Metabolic and neuropsychiatric effects of calorie restriction and sirtuins

SIRT1: An Intermediator of Key Pathways Regulating Pulmonary Diseases

Silent information regulator type-1 (SIRT1), a nicotinamide adenine dinucleotide+-dependent deacetylase, is a member of the sirtuins family and has unique protein deacetylase activity. SIRT1 participates in physiological as well as pathophysiological processes by targeting a wide range of protein substrates and signalings. In this review, we described the latest progress of SIRT1 in pulmonary diseases. We have introduced the basic information and summarized the prominent role of SIRT1 in several lung diseases, such as acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, lung cancer, and aging-related diseases.

Mechanistic insights into fasting-induced autophagy in the aging heart

Autophagy is a prosurvival mechanism for the clearance of accumulated abnormal proteins, damaged organelles, and excessive lipids within mammalian cells. A growing body of data indicates that autophagy is reduced in aging cells. This reduction leads to various diseases, such as myocardial hypertrophy, infarction, and atherosclerosis. Recent studies in animal models of an aging heart showed that fasting-induced autophagy improved cardiac function and longevity. This improvement is related to autophagic clearance of damaged cellular components via either bulk or selective autophagy (such as mitophagy). In this editorial, we summarize the mechanisms of autophagy in normal and aging hearts. In addition, the protective effect of fasting-induced autophagy in cardiac aging has been highlighted.

The Association between Blood SIRT1 and Ghrelin, Leptin, and Antibody Anti-Hypothalamus: A Comparison in Normal Weight and Anorexia Nervosa

Sirtuin 1 (SIRT1) is a sensor of cell energy availability, regulating metabolic homeostasis as well as leptin and ghrelin, and it could be considered as a potential plasmatic marker. The aim of this study was to assess whether circulating SIRT1 varies consistently with leptin, ghrelin, body mass index (BMI), and IgG reactive to hypothalamic antigens in anorexia nervosa (AN). Fifty-four subjects were evaluated: 32 with AN and 22 normal-weight control subjects. Serum levels of SIRT1, leptin, ghrelin, and IgG reactive to hypothalamic antigens were evaluated by ELISA. Results showed that serum SIRT1 is increased in patients with AN, and the amount is decreased in relation to the duration of the illness. SIRT1 concentration approaches the values obtained for the control group, although the difference is still statistically significant. A negative correlation between serum SIRT1 values and leptin or BMI values has been found. On the contrary, a positive correlation between SIRT1 and ghrelin or IgG specific for hypothalamic antigens is reported. These findings suggest that a peripheral evaluation of SIRT1 could be a possible clinical/biochemical parameter related to AN. In addition, we can assume that SIRT1 is related to autoantibody production and may correlate with the intensity/severity of AN. Thus, reducing the production of autoantibodies specific for hypothalamic cells could be a sign of improvement of the clinical condition.

A new view on functions of the lysine demalonylase activity of SIRT5

AIMS

The specificity of the lysine demalonylation substrates of the pharmaceutically attractive tumor promoter/suppressor SIRT5 is not comprehensively clarified. The present study re-analyses publicly available data and highlights potentially pharmaceutically interesting outcomes by the use of bioinformatics.

MATERIALS AND METHODS

The interaction networks of SIRT5 malonylome from the wild-type and ob/ob (obese pre-diabetic type) mice were subjected to the pathway enrichment and gene function prediction analysis using GeneMania (3.5.2) application run under Cytoscape (3.9.1) environment.

KEY FINDINGS

The analysis in the wild-type mice revealed the involvement of SIRT5 malonylome in Eukaryotic translation elongation (ETE; the nodes EF1A1, EEF2, EEF1D, and EEF1G), Amino acid and derivative metabolism (AADM), and Selenoamino acid metabolism (SAM). The tumor promoter/suppressor activity of SIRT5 is mediated through the tumor promoter substrates included in AADM (GLUD1, SHMT1, ACAT1), and the tumor suppressor substrates involved in AADM and SAM (ALDH9A1, BHMT, GNMT). Selen stimulates the expression of SIRT5 and other sirtuins. SIRT5 in turn regulates the selenocysteine synthesis, which creates a regulatory loop. The analysis of SIRT5 malonylome in pre-diabetic ob/ob mice identifies the mTORC1 pathway as a mechanism, which facilitates SIRT5 functions. The comparison of the outcomes of SIRT5 malonylome, succinylome, and glutarylome analysis disclosed several differences.

SIGNIFICANCE

The analysis showed additional aspects of SIRT5 malonylome functions besides the control of glucose metabolism. It defined several unique substrates and pathways, and it showed differences compared to other enzymatic activities of SIRT5, which could be used for pharmaceutical benefits.

Fasting during cancer treatment: a systematic review

Background

Clinical data on the modern topic fasting among cancer patients are rare. This review aimed to summarise published clinical data on fasting and its effects on patients undergoing chemotherapy and therefore to give some directions in advising patients with the desire to fast.

Method

A systematic search was conducted searching five electronic databases (Embase, Cochrane, PsychInfo, CINAHL and Medline) to find studies concerning the use, effectiveness and potential harm of fasting during therapy on cancer patients. The main endpoints were quality of life, side effects and toxicities of the fasting intervention.

Results

The search results totaled 3983 hits. After systematic sorting according to standardised pre-defined criteria, nine publications which covered eight studies with 379 patients were included in this systematic review. The majority of the patients included were diagnosed with breast- and gynaecological cancers. Fasting duration and timepoints ranged significantly (24–140 h before, and on the day of, chemotherapy to 56 h after chemotherapy). In one study patients were fasting before cancer surgery. The studies were mostly low to moderate quality and reported heterogeneous results. Overall, the studies were insufficiently powered to detect significant effects on the predefined endpoints.

Conclusion

Fasting for short periods does not have any beneficial effect on the quality of life of cancer patients during treatment. Evidence on fasting regimes reducing side effects and toxicities of chemotherapy is missing. In contrast, as the negative effects of unintentional weight loss are known to impact clinical outcomes severely, fasting is not indicated in this context.

Role of Sirtuins in Physiology and Diseases of the Central Nervous System

Silent information regulators, sirtuins (SIRTs), are a family of enzymes which take part in major posttranslational modifications of proteins and contribute to multiple cellular processes, including metabolic and energetic transformations, as well as regulation of the cell cycle. Recently, SIRTs have gained increased attention as the object of research because of their multidirectional activity and possible role in the complex pathomechanisms underlying human diseases. The aim of this study was to review a current literature evidence of SIRTs' role in the physiology and pathology of the central nervous system (CNS). SIRTs have been demonstrated to be crucial players in the crosstalk between neuroinflammation, neurodegeneration, and metabolic alterations. The elucidation of SIRTs' role in the background of various CNS diseases offers a chance to define relevant markers of their progression and promising candidates for novel therapeutic targets. Possible diagnostic and therapeutic implications from SIRTs-related investigations are discussed, as well as their future directions and associated challenges.

Sirtfoods: New Concept Foods, Functions, and Mechanisms

Sirtfood is a new concept food that compounds diets that can target sirtuins (SIRTs). SIRTs are nicotinamide adenine dinucleotide (NAD⁺)-dependent deacylases and ADP-ribosyltransferases (enzymes). SIRTs are mediators of calorie restriction (CR) and their activation can achieve some effects similar to CR. SIRTs play essential roles in ameliorating obesity and age-related metabolic diseases. Food ingredients such as resveratrol, piceatannol, anthocyanidin, and quinine are potential modulators of SIRTs. SIRT modulators are involved in autophagy, apoptosis, aging, inflammation, and energy homeostasis. Sirtfood proponents believe that natural Sirtfood recipes exert significant health effects.

Targeting autophagy and neuroinflammation pathways with plant-derived natural compounds as potential antidepressant agents

Major depressive disorder (MDD) is a life-threatening disease that presents several characteristics. The pathogenesis of depression still remains poorly understood. Moreover, the mechanistic interactions of natural components in treating depression to target autophagy and neuroinflammation are yet to be evaluated. This study overviewed the effects of plant-derived natural components in regulating critical pathways, particularly neuroinflammation and autophagy, associated with depression. A list of natural components, including luteolin, apigenin, hyperforin, resveratrol, salvianolic acid b, isoliquiritin, nobiletin, andrographolide, and oridonin, have been investigated. All peer-reviewed journal articles were searched by Scopus, MEDLINE, PubMed, Web of Science, and Google Scholar using the appropriated keywords, including depression, neuroinflammation, autophagy, plant, natural components, etc. The neuroinflammation and autophagy dysfunction are critically associated with the pathophysiology of depression. Natural components with higher efficiency and lower complications can be used for targeting neuroinflammation and autophagy. These components with different doses showed the beneficial antidepressant properties in rodents. These can modulate autophagy markers, mainly AMPK, LC3II/LC3I ratio, Beclin-1. Moreover, they can regulate the NLRP3 inflammasome, resulting in the suppression of proinflammatory cytokines (e.g., IL-1β and IL-18). Future in vitro and in vivo studies are required to develop novel therapeutic approaches based on plant-derived active components to treat MDD.

Diet and longevity in the Blue Zones: A set-and-forget issue?

The Blue Zones (BZs) are areas of the globe inhabited by exceptionally long-lived populations. They include the island of Okinawa in Japan, the island of Ikaria in Greece, the mountain area of the island of Sardinia in Italy, and the peninsula of Nicoya in Costa Rica. Their longevity is a relatively recent phenomenon that has been progressively investigated since the dawn of this century. Research efforts over the past two decades have sought to shed light on the factors associated with this longevity, as well as explore the possibility of lessons transferable to the general population. Among the features of BZ inhabitants, described in the literature, their eating habits hold a prominent place, as these have the advantage of being easily quantifiable and applicable on a larger scale. However, it is too often taken for granted that the mere fact of being documented in a long-lived population makes the diet a causal factor of that population's longevity; this is a claim which should be proven. Furthermore, it is implicitly assumed that a specific BZ diet is homogeneous and remains stable over time, whereas some evidence suggests the opposite. Therefore, this review summarizes our current knowledge of the BZ diets and discusses whether they can be considered as a paradigmatic example of healthy nutrition valid for anyone or, rather, a set of evolving food patterns that has offered benefits to a few specific communities in recent decades.

Transcriptional response to cold and fasting acclimation in Onychostoma macrolepis during the overwintering stage

In this study, we investigated the transcriptome responses of the liver of Onychostoma macrolepis in by RNA sequencing. The sampling process involved three groups: 1G (0 week, 10 °C), 2G (12 weeks, 0 °C) and 3G (24 weeks, 10 °C). The body weight, viscera index, hepatopancreas index and intraperitoneal fat index of O. macrolepis showed a decreasing trend with the prolonging of overwintering time. The crude fat contents of whole fish, muscle and liver in O. macrolepis after overwintering were significantly lower than those of the fish before overwintering (p < 0.05). In 1G versus 2G group, 2G versus 3G group and 1G versus 3G group, the differently expressed genes (DEGs) were 4630, 3976 and 2311, respectively. These results indicated that different stages of overwintering period had significant effects on gene expression of O. macrolepis, and the influence degree gradually decreased with the extension of overwintering period. The results of Gene ontology (GO) enrichment showed that these DEGs were mainly related to metabolism and immunity, and most of them were down-regulated. In this study, the KEGG pathway classification results showed that signal transduction was the most representative. In addition, KOG enrichment results showed that many DEGs associated with lipid transport and metabolism were down-regulated during the overwintering period. These observations suggested that slowing metabolism and delaying immunity may be the strategies for overwintering adaptation of O. macrolepis.

Metabolic Regulation of Stem Cells in Aging

PURPOSE OF REVIEW

From invertebrates to vertebrates, the ability to sense nutrient availability is critical for survival. Complex organisms have evolved numerous signaling pathways to sense nutrients and dietary fluctuations, which influence many cellular processes. Although both overabundance and extreme depletion of nutrients can lead to deleterious effects, dietary restriction without malnutrition can increase lifespan and promote overall health in many model organisms. In this review, we focus on age-dependent changes in stem cell metabolism and dietary interventions used to modulate stem cell function in aging.

RECENT FINDINGS

Over the last half-century, seminal studies have illustrated that dietary restriction confers beneficial effects on longevity in many model organisms. Many researchers have now turned to dissecting the molecular mechanisms by which these diets affect aging at the cellular level. One subpopulation of cells of particular interest are adult stem cells, the most regenerative cells of the body. It is generally accepted that the regenerative capacity of stem cells declines with age, and while the metabolic requirements of each vary across tissues, the ability of dietary interventions to influence stem cell function is striking.

SUMMARY

In this review, we will focus primarily on how metabolism plays a role in adult stem cell homeostasis with respect to aging, with particular emphasis on intestinal stem cells while also touching on hematopoietic, skeletal muscle, and neural stem cells. We will also discuss key metabolic signaling pathways influenced by both dietary restriction and the aging process, and will examine their role in improving tissue homeostasis and lifespan. Understanding the mechanisms behind the metabolic needs of stem cells will help bridge the divide between a basic science interpretation of stem cell function and a whole-organism view of nutrition, thereby providing insight into potential dietary or therapeutic interventions.

Epigenetic Modulation of Microglia Function and Phenotypes in Neurodegenerative Diseases

Microglia-mediated neuroinflammation is one of the most remarkable hallmarks of neurodegenerative diseases (NDDs), including AD, PD, and ALS. Accumulating evidence indicates that microglia play both neuroprotective and detrimental roles in the onset and progression of NDDs. Yet, the specific mechanisms of action surrounding microglia are not clear. Modulation of microglia function and phenotypes appears to be a potential strategy to reverse NDDs. Until recently, research into the epigenetic mechanisms of diseases has been gradually developed, making it possible to elucidate the molecular mechanisms underlying the epigenetic regulation of microglia in NDDs. This review highlights the function and phenotypes of microglia, elucidates the relationship between microglia, epigenetic modifications, and NDDs, as well as the possible mechanisms underlying the epigenetic modulation of microglia in NDDs with a focus on potential intervention strategies.

Sirtuins, a potential target in Traumatic Brain Injury and relevant experimental models

Traumatic brain injury (TBI) can simply be defined as a violent external injury to the head causing brain dysfunction. The primary injury occurs immediately on impact whereas the secondary injury begins minutes to months after impact. TBI affects a vast majority of population worldwide yet, there isn't any therapeutic intervention available. Sirtuins (SIRTs) are important regulator proteins found in humans. In several neurodegenerative diseases, SIRTs have proven its neuroprotective actions. Owing to the pathophysiological similarities in these diseases and TBI, SIRTs may serve as a potential target for therapeutic intervention in TBI. This review aims to describe the relevance of SIRTs as a potential pharmacological target in TBI. Also, the experimental animal model of TBI explored to understand the role of SIRTs in TBI have been discussed.

Sirt-1 Regulates Physiological Process and Exerts Protective Effects against Oxidative Stress

Background

Recent studies suggest a correlation between the reduced Sirt-1 expression with Alzheimer's diseases (AD) and depression, respectively, suggesting a possible pathogenic role of the altered Sirt-1 expression in neuronal degenerative diseases, such as AD and depression. However, the molecular mechanisms underlying how Sirt-1 reduction impairs neuronal functions remain unknown.

Methods

We used the SK-N-SH neuroblastoma cells to study the role of Sirt-1 expression on physiological roles in neuronal cells. Gain of Sirt-1 was achieved by transiently transfecting Sirt-1 expression plasmid. Sirt-1-specific shRNA was used to elucidate the role of Sirt-1 loss of function. CCK-8 (Cell Counting Kit-8) assay and flow cytometry were used to evaluate cell proliferation. Semiquantitative western blotting was used to detect relative protein levels. A further luciferase reporter gene assay was employed to examine the effect of Sirt-1 expression on the transcriptional activity of p53. RT-qPCR was used to determine the mRNA levels of p21, Bax, and Bcl-2, which were the downstream target genes of p53.

Results

Sirt-1 suppressed the p53 downstream gene p21 transcription, while shRNA-mediated Sirt-1 knockdown resulted in a significant increase in p21 expression, implying a possibility that Sirt-1 promotes neuron proliferation through suppressing p53 transcriptional activity. The mRNA and protein levels of p53 were not affected by the altered Sirt-1 expression, suggesting that Sirt-1 regulates the transcriptional regulatory activity of p53 rather than p53 expression. Indeed, we further confirmed that Sirt-1 appeared to inhibit p53 transcriptional activity by attenuating its acetylation and resulted in a decrease of p53's binding to the p21 promoter. Overexpressed Sirt-1 scavenged reactive oxygen species (ROS) production in SK-N-SH with H₂O₂. Knockdown of Sirt-1 presented opposite effect; the addition of EX527 (Sirt-1 inhibitor) increased ROS accumulation.

Conclusions

Oxidative stress induces Sirt-1 in neuron cells, and Sirt-1 promotes proliferation in SK-N-SH cells, which protects them from oxidative stress-induced cell death, potentially via suppressing the transcriptional activity of p53. These results provide a molecular explanation underlying how the reduced Sirt-1 potentially causes the AD and depression-related diseases, supporting the idea that Sirt-1 can possibly be used as a diagnostic biomarker and/or therapeutic drug target for the AD and depression-related diseases.

Metabolic Reprogramming by Reduced Calorie Intake or Pharmacological Caloric Restriction Mimetics for Improved Cancer Immunotherapy

Caloric restriction and fasting have been known for a long time for their health- and life-span promoting effects, with coherent observations in multiple model organisms as well as epidemiological and clinical studies. This holds particularly true for cancer. The health-promoting effects of caloric restriction and fasting are mediated at least partly through their cellular effects-chiefly autophagy induction-rather than reduced calorie intake per se. Interestingly, caloric restriction has a differential impact on cancer and healthy cells, due to the atypical metabolic profile of malignant tumors. Caloric restriction mimetics are non-toxic compounds able to mimic the biochemical and physiological effects of caloric restriction including autophagy induction. Caloric restriction and its mimetics induce autophagy to improve the efficacy of some cancer treatments that induce immunogenic cell death (ICD), a type of cellular demise that eventually elicits adaptive antitumor immunity. Caloric restriction and its mimetics also enhance the therapeutic efficacy of chemo-immunotherapies combining ICD-inducing agents with immune checkpoint inhibitors targeting PD-1. Collectively, preclinical data encourage the application of caloric restriction and its mimetics as an adjuvant to immunotherapies. This recommendation is subject to confirmation in additional experimental settings and in clinical trials. In this work, we review the preclinical and clinical evidence in favor of such therapeutic interventions before listing ongoing clinical trials that will shed some light on this subject.

CXCL6 regulates cell permeability, proliferation, and apoptosis after ischemia-reperfusion injury by modulating Sirt3 expression via AKT/FOXO3a activation

Chemokine (C-X-C motif) ligand 6 (CXCL6), a member of the CXC chemokine family, reportedly mediates several processes such as inflammation, immunoreaction, cell growth, and metastasis through interaction with the chemokine receptors CXCR1 and CXCR2 in humans; further, CXCR1 and CXCR2 can promote repair and regeneration of organs or tissues after ischemia-reperfusion injury (IRI). In this study, we found that HIF-1α, CXCL6, and CXCR2 expression levels were elevated in human brain microvascular endothelial cells (HBMECs) after IRI, whereas silent information regulator of transcription (Sirt) 3 expression level had reduced. HIF-1α inhibition in an IRI model potently promoted HBMEC proliferation, accompanied by increased Sirt3 and decreased CXCL6/CXCR2 expression levels. CXCL6 knockdown in the IRI model significantly decreased HBMEC permeability and promoted HBMEC proliferation, concurrent with a decrease in apoptosis; it also increased Sirt3 expression levels and decreased CXCL6/CXCR2 protein and phosphorylated AKT (p-AKT) and class O of forkhead box (FOXO) 3a (p-FOXO3a) levels. In addition, CXCL6-induced HBMEC permeability and inhibition of HBMEC proliferation were counteracted by Sirt3 overexpression, and the AKT inhibitor LY294002 counteracted the effect of CXCL6 recombinant proteins on Sirt3, p-AKT, and p-FOXO3a expressions. These results suggest that CXCL6 and Sirt3 are downstream of HIF-1α and that CXCL6 regulatesHBMEC permeability, proliferation, and apoptosis after IRI by modulating Sirt3 expression via AKT/FOXO3a activation.

Resveratrol ameliorates lipopolysaccharide-induced anxiety-like behavior by attenuating YAP-mediated neuro-inflammation and promoting hippocampal autophagy in mice

Resveratrol, a type of natural polyphenol mainly extracted from the skin of grapes, has been reported to protect against inflammatory responses and exert anxiolytic effect. Yes-associated protein (YAP), a major downstream effector of the Hippo signaling pathway, plays a critical role in inflammation. The present study aimed to explore whether YAP pathway was involved in the anxiolytic effect of resveratrol in lipopolysaccharide (LPS)-treated C57BL/6J male mice. LPS treatment induced anxiety-like behavior and decreased sirtuin 1 while increased YAP expression in the hippocampus. Resveratrol attenuated LPS-induced anxiety-like behavior, which was blocked by EX-527 (a sirtuin 1 inhibitor). Mechanistically, the anxiolytic effects of resveratrol were accompanied by a marked decrease in YAP, interleukin-1β and ionized calcium binding adaptor molecule 1 (Iba-1) while a significant increase in autophagic protein expression in the hippocampus. Pharmacological study using XMU-MP-1, a YAP activator, showed that activating YAP could induce anxiety-like behavior and neuro-inflammation as well as decrease hippocampal autophagy. Moreover, activation of YAP by XMU-MP-1 treatment attenuated the ameliorative effects of resveratrol on LPS-induced anxiety-like behavior, while blockade of YAP activation with verteporfin, a YAP inhibitor, attenuated LPS-induced anxiety-like behavior and neuro-inflammation as well as hippocampal autophagy. Finally, rapamycin-mediated promotion of autophagy attenuated LPS-induced anxiety-like behavior and decreased interleukin-1β and Iba-1 expression in the hippocampus. Collectively, these results indicate that amelioration by resveratrol in LPS-induced anxiety-like behavior is through attenuating YAP-mediated neuro-inflammation and promoting hippocampal autophagy, and suggest that inhibition of YAP pathway could be a potential therapeutic target for anxiety-like behavior induced by neuro-inflammation.

Myocardial infarction-induced anxiety-like behavior is associated with epigenetic alterations in the hippocampus of rat

Epidemiological and experimental animal studies indicate that there is a high risk for the incidence of neuropsychiatric disorders suffering from cardiovascular diseases such as myocardial infarction (MI). However, the potential mechanism of this association remains largely unknown. This study sought to evaluate whether epigenetic alterations in the hippocampus is associated with MI-induced anxiety-like behavior in rats. MI was induced by occlusion of the left anterior descending artery in adult female rats. Anxiety-like behavior was examined by elevated plus maze, light-dark box, and open field test. Relative gene and protein levels expression in the hippocampus were tested by qRT-PCR and western blotting, respectively. We found that MI rats exhibited anxiety-like behavior compared with those in controls, and there is a positive correlation between MI and anxiety-like behavior. We also found that MI decreased KDM6B while increased SIRT1 expression in the hippocampus of MI rats relative to those in controls. In addition, MI not only increased levels of IL-1β, bax, and cleaved-caspase 3, but also increased Iba-1 and GFAP expression in the hippocampus, as compared to those in controls, suggesting a promotion of neuro-inflammation and apoptosis in hippocampus. Co-immunoprecipitation assay illustrated that H3K27me3 functioned by counteracting with YAP activation in the hippocampus of MI rats relative to those in controls. Together, these results suggest a potential role of hippocampal epigenetic signaling in MI-induced anxiety-like behavior in rats, and pharmacological targeting KDM6B or SIRT1 could be a strategy to ameliorate anxiety-like behavior induced by MI.

The role of the Acanthamoeba castellanii Sir2-like protein in the growth and encystation of Acanthamoeba

BACKGROUND

The encystation of Acanthamoeba leads to the development of resilient cysts from vegetative trophozoites. This process is essential for the survival of parasites under unfavorable conditions. Previous studies have reported that, during the encystation of A. castellanii, the expression levels of encystation-related factors are upregulated. However, the regulatory mechanisms for their expression during the encystation process remains unknown. Proteins in the sirtuin family, which consists of nicotinamide adenine dinucleotide-dependent deacetylases, are known to play an important role in various cellular functions. In the present study, we identified the Acanthamoeba silent-information regulator 2-like protein (AcSir2) and examined its role in the growth and encystation of Acanthamoeba.

METHODS

We obtained the full-length sequence for AcSir2 using reverse-transcription polymerase chain reaction. In Acanthamoeba transfectants that constitutively overexpress AcSir2 protein, SIRT deacetylase activity was measured, and the intracellular localization of AcSir2 and the effects on the growth and encystation of trophozoites were examined. In addition, the sirtuin inhibitor salermide was used to determine whether these effects were caused by AcSir2 overexpression RESULTS: AcSir2 was classified as a class-IV sirtuin. AcSir2 exhibited functional SIRT deacetylase activity, localized mainly in the nucleus, and its transcription was upregulated during encystation. In trophozoites, AcSir2 overexpression led to greater cell growth, and this growth was inhibited by treatment with salermide, a sirtuin inhibitor. When AcSir2 was overexpressed in the cysts, the encystation rate was significantly higher; this was also reversed with salermide treatment. In AcSir2-overexpressing encysting cells, the transcription of cellulose synthase was highly upregulated compared with that of control cells, and this upregulation was abolished with salermide treatment. Transmission electron microscope-based ultrastructural analysis of salermide-treated encysting cells showed that the structure of the exocyst wall and intercyst space was impaired and that the endocyst wall had not formed.

CONCLUSIONS

These results indicate that AcSir2 is a SIRT deacetylase that plays an essential role as a regulator of a variety of cellular processes and that the regulation of AcSir2 expression is important for the growth and encystation of A. castellanii.

SIRT1 accelerates the progression of activity-based anorexia

Food consumption is fundamental for life, and eating disorders often result in devastating or life-threatening conditions. Anorexia nervosa (AN) is characterized by a persistent restriction of energy intake, leading to lowered body weight, constant fear of gaining weight, and psychological disturbances of body perception. Herein, we demonstrate that SIRT1 inhibition, both genetically and pharmacologically, delays the onset and progression of AN behaviors in activity-based anorexia (ABA) models, while SIRT1 activation accelerates ABA phenotypes. Mechanistically, we suggest that SIRT1 promotes progression of ABA, in part through its interaction with NRF1, leading to suppression of a NMDA receptor subunit Grin2A. Our results suggest that AN may arise from pathological positive feedback loops: voluntary food restriction activates SIRT1, promoting anxiety, hyperactivity, and addiction to starvation, exacerbating the dieting and exercising, thus further activating SIRT1. We propose SIRT1 inhibition can break this cycle and provide a potential therapy for individuals suffering from AN.

Anorexia nervosa is an eating disorder characterized by fear of gaining weight that can lead to serious complications. Here the authors show that inhibition of SIRT1 is protective against the onset and progression of anorectic behavior in an activity-based anorexia model, suggesting SIRT1 could be a potential therapeutic target.

Ginsenoside Rg1 protects against Sca-1+ HSC/HPC cell aging by regulating the SIRT1-FOXO3 and SIRT3-SOD2 signaling pathways in a γ-ray irradiation-induced aging mice model

Aging is characterized by a progressive deterioration in metabolic functions. The present study aimed to investigate the antagonistic effects of ginsenoside Rg1 (Rg1) on the γ-ray irradiation-induced aging of mixed hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs). C57BL/6 mice were divided into a control group, a γ-ray irradiation group that served as an aging mouse model, and an Rg1 group. The Rg1 group was treated with Rg1 at dosage of 20 mg/kg/day for 7 days prior to γ-ray irradiation. The aging mouse model was established by exposing the mice to 6.5-Gy γ-ray total-body irradiation. Stem cell antigen 1 positive (Sca-1⁺) HSC/HPCs isolated from the mice were examined using a senescence-associated β-galactosidase (SA-β-Gal) staining assay. The cell cycle of the HSC/HPCs was examined using flow cytometry. A mixed hematopoietic progenitor cell colony-forming unit (CFU-mix) assay was also conducted. The mRNA and protein expression levels of sirtuin 1 (SIRT1), SIRT3, forkhead box O3 (FOXO3) and superoxide dismutase (SOD2) were evaluated using western blot and reverse transcription-quantitative PCR assays. The results indicated that Rg1 treatment significantly increased white blood cell, red blood cell and platelet counts in peripheral blood compared with those in the γ-ray irradiation group (P<0.05). However, Rg1 significantly attenuated the senescence of Sca-1⁺ HSC/HPCs in the γ-ray irradiation aging mice model. The proportion of SA-β-Gal stained HSC/HPCs was significantly decreased and CFU-Mix counts were significantly increased in the Rg1 group compared with the γ-ray irradiation group (P<0.05). Rg1 significantly increased the mRNA and protein levels of SIRT1, SIRT3, FOXO3 and SOD2 in the Sca-1⁺ HSC/HPCs compared with those in the γ-ray irradiation group (P<0.05). The percentage of Sca-1⁺ HSC/HPCs arrested at the G1 phase in the Rg1 group was significantly decreased compared with that in the γ-ray irradiation group (P<0.05). In conclusion, the present study indicates that Rg1 exerts anti-aging effects via the regulation of SIRT1-FOXO3 and SIRT3-SOD2 signaling pathways, and triggering the progression of Sca-1⁺ HSC/HPCs from the G1 phase to the S phase in γ-ray irradiation-induced aging mice.

Salvianolic Acid B Improves Chronic Mild Stress-Induced Depressive Behaviors in Rats: Involvement of AMPK/SIRT1 Signaling Pathway

Introduction

Depression is one of the most common neuropsychiatric illnesses which leads to a huge social and economic burden on modern society. So, it is necessary to develop an effective and safe pharmacological intervention for depression. Accumulating evidence has shown that adenosine monophosphate-activated protein kinase/sirtuin 1 (AMPK/SIRT1) signaling pathway plays a pivotal role in the development of depression. Our present study aimed to investigate the antidepressant effect and possible mechanisms of salvianolic acid B (SalB) in a chronic mild stress (CMS)-induced depression model in rats.

Materials and Methods

The rats were randomly divided into three groups: control group with no stressor, CMS group and CMS+SalB (30 mg/kg/d) group. After administration for 28 consecutive days, the behavior tests were performed. The rats were sacrificed after behavior tests, and the brain tissues were collected for biochemical analysis.

Results

It was observed that the administration of SalB for 28 consecutive days successfully corrected the depressive-like behaviors in CMS-treated rats. SalB could effectively reduce the gene expression of pro-inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α), as well as nuclear factor-kappa B (NF-κB) p65 protein. In addition, inhibitor of NF-κB (IκB) protein expression was significantly increased after the administration of SalB. Moreover, SalB could effectively decrease protein expression of oxidative stress markers such as 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) and increase the activity of catalase (CAT). SalB treatment also reversed CMS-induced inhibition of Nrf2 signaling pathway, along with increasing the mRNA expression of NAD(P)H:quinone oxidoreductase (NQO-1) and heme oxygenase 1 (HO-1). Regarding the endoplasmic reticulum (ER) stress markers, the protein expressions of C/EBP-homologous protein (CHOP) and glucose-regulated protein 78 kD (GRP78) were also significantly reduced after SalB administration. Furthermore, the supplementation of SalB could effectively activate the AMPK/SIRT1 signaling pathway, which indicated significant increase in pAMPK/AMPK ratio and SIRT1 protein expression.

Conclusion

Our study demonstrated that SalB relieved CMS-induced depressive-like state through the mitigation of inflammatory status, oxidative stress, and the activation of AMPK/SIRT1 signaling pathway.

The Effects of Calorie Restriction on Autophagy: Role on Aging Intervention

Autophagy is an important housekeeping process that maintains a proper cellular homeostasis under normal physiologic and/or pathologic conditions. It is responsible for the disposal and recycling of metabolic macromolecules and damaged organelles through broad lysosomal degradation processes. Under stress conditions, including nutrient deficiency, autophagy is substantially activated to maintain proper cell function and promote cell survival. Altered autophagy processes have been reported in various aging studies, and a dysregulated autophagy is associated with various age-associated diseases. Calorie restriction (CR) is regarded as the gold standard for many aging intervention methods. Although it is clear that CR has diverse effects in counteracting aging process, the exact mechanisms by which it modulates those processes are still controversial. Recent advances in CR research have suggested that the activation of autophagy is linked to the observed beneficial anti-aging effects. Evidence showed that CR induced a robust autophagy response in various metabolic tissues, and that the inhibition of autophagy attenuated the anti-aging effects of CR. The mechanisms by which CR modulates the complex process of autophagy have been investigated in depth. In this review, several major advances related to CR’s anti-aging mechanisms and anti-aging mimetics will be discussed, focusing on the modification of the autophagy response.

Gastrodin alleviates Tourette syndrome via Nrf-2/HO-1/HMGB1/NF-кB pathway

The aim is to study the effects of gastrodin (GA) on striatal inflammation and oxidative stress in rats with Tourette syndrome (TS). The rat model of TS was induced by 3,3'-iminodipropionitrile. Behavioral tests were carried out by stereotype experiment. The concentrations of amino acid transmitters glutamic acid (Glu) and γ-aminobutyric acid (GABA) in striatum were determined by high-performance liquid chromatography. Superoxide dismutase (SOD) and malondialdehyde (MDA) in serum and striatum were detected by commercial kits. Cytokines in serum and striatum were detected by enzyme-linked immunosorbent assay kits. Western blot analysis was used to detect striatum nuclear erythroid factor 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1)/high mobility group box 1 protein (HMGB1)/nuclear factor-кB (NF-кB) pathway-related proteins. The expressions of Nrf-2 and P-NF-кBp65 in striatum were detected by immunohistochemistry. Compared with the control group, the stereotype scores of rats in the model group significantly increased, and the contents of Glu and GABA in striatum obviously increased. GA significantly reduced the stereotype scores and decreased the contents of Glu and GABA. The levels of SOD in serum and striatum were decreased and the content of MDA in serum and striatum were increased compared with the control group, while GA significantly restored the changes. GA significantly adjusted Nrf-2/HO-1/HMGB1/NF-кB pathway-related proteins changes consistent with immunohistochemical changes. GA may protect striatum of rats with TS by regulating Nrf-2/HO-1/HMGB1/NF-кB pathway protein changes in striatum.

Rhynchophylline Attenuates Neurotoxicity in Tourette Syndrome Rats

Tourette syndrome (TS) is a chronic neuropsychiatric disorder with clinical manifestations of involuntary and repeated muscle twitching and vocal twitching. The drugs used to treat TS are relatively limited. The aim of this study was to investigate the effects of rhynchophylline (RH) and the underlying mechanism in 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-induced neurotoxicity in a TS rat model. A TS model was induced with DOI. The rats were divided into control, TS, TS + tiapride (25 mg/kg), and TS + RH (20 and 40 mg/kg) groups. Behavioral tests were performed 24 h after the last administration by nodding and stereotype experiments. Interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α) levels in striatum and serum were detected with an enzyme-linked immunosorbent assay (ELISA). Western blot analysis was used to detect the expression levels of Toll-like receptor (TLR)/nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3)/nuclear factor kappa B (NF-κB) signal proteins in the striatum. The expression of TLR2 and NF-κB p65 subunit was detected with immunohistochemical analysis. RH may significantly improve behavioral changes in rats with DOI-induced TS and reduce the levels of inflammatory factors in serum and striatum. RH inhibited the activation of TLR/NLRP3/NF-κB signaling proteins in the striatum of TS rats. In BV2 cells, DOI-induced inflammation mediated through TLR/NLRP3/NF-κB was significantly inhibited following RH administration. The therapeutic effect of RH in TS was studied and its mechanism of action mediated via the TLR/NLRP3/NF-κB pathway was clarified in vitro and in vivo.

Eating Rewards the Gears of the Clock

Eating behavior is regulated by metabolic and hedonic brain networks, which interact with each other to balance the physiological regulation of hunger and satiety. The daily balance of this regulation is controlled by the central circadian clock. Importantly, metabolic and reward properties of food impact the functioning of circadian clocks, altering the oscillatory activity of the molecular clockwork and circadian rhythms. However, when feeding (metabolic or reward) is timed, the whole circadian system is entrained. Furthermore, besides synchronizing the clock, the timing of both metabolic and reward eating might be crucial for health, to improve circadian physiology, as well as to treat metabolic (e.g., diabetes, obesity) and neurological diseases (e.g., mental, neurodegenerative).

Quiescence Entry, Maintenance, and Exit in Adult Stem Cells

Cells of unicellular and multicellular eukaryotes can respond to certain environmental cues by arresting the cell cycle and entering a reversible state of quiescence. Quiescent cells do not divide, but can re-enter the cell cycle and resume proliferation if exposed to some signals from the environment. Quiescent cells in mammals and humans include adult stem cells. These cells exhibit improved stress resistance and enhanced survival ability. In response to certain extrinsic signals, adult stem cells can self-renew by dividing asymmetrically. Such asymmetric divisions not only allow the maintenance of a population of quiescent cells, but also yield daughter progenitor cells. A multistep process of the controlled proliferation of these progenitor cells leads to the formation of one or more types of fully differentiated cells. An age-related decline in the ability of adult stem cells to balance quiescence maintenance and regulated proliferation has been implicated in many aging-associated diseases. In this review, we describe many traits shared by different types of quiescent adult stem cells. We discuss how these traits contribute to the quiescence, self-renewal, and proliferation of adult stem cells. We examine the cell-intrinsic mechanisms that allow establishing and sustaining the characteristic traits of adult stem cells, thereby regulating quiescence entry, maintenance, and exit.

Mechanisms Through Which Some Mitochondria-Generated Metabolites Act as Second Messengers That Are Essential Contributors to the Aging Process in Eukaryotes Across Phyla

Recent studies have revealed that some low-molecular weight molecules produced in mitochondria are essential contributing factors to aging and aging-associated pathologies in evolutionarily distant eukaryotes. These molecules are intermediates or products of certain metabolic reactions that are activated in mitochondria in response to specific changes in the nutrient, stress, proliferation, or age status of the cell. After being released from mitochondria, these metabolites directly or indirectly change activities of a distinct set of protein sensors that reside in various cellular locations outside of mitochondria. Because these protein sensors control the efficiencies of some pro- or anti-aging cellular processes, such changes in their activities allow to create a pro- or anti-aging cellular pattern. Thus, mitochondria can function as signaling platforms that respond to certain changes in cell stress and physiology by remodeling their metabolism and releasing a specific set of metabolites known as "mitobolites." These mitobolites then define the pace of cellular and organismal aging because they regulate some longevity-defining processes taking place outside of mitochondria. In this review, we discuss recent progress in understanding mechanisms underlying the ability of mitochondria to function as such signaling platforms in aging and aging-associated diseases.

Neuroprotective effect of salidroside against central nervous system inflammation-induced cognitive deficits: A pivotal role of sirtuin 1-dependent Nrf-2/HO-1/NF-κB pathway

Central nervous system (CNS) inflammation occurs in cognitive dysfunctions, but the underlying mechanisms remain unclear. Here, we investigated the role of sirtuin 1 (SIRT1) and salidroside in CNS inflammation-induced cognitive deficits model. In vivo, CNS inflammation was initiated by a single intracerebroventricular injection of lipopolysaccharide (LPS). The levels of inflammatory cytokines and the capability of free radial scavenging were determined after the LPS challenge. In vivo, salidroside and nicotinamide, a SIRT1 inhibitor, were used in PC12 cell. Of note, with the treatment of salidroside, LPS-induced learning and memory impairments were effectively improved. Salidroside also remarkably inhibited the inflammatory cytokines, up-regulated the concentration of superoxide dismutase and inhibited the vitalities of malondialdehyde in serum, hippocampus, and cell supernatant. Besides, the expression of Sirt1, Nrf-2, HO-1, Bax, Bcl-2, caspase-9, and caspase-3 and the phosphorylation of AMPK, NF-κBp65, and IκBα were increased accompanying with the LPS-induced cognitive impairments, which were significantly suppressed by salidroside treatment. In PC12 cell model, nicotinamide significantly abrogated the beneficial effects of salidroside, as indicated by the antioxidant, anti-inflammatory, and antiapoptosis signaling. Together, our results showed that salidroside may be a novel therapy drug in neurodegenerative diseases, and the protective effect was involved in SIRT1-dependent Nrf-2/HO-1/NF-κB pathway.

Fasting enhances cold resistance in fish through stimulating lipid catabolism and autophagy

KEY POINTS

In a cold environment, mammals increase their food intake while fish decrease or stop feeding. However, the physiological value of fasting during cold resistance in fish is currently unknown. Fasting for more than 48 h enhanced acute cold resistance in zebrafish, which correlated with lipid catabolism and cell damage attenuation. Lipid catabolism and autophagy were necessary for cold resistance in fish and the inhibition of mitochondrial fatty acid β-oxidation or autophagy weakened the fasting-induced cold resistance. Repression of mechanistic target of rapamycin (mTOR) signalling pathway by rapamycin largely mimicked the beneficial effects of fasting in promoting cold resistance, suggesting mTOR signalling may be involved in the fasting-induced cold resistance in fish. Our study demonstrates that fasting may be a protective strategy for fish to survive under cold stress.

ABSTRACT

In cold environments, most homeothermic animals increase their food intake to supply more energy to maintain body temperature, whereas most poikilothermic animals such as fishes decrease or even stop feeding under cold stress. However, the physiological value of fasting during cold resistance in poikilotherms has not been explained. Here, we show that moderate fasting largely enhanced cold resistance in fish. By using pharmacological (fenofibrate, mildronate, chloroquine and rapamycin) and nutritional approaches (fatty acids diets and amino acids diets) in wild-type or specific gene knock-out zebrafish models (carnitine palmitoyltransferase-1b-deficient strain, CPT1b^-/- , or autophagy-related protein 12-deficient strain, ATG12^-/- ), we verified that fasting-stimulated lipid catabolism and autophagy played essential roles in the improved cold resistance. Moreover, suppression of the mechanistic target of rapamycin (mTOR) pathway by using rapamycin mostly mimicked the beneficial effects of fasting in promoting cold resistance as either the physiological phenotype or transcriptomic pattern. However, these beneficial effects were largely reduced when the mTOR pathway was activated through high dietary leucine supplementation. We conclude that fasting helps fish to resist cold stress by modulating lipid catabolism and autophagy, which correlates with the mTOR signalling pathway. Therefore, fasting can act as a protective strategy of fish in resisting coldness.

The signaling pathways that mediate the anti-cancer effects of caloric restriction

Caloric restriction (CR) has been shown to promote longevity and ameliorate aging-associated diseases, including cancer. Extensive research over recent decades has revealed that CR reduces IGF-1/PI3K/AKT signaling and increases sirtuin signaling. We recently found that CR also enhances ALDOA/DNA-PK/p53 signaling. In the present review, we summarize the molecular mechanisms underlying the modulation of the IGF-1/PI3K/AKT pathway, sirtuin signaling, and the ALDOA/DNA-PK/p53 pathway by CR. We also summarize the evidence concerning the roles of these signaling pathways in carcinogenesis, and discuss how they are regulated by CR. Finally, we discuss the crosstalk between these signaling pathways.

The effect of fasting or calorie restriction on autophagy induction: A review of the literature

Autophagy is a lysosomal degradation process and protective housekeeping mechanism to eliminate damaged organelles, long-lived misfolded proteins and invading pathogens. Autophagy functions to recycle building blocks and energy for cellular renovation and homeostasis, allowing cells to adapt to stress. Modulation of autophagy is a potential therapeutic target for a diverse range of diseases, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. Traditionally, food deprivation and calorie restriction (CR) have been considered to slow aging and increase longevity. Since autophagy inhibition attenuates the anti-aging effects of CR, it has been proposed that autophagy plays a substantive role in CR-mediated longevity. Among several stress stimuli inducers of autophagy, fasting and CR are the most potent non-genetic autophagy stimulators, and lack the undesirable side effects associated with alternative interventions. Despite the importance of autophagy, the evidence connecting fasting or CR with autophagy promotion has not previously been reviewed. Therefore, our objective was to weigh the evidence relating the effect of CR or fasting on autophagy promotion. We conclude that both fasting and CR have a role in the upregulation of autophagy, the evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation.

SIRT1 activation attenuates α cell hyperplasia, hyperglucagonaemia and hyperglycaemia in STZ-diabetic mice

The NAD⁺-dependent lysine deacetylase, Sirtuin 1 (SIRT1), plays a central role in metabolic regulation. With type 1 diabetes a disease that is characterised by metabolic dysregulation, we sought to assess the impact of SIRT1 activation in experimental, streptozotocin (STZ)-induced diabetes. CD1 mice with and without STZ-induced diabetes were randomized to receive the SIRT1 activating compound, SRT3025, or vehicle over 20 weeks. Vehicle treated STZ-CD1 mice developed severe hyperglycaemia with near-absent circulating insulin and widespread beta cell loss in association with hyperglucagonaemia and expanded islet alpha cell mass. Without affecting ß-cell mass or circulating insulin, diabetic mice that received SRT3025 had substantially improved glycaemic control with greatly reduced islet α cell mass and lower plasma glucagon concentrations. Consistent with reduced glucagon abundance, the diabetes-associated overexpression of key gluconeogenic enzymes, glucose-6-phosphatase and PEPCK were also lowered by SRT3025. Incubating cultured α cells with SRT3025 diminished their glucagon secretion and proliferative activity in association with a reduction in the α cell associated transcription factor, Aristaless Related Homeobox (Arx). By reducing the paradoxical increase in glucagon, SIRT1 activation may offer a new, α-cell centric approach to the treatment of type 1 diabetes.

Epigenetics Control Microglia Plasticity

Microglia, resident immune cells of the central nervous system, fulfill multiple functions in the brain throughout life. These microglial functions range from participation in innate and adaptive immune responses, involvement in the development of the brain and its homeostasis maintenance, to contribution to degenerative, traumatic, and proliferative diseases; and take place in the developing, the aging, the healthy, or the diseased brain. Thus, an impressive level of cellular plasticity, appears as a requirement for the pleiotropic biological functions of microglia. Epigenetic changes, including histone modifications or DNA methylation as well as microRNA expression, are important modifiers of gene expression, and have been involved in cell phenotype regulation and reprogramming and are therefore part of the mechanisms regulating cellular plasticity. Here, we review and discuss the epigenetic mechanisms, which are emerging as contributors to this microglial cellular plasticity and thereby can constitute interesting targets to modulate microglia associated brain diseases, including developmental diseases, neurodegenerative diseases as well as cancer.

Lipopolysaccharide aggravated DOI-induced Tourette syndrome: elaboration for recurrence of Tourette syndrome

Tourette syndrome (TS) is a neurological disorder characterized by highest familial recurrence rate among neuropsychiatric diseases with complicated inheritance. Recurrence of Tourette syndrome was frequently observed in clinical. Unexpectedly, the mechanism of recurrence of Tourette syndrome was failure to elucidate. Here, we first shown that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome. The TS model in rats was induced by DOI (the selective 5-HT2A/2C agonist 1-(2, 5-dimethoxy-4-iodophenyl) -2- aminopropane). The rats were randomly divided into 4 groups:(1)Control;(2) Control + LPS; (2)TS; (3)TS + LPS. The results demonstrated that the LPS treatment significantly increased stereotypic score and autonomic activity. LPS treatment also significantly increased inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in serum and striatum. Also, highly expressed TLR4, MyD88, P-NF-κBp65, P-IκBα in TS rats were increased respectively by LPS treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome and its mechanism was related to TLR/NF-κB pathway.

Glycogen controls Caenorhabditis elegans lifespan and resistance to oxidative stress

A high-sugar diet has been associated with reduced lifespan in organisms ranging from worms to mammals. However, the mechanisms underlying the harmful effects of glucose are poorly understood. Here we establish a causative relationship between endogenous glucose storage in the form of glycogen, resistance to oxidative stress and organismal aging in Caenorhabditis elegans. We find that glycogen accumulated on high dietary glucose limits C. elegans longevity. Glucose released from glycogen and used for NADPH/glutathione reduction renders nematodes and human hepatocytes more resistant against oxidative stress. Exposure to low levels of oxidants or genetic inhibition of glycogen synthase depletes glycogen stores and extends the lifespan of animals fed a high glucose diet in an AMPK-dependent manner. Moreover, glycogen interferes with low insulin signalling and accelerates aging of long-lived daf-2 worms fed a high glucose diet. Considering its extensive evolutionary conservation, our results suggest that glycogen metabolism might also have a role in mammalian aging.

Glycogen is a storage form of glucose in cells. Here, Gusarov et al. show that glycogen-derived glucose can be used to quickly regenerate the antioxidant glutathione and that inhibiting glycogen synthesis extends C. elegans lifespan, whereas glycogen accumulation drives organismal ageing in worms.

The Role of Sirt1 in Epileptogenesis

The mechanisms by which brain insults lead to subsequent epilepsy remain unclear. Insults, including trauma, stroke, tumors, infections, and long seizures [status epilepticus (SE)], create a neuronal state of increased metabolic demand or decreased energy supply. Neurons express molecules that monitor their metabolic state, including sirtuins (Sirts). Sirtuins deacetylate cytoplasmic proteins and nuclear histones, and their epigenetic modulation of the chromatin governs the expression of many genes, influencing neuronal properties. Thus, sirtuins are poised to enduringly modulate neuronal properties following SE, potentially contributing to epileptogenesis, a hypothesis supported by the epilepsy-attenuating effects of blocking a downstream target of Sirt1, Neuron-Restrictive Silencer Factor (NRSF) also know as REST (RE1-Silencing Transcription factor). Here we used an adult male rat model of epileptogenesis provoked by kainic acid-induced SE (KA-SE). We assessed KA-SE-provoked Sirt1 activity, infused a Sirt1 inhibitor (EX-527) after KA-SE, and examined for epileptogenesis using continuous digital video-EEG. Sirt1 activity, measured using chromatin immunoprecipitation for Sirt1 binding at a target gene, increased rapidly after SE. Post hoc infusion of the Sirt1 inhibitor prevented Sirt1-mediated repression of a target gene. Blocking Sirt1 activity transiently after KA-SE did not significantly influence the time- course and all of the parameters of epilepsy development. Specifically, latency to first seizure and seizure number, duration, and severity (using the Racine scale and EEG measures) as well as the frequency and duration of interictal spike series, were all unchanged. KA-SE provoked a robust inflammatory response and modest cell loss, yet neither was altered by blocking Sirt1. In conclusion, blocking Sirt1 activity after KA-SE does not abrogate epilepsy development, suggesting that the mechanisms of such acquired epileptogenesis are independent of Sirt1 function.

Short-term starvation attenuates liver ischemia-reperfusion injury (IRI) by Sirt1-autophagy signaling in mice

Calorie restriction or starvation (fasting) has some beneficial effects in terms of prolonging life and increasing resistance to stress. It has also been shown that calorie restriction has a protective role during ischemia-reperfusion injury (IRI) in several organs, but the underlying mechanism has not been elucidated. In this study we investigated the effects and molecular mechanisms of short-term starvation (STS) on liver IRI in a mouse liver IRI model. We found that STS significantly attenuated liver IRI in this model, as evidenced by inhibition of serum aminotransferase levels, and decreased pathological damage and hepatocellular apoptosis, especially after 2- or 3-day starvation. Furthermore, we found that 2- or 3-day starvation induced expression of hepatocellular autophagy in vivo and in vitro. Further experiments provided support for the notion that STS-induced autophagy played a key role during starvation-regulated protection against liver IRI via autophagy inhibition with 3-methyladenine. Interestingly, the longevity gene Sirt1 was also significantly up-regulated in liver after STS. Importantly, inhibition of Sirt1 by sirtinol abolished STS-induced autophagy and further abrogated STS-mediated protection against liver IRI. In conclusion, our results indicate that STS attenuates liver IRI via the Sirt1-autophagy pathway. Our findings provide a rationale for a novel therapeutic strategy for managing liver IRI.

Epigenetic Mechanisms of Longevity and Aging

Aging is an inevitable outcome of life, characterized by progressive decline in tissue and organ function and increased risk of mortality. Accumulating evidence links aging to genetic and epigenetic alterations. Given the reversible nature of epigenetic mechanisms, these pathways provide promising avenues for therapeutics against age-related decline and disease. In this review, we provide a comprehensive overview of epigenetic studies from invertebrate organisms, vertebrate models, tissues, and in vitro systems. We establish links between common operative aging pathways and hallmark chromatin signatures that can be used to identify "druggable" targets to counter human aging and age-related disease.

The effects of graded levels of calorie restriction: III. Impact of short term calorie and protein restriction on mean daily body temperature and torpor use in the C57BL/6 mouse

A commonly observed response in mammals to calorie restriction (CR) is reduced body temperature (T_b). We explored how the T_b of male C57BL/6 mice responded to graded CR (10 to 40%), compared to the response to equivalent levels of protein restriction (PR) over 3 months. Under CR there was a dynamic change in daily T_b over the first 30–35 days, which stabilized thereafter until day 70 after which a further decline was noted. The time to reach stability was dependent on restriction level. Body mass negatively correlated with T_b under ad libitum feeding and positively correlated under CR. The average T_b over the last 20 days was significantly related to the levels of body fat, structural tissue, leptin and insulin-like growth factor-1. Some mice, particularly those under higher levels of CR, showed periods of daily torpor later in the restriction period. None of the changes in T_b under CR were recapitulated by equivalent levels of PR. We conclude that changes in T_b under CR are a response only to the shortfall in calorie intake. The linear relationship between average T_b and the level of restriction supports the idea that T_b changes are an integral aspect of the lifespan effect.

The Frequency of Fish-Eating Could Negatively Associate with Visceral Adiposity in Those Who Eat Moderately

Visceral fat accumulation is regarded as one of the major phenotypes of metabolic syndrome. There have not been enough data on the relationship between the fish-eating habit and visceral adiposity. A total of 94 male participants received abdominal CT for the measurement of the visceral fat area (VFA), serum sampling for the fatty acid composition and questionnaires about their life-style. We divided the participants into two groups: whether they ate their fill (group F, n=70) or they ate in moderation (group M, n=24). Stepwise multiple linear regression analyses showed that usual alcohol consumption and lower daily physical activity in group F, and infrequent fish-eating and frequent fat-rich deserts in group M were the significant positive correlates with the VFA. The serum eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio showed significant correlation with the frequency of fish-eating in both groups. Interestingly, in group M, the serum EPA/AA ratio negatively correlated with the VFA, while it failed in group F. In conclusion, the present data suggest that the fish-eating habit might negatively associate with visceral fat accumulation only in those who are moderate in eating in the general population.

Age-Related Changes in Sirtuin 7 Expression in Calorie-Restricted and Refed Rats

Background: Sirtuins (SIRT1-7) have been implicated to mediate the beneficial effects of calorie restriction for healthy aging. While the physiological functions of SIRT7 are still poorly understood, SIRT7 has recently been shown to affect ribosome biogenesis, mitochondrial gene expression, and hepatic lipid metabolism. Objective: To analyze the effects of age and short-term calorie restriction (SCR) and subsequent refeeding on SIRT7 expression in key metabolic tissues. Methods: Four- and 24-month-old male Wistar rats were subjected to 40% SCR for 30 days, followed by ad libitum feeding for 2 or 4 days. Liver, white adipose tissue (WAT), heart and skeletal muscle samples were analyzed by real-time PCR and Western blotting for SIRT7 mRNA and protein expression, respectively. Results: Aging had diverse effects on SIRT7 levels in lipogenic tissues: both the mRNA and protein levels increased in the retroperitoneal depot (rWAT), did not change in the epididymal depot (eWAT), and decreased in the subcutaneous depot (sWAT) and the liver of old as compared to young animals. In the heart, extensor digitorum longus muscle (EDL) and soleus muscle (SOL), Sirt7 gene but not protein expression was lower in old than in young control rats. SCR did not affect SIRT7 expression in WAT and the liver in both age groups. In the heart of young animals, SCR did not affect SIRT7 mRNA or protein level. In EDL, SIRT7 protein but not mRNA levels decreased after SCR and remained reduced upon refeeding. In SOL, both SIRT7 mRNA and protein expression were inhibited by refeeding. In old rats, cardiac Sirt7 expression increased after SCR and refeeding. In old rats' EDL and SOL muscles, SIRT7 protein expression was inhibited by refeeding. Conclusion: Age-related changes of SIRT7 gene expression in key organs of energy homeostasis are tissue dependent.

The daily rhythms of mitochondrial gene expression and oxidative stress regulation are altered by aging in the mouse liver

The circadian clock regulates many cellular processes, notably including the cell cycle, metabolism and aging. Mitochondria play essential roles in metabolism and are the major sites of reactive oxygen species (ROS) production in the cell. The clock regulates mitochondrial functions by driving daily changes in NAD(+) levels and Sirt3 activity. In addition to this central route, in the present study, we find that the expression of some mitochondrial genes is also rhythmic in the liver, and that there rhythms are disrupted by the Clock(Δ19) mutation in young mice, suggesting that they are regulated by the core circadian oscillator. Related to this observation, we also find that the regulation of oxidative stress is rhythmic in the liver. Since mitochondria and ROS play important roles in aging, and mitochondrial functions are also disturbed by aging, these related observations prompt the compelling hypothesis that circadian oscillators influence aging by regulating ROS in mitochondria. During aging, the expression rhythms of some mitochondrial genes were altered in the liver and the temporal regulation over the dynamics of mitochondrial oxidative stress was disrupted. However, the expression of clock genes was not affected. Our results suggested that mitochondrial functions are combinatorially regulated by the clock and other age-dependent mechanism(s), and that aging disrupts mitochondrial rhythms through mechanisms downstream of the clock.

de Bruin R, N. M. Ijzermans J, van Kooten C, Dor FJMF. Mannan-Binding Lectin Is Involved in the Protection against Renal Ischemia/Reperfusion Injury by Dietary Restriction

Preoperative fasting and dietary restriction offer robust protection against renal ischemia/reperfusion injury (I/RI) in mice. We recently showed that Mannan-binding lectin (MBL), the initiator of the lectin pathway of complement activation, plays a pivotal role in renal I/RI. Based on these findings, we investigated the effect of short-term DR (30% reduction of total food intake) or three days of water only fasting on MBL in 10-12 weeks old male C57/Bl6 mice. Both dietary regimens significantly reduce the circulating levels of MBL as well as its mRNA expression in liver, the sole production site of MBL. Reconstitution of MBL abolished the protection afforded by dietary restriction, whereas in the fasting group the protection persisted. These data show that modulation of MBL is involved in the protection against renal I/RI induced by dietary restriction, and suggest that the mechanisms of protection induced by dietary restriction and fasting may be different.

SIRT1 affects DNA methylation of polycomb group protein target genes, a hotspot of the epigenetic shift observed in ageing

BACKGROUND

SIRT1 is likely to play a role in the extension in healthspan induced by dietary restriction. Actions of SIRT1 are pleiotropic, and effects on healthspan may include effects on DNA methylation. Polycomb group protein target genes (PCGTs) are suppressed by epigenetic mechanisms in stem cells, partly through the actions of the polycomb repressive complexes (PRCs), and have been shown previously to correspond with loci particularly susceptible to age-related changes in DNA methylation. We hypothesised that SIRT1 would affect DNA methylation particularly at PCGTs. To map the sites in the genome where SIRT1 affects DNA methylation, we altered SIRT1 expression in human intestinal (Caco-2) and vascular endothelial (HuVEC) cells by transient transfection with an expression construct or with siRNA. DNA was enriched for the methylated fraction then sequenced (HuVEC) or hybridised to a human promoter microarray (Caco-2).

RESULTS

The profile of genes where SIRT1 manipulation affected DNA methylation was enriched for PCGTs in both cell lines, thus supporting our hypothesis. SIRT1 knockdown affected the mRNA for none of seven PRC components nor for DNMT1 or DNMT3b. We thus find no evidence that SIRT1 affects DNA methylation at PCGTs by affecting the expression of these gene transcripts. EZH2, a component of PRC2 that can affect DNA methylation through association with DNA methyltransferases (DNMTs), did not co-immunoprecipitate with SIRT1, and SIRT1 knockdown did not affect the expression of EZH2 protein. Thus, it is unlikely that the effects of SIRT1 on DNA methylation at PCGTs are mediated through direct intermolecular association with EZH2 or through effects in its expression.

CONCLUSIONS

SIRT1 affects DNA methylation across the genome, but particularly at PCGTs. Although the mechanism through which SIRT1 has these effects is yet to be uncovered, this action is likely to contribute to extended healthspan, for example under conditions of dietary restriction.

SIRT1 deficiency in microglia contributes to cognitive decline in aging and neurodegeneration via epigenetic regulation of IL-1β

Aging is the predominant risk factor for neurodegenerative diseases. One key phenotype as the brain ages is an aberrant innate immune response characterized by proinflammation. However, the molecular mechanisms underlying aging-associated proinflammation are poorly defined. Whether chronic inflammation plays a causal role in cognitive decline in aging and neurodegeneration has not been established. Here we report a mechanistic link between chronic inflammation and aging microglia and a causal role of aging microglia in neurodegenerative cognitive deficits. We showed that SIRT1 is reduced with the aging of microglia and that microglial SIRT1 deficiency has a causative role in aging- or tau-mediated memory deficits via IL-1β upregulation in mice. Interestingly, the selective activation of IL-1β transcription by SIRT1 deficiency is likely mediated through hypomethylating the specific CpG sites on IL-1β proximal promoter. In humans, hypomethylation of IL-1β is strongly associated with chronological age and with elevated IL-1β transcription. Our findings reveal a novel epigenetic mechanism in aging microglia that contributes to cognitive deficits in aging and neurodegenerative diseases.

Schistosome sirtuins as drug targets

The sirtuins form a superfamily of evolutionarily conserved NAD+-dependent protein N-ϵ-acyl-lysine (AcK) deacylases with roles in a variety of key cellular processes. Sirtuins have a broadly conserved overall structure with a catalytic site formed by a hydrophobic channel between the NAD+-binding Rossmann fold domain and a smaller Zn2+-binding domain. Schistosomes express five members of the sirtuin family and generic sirtuin inhibitors induce apoptosis and death in schistosome larvae, the disruption of adult worm pairs, inhibition of egg laying and damage to the male and female worm reproductive systems. Sirtuins in schistosomes and other parasitic flatworms present structural differences from their human orthologues that should allow the development of selective inhibitors that can be developed as drug leads.

Aging and brain rejuvenation as systemic events

The effects of aging were traditionally thought to be immutable, particularly evident in the loss of plasticity and cognitive abilities occurring in the aged central nervous system (CNS). However, it is becoming increasingly apparent that extrinsic systemic manipulations such as exercise, caloric restriction, and changing blood composition by heterochronic parabiosis or young plasma administration can partially counteract this age-related loss of plasticity in the aged brain. In this review, we discuss the process of aging and rejuvenation as systemic events. We summarize genetic studies that demonstrate a surprising level of malleability in organismal lifespan, and highlight the potential for systemic manipulations to functionally reverse the effects of aging in the CNS. Based on mounting evidence, we propose that rejuvenating effects of systemic manipulations are mediated, in part, by blood-borne ‘pro-youthful’ factors. Thus, systemic manipulations promoting a younger blood composition provide effective strategies to rejuvenate the aged brain. As a consequence, we can now consider reactivating latent plasticity dormant in the aged CNS as a means to rejuvenate regenerative, synaptic, and cognitive functions late in life, with potential implications even for extending lifespan.