Deleterious consequences of antioxidant supplementation on lifespan in a wild-derived mammal

Metabolic stress as a driver of life-history plasticity: flight promotes longevity and antioxidant production in monarch butterflies

Life-history theory predicts that increased investment in traits related to reproduction will be associated with a reduced ability to invest in survival or longevity. One mechanistic explanation for this trade-off is that metabolic stress generated from current fitness activities (e.g. reproduction or locomotion) will increase somatic damage, leading to reduced longevity. Yet, there has been limited support for this damage-based hypothesis. A possible explanation is that individuals can respond to increases in metabolic stress by plastically inducing cellular maintenance responses, which may increase, rather than decrease, longevity. We tested this possibility by experimentally manipulating investment in flight activity (a metabolic stressor) in the migratory monarch butterfly (Danaus plexippus), a species whose reproductive fitness is dependent on survival through a period of metabolically intensive migratory flight. Consistent with the idea that metabolic stress stimulated investment in self-maintenance, increased flight activity enhanced monarch butterfly longevity and somatic tissue antioxidant capacity, likely at a cost to reproductive investment. Our study implicates a role for metabolic stress as a driver of life-history plasticity and supports a model where current engagement in metabolically stressful activities promotes somatic survival by stimulating investment in self-maintenance processes.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Dietary antioxidants and lifespan: Relevance of environmental conditions, diet, and genotype of experimental models

The rise of life expectancy in current societies is not accompanied, to date, by a similar increase in healthspan, which represents a great socio-economic problem. It has been suggested that aging can be manipulated and then, the onset of all age-associated chronic disorders can be delayed because these pathologies share age as primary underlying risk factor. One of the most extended ideas is that aging is consequence of the accumulation of molecular damage. According to the oxidative damage theory, antioxidants should slow down aging, extending lifespan and healthspan. The present review analyzes studies evaluating the effect of dietary antioxidants on lifespan of different aging models and discusses the evidence on favor of their antioxidant activity as anti-aging mechanisms. Moreover, possible causes for differences between the reported results are evaluated.

Differential Expression of Metabolism-Related Genes in Plateau Pika (Ochotona curzoniae) at Different Altitudes on the Qinghai–Tibet Plateau

According to life history theory, animals living in extreme environments have evolved specific behavioral and physiological strategies for survival. However, the genetic mechanisms underpinning these strategies are unclear. As the highest geographical unit on Earth, the Qinghai–Tibet Plateau is characterized by an extreme environment and climate. During long-term evolutionary processes, animals that inhabit the plateau have evolved specialized morphological and physiological traits. The plateau pika (Ochotona curzoniae), one of the native small mammals that evolved on the Qinghai–Tibet Plateau, has adapted well to this cold and hypoxic environment. To explore the genetic mechanisms underlying the physiological adaptations of plateau pika to extremely cold ambient temperatures, we measured the differences in resting metabolic rate (RMR) and metabolism-related gene expression in individuals inhabiting three distinct altitudes (i.e., 3,321, 3,663, and 4,194 m). Results showed that the body mass and RMR of plateau pika at high- and medium-altitudes were significantly higher than those at the low-altitude. The expression levels of peroxisome proliferator-activated receptor α (pparα), peroxisome proliferator-activated receptor-γ coactivator-1α (pgc-1α), and the PR domain-containing 16 (PRDM16) in white (WAT) and brown (BAT) adipose tissues of plateau pika from high- and medium-altitudes were significantly higher than in pika from the low-altitude region. The enhanced expression levels of pgc-1α and pparα genes in the WAT of pika at high-altitude showed that WAT underwent “browning” and increased thermogenic properties. An increase in the expression of uncoupling protein 1 (UCP1) in the BAT of pika at high altitude indicated that BAT increased their thermogenic properties. The gene expression levels of pparα and pgc-1α in skeletal muscles were significantly higher in high-altitude pika. Simultaneously, the expression of the sarcolipin (SLN) gene in skeletal muscles significantly increased in high-altitude pika. Our results suggest that plateau pika adapted to an extremely cold environment via browning WAT, thereby activating BAT and enhancing SLN expression to increase non-shivering thermogenesis. This study demonstrates that plateau pika can increase thermogenic gene expression and energy metabolism to adapt to the extreme environments on the plateau.

Strategies to protect against age-related mitochondrial decay: Do natural products and their derivatives help?

Mitochondria serve vital roles critical for overall cellular function outside of energy transduction. Thus, mitochondrial decay is postulated to be a key factor in aging and in age-related diseases. Mitochondria may be targets of their own decay through oxidative damage. However, treating animals with antioxidants has been met with only limited success in rejuvenating mitochondrial function or in increasing lifespan. A host of nutritional strategies outside of using traditional antioxidants have been devised to promote mitochondrial function. Dietary compounds are under study that induce gene expression, enhance mitochondrial biogenesis, mitophagy, or replenish key metabolites that decline with age. Moreover, redox-active compounds may now be targeted to mitochondria which improve their effectiveness. Herein we review the evidence that representative dietary effectors modulate mitochondrial function by stimulating their renewal or reversing the age-related loss of key metabolites. While in vitro evidence continues to accumulate that many of these compounds benefit mitochondrial function and/or prevent their decay, the results using animal models and, in some instances human clinical trials, are more mixed and sometimes even contraindicated. Thus, further research on optimal dosage and age of intervention are warranted before recommending potential mitochondrial rejuvenating compounds for human use.

Lifelong soya consumption in males does not increase lifespan but increases health span under a metabolic stress such as type 2 diabetes mellitus

Soya consumption can decrease oxidative stress in animal models. Moreover, phytoestrogens such as genistein, present in soya, can mimic some of the beneficial effects of estrogens and are devoid of significant side effects, such as cancer. In this study, we have performed a controlled lifelong study with male OF1 mice that consumed either a soya-free diet or a soya-rich diet. We show that, although we found an increase in the expression and activity of antioxidant enzymes in soya-consuming mice, it did not increase lifespan. We reasoned that the soya diet could not increase lifespan in a very healthy population, but perhaps it could extend health span in stressed animals such as type 2 diabetic Goto Kakizaki (GK) rats. Indeed, this was the case: we found that male GK rats consuming a soya-rich diet developed the disease at a lower rate and, therefore, lived longer than soya-free diet-consuming rats.

Early Exposure is Necessary for the Lifespan Extension Effects of Cocoa in C. elegans

Background

We previously showed that cocoa, a rich source of polyphenols improved the age-associated health and extended the lifespan in C. elegans when supplemented starting from L1 stage.

Aim

In this study, we aimed to find out the effects of timing of cocoa exposure on longevity improving effects and the mechanisms and pathways involved in lifespan extension in C. elegans.

Methods

The standard E. coli OP50 diet of wild type C. elegans was supplemented with cocoa powder starting from different larval stages (L1, L2, L3, and L4) till the death, from L1 to adult day 1 and from adult day 1 till the death. For mechanistic studies, different mutant strains of C. elegans were supplemented with cocoa starting from L1 stage till the death. Survival curves were plotted, and mean lifespan was reported.

Results

Cocoa exposure starting from L1 stage till the death and till adult day 1 significantly extended the lifespan of worms. However, cocoa supplementation at other larval stages as well as at adulthood could not extend the lifespan, instead the lifespan was significantly reduced. Cocoa could not extend the lifespan of daf-16, daf-2, sir-2.1, and clk-1 mutants.

Conclusion

Early-start supplementation is essential for cocoa-mediated lifespan extension which is dependent on insulin/IGF-1 signaling pathway and mitochondrial respiration.

Histopathological, histochemical and biochemical postmortem changes in induced fatal hypothermia in rats

Reaching a postmortem diagnosis of hypothermia is challenging in forensic practice. Therefore, this study was conducted to detect the histopathological, histochemical and biochemical changes that occur in adult albino rats following exposure to induced fatal hypothermia. Twenty-four adult albino rats were divided into the negative control, moderate hypothermia, severe hypothermia and hypoxia groups. Rats in the control group were euthanized when those in the moderate hypothermic group died. Blood samples were collected via heart puncture, and the cerebrum, heart, suprarenal gland, kidney, liver and skeletal muscle were removed to investigate the biochemical, histochemical and histopathological changes. Postmortem assessment depicted significant changes in lipid peroxidation, represented by increased malondialdehyde levels in the studied organs of the rats in hypothermic and hypoxia groups. Histopathological examination of the rats’ organs revealed degeneration and necrosis in the hypothermia and hypoxia groups. Sections taken from the severe hypothermic rats revealed a loss of normal cardiac tissue architecture, necrotic changes in the pyramidal cells in the cerebral cortex, and massive necrosis, mainly in the tubules of the renal cortex and medulla. These findings suggest that histological changes might be used as biochemical markers for postmortem diagnosing of fatal hypothermia, particularly in severe hypothermic conditions.

Key points

Death by hypothermia is a serious public health problem worldwide.

Confirming a diagnosis and determining the cause of death in cases of hypothermia are among the most difficult practices in forensic medicine.

Death by hypothermia might be associated with structural abnormalities in various organs.

Studies using different tissue staining techniques will enable an overall illustration of the role of histopathological changes in body organs as indicators of hypothermia.

Beneficial and Detrimental Effects of Reactive Oxygen Species on Lifespan: A Comprehensive Review of Comparative and Experimental Studies

Aging is the greatest risk factor for a multitude of diseases including cardiovascular disease, neurodegeneration and cancer. Despite decades of research dedicated to understanding aging, the mechanisms underlying the aging process remain incompletely understood. The widely-accepted free radical theory of aging (FRTA) proposes that the accumulation of oxidative damage caused by reactive oxygen species (ROS) is one of the primary causes of aging. To define the relationship between ROS and aging, there have been two main approaches: comparative studies that measure outcomes related to ROS across species with different lifespans, and experimental studies that modulate ROS levels within a single species using either a genetic or pharmacologic approach. Comparative studies have shown that levels of ROS and oxidative damage are inversely correlated with lifespan. While these studies in general support the FRTA, this type of experiment can only demonstrate correlation, not causation. Experimental studies involving the manipulation of ROS levels in model organisms have generally shown that interventions that increase ROS tend to decrease lifespan, while interventions that decrease ROS tend to increase lifespan. However, there are also multiple examples in which the opposite is observed: increasing ROS levels results in extended longevity, and decreasing ROS levels results in shortened lifespan. While these studies contradict the predictions of the FRTA, these experiments have been performed in a very limited number of species, all of which have a relatively short lifespan. Overall, the data suggest that the relationship between ROS and lifespan is complex, and that ROS can have both beneficial or detrimental effects on longevity depending on the species and conditions. Accordingly, the relationship between ROS and aging is difficult to generalize across the tree of life.

The goal of geroscience is life extension

Although numerous drugs seemingly extend healthspan in mice, only a few extend lifespan in mice and only one does it consistently. Some of them, alone or in combination, can be used in humans, without further clinical trials.

Genes affecting the extension of chronological lifespan in Schizosaccharomyces pombe (fission yeast)

So far, more than 70 genes involved in the chronological lifespan (CLS) of Schizosaccharomyces pombe (fission yeast) have been reported. In this mini‐review, we arrange and summarize these genes based on the reported genetic interactions between them and the physical interactions between their products. We describe the signal transduction pathways that affect CLS in S. pombe: target of rapamycin complex 1, cAMP‐dependent protein kinase, Sty1, and Pmk1 pathways have important functions in the regulation of CLS extension. Furthermore, the Php transcription complex, Ecl1 family proteins, cyclin Clg1, and the cyclin‐dependent kinase Pef1 are important for the regulation of CLS extension in S. pombe. Most of the known genes involved in CLS extension are related to these pathways and genes. In this review, we focus on the individual genes regulating CLS extension in S. pombe and discuss the interactions among them.

The role of oxidative stress in postcopulatory selection

Two decades ago, von Schantz et al. (von Schantz T, Bensch S, Grahn M, Hasselquist D, Wittzell H. 1999 Good genes, oxidative stress and condition-dependent sexual signals. Proc. R. Soc. B 266, 1-12. (doi:10.1098/rspb.1999.0597)) united oxidative stress (OS) biology with sexual selection and life-history theory. This set the scene for analysis of how evolutionary trade-offs may be mediated by the increase in reactive molecules resulting from metabolic processes at reproduction. Despite 30 years of research on OS effects on infertility in humans, one research area that has been left behind in this integration of evolution and OS biology is postcopulatory sexual selection-this integration is long overdue. We review the basic mechanisms in OS biology, why mitochondria are the primary source of ROS and ATP production during oxidative metabolism, and why sperm, and its performance, is uniquely susceptible to OS. We also review how postcopulatory processes select for antioxidation in seminal fluids to counter OS and the implications of the net outcome of these processes on sperm damage, sperm storage, and female and oocyte manipulation of sperm metabolism and repair of DNA to enhance offspring fitness. This article is part of the theme issue 'Fifty years of sperm competition'.

Oxidative Stress and Reproductive Function in the Aging Male

With the delay of parenthood becoming more common, the age at which men father children is on the rise. While the effects of advanced maternal age have been well documented, only recently have studies started to focus on the impact of advanced paternal age (APA) in the context of male reproduction. As men age, the antioxidant defense system gradually becomes less efficient and elevated levels of reactive oxygen species (ROS) accumulate in spermatozoa; this can impair their functional and structural integrity. In this review, we present an overview of how oxidative stress is implicated in male reproductive aging by providing a summary of the sources and roles of ROS, the theories of aging, and the current animal and human studies that demonstrate the impacts of APA on the male germ line, the health of progeny and fertility, and how treatment with antioxidants may reverse these effects.

Perspective: Methionine Restriction-Induced Longevity-A Possible Role for Inhibiting the Synthesis of Bacterial Quorum Sensing Molecules

Methionine restriction (MR) extends lifespans in multiple species through mechanisms that include enhanced oxidative stress resistance and inhibition of insulin/insulin-like growth factor I (IGF-I) signaling. Methionine and S-adenosylmethionine (SAM) are the essential precursors of bacterial quorum sensing (QS) molecules, and therefore, MR might also affect bacterial communication to prevent enteric bacterial infection as well as chronic inflammation, which contributes to lifespan prolongation. Here, we discuss the influence of MR on oxidative stress resistance and inhibition of insulin/IGF-I cell signaling and further propose a potential mechanism involving bacterial QS inhibition for lifespan extension. Unraveling the connection between MR and inhibition of QS provides new strategies for combating infectious diseases, resulting in enriched understanding of MR-induced lifespan extension.

Dietary antioxidants attenuate the endocrine stress response during long-duration flight of a migratory bird

Glucocorticoids (GCs) are metabolic hormones that promote catabolic processes, which release stored energy and support high metabolic demands such as during prolonged flights of migrating birds. Dietary antioxidants (e.g. anthocyanins) support metabolism by quenching excess reactive oxygen species produced during aerobic metabolism and also by activating specific metabolic pathways. For example, similar to GCs' function, anthocyanins promote the release of stored energy, although the extent of complementarity between GCs and dietary antioxidants is not well known. If anthocyanins complement GCs functions, birds consuming anthocyanin-rich food can be expected to limit the secretion of GCs when coping with a metabolically challenging activity, avoiding the exposure to potential hormonal detrimental effects. We tested this hypothesis in European starlings (Sturnus vulgaris) flying in a wind tunnel. We compared levels of corticosterone, the main avian GC, immediately after a sustained flight and at rest for birds that were fed diets with or without an anthocyanin supplement. As predicted, we found (i) higher corticosterone after flight than at rest in both diet groups and (ii) anthocyanin-supplemented birds had less elevated corticosterone after flight than unsupplemented control birds. This provides novel evidence that dietary antioxidants attenuate the activation of the HPA axis (i.e. increased secretion of corticosterone) during long-duration flight.

Effects of temperature changes on life parameters, oxidative stress, and antioxidant defense system in the monogonont marine rotifer Brachionus plicatilis

Global warming is a big concern for all organisms and many efforts have been made to reveal the potential effects of temperature elevation on aquatic organisms. However, limited studies on molecular mechanistic approaches on physiological effects due to temperature changes are available. Here, we investigated the effects of temperature changes on life parameters (e.g., population growth [total number of rotifers], and lifespan), oxidative stress levels and antioxidant activities (e.g., glutathione S-transferase [GST], catalase [CAT], superoxide dismutase [SOD]) with expression levels in the monogonont marine rotifer Brachionus plicatilis. The changes in temperatures led to significant reduction (P < 0.05) in lifespan, possibly due to significant decrease (P < 0.05) in antioxidant activities, reducing the potential to cope with significant elevation in the temperature-induced oxidative stress in B. plicatilis. To further assess the actual induction and clearance of reactive oxygen species (ROS), N-acetyl-L-cysteine was used to examine whether the temperature-induced oxidative stress could be successfully scavenged. Furthermore, expression patterns of the antioxidant-related genes (GSTs, SODs, and CATs) were down- or upregulated (P < 0.05) in response to different temperatures in B. plicatilis. Overall, these findings indicate that ROS-mediated oxidative stress led to cellular damage and antioxidant defense system, resulting in deleterious effects on life parameters in rotifer.

Effect of temperature on antioxidant defense and innate immunity in Brandt's voles

Ambient temperature is an important factor influencing many physiological processes, including antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatment in Brandt's voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32 °C, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature increased gross energy intake (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxygen species (ROS) levels, increased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (T-AOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4 °C group in contrast to the 23 °C group, whereas spleen mass and white blood cells were unaffected by temperature treatment. The levels of testosterone, but not corticosterone, were influenced by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and T-AOC activity in any detected tissues. Overall, these results showed that temperature had different influences on oxidative stress, antioxidant enzymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of antioxidant defense might be an important mechanism for voles to survive highly variable environmental temperatures.

The relationship of mammal survivorship and body mass modeled by metabolic and vitality theories

A model describes the relationship between mammal body mass and survivorship by combining replicative senescence theory postulating a cellular basis of aging, metabolic theory relating metabolism to body mass, and vitality theory relating survival to vitality loss and extrinsic mortality. In the combined framework, intrinsic mortality results from replicative senescence of the hematopoietic stem cells and extrinsic mortality results from environmental challenges. Because the model expresses the intrinsic and extrinsic rates with different powers of body mass, across the spectrum of mammals, survivorship changes from Type I to Type II curve shapes with decreasing body mass. Fitting the model to body mass and maximum lifespan data of 494 nonvolant mammals yields allometric relationships of body mass to the vitality parameters, from which full survivorship profiles were generated from body mass alone. Because maximum lifespan data is predominantly derived from captive populations, the generated survivorship curves were dominated by intrinsic mortality. Comparison of the mass-derived and observed survivorship curves provides insights into how specific populations deviate from the aggregate of populations observed under captivity.

Beyond ROS clearance: Peroxiredoxins in stress signaling and aging

Antioxidants were long predicted to have lifespan-promoting effects, but in general this prediction has not been well supported. While some antioxidants do seem to have a clear effect on longevity, this may not be primarily as a result of their role in the removal of reactive oxygen species, but rather mediated by other mechanisms such as the modulation of intracellular signaling. In this review we discuss peroxiredoxins, a class of proteinaceous antioxidants with redox signaling and chaperone functions, and their involvement in regulating longevity and stress resistance. Peroxiredoxins have a clear role in the regulation of lifespan and survival of many model organisms, including the mouse, Caenorhabditis elegans and Drosophila melanogaster. Recent research on peroxiredoxins - in these models and beyond - has revealed surprising new insights regarding the interplay between peroxiredoxins and longevity signaling, which will be discussed here in detail. As redox signaling is emerging as a potentially important player in the regulation of longevity and aging, increased knowledge of these fascinating antioxidants and their mode(s) of action is paramount.

Factors extending the chronological lifespan of yeast: Ecl1 family genes

Ecl1 family genes are conserved among yeast, in which their overexpression extends chronological lifespan. Ecl1 family genes were first identified in the fission yeast Schizosaccharomyces pombe; at the time, they were considered noncoding RNA owing to their short coding sequence of fewer than 300 base pairs. Schizosaccharomyces pombe carries three Ecl1 family genes, ecl1+, ecl2+ and ecl3+, whereas Saccharomyces cerevisiae has one, ECL1. Their overexpression extends chronological lifespan, increases oxidative stress resistance and induces sexual development in fission yeast. A recent study indicated that Ecl1 family genes play a significant role in responding to environmental zinc or sulfur depletion. In this review, we focus on Ecl1 family genes in fission yeast and describe the relationship between nutritional depletion and cellular output, as the latter depends on Ecl1 family genes. Furthermore, we present the roles and functions of Ecl1 family genes characterized to date.

Finding Ponce de Leon's Pill: Challenges in Screening for Anti-Aging Molecules

Aging is characterized by the progressive accumulation of degenerative changes, culminating in impaired function and increased probability of death. It is the major risk factor for many human pathologies - including cancer, type 2 diabetes, and cardiovascular and neurodegenerative diseases - and consequently exerts an enormous social and economic toll. The major goal of aging research is to develop interventions that can delay the onset of multiple age-related diseases and prolong healthy lifespan (healthspan). The observation that enhanced longevity and health can be achieved in model organisms by dietary restriction or simple genetic manipulations has prompted the hunt for chemical compounds that can increase lifespan. Most of the pathways that modulate the rate of aging in mammals have homologs in yeast, flies, and worms, suggesting that initial screening to identify such pharmacological interventions may be possible using invertebrate models. In recent years, several compounds have been identified that can extend lifespan in invertebrates, and even in rodents. Here, we summarize the strategies employed, and the progress made, in identifying compounds capable of extending lifespan in organisms ranging from invertebrates to mice and discuss the formidable challenges in translating this work to human therapies.

Type 5 adenylyl cyclase disruption leads to enhanced exercise performance

The most important physiological mechanism mediating enhanced exercise performance is increased sympathetic, beta adrenergic receptor (β-AR), and adenylyl cyclase (AC) activity. This is the first report of decreased AC activity mediating increased exercise performance. We demonstrated that AC5 disruption, that is, knock out (KO) mice, a longevity model, increases exercise performance. Importantly for its relation to longevity, exercise was also improved in old AC5 KO. The mechanism resided in skeletal muscle rather than in the heart, as confirmed by cardiac- and skeletal muscle-specific AC5 KO's, where exercise performance was no longer improved by the cardiac-specific AC5 KO, but was by the skeletal muscle-specific AC5 KO, and there was no difference in cardiac output during exercise in AC5 KO vs. WT. Mitochondrial biogenesis was a major mechanism mediating the enhanced exercise. SIRT1, FoxO3a, MEK, and the anti-oxidant, MnSOD were upregulated in AC5 KO mice. The improved exercise in the AC5 KO was blocked with either a SIRT1 inhibitor, MEK inhibitor, or by mating the AC5 KO with MnSOD hetero KO mice, confirming the role of SIRT1, MEK, and oxidative stress mechanisms. The Caenorhabditis elegans worm AC5 ortholog, acy-3 by RNAi, also improved fitness, mitochondrial function, antioxidant defense, and lifespan, attesting to the evolutionary conservation of this pathway. Thus, decreasing sympathetic signaling through loss of AC5 is not only a mechanism to improve exercise performance, but is also a mechanism to improve healthful aging, as exercise also protects against diabetes, obesity, and cardiovascular disease, which all limit healthful aging.

Comparative cellular biogerontology: Where do we stand?

Due to the extreme variation in life spans among species, using a comparative approach to address fundamental questions about the aging process has much to offer. For example, maximum life span can vary by as much as several orders of magnitude among taxa. In recent years, using primary cell lines cultured from species with disparate life spans and aging rates has gained considerable momentum as a means to dissect the mechanisms underlying the variation in aging rates among animals. In this review, we reiterate the strengths of comparative cellular biogerontology, as well as provide a survey of the current state of the field. By and large this work sprang from early studies using cell lines derived from long-lived mutant mice. Specifically, they suggested that an enhanced resistance to cellular stress was strongly associated with increased longevity of select laboratory models. Since then, we and others have shown that the degree of stress resistance and species longevity is also correlated among cell lines derived from free-living populations of both mammals and birds, and more recent studies have begun to reveal the biochemical and physiological underpinnings to these differences. The continued study of cultured cell lines from vertebrates with disparate life spans is likely to provide considerable insight toward unifying mechanisms of longevity assurance.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

Oxidative stress in aging human skin

Oxidative stress in skin plays a major role in the aging process. This is true for intrinsic aging and even more for extrinsic aging. Although the results are quite different in dermis and epidermis, extrinsic aging is driven to a large extent by oxidative stress caused by UV irradiation. In this review the overall effects of oxidative stress are discussed as well as the sources of ROS including the mitochondrial ETC, peroxisomal and ER localized proteins, the Fenton reaction, and such enzymes as cyclooxygenases, lipoxygenases, xanthine oxidases, and NADPH oxidases. Furthermore, the defense mechanisms against oxidative stress ranging from enzymes like superoxide dismutases, catalases, peroxiredoxins, and GSH peroxidases to organic compounds such as L-ascorbate, α-tocopherol, beta-carotene, uric acid, CoQ10, and glutathione are described in more detail. In addition the oxidative stress induced modifications caused to proteins, lipids and DNA are discussed. Finally age-related changes of the skin are also a topic of this review. They include a disruption of the epidermal calcium gradient in old skin with an accompanying change in the composition of the cornified envelope. This modified cornified envelope also leads to an altered anti-oxidative capacity and a reduced barrier function of the epidermis.

An oxidative fluctuation hypothesis of aging generated by imaging H₂O₂ levels in live Caenorhabditis elegans with altered lifespans

Reactive oxygen species (ROS) are important factors mediating aging according to the free radical theory of aging. Few studies have systematically measured ROS levels in relationship to aging, partly due to the lack of tools for detection of specific ROS in live animals. By using the H₂O₂-specific fluorescence probe Peroxy Orange 1, we assayed the H₂O₂ levels of live Caenorhabditis elegans with 41 aging-related genes being individually knocked down by RNAi. Knockdown of 14 genes extends the lifespan but increases H₂O₂ level or shortens the lifespan but decreases H₂O₂ level, contradicting the free radical theory of aging. Strikingly, a significant inverse correlation between lifespan and the normalized standard deviation of H₂O₂ levels was observed (p < 0.0001). Such inverse correlation was also observed in worms cultured under heat shock conditions. An oxidative fluctuation hypothesis of aging is thus proposed and suggests that the ability of animals to homeostatically maintain the ROS levels within a narrow range is more important for lifespan extension than just minimizing the ROS levels though the latter still being crucial.

Effects of nutritional components on aging

Nutrients including carbohydrates, proteins, lipids, vitamins, and minerals regulate various physiological processes and are essential for the survival of organisms. Reduced overall caloric intake delays aging in various organisms. However, the role of each nutritional component in the regulation of lifespan is not well established. In this review, we describe recent studies focused on the regulatory role of each type of nutrient in aging. Moreover, we will discuss how the amount or composition of each nutritional component may influence longevity or health in humans.

Nordihydroguaiaretic Acid Extends the Lifespan of Drosophila and Mice, Increases Mortality-Related Tumors and Hemorrhagic Diathesis, and Alters Energy Homeostasis in Mice

Mesonordihydroguaiaretic acid (NDGA) extends murine lifespan. The studies reported here describe its dose dependence, effects on body weight, toxicity-related clinical chemistries, and mortality-related pathologies. In flies, we characterized its effects on lifespan, food consumption, body weight, and locomotion. B6C3F1 mice were fed AIN-93M diet supplemented with 1.5, 2.5, 3.5, or 4.5g NDGA/kg diet (1.59, 2.65, 3.71 and 4.77mg/kg body weight/day) beginning at 12 months of age. Only the 3.5mg/kg diet produced a highly significant increase in lifespan, as judged by either the Mantel–Cox log-rank test (p = .008) or the Gehan–Breslow–Wilcoxon test (p = .009). NDGA did not alter food intake, but dose-responsively reduced weight, suggesting it decreased the absorption or increased the utilization of calories. NDGA significantly increased the incidence of liver, lung, and thymus tumors, and peritoneal hemorrhagic diathesis found at necropsy. However, clinical chemistries found little evidence for overt toxicity. While NDGA was not overtly toxic at its therapeutic dosage, its association with severe end of life pathologies does not support the idea that NDGA consumption will increase human lifespan or health-span. The less toxic derivatives of NDGA which are under development should be explored as anti-aging therapeutics.

L-carnitine prevents progression of non-alcoholic steatohepatitis in a mouse model with upregulation of mitochondrial pathway

Non-alcoholic steatohepatitis (NASH) is a severe form of non-alcoholic fatty liver disease characterized by lobular inflammation, hepatocellular ballooning, and fibrosis with an inherent risk for progression to cirrhosis and hepatocellular carcinoma (HCC). Mitochondrial dysfunction appears to play a role in the progression from simple steatosis to NASH. L-carnitine (L-b-hydroxy-g-N-trimethylaminobutyric acid), an essential nutrient that converts fat into energy in mitochondria, has been shown to ameliorate liver damage. The aim of the present study was to explore the preventive and therapeutic effect of L-carnitine in NASH model mice. Eight-week-old male STAM mice, a NASH-cirrhosis-hepatocarcinogenic model, were divided into 3 experimental groups and fed as follows: 1) high-fat diet (HFD) (control group); 2) HFD mixed with 0.28% L-carnitine (L-carnitine group); and 3) HFD mixed with 0.01% α-tocopherol (α-tocopherol group). After 4 or 8 weeks, mice were sacrificed. Blood samples and livers were collected, and hepatic tumors were counted and measured. Livers were subjected to histological study, immunohistochemical staining of 4-hydroxynonenal and ferritin, determination of 8-OHdG levels, mRNA and protein expressions for multiple genes, and metabolomic analysis. The intestinal microbiome was also analyzed. L-carnitine increased hepatic expression of genes related to long-chain fatty acid transport, mitochondrial β-oxidation, and antioxidant enzymes following suppression of hepatic oxidative stress markers and inflammatory cytokines in NASH, and mice treated with L-carnitine developed fewer liver tumors. Although α-tocopherol resulted in NASH improvement in the same manner as L-carnitine, it increased periodontitis-related microbiotic changes and hepatic iron transport-related gene expression and led to less effective for anti-hepatocarcinogenesis.

Conclusion

L-carnitine prevents progression of non-alcoholic steatohepatitis in a mouse model by upregulating the mitochondrial β-oxidation and redox system.

Oxidative stress and its downstream signaling in aging eyes

BACKGROUND

Oxidative stress (OS) and its biomarkers are the biochemical end point of the imbalance between reactive oxygen species (ROS) production and the ability of the antioxidant (AOX) biological systems to fight against oxidative injury.

OBJECTIVE

We reviewed the role of OS and its downstream signaling in aging eyes.

METHODS

A search of the literature and current knowledge on the physiological and pathological mechanisms of OS were revisited in relation to the eyes and the aging process. Most prevalent ocular diseases have been analyzed herein in relation to OS and nutraceutic supplements, such as dry-eye disorders, glaucoma, age-related macular degeneration, and diabetic retinopathy.

RESULTS

Clinical, biochemical, and molecular data from anterior and posterior eye segment diseases point to OS as the common pathogenic mechanism in the majority of these ocular disorders, many of which are pathologies causing visual impairment, blindness, and subsequent loss of life quality. Studies with nutraceutic supplements in aging eye-related pathologies have also been reviewed.

CONCLUSION

OS, nutritional status, and nutraceutic supplements have to be considered within the standards of care of older ophthalmologic patients. OS biomarkers and surrogate end points may help in managing the aging population with ocular diseases.

Lifespan effects of simple and complex nutraceutical combinations fed isocalorically to mice

Present data suggest that the consumption of individual dietary supplements does not enhance the health or longevity of healthy rodents or humans. It might be argued that more complex combinations of such agents might extend lifespan or health-span by more closely mimicking the complexity of micronutrients in fruits and vegetables, which appear to extend health-span and longevity. To test this hypothesis we treated long-lived, male, F1 mice with published and commercial combinations of dietary supplements and natural product extracts, and determined their effects on lifespan and health-span. Nutraceutical, vitamin or mineral combinations reported to extend the lifespan or health-span of healthy or enfeebled rodents were tested, as were combinations of botanicals and nutraceuticals implicated in enhanced longevity by a longitudinal study of human aging. A cross-section of commercial nutraceutical combinations sold as potential health enhancers also were tested, including Bone Restore®, Juvenon®, Life Extension Mix®, Ortho Core®, Ortho Mind®, Super K w k2®, and Ultra K2®. A more complex mixture of vitamins, minerals, botanical extracts and other nutraceuticals was compounded and tested. No significant increase in murine lifespan was found for any supplement mixture. Our diverse supplement mixture significantly decreased lifespan. Thus, our results do not support the hypothesis that simple or complex combinations of nutraceuticals, including antioxidants, are effective in delaying the onset or progress of the major causes of death in mice. The results are consistent with epidemiological studies suggesting that dietary supplements are not beneficial and even may be harmful for otherwise healthy individuals.

Effect of antioxidants supplementation on aging and longevity

If aging is due to or contributed by free radical reactions, as postulated by the free radical theory of aging, lifespan of organisms should be extended by administration of exogenous antioxidants. This paper reviews data on model organisms concerning the effects of exogenous antioxidants (antioxidant vitamins, lipoic acid, coenzyme Q, melatonin, resveratrol, curcumin, other polyphenols, and synthetic antioxidants including antioxidant nanoparticles) on the lifespan of model organisms. Mechanisms of effects of antioxidants, often due to indirect antioxidant action or to action not related to the antioxidant properties of the compounds administered, are discussed. The legitimacy of antioxidant supplementation in human is considered.

Coenzyme Q10 prevents accelerated cardiac aging in a rat model of poor maternal nutrition and accelerated postnatal growth

Studies in human and animals have demonstrated that nutritionally induced low birth-weight followed by rapid postnatal growth increases the risk of metabolic syndrome and cardiovascular disease. Although the mechanisms underlying such nutritional programming are not clearly defined, increased oxidative-stress leading to accelerated cellular aging has been proposed to play an important role. Using an established rodent model of low birth-weight and catch-up growth, we show here that post-weaning dietary supplementation with coenzyme Q10, a key component of the electron transport chain and a potent antioxidant rescued many of the detrimental effects of nutritional programming on cardiac aging. This included a reduction in nitrosative and oxidative-stress, telomere shortening, DNA damage, cellular senescence and apoptosis. These findings demonstrate the potential for postnatal antioxidant intervention to reverse deleterious phenotypes of developmental programming and therefore provide insight into a potential translatable therapy to prevent cardiovascular disease in at risk humans.

Deleterious consequences of antioxidant supplementation on lifespan in a wild-derived mammal

While oxidative damage owing to reactive oxygen species (ROS) often increases with advancing age and is associated with many age-related diseases, its causative role in ageing is controversial. In particular, studies that have attempted to modulate ROS-induced damage, either upwards or downwards, using antioxidant or genetic approaches, generally do not show a predictable effect on lifespan. Here, we investigated whether dietary supplementation with either vitamin E (α-tocopherol) or vitamin C (ascorbic acid) affected oxidative damage and lifespan in short-tailed field voles, Microtus agrestis. We predicted that antioxidant supplementation would reduce ROS-induced oxidative damage and increase lifespan relative to unsupplemented controls. Antioxidant supplementation for nine months reduced hepatic lipid peroxidation, but DNA oxidative damage to hepatocytes and lymphocytes was unaffected. Surprisingly, antioxidant supplementation significantly shortened lifespan in voles maintained under both cold (7 ± 2°C) and warm (22 ± 2°C) conditions. These data further question the predictions of free-radical theory of ageing and critically, given our previous research in mice, indicate that similar levels of antioxidants can induce widely different interspecific effects on lifespan.