. For instance, the free radical theory of aging is under "re-evaluation," while DR as a golden standard for prolonging life span and ameliorating the effects of aging is also under debate. Critical Issues: This review article pays special attention to highlight the link between DR and oxidative stress in both aging and age-related diseases. We discuss in particular DR's capability to counteract the consequences of oxidative stress and the molecular mechanisms involved in these processes. Future Directions: Although DR is undoubtedly beneficial, several considerations must be taken into account when designing the best dietary intervention. Use of intermittent fasting, daily food reduction, or DR mimetics? Future research should unravel the pros and cons of all these processes. Antioxid. Redox Signal. 34, 421-438.

Targeting Nrf2 for the treatment of Duchenne Muscular Dystrophy

Imbalances in redox homeostasis can result in oxidative stress, which is implicated in various pathological conditions including the fatal neuromuscular disease Duchenne Muscular Dystrophy (DMD). DMD is a complicated disease, with many druggable targets at the cellular and molecular level including calcium-mediated muscle degeneration; mitochondrial dysfunction; oxidative stress; inflammation; insufficient muscle regeneration and dysregulated protein and organelle maintenance. Previous investigative therapeutics tended to isolate and focus on just one of these targets and, consequently, therapeutic activity has been limited. Nuclear erythroid 2-related factor 2 (Nrf2) is a transcription factor that upregulates many cytoprotective gene products in response to oxidants and other toxic stressors. Unlike other strategies, targeted Nrf2 activation has the potential to simultaneously modulate separate pathological features of DMD to amplify therapeutic benefits. Here, we review the literature providing theoretical context for targeting Nrf2 as a disease modifying treatment against DMD.

Age-related mitochondrial dysfunction as a key factor in COVID-19 disease

SARS-CoV-2 causes a severe pneumonia (COVID-19) that affects essentially elderly people. In COVID-19, macrophage infiltration into the lung causes a rapid and intense cytokine storm leading finally to a multi-organ failure and death. Comorbidities such as metabolic syndrome, obesity, type 2 diabetes, lung and cardiovascular diseases, all of them age-associated diseases, increase the severity and lethality of COVID-19. Mitochondrial dysfunction is one of the hallmarks of aging and COVID-19 risk factors. Dysfunctional mitochondria is associated with defective immunological response to viral infections and chronic inflammation. This review discuss how mitochondrial dysfunction is associated with defective immune response in aging and different age-related diseases, and with many of the comorbidities associated with poor prognosis in the progression of COVID-19. We suggest here that chronic inflammation caused by mitochondrial dysfunction is responsible of the explosive release of inflammatory cytokines causing severe pneumonia, multi-organ failure and finally death in COVID-19 patients. Preventive treatments based on therapies improving mitochondrial turnover, dynamics and activity would be essential to protect against COVID-19 severity.

Resveratrol Regulates the Expression of Genes Involved in CoQ Synthesis in Liver in Mice Fed with High Fat Diet

Resveratrol (RSV) is a bioactive natural molecule that induces antioxidant activity and increases protection against oxidative damage. RSV could be used to mitigate damages associated to metabolic diseases and aging. Particularly, RSV regulates different aspects of mitochondrial metabolism. However, no information is available about the effects of RSV on Coenzyme Q (CoQ), a central component in the mitochondrial electron transport chain. Here, we report for the first time that RSV modulates COQ genes and parameters associated to metabolic syndrome in mice. Mice fed with high fat diet (HFD) presented a higher weight gain, triglycerides (TGs) and cholesterol levels while RSV reverted TGs to control level but not weight or cholesterol. HFD induced a decrease of COQs gene mRNA level, whereas RSV reversed this decrease in most of the COQs genes. However, RSV did not show effect on CoQ₉, CoQ₁₀ and total CoQ levels, neither in CoQ-dependent antioxidant enzymes. HFD influenced mitochondrial dynamics and mitophagy markers. RSV modulated the levels of PINK1 and PARKIN and their ratio, indicating modulation of mitophagy. In summary, we report that RSV influences some of the metabolic adaptations of HFD affecting mitochondrial physiology while also regulates COQs gene expression levels in a process that can be associated with mitochondrial dynamics and turnover.

Effect of Coenzyme Q10 Alone and in Combination with Exercise Training on Oxidative Stress Biomarkers in Rats

Aim: This study aimed to determine the effect of exercise training alone and in combination with coenzyme Q10 (Q10) supplementation on the Q10 level, oxidative damage, and antioxidant defense markers in blood and skeletal muscle tissue in young and aged rats. Methods: The study included 4-month old (young) and 20-month old (aged) rats. Each group was further divided into control, exercise training, Q10 supplementation, and Q10 supplementation plus exercise training groups. The exercise training program consisted of swimming for 8 weeks, and Q10 or vehicle during the same period. Results: The Q10 concentration in plasma (P < 0.05), but not in skeletal muscle (P > 0.05) increased significantly following Q10 supplementation in both the young and aged rats. Plasma SOD and CAT activity were significantly higher in the aged rats in the Q10 and Q10 plus exercise training groups than in the other groups (P < 0.05); however, there was no significant difference between the groups in skeletal muscle (P > 0.05). Additionally, plasma and skeletal GSH levels did not differ between the groups (P > 0.05). Conclusion: The present findings indicate that Q10 supplementation increased the Q10 concentration in blood but not in skeletal muscle tissue. On the other hand, Q10 administration alone and in combination with exercise challenge improved antioxidant enzyme capacity especially in the aged rats.

Mitochondrial dysfunction in metabolism and ageing: shared mechanisms and outcomes?

Mitochondria are key in the metabolism of aerobic organisms and in ageing progression and age-related diseases. Mitochondria are essential for obtaining ATP from glucose and fatty acids but also in many other essential functions in cells including aminoacids metabolism, pyridine synthesis, phospholipid modifications and calcium regulation. On the other hand, the activity of mitochondria is also the principal source of reactive oxygen species in cells. Ageing and chronic age-related diseases are associated with the deregulation of cell metabolism and dysfunction of mitochondria. Cell metabolism is controlled by three major nutritional sensors: mTOR, AMPK and Sirtuins. These factors control mitochondrial biogenesis and dynamics by regulating fusion, fission and turnover through mito- and autophagy. A complex interaction between the activity of these nutritional sensors, mitochondrial biogenesis rate and dynamics exists and affect ageing, age-related diseases including metabolic disease. Further, mitochondria maintain a constant communication with nucleus modulating gene expression and modifying epigenetics. In this review we highlight the importance of mitochondria in ageing and the repercussion in the progression of age-related diseases and metabolic disease.

Sirtuins as Mediator of the Anti-Ageing Effects of Calorie Restriction in Skeletal and Cardiac Muscle

Fighting diseases and controlling the signs of ageing are the major goals of biomedicine. Sirtuins, enzymes with mainly deacetylating activity, could be pivotal targets of novel preventive and therapeutic strategies to reach such aims. Scientific proofs are accumulating in experimental models, but, to a minor extent, also in humans, that the ancient practice of calorie restriction could prove an effective way to prevent several degenerative diseases and to postpone the detrimental signs of ageing. In the present review, we summarize the evidence about the central role of sirtuins in mediating the beneficial effects of calorie restriction in skeletal and cardiac muscle since these tissues are greatly damaged by diseases and advancing years. Moreover, we entertain the possibility that the identification of sirtuin activators that mimic calorie restriction could provide the benefits without the inconvenience of this dietary style.

Does eating less make you live longer and better? An update on calorie restriction

The complexity of aging is hard to be captured. However, apart from its tissue-specific features, a structural and functional progressive decline of the whole organism that leads to death, often preceded by a phase of chronic morbidity, characterizes the common process of aging. Therefore, the research goal of scientists in the field moved from the search for strategies able to extend longevity to those ensuring healthy aging associated with a longer lifespan referred to as “healthspan”. The aging process is plastic and can be tuned by multiple mechanisms including dietary and genetic interventions. To date, the most robust approach, efficient in warding off the cellular markers of aging, is calorie restriction (CR). Here, after a preliminary presentation of the major debate originated by CR, we concisely overviewed the recent results of CR treatment on humans. We also provided an update on the molecular mechanisms involved by CR and the effects on some of the age-associated cellular markers. We finally reviewed a number of tested CR mimetics and concluded with an evaluation of future applications of such dietary approach.

Rapamycin preserves gut homeostasis during Drosophila aging

Gut homeostasis plays an important role in maintaining the overall body health during aging. Rapamycin, a specific inhibitor of mTOR, exerts prolongevity effects in evolutionarily diverse species. However, its impact on the intestinal homeostasis remains poorly understood. Here, we demonstrate that rapamycin can slow down the proliferation rate of intestinal stem cells (ISCs) in the aging guts and induce autophagy in the intestinal epithelium in Drosophila. Rapamycin can also significantly affect the FOXO associated genes in intestine and up-regulate the negative regulators of IMD/Rel pathway, consequently delaying the microbial expansion in the aging guts. Collectively, these findings reveal that rapamycin can delay the intestinal aging by inhibiting mTOR and thus keeping stem cell proliferation in check. These results will further explain the mechanism of healthspan and lifespan extension by rapamycin in Drosophila.

Resveratrol primes the effects of physical activity in old mice

Decrease in muscle mass and performance with ageing is one of the main factors of frailty in the elderly. Maintenance of muscle performance by involving in physical activities is essential to increase independence and quality of life among elderly. The use of natural compounds with ergogenic activity in old people would increase the effect of moderate exercises in the maintenance of physiological muscle capacity. Resveratrol (RSV), a polyphenol found in walnuts, berries and grapes, shows this ergogenic activity. By using young, mature and old mice as models, we have found that RSV improves muscle performance in mature and old animals but not in young animals. Without showing significant effect by itself, RSV primed the effect of exercise by increasing endurance, coordination and strength in old animals. This effect was accompanied by a higher protection against oxidative damage and an increase in mitochondrial mass. RSV increased catalase and superoxide dismutase protein levels in muscle and primed exercise to reverse the decrease in their activities during ageing. Furthermore, RSV increased the level of mitochondrial mass markers such as cytochrome C, mitochondrial transcription factor A and nuclear respiratory factor-1 in muscle in exercised animals. Our results indicate that RSV can be considered an ergogenic compound that helps maintain muscle performance during ageing and subsequently reduces frailty and increases muscle performance in old individuals practising moderate exercise.

Calorie restriction as an intervention in ageing

Ageing causes loss of function in tissues and organs, is accompanied by a chronic inflammatory process and affects life- and healthspan. Calorie restriction (CR) is a non-genetic intervention that prevents age-associated diseases and extends longevity in most of the animal models studied so far. CR produces a pleiotropic effect and improves multiple metabolic pathways, generating benefits to the whole organism. Among the effects of CR, modulation of mitochondrial activity and a decrease in oxidative damage are two of the hallmarks. Oxidative damage is reduced by the induction of endogenous antioxidant systems and modulation of the peroxidability index in cell membranes. Mitochondrial activity changes are regulated by inhibition of IGF-1 and Target of Rapamycin (TOR)-dependent activities and activation of AMP-dependent kinase (AMPK) and the sirtuin family of proteins. The activity of PGC-1α and FoxO is regulated by these systems and is involved in mitochondria biogenesis, oxidative metabolism activity and mitochondrial turnover. The use of mimetics and the regulation of common factors have demonstrated that these molecular pathways are essential to explain the effect of CR in the organism. Finally, the anti-inflammatory effect of CR is an interesting emerging factor to be taken into consideration. In the present revision we focus on the general effect of CR and other mimetics in longevity, focusing especially on the cardiovascular system and skeletal muscle.

The role of oxidative stress in skeletal muscle injury and regeneration: focus on antioxidant enzymes

Reactive oxygen species (ROS) are generated in skeletal muscle both during the rest and contractile activity. Myogenic cells are equipped with antioxidant enzymes, like superoxide dismutase, catalase, glutathione peroxidase, γ-glutamylcysteine synthetase and heme oxygenase-1. These enzymes not only neutralise excessive ROS, but also affect myogenic regeneration at several stages: influence post-injury inflammatory reaction, enhance viability and proliferation of muscle satellite cells and myoblasts and affect their differentiation. Finally, antioxidant enzymes regulate also processes accompanying muscle regeneration-induce angiogenesis and reduce fibrosis. Elevated ROS production was also observed in Duchenne muscular dystrophy (DMD), a disease characterised by degeneration of muscle tissue and therefore-increased rate of myogenic regeneration. Antioxidant enzymes are consequently considered as target for therapies counteracting dystrophic symptoms. In this review we present current knowledge regarding the role of oxidative stress and systems of enzymatic antioxidant defence in muscular regeneration after both acute injury and persistent muscular degeneration.

Cytochrome b5 reductase, a plasma membrane redox enzyme, protects neuronal cells against metabolic and oxidative stress through maintaining redox state and bioenergetics

The plasma membrane redox system (PMRS) containing NADH-dependent reductases is known to be involved in the maintenance of redox state and bioenergetics. Neuronal cells are very vulnerable to oxidative stress and altered energy metabolism linked to mitochondrial dysfunction. However, the role of the PMRS in these pathways is far from clear. In this study, in order to investigate how cytochrome b5 reductase (b5R), one of the PM redox enzymes, regulates cellular response under stressed conditions, human neuroblastoma cells transfected with b5R were used for viability and mitochondrial functional assays. Cells transfected with b5R exhibited significantly higher levels of the NAD(+)/NADH ratio, consistent with increased levels of b5R activity. Overexpression of b5R made cells more resistant to H2O2 (oxidative stress), 2-deoxyglucose (metabolic stress), rotenone and antimycin A (energetic stress), and lactacystin (proteotoxic stress), but did not protect cells against H2O2 and serum withdrawal. Overexpression of b5R induced higher mitochondrial functions such as ATP production rate, oxygen consumption rate, and activities of complexes I and II, without formation of further reactive oxygen species, consistent with lower levels of oxidative/nitrative damage and resistance to apoptotic cell death. In conclusion, higher NAD(+)/NADH ratio and consequent more efficient mitochondrial functions are induced by the PMRS, enabling them to maintain redox state and energy metabolism under conditions of some energetic stresses. This suggests that b5R can be a target for therapeutic intervention for aging and neurodegenerative diseases.

Organ and tissue-dependent effect of resveratrol and exercise on antioxidant defenses of old mice

BACKGROUND

Oxidative stress has been considered one of the causes of aging. For this reason, treatments based on antioxidants or those capable of increasing endogenous antioxidant activity have been taken into consideration to delay aging or age-related disease progression.

AIM

In this paper, we determine if resveratrol and exercise have similar effect on the antioxidant capacity of different organs in old mice.

METHODS

Resveratrol (6 months) and/or exercise (1.5 months) was administered to old mice. Markers of oxidative stress (lipid peroxidation and glutathione) and activities and levels of antioxidant enzymes (SOD, catalase, glutathione peroxidase, glutathione reductase and transferase and thioredoxin reductases, NADH cytochrome B5-reductase and NAD(P)H-quinone acceptor oxidoreductase) were determined by spectrophotometry and Western blotting in different organs: liver, kidney, skeletal muscle, heart and brain.

RESULTS

Both interventions improved antioxidant activity in the major organs of the mice. This induction was accompanied by a decrease in the level of lipid peroxidation in the liver, heart and muscle of mice. Both resveratrol and exercise modulated several antioxidant activities and protein levels. However, the effect of resveratrol, exercise or their combination was organ dependent, indicating that different organs respond in different ways to the same stimulus.

CONCLUSIONS

Our data suggest that physical activity and resveratrol may be of great importance for the prevention of age-related diseases, but that their organ-dependent effect must be taken into consideration to design a better intervention.

Mitochondrial responsibility in ageing process: innocent, suspect or guilty

Ageing is accompanied by the accumulation of damaged molecules in cells due to the injury produced by external and internal stressors. Among them, reactive oxygen species produced by cell metabolism, inflammation or other enzymatic processes are considered key factors. However, later research has demonstrated that a general mitochondrial dysfunction affecting electron transport chain activity, mitochondrial biogenesis and turnover, apoptosis, etc., seems to be in a central position to explain ageing. This key role is based on several effects from mitochondrial-derived ROS production to the essential maintenance of balanced metabolic activities in old organisms. Several studies have demonstrated caloric restriction, exercise or bioactive compounds mainly found in plants, are able to affect the activity and turnover of mitochondria by increasing biogenesis and mitophagy, especially in postmitotic tissues. Then, it seems that mitochondria are in the centre of metabolic procedures to be modified to lengthen life- or health-span. In this review we show the importance of mitochondria to explain the ageing process in different models or organisms (e.g. yeast, worm, fruitfly and mice). We discuss if the cause of aging is dependent on mitochondrial dysfunction of if the mitochondrial changes observed with age are a consequence of events taking place outside the mitochondrial compartment.

Oxidative Stress Is a Central Target for Physical Exercise Neuroprotection Against Pathological Brain Aging

Physical exercise is suggested for preventing or delaying senescence and Alzheimer's disease (AD). We have examined its therapeutic value in the advanced stage of AD-like pathology in 3xTg-AD female mice through voluntary wheel running from 12 to 15 months of age. Mice submitted to exercise showed improved body fitness, immunorejuvenation, improvement of behavior and cognition, and reduced amyloid and tau pathology. Brain tissue analysis of aged 3xTg-AD mice showed high levels of oxidative damage. However, this damage was decreased by physical exercise through regulation of redox homeostasis. Network analyses showed that oxidative stress was a central event, which correlated with AD-like pathology and the AD-related behaviors of anxiety, apathy, and cognitive loss. This study corroborates the importance of redox mechanisms in the neuroprotective effect of physical exercise, and supports the theory of the crucial role of oxidative stress in the switch from normal brain aging to pathological aging and AD.

Meal frequency and timing in health and disease

Although major research efforts have focused on how specific components of foodstuffs affect health, relatively little is known about a more fundamental aspect of diet, the frequency and circadian timing of meals, and potential benefits of intermittent periods with no or very low energy intakes. The most common eating pattern in modern societies, three meals plus snacks every day, is abnormal from an evolutionary perspective. Emerging findings from studies of animal models and human subjects suggest that intermittent energy restriction periods of as little as 16 h can improve health indicators and counteract disease processes. The mechanisms involve a metabolic shift to fat metabolism and ketone production, and stimulation of adaptive cellular stress responses that prevent and repair molecular damage. As data on the optimal frequency and timing of meals crystalizes, it will be critical to develop strategies to incorporate those eating patterns into health care policy and practice, and the lifestyles of the population.