Caloric Restriction Conditions Research Articles

Dietary methionine functions in proliferative zone maintenance and egg production via sams-1 in Caenorhabditis elegans.

The maintenance of germ cells is critical for the prosperity of offspring. The amount of food consumption is known to be closely related to reproduction, i.e. the number of eggs decreases under calorie-restricted conditions in various organisms. Previous studies in Caenorhabditis elegans have reported that calorie restriction reduces the number of eggs and the reduction can be rescued by methionine. However, the effect of methionine on the reproductive process has not been fully understood. In this study, to assess the gonadal function of methionine metabolism, we firstly demonstrated that a depletion in dietary methionine resulted in reduced levels of S-adenosyl-l-methionine (SAM) and S-adenosyl homocysteine in wild-type N2, but not in glp-1 mutants, which possess only a few germ cells. Second, we found no recovery in egg numbers upon methionine administration in SAM synthase (sams)-1 mutants. Furthermore, a reduced number of proliferative zone nuclei exhibited in the sams-1 mutants was not rescued via methionine. Thus, our results have shown that dietary methionine is required for the normal establishment of both the germline progenitor pool and fecundity, mediated by sams-1.

Unraveling the Anti-Aging Properties of Phycocyanin from the Cyanobacterium Spirulina (Arthrospira platensis).

In recent years, marine natural products have become one of the most important resources of novel lead compounds for critical diseases associated with age. Spirulina, a dietary supplement made from blue-green algae (cyanobacteria: scientific name Arthrospira platensis), is particularly rich in phycocyanin, a phycobiliprotein, which accounts for up to 20% of this cyanobacterium's dry weight and is considered responsible for its anti-cancer, anti-inflammatory and antioxidant activities. Although the anti-aging activity of phycocyanin has been investigated, how exactly this compound works against aging remains elusive. The aim of our research is to use the yeast Saccharomyces cerevisiae as a model organism to investigate the anti-aging properties of phycocyanin from A. platensis. Our results show that phycocyanin has a powerful anti-aging effect, greatly extending the chronological life span of yeast cells in a dose-dependent way, as the effect was also pronounced when cells were grown in SD medium under calorie restriction conditions (0.2% glucose). Both ROS and accumulation of dead cells were followed by staining chronologically aged cells with dihydrorhodamine 123 (DHR123) and propidium iodide (PI). Interestingly, we found that most of the aged phycocyanin-treated cells, which were unable to form colonies, were actually ROS+/PI-. Finally, we show that the moment in which phycocyanin is added to the culture does not substantially influence its effectiveness in counteracting chronological aging.

Preparation and characterization of ATP-loaded chitosan/alginate nanoparticles for therapeutic applications

Adenosine triphosphate (ATP) is known as an energy source and is generated by mitochondria which is the powerhouse of the cell. The ATP supplies energy through the disassociation of the phosphate group by the cellular enzymes. The extracellular ATP in the extracellular environment acts as a signaling molecule and can act as an anti-inflammatory molecule, can promote cancer progression, and also can act as a pro-inflammatory molecule. The degradation of ATP is a major disadvantage by ectonucleotidases that attenuates the therapeutic property of ATP in the extracellular environment. We have formulated chitosan/alginate nanoparticles loaded with ATP for increasing their encapsulation efficiency and for sustained drug release. This encapsulation can avoid ATP degradation from ectonucleotidases. Nanoparticle characterization by DLS, FTIR, SEM, encapsulation efficiency, and cytotoxicity assay by XTT assay and Live-dead assay was monitored for the synthesized nano formulated ATP. Our results showed that the formulated ATP-loaded chitosan/alginate nanoparticle sized about 342 nm with the optimum encapsulation efficiency of about 92.03% with a sustained drug release profile. These nano formulated ATP could be used for calorie restriction conditions where ATP can be supplied as an extracellular source for bypassing oxidative phosphorylation, and we can circumvent the oxidant production during oxidative phosphorylation. The concept of avoiding oxidative stress by bypassing oxidative phosphorylation can open an avenue for healthy aging.

OR22-2 Ghrelin Receptor (GHSR1a) Functional Selectivity As A Novel Pharmacotherapeutic Strategy To Normalize Dysfunctional Metabolic Homeostasis

Abstract The growth hormone secretagogue receptor-1a (GHSR1a) is the cognate G protein-coupled receptor (GPCR) for the orexigenic agonist ghrelin and the anorexigenic antagonist liver-expressed antimicrobial peptide-2 (LEAP2). The ghrelinergic system is activated under conditions of caloric restriction and/or environmental stress, and it acts pleiotropically to restore physiological homeostasis by modulating both central and peripheral metabolic processes, including food-seeking behavior, glycemia, energy utilization/nutrient partitioning, and cardiovascular function. Consequently, ghrelin/GHSR1a signaling provides an accessible and desirable pharmacological target. GHSR1a-mediated physiological responses rely upon distinct G protein- and β-arrestin (βarr)-dependent signaling pathways, a property referred to as 'functional selectivity' or 'biased signaling.' Thus, when treating disorders of metabolic dysfunction (e.g., obesity, type II diabetes, neurodegenerative disease), a pharmacotherapeutic strategy that modulates 'biased' GHSR1a signaling may uncouple desired therapeutic outcomes from unwanted side effects. For example, animal models bearing G protein- or βarr-biasing GHSR1a mutations may express differences in orexigenic and glucoregulatory effects that are signaling pathway-dependent, and our group has demonstrated that GHSR1a antagonism blunts cocaine-induced neuroadaptive behaviors via a mechanism requiring βarr2 in dopaminergic neurons (Toth et al., 2016, Synapse). Based on these findings and the principle of ligand functional selectivity, we sought to identify new GHSR1a drug candidates that could distinguish between G protein and βarr pathways. We discovered a GHSR1a-selective, G protein-biased agonist — N8279 (NCATS-SM8864) — based on a novel chemotype. Comprehensive pharmacological analysis revealed that N8279 elicits potent and biased Gαq activity at both the apo- and ghrelin-bound GHSR1a. Molecular modeling coupled with mutagenesis and medical chemistry supports that N8279 signals through the GHSR1a via a unique extended binding mode requiring the extracellular loop 2 and thereby, enables preferential signaling through the Gαq pathway over alternative G proteins (Gαi∕o, Gα12∕13) and βarr2. Critically, N8279 is readily brain penetrant in mice, exhibits advantageous pharmacokinetics, and attenuates aberrant dopaminergic behaviors in both genetic and pharmacological mouse models of hyperdopaminergia. Our findings together provide important insights into mechanisms governing GPCR signaling and illustrate how functional selectivity might be leveraged to develop GHSR1a pharmacotherapeutics to normalize pathological disruptions of metabolic homeostasis. Presentation: Monday, June 13, 2022 11:15 a.m. - 11:30 a.m.

Bone marrow adipose tissue

Bone marrow adipose tissue (BMAT) represents > 10% total fat mass in healthy humans and further increases in diverse clinical conditions. Like white adipose tissue (WAT), BMAT can produce hormones such as adiponectin, suggesting that it may exert systemic metabolic effects. Unlike WAT, BMAT increases in conditions of caloric restriction (CR), in which it is a key source of increased circulating adiponectin. Thus, BMAT appears developmentally and functionally distinct from WAT. However, the impact of BMAT on health and disease remains poorly understood. Thus, the objective of my research is to determine the fundamental functions and clinical significance of BMAT. My lab's research combines preclinical animal models, human clinical studies and data science approaches using the UK Biobank. Mouse models include CR studies in adiponectin knockout mice, to test if BMAT acts via adiponectin to influence the metabolic, skeletal and immunological effects of CR. Clinical studies include the use of positron emission tomography and computed tomography (PET-CT) to assess BMAT's metabolic functions in vivo. Finally, we are using deep learning to analyse BMAT in magnetic resonance imaging data from the UK Biobank, thereby allowing us to identify the physiological, pathological and genetic factors associated with altered BMAT. (1) Adiponectin KO mice: We have found, unexpectedly, that lack of adiponectin enhances, rather than impairs, CR-induced improvements in glucose tolerance. Compared to wild-type counterparts, KO mice have lower fasting glucose during CR. Adiponectin KO also alters the immunological effects of CR. (2) PET-CT studies: in mice we find that BMAT glucose uptake is not insulin or cold-responsive, demonstrating that BMAT is metabolically distinct from WAT and brown adipose tissue. In humans, we have found that BMAT has high basal glucose uptake under fasting conditions, greater even than that of skeletal muscle. Thus, BMAT may influence systemic metabolic homeostasis as a site of high glucose disposal. (3) UK Biobank studies: our deep learning segmentations have yielded expected inverse associations between BMFF and bone mineral density (BMD) and identified new site- and sex-dependent relationships between BMFF, BMD and peripheral adiposity. Our preclinical and clinical studies have identified new fundamental functions of BMAT and adiponectin, including metabolic and immunological effects. In our UK Biobank studies, we have developed and validated a new deep learning method for high-throughput BMFF analysis in the UKBB. Our initial results already provide new insights for the role of BMAT in skeletal and metabolic health. We have since analysed BMFF in ∼ 37,000 subjects and are pursuing Genome- and Phenome-Wide Association Studies to identify genetic and pathophysiological factors associated with altered BMAT. Together, our research establishes the utility of machine learning for population-level BMFF analysis and promises to elucidate the full impact of BMAT on human health and disease. William Cawthorn is an Associate Professor at the Centre for Cardiovascular Science, University of Edinburgh. His PhD research (Institute of Metabolic Science, University of Cambridge) investigated the regulation of adipogenesis while his postdoctoral studies (University of Michigan) focussed on mesenchymal cell fate and the function bone marrow adipose tissue (BMAT). In 2015, he established his laboratory at The University of Edinburgh with the overarching research goal of determining the function of BMAT. To do so his lab combines preclinical animal models, human clinical studies and data science approaches using the UK Biobank. Methods include in-depth metabolic phenotyping, immunological analyses, the development of novel biomedical imaging techniques, and artificial intelligence to open new avenues for population-level studies. Together, his research addresses the interplay between metabolism, immunological function and skeletal health, both in the context of fundamental biology and chronic diseases. He is a founding member and current Interim President of the International Bone Marrow Adiposity Society and is also the University of Edinburgh's Open Science Ambassador for the League of European Research Institutions (LERU).

The GhsrQ343X allele favors the storage of fat by acting on nutrient partitioning.

The Growth Hormone Secretagogue Receptor (GHSR) mediates key properties of the gut hormone ghrelin on metabolism and behavior. Nevertheless, most recent observations also support that the GHSR is a constitutively active G protein-coupled receptor endowed of a sophisticated tuning involving a balance of endogenous ligands. Demonstrating the feasibility of shifting GHSR canonical signaling in vivo, we previously reported that a model with enhanced sensitivity to ghrelin (GhsrQ343X mutant rats) developed fat accumulation and glucose intolerance. Herein, we investigated the contribution of energy homeostasis to the onset of this phenotype, as well as behavioral responses to feeding or pharmacological challenges, by comparing GhsrM/M rats to wild-type littermate rats 1) as freely behaving animals and 2) in feeding and locomotor paradigms. Herein, GhsrM/M rats showed enhanced locomotor response to a GHSR agonist while locomotor or anorexigenic responses to amphetamine or cabergoline (dopamine receptor 2 agonist), respectively, were preserved. Ad libitum fed GhsrM/M rats consumed and conditioned for sucrose similarly to littermate control rats. In calorie-restricted conditions, GhsrM/M rats retained food anticipatory activity and maintained better their body weight and glycemia. Importantly, prior to fat accumulation, male GhsrM/M rats preferentially used carbohydrates as fuel substrate without alterations of energy intake, energy expenditure or physical activity and showed alterations of the GHSR system (i.e. enhanced ratio of GHSR hormones LEAP2:acyl-ghrelin and increased Ghsr expression in the hypothalamus). Overall, the present study provides proof of concept that shifted GHSR signaling can specifically alter nutrient partitioning resulting in modified balance of carbohydrate/lipid utilization.

Caloric restriction causes a distinct reorganization of the lipidome in quiescent and non-quiescent cells of budding yeast.

After budding yeast cells cultured in a nutrient-rich liquid medium with 0.2% glucose (under caloric restriction conditions) or 2% glucose (under non-caloric restriction conditions), ferment glucose to ethanol and then consume ethanol, they enter the stationary phase. The process of their chronological aging begins. At that point, the yeast culture starts to accumulate quiescent and non-quiescent cells. Here, we purified the high- and low-density populations of quiescent and non-quiescent cells from the yeast cultures limited in calorie supply or not. We then employed mass spectrometry-based quantitative lipidomics to assess the aging-associated changes in high- and low-density cells’ lipidomes. We found that caloric restriction, a geroprotective dietary intervention, alters the concentrations of many lipid classes through most of the chronological lifespan of the high- and low-density populations of quiescent and non-quiescent cells. Specifically, caloric restriction decreased triacylglycerol, increased free fatty acid, elevated phospholipid and amplified cardiolipin concentrations. Based on these findings, we propose a hypothetical model for a caloric restriction-dependent reorganization of lipid metabolism in budding yeast’s quiescent and non-quiescent cells. We also discovered that caloric restriction creates lipidomic patterns of these cells that differ from those established by two other robust geroprotectors, namely the tor1Δ mutation and lithocholic acid.

Antibody-mediated inhibition of GDF15-GFRAL activity reverses cancer cachexia in mice.

Cancer cachexia is a highly prevalent condition associated with poor quality of life and reduced survival1. Tumor-induced perturbations in the endocrine, immune and nervous systems drive anorexia and catabolic changes in adipose tissue and skeletal muscle, hallmarks of cancer cachexia2-4. However, the molecular mechanisms driving cachexia remain poorly defined, and there are currently no approved drugs for the condition. Elevation in circulating growth differentiation factor 15 (GDF15) correlates with cachexia and reduced survival in patients with cancer5-8, and a GDNF family receptor alpha like (GFRAL)-Ret proto-oncogene (RET) signaling complex in brainstem neurons that mediates GDF15-induced weight loss in mice has recently been described9-12. Here we report a therapeutic antagonistic monoclonal antibody, 3P10, that targets GFRAL and inhibits RET signaling by preventing the GDF15-driven interaction of RET with GFRAL on the cell surface. Treatment with 3P10 reverses excessive lipid oxidation in tumor-bearing mice and prevents cancer cachexia, even under calorie-restricted conditions. Mechanistically, activation of the GFRAL-RET pathway induces expression of genes involved in lipid metabolism in adipose tissues, and both peripheral chemical sympathectomy and loss of adipose triglyceride lipase protect mice from GDF15-induced weight loss. These data uncover a peripheral sympathetic axis by which GDF15 elicits a lipolytic response in adipose tissue independently of anorexia, leading to reduced adipose and muscle mass and function in tumor-bearing mice.

Caloric restriction induces anabolic resistance to resistance exercise

PurposeWeight loss can result in the loss of muscle mass and bone mineral density. Resistance exercise is commonly prescribed to attenuate these effects. However, the anabolic endocrine response to resistance exercise during caloric restriction has not been characterized.MethodsParticipants underwent 3-day conditions of caloric restriction (15 kcal kg FFM−1) with post-exercise carbohydrate (CRC) and with post-exercise protein (CRP), and an energy balance control (40 kcal kg FFM−1) with post-exercise carbohydrate (CON). Serial blood draws were taken following five sets of five repetitions of the barbell back squat exercise on day 3 of each condition.ResultsIn CRC and CRP, respectively, growth hormone peaked at 2.6 ± 0.4 and 2.5 ± 0.9 times the peak concentrations observed during CON. Despite this, insulin-like growth factor-1 concentrations declined 18.3 ± 3.4% in CRC and 27.2 ± 3.8% in CRP, which was greater than the 7.6 ± 3.6% decline in CON, over the subsequent 24 h. Sclerostin increased over the first 2 days of each intervention by 19.2 ± 5.6% in CRC, 21.8 ± 6.2% in CRP and 13.4 ± 5.9% in CON, but following the resistance exercise bout, these increases were attenuated and no longer significant.ConclusionDuring caloric restriction, there is considerable endocrine anabolic resistance to a single bout of resistance exercise which persists in the presence of post-exercise whey protein supplementation. Alternative strategies to restore the sensitivity of insulin-like growth factor-1 to growth hormone need to be explored.

Comparison of microplate- and bottle-based methods to age yeast for chronological life span assays

This study compared the chronological life span and survival of Saccharomyces cerevisiae aged in a microplate or bottle, under different aeration and calorie restriction conditions. Our data shows that limited aeration in the microplate-aged culture contributed to slower outgrowth but extended yeast CLS compared to the bottle-aged culture.

Less is more or more is less: Implications of glucose metabolism in the regulation of the reproductive potential and total lifespan of the Saccharomyces cerevisiae yeast.

Carbohydrates are dietary nutrients that have an influence on cells physiology, cell reproductive capacity and, consequently, the lifespan of organisms. They are used in cellular processes after conversion to glucose, which is the primary source of energy and carbon skeleton for biosynthetic processes. Studies of the influence of glucose on cellular parameters and lifespan of organisms are primarily concerned with the effect of low glucose concentration defined as calorie restriction conditions. However, the effect of high glucose concentration on cell physiology is also very important. Thus, a comparative analysis of the effects of low and high glucose concentration conditions on cell efficiency was proposed with regard to reproductive capacity and total lifespan of the cell. Glucose concentration determines the type of metabolism and biosynthetic capabilities, which in turn, through the regulation on the cell size, may affect the reproductive capacity of cells. This study was conducted on yeast cells of wild-type and mutant strains Δgpa2 and Δgpr1 with glucose signalling pathway impairment. Such an experimental model enabled testing both the role of glucose concentration in the regulation of metabolic changes and the extent to which these changes depend on the extracellular or intracellular glucose concentrations. It has been shown here that calorie/glucose excess connected with changes in cell metabolic fluxes increases biosynthetic capabilities of yeast cells. This leads to an increase in cell dry weight accompanied by the increase in cell size and a simultaneous decrease in the reproductive potential and the overall length of cell life.

Mechanisms through which lithocholic acid delays yeast chronological aging under caloric restriction conditions.

All presently known geroprotective chemical compounds of plant and microbial origin are caloric restriction mimetics because they can mimic the beneficial lifespan- and healthspan-extending effects of caloric restriction diets without the need to limit calorie supply. We have discovered a geroprotective chemical compound of mammalian origin, a bile acid called lithocholic acid, which can delay chronological aging of the budding yeast Saccharomyces cerevisiae under caloric restriction conditions. Here, we investigated mechanisms through which lithocholic acid can delay chronological aging of yeast limited in calorie supply. We provide evidence that lithocholic acid causes a stepwise development and maintenance of an aging-delaying cellular pattern throughout the entire chronological lifespan of yeast cultured under caloric restriction conditions. We show that lithocholic acid stimulates the aging-delaying cellular pattern and preserves such pattern because it specifically modulates the spatiotemporal dynamics of a complex cellular network. We demonstrate that this cellular network integrates certain pathways of lipid and carbohydrate metabolism, some intercompartmental communications, mitochondrial morphology and functionality, and liponecrotic and apoptotic modes of aging-associated cell death. Our findings indicate that lithocholic acid prolongs longevity of chronologically aging yeast because it decreases the risk of aging-associated cell death, thus increasing the chance of elderly cells to survive.

Fabrication of cyclo olefin polymer microfluidic devices for trapping and culturing of yeast cells.

A microfluidic platform is designed and fabricated to investigate the role of uncharacterized YOR060C (Sld7) protein in aging in yeast cells for the first time. Saccharomyces cerevisiae yeast cells are trapped in the series of C-shaped regions (0.5nL) of COP (cyclo olefin polymer), PMMA (poly methylmethacrylate), or PS (polystyrene) microbioreactors. The devices are fabricated using hot embossing and thermo-compression bonding methods. Photolithography and electrochemical etching are used to form the steel mold needed for hot embossing. The cell cycle processes are investigated by monitoring green fluorescent protein (GFP) tagged Sld7 expressions under normal as well as calorie restricted conditions. The cells are loaded at 1μL/min flowrate and trapped successfully within each chamber. The medium is continuously fed at 0.1μL/min throughout the experiments. Fluorescent signals of the low abundant Sld7 proteins could be distinguished only on COP devices. The background fluorescence of COP is found 1.22 and 7.24 times lower than that of PMMA, and PS, respectively. Hence, experiments are continued with COP, and lasted for more than 40h without any contamination. The doubling time of the yeast cells are found as 72min and 150min, and the growth rates as 9.63×10-3min-1 and 4.62×10-3min-1, in 2% glucose containing YPD and YNB medium, respectively. The product concentration (Sld7p:GFP) increased in accordance with cell growth. The dual role of Sld7 protein in both cell cycle and chronological aging needs to be further investigated following the preliminary experimental results.

Glycation inhibitors extend yeast chronological lifespan by reducing advanced glycation end products and by back regulation of proteins involved in mitochondrial respiration

Advanced Glycation End products (AGEs) are implicated in aging process. Thus, reducing AGEs by using glycation inhibitors may help in attenuating the aging process. In this study using Saccharomyces cerevisiae yeast system, we show that Aminoguanidine (AMG), a well-known glycation inhibitor, decreases the AGE modification of proteins in non-calorie restriction (NR) (2% glucose) and extends chronological lifespan (CLS) similar to that of calorie restriction (CR) condition (0.5% glucose). Proteomic analysis revealed that AMG back regulates the expression of differentially expressed proteins especially those involved in mitochondrial respiration in NR condition, suggesting that it switches metabolism from fermentation to respiration, mimicking CR. AMG induced back regulation of differentially expressed proteins could be possibly due to its chemical effect or indirectly by glycation inhibition. To delineate this, Metformin (MET), a structural analog of AMG and a mild glycation inhibitor and Hydralazine (HYD), another potent glycation inhibitor but not structural analog of AMG were used. HYD was more effective than MET in mimicking AMG suggesting that glycation inhibition was responsible for restoration of differentially expressed proteins. Thus glycation inhibitors particularly AMG, HYD and MET extend yeast CLS by reducing AGEs, modulating the expression of proteins involved in mitochondrial respiration and possibly by scavenging glucose. SignificanceThis study reports the role of glycation in aging process. In the non-caloric restriction condition, carbohydrates such as glucose promote protein glycation and reduce CLS. While, the inhibitors of glycation such as AMG, HYD, MET mimic the caloric restriction condition by back regulating deregulated proteins involved in mitochondrial respiration which could facilitate shift of metabolism from fermentation to respiration and extend yeast CLS. These findings suggest that glycation inhibitors can be potential molecules that can be used in management of aging.

Absence of Non-histone Protein Complexes at Natural Chromosomal Pause Sites Results in Reduced Replication Pausing in Aging Yeast Cells

There is substantial evidence that genomic instability increases during aging. Replication pausing (and stalling) at difficult-to-replicate chromosomal sites may induce genomic instability. Interestingly, in aging yeast cells, we observed reduced replication pausing at various natural replication pause sites (RPSs) in ribosomal DNA (rDNA) and non-rDNA locations (e.g., silent replication origins and tRNA genes). The reduced pausing occurs independent of the DNA helicase Rrm3p, which facilitates replication past these non-histone protein-complex-bound RPSs, and is independent of the deacetylase Sir2p. Conditions of caloric restriction (CR), which extend life span, also cause reduced replication pausing at the 5S rDNA and at tRNA genes. In aged and CR cells, the RPSs are less occupied by their specific non-histone protein complexes (e.g., the preinitiation complex TFIIIC), likely because members of these complexes have primarily cytosolic localization. These conditions may lead to reduced replication pausing and may lower replication stress at these sites during aging.

Effects of ghrelin in energy balance and body weight homeostasis.

Ghrelin is a gut peptide composed of 28 amino acids mostly secreted in the gastric fundus mucosa. It was isolated and described in 1999 by Kojima et al. and only three years later its specific receptor, GHSR1a, was also identified. Ghrelin, the endogenous ligand for the GH secretagogue receptor, is the only peripheral orexigenic hormone that activates the receptors to be found especially in the appetite center (hypothalamus and pituitary gland). Ghrelin is present in human plasma in two forms: an inactive form known as deacylated ghrelin, and an active form called acylated ghrelin synthesized under the action of ghrelin O-acyltransferase enzyme (GOAT). The literature even mentions an extremely complex ghrelin/GOAT/GHSR system involved in the regulation of human energy, metabolism and adaptation of energy homeostasis to environmental changes. In humans, there is a preprandial rise and a postprandial fall in plasma ghrelin levels, which strongly suggest that the peptide plays a physiological role in meal initiation and may be employed in determining the amount and quality of ingested food. Besides the stimulation of food intake, ghrelin determines a decrease in energy expenditure and promotes the storage of fatty acids in adipocytes. Thus, in the human body ghrelin induces a positive energy balance, an increased adiposity gain, as well as an increase in caloric storage, seen as an adaptive mechanism to caloric restriction conditions. In the current world context, when we are witnessing an increasing availability of food and a reduction of energy expenditure to a minimum level, these mechanisms have become pathogenic. As a consequence, the hypothesis that ghrelin is involved in the current obesity epidemic has been embraced by many scholars and researchers.

Body mass loss correlates with cognitive performance in primates under acute caloric restriction conditions.

Brain functions are known to consume high levels of energy, thus, the integrity of cognitive performance can be drastically impacted by acute caloric restriction. In this study, we tested the impact of a 40% caloric restriction on the cognitive abilities of the grey mouse lemur (Microcebus murinus).Twenty-three male mouse lemurs were divided into two groups: 13 control animals (CTL) that were fed with 105kJ/day and 10calorie restricted (CR) animals that received 40% less food (63kJ/day) than the CTL animals. The animals were fed according to their group for 19days. Before treatment, we assessed baseline associative learning capacities, resting metabolic rates and locomotor performance of both animal groups. After treatment, we tested the same functions as well as long-term memory.Our results showed that CR animals had lower learning performance following caloric restriction. The effects of caloric restriction on memory recall varied and depended on the metabolism of the individual animal. Body mass loss was linked to memory test performance in the CR group, and lower performance was observed in individuals losing the most weight. While CR was observed to negatively impact learning, locomotor capacities were preserved in CR animals, and there were higher resting metabolic rates in the CR group. Our data reinforce the strong link between energy allocation and brain function, and suggest that in the context of food shortage, learning capacities could be a limiting parameter in the adaptation to a changing environment.

Korean Pine Nut Oil Attenuated Hepatic Triacylglycerol Accumulation in High-Fat Diet-Induced Obese Mice.

Korean pine nut oil (PNO) has been reported to influence weight gain and lipid metabolism. We examined whether PNO replacement in a high-fat diet (HFD) can ameliorate HFD-induced hepatic steatosis. Five-week-old male C57BL mice were fed control diets containing 10% of the energy from fat from PNO or soybean oil (SBO) (PC, SC) or HFDs with 45% of the energy from fat, with 10% from PNO or SBO and 35% from lard (PHFD, SHFD), for 12 weeks. Body weight gain and amount of white adipose tissue were lower in PHFD (10% and 18% lower, respectively) compared with SHFD. Hepatic triacylglycerol (TG) level was significantly lower in PHFD than the SHFD (26% lower). PNO consumption upregulated hepatic ACADL mRNA levels. The hepatic PPARG mRNA level was lower in the PC than in the SC. Expression of the sirtuin (SIRT) 3 protein in white adipose tissue was down-regulated in the SHFD and restored in the PHFD to the level in the lean control mice. SIRT 3 was reported to be upregulated under conditions of caloric restriction (CR) and plays a role in regulating mitochondrial function. PNO consumption resulted in lower body fat and hepatic TG accumulation in HFD-induced obesity, which seemed to be associated with the CR-mimetic response.

COCOA (Theobroma cacao) POLYPHENOL-RICH EXTRACT INCREASES THE CHRONOLOGICAL LIFESPAN OF Saccharomyces cerevisiae

BACKGROUND: Saccharomyces cerevisiae is a model organism with conserved aging pathways. Yeast chronological lifespan experiments mimic the processes involved in human non-dividing tissues, such as the nervous system or skeletal muscle, and can speed up the search for biomolecules with potential anti-aging effects before proceeding to animal studies. OBJECTIVE: To test the effectiveness of a cocoa polyphenol-rich extract (CPE) in expanding the S. cerevisiae chronological lifespan in two conditions: in the stationary phase reached after glucose depletion and under severe caloric restriction. MEASUREMENTS: Using a high-throughput method, wild-type S. cerevisiae and its mitochondrial manganese-dependent superoxide dismutase null mutant (sod2Δ) were cultured in synthetic complete dextrose medium. After 2 days, 0, 5 and 20 mg/ml of CPE were added, and viability was measured throughout the stationary phase. The effects of the major components of CPE were also evaluated. To determine yeast lifespan under severe caloric restriction conditions, cultures were washed with water 24 h after the addition of 0 and 20 mg/ml of CPE, and viability was followed over time. RESULTS : CPE increased the chronological lifespan of S. cerevisiae during the stationary phase in a dose-dependent manner. A similar increase was also observed in (sod2Δ). None of the major CPE components (theobromine, caffeine, maltodextrin, (-)-epicatechin, (+)-catechin and procyanidin B2) was able to increase the yeast lifespan. CPE further increased the yeast lifespan under severe caloric restriction. CONCLUSION: CPE increases the chronological lifespan of S. cerevisiae through a SOD2-independent mechanism. The extract also extends yeast lifespan under severe caloric restriction conditions. The high-throughput assay used makes it possible to simply and rapidly test the efficacy of a large number of compounds on yeast aging, requiring only small amounts, and is thus a convenient screening assay to accelerate the search for biomolecules with potential anti-aging effects.

Sir2 is involved in the transcriptional modulation of NHP6A in Saccharomyces cerevisiae

The Sir proteins, namely Sir2, 3 and 4, have roles related to heterochromatin, but genome-wide studies have revealed their presence at many euchromatic loci, although the functional meaning of this is still not clear. Nhp6a is an abundant HMG-like protein in yeast, which has a role in transcription by modulating chromatin structure and nucleosome number. Although much is known about its structure and function, information regarding its regulation is scarce. NHP6A, among other genes, emerges in ChIP-on chip studies of global Sir proteins binding, suggesting it could be regulated by SIR. We have investigated NHP6A expression in sir deletion mutants as well as in SIR2 overexpressing conditions. In addition, we have asked if the Sir2 deacetylation activity is involved by using conditions that either inhibit (treatment with nicotinamide) or enhance (calorie restriction conditions) Sir2 activity. We have found that, consistent with previous microarray studies, NHP6A expression undergoes a slight increase in sir mutant strains, but is strongly repressed when SIR2 is overexpressed. In a sir3 mutant strain the gene continues to be transcribed, even in SIR2 overexpressing conditions. In addition, treating the cells with nicotinamide counteracts the SIR2 overexpressing effect. Finally, conditions that are known to potentiate Sir2 deacetylation activity seem to mimic the effect of SIR2 overexpression on NHP6A. Our results suggest that Sir2 is involved in the regulation of NHP6A promoter, acting more as a specific repressor, rather than a long-range silencer. This effect is specific, and the Sir2 deacetylase activity is required for the Sir2 mediated repression of NHP6A. Moreover, the presence of the SIR complex seems required for Sir2 to silence NHP6A.