The effects of graded levels of calorie restriction: II. Impact of short term calorie and protein restriction on circulating hormone levels, glucose homeostasis and oxidative stress in male C57BL/6 mice

Benefits of calorie restriction in mice are mediated via energy imbalance, not absolute energy or protein intake

Caloric restriction (CR) results in reduced energy and protein intake, raising questions about protein restriction's contribution to CR longevity benefits. We kept ad libitum (AL)-fed male C57BL/6J mice at 27°C (AL27) and pair-fed (PF) mice at 22°C (22(PF27)). The 22(PF27) group was fed to match AL27 while restricted for calories due to cold-induced metabolism. The 22(PF27) mice had significantly lower body weight, lean mass, fat mass, leptin, IGF-1, and TNF-α levels than AL27 mice (p<0.001 for all). Manipulations over ~11 weeks resulted in significant differences in body temperature, physical activity, and expression of key genes linked to hunger in the hypothalamus. Survival was significantly greater in 22(PF27) compared to AL27 overall (p<0.001). CR in the context of equivalent energy and protein intake resulted in hormonal, metabolic, and physiological benefits and extended longevity. Hence, energy imbalance, rather than low energy or protein intake per se, mediates the benefits of CR.

Does diet influence aging? Evidence from animal studies

Nutrition profoundly influences the risk for many age-related diseases. Whether nutrition influences human aging biology directly is less clear. Studies in different animal species indicate that reducing food intake ("caloric restriction" [CR]) can increase lifespan and delay the onset of diseases and the biological hallmarks of aging. Obesity has been described as "accelerated aging" and therefore the lifespan and health benefits generated by CR in both aging and obesity may occur via similar mechanisms. Beyond calorie intake, studies based on nutritional geometry have shown that protein intake and the interaction between dietary protein and carbohydrates influence age-related health and lifespan. Studies where animals are calorically restricted by providing free access to diluted diets have had less impact on lifespan than those studies where animals are given a reduced aliquot of food each day and are fasting between meals. This has drawn attention to the role of fasting in health and aging, and exploration of the health effects of various fasting regimes. Although definitive human clinical trials of nutrition and aging would need to be unfeasibly long and unrealistically controlled, there is good evidence from animal experiments that some nutritional interventions based on CR, manipulating dietary macronutrients, and fasting can influence aging biology and lifespan.

Antiaging Strategies and Remedies: A Landscape of Research Progress and Promise

Aging is typified by a gradual loss of physiological fitness and accumulation of cellular damage, leading to deteriorated functions and enhanced vulnerability to diseases. Antiaging research has a long history throughout civilization, with many efforts put forth to understand and prevent the effects of aging. Multiple strategies aiming to promote healthy aging and extend the lifespan have been developed including lifestyle adjustments, medical treatments, and social programs. A multitude of antiaging medicines and remedies have also been explored. Here, we use data from the CAS Content Collection to analyze the publication landscape of recent research related to antiaging strategies and treatments. We review the recent advances and delineate trends in research headway of antiaging knowledge and practice across time, geography, and development pipelines. We further assess the state-of-the-art antiaging approaches and explore their correlations with age-related diseases. The landscape of antiaging drugs has been outlined and explored. Well-recognized and novel, currently evaluated antiaging agents have also been summarized. Finally, we review clinical applications of antiaging products with their development pipelines. The objective of this review is to summarize current knowledge on preventive strategies and treatment remedies in the field of aging, to outline challenges and evaluate growth opportunities, in order to further efforts to solve the problems that remain.

Major urinary protein (Mup) gene family deletion drives sex-specific alterations in the house-mouse gut microbiota

The gut microbiota is shaped by host metabolism. In house mice (Mus musculus), major urinary protein (MUP) pheromone production represents a considerable energy investment, particularly in sexually mature males. Deletion of the Mup gene family shifts mouse metabolism toward an anabolic state, marked by lipogenesis, lipid accumulation, and body mass increases. Given the metabolic implications of MUPs, they may also influence the gut microbiota. Here, we investigated the effect of a deletion of the Mup gene family on the gut microbiota of sexually mature mice. Shotgun metagenomics revealed distinct taxonomic and functional profiles between wild-type and knockout males but not females. Deletion of the Mup gene cluster significantly reduced diversity in microbial families and functions in male mice. Additionally, a species of Ruminococcaceae and several microbial functions, such as transporters involved in vitamin B5 acquisition, were significantly depleted in the microbiota of Mup knockout males. Altogether, these results show that MUPs significantly affect the gut microbiota of house mouse in a sex-specific manner.IMPORTANCEThe community of microorganisms that inhabits the gastrointestinal tract can have profound effects on host phenotypes. The gut microbiota is in turn shaped by host genes, including those involved with host metabolism. In adult male house mice, expression of the major urinary protein (Mup) gene cluster represents a substantial energy investment, and deletion of the Mup gene family leads to fat accumulation and weight gain in males. We show that deleting Mup genes also alters the gut microbiota of male, but not female, mice in terms of both taxonomic and functional compositions. Male mice without Mup genes harbored fewer gut bacterial families and reduced abundance of a species of Ruminococcaceae, a family that has been previously shown to reduce obesity risk. Studying the impact of the Mup gene family on the gut microbiota has the potential to reveal the ways in which these genes affect host phenotypes.

Every-other day (EOD) feeding regime decreases oxidative stress and inflammatory cascade in mouse liver: The immunohistochemical study

INTRODUCTION

Positive effects of calorie restrictions (CR) and EOD include decreased body weight, prolonged life span, but also changes in metabolism of the liver. In present paper our aim was to examine antioxidative enzymes: Catalase (CAT) and Manganese superoxidative dismutase (MnSOD, SOD2) and Glutathione peroxidase 4 (Gpx-4) in connection to caspase-3 and inflammatory mediators (IL-1β and TNF- α) in EOD liver tissue in comparison to control mice.

METHODS

After 9 months of EOD treatment male mouse liver tissue was harvested and prepared for analysis. Protein semi-quantitative estimation and cellular immunolocalization was performed for CAT, SOD2, Gpx-4, caspase-3, IL-1β and TNF- α in liver tissue of mice fed every-other day in comparison to control (AL fed) animals.

RESULTS

After prolonged EOD feeding in mice we observed decreased level of SOD2 and Gpx-4, decreased caspase-3, IL-1β and TNF-α expression in liver tissue on protein level measured by semi-quantitative DAB staining intensity.

CONCLUSION

For the first time we showed immunolocalization of major antioxidative enzymes (CAT, SOD2, Gpx-4) in liver tissue after DR. Decrease of two major antioxidant enzymes combined with decrease of apoptotic marker and inflammatory factors indicate decrease in oxidative stress as the result of fast in EOD feeding regime.

The Effects of Graded Levels of Calorie Restriction: XX. Impact of Long-Term Graded Calorie Restriction on Survival and Body Mass Dynamics in Male C57BL/6J Mice

Calorie restriction (CR) typically promotes a reduction in body mass, which correlates with increased lifespan. We evaluated the overall changes in survival, body mass dynamics, and body composition following long-term graded CR (580 days/19 months) in male C57BL/6J mice. Control mice (0% restriction) were fed ad libitum in the dark phase only (12-hour ad libitum [12AL]). CR groups were restricted by 10%-40% of their baseline food intake (10CR, 20CR, 30CR, and 40CR). Body mass was recorded daily, and body composition was measured at 8 time points. At 728 days/24 months, all surviving mice were culled. A gradation in survival rate over the CR groups was found. The pattern of body mass loss differed over the graded CR groups. Whereas the lower CR groups rapidly resumed an energy balance with no significant loss of fat or fat-free mass, changes in the 30 and 40CR groups were attributed to higher fat-free mass loss and protection of fat mass. Day-to-day changes in body mass were less variable under CR than for the 12AL group. There was no indication that body mass was influenced by external factors. Partial autocorrelation analysis examined the relationship between daily changes in body masses. A negative correlation between mass on Day 0 and Day +1 declined with age in the 12AL but not the CR groups. A reduction in the correlation with age suggested body mass homeostasis is a marker of aging that declines at the end of life and is protected by CR.

Caloric Restriction: A Novel Conditioning Strategy to Improve the Survival of Ischemically Challenged Musculocutaneous Random Pattern Flaps

Caloric restriction (CR) is a cost-effective and easy-to-perform approach to counteracting surgical stress. The present study therefore evaluates the tissue-protective effects of a 30% CR in musculocutaneous flaps undergoing ischemia. For this purpose, a well-established murine dorsal skinfold chamber model, in combination with random pattern musculocutaneous flaps, was used. C57BL/6N mice were divided at random into a CR group (n = 8) and a control group with unrestricted access to standard chow (n = 8). The CR animals were subjected to a 30% reduction in caloric intake for 10 days before flap elevation. Intravital fluorescence microscopy was carried out on days 1, 3, 5, 7 and 10 after flap elevation to assess the nutritive blood perfusion, angiogenesis and flap necrosis. Subsequently, the flap tissue was harvested for additional histological and immunohistochemical analyses. The CR-treated animals exhibited a significantly higher functional capillary density and more newly formed microvessels within the flap tissue when compared to the controls; this was associated with a significantly higher flap survival rate. Immunohistochemical analyses showed a decreased invasion of myeloperoxidase-positive neutrophilic granulocytes into the flap tissue of the CR-treated mice. Moreover, the detection of cleaved caspase-3 revealed fewer cells undergoing apoptosis in the transition zone between the vital and necrotic tissue in the flaps of the CR-treated mice. These results demonstrate that a CR of 30% effectively prevents flap necrosis by maintaining microperfusion on a capillary level and inhibiting inflammation under ischemic stress. Hence, CR represents a promising novel conditioning strategy for improving the survival of musculocutaneous flaps with random pattern perfusion.

On antigen-specific signals, immune class regulation and energetics: Report III from the workshops on foundational concepts of immune regulation

This is a report from a one-week workshop held in Athens, Greece in July of 2022. The workshop aimed to identify emerging concepts relevant to the fundamentals of immune regulation and areas for future research. Theories of immune regulation emphasize the role of T cell help or co-stimulation (signal 2). The workshop participants considered how new data on the characteristics of agonist antigens, the role of the antigen receptor signals (signal 1) in driving fate decisions, the effect of energetics on immunity and a better understanding of class-control in the immune response, may impact theories of immune regulation. These ideas were discussed in the context of tumour immunology, autoimmunity, pregnancy and transplantation. Here we present the discussions as a narrative of different viewpoints to allow the reader to join the conversation. These discussions highlight the evolving understanding of the nature of specific antigen recognition and how both antigen-specific and non-specific mechanisms impact immune responses.

Major urinary protein (Mup) gene family deletion drives sex-specific alterations on the house mouse gut microbiota

The gut microbiota is shaped by host metabolism. In house mice (Mus musculus), major urinary protein (MUP) pheromone production represents a considerable energy investment, particularly in sexually mature males. Deletion of the Mup gene family shifts mouse metabolism towards an anabolic state, marked by lipogenesis, lipid accumulation, and body mass increases. Given the metabolic implications of MUPs, they may also influence the gut microbiota. Here, we investigated the effect of deletion of the Mup gene family on the gut microbiota of sexually mature mice. Shotgun metagenomics revealed distinct taxonomic and functional profiles between wildtype and knockout males, but not females. Deletion of the Mup gene cluster significantly reduced diversity in microbial families and functions in male mice. Additionally, specific taxa of the Ruminococcaceae family, which is associated with gut health and reduced risk of developing metabolic syndrome, and several microbial functions, such as transporters involved in vitamin B5 acquisition, were significantly depleted in the microbiota of Mup-knockout males. Altogether these results show that major urinary proteins significantly affect the gut microbiota of house mouse in a sex-specific manner.

The Effects of Graded Levels of Calorie Restriction: XIX. Impact of Graded Calorie Restriction on Protein Expression in the Liver

Calorie restriction (CR) extends life span by modulating the mechanisms involved in aging. We quantified the hepatic proteome of male C57BL/6 mice exposed to graded levels of CR (0%-40% CR) for 3 months, and evaluated which signaling pathways were most affected. The metabolic pathways most significantly stimulated by the increase in CR, included the glycolysis/gluconeogenesis pathway, the pentose phosphate pathway, the fatty acid degradation pathway, the valine, leucine, and isoleucine degradation pathway, and the lysine degradation pathway. The metabolism of xenobiotics by cytochrome P450 pathway was activated and feminized by increased CR, while production in major urinary proteins (Mups) was strongly reduced, consistent with a reduced investment in reproduction as predicted by the disposable soma hypothesis. However, we found no evidence of increased somatic protection, and none of the 4 main pathways implied to be linked to the impact of CR on life span (insulin/insulin-like growth factor [IGF-1], nuclear factor-κB [NF-κB], mammalian Target of Rapamycin [mTOR], and sirtuins) as well as pathways in cancer, were significantly changed at the protein level in relation to the increase in CR level. This was despite previous work at the transcriptome level in the same individuals indicating such changes. On the other hand, we found Aldh2, Aldh3a2, and Aldh9a1 in carnitine biosynthesis and Acsl5 in carnitine shuttle system were up-regulated by increased CR, which are consistent with our previous work on metabolome of the same individuals. Overall, the patterns of protein expression were more consistent with a "clean cupboards" than a "disposable soma" interpretation.

The interplay between nonalcoholic fatty liver disease and atherosclerotic cardiovascular disease

Therapeutic approaches that lower circulating low-density lipoprotein (LDL)-cholesterol significantly reduced the burden of cardiovascular disease over the last decades. However, the persistent rise in the obesity epidemic is beginning to reverse this decline. Alongside obesity, the incidence of nonalcoholic fatty liver disease (NAFLD) has substantially increased in the last three decades. Currently, approximately one third of world population is affected by NAFLD. Notably, the presence of NAFLD and particularly its more severe form, nonalcoholic steatohepatitis (NASH), serves as an independent risk factor for atherosclerotic cardiovascular disease (ASCVD), thus, raising interest in the relationship between these two diseases. Importantly, ASCVD is the major cause of death in patients with NASH independent of traditional risk factors. Nevertheless, the pathophysiology linking NAFLD/NASH with ASCVD remains poorly understood. While dyslipidemia is a common risk factor underlying both diseases, therapies that lower circulating LDL-cholesterol are largely ineffective against NASH. While there are no approved pharmacological therapies for NASH, some of the most advanced drug candidates exacerbate atherogenic dyslipidemia, raising concerns regarding their adverse cardiovascular consequences. In this review, we address current gaps in our understanding of the mechanisms linking NAFLD/NASH and ASCVD, explore strategies to simultaneously model these diseases, evaluate emerging biomarkers that may be useful to diagnose the presence of both diseases, and discuss investigational approaches and ongoing clinical trials that potentially target both diseases.

Effect of dietary protein content shift on aging in elderly rats by comprehensive quantitative score and metabolomics analysis

In the protein nutrition strategy of middle-aged and elderly people, some believe that low protein is good for health, while others believe high protein is good for health. Facing the contradictory situation, the following hypothesis is proposed. There is a process of change from lower to higher ratio of protein nutritional requirements that are good for health in the human body after about 50 years of age, and the age at which the switch occurs is around 65 years of age. Hence, in this study, 50, 25-month-old male rats were randomly divided into five groups: Control (basal diet), LP (low-protein diet with a 30% decrease in protein content compared to the basal diet), HP (high-protein diet with a 30% increase in protein content compared to the basal diet), Model 1 (switched from LP to HP feed at week 4), and Model 2 (switched from LP to HP feed at week 7). After a total of 10 weeks intervention, the liver and serum samples were examined for aging-related indicators, and a newly comprehensive quantitative score was generated using principal component analysis (PCA). The effects of the five protein nutritional modalities were quantified in descending order: Model 1 &gt; HP &gt; LP &gt; Control &gt; Model 2. Furthermore, the differential metabolites in serum and feces were determined by orthogonal partial least squares discriminant analysis, and 15 differential metabolites, significantly associated with protein intake, were identified by Spearman’s correlation analysis (p &lt; 0.05). Among the fecal metabolites, 10 were positively correlated and 3 were negatively correlated. In the serum, tyrosine and lactate levels were positively correlated, and acetate levels were negatively correlated. MetaboAnalyst analysis identified that the metabolic pathways influenced by protein intake were mainly related to amino acid and carbohydrate metabolism. The results of metabolomic analysis elucidate the mechanisms underlying the preceding effects to some degree. These efforts not only contribute to a unified protein nutrition strategy but also positively impact the building of a wiser approach to protein nutrition, thereby helping middle-aged and older populations achieve healthy aging.

Effects of Different Calorie Restriction Protocols on Oxidative Stress Parameters in a Transgenic Mouse Model of Breast Cancer

Aging and diseases related to aging, such as cancer, have been linked to oxidative stress. On the other hand, calorie restriction (CR) is one of the most effective interventions to slow down aging and prevent a variety of diseases such as cancer in preclinical models. CR has also been reported to modify oxidative stress. The aim of this study was to investigate the effects of different CR protocols and aging on oxidative stress parameters in the MMTV-TGF-α breast cancer mouse model in a cross-sectional study. Female mice were randomly enrolled in three groups: ad libitum (AL), chronic calorie restriction (CCR, 15% CR) or intermittent calorie restriction (ICR, three weeks AL followed by one week 60% CR in cyclic periods) starting at the age of 10 weeks until 81/82 weeks of age. Liver samples were analyzed for malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GSH-Px) levels. At week 49/50, the GSH level increased significantly in the CCR group compared to the AL and ICR-R groups which had higher mammary tumor (MT) incidence rates. Additionally, liver MDA levels in ICR groups were significantly increased, while aging led to decreased CAT and SOD activities in all CR groups. The application of different CR protocols did not have any significant effect on MDA, CAT, and SOD parameters in the liver at week 81/82. These results suggest that although GSH may interfere with MT development at the systemic level, many of the oxidative stress parameters may have more local effects on tumor development than the systemic effects.

Temporal Dynamics of the Intestinal Microbiome Following Short-Term Dietary Restriction

Short-term dietary restriction has been proposed as an intriguing pre-operative conditioning strategy designed to attenuate the surgical stress response and improve outcomes. However, it is unclear how this nutritional intervention influences the microbiome, which is known to modulate the systemic condition. Healthy individuals were recruited to participate in a four-day, 70% protein-restricted, 30% calorie-restricted diet, and stool samples were collected at baseline, after the restricted diet, and after resuming normal food intake. Taxonomy and functional pathway analysis was performed via shotgun metagenomic sequencing, prevalence filtering, and differential abundance analysis. High prevalence species were altered by the dietary intervention but quickly returned to baseline after restarting a regular diet. Composition and functional changes after the restricted diet included the decreased relative abundance of commensal bacteria and a catabolic phenotype. Notable species changes included Faecalibacterium prausnitzii and Roseburia intestinalis, which are major butyrate producers within the colon and are characteristically decreased in many disease states. The macronutrient components of the diet might have influenced these changes. We conclude that short-term dietary restriction modulates the ecology of the gut microbiome, with this modulation being characterized by a relative dysbiosis.

The effects of graded levels of calorie restriction XVIII: tissue specific changes in cell size and number in response to calorie restriction

Calorie restriction (CR) without malnutrition increases the health- and lifespan of diverse taxa. The mechanism(s) behind CR are debated but may be directly linked to body composition changes that maintain energy balance. During a deficit, energy is primarily obtained from white adipose tissue (WAT; utilized) whilst other tissues remain unchanged (protected) or grow (invested) relative to body mass. The changes in mass of 6 tissues from 48 male C57BL/6 mice following 3-months graded (10, 20, 30, or 40%) CR or fed ad libitum for 12 or 24hr a day were related to cell size (hypo/hypertrophy) and/or number (hypo/hyperplasia). Tissues studied were: retroperitoneal and subcutaneous WAT, brown adipose tissue (BAT) (utilized); lungs (protected), and stomach and caecum (invested). Methodology was based on number of nuclei/ tissue equalling the number of cells. Extracted DNA was quantified and used to estimate cell numbers (Total DNA/DNA per diploid nucleus) and size (Tissue mass/nuclei number). WAT utilization was caused solely by hypotrophy whereas BAT utilization resulted from reduced cell number and size. WAT cell size positively correlated with circulating hormones related to energy balance and BAT cell number and size positively correlated with body temperature. No changes were found in the lungs, consistent with their protected status, whereas hyperplasia appeared to be the dominant mechanism for invested alimentary-tract tissues. These findings indicate the pattern of change of cell size and number across increasing levels of short-term CR is tissue-specific.

Calorie restriction and calorie dilution have different impacts on body fat, metabolism, behavior, and hypothalamic gene expression

Caloric restriction is a robust intervention to increase lifespan. Giving less food (calorie restriction [CR]) or allowing free access to a diluted diet with indigestible components (calorie dilution [CD]) are two methods to impose restriction. CD does not generate the same lifespan effect as CR. We compare responses of C57BL/6 mice with equivalent levels of CR and CD. The two groups have different responses in fat loss, circulating hormones, and metabolic rate. CR mice are hungrier, as assessed by behavioral assays. Although gene expression of Npy, Agrp, and Pomc do not differ between CR and CD groups, CR mice had a distinctive hypothalamic gene-expression profile with many genes related to starvation upregulated relative to CD. While both result in lower calorie intake, CR and CD are not equivalent procedures. Increased hunger under CR supports the hypothesis that hunger signaling is a key process mediating the benefits of CR.

Regulation of Sexually Dimorphic Expression of Major Urinary Proteins

Male house mice excrete large amounts of protein in their urinary scent marks, mainly composed of Major Urinary Proteins (MUPs), and these lipocalins function as pheromones and pheromone carriers. Here, we review studies on sexually dimorphic MUP expression in house mice, including the proximate mechanisms controlling MUP gene expression and their adaptive functions. Males excrete 2 to 8 times more urinary protein than females, though there is enormous variation in gene expression across loci in both sexes. MUP expression is dynamically regulated depending upon a variety of factors. Males regulate MUP expression according to social status, whereas females do not, and males regulate expression depending upon health and condition. Male-biased MUP expression is regulated by pituitary secretion of growth hormone (GH), which binds receptors in the liver, activating the JAK2-STAT5 signaling pathway, chromatin accessibility, and MUP gene transcription. Pulsatile male GH secretion is feminized by several factors, including caloric restriction, microbiota depletion, and aging, which helps explain condition-dependent MUP expression. If MUP production has sex-specific fitness optima, then this should generate sexual antagonism over allelic expression (intra-locus sexual conflict) selectively favoring sexually dimorphic expression. MUPs influence the sexual attractiveness of male urinary odor and increased urinary protein excretion is correlated with the reproductive success of males but not females. This finding could explain the selective maintenance of sexually dimorphic MUP expression. Producing MUPs entails energetic costs, but increased excretion may reduce the net energetic costs and predation risks from male scent marking as well as prolong the release of chemical signals. MUPs may also provide physiological benefits, including regulating metabolic rate and toxin removal, which may have sex-specific effects on survival. A phylogenetic analysis on the origins of male-biased MUP gene expression in Mus musculus suggests that this sexual dimorphism evolved by increasing male MUP expression rather than reducing female expression.

Molecular mechanisms of dietary restriction promoting health and longevity

Dietary restriction with adequate nutrition is the gold standard for delaying ageing and extending healthspan and lifespan in diverse species, including rodents and non-human primates. In this Review, we discuss the effects of dietary restriction in these mammalian model organisms and discuss accumulating data that suggest that dietary restriction results in many of the same physiological, metabolic and molecular changes responsible for the prevention of multiple ageing-associated diseases in humans. We further discuss how different forms of fasting, protein restriction and specific reductions in the levels of essential amino acids such as methionine and the branched-chain amino acids selectively impact the activity of AKT, FOXO, mTOR, nicotinamide adenine dinucleotide (NAD+), AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21), which are key components of some of the most important nutrient-sensing geroprotective signalling pathways that promote healthy longevity.

Strain-specific metabolic responses to long-term caloric restriction in female ILSXISS recombinant inbred mice

The role that genetic background may play in the responsiveness of organisms to interventions such as caloric restriction (CR) is underappreciated but potentially important. We investigated the impact of genetic background on a suite of metabolic parameters in female recombinant inbred ILSXISS mouse strains previously reported to show divergent lifespan responses to 40% CR (TejJ89-lifespan extension; TejJ48-lifespan unaffected; TejJ114-lifespan shortening). Body mass was reduced across all strains following 10 months of 40% CR, although this loss (relative to ad libitum controls) was greater in TejJ114 relative to the other strains. Gonadal white adipose tissue (gWAT) mass was similarly reduced across all strains following 40% CR, but brown adipose tissue (BAT) mass increased only in strains TejJ89 and TejJ48. Surprisingly, glucose tolerance was improved most notably by CR in TejJ114, while both strains TejJ89 and TejJ114 were hyperinsulinemic following CR relative to their AL controls. We subsequently undertook an unbiased metabolomic approach in gWAT and BAT tissue derived from strains TejJ89 and TejJ114 mice under AL and 40% CR. In gWAT from TejJ89 a significant reduction in several long chain unsaturated fatty acids was observed following 40% CR, but gWAT from TejJ114 appeared relatively unresponsive to CR with far fewer metabolites changing. Phosphatidylethanoloamine lipids within the BAT were typically elevated in TejJ89 following CR, while some phosphatidylglycerol lipids were decreased. However, BAT from strain TejJ114 again appeared unresponsive to CR. These data highlight strain-specific metabolic differences exist in ILSXISS mice following 40% CR. We suggest that precisely how different fat depots respond dynamically to CR may be an important factor in the variable longevity under 40% CR reported in these mice.

The Effects of Graded Levels of Calorie Restriction: XVI. Metabolomic Changes in the Cerebellum Indicate Activation of Hypothalamocerebellar Connections Driven by Hunger Responses

Calorie restriction (CR) remains the most robust intervention to extend life span and improve healthspan. Though the cerebellum is more commonly associated with motor control, it has strong links with the hypothalamus and is thought to be associated with nutritional regulation and adiposity. Using a global mass spectrometry-based metabolomics approach, we identified 756 metabolites that were significantly differentially expressed in the cerebellar region of the brain of C57BL/6J mice, fed graded levels of CR (10, 20, 30, and 40 CR) compared to mice fed ad libitum for 12 hours a day. Pathway enrichment indicated changes in the pathways of adenosine and guanine (which are precursors of DNA production), aromatic amino acids (tyrosine, phenylalanine, and tryptophan) and the sulfur-containing amino acid methionine. We also saw increases in the tricarboxylic acid cycle (TCA) cycle, electron donor, and dopamine and histamine pathways. In particular, changes in l-histidine and homocarnosine correlated positively with the level of CR and food anticipatory activity and negatively with insulin and body temperature. Several metabolic and pathway changes acted against changes seen in age-associated neurodegenerative disorders, including increases in the TCA cycle and reduced l-proline. Carnitine metabolites contributed to discrimination between CR groups, which corroborates previous work in the liver and plasma. These results indicate the conservation of certain aspects of metabolism across tissues with CR. Moreover, this is the first study to indicate CR alters the cerebellar metabolome, and does so in a graded fashion, after only a short period of restriction.

The effects of graded calorie restriction XVII: Multitissue metabolomics reveals synthesis of carnitine and NAD, and tRNA charging as key pathways

The evolutionary context of why caloric restriction (CR) activates physiological mechanisms that slow the process of aging remains unclear. The main goal of this analysis was to identify, using metabolomics, the common pathways that are modulated across multiple tissues (brown adipose tissue, liver, plasma, and brain) to evaluate two alternative evolutionary models: the "disposable soma" and "clean cupboards" ideas. Across the four tissues, we identified more than 10,000 different metabolic features. CR altered the metabolome in a graded fashion. More restriction led to more changes. Most changes, however, were tissue specific, and in some cases, metabolites changed in opposite directions in different tissues. Only 38 common metabolic features responded to restriction in the same way across all four tissues. Fifty percent of the common altered metabolites were carboxylic acids and derivatives, as well as lipids and lipid-like molecules. The top five modulated canonical pathways were l-carnitine biosynthesis, NAD (nicotinamide adenine dinucleotide) biosynthesis from 2-amino-3-carboxymuconate semialdehyde, S-methyl-5'-thioadenosine degradation II, NAD biosynthesis II (from tryptophan), and transfer RNA (tRNA) charging. Although some pathways were modulated in common across tissues, none of these reflected somatic protection, and each tissue invoked its own idiosyncratic modulation of pathways to cope with the reduction in incoming energy. Consequently, this study provides greater support for the clean cupboards hypothesis than the disposable soma interpretation.

Effects of fasting on skeletal muscles and body fat of adult and old C57BL/6J mice

Fasting improves metabolic health, but is also associated with loss of lean body mass. We investigated if old mice are less resistant to fasting-induce muscle wasting than adult mice. We compared changes in skeletal muscles and fat distribution in C57BL/6J mice subjected to 48-hour fasting at adult (6-month old) or old (24-month old) age. Old mice lost less weight (11.9 ± 1.5 vs 16.9 ± 2.8%, p < 0.001) and showed less (p < 0.01) pronounced muscle wasting than adult mice. Extensor digitorum longus (EDL) muscle force decreased only in adult mice after fasting. Serum IGF-1 levels were higher (p < 0.01) and showed greater (p < 0.01) decline in adult mice compared to old mice. Phosphorylation of 4EBP1 was reduced in the gastrocnemius muscles of adult mice only. Energy expenditure was slower in old mice and showed smaller fasting-induced decline than in adult mice when adjusted for variations in physical activity. There was a loss of fat mass in both age groups, but it was more pronounced in adult mice than old mice. Our results suggest that ageing-related decrease in metabolic rate protects old mice from skeletal muscle wasting during fasting.

Very-low-protein diets lead to reduced food intake and weight loss, linked to inhibition of hypothalamic mTOR signaling, in mice

The protein leverage hypothesis predicts that low dietary protein should increase energy intake and cause adiposity. We designed 10 diets varying from 1% to 20% protein combined with either 60% or 20% fat. Contrasting the expectation, very low protein did not cause increased food intake. Although these mice had activated hunger signaling, they ate less food, resulting in decreased body weight and improved glucose tolerance but not increased frailty, even under 60% fat. Moreover, they did not show hyperphagia when returned to a 20% protein diet, which could be mimicked by treatment with rapamycin. Intracerebroventricular injection of AAV-S6K1 significantly blunted the decrease in both food intake and body weight in mice fed 1% protein, an effect not observed with inhibition of eIF2a, TRPML1, and Fgf21 signaling. Hence, the 1% protein diet induced decreased food intake and body weight via a mechanism partially dependent on hypothalamic mTOR signaling.

The effect of calorie intake, fasting, and dietary composition on metabolic health and gut microbiota in mice

Background

Calorie restriction (CR) and intermittent fasting (IF) can promote metabolic health through a process that is partially mediated by gut microbiota modulation. To compare the effects of CR and IF with different dietary structures on metabolic health and the gut microbiota, we performed an experiment in which mice were subjected to a CR or IF regimen and an additional IF control (IF^Ctrl) group whose total energy intake was not different from that of the CR group was included. Each regimen was included for normal chow and high-fat diet.

Results

We showed that in normal-chow mice, the IF^Ctrl regimen had similar positive effects on glucose and lipid metabolism as the CR regimen, but the IF regimen showed almost no influence compared to the outcomes observed in the ad libitum group. IF also resulted in improvements, but the effects were less marked than those associate with CR and IF^Ctrl when the mice were fed a high-fat diet. Moreover, CR created a stable and unique gut microbial community, while the gut microbiota shaped by IF exhibited dynamic changes in fasting-refeeding cycles. At the end of each cycle, the gut microbiota of the IF^Ctrl mice was similar to that of the CR mice, and the gut microbiota of the IF mice was similar to that of the ad libitum group. When the abundance of Lactobacillus murinus OTU2 was high, the corresponding metabolic phenotype was improved regardless of eating pattern and dietary structure, which might be one of the key bacterial groups in the gut microbiota that is positively correlated with metabolic amelioration.

Conclusion

There are interactions among the amount of food intake, the diet structure, and the fasting time on metabolic health. The structure and composition of gut microbiota modified by dietary regimens might contribute to the beneficial effects on the host metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-00987-5.

Late-life intermittent fasting decreases aging-related frailty and increases renal hydrogen sulfide production in a sexually dimorphic manner

Global average life expectancy continues to rise. As aging increases the likelihood of frailty, which encompasses metabolic, musculoskeletal, and cognitive deficits, there is a need for effective anti-aging treatments. It is well established in model organisms that dietary restriction (DR), such as caloric restriction or protein restriction, enhances health and lifespan. However, DR is not widely implemented in the clinic due to patient compliance and its lack of mechanistic underpinnings. Thus, the present study tested the effects of a somewhat more clinically applicable and adoptable DR regimen, every-other-day (EOD) intermittent fasting, on frailty in 20-month-old male and female C57BL/6 mice. Frailty was determined by a series of metabolic, musculoskeletal, and cognitive tasks performed prior to and toward the end of the 2.5-month dietary intervention. Late-life EOD fasting attenuated overall energy intake, hypothalamic inflammatory gene expression, and frailty in males. However, it failed to reduce overall caloric intake and had a little positive effect in females. Given that the selected benefits of DR are dependent on augmented production of the gasotransmitter hydrogen sulfide (H₂S) and that renal H₂S production declines with age, we tested the effects of EOD fasting on renal H₂S production capacity and its connection to frailty in males. EOD fasting boosted renal H₂S production, which positively correlated with improvements in multiple components of frailty tasks. Therefore, late-life initiated EOD fasting is sufficient to reduce aging-related frailty, at least in males, and suggests that renal H₂S production capacity may modulate the effects of late-life EOD fasting on frailty.

Caloric restriction following early-life high fat-diet feeding represses skeletal muscle TNF in male rats

Chronic metabolic diseases are on the rise worldwide and their etiology is multifactorial. Among them, inflammatory components like Tumor Necrosis Factor (TNF), contribute to whole-body metabolic impairment. Caloric Restriction (CR) combats metabolic diseases, but how it reduces inflammation remains understudied. We aimed to evaluate the impact of chronic CR on muscle inflammation, in particular TNF. In our study, 4-week old male Sprague-Dawley rats were fed a high-fat diet (HF, 45% Kcal of fat from lard) ad libitum for 3 months. After estimation of their energy requirement (1 month), they were then divided into three groups: HF ad libitum (OL), weight maintenance with AIN93M (9.5% Kcal from fat; ML, 100% of energy requirement), and caloric restriction (CR, AIN93M with 75% of energy requirement). This dietary intervention continued for six months. At this point, rats were sacrificed and gastrocnemius muscle was collected. CR induced a profound shift in fat and lean mass, and decreased growth factor IGF-1. Muscle qPCR analysis showed a marked decrease in inflammation and TNF (premRNA, mRNA, and protein) by CR, accompanied by Tnf promoter DNA hypermethylation. CR increased expression of histone deacetylase Sirt6 and decreased methyltransferase Suv39h1, together with decreased Tnf promoter and coding region binding of NF- κB and C/EBP-β. Following miRNA database mining, qPCR analysis revealed that CR downregulated the proinflammatory miR-19b and increased the anti-inflammatory miR-181a and its known targets. Chronic CR is able to regulate muscle-specific inflammation by targeting the NF-κB pathway as well as transcriptional and post-transcriptional regulation of Tnf gene.

The Effects of Graded Levels of Calorie Restriction XV: Phase Space Attractors Reveal Distinct Behavioral Phenotypes

Calorie restriction (CR) has a positive impact on health and life span. Previous work, however, does not reveal the whole underlying mechanism of behavioral phenotypes under CR. We propose a new approach based on phase space reconstruction (PSR) to analyze the behavioral responses of mice to graded CR. This involved reconstructing high-dimensional attractors which topologically represent the intrinsic dynamics of mice based on low-dimensional time series of movement counts observed during the 90-day time course of restriction. PSR together with correlation dimensions (CD), Kolmogorov entropy (KE), and multifractal spectra builds a map from internal attractors to the phenotype of mice and reveals the mice with increasing CR levels undergo significant changes from a normal to a new state. Features of the attractors (CD and KE) were significantly associated with gene expression profiles in the hypothalamus of the same individuals.

Lifelong restriction of dietary branched-chain amino acids has sex-specific benefits for frailty and lifespan in mice

Protein restricted (PR) diets promote health and longevity in many species. While the precise components of a PR diet that mediate the beneficial effects to longevity have not been defined, we recently showed that many metabolic effects of PR can be attributed to reduced dietary levels of the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine. Here, we demonstrate that restricting dietary BCAAs increases the survival of two different progeroid mouse models, delays frailty and promotes the metabolic health of wild-type C57BL/6J mice when started in midlife, and leads to a 30% increase in lifespan and a reduction in frailty in male, but not female, wild-type mice when fed lifelong. Our results demonstrate that restricting dietary BCAAs can increase healthspan and longevity in mice, and suggest that reducing dietary BCAAs may hold potential as a translatable intervention to promote healthy aging.

Nutritional Control of Intestinal Stem Cells in Homeostasis and Tumorigenesis

Food and nutrition have a profound impact on organismal health and diseases, and tissue-specific adult stem cells play a crucial role in coordinating tissue maintenance by responding to dietary cues. Emerging evidence indicates that adult intestinal stem cells (ISCs) actively adjust their fate decisions in response to diets and nutritional states to drive intestinal adaptation. Here, we review the signaling mechanisms mediating the dietary responses imposed by caloric intake and nutritional composition (i.e., macronutrients and micronutrients), fasting-feeding patterns, diet-induced growth factors, and microbiota on ISCs and their relevance to the beginnings of intestinal tumors.

The Potential of Resveratrol to Act as a Caloric Restriction Mimetic Appears to Be Limited: Insights from Studies in Mice

Caloric restriction (CR) has been shown repeatedly to prolong the lifespan in laboratory animals, with its benefits dependent on molecular targets forming part of the nutrient signaling network, including the NAD-dependent deacetylase silent mating type information regulation 2 homologue 1 (SIRT1). It has been hypothesized that the stilbene resveratrol (RSV) may counteract age- and obesity-related diseases similarly to CR. In yeast and worms, RSV-promoted longevity also depended on SIRT1. While it remains unclear whether RSV can prolong lifespans in mammals, some studies in rodents supplemented with RSV have reported lowered body weight (BW) and fat mass, improved insulin sensitivity, lowered cholesterol levels, increased fitness, and mitochondrial biogenesis. Molecular mechanisms possibly leading to such changes include altered gene transcription and activation of SIRT1, AMP-activated kinase (AMPK), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A). However, some mouse models did not benefit from RSV treatment to the same extent as others. We conducted a literature search on PubMed (15 April, 2020) for trials directly comparing RSV application to CR feeding in mice. In most studies retrieved by this systematic PubMed search, mice supplemented with RSV did not show significant reductions of BW, glucose, or insulin. Moreover, in some of these studies, RSV and CR treatments affected molecular targets differently and/or findings on RSV and CR impacts varied between trials. We discuss those RSV-induced changes in gene transcription hypothesized to partly counteract age-related alterations. Although there may be a moderate effect of RSV supplementation on parameters such as insulin sensitivity toward a more CR-like profile in mice, data are inconsistent. Likewise, RSV supplementation trials in humans report controversial findings. While we consider that RSV may, under certain circumstances, moderately mimic some aspects of CR, current evidence does not fully support its use to prevent or treat age- or obesity-related diseases.

Effect of fasting on body composition and proteolysis gene expression in skeletal muscles and liver of BEH+/+ and BEL mice

Fasting improves health, but can cause muscle weakness. We assessed body composition in 21-week old males of Berlin high (BEH+/+) and Berlin low (BEL) strains after two bouts of 48-h or 40-h of fasting with 5-day refeeding in between, respectively. BEH+/+ mice tended to loose less weight than BEL in bout 1 and 2 (16.0 ± 2.7 versus 23.5 ± 2.9%, p < 0.001 and 17.1 ± 3.4 versus 20.4 ± 3.4%, p = 0.17, respectively). In spite of greater serum IGF-1 and body fat levels, BEH+/+ mice showed more severe muscle atrophy, but less marked liver wasting and fat depletion than BEL mice. BEH+/+ mice also showed smaller increases in expression of p62, Atrogin-1, and Mstn genes in skeletal muscles. In summary, BEL mice show resistance to fasting-induced muscle wasting in spite of low serum IGF-1 levels and high expression of genes associated with muscle atrophy.

Healthful aging mediated by inhibition of oxidative stress

The progressive increase in lifespan over the past century carries with it some adversity related to the accompanying burden of debilitating diseases prevalent in the older population. This review focuses on oxidative stress as a major mechanism limiting longevity in general, and healthful aging, in particular. Accordingly, the first goal of this review is to discuss the role of oxidative stress in limiting longevity, and compare healthful aging and its mechanisms in different longevity models. Secondly, we discuss common signaling pathways involved in protection against oxidative stress in aging and in the associated diseases of aging, e.g., neurological, cardiovascular and metabolic diseases, and cancer. Much of the literature has focused on murine models of longevity, which will be discussed first, followed by a comparison with human models of longevity and their relationship to oxidative stress protection. Finally, we discuss the extent to which the different longevity models exhibit the healthful aging features through physiological protective mechanisms related to exercise tolerance and increased β-adrenergic signaling and also protection against diabetes and other metabolic diseases, obesity, cancer, neurological diseases, aging-induced cardiomyopathy, cardiac stress and osteoporosis.

Combined effects of caloric restriction and fish oil attenuated anti-depressant and anxiolytic-like effects of fish oil: association with hippocampal BDNF concentrations

Omega-3-enriched fish oil (FO) and caloric restriction (CR) are nutritional therapeutic approaches that exert an important impact on brain function, behavior, memory, and neuroprotection. Here, we investigate the synergic effects of both therapeutic approaches combined (CR + FO) on behavior (memory, anxiety-like behavior, antidepressant-like behavior), as well as its association with hippocampal brain-derived neurotrophic factor (BDNF) concentrations. Adult male Wistar rats were divided into four dietary groups: Control group (C) - chow ad libitum; CR group - 30 % CR, considering C group food intake; FO group - FO-enriched chow ad libitum; and CR + FO group - FO-enriched 30 % CR chow. After 12 weeks of dietary treatment, behavioural analysis set was conducted, and hippocampal BDNF concentrations were measured. FO group presented anxiolytic-like and antidepressant-like behaviors as well as improved memory in the Morris' water maze. These effects were attenuated by the combined CR + FO treatment. FO group also presented higher BDNF concentrations. There was a positive association between the number of entries in the platform quadrant in the MWM and hippocampal BDNF concentrations (β = 0.39; R² = 0.15; p = 0.042) and an inverse association between forced swim immobility time and BDNF concentrations (β = -0.39; R² = 0.15; p = 0.041). Taken together, our data showed that the 12-week FO dietary treatment promoted anxiolytic-like and antidepressant-like behaviors as well as memory improvement, and these effects were associated with BDNF concentrations. Synergic effects of interventions attenuated FO-related behavioral responses and BDNF concentrations and probably reduced hippocampal neuroplasticity.

Limits to sustained energy intake. XXX. Constraint or restraint? Manipulations of food supply show peak food intake in lactation is constrained

Lactating mice increase food intake 4- to 5-fold, reaching an asymptote in late lactation. A key question is whether this asymptote reflects a physiological constraint, or a maternal investment strategy (a 'restraint'). We exposed lactating mice to periods of food restriction, hypothesizing that if the limit reflected restraint, they would compensate by breaching the asymptote when refeeding. In contrast, if it was a constraint, they would by definition be unable to increase their intake on refeeding days. Using isotope methods, we found that during food restriction, the females shut down milk production, impacting offspring growth. During refeeding, food intake and milk production rose again, but not significantly above unrestricted controls. These data provide strong evidence that asymptotic intake in lactation reflects a physiological/physical constraint, rather than restraint. Because hypothalamic neuropeptide Y (Npy) was upregulated under both states of restriction, this suggests the constraint is not imposed by limits in the capacity to upregulate hunger signalling (the saturated neural capacity hypothesis). Understanding the genetic basis of the constraint will be a key future goal and will provide us additional information on the nature of the constraining factors on reproductive output, and their potential links to life history strategies.

In Contrast to Dietary Restriction, Application of Resveratrol in Mice Does not Alter Mouse Major Urinary Protein Expression

Resveratrol (RSV) supplementation in mice has been discussed as partly mimicking the beneficial effects of dietary restriction (DR). However, data on putative benefits from resveratrol application in mice and other model organisms including humans is contradictory. Mouse major urinary proteins (MUPs) are a family of proteins that are expressed in rodent liver and secreted via urine. Impacting (mating) behavior and pheromone communication, they are severely down-regulated upon DR. We carried out two studies in C57BL/6Rj mice where RSV was either supplemented via diet or injected intraperitoneally for 8 weeks. Contrary to −40% DR, RSV did not decrease total MUP protein expression or Mup (amongst others Mup3, Mup5, Mup6, Mup15, and Mup20) mRNA levels in mouse liver when compared to ad-libitum (AL)-fed controls. Since inhibitory glucocorticoid response elements can be found in Mup promoters, we also measured glucocorticoid receptor (GR) levels in nuclear hepatic extracts. Consistent with differential MUP expression, we observed more nuclear GR in DR mice than in RSV-supplemented and AL control mice with no difference between RSV and AL. These findings point to the notion that, in mice, RSV does not mimic DR in terms of differential MUP expression.

The Effects of Graded Levels of Calorie Restriction: XIV. Global Metabolomics Screen Reveals Brown Adipose Tissue Changes in Amino Acids, Catecholamines, and Antioxidants After Short-Term Restriction in C57BL/6 Mice

Animals undergoing calorie restriction (CR) often lower their body temperature to conserve energy. Brown adipose tissue (BAT) is stimulated through norepinephrine when rapid heat production is needed, as it is highly metabolically active due to the uncoupling of the electron transport chain from ATP synthesis. To better understand how BAT metabolism changes with CR, we used metabolomics to identify 883 metabolites that were significantly differentially expressed in the BAT of C57BL/6 mice, fed graded CR (10%, 20%, 30%, and 40% CR relative to their individual baseline intake), compared with mice fed ad libitum (AL) for 12 hours a day. Pathway analysis revealed that graded CR had an impact on the TCA cycle and fatty acid degradation. In addition, an increase in nucleic acids and catecholamine pathways was seen with graded CR in the BAT metabolome. We saw increases in antioxidants with CR, suggesting a beneficial effect of mitochondrial uncoupling. Importantly, the instigator of BAT activation, norepinephrine, was increased with CR, whereas its precursors l-tyrosine and dopamine were decreased, indicating a shift of metabolites through the activation pathway. Several of these key changes were correlated with food anticipatory activity and body temperature, indicating BAT activation may be driven by responses to hunger.

The Effects of Graded Levels of Calorie Restriction: XIII. Global Metabolomics Screen Reveals Graded Changes in Circulating Amino Acids, Vitamins, and Bile Acids in the Plasma of C57BL/6 Mice

Calorie restriction (CR) remains the most robust intervention to extend life span and improve health span. Using a global mass spectrometry–based metabolomics approach, we identified metabolites that were significantly differentially expressed in the plasma of C57BL/6 mice, fed graded levels of calorie restriction (10% CR, 20% CR, 30% CR, and 40% CR) compared with mice fed ad libitum for 12 hours a day. The differential expression of metabolites increased with the severity of CR. Pathway analysis revealed that graded CR had an impact on vitamin E and vitamin B levels, branched chain amino acids, aromatic amino acids, and fatty acid pathways. The majority of amino acids correlated positively with fat-free mass and visceral fat mass, indicating a strong relationship with body composition and vitamin E metabolites correlated with stomach and colon size, which may allude to the beneficial effects of investing in gastrointestinal organs with CR. In addition, metabolites that showed a graded effect, such as the sphinganines, carnitines, and bile acids, match our previous study on liver, which suggests not only that CR remodels the metabolome in a way that promotes energy efficiency, but also that some changes are conserved across tissues.

Dietary Protein, Exercise, and Frailty Domains

Increasing awareness of the impact of frailty on elderly people resulted in research focusing on factors that contribute to the development and persistence of frailty including nutrition and physical activity. Most effort so far has been spent on understanding the association between protein intake and the physical domain of frailty. Far less is known for other domains of frailty: cognition, mood, social health and comorbidity. Therefore, in the present narrative review, we elaborate on the evidence currently known on the association between protein and exercise as well as the broader concept of frailty. Most, but not all, identified studies concluded that low protein intake is associated with a higher prevalence and incidence of physical frailty. Far less is known on the broader concept of frailty. The few studies that do look into this association find a clear beneficial effect of physical activity but no conclusions regarding protein intake can be made yet. Similar, for other important aspects of frailty including mood, cognition, and comorbidity, the number of studies are limited and results are inconclusive. Future studies need to focus on the relation between dietary protein and the broader concept of frailty and should also consider the protein source, amount and timing.

Recent Advances in Anti-Aging Medicine

A rapidly aging population in Korea has led to increased attention in the field of anti-aging medicine. The purpose of anti-aging medicine is to slow, stop, or reverse the aging process and its associated effects, such as disability and frailty. Anti-aging medicine is emerging as a growing industry, but many supplements or protocols are available that do not have scientific evidence to support their claims. In this review, the mechanisms of action and the clinical implications of anti-aging interventions were examined and explained. Calorie restriction mimetics define compounds that imitate the outcome of calorie restriction, including an activator of AMP protein kinase (metformin), inhibitor of growth hormone/insulin-like growth factor-1 axis (pegvisomant), inhibitor of mammalian target of rapamycin (rapamycin), and activator of the sirtuin pathway (resveratrol). Hormonal replacement has also been widely used in the elderly population to improve their quality of life. Manipulating healthy gut microbiota through prebiotic/probiotics or fecal microbiota transplantation has significant potential in anti-aging medicine. Vitamin D is expected to be a primary anti-aging medicine in the near future due to its numerous positive effects in the elderly population.

The Effects of Graded Levels of Calorie Restriction: X. Transcriptomic Responses of Epididymal Adipose Tissue

Calorie restriction (CR) leads to a remarkable decrease in adipose tissue mass and increases longevity in many taxa. Since the discovery of leptin, the secretory abilities of adipose tissue have gained prominence in the responses to CR. We quantified transcripts of epididymal white adipose tissue of male C57BL/6 mice exposed to graded levels of CR (0–40% CR) for 3 months. The numbers of differentially expressed genes (DEGs) involved in NF-κB, HIF1-α, and p53 signaling increased with increasing levels of CR. These pathways were all significantly downregulated at 40% CR relative to 12 h ad libitum feeding. In addition, graded CR had a substantial impact on DEGs associated with pathways involved in angiogenesis. Of the 497 genes differentially expressed with graded CR, 155 of these genes included a signal peptide motif. These putative signaling proteins were involved in the response to ketones, TGF-β signaling, negative regulation of insulin secretion, and inflammation. This accords with the previously established effects of graded CR on glucose homeostasis in the same mice. Overall these data suggest reduced levels of adipose tissue under CR may contribute to the protective impact of CR in multiple ways linked to changes in a large population of secreted proteins.

Reconciling nutritional geometry with classical dietary restriction: Effects of nutrient intake, not calories, on survival and reproduction

Dietary restriction (DR) is one of the main experimental paradigms to investigate the mechanisms that determine lifespan and aging. Yet, the exact nutritional parameters responsible for DR remain unclear. Recently, the advent of the geometric framework of nutrition (GF) has refocussed interest from calories to dietary macronutrients. However, GF experiments focus on invertebrates, with the importance of macronutrients in vertebrates still widely debated. This has led to the suggestion of a fundamental difference in the mode of action of DR between vertebrates and invertebrates, questioning the suggestion of an evolutionarily conserved mechanism. The use of dietary dilution rather than restriction in GF studies makes comparison with traditional DR studies difficult. Here, using a novel nonmodel vertebrate system (the stickleback fish, Gasterosteus aculeatus), we test the effect of macronutrient versus calorie intake on key fitness‐related traits, both using the GF and avoiding dietary dilution. We find that the intake of macronutrients rather than calories determines both mortality risk and reproduction. Male mortality risk was lowest on intermediate lipid intakes, and female risk was generally reduced by low protein intakes. The effect of macronutrient intake on reproduction was similar between the sexes, with high protein intakes maximizing reproduction. Our results provide, to our knowledge, the first evidence that macronutrient, not caloric, intake predicts changes in mortality and reproduction in the absence of dietary dilution. This supports the suggestion of evolutionary conservation in the effect of diet on lifespan, but via variation in macronutrient intake rather than calories.

Regulation of intestinal growth in response to variations in energy supply and demand

The growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients. Paradoxically, during whole body energy deficit including calorie restriction, the intestine grows in size. To understand how and why this happens, we reviewed data from several animal models of energetic challenge. These were bariatric surgery, cold exposure, lactation, dietary whey protein intake and calorie restriction. Notably, these challenges all reduced the adipose tissue mass, altered hypothalamic neuropeptide expression and increased intestinal size. Based on these data, we propose that the loss of energy in the adipose tissue promotes the growth of the intestine via a signalling mechanism involving the hypothalamus. We discuss possible candidates in this pathway including data showing a correlative change in intestinal (ileal) expression of the cyclin D1 gene with adipose tissue mass, adipose derived-hormone leptin and hypothalamic expression of leptin receptor and the pro-opiomelanocortin gene. The ability of the intestine to grow in size during depletion of energy stores provides a mechanism to maximize assimilation of ingested energy and in turn sustain critical functions of tissues important for survival.

The effects of graded levels of calorie restriction: XI. Evaluation of the main hypotheses underpinning the life extension effects of CR using the hepatic transcriptome

Calorie restriction (CR) may extend longevity by modulating the mechanisms involved in aging. Different hypotheses have been proposed for its main mode of action. We quantified hepatic transcripts of male C57BL/6 mice exposed to graded levels of CR (0% to 40% CR) for three months, and evaluated the responses relative to these various hypotheses. Of the four main signaling pathways implied to be linked to the impact of CR on lifespan (insulin/insulin like growth factor 1 (IGF-1), nuclear factor-kappa beta (NF-ĸB), mechanistic target of rapamycin (mTOR) and sirtuins (SIRTs)), all the pathways except SIRT were altered in a manner consistent with increased lifespan. However, the expression levels of SIRT4 and SIRT7 were decreased with increasing levels of CR. Changes consistent with altered fuel utilization under CR may reduce reactive oxygen species production, which was paralleled by reduced protection. Downregulated major urinary protein (MUP) transcription suggested reduced reproductive investment. Graded CR had a positive effect on autophagy and xenobiotic metabolism, and was protective with respect to cancer signaling. CR had no significant effect on fibroblast growth factor-21 (FGF21) transcription but affected transcription in the hydrogen sulfide production pathway. Responses to CR were consistent with several different hypotheses, and the benefits of CR on lifespan likely reflect the combined impact on multiple aging related processes.

Sex-dependent Differences in Liver and Gut Metabolomic Profiles With Acarbose and Calorie Restriction in C57BL/6 Mice

Acarbose, an alpha-glucosidase inhibitor used in treating type 2 diabetes, impairs complex carbohydrate digestion and absorption and extends life span in mice (without a requisite reduction in food intake). To assess sex-differential effects coincident with calorie restriction versus a nonrestricted longevity enhancing intervention, we evaluated the metabolite profiles (by liquid chromatography-mass spectroscopy) from livers and cecal contents of C57BL/6J mice (n = 4/sex/group), which were maintained for 10 months under one of the three diet treatments: ad libitum control diet (CON), ad libitum control diet containing 0.1% acarbose (ACA), or 40% calorie restriction using the control diet (CR). Principal component analysis revealed sex-differential profiles with ACA in livers. Of the identified metabolites (n = 621) in liver, CR significantly altered ~44% (males:187↑/131↓, females:74↑/148↓) compared with CON, in contrast with ACA (M:165↑/61↓, F:52↑/60↓). Dissimilarity in ACA-F liver metabolites was observed for ~50% of common metabolites from ACA-M and CR-M/F. CR resulted in fewer significant cecal metabolite differences (n = 615 metabolites; M:86↑/66↓, F:51↑/48↓ vs CON), relative to ACA treatment (M:32↑/189↓, F:36↑/137↓). Metabolomic profiling identifies sex-differential and tissue-specific effects with amino acid metabolism sub-pathways including those involving tryptophan, branch-chain and sulfur amino acids, and the urea cycle, as well as bile acid, porphyrin, and cofactor metabolism pathways.

Aging Kidney and Aging-Related Disease

With the development of society and improvement of health care, the life span is much longer than before, which brings serious aging problems. Among all the aging problems, renal aging grows to be nonnegligible issue. The aging process of kidney is always accompanied with structural and functional changes. Molecular changes, including Klotho and Sirtuins, are the basic causes of phenotypical changes. Cell senescence and cell autophagy play fundamental roles in the process of renal aging. To effectively intervene in the process of renal aging, different methods have been tried separately, which could produce different effects. Effective intervention of renal aging could be meaningful for healthy state of the whole body.