Impact of aging and life-long calorie restriction on expression of apoptosis-related genes in male F344 rat liver

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

Effects of apoptosis on liver aging

As an irreversible and perennial process, aging is accompanied by functional and morphological declines in organs. Generally, aging liver exhibits a decline in volume and hepatic blood flow. Even with a preeminent regenerative capacity to restore its functions after liver cell loss, its biosynthesis and metabolism abilities decline, and these are difficult to restore to previous standards. Apoptosis is a programmed death process via intrinsic and extrinsic pathways, in which Bcl-2 family proteins and apoptosis-related genes, such as p21 and p53, are involved. Apoptosis inflicts both favorable and adverse influences on liver aging. Apoptosis eliminates transformed abnormal cells but promotes age-related liver diseases, such as nonalcoholic fatty liver disease, liver fibrosis, cirrhosis, and liver cancer. We summarize the roles of apoptosis in liver aging and age-related liver diseases.

Apoptosis in the aging liver

Various changes in the liver during aging can reduce hepatic function and promote liver injury. Aging is associated with high morbidity and a poor prognosis in patients with various liver diseases, including nonalcoholic fatty liver disease, hepatitis C and liver cancer, as well as with surgeries such as partial hepatectomy and liver transplantation. In addition, apoptosis increases with liver aging. Because apoptosis is involved in regeneration, fibrosis and cancer prevention during liver aging, and restoration of the appropriate level of apoptosis can alleviate the adverse effects of liver aging, it is important to understand the mechanisms underlying this process. Herein, we elaborate on the causes of apoptosis during liver aging, with a focus on oxidative stress, genomic instability, lipotoxicity, endoplasmic reticulum stress, dysregulation of nutrient sensing, and liver stem/progenitor cell activity.

Neuroprotective effects of phytosterol esters against high cholesterol-induced cognitive deficits in aged rat

Accumulating epidemiological and experimental studies have confirmed that a high-cholesterol diet is detrimental to cognitive performance in animal models.

Milk-soluble formula increases food intake and reduces Il6 expression in elderly rat hypothalami

Malnutrition in the elderly is accompanied by several metabolic dysfunctions, especially alterations in energy homeostasis regulation and a loss of insulin responsiveness. Nutritional recommendations aim to enrich food with high protein and energy supplements, and protein composition and lipid quality have been widely studied. Despite the numerous studies that have examined attempts to overcome malnutrition in the elderly through such nutritional supplementation, it is still necessary to study the effects of a combination of protein, lipids, and vitamin D (VitD). This can be done in animal models of elderly malnutrition. In the present study, we investigated the effects of several diet formulae on insulin responsiveness, inflammation, and the hypothalamic expression of key genes that are involved in energy homeostasis control. To mimic elderly malnutrition in humans, elderly Wistar rats were food restricted (R, -50%) for 12 weeks and then refed for 4 weeks with one of four different isocaloric diets: a control diet; a diet where milk soluble protein (MSP) replaced casein; a blend of milk fat, rapeseed, and DHA (MRD); or a full formula (FF) diet that combined MSP and a blend of MRD (FF). All of the refeeding diets contained VitD. We concluded that: (i) food restriction led to the upregulation of insulin receptor in liver and adipose tissue accompanied by increased Tnfα in the hypothalamus; (ii) in all of the refed groups, refeeding led to similar body weight gain during the refeeding period; and (iii) refeeding with MSP and MRD diets induced higher food intake on the fourth week of refeeding, and this increase was associated with reduced hypothalamic interleukin 6 expression.

A comparative study on the effect of high cholesterol diet on the hippocampal CA1 area of adult and aged rats

Dementia is one of the most important problems nowadays. Aging is associated with learning and memory impairments. Diet rich in cholesterol has been shown to be detrimental to cognitive performance. This work was carried out to compare the effect of high cholesterol diet on the hippocampus of adult and aged male albino rats. Twenty adult and twenty aged male rats were used in this study. According to age, the rats were randomly subdivided into balanced and high cholesterol diet fed groups. The diet was 15 g/rat/day for adult rats and 20 g/rat/day for aged rats for eight weeks. Serial coronal sections of hippocampus and blood samples were taken from each rat. For diet effect evaluation, Clinical, biochemical, histological, immunohistochemical, and morphometric assessments were done. In compare to a balanced diet fed rat, examination of Cornu Ammonis 1 (CA 1) area in the hippocampus of the high cholesterol diet adult rats showed degeneration, a significant decrease of the pyramidal cells, attenuation and/or thickening of small blood vessels, apparent increase of astrocytes and apparent decrease of Nissl's granules content. Moreover, the high cholesterol diet aged rats showed aggravation of senility changes of the hippocampus together with Alzheimer like pathological changes. In conclusion, the high cholesterol diet has a significant detrimental effect on the hippocampus and aging might pronounce this effect. So, we should direct our attention to limit cholesterol intake in our food to maintain a healthy life style for a successful aging.

Bariatric surgery and diet-induced long-term caloric restriction protect subcutaneous adipose-derived stromal/progenitor cells and prolong their life span in formerly obese humans

A key effect of prolonged reducing diets and bariatric surgeries in formerly obese people is long-term caloric restriction (CR). The analysis of the impact of these interventions on specific tissues will contribute to a better understanding of their mechanisms of action. The physiological functions of subcutaneous white adipose tissues are mainly fulfilled by adipocytes arising out of adipose-derived stromal/progenitor cells (ASCs), which are crucial for adipose tissue homeostasis. In the present study we analyzed ASC from age-matched long-term calorically restricted formerly obese (CRD), obese (OD) and normal weight donors (NWDs). We demonstrate that ASC derived from CRD has a significant longer replicative lifespan than ASC isolated from OD and NWD. This correlated with strongly reduced DNA-damage and improved survival of the CRD ASC, both are hallmarks of CR. The adipogenic capacity was significantly lower in ASC derived from CRD than that from OD, as shown by reduced expression of the adipogenic key regulator PPARγ2 and the differentiation marker FABP4. The adipogenic capacity of ASCs from CRD and NWD differed only slightly. In conclusion, we provide evidence that bariatric surgery and diet-induced long-term CR substantially reprogram ASCs in formerly obese humans, comprising reduced DNA-damage, improved viability, extended replicative lifespan and reduced adipogenic differentiation potential.

Dietary fat and aging modulate apoptotic signaling in liver of calorie-restricted mice

Imbalance between proliferation and cell death accounts for several age-linked diseases. Aging, calorie restriction (CR), and fat source are all factors that may influence apoptotic signaling in liver, an organ that plays a central metabolic role in the organism. Here, we have studied the combined effect of these factors on a number of apoptosis regulators and effectors. For this purpose, animals were fed diets containing different fat sources (lard, soybean oil, or fish oil) under CR for 6 or 18 months. An age-linked increase in the mitochondrial apoptotic pathway was detected with CR, including a decrease in Bcl-2/Bax ratio, an enhanced release of cytochrome c to the cytosol and higher caspase-9 activity. However, these changes were not fully transmitted to the effectors apoptosis-inducing factor and caspase-3. CR (which abated aging-related inflammatory responses) and dietary fat altered the activities of caspases-8, -9, and -3. Apoptotic index (DNA fragmentation) and mean nuclear area were increased in aged animals with the exception of calorie-restricted mice fed a lard-based fat source. These results suggest possible protective changes in hepatic homeostasis with aging in the calorie-restricted lard group.

Caloric restriction and aging stem cells: the stick and the carrot?

Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.

Caloric restriction shortens lifespan through an increase in lipid peroxidation, inflammation and apoptosis in the G93A mouse, an animal model of ALS

Caloric restriction (CR) extends lifespan through a reduction in oxidative stress, delays the onset of morbidity and prolongs lifespan. We previously reported that long-term CR hastened clinical onset, disease progression and shortened lifespan, while transiently improving motor performance in G93A mice, a model of amyotrophic lateral sclerosis (ALS) that shows increased free radical production. To investigate the long-term CR-induced pathology in G93A mice, we assessed the mitochondrial bioenergetic efficiency and oxidative capacity (CS--citrate synthase content and activity, cytochrome c oxidase--COX activity and protein content of COX subunit-I and IV and UCP3-uncoupling protein 3), oxidative damage (MDA--malondialdehyde and PC--protein carbonyls), antioxidant enzyme capacity (Mn-SOD, Cu/Zn-SOD and catalase), inflammation (TNF-alpha), stress response (Hsp70) and markers of apoptosis (Bax, Bcl-2, caspase 9, cleaved caspase 9) in their skeletal muscle. At age 40 days, G93A mice were divided into two groups: Ad libitum (AL; n = 14; 7 females) or CR (n = 13; 6 females), with a diet equal to 60% of AL. COX/CS enzyme activity was lower in CR vs. AL male quadriceps (35%), despite a 2.3-fold higher COX-IV/CS protein content. UCP3 was higher in CR vs. AL females only. MnSOD and Cu/Zn-SOD were higher in CR vs. AL mice and CR vs. AL females. MDA was higher (83%) in CR vs. AL red gastrocnemius. Conversely, PC was lower in CR vs. AL red (62%) and white (30%) gastrocnemius. TNF-alpha was higher (52%) in CR vs. AL mice and Hsp70 was lower (62%) in CR vs. AL quadriceps. Bax was higher in CR vs. AL mice (41%) and CR vs. AL females (52%). Catalase, Bcl-2 and caspases did not differ. We conclude that CR increases lipid peroxidation, inflammation and apoptosis, while decreasing mitochondrial bioenergetic efficiency, protein oxidation and stress response in G93A mice.

Determining the influence of telomere dysfunction and DNA damage on stem and progenitor cell aging: what markers can we use?

The decline in organ maintenance and function is one of the major problems limiting quality of life during aging. The accumulation of telomere dysfunction and DNA damage appears to be one of the underlying causes. Uncapping of chromosome ends in response to critical telomere shortening limits the proliferative capacity of human cells by activation of DNA damage checkpoints inducing senescence or apoptosis. Telomere shortening occurs in the vast majority of human tissues during aging and in chronic diseases that increase the rate of cell turnover. There is emerging evidence that telomere shortening can limit the maintenance and function of adult stem cells -- a cell type of utmost importance for organ maintenance and regeneration. In mouse models, telomere dysfunction leads to a depletion of adult stem cell compartments suggesting that stem cells are very sensitive to DNA damage. Both the rarity of stem and progenitor cells in adult organs and their removal in response to damage make it difficult to assess the impact of telomere dysfunction and DNA damage on stem and progenitor cell aging. Such approaches require the development of sensitive biomarkers recognizing low levels of telomere dysfunction and DNA damage in stem and progenitor cells. Here, we review experimental data on the prevalence of telomere dysfunction and DNA damage during aging and its possible impact on stem and progenitor cell aging.

Genes regulated by caloric restriction have unique roles within transcriptional networks

Caloric restriction (CR) has received much interest as an intervention that delays age-related disease and increases lifespan. Whole-genome microarrays have been used to identify specific genes underlying these effects, and in mice, this has led to the identification of genes with expression responses to CR that are shared across multiple tissue types. Such CR-regulated genes represent strong candidates for future investigation, but have been understood only as a list, without regard to their broader role within transcriptional networks. In this study, co-expression and network properties of CR-regulated genes were investigated using data generated by more than 600 Affymetrix microarrays. This analysis identified groups of co-expressed genes and regulatory factors associated with the mammalian CR response, and uncovered surprising network properties of CR-regulated genes. Genes downregulated by CR were highly connected and located in dense network regions. In contrast, CR-upregulated genes were weakly connected and positioned in sparse network regions. Some network properties were mirrored by CR-regulated genes from invertebrate models, suggesting an evolutionary basis for the observed patterns. These findings contribute to a systems-level picture of how CR influences transcription within mammalian cells, and point towards a comprehensive understanding of CR in terms of its influence on biological networks.

Transcriptome analysis provides new insights into liver changes induced in the rat upon dietary administration of the food additives butylated hydroxytoluene, curcumin, propyl gallate and thiabendazole

Transcriptomics was performed to gain insight into mechanisms of food additives butylated hydroxytoluene (BHT), curcumin (CC), propyl gallate (PG), and thiabendazole (TB), additives for which interactions in the liver can not be excluded. Additives were administered in diets for 28 days to Sprague-Dawley rats and cDNA microarray experiments were performed on hepatic RNA. BHT induced changes in the expression of 10 genes, including phase I (CYP2B1/2; CYP3A9; CYP2C6) and phase II metabolism (GST mu2). The CYP2B1/2 and GST expression findings were confirmed by real time RT-PCR, western blotting, and increased GST activity towards DCNB. CC altered the expression of 12 genes. Three out of these were related to peroxisomes (phytanoyl-CoA dioxygenase, enoyl-CoA hydratase; CYP4A3). Increased cyanide insensitive palmitoyl-CoA oxidation was observed, suggesting that CC is a weak peroxisome proliferator. TB changed the expression of 12 genes, including CYP1A2. In line, CYP1A2 protein expression was increased. The expression level of five genes, associated with p53 was found to change upon TB treatment, including p53 itself, GADD45alpha, DN-7, protein kinase C beta and serum albumin. These array experiments led to the novel finding that TB is capable of inducing p53 at the protein level, at least at the highest dose levels employed above the current NOAEL. The expression of eight genes changed upon PG administration. This study shows the value of gene expression profiling in food toxicology in terms of generating novel hypotheses on the mechanisms of action of food additives in relation to pathology.

Sirtuins: critical regulators at the crossroads between cancer and aging

Sirtuins (SIRTs 1-7), or class III histone deacetylases (HDACs), are protein deacetylases/ADP ribosyltransferases that target a wide range of cellular proteins in the nucleus, cytoplasm, and mitochondria for post-translational modification by acetylation (SIRT1, -2, -3 and -5) or ADP ribosylation (SIRT4 and -6). The orthologs of sirtuins in lower organisms play a critical role in regulating lifespan. As cancer is a disease of aging, we discuss the growing implications of the sirtuins in protecting against cancer development. Sirtuins regulate the cellular responses to stress and ensure that damaged DNA is not propagated and that mutations do not accumulate. SIRT1 also promotes replicative senescence under conditions of chronic stress. By participating in the stress response to genomic insults, sirtuins are thought to protect against cancer, but they are also emerging as direct participants in the growth of some cancers. Here, we review the growing implications of sirtuins both in cancer prevention and as specific and novel cancer therapeutic targets.

Nutrient-sensitive mitochondrial NAD+ levels dictate cell survival

A major cause of cell death caused by genotoxic stress is thought to be due to the depletion of NAD(+) from the nucleus and the cytoplasm. Here we show that NAD(+) levels in mitochondria remain at physiological levels following genotoxic stress and can maintain cell viability even when nuclear and cytoplasmic pools of NAD(+) are depleted. Rodents fasted for 48 hr show increased levels of the NAD(+) biosynthetic enzyme Nampt and a concomitant increase in mitochondrial NAD(+). Increased Nampt provides protection against cell death and requires an intact mitochondrial NAD(+) salvage pathway as well as the mitochondrial NAD(+)-dependent deacetylases SIRT3 and SIRT4. We discuss the relevance of these findings to understanding how nutrition modulates physiology and to the evolution of apoptosis.

Nutrient-sensitive mitochondrial NAD+ levels dictate cell survival

A major cause of cell death caused by genotoxic stress is thought to be due to the depletion of NAD(+) from the nucleus and the cytoplasm. Here we show that NAD(+) levels in mitochondria remain at physiological levels following genotoxic stress and can maintain cell viability even when nuclear and cytoplasmic pools of NAD(+) are depleted. Rodents fasted for 48 hr show increased levels of the NAD(+) biosynthetic enzyme Nampt and a concomitant increase in mitochondrial NAD(+). Increased Nampt provides protection against cell death and requires an intact mitochondrial NAD(+) salvage pathway as well as the mitochondrial NAD(+)-dependent deacetylases SIRT3 and SIRT4. We discuss the relevance of these findings to understanding how nutrition modulates physiology and to the evolution of apoptosis.

Neuroendocrine and immune characteristics of aging in avian species

Avian species show a remarkable diversity in lifespan. The differing lifespan patterns are found across a number of birds, in spite of higher body temperature and apparent increased metabolic rate. These characteristics make study of age-related changes of great interest, especially for understanding the biology of aging associated with surprisingly long lifespan in some birds. Our studies have focused on a short-lived avian model, the Japanese quail in order to describe reproductive aging and the neuroendocrine characteristics leading to reproductive senescence. Biomarkers of aging used in mammalian species include telomere length, oxidative damage, and selected metabolic indicators. These markers provide confirming evidence that the long-lived birds appear to age more slowly. A corollary area of interest is that of immune function and aging. Immune responses have been studied in selected wild birds and there has been a range of studies that have considered the effects of stress in wild and domestic species. Our laboratory studies have specifically tested response to immune challenge relative to aging in the quail model and these studies indicate that there is an age-related change in the qualitative aspects of the response. However, there are also intriguing differences in the ability of the aging quail to respond that differ from mammalian data. Finally, another approach to understanding aging is to attempt to develop or test strategies that may extend lifespan and presumably health. One area of great interest has been to consider the effect of calorie restriction, which is a treatment shown to extend lifespan in a variety of species. This approach is routinely used in domestic poultry as a means for extending reproductive function and enhancing health. Our data indicate that moderate calorie restriction has beneficial effects, and that physiological and endocrine responses reflect these benefits.

A forkhead in the road to longevity: the molecular basis of lifespan becomes clearer

OBJECTIVE

Although the quest for longevity is as old as civilization itself, only recently have technical and conceptual advances in genomics research brought us to the point of understanding the precise molecular events that make us age. This heralds an era when manipulations of these will enable us to live longer, healthier lives. The present review describes how recent experimental strategies have identified key genes and intracellular pathways that are responsible for ageing and longevity.

FINDINGS

In diverse species transcription factors belonging to the forkhead/winged helix box gene, group O (FOXO) subfamily have been found to be crucial in downstream suppression of the life-shortening effects of insulin/insulin-like growth factor-I receptor signalling pathways that, when upregulated, accelerate ageing by suppression of FOXO. The various adverse processes activated upon FOXO suppression include increased generation of reactive oxygen species (ROS). ROS are pivotal for the onset of various common conditions, including hypertension, atherosclerosis, type 2 diabetes, cancer and Alzheimer's disease, each of which shortens lifespan. In humans, FOXO3a, as well as FOXO1 and -4, and their downstream effectors, could hold the key to counteracting ageing and common diseases. An understanding of the processes controlled by these FOXOs should permit development of novel classes of agents that will more directly counteract or prevent the damage associated with diverse life-threatening conditions, and so foster a life of good health to a ripe old age. Just like caloric restriction, lifespan can be increased in various species by plant-derived polyphenols, such as resveratrol, via activation of sirtuins in cells. Sirtuins, such as SIRT1 in mammals, utilize FOXO and other pathways to achieve their beneficial effects on health and lifespan.

CONCLUSION

Lifespan is tractable and basic mechanisms are now known. Longevity research complements and overlaps research in most major medical disciplines. Current progress bodes well for an ever-increasing length of healthy life for those who adapt emerging knowledge personally (so-called 'longevitarians').

Toward a unified theory of caloric restriction and longevity regulation

The diet known as calorie restriction (CR) is the most reproducible way to extend the lifespan of mammals. Many of the early hypotheses to explain this effect were based on it being a passive alteration in metabolism. Yet, recent data from yeast, worms, flies, and mammals support the idea that CR is not simply a passive effect but an active, highly conserved stress response that evolved early in life's history to increase an organism's chance of surviving adversity. This perspective updates the evidence for and against the various hypotheses of CR, and concludes that many of them can be synthesized into a single, unifying hypothesis. This has important implications for how we might develop novel medicines that can harness these newly discovered innate mechanisms of disease resistance and survival.

Effects of caloric restriction on cell proliferation in several tissues in mice: role of intermittent feeding

Reduced cell proliferation may mediate anticarcinogenic effects of caloric restriction (CR). Using heavy water (2H2O) labeling, we investigated the cell proliferation response to CR in detail, including time course, effect of refeeding, and role of intermittent feeding with 5% CR. In the time-course study, 8-wk-old female C57BL/6J mice were placed on a 33% CR regimen (fed 3 times/wk) for varying durations. Compared with responses in controls fed ad libitum (AL), proliferation rates of keratinocytes, mammary epithelial cells, and T cells were markedly reduced within 2 wk of CR. In mice fed 95% ad libitum (C95, fed 3 times/wk), cell proliferation was also reduced in all tissues so that differences from 33% CR were only significant at 1 mo. In the refeeding study, mice were refed a C95 diet for varying durations after 1 mo of 33% CR. Cell proliferation rebounded to a suprabasal rate in all tissues after 2 wk of refeeding and then normalized after 2 mo, although the C95 group again exhibited lower cell proliferation than the AL group. The role of intermittent feeding was studied by comparing 33% CR and C95 animals (both fed intermittently) with animals fed isocalorically either daily or continuously by pellet dispenser. Intermittent feeding had no additive effect on 33% CR but reduced cell proliferation in all tissues at the 95% caloric intake level. In summary, the CR effect on cell proliferation is potent, rapid, and reversible in several tissues, and an intermittent feeding pattern reproduces much of the effect in the absence of substantial CR.

Role of sirtuin proteins in life extension by caloric restriction

The deacetylase activity of sirtuin proteins may play a key role in the life extending action of caloric restriction in organisms ranging from yeast to mammals. Recent research has been focused on the possible afferent pathway by which caloric restriction increases the deacetylase activity and on the efferent pathway by which the increased deacetylase activity extends life. Further research is needed to firmly establish the role of sirtuin proteins in life extension by caloric restriction in mammals.

The role of macroautophagy in the ageing process, anti-ageing intervention and age-associated diseases

Macroautophagy is a degradation/recycling system ubiquitous in eukariotic cells, which generates nutrients during fasting under the control of amino acids and hormones, and contributes to the turnover and rejuvenation of cellular components (long-lived proteins, cytomembranes and organelles). Tight coupling between these two functions may be the weak point in cell housekeeping. Ageing denotes a post-maturational deterioration of tissues and organs with the passage of time, due to the progressive accumulation of the misfunctioning cell components because of oxidative damage and an age-dependent decline of turnover rate and housekeeping. Caloric restriction (CR) and lower insulin levels may slow down many age-dependent processes and extend lifespan. Recent evidence is reviewed showing that autophagy is involved in ageing and in the anti-ageing action of anti-ageing calorie restriction: function of autophagy declines during adulthood and is almost negligible at older age; CR prevents the age-dependent decline of autophagic proteolysis and improves the sensitivity of liver cells to stimulation of lysosomal degradation; protection of autophagic proteolysis from the age-related decline co-varies with the duration and level of anti-ageing food restriction like the effects of CR extending lifespan; the pharmacological stimulation of macroautophagy has anti-ageing effects. Besides the involvement in ageing, macroautophagy may have an essential role in the pathogenesis of many age-associated diseases. Higher protein turnover may not fully account for the anti-ageing effects of macroautophagy, and effects of macroautophagy on housekeeping of the cell organelles, antioxidant machinery of cell membranes and transmembrane cell signaling should also be considered.

Balanced Regulation of mRNA Production for Fas and Fas Ligand in Lymphocytes From Centenarians

Background— The functionality of the immune system during aging is crucial for protection against the most common age-related diseases. Apoptosis plays a central role in the senescence of the immune system, as evidenced by the increased plasma membrane expression of a key molecule like Fas protein. We analyzed the mRNA levels of different forms of Fas (total [tFas] and membrane [mFas]) and of its ligand (FasL) in peripheral blood lymphocytes from centenarians, the best example of successful aging, who were compared with young and middle-aged donors.

Methods and Results— Using real-time polymerase chain reaction, we quantified mRNA for different forms of Fas and for FasL. In resting lymphocytes, mRNA for tFas, but not for mFas, significantly increases with age, whereas FasL mRNA significantly decreases. In vitro production of Fas/FasL mRNA after different stimuli was similar in cells from the 3 groups. Even if the percentage of Fas + cells was higher than in the other groups, peripheral blood lymphocytes from centenarians had normal Fas-induced apoptosis, as revealed by flow cytometry. By ELISA, we observed that cells from centenarians showed normal in vitro production of the soluble form of Fas (sFas) and that plasma levels of such molecule were significantly higher in centenarians than in the other groups.

Conclusions— Lymphocytes from centenarians are able to balance the production of proapoptotic (mFas and FasL) and antiapoptotic (sFas) molecules, whose proportions are likely crucial for the well-preserved immune functionality at the extreme limits of human life.

Energy restriction and aging

PURPOSE OF REVIEW

The focus of this review is on current research involving long-term calorie restriction and the resulting changes observed in possible biomarkers of aging. Special emphasis will be given to the basic and clinical science studies which are currently investigating the effects of controlled, high-quality energy-restricted diets on both biomarkers of longevity and on the development of chronic diseases related to age and obesity in humans.

RECENT FINDINGS

Prolonged calorie restriction has been shown to extend both the median and maximal lifespan in a variety of lower species such as yeast, worms, fish, rats, and mice. Mechanisms of this lifespan extension via calorie restriction are not fully elucidated, but possibly involve significant alterations in energy metabolism, oxidative damage, insulin sensitivity, and functional changes in both the neuroendocrine and sympathetic nervous systems. Ongoing studies of prolonged energy restriction in humans are now making it possible to analyze changes in these aging biomarkers to unravel some of the mechanisms of its antiaging phenomenon.

SUMMARY

With the incremental expansion of research endeavors in the area of energy or calorie restriction, data on the effects of calorie restriction in animal models and humans are becoming more accessible. Detailed analyses from controlled human trials involving long-term calorie restriction will allow investigators to link observed alterations in body composition down to changes in molecular pathways and gene expression, with their possible effects on the biomarkers of aging.

Calorie restriction promotes mammalian cell survival by inducing the SIRT1 deacetylase

A major cause of aging is thought to result from the cumulative effects of cell loss over time. In yeast, caloric restriction (CR) delays aging by activating the Sir2 deacetylase. Here we show that expression of mammalian Sir2 (SIRT1) is induced in CR rats as well as in human cells that are treated with serum from these animals. Insulin and insulin-like growth factor 1 (IGF-1) attenuated this response. SIRT1 deacetylates the DNA repair factor Ku70, causing it to sequester the proapoptotic factor Bax away from mitochondria, thereby inhibiting stress-induced apoptotic cell death. Thus, CR could extend life-span by inducing SIRT1 expression and promoting the long-term survival of irreplaceable cells.

Proinflammatory phenotype of coronary arteries promotes endothelial apoptosis in aging

Previously we demonstrated that aging in coronary arteries is associated with proinflammatory phenotypic changes and decreased NO bioavailability, which, we hypothesized, promotes vascular disease by enhancing endothelial apoptosis. To test this hypothesis we characterized proapoptotic alterations in the phenotype of coronary arteries of aged (26 mo old) and young (3 mo old) F344 rats. DNA fragmentation analysis and TUNEL assay showed that in aged vessels there was an approximately fivefold increase in the number of apoptotic endothelial cells. In aged coronary arteries there was an increased expression of TNFα, TNFβ, and caspase 9 (microarray, real-time PCR), as well as increased caspase 9 and caspase 3 activity, whereas expression of TNFR1, TNFα-converting enzyme (TACE), Bcl-2, Bcl-X(L), Bid, Bax, caspase 8, and caspase 3 were unchanged. In vessel culture (18 h) incubation of aged coronary arteries with a TNF blocking antibody or the NO donor S-nitroso-penicillamine (SNAP) decreased apoptotic cell death. Incubation of young arteries with exogenous TNFα increased caspase 9 activity and elicited endothelial apoptosis, which was attenuated by SNAP. Inhibition of NO synthesis in cultured young coronary arteries also induced apoptotic cell death and potentiated the apoptotic effect of TNFα. Thus we propose that age-related upregulation of TNFα and caspase 9 and decreased bioavailability of NO promote endothelial apoptosis in coronary arteries that may lead to impaired endothelial function and ischemic heart disease in the elderly.

Identification of the Apoptosis Activation Cascade Induced in Mammary Carcinomas by Energy Restriction

Energy restriction (ER) inhibits mammary carcinogenesis and results in a marked reduction in tumor size, effects likely to be explained by ER-mediated induction of apoptosis. The goal of this study was to investigate the molecular mechanism(s) accounting for apoptosis induction. To do this, chemically induced mammary carcinomas were evaluated from rats that were ad libitum fed (control), 40% ER, or 40% ER but energy repleted for 7 days before study termination (ER-REP); the ER-REP group permitted the determination of the reversibility of ER-mediated effects. Cleaved products of poly(ADP-ribose) polymerase 1 were elevated by ER (P < 0.025) providing biochemical evidence of apoptosis induction. cDNA microarray analysis identified the Bcl-2, CARD, and IAP functional gene groupings as being involved in apoptosis induction. Consistent with the microarray data, the activities of caspases 9 and 3 were observed to be approximately 2-fold higher in carcinomas from ER rats (P < or =0.01), whereas caspase 8 activity was similar in carcinomas from all three of the groups. This evidence that ER-induced apoptosis mediated by the mitochondrial pathway was additionally supported by the finding that levels of Bcl-2, Bcl-xl, and XIAP protein were significantly lower (P < 0.01), and levels of Bax and Apaf-1 were elevated (P < 0.02) in ER carcinomas versus those carcinomas from control or ER-REP rats. Additional studies revealed that Akt phosphorylation (activation) was reduced in mammary carcinomas from ER rats. Thus, it appears that ER induces apoptosis in mammary carcinomas via a cell survival factor-dependent pathway.