Overview of caloric restriction and ageing

Conserved regulators of cognitive aging: From worms to humans

Cognitive decline is a major deficit that arises with age in humans. While some research on the underlying causes of these problems can be done in humans, harnessing the strengths of small model systems, particularly those with well-studied longevity mutants, such as the nematode C. elegans, will accelerate progress. Here we review the approaches being used to study cognitive decline in model organisms and show how simple model systems allow the rapid discovery of conserved molecular mechanisms, which will eventually enable the development of therapeutics to slow cognitive aging.

Cellular oxidative damage is more sensitive to biosynthetic rate than to metabolic rate: A test of the theoretical model on hornworms (Manduca sexta larvae)

We develop a theoretical model from an energetic viewpoint for unraveling the entangled effects of metabolic and biosynthetic rates on oxidative cellular damage accumulation during animal's growth, and test the model by experiments in hornworms. The theoretical consideration suggests that most of the cellular damages caused by the oxidative metabolism can be repaired by the efficient maintenance mechanisms, if the energy required by repair is unlimited. However, during growth a considerable amount of energy is allocated to the biosynthesis, which entails tradeoffs with the requirements of repair. Thus, the model predicts that cellular damage is more influenced by the biosynthetic rate than the metabolic rate. To test the prediction, we induced broad variations in metabolic and biosynthetic rates in hornworms, and assayed the lipid peroxidation and protein carbonyl. We found that the increase in the cellular damage was mainly caused by the increase in biosynthetic rate, and the variations in metabolic rate had negligible effect. The oxidative stress hypothesis of aging suggests that high metabolism leads to high cellular damage and short lifespan. However, some empirical studies showed that varying biosynthetic rate, rather than metabolic rate, changes animal's lifespan. The conflicts between the empirical evidence and the hypothesis are reconciled by this study.

DNA Damage: A Main Determinant of Vascular Aging

Vascular aging plays a central role in health problems and mortality in older people. Apart from the impact of several classical cardiovascular risk factors on the vasculature, chronological aging remains the single most important determinant of cardiovascular problems. The causative mechanisms by which chronological aging mediates its impact, independently from classical risk factors, remain to be elucidated. In recent years evidence has accumulated that unrepaired DNA damage may play an important role. Observations in animal models and in humans indicate that under conditions during which DNA damage accumulates in an accelerated rate, functional decline of the vasculature takes place in a similar but more rapid or more exaggerated way than occurs in the absence of such conditions. Also epidemiological studies suggest a relationship between DNA maintenance and age-related cardiovascular disease. Accordingly, mouse models of defective DNA repair are means to study the mechanisms involved in biological aging of the vasculature. We here review the evidence of the role of DNA damage in vascular aging, and present mechanisms by which genomic instability interferes with regulation of the vascular tone. In addition, we present potential remedies against vascular aging induced by genomic instability. Central to this review is the role of diverse types of DNA damage (telomeric, non-telomeric and mitochondrial), of cellular changes (apoptosis, senescence, autophagy), mediators of senescence and cell growth (plasminogen activator inhibitor-1 (PAI-1), cyclin-dependent kinase inhibitors, senescence-associated secretory phenotype (SASP)/senescence-messaging secretome (SMS), insulin and insulin-like growth factor 1 (IGF-1) signaling), the adenosine monophosphate-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR)-nuclear factor kappa B (NFκB) axis, reactive oxygen species (ROS) vs. endothelial nitric oxide synthase (eNOS)-cyclic guanosine monophosphate (cGMP) signaling, phosphodiesterase (PDE) 1 and 5, transcription factor NF-E2-related factor-2 (Nrf2), and diet restriction.

Differences in genome-wide gene expression response in peripheral blood mononuclear cells between young and old men upon caloric restriction

Background

Caloric restriction (CR) is considered to increase lifespan and to prevent various age-related diseases in different nonhuman organisms. Only a limited number of CR studies have been performed on humans, and results put CR as a beneficial tool to decrease risk factors in several age-related diseases. The question remains at what age CR should be implemented to be most effective with respect to healthy aging. The aim of our study was to elucidate the role of age in the transcriptional response to a completely controlled 30 % CR diet on immune cells, as immune response is affected during aging. Ten healthy young men, aged 20–28, and nine healthy old men, aged 64–85, were subjected to a 2-week weight maintenance diet, followed by 3 weeks of 30 % CR. Before and after 30 % CR, the whole genome gene expression in peripheral blood mononuclear cells (PBMCs) was assessed.

Results

Expression of 554 genes showed a different response between young and old men upon CR. Gene set enrichment analysis revealed a downregulation of gene sets involved in the immune response in young but not in old men. At baseline, immune response-related genes were higher expressed in old compared to young men. Upstream regulator analyses revealed that most potential regulators were controlling the immune response.

Conclusions

Based on the gene expression data, we theorise that a short period of CR is not effective in old men regarding immune-related pathways while it is effective in young men.

Trial registration

ClinicalTrials.gov, NCT00561145

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-016-0528-0) contains supplementary material, which is available to authorized users.

The dog aging project: translational geroscience in companion animals

Studies of the basic biology of aging have identified several genetic and pharmacological interventions that appear to modulate the rate of aging in laboratory model organisms, but a barrier to further progress has been the challenge of moving beyond these laboratory discoveries to impact health and quality of life for people. The domestic dog, Canis familiaris, offers a unique opportunity for surmounting this barrier in the near future. In particular, companion dogs share our environment and play an important role in improving the quality of life for millions of people. Here, we present a rationale for increasing the role of companion dogs as an animal model for both basic and clinical geroscience and describe complementary approaches and ongoing projects aimed at achieving this goal.

Nutritional ecology and the evolution of aging

Considerable progress has been made in understanding both evolutionary and mechanistic aspects of biological aging, although the two areas remain poorly integrated. We suggest that a greater emphasis on ecology can help to remedy this, by focusing on the interface between biological mechanisms and the environments in which they evolved by natural selection. Among the most salient aspects of the environment relevant to aging is nutrition, and yet in the bulk of aging research nutrition is coarsely represented as dietary restriction or caloric restriction, without consideration for how specific components of diet, beyond "energy" (the undifferentiated mix of macronutrients), are driving the observed effects. More recently, it has become clear that specific nutrients (notably amino acids) and interactions among nutrients (i.e., nutritional balance) play important roles in the biology of aging. We show how a method developed in nutritional ecology, called the Geometric Framework for nutrition, can help to understand the nutritional interactions of animals with their environments, by explicitly distinguishing the roles of calories, individual nutrients and nutrient balance. Central to these models are the active regulatory responses that animals use to mediate between variation in the nutritional environment and fitness-related consequences such as lifespan and reproduction. These homeostatic responses provide a guide for researchers that can help to link the biological mechanisms with evolutionary processes in the context of a multi-dimensional nutritional environment.

Whole-transcriptome analysis of mouse adipose tissue in response to short-term caloric restriction

Caloric restriction (CR) has been shown to extend the lifespan of many species by improving cellular function and organismal health. Additionally, fat reduction by CR may play an important role in lengthening lifespan and preventing severe age-related diseases. Interestingly, CR induced the greatest transcriptome change in the epididymal fat of mice in our study. In this transcriptome analysis, we identified and categorized 446 genes that correlated with CR level. We observed down-regulation of several signaling pathways, including insulin/insulin-like growth factor 1 (insulin/IGF-1), epidermal growth factor (EGF), transforming growth factor beta (TGF-β), and canonical wingless-type mouse mammary tumor virus integration site (Wnt). Many genes related to structural features, including extracellular matrix structure, cell adhesion, and the cytoskeleton, were down-regulated, with a strong correlation to the degree of CR. Furthermore, genes related to the cell cycle and adipogenesis were down-regulated. These biological processes are well-identified targets of insulin/IGF-1, EGF, TGF-β, and Wnt signaling. In contrast, genes involved in specific metabolic processes, including the tricarboxylic acid cycle and the electron transport chain were up-regulated. We performed in silico analysis of the promoter sequences of CR-responsive genes and identified two associated transcription factors, Paired-like homeodomain 2 (Pitx2) and Paired box gene 6 (Pax6). Our results suggest that strict regulation of signaling pathways is critical for creating the optimal energy homeostasis to extend lifespan.

Factors that Affect Pancreatic Islet Cell Autophagy in Adult Rats: Evaluation of a Calorie-Restricted Diet and a High-Fat Diet

Aging may be a risk factor for type 2 diabetes in the elderly. Dietary intervention can affect glucose tolerance in adults, which may be due to body composition and islet cell autophagy. The aim of this study was to determine the effects of various dietary interventions on islet cell autophagy. Pancreatic tissue and blood samples were collected from Sprague Dawley rats (14–16 months old, n = 15 for each group) that received a normal diet (ND), a high-fat diet (HFD), or a calorie-restricted diet (CRD). The body weight (BW), visceral fat, serum lipid levels, fasting serum glucose, insulin levels, and β/α cell area were determined in 14-16-(0-w), 16-18-(8-w), and 18-20(16-w)-month-old rats. Pancreatic islet autophagy (LC3B and LAMP2), AP (Acid Phosphatase) and apoptosis (apoptosis index, AI (TUNEL assay) and cleaved caspase-3) were detected using immunohistochemistry, ELISA and western blot. At 16 weeks, the expressions of LC3B, LAMP2 and AP markedly increased in both the HFD (P<0.01) and CRD (P<0.05) groups; however, an increase in the AI (P<0.05), cleaved caspase-3 and Beclin1 expression and a decrease in the expressions of BCL2 and BCLXL (P<0.05) were observed in only the HFD group. FFA, triglyceride levels, HOMA-IR, insulin levels and glucagon levels were significantly increased in the HFD group but decreased in the CRD group at 16 weeks (P<0.05). The degree of islet cell autophagy was potentially regulated by the levels of FFA and islet cell insulin and glucagon, which may have been due to the effects of Beclin1/BCL2.

Withanolide A offers neuroprotection, ameliorates stress resistance and prolongs the life expectancy of Caenorhabditis elegans

Withanolide A (steroidal lactone) forms the major constituent of the most popular herbal drug in Ayurvedic medicine, Ashwagandha. It has been used since ancient times as an alternative medicine for the treatment of a variety of age related disorders. Here we provide multiple lines of evidence indicating that Withanolide A improves healthspan, delays age-associated physiological changes and also extends the lifespan of Caenorhabditis elegans. We also report several neuroprotective benefits of this natural product, including its anti-amyloidogenic effects, alleviation of α-synuclein aggregation and neuroprotection through modulation of neural mediators like acetylcholine. We observed that Withanolide A mediates lifespan extension and promotes stress resistance via insulin/insulin-like growth factor signaling pathway. Such findings could be helpful to develop a therapeutic medicine from this natural product for the prevention or reversal of age-related ailments and to improve the survival of patients suffering from Alzheimer's or Parkinson's disease.

The impact of low-protein high-carbohydrate diets on aging and lifespan

Most research on nutritional effects on aging has focussed on the impact of manipulating single dietary factors such as total calorie intake or each of the macronutrients individually. More recent studies using a nutritional geometric approach called the Geometric Framework have facilitated an understanding of how aging is influenced across a landscape of diets that vary orthogonally in macronutrient and total energy content. Such studies have been performed using ad libitum feeding regimes, thus taking into account compensatory feeding responses that are inevitable in a non-constrained environment. Geometric Framework studies on insects and mice have revealed that diets low in protein and high in carbohydrates generate longest lifespans in ad libitum-fed animals while low total energy intake (caloric restriction by dietary dilution) has minimal effect. These conclusions are supported indirectly by observational studies in humans and a heterogeneous group of other types of interventional studies in insects and rodents. Due to compensatory feeding for protein dilution, low-protein, high-carbohydrate diets are often associated with increased food intake and body fat, a phenomenon called protein leverage. This could potentially be mitigated by supplementing these diets with interventions that influence body weight through physical activity and ambient temperature.

The Biology of Aging: Citizen Scientists and Their Pets as a Bridge Between Research on Model Organisms and Human Subjects

A fundamental goal of research into the basic mechanisms of aging is to develop translational strategies that improve human health by delaying the onset and progression of age-related pathology. Several interventions have been discovered that increase life span in invertebrate organisms, some of which have similar effects in mice. These include dietary restriction and inhibition of the mechanistic target of rapamycin by treatment with rapamycin. Key challenges moving forward will be to assess the extent to which these and other interventions improve healthy longevity and increase life span in mice and to develop practical strategies for extending this work to the clinic. Companion animals may provide an optimal intermediate between laboratory models and humans. By improving healthy longevity in companion animals, important insights will be gained regarding human aging while improving the quality of life for people and their pets.

Cardiac Sirt1 mediates the cardioprotective effect of caloric restriction by suppressing local complement system activation after ischemia-reperfusion

Caloric restriction (CR) confers cardioprotection against ischemia-reperfusion (I/R) injury. We previously found the essential roles of endothelial nitric oxide synthase in the development of CR-induced cardioprotection and Sirt1 activation during CR (Shinmura K, Tamaki K, Ito K, Yan X, Yamamoto T, Katsumata Y, Matsuhashi T, Sano M, Fukuda K, Suematsu M, Ishii I. Indispensable role of endothelial nitric oxide synthase in caloric restriction-induced cardioprotection against ischemia-reperfusion injury.Am J Physiol Heart Circ Physiol 308: H894-H903, 2015). However, the exact mechanism by which Sirt1 in cardiomyocytes mediates the cardioprotective effect of CR remains undetermined. We subjected cardiomyocyte-specific Sirt1 knockout (CM-Sirt1(-/-)) mice and the corresponding control mice to either 3-mo ad libitum feeding or CR (-40%). Isolated perfused hearts were subjected to 25-min global ischemia, followed by 60-min reperfusion. The recovery of left ventricle function after I/R was improved, and total lactate dehydrogenase release into the perfusate during reperfusion was attenuated in the control mice treated with CR, but a similar cardioprotective effect of CR was not observed in the CM-Sirt1(-/-)mice. The expression levels of cardiac complement component 3 (C3) at baseline and the accumulation of C3 and its fragments in the ischemia-reperfused myocardium were attenuated by CR in the control mice, but not in the CM-Sirt1(-/-)mice. Resveratrol treatment also attenuated the expression levels of C3 protein in cultured neonatal rat ventricular cardiomyocytes. Moreover, the degree of myocardial I/R injury in conventional C3 knockout (C3(-/-)) mice treated with CR was similar to that in the ad libitum-fed C3(-/-)mice, although the expression levels of Sirt1 were enhanced by CR. These results demonstrate that cardiac Sirt1 plays an essential role in CR-induced cardioprotection against I/R injury by suppressing cardiac C3 expression. This is the first report suggesting that cardiac Sirt1 regulates the local complement system during CR.

The impact of nutrients on the aging rate: A complex interaction of demographic, environmental and genetic factors

Nutrition has a strong influence on the health status of the elderly, with many dietary components associated to either an increased risk of disease or to an improvement of the quality of life and to a delay of age-related pathologies. A direct effect of a reduced caloric intake on the delay of aging phenotypes is documented in several organisms. The role of nutrients in the regulation of human lifespan is not easy to disentangle, influenced by a complex interaction of nutrition with environmental and genetic factors. The individual genetic background is fundamental for mediating the effects of nutritional components on aging. Classical genetic factors able to influence nutrient metabolism are considered those belonging to insulin/insulin growth factor (INS/IGF-1) signaling, TOR signaling and Sirtuins, but also genes involved in inflammatory/immune response and antioxidant activity can have a major role. Considering the worldwide increasing interest in nutrition to prevent age related diseases and achieve a healthy aging, in this review we will discuss this complex interaction, in the light of metabolic changes occurring with aging, with the aim of shedding a light on the enormous complexity of the metabolic scenario underlying longevity phenotype.

Neuroprotective effects of metformin against Aβ-mediated inhibition of long-term potentiation in rats fed a high-fat diet

Metformin (Met) is used to treat neurodegenerative disorders such as Alzheimer's disease (AD). Conversely, high-fat diets (HFD) have been shown to increase AD risk. In this study, we investigated the neuroprotective effects of Met on β-amyloid (Aβ)-induced impairments in hippocampal synaptic plasticity in AD model rats that were fed a HFD. In this study, 32 adult male Wistar rats were randomly assigned to four groups: group I (control group, regular diet); group II (HFD+vehicle); group III (HFD+Aβ); or group IV (Met+HFD+Aβ). Rats fed a HFD were injected with Aβ to induce AD, allowed to recover, and treated with Met for 8 weeks. The rats were then anesthetized with intraperitoneal injections of urethane and placed in a stereotaxic apparatus for surgery, electrode implantation, and field potential recording. In vivo electrophysiological recordings were then performed to measure population spike (PS) amplitude and excitatory postsynaptic potential (EPSP) slope in the hippocampal dentate gyrus. Long-term potentiation (LTP) was induced by high-frequency stimulation of the perforant pathway. Blood samples were then collected to measure plasma levels of triglycerides, low-density lipoproteins, very low-density lipoprotein, and cholesterol. After induction of LTP, PS amplitude and EPSP slope were significantly decreased in Aβ-injected rats fed a HFD compared to vehicle-injected animals or untreated animals that were fed a normal diet. Met treatment of Aβ-injected rats significantly attenuated these decreases, suggesting that Met decreased the effects of Aβ on LTP. These findings suggest that Met treatment is neuroprotective against the detrimental effects of Aβ and HFDs on hippocampal synaptic plasticity.

Thyroxine modifies the effects of growth hormone in Ames dwarf mice

Ames dwarf (df/df) mice lack growth hormone (GH), thyroid stimulating hormone and prolactin. Treatment of juvenile df/df mice with GH alone stimulates somatic growth, reduces insulin sensitivity and shortens lifespan. Early‐life treatment with thyroxine (T4) alone produces modest growth stimulation but does not affect longevity. In this study, we examined the effects of treatment of juvenile Ames dwarf mice with a combination of GH + T4 and compared them to the effects of GH alone. Treatment of female and male dwarfs with GH + T4 between the ages of 2 and 8 weeks rescued somatic growth yet did not reduce lifespan to match normal controls, thus contrasting with the previously reported effects of GH alone. While the male dwarf GH + T4 treatment group had no significant effect on lifespan, the female dwarfs undergoing treatment showed a decrease in maximal longevity. Expression of genes related to GH and insulin signaling in the skeletal muscle and white adipose tissue (WAT) of female dwarfs was differentially affected by treatment with GH + T4 vs. GH alone. Differences in the effects of GH + T4 vs. GH alone on insulin target tissues may contribute to the differential effects of these treatments on longevity.

Aging and computational systems biology

Aging research is undergoing a paradigm shift, which has led to new and innovative methods of exploring this complex phenomenon. The systems biology approach endeavors to understand biological systems in a holistic manner, by taking account of intrinsic interactions, while also attempting to account for the impact of external inputs, such as diet. A key technique employed in systems biology is computational modeling, which involves mathematically describing and simulating the dynamics of biological systems. Although a large number of computational models have been developed in recent years, these models have focused on various discrete components of the aging process, and to date no model has succeeded in completely representing the full scope of aging. Combining existing models or developing new models may help to address this need and in so doing could help achieve an improved understanding of the intrinsic mechanisms which underpin aging.

Effects of food variability on growth and reproduction of Aedes aegypti

Despite a large body of knowledge about the evolution of life histories, we know little about how variable food availability during an individual's development affects its life history. We measured the effects of manipulating food levels during early and late larval development of the mosquito Aedes aegypti on its growth rate, life history and reproductive success. Switching from low to high food led to compensatory growth: individuals grew more rapidly during late larval development and emerged at a size close to that of mosquitoes consistently reared at high food. However, switching to high food had very little effect on longevity, and fecundity and reproductive success were considerably lower than in consistently well-fed mosquitoes. Changing from high to low food led to adults with similar size as in consistently badly nourished mosquitoes, but even lower fecundity and reproductive success. A rapid response of growth to changing resources can thus have unexpected effects in later life and in lifetime reproductive success. More generally, our study emphasizes the importance of varying developmental conditions for the evolutionary pressures underlying life-history evolution.

FoxO1 signaling plays a pivotal role in the cardiac telomere biology responses to calorie restriction

This study examined whether the forkhead transcription factors of O group 1 (FoxO1) might be involved in telomere biology during calorie restriction (CR). We used FoxO1-knockout heterozygous mice (FoxO1^+/−) and wild-type mice (WT) as a control. Both WT and FoxO1^+/− were subjected to ad libitum (AL) feeding or 30 % CR compared to AL for 20 weeks from 15 weeks of age. The heart-to-body weight ratio, blood glucose, and serum lipid profiles were not different among all groups of mice at the end of the study. Telomere size was significantly lower in the FoxO1^+/−-AL than the WT-AL, and telomere attrition was not observed in either WT-CR or FoxO1^+/−-CR. Telomerase activity was elevated in the heart and liver of WT-CR, but not in those of FoxO1^+/−-CR. The phosphorylation of Akt was inhibited and Sirt 1 was activated in heart tissues of WT-CR and FoxO1^+/−-CR. However, the ratio of conjugated to cytosolic light chain 3 increased and the level of p62 decreased in WT-CR, but not in FoxO1^+/−-CR. A marker of oxidative DNA damage, 8-OhdG, was significantly lower in WT-CR only. The level of MnSOD and eNOS increased, and the level of cleaved caspase-3 decreased in WT-CR, but not FoxO1^+/−-CR. Echocardiography showed that the left ventricular end-diastolic and systolic dimensions were significantly lower in WT-CR or FoxO1^+/−-CR than WT-AL or FoxO1^+/−-AL, respectively. The present studies suggest that FoxO1 plays beneficial roles by inducing genes involved in telomerase activity, as well as anti-oxidant, autophagic, and anti-apoptotic genes under conditions of CR, and suggest that FoxO1 signaling may be an important mediator of metabolic equilibrium during CR.

Transcriptome analysis in calorie-restricted rats implicates epigenetic and post-translational mechanisms in neuroprotection and aging

BACKGROUND

Caloric restriction (CR) can increase longevity in rodents and improve memory function in humans. α-Lipoic acid (LA) has been shown to improve memory function in rats, but not longevity. While studies have looked at survival in rodents after switching from one diet to another, the underlying mechanisms of the beneficial effects of CR and LA supplementation are unknown. Here, we use RNA-seq in cerebral cortex from rats subjected to CR and LA-supplemented rats to understand how changes in diet can affect aging, neurodegeneration and longevity.

RESULTS

Gene expression changes during aging in ad libitum-fed rats are largely prevented by CR, and neuroprotective genes are overexpressed in response to both CR and LA diets with a strong overlap of differentially expressed genes between the two diets. Moreover, a number of genes are differentially expressed specifically in rat cohorts exhibiting diet-induced life extension. Finally, we observe that LA supplementation inhibits histone deacetylase (HDAC) protein activity in vitro in rat astrocytes. We find a single microRNA, miR-98-3p, that is overexpressed during CR feeding and LA dietary supplementation; this microRNA alters HDAC and histone acetyltransferase (HAT) activity, which suggests a role for HAT/HDAC homeostasis in neuroprotection.

CONCLUSIONS

This study presents extensive data on the effects of diet and aging on the cerebral cortex transcriptome, and also emphasises the importance of epigenetics and post-translational modifications in longevity and neuroprotection.

Beneficial Effects of Caloric Restriction on Chronic Kidney Disease in Rodent Models: A Meta-Analysis and Systematic Review

BACKGROUND

Numerous studies have demonstrated the life-extending effect of caloric restriction. It is generally accepted that caloric restriction has health benefits, such as prolonging lifespan and delaying the onset and progression of CKD in various species, especially in rodent models. Although many studies have tested the efficacy of caloric restriction, no complete quantitative analysis of the potential beneficial effects of reducing caloric intake on the development and progression of CKD has been published.

METHODS

All studies regarding the relationship between caloric restriction and chronic kidney diseases were searched in electronic databases, including PubMed/MEDLINE, EMBASE, Science Citation Index (SCI), OVID evidence-based medicine, Chinese Bio-medical Literature and Chinese science and technology periodicals (CNKI, VIP, and Wan Fang). The pooled odds ratios (OR) and 95% confidence intervals (95% CI) were calculated by using fixed- or random-effects models.

RESULTS

The data from 27 of all the studies mentioned above was used in the Meta analysis. Through the meta-analysis, we found that the parameter of blood urea nitrogen, serum creatinine and urinary protein levels of the AL group was significant higher than that of the CR group, which are 4.11 mg/dl, 0.08mg/dl and 33.20mg/kg/24h, respectively. The incidence of the nephropathy in the caloric restriction (CR) group was significantly lower than that in the ad libitum-fed (AL) group. We further introduced the subgroup analysis and found that the effect of caloric restriction on the occurrence of kidney disease was only significant with prolonged intervention; the beneficial effects of CR on the 60%-caloric-restriction group were greater than on the less-than-60%-caloric-restriction group, and caloric restriction did not show obvious protective effects in genetically modified strains. Moreover, survival rate of the caloric restriction group is much higher than that of the ad libitum-fed (AL) group.

CONCLUSIONS

Our findings demonstrate for the first time that compared with the AL group, the caloric restriction indeed decreased urea nitrogen, creatinine, urine protein, incidence of kidney diseases and increased the survival rate on 700~800 days.

[Strategies for successful ageing]

There has been an increase in the interest of anti-ageing medicine in the last few years, with a growth in the industry of products that promise to prolong life and restore all the suffering or "defects" produced by age. The understanding of ageing has changed over the years, giving rise to the possibility of intervening in different metabolic and cellular pathways, and thus, delaying the appearance of the degenerative chronic diseases that appear with age, and that are finally the causing factors of the vulnerability that leads to our death. It is hoped that we can help the clinician to orientate their patients, who, due to the overwhelming amount of information they receive by the Internet, arrive at the clinic full of questions, waiting to receive absolute answer from their physician in order to increase their longevity and quality of life. This article presents an analysis of the physical activity, diets, supplements and drugs that are being investigated as anti-ageing measures and of the many clinical studies that have produced encouraging, measurable and reproducible results.

β-Guanidinopropionic acid extends the lifespan of Drosophila melanogaster via an AMP-activated protein kinase-dependent increase in autophagy

Previous studies have demonstrated that AMP‐activated protein kinase (AMPK) controls autophagy through the mammalian target of rapamycin (mTOR) and Unc‐51 like kinase 1 (ULK1/Atg1) signaling, which augments the quality of cellular housekeeping, and that β‐guanidinopropionic acid (β‐GPA), a creatine analog, leads to a chronic activation of AMPK. However, the relationship between β‐GPA and aging remains elusive. In this study, we hypothesized that feeding β‐GPA to adult Drosophila produces the lifespan extension via activation of AMPK‐dependent autophagy. It was found that dietary administration of β‐GPA at a concentration higher than 900 mm induced a significant extension of the lifespan of Drosophila melanogaster in repeated experiments. Furthermore, we found that Atg8 protein, the homolog of microtubule‐associated protein 1A/1B‐light chain 3 (LC3) and a biomarker of autophagy in Drosophila, was significantly upregulated by β‐GPA treatment, indicating that autophagic activity plays a role in the effect of β‐GPA. On the other hand, when the expression of Atg5 protein, an essential protein for autophagy, was reduced by RNA interference (RNAi), the effect of β‐GPA on lifespan extension was abolished. Moreover, we found that AMPK was also involved in this process. β‐GPA treatment significantly elevated the expression of phospho‐T172‐AMPK levels, while inhibition of AMPK by either AMPK‐RNAi or compound C significantly attenuated the expression of autophagy‐related proteins and lifespan extension in Drosophila. Taken together, our results suggest that β‐GPA can induce an extension of the lifespan of Drosophila via AMPK‐Atg1‐autophagy signaling pathway.

Life history trade-offs imposed by dragline use in two money spiders

Trade-offs among life history traits are central to understanding the limits of adaptations to stress. In animals, virtually all decisions taken during life are expected to have downstream consequences. To what degree rare, but energy-demanding, decisions carry over to individual performance is rarely studied in arthropods. We used spiders as a model system to test how single investments in silk use - for dispersal or predator escape - affect individual performance. Silk produced for safe lines and as threads for ballooning is of the strongest kind and is energetically costly, especially when resources are limited. We induced dragline spinning in two species of money spider at similar quantities to that under natural conditions and tested trade-offs with lifespan and egg sac production under unlimited prey availability and a dietary restriction treatment. We demonstrate strong trade-offs between dragline spinning and survival and fecundity. Survival trade-offs were additive to those imposed by the dietary treatment, but a reduction in eggs produced after silk use was only prevalent under conditions where food was restricted during the spider's life. Because draglines are not recycled after their use for dispersal or predator escape, their spinning incurs substantial fitness costs in dispersal, especially in environments with prey limitation. Rare but energetically costly decisions related to dispersal or predator escape may thus carry over to adult performance and explain phenotypic heterogeneity in natural populations.

Protection against renal ischemia-reperfusion injury through hormesis? Dietary intervention versus cold exposure

AIM

Dietary restriction (DR) and fasting (FA) induce robust protection against the detrimental effects of renal ischemia-reperfusion injury (I/RI). Several mechanisms of protection have been proposed, such as hormesis. Hormesis is defined as a life-supporting beneficial effect resulting from the cellular responses to single or multiple rounds of (mild) stress. The cold exposure (CE) model is a stress model similar to DR, and has been shown to have hormetic effects and has proved to increase longevity. CE is considered to be the most robust method to increase metabolism through activation of brown adipocytes. BAT has been considered important in etiology of obesity and its metabolic consequences.

MATERIALS AND METHODS

Since DR, FA, and CE models are proposed to work through hormesis, we investigated physiology of adipose tissue and effect on BAT in these models and compared them to ad libitum (AL) fed mice. We also studied the differential effect of these stress models on immunological changes, and effect of CE on renal I/RI.

KEY FINDINGS

We show similar physiological changes in adiposity in male C57Bl/6 mice due to DR, FA and CE, but the CE mice were not protected against renal I/RI. The immunophenotypic changes observed in the CE mice were similar to the AL animals, in contrast to FA mice, that showed major immunophenotypic changes in the B and T cell development stages in primary and secondary lymphoid organs.

SIGNIFICANCE

Our findings thus demonstrate that DR, FA and CE are hormetic stress models. DR and FA protect against renal I/IR, whereas CE could not.

Maternal food quantity affects offspring feeding rate in Daphnia magna

Maternal effects have wide-ranging effects on life-history traits. Here, using the crustacean Daphnia magna, we document a new effect: maternal food quantity affects offspring feeding rate, with low quantities of food triggering mothers to produce slow-feeding offspring. Such a change in the rate of resource acquisition has broad implications for population growth or dynamics and for interactions with, for instance, predators and parasites. This maternal effect can also explain the previously puzzling situation that the offspring of well-fed mothers, despite being smaller, grow and reproduce better than the offspring of food-starved mothers. As an additional source of variation in resource acquisition, this maternal effect may also influence relationships between life-history traits, i.e. trade-offs, and thus constraints on adaptation. Maternal nutrition has long-lasting effects on health and particularly diet-related traits in humans; finding an effect of maternal nutrition on offspring feeding rate in Daphnia highlights the utility of this organism as a powerful experimental model for exploring the relationship between maternal diet and offspring fitness.

Ageing and Caloric Restriction in a Marine Planktonic Copepod

Planktonic copepods are a key group in the marine pelagic ecosystem, linking primary production with upper trophic levels. Their abundance and population dynamics are constrained by the life history tradeoffs associated with resource availability, reproduction and predation pressure. The tradeoffs associated with the ageing process and its underlying biological mechanisms are, however, poorly known. Our study shows that ageing in copepods involves a deterioration of their vital rates and a rise in mortality associated with an increase in oxidative damage (lipid peroxidation); the activity of the cell-repair enzymatic machinery also increases with age. This increase in oxidative damage is associated with an increase in the relative content of the fatty acid 22:6(n-3), an essential component of cell membranes that increases their susceptibility to peroxidation. Moreover, we show that caloric (food) restriction in marine copepods reduces their age-specific mortality rates, and extends the lifespan of females and their reproductive period. Given the overall low production of the oceans, this can be a strategy, at least in certain copepod species, to enhance their chances to reproduce in a nutritionally dilute, temporally and spatially patchy environment.

Regulation of mitochondrial biogenesis through TFAM-mitochondrial DNA interactions: Useful insights from aging and calorie restriction studies

Mitochondrial biogenesis is regulated to adapt mitochondrial population to cell energy demands. Mitochondrial transcription factor A (TFAM) performs several functions for mtDNA and interactions between TFAM and mtDNA participate to regulation of mitochondrial biogenesis. Such interactions are modulated through different mechanisms: regulation of TFAM expression and turnover, modulation of TFAM binding activity to mtDNA through post-translational modifications and differential affinity of TFAM, occurrence of TFAM sliding on mtDNA filaments and of cooperative binding among TFAM molecules, modulation of protein-protein interactions. The tissue-specific regulation of mitochondrial biogenesis in aging and calorie restriction (CR) highlights the relevance of modulation of TFAM-mtDNA interactions.

Acacetin 7-O-α-l-rhamnopyranosyl (1-2) β-D-xylopyranoside Elicits Life-span Extension and Stress Resistance in Caenorhabditis elegans

The advancements in the field of gerontology have unraveled the signaling pathways that regulate life span, suggesting that it might be feasible to modulate aging. To this end, we isolated a novel phytomolecule Acacetin 7-O-α-l-rhamnopyranosyl (1-2) β-D-xylopyranoside (ARX) from Premna integrifolia and evaluated its antiaging effects in Caenorhabditis elegans The spectral data analysis revealed the occurrence of a new compound ARX. Out of the three tested pharmacological doses of ARX, viz. 5, 25, and 50 µM, the 25-µM dose was able to extend life span in C. elegans by more than 39%. The present study suggests that ARX affects bacterial metabolism, which in turn leads to dietary restriction (DR)-like effects in the worms. The effect of ARX on worms with mutations (mev-1, eat-2, sir-2.1, skn-1, daf-16, and hsf-1) indicates that ARX-mediated life-span extension involves mechanisms associated with DR and maintenance of cellular redox homeostasis. This study is the first time report on longevity-promoting activity of ARX in C. elegans mediated by stress and DR-regulating genes. This novel phytomolecule can contribute in designing therapeutics for managing aging and age-related diseases.

AMPK Protects Leukemia-Initiating Cells in Myeloid Leukemias from Metabolic Stress in the Bone Marrow

How cancer cells adapt to metabolically adverse conditions in patients and strive to proliferate is a fundamental question in cancer biology. Here we show that AMP-activated protein kinase (AMPK), a metabolic checkpoint kinase, confers metabolic stress resistance to leukemia-initiating cells (LICs) and promotes leukemogenesis. Upon dietary restriction, MLL-AF9-induced murine acute myeloid leukemia (AML) activated AMPK and maintained leukemogenic potential. AMPK deletion significantly delayed leukemogenesis and depleted LICs by reducing the expression of glucose transporter 1 (Glut1), compromising glucose flux, and increasing oxidative stress and DNA damage. LICs were particularly dependent on AMPK to suppress oxidative stress in the hypoglycemic bone marrow environment. Strikingly, AMPK inhibition synergized with physiological metabolic stress caused by dietary restriction and profoundly suppressed leukemogenesis. Our results indicate that AMPK protects LICs from metabolic stress and that combining AMPK inhibition with physiological metabolic stress potently suppresses AML by inducing oxidative stress and DNA damage.

Mitochondrial function in ageing: coordination with signalling and transcriptional pathways

Mitochondrial dysfunction entailing decreased energy-transducing capacity and perturbed redox homeostasis is an early and sometimes initiating event in ageing and age-related disorders involving tissues with high metabolic rate such as brain, liver and heart. In the central nervous system (CNS), recent findings from our and other groups suggest that the mitochondrion-centred hypometabolism is a key feature of ageing brains and Alzheimer's disease. This hypometabolic state is manifested by lowered neuronal glucose uptake, metabolic shift in the astrocytes, and alternations in mitochondrial tricarboxylic acid cycle function. Similarly, in liver and adipose tissue, mitochondrial capacity around glucose and fatty acid metabolism and thermogenesis is found to decline with age and is implicated in age-related metabolic disorders such as obesity and type 2 diabetes mellitus. These mitochondrion-related disorders in peripheral tissues can impact on brain functions through metabolic, hormonal and inflammatory signals. At the cellular level, studies in CNS and non-CNS tissues support the notion that instead of being viewed as autonomous organelles, mitochondria are part of a dynamic network with close interactions with other cellular components through energy- or redox-sensitive cytosolic kinase signalling and transcriptional pathways. Hence, it would be critical to further understand the molecular mechanisms involved in the communication between mitochondria and the rest of the cell. Therapeutic strategies that effectively preserves or improve mitochondrial function by targeting key component of these signalling cascades could represent a novel direction for numerous mitochondrion-implicated, age-related disorders.

What is hormesis and its relevance to healthy aging and longevity?

This paper provides a broad overview of hormesis, a specific type of biphasic dose response, its historical and scientific foundations as well as its biomedical applications, especially with respect to aging. Hormesis is a fundamental component of adaptability, neutralizing many endogenous and environmental challenges by toxic agents, thereby enhancing survival. Hormesis is highly conserved, broadly generalizable, and pleiotrophic, being independent of biological model, endpoint measured, inducing agent, level of biological organization and mechanism. The low dose stimulatory hormetic response has specific characteristics which defines both the quantitative features of biological plasticity and the potential for maximum biological performance, thereby estimating the limits to which numerous medical and pharmacological interventions may affect humans. The substantial degrading of some hormetic processes in the aged may profoundly reduce the capacity to respond effectively to numerous environmental/ischemic and other stressors leading to compromised health, disease and, ultimately, defining the bounds of longevity.

The expression characteristics of mt-ND2 gene in chicken

Subunit 2 of NADH dehydrogenase (ND2) is encoded by the mt-ND2 gene and plays a critical role in controlling the production of the mitochondrial reactive oxygen species. Our study focused on exploring the mt-ND2 tissue expression patterns and the effects of energy restriction and dietary fat (linseed oil, corn oil, sesame oil or lard) level (2.5% and 5%) on its expression in chicken. The results showed that mt-ND2 gene was expressed in the 15 tissues of hybrid chickens with the highest level in heart and lowest level in pancreas tissue; 30% energy restriction did not significantly affect mt-ND2 mRNA level in chicken liver tissue. Both the mt-ND2 mRNA levels in chicken pectoralis (p < 0.05) and hepatic tissues (p < 0.05) at 42 d-old were affected by the type of dietary fats in 5% level, while not in abdominal fat tissues. The expression of mt-ND2 in hepatic tissues was down-regulated with chicken age (p < 0.01). The interactive effect of dietary fat types with chicken age (p < 0.05) was significant on mt-ND2 mRNA level. The study demonstrated that mt-ND2 gene was extensively expressed in tissues, and the expression was affected by dietary fat types and chicken age.

Pregnancy-associated plasma protein-A deficiency improves survival of mice on a high fat diet

Obesity is on the rise in westernized countries, and visceral obesity in particular is associated with enhanced risk of developing metabolic disease and accelerated aging. Various dietary restriction regimens have been shown to extend healthy lifespan in a variety of species. However, identification of alternative approaches that could be more acceptable to humans is actively being pursued. We have shown previously that mice deficient in pregnancy-associated plasma protein-A (PAPP-A) have an extended healthy lifespan on a regular chow diet. In this study, we determined the lifespan of PAPP-A knock-out (KO) and wild-type (WT) littermates fed a high fat diet (HFD) starting at 12 months of age. PAPP-A KO and WT mice had equivalent weight gain as measured over 25 weeks on HFD. However, PAPP-A KO mice on HFD had a significant increase in lifespan (P=0.018). Body composition and tissue pathology were assessed in a separate cohort of mice after 30 weeks on HFD. Percent body fat was equivalent in the two groups. However, there was a decrease in visceral fat depot weights and an increase in serum adiponectin levels in PAPP-A KO compared to WT mice. Major pathological differences were seen in kidney, heart and testes, with PAPP-A KO mice having little, if any, evidence of inflammation, mineralization, or degeneration in these tissues compared to WT mice. Thus, PAPP-A is a novel drug target with the potential to promote healthy longevity without a need for dietary restriction.

The effects of graded levels of calorie restriction: IV. Non-linear change in behavioural phenotype of mice in response to short-term calorie restriction

Animals have to adjust their activities when faced with caloric restriction (CR) to deal with reduced energy intake. If CR is pronounced, allostasis can push individuals into alternate physiological states which can result in important health benefits across a wide range of taxa. Here we developed a new approach to determine the changes in behavioural phenotype associated with different levels of CR. We exposed C57BL/6 male mice to graded CR (from 0 to 40%) for three months and defined their behavioural phenotype using hidden Markov models of their movement and body temperature. All 40% CR mice exhibited a state-shift in behavioural phenotype and only some exposed to 30% CR did. We show for the first time that mice changed their activity characteristics rather than changed their activities. This new phenotyping approach provides an avenue to determine the mechanisms linking CR to healthspan.

Caloric restriction increases ratio of estrogen to androgen receptors expression in murine ovaries--potential therapeutic implications

Both estrogens and androgens are involved in the development and normal functioning of the ovaries. It is also known that ovarian function is regulated by diet. The goal of this study was to estimate the expression of sex hormone receptors in ovaries of mice that were on a 9-month caloric restriction (alternate-day feeding) as compared to normal control animals fed ad libitum. We found that prolonged caloric restriction in mouse ovaries led to increased expression of estrogen receptors (ERs) but did not affect expression of the androgen receptor (AR). This increase in ER:AR ration as result of caloric restriction may lead to higher sensitivity to estrogens and upon return to normal diet may increase ovulation. Thus our observation shed more light on a role of beneficial effect of calorie restriction on female reproduction.

Sex-specific effects of protein and carbohydrate intake on reproduction but not lifespan in Drosophila melanogaster

Modest dietary restriction extends lifespan (LS) in a diverse range of taxa and typically has a larger effect in females than males. Traditionally, this has been attributed to a stronger trade-off between LS and reproduction in females than in males that is mediated by the intake of calories. Recent studies, however, suggest that it is the intake of specific nutrients that extends LS and mediates this trade-off. Here, we used the geometric framework (GF) to examine the sex-specific effects of protein (P) and carbohydrate (C) intake on LS and reproduction in Drosophila melanogaster. We found that LS was maximized at a high intake of C and a low intake of P in both sexes, whereas nutrient intake had divergent effects on reproduction. Male offspring production rate and LS were maximized at the same intake of nutrients, whereas female egg production rate was maximized at a high intake of diets with a P:C ratio of 1:2. This resulted in larger differences in nutrient-dependent optima for LS and reproduction in females than in males, as well as an optimal intake of nutrients for lifetime reproduction that differed between the sexes. Under dietary choice, the sexes followed similar feeding trajectories regulated around a P:C ratio of 1:4. Consequently, neither sex reached their nutritional optimum for lifetime reproduction, suggesting intralocus sexual conflict over nutrient optimization. Our study shows clear sex differences in the nutritional requirements of reproduction in D. melanogaster and joins the growing list of studies challenging the role of caloric restriction in extending LS.

Being cool: how body temperature influences ageing and longevity

Temperature is a basic and essential property of any physical system, including living systems. Even modest variations in temperature can have profound effects on organisms, and it has long been thought that as metabolism increases at higher temperatures so should rates of ageing. Here, we review the literature on how temperature affects longevity, ageing and life history traits. From poikilotherms to homeotherms, there is a clear trend for lower temperature being associated with longer lifespans both in wild populations and in laboratory conditions. Many life-extending manipulations in rodents, such as caloric restriction, also decrease core body temperature. Nonetheless, an inverse relationship between temperature and lifespan can be obscured or reversed, especially when the range of body temperatures is small as in homeotherms. An example is observed in humans: women appear to have a slightly higher body temperature and yet live longer than men. The mechanisms involved in the relationship between temperature and longevity also appear to be less direct than once thought with neuroendocrine processes possibly mediating complex physiological responses to temperature changes. Lastly, we discuss species differences in longevity in mammals and how this relates to body temperature and argue that the low temperature of the long-lived naked mole-rat possibly contributes to its exceptional longevity.

Macronutrients and caloric intake in health and longevity

Both lifespan and healthspan are influenced by nutrition, with nutritional interventions proving to be robust across a wide range of species. However, the relationship between nutrition, health and aging is still not fully understood. Caloric restriction is the most studied dietary intervention known to extend life in many organisms, but recently the balance of macronutrients has been shown to play a critical role. In this review, we discuss the current understanding regarding the impact of calories and macronutrient balance in mammalian health and longevity, and highlight the key nutrient-sensing pathways that mediate the effects of nutrition on health and ageing.

Translational geroscience: emphasizing function to achieve optimal longevity

Among individuals, biological aging leads to cellular and organismal dysfunction and an increased risk of chronic degenerative diseases and disability. This sequence of events in combination with the projected increases in the number of older adults will result in a worldwide healthcare burden with dire consequences. Superimposed on this setting are the adults now reaching traditional retirement ages--the baby boomers--a group that wishes to remain active, productive and physically and cognitively fit as they grow older. Together, these conditions are producing an unprecedented demand for increased healthspan or what might be termed “optimal longevity”—to live long, but well. To meet this demand, investigators with interests in the biological aspects of aging from model organisms to human epidemiology (population aging) must work together within an interactive process that we describe as translational geroscience. An essential goal of this new investigational platform should be the optimization and preservation of physiological function throughout the lifespan, including integrative physical and cognitive function, which would serve to increase healthspan, compress morbidity and disability into a shorter period of late-life, and help achieve optimal longevity. To most effectively utilize this new approach, we must rethink how investigators and administrators working at different levels of the translational research continuum communicate and collaborate with each other, how best to train the next generation of scientists in this new field, and how contemporary biological-biomedical aging research should be organized and funded.

Repeated exposure to stressful conditions can have beneficial effects on survival

Repeated exposure to stressful circumstances is generally thought to be associated with increased pathology and reduced longevity. However, growing lines of evidence suggest that the effects of environmental stressors on survival and longevity depend on a multitude of factors and, under some circumstances, might be positive rather than negative. Here, using the zebra finch (Taeniopygia guttata), we show that repeated exposure to stressful conditions (i.e. unpredictable food availability), which induced no changes in body mass, was associated with a decrease in mortality rate and an increase in the age of death. As expected, the treated birds responded to the unpredictable food supply by increasing baseline glucocorticoid stress hormone secretion and there were no signs of habituation of this hormonal response to the treatment across time. Importantly, and consistent with previous literature, the magnitude of hormone increase induced by the treatment was significant, but relatively mild, since the baseline glucocorticoid concentrations in the treated birds were substantially lower than the peak levels that occur during an acute stress response in this species. Taken together, these data demonstrate that protracted exposure to relatively mild stressful circumstances can have beneficial lifespan effects.

Dietary Protein to Carbohydrate Ratio and Caloric Restriction: Comparing Metabolic Outcomes in Mice

Both caloric restriction (CR) and low-protein, high-carbohydrate (LPHC) ad-libitum-fed diets increase lifespan and improve metabolic parameters such as insulin, glucose, and blood lipids. Severe CR, however, is unsustainable for most people; therefore, it is important to determine whether manipulating macronutrient ratios in ad-libitum-fed conditions can generate similar health outcomes. We present the results of a short-term (8 week) dietary manipulation on metabolic outcomes in mice. We compared three diets varying in protein to carbohydrate ratio under both CR and ad libitum conditions. Ad libitum LPHC diets delivered similar benefits to CR in terms of levels of insulin, glucose, lipids, and HOMA, despite increased energy intake. CR on LPHC diets did not provide additional benefits relative to ad libitum LPHC. We show that LPHC diets under ad-libitum-fed conditions generate the metabolic benefits of CR without a 40% reduction in total caloric intake.

The effects of energy intake of four different feeding patterns in rats

Energy intake can affect the metabolism. But it is not very clear that how and to what degree the metabolism can be changed by energy intake quantity and change. Here we applied four feeding patterns in male Sprague-Dawley rats--normal ad libitum diet (NFal), high-fat diet (HFal), caloric restriction (CR) after HFal (HFal-NFcr), and refeeding from CR to ad libitum (HFal-NFcr-NFal). Food intake and body weight, along with fat mass, insulin sensitivity, fasting plasma insulin, and glucose level were used to calculate the energy efficiency and compared the quantitative effects of energy intake. Energy intake changed little in NFal or HFal group; while it changed greatly and suddenly in HFal-NFcr or HFal-NFcr-NFal group. All the parameters we detected were different between these four feeding patterns. Excess of energy intake from high-fat diet induced adverse outcomes with low energy efficiency. CR reversed the impairment of high-fat diet with very high energy efficiency in a short period. However, dramatic response with high energy efficiency induced by recovery to feeding ad libitum after CR, which was possible harmful to health. In conclusion, energy intake quantity and change are key determinants of metabolism. Different energy intake quantity and change affect body weight, white adipose tissue weight, insulin sensitivity, etc. at different degrees and speeds because of different energy efficiency.