Increased dosage of a sir-2 gene extends lifespan in Caenorhabditis elegans

MPK-1/ERK is required for the full activity of resveratrol in extended lifespan and reproduction

Resveratrol (RSV) extends the lifespan of various organisms through activation of sirtuin. However, whether RSV-mediated longevity is entirely dependent upon sirtuin is still controversial. Thus, understanding additional mechanisms concerning the genetic requirements for the biological activity of RSV needs to be clarified to utilize the beneficial effects of RSV. In this study using Caenorhabditis elegans as a model system, we found that MPK-1 (an ERK homolog) signaling is necessarily required for RSV-mediated longevity of sir-2.1/sirtuin mutants as well as for wild-type worms. We demonstrated that MPK-1 contributes to RSV-mediated longevity through nuclear accumulation of SKN-1 in a SIR-2.1/DAF-16 pathway-independent manner. The positive effect of RSV in regulating lifespan was completely abolished by RNA interference against mpk-1 in the sir-2.1 and daf-16 mutants, strongly indicating that the MPK-1/SKN-1 pathway is involved in RSV-mediated longevity, independently of SIR-2.1/DAF-16. We additionally found that RSV protected worms from oxidative stress via MPK-1. In addition to organismal aging, RSV prevented the age-associated loss of mitotic germ cells, brood size, and reproductive span through MPK-1 in C. elegans germline. Therefore, our findings not only provide new mechanistic insight into the controversial effects of RSV on organismal longevity, but additionally have important implications in utilizing RSV to improve the outcome of aging-related diseases.

Epigenetic Regulation of Bone Marrow Stem Cell Aging: Revealing Epigenetic Signatures associated with Hematopoietic and Mesenchymal Stem Cell Aging

In this review we explore the importance of epigenetics as a contributing factor for aging adult stem cells. We summarize the latest findings of epigenetic factors deregulated as adult stem cells age and the consequence on stem cell self-renewal and differentiation, with a focus on adult stem cells in the bone marrow. With the latest whole genome bisulphite sequencing and chromatin immunoprecipitations we are able to decipher an emerging pattern common for adult stem cells in the bone marrow niche and how this might correlate to epigenetic enzymes deregulated during aging. We begin by briefly discussing the initial observations in yeast, drosophila and Caenorhabditis elegans (C. elegans) that led to the breakthrough research that identified the role of epigenetic changes associated with lifespan and aging. We then focus on adult stem cells, specifically in the bone marrow, which lends strong support for the deregulation of DNA methyltransferases, histone deacetylases, acetylates, methyltransferases and demethylases in aging stem cells, and how their corresponding epigenetic modifications influence gene expression and the aging phenotype. Given the reversible nature of epigenetic modifications we envisage “epi” targeted therapy as a means to reprogram aged stem cells into their younger counterparts.

3-Methyl-3-buten-1-ol (isoprenol) confers longevity and stress tolerance in Caenorhabditis elegans

The present investigation demonstrates the longevity-promoting effects of 3-methyl-3-buten-1-ol (isoprenol) in the animal model Caenorhabditis elegans that might be served as a lead nutraceutical in geriatric research. Our results showed that 0.5 mM isoprenol extended the mean lifespan of worms by 25% in comparison to control worms. Isoprenol also significantly enhanced survival of the worms under various stress conditions. It was found that the longevity-promoting effects of isoprenol were associated with improved age-associated physiological behaviour and reduced intracellular reactive oxygen species (ROS) accumulation. Finally, studies with gene-specific mutants revealed the involvement of pro-longevity transcription factors (TFs) DAF-16 and SKN-1 with simultaneous over-expression of GST-4 and SOD-3 in isoprenol treated worms. In silico analysis revealed the binding affinity of isoprenol with DAF-16 and SKN-1 TFs. Together, the findings suggest that isoprenol is able to enhance the lifespan of C. elegans and embarks its potential in the developments of formulations for age-related ailments.

Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity

NAD⁺ acts as a crucial regulator of cell physiology and as an integral participant in cellular metabolism. By virtue of a variety of signaling activities this central metabolite can exert profound effects on organism health status. Thus, while it serves as a well-known metabolic cofactor functioning as a redox-active substrate, it can also function as a substrate for signaling enzymes, such as sirtuins, poly (ADP-ribosyl) polymerases, mono (ADP-ribosyl) transferases, and CD38. Sirtuins function as NAD⁺-dependent protein deacetylases (deacylases) and catalyze the reaction of NAD⁺ with acyllysine groups to remove the acyl modification from substrate proteins. This deacetylation provides a regulatory function and integrates cellular NAD⁺ metabolism into a large spectrum of cellular processes and outcomes, such as cell metabolism, cell survival, cell cycle, apoptosis, DNA repair, mitochondrial homeostasis and mitochondrial biogenesis, and even lifespan. Increased attention to how regulated and pharmacologic changes in NAD⁺ concentrations can impact sirtuin activities has motivated openings of new areas of research, including investigations of how NAD⁺ levels are regulated at the subcellular level, and searches for more potent NAD⁺ precursors typified by nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). This review describes current results and thinking of how NAD⁺ metabolic pathways regulate sirtuin activities and how regulated NAD⁺ levels can impact cell physiology. In addition, NAD⁺ precursors are discussed, with attention to how these might be harnessed to generate novel therapeutic options to treat the diseases of aging.

Yeast at the Forefront of Research on Ageing and Age-Related Diseases

Ageing is a complex and multifactorial process driven by genetic, environmental and stochastic factors that lead to the progressive decline of biological systems. Mechanisms of ageing have been extensively investigated in various model organisms and systems generating fundamental advances. Notably, studies on yeast ageing models have made numerous and relevant contributions to the progress in the field. Different longevity factors and pathways identified in yeast have then been shown to regulate molecular ageing in invertebrate and mammalian models. Currently the best candidates for anti-ageing drugs such as spermidine and resveratrol or anti-ageing interventions such as caloric restriction were first identified and explored in yeast. Yeasts have also been instrumental as models to study the cellular and molecular effects of proteins associated with age-related diseases such as Parkinson's, Huntington's or Alzheimer's diseases. In this chapter, a review of the advances on ageing and age-related diseases research in yeast models will be made. Particular focus will be placed on key longevity factors, ageing hallmarks and interventions that slow ageing, both yeast-specific and those that seem to be conserved in multicellular organisms. Their impact on the pathogenesis of age-related diseases will be also discussed.

Metabolic Biomarkers in Nematode C. elegans During Aging

Changes in energy metabolism occur not only in diseases such as cancer but also in the normal development and aging processes of various organisms. These metabolic changes result to lead to imbalances in energy metabolism related to cellular and tissue homeostasis. In the model organism C. elegans, which is used to study aging, an imbalance in age-related energy metabolism exists between mitochondrial oxidative phosphorylation and aerobic glycolysis. Cellular lactate and pyruvate are key intermediates in intracellular energy metabolic pathways and can indicate age-related imbalances in energy metabolism. Thus, the cellular lactate/pyruvate ratio can be monitored as a biomarker during aging. Moreover, recent studies have proposed a candidate novel biomarker for aging and age-related declines in the nematode C. elegans.

Prospects of Pharmacological Interventions to Organismal Aging

Intense research in the areas of cellular and organismal aging using diverse laboratory model systems has enriched our knowledge in the processes and the signalling pathways involved in normal and pathological conditions. The field finds itself in a position to take decisive steps towards clinical applications and interventions not only for targeted age-related diseases such as cardiovascular conditions and neurodegeneration but also for the modulation of health span and lifespan of a whole organism. Beyond nutritional interventions such as dietary restriction without malnutrition and various regimes of intermittent fasting, accumulating evidence provides promise for pharmacological interventions. The latter, mimic caloric or dietary restriction, tune cellular and organismal stress responses, affect the metabolism of microbiome with subsequent effects on the host or modulate repair pathways, among others. In this mini review, we summarise some of the evidence on drugs that can alter organismal lifespan and the prospects they might offer for promoting healthspan and delaying age-related diseases.

Poly(ADP-Ribose) Polymerases in Host-Pathogen Interactions, Inflammation, and Immunity

The literature review presented here details recent research involving members of the poly(ADP-ribose) polymerase (PARP) family of proteins. Among the 17 recognized members of the family, the human enzyme PARP1 is the most extensively studied, resulting in a number of known biological and metabolic roles. This review is focused on the roles played by PARP enzymes in host-pathogen interactions and in diseases with an associated inflammatory response. In mammalian cells, several PARPs have specific roles in the antiviral response; this is perhaps best illustrated by PARP13, also termed the zinc finger antiviral protein (ZAP). Plant stress responses and immunity are also regulated by poly(ADP-ribosyl)ation. PARPs promote inflammatory responses by stimulating proinflammatory signal transduction pathways that lead to the expression of cytokines and cell adhesion molecules. Hence, PARP inhibitors show promise in the treatment of inflammatory disorders and conditions with an inflammatory component, such as diabetes, arthritis, and stroke. These functions are correlated with the biophysical characteristics of PARP family enzymes. This work is important in providing a comprehensive understanding of the molecular basis of pathogenesis and host responses, as well as in the identification of inhibitors. This is important because the identification of inhibitors has been shown to be effective in arresting the progression of disease.

Study of expression analysis of SIRT4 and the coordinate regulation of bovine adipocyte differentiation by SIRT4 and its transcription factors

Sirtuins, NAD⁺-dependent deacylases and ADP-ribosyltransferases, are critical regulators of metabolism involved in many biological processes, and are involved in mediating adaptive responses to the cellular environment. SIRT4 is a mitochondrial sirtuin and has been shown to play a critical role in maintaining insulin secretion and glucose homeostasis. As a regulator of lipid homeostasis, SIRT4 can repress fatty acid oxidation and promote lipid anabolism in nutrient-replete conditions. Using real-time quantitative PCR (qPCR) to explore the molecular mechanisms of transcriptional regulation of bovine SIRT4 during adipocyte differentiation, we found that bovine SIRT4 is expressed at high levels in bovine subcutaneous adipose tissue. SIRT4 knockdown led to decreased expression of adipogenic differentiation marker genes during adipocyte differentiation. The core promoter of bovine SIRT4 was identified in the −402/−60 bp region of the cloned 2-kb fragment containing the 5′-regulatory region. Binding sites were identified in this region for E2F transcription factor-1 (E2F1), CCAAT/enhancer-binding protein β (CEBPβ), homeobox A5 (HOXA5), interferon regulatory factor 4 (IRF4), paired box 4 (PAX4), and cAMP responsive element-binding protein 1 (CREB1) by using Electrophoretic mobility shift assay (EMSA) and luciferase reporter gene assay. We also found that E2F1, CEBPβ, and HOXA5 transcriptionally activate SIRT4 expression, whereas, IRF4, PAX4, and CREB1 transcriptionally repress SIRT4 expression. We further verified that SIRT4 knockdown could affect the ability of these transcription factors (TFs) to regulate the differentiation of bovine adipocytes. In conclusion, our results shed light on the mechanisms underlying the transcriptional regulation of SIRT4 expression in bovine adipocytes.

Protective Effect of Hydrogen on Sodium Iodate-Induced Age-Related Macular Degeneration in Mice

Oxidative stress is one of the main causes of AMD. Hydrogen has anti-oxidative stress and apoptotic effects on retinal injury. However, the effect of hydrogen on AMD is not clear. In this study, fundus radiography, OCT, and FFA demonstrated that HRW reduced the deposition of drusen-like structures in RPE layer, prevented retina from thinning and leakage of ocular fundus vasculature induced by NaIO₃. ERG analysis confirmed that HRW effectively reversed the decrease of a-wave and b-wave amplitude in NaIO₃-mice. Mechanistically, HRW greatly reduced the oxidative stress reaction through decreased MDA levels, increased SOD production, and decreased ROS content. The OGG1 expression was downregulated which is a marker of oxidative stress. Involvement of oxidative stress was confirmed using oxidative stress inhibitor ALCAR. Moreover, oxidative stress reaction was associated with expression of Sirt1 level and HRW significantly inhibited the downregulation of Sirt1 expression. This result was further confirmed with AICAR which restore Sirt1 expression and activity. In addition, NaIO₃-induced retinal damage was related to apoptosis via caspase 8 and caspase 9, but not the caspase 3 pathways, which led to upregulation of Bax and p53, downregulation of Bcl-2, and increase in Jc-1-positive cells in mice. However, HRW effectively reversed these effects that apoptosis induced. These results suggest that HRW protects retinal functions against oxidative stress injury through inhibiting downregulation of Sirt1 and reducing retinal apoptosis. Therefore, we speculated that hydrogen administration is a promising treatment for AMD therapy.

Cellular senescence in intervertebral disc aging and degeneration

PURPOSE

Age is a major risk factor for multiple disease pathologies, including chronic back pain, which stems from age-related degenerative changes to intervertebral disc tissue. Growing evidence suggest that the change in phenotype of disc cells to a senescent phenotype may be one of the major driving forces of age-associated disc degeneration. This review discusses the known stressors that promote development of senescence in disc tissue and the underlying molecular mechanisms disc cells adopt to enable their transition to a senescent phenotype.

RECENT FINDINGS

Increased number of senescent cells have been observed with advancing age and degeneration in disc tissue. Additionally, in vitro studies have confirmed the catabolic nature of stress-induced senescent disc cells. Several factors have been shown to establish senescence via multiple different underlying mechanisms.

SUMMARY

Cellular senescence can serve as a therapeutic target to combat age-associated disc degeneration. However, whether the different stressors utilizing different signaling networks establish different kinds of senescent types in disc cells is currently unknown and warrants further investigation.

Toxic effect of the novel chiral insecticide IPP and its biodegradation intermediate in nematode Caenorhabditis elegans

Caenorhabditis elegans, a kind of model organism, was used to investigate biodegradation pathway of IPP and M1 in nematodes, in vivo toxicity from IPP and M1 and the possible underlying molecular mechanism. The results showed that both IPP and M1 could decrease lifespan, locomotion behavior, reproductive ability and AChE activity. During IPP biodegradation process, three intermediates (M1-M3) were monitored and identified. Based on the identified metabolites and their biodegradation courses, a possible biodegradation pathway was proposed. IPP was probably transformed to different three metabolites in nematodes through oxidation and elimination of methyl and propyl etc. Under the same concentration, IPP had more severe toxicity than M1 on nematodes. IPP and M1 might reduce lifespan and decrease reproductive ability through influencing insulin/IGF signaling pathway and TOR signaling pathway. They could decrease expression levels of daf-16, sgk-1, aak-2, daf-15 and rict-1 genes, which involved in IGF and TOR signaling pathway.

Loss of Sirt2 increases and prolongs a caerulein-induced pancreatitis permissive phenotype and induces spontaneous oncogenic Kras mutations in mice

Mice lacking Sirt2 spontaneously develop tumors in multiple organs, as well as when expressed in combination with oncogenic KrasG12D, leading to pancreatic tumors. Here, we report that after caerulein-induced pancreatitis, Sirt2-deficient mice exhibited an increased inflammatory phenotype and delayed pancreatic tissue recovery. Seven days post injury, the pancreas of Sirt2-/- mice display active inflammation, whereas wild-type mice had mostly recovered. In addition, the pancreas from the Sirt2-/- mice exhibited extensive tissue fibrosis, which was still present at six weeks after exposure. The mice lacking Sirt2 also demonstrated an enhanced whole body pro-inflammatory phenotype that was most obvious with increasing age. Importantly, an accumulation of a cell population with spontaneous cancerous KrasG12D mutations was observed in the Sirt2-/- mice that is enhanced in the recovering pancreas after exposure to caerulein. Finally, transcriptome analysis of the pancreas of the Sirt2-/- mice exhibited a pro-inflammatory genomic signature. These results suggest that loss of Sirt2, as well as increased age, enhanced the immune response to pancreatic injury and induced an inflammatory phenotype permissive for the accumulation of cells carrying oncogenic Kras mutations.

NAD metabolism: Implications in aging and longevity

Nicotinamide adenine dinucleotide (NAD) is an important co-factor involved in numerous physiological processes, including metabolism, post-translational protein modification, and DNA repair. In living organisms, a careful balance between NAD production and degradation serves to regulate NAD levels. Recently, a number of studies have demonstrated that NAD levels decrease with age, and the deterioration of NAD metabolism promotes several aging-associated diseases, including metabolic and neurodegenerative diseases and various cancers. Conversely, the upregulation of NAD metabolism, including dietary supplementation with NAD precursors, has been shown to prevent the decline of NAD and exhibits beneficial effects against aging and aging-associated diseases. In addition, many studies have demonstrated that genetic and/or nutritional activation of NAD metabolism can extend the lifespan of diverse organisms. Collectively, it is clear that NAD metabolism plays important roles in aging and longevity. In this review, we summarize the basic functions of the enzymes involved in NAD synthesis and degradation, as well as the outcomes of their dysregulation in various aging processes. In addition, a particular focus is given on the role of NAD metabolism in the longevity of various organisms, with a discussion of the remaining obstacles in this research field.

Multi-generational effects of lindane on nematode lipid metabolism with disturbances on insulin-like signal pathway

Influences on lipid metabolism and multi-generational obesogenic effects raised new concerns on lipophilic pollutants (e.g., lindane). Yet, the mechanisms remained unanswered. The present study exposed Caenorhabditis elegans to lindane for 4 consecutive generations (F0 to F3) at 1.0 ng/L, and measured effects in the directly exposed generations (F0 to F3), indirectly exposed ones (T1 and T1') and un-exposed ones (T3 and T3'). Lindane stimulated fat storages in all generations. At the biochemical level, lindane stimulated both acetyl-CoA carboxylase (ACC) and carnitine palmitoyl-transferases (CPT) in F0, T1 and T2, while inhibited them in F3, T1' and T3', demonstrating the balance between fatty acid synthesis and its depletion toward fat accumulation over generations. Moreover, lindane caused different effects on insulin among generations. It inhibited insulin in F0 and F3 and exhibited consistent effects on the expression changes of daf-2, sgk-1 and daf-16 genes in insulin-like signal pathway. Lindane also inhibited insulin in T1 and T3 but exhibited consistent effects on the expression changes of daf-2, akt-1 and daf-16. Different roles of sgk-1 and akt-1 indicated the response strategies from tolerance (F0 and F3) to avoidance (T1 and T3). Lindane stimulated insulin in T1' and T3' and exhibited consistent effects on expression changes of daf-2, sgk-1 and daf-16 genes that were similar in F0 and F3.

Transcriptome evidence reveals enhanced autophagy-lysosomal function in centenarians

Centenarians (CENs) are excellent subjects to study the mechanisms of human longevity and healthy aging. Here, we analyzed the transcriptomes of 76 centenarians, 54 centenarian-children, and 41 spouses of centenarian-children by RNA sequencing and found that, among the significantly differentially expressed genes (SDEGs) exhibited by CENs, the autophagy-lysosomal pathway is significantly up-regulated. Overexpression of several genes from this pathway, CTSB, ATP6V0C, ATG4D, and WIPI1, could promote autophagy and delay senescence in cultured IMR-90 cells, while overexpression of the Drosophila homolog of WIPI1, Atg18a, extended the life span in transgenic flies. Interestingly, the enhanced autophagy-lysosomal activity could be partially passed on to their offspring, as manifested by their higher levels of both autophagy-encoding genes and serum beclin 1 (BECN1). In light of the normal age-related decline of autophagy-lysosomal functions, these findings provide a compelling explanation for achieving longevity in, at least, female CENs, given the gender bias in our collected samples, and suggest that the enhanced waste-cleaning activity via autophagy may serve as a conserved mechanism to prolong the life span from Drosophila to humans.

An overview of Sirtuins as potential therapeutic target: Structure, function and modulators

Sirtuin (Yeast Silent Information RegulatorsⅡ, Sir2) was first discovered in the 1970s. Because of its function by removing acetylated groups from histones in the presence of nicotinamide adenine dinucleotide (NAD⁺), waves of research have assessed the potential of Sirtuin as a therapeutic target. The Sirtuin family, which is widely distributed throughout the nature, has been divided into seven human isoforms (Sirt1-Sirt7). They are thought to be closely related to some aging diseases such as cardiovascular disorders, neurodegeneration, and tumors. Herein, we present a comprehensive review of the structure, function and modulators of Sirtuins, which is expected to be beneficial to relevant studies.

MiR-34 inhibits polycomb repressive complex 2 to modulate chaperone expression and promote healthy brain aging

Aging is a prominent risk factor for neurodegenerative disease. Defining gene expression mechanisms affecting healthy brain aging should lead to insight into genes that modulate susceptibility to disease. To define such mechanisms, we have pursued analysis of miR-34 mutants in Drosophila. The miR-34 mutant brain displays a gene expression profile of accelerated aging, and miR-34 upregulation is a potent suppressor of polyglutamine-induced neurodegeneration. We demonstrate that Pcl and Su(z)12, two components of polycomb repressive complex 2, (PRC2), are targets of miR-34, with implications for age-associated processes. Because PRC2 confers the repressive H3K27me3 mark, we hypothesize that miR-34 modulates PRC2 activity to relieve silencing of genes promoting healthful aging. Gene expression profiling of the brains of hypomorphic mutants in Enhancer of zeste (E(z)), the enzymatic methyltransferase component of PRC2, revealed a younger brain transcriptome profile and identified the small heat shock proteins as key genes reduced in expression with age.

miR-34 is known to regulate age-related gene expression in the Drosophila brain, and miR-34 overexpression can attenuate neurodegeneration induced by polyQ-expanded proteins. Here, Kennerdell and colleagues show that miR-34 confers longevity and neuroprotection via an epigenetic regulator Polycomb Repressive Complex 2 and molecular chaperone expression.

BK channel deacetylation by SIRT1 in dentate gyrus regulates anxiety and response to stress

Previous genomic studies in humans indicate that SIRT1, a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase, is involved in anxiety and depression, but the mechanisms are unclear. We previously showed that SIRT1 is highly activated in the nuclear fraction of the dentate gyrus of the chronically stressed animals and inhibits memory formation and increases anhedonic behavior during chronic stress, but specific functional targets of cytoplasmic SIRT1 are unknown. Here, we demonstrate that SIRT1 activity rapidly modulates intrinsic and synaptic properties of the dentate gyrus granule cells and anxiety behaviors through deacetylation of BK channel α subunits in control animals. Chronic stress decreases BKα channel membrane expression, and SIRT1 activity has no rapid effects on synaptic transmission or intrinsic properties in the chronically stressed animal. These results suggest SIRT1 activity rapidly modulates the physiological function of the dentate gyrus, and this modulation participates in the maladaptive stress response.

Diankun Yu et al. show that deacetylase SIRT1 rapidly modulates synaptic properties of the dentate gyrus granule cells and anxiety behaviors through deacetylation of BK channel α subunits. This study provides mechanistic insight into how SIRT1 regulates fight-or-flight stress response.

CCAR-1 is a negative regulator of the heat-shock response in Caenorhabditis elegans

Defects in protein quality control during aging are central to many human diseases, and strategies are needed to better understand mechanisms of controlling the quality of the proteome. The heat-shock response (HSR) is a conserved survival mechanism mediated by the transcription factor HSF1 which functions to maintain proteostasis. In mammalian cells, HSF1 is regulated by a variety of factors including the prolongevity factor SIRT1. SIRT1 promotes the DNA-bound state of HSF1 through deacetylation of the DNA-binding domain of HSF1, thereby enhancing the HSR. SIRT1 is also regulated by various factors, including negative regulation by the cell-cycle and apoptosis regulator CCAR2. CCAR2 negatively regulates the HSR, possibly through its inhibitory interaction with SIRT1. We were interested in studying conservation of the SIRT1/CCAR2 regulatory interaction in Caenorhabditis elegans, and in utilizing this model organism to observe the effects of modulating sirtuin activity on the HSR, longevity, and proteostasis. The HSR is highly conserved in C. elegans and is mediated by the HSF1 homolog, HSF-1. We have uncovered that negative regulation of the HSR by CCAR2 is conserved in C. elegans and is mediated by the CCAR2 ortholog, CCAR-1. This negative regulation requires the SIRT1 homolog SIR-2.1. In addition, knockdown of CCAR-1 via ccar-1 RNAi works through SIR-2.1 to enhance stress resistance, motility, longevity, and proteostasis. This work therefore highlights the benefits of enhancing sirtuin activity to promote the HSR at the level of the whole organism.

Modulating SIRT1 activity variously affects thymic lymphoma development in mice

SIRT1 is a protein deacetylase with a broad range of biological functions, many of which are known to be important in carcinogenesis, however much of the literature regarding the role of SIRT1 in cancer remains conflicting. In this study we assessed the effect of SIRT1 on the initiation and progression of thymic T cell lymphomas. We employed mouse strains in which SIRT1 activity was absent or could be reversibly modulated in conjunction with thymic lymphoma induction using either the N-nitroso-N-methylurea (NMU) carcinogenesis or the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) transgene. Decreased SIRT1 activity reduced the development of thymic lymphomas in the NMU-treated mice but was permissive for the formation of lung adenomas. Conversely, in the NPM-ALK transgenic mice, decreased SIRT1 activity had a modest promoting effect in the development of thymic lymphomas. The results of the work presented here add to the growing body of evidence that sirt1 is neither an outright oncogene nor a tumor suppressor. These opposing results in two models of the same disease suggest that the influence of sirt1 on carcinogenesis may lie in a role in tumor surveillance.

Recent Advances in Behavioral (Epi)Genetics in Eusocial Insects

Eusocial insects live in societies in which distinct family members serve specific roles in maintaining the colony and advancing the reproductive ability of a few select individuals. Given the genetic similarity of all colony members, the diversity of morphologies and behaviors is surprising. Social communication relies on pheromones and olfaction, as shown by mutants of orco, the universal odorant receptor coreceptor, and through electrophysiological analysis of neuronal responses to pheromones. Additionally, neurohormonal factors and epigenetic regulators play a key role in caste-specific behavior, such as foraging and caste switching. These studies start to allow an understanding of the molecular mechanisms underlying social behavior and provide a technological foundation for future studies of eusocial insects. In this review, we highlight recent findings in eusocial insects that advance our understanding of genetic and epigenetic regulations of social behavior and provide perspectives on future studies using cutting-edge technologies.

Killed Bifidobacterium longum enhanced stress tolerance and prolonged life span of Caenorhabditis elegans via DAF-16

Probiotics are bacteria among the intestinal flora that are beneficial for human health. Bifidobacterium longum (BL) is a prototypical probiotic that is widely used in yogurt making, supplements and others. Although various physiological effects of BL have been reported, those associated with longevity and anti-ageing still remain elusive. Here we aimed to elucidate the physiological effects of killed BL (BR-108) on stress tolerance and longevity of Caenorhabditis elegans and their mechanisms. Worms fed killed BL in addition to Escherichia coli (OP50) displayed reduced body length in a BL dose-dependent manner. When compared with those fed E. coli alone, these worms had a higher survival rate following heat stress at 35°C and hydrogen peroxide-induced oxidative stress. A general decrease in motility was observed over time in all worms; however, killed BL-fed ageing worms displayed increased movement and longer life span than those fed E. coli alone. However, the longevity effect was suppressed in sir-2.1, daf-16 and skn-1-deficient worms. Killed BL induced DAF-16 nuclear localisation and increased the expression of the DAF-16 target gene hsp-12.6. These results revealed that the physiological effects of killed BL in C. elegans were mediated by DAF-16 activation. These findings contradict previous observations with different Bifidobacterium and Lactobacillus strains, which showed the role for SKN-1 independently of DAF-16.

Peripheral blood SIRT1 mRNA levels in depression and treatment with electroconvulsive therapy

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD+) dependent enzymes that regulate cellular functions through deacetylation of protein targets. They have roles in both the periphery and central nervous system and have been implicated in depression biology. A recent genome-wide association study has identified a locus for major depression in the Sirtuin1 gene (SIRT1) and lower blood levels of SIRT1 mRNA in patients with depression have also been observed in two studies. To our knowledge, no studies have examined the effect of treatment on SIRT1 levels in patients with depression. We therefore examined SIRT1 mRNA levels in a well characterised group of patients with depression, compared to healthy controls, and characterised the effects of a course of electroconvulsive therapy (ECT) on peripheral blood SIRT1 mRNA. Depressed patients (n = 91) were matched to healthy controls (n = 85) on the basis of age and sex. In line with previous studies, blood SIRT1 mRNA levels were lower in depressed patients in comparison to controls (p = 0.005). However, ECT had no effect on SIRT1 levels (p = 0.67). There was no relationship between baseline pre-ECT SIRT1 levels and depression severity, change in mood scores, suicidality, depression polarity, presence of psychosis, or response to treatment. There was a trend for a negative association between an increase in SIRT1 mRNA and a decrease in HAM-D24 scores in ECT responders and remitters. These results indicate that reduced peripheral blood SIRT1 mRNA could be a trait feature of depression.

Genetic cartography of longevity in humans and mice: Current landscape and horizons

Aging is a complex and highly variable process. Heritability of longevity among humans and other species is low, and this finding has given rise to the idea that it may be futile to search for DNA variants that modulate aging. We argue that the problem in mapping longevity genes is mainly one of low power and the genetic and environmental complexity of aging. In this review we highlight progress made in mapping genes and molecular networks associated with longevity, paying special attention to work in mice and humans. We summarize 40 years of linkage studies using murine cohorts and 15 years of studies in human populations that have exploited candidate gene and genome-wide association methods. A small but growing number of gene variants contribute to known longevity mechanisms, but a much larger set have unknown functions. We outline these and other challenges and suggest some possible solutions, including more intense collaboration between research communities that use model organisms and human cohorts. Once hundreds of gene variants have been linked to differences in longevity in mammals, it will become feasible to systematically explore gene-by-environmental interactions, dissect mechanisms with more assurance, and evaluate the roles of epistasis and epigenetics in aging. A deeper understanding of complex networks-genetic, cellular, physiological, and social-should position us well to improve healthspan.

Glucosamine Extends the Lifespan of Caenorhabditis elegans via Autophagy Induction

Glucosamine (GlcN) is commonly used as a dietary supplement to promote cartilage health in humans. We previously reported that GlcN could induce autophagy in cultured mammalian cells. Autophagy is known to be involved in the prevention of various diseases and aging. Here, we showed that GlcN extended the lifespan of the nematode Caenorhabditis elegans by inducing autophagy. Autophagy induction by GlcN was demonstrated by western blotting for LGG-1 (an ortholog of mammalian LC3) and by detecting autophagosomal dots in seam cells by fluorescence microscopy. Lifespan assays revealed that GlcN-induced lifespan extension was achieved with at least 5 mM GlcN. A maximum lifespan extension of approximately 30 % was achieved with 20 mM GlcN (p<0.0001). GlcN-induced lifespan extension was not dependent on the longevity genes daf-16 and sir-2.1 but dependent on the autophagy-essential gene atg-18. Therefore, we suggest that oral administration of GlcN could help delay the aging process via autophagy induction.

The Role of SIRT3 in the Brain Under Physiological and Pathological Conditions

Sirtuin enzymes are a family of highly seven conserved protein deacetylases, namely SIRT1 through SIRT7, whose enzymatic activities require the cofactor nicotinamide adenine dinucleotide (NAD⁺). Sirtuins reside in different compartments within cells, and their activities have been shown to regulate a number of cellular pathways involved in but not limited to stress management, apoptosis and inflammatory responses. Given the importance of mitochondrial functional state in neurodegenerative conditions, the mitochondrial SIRT3 sirtuin, which is the primary deacetylase within mitochondria, has garnered considerable recent attention. It is now clear that SIRT3 plays a major role in regulating a host of mitochondrial molecular cascades that can contribute to both normal and pathophysiological processes. However, most of the currently available knowledge on SIRT3 stems from studies in non-neuronal cells, and the consequences of the interactions between SIRT3 and its targets in the CNS are only beginning to be elucidated. In this review, we will summarize current advances relating to SIRT3, and explore how its known functions could influence brain physiology.

ROS is the major player in regulating altered autophagy and lifespan in sin-3 mutants of C. elegans

SIN3, a transcriptional corepressor has been implicated in varied functions both as transcription activator and repressor. Recent studies associated Sin3 with the macroautophagic/autophagic process as a negative regulator of Atg8 and Atg32. Though the role of SIN3 in autophagy is being explored, little is known about the overall effect of SIN3 deletion on the survival of an organism. In this study using a Caenorhabditis elegans sin-3(tm1279);him-5(e1490) strain, we demonstrate that under in vivo conditions SIN-3 differentially modulates autophagy and lifespan. We provide evidence that the enhanced autophagy and decreased lifespan observed in sin-3 deletion mutants is dependent on ROS and intracellular oxidative stress. Inability of the mutant worms to maintain redox balance along with dysregulation of enzymatic antioxidants, depletion of GSH and NADP reserves and elevation of ROS markers compromises the longevity of the worms. It is possible that the enhanced autophagic process observed in sin-3(tm1279);him-5(e1490) worms is required to compensate for oxidative stress generated in these worms.

ABBREVIATIONS

cat: catalase; DCFDA: 2',7'-dichlorodihydrofluoroscein diacetate; GSH: reduced glutathione; GSSG: oxidized glutathione; H2O2: hydrogen peroxide; HDAC: Histone deacetylase; HID: HDAC interacting domain; him-5: high incidence of males; HLH-30: Helix Loop Helix-30; HNE: 4-hydroxyl-2-noneal; LIPL: LIPase Like; MDA: malondialdehyde; NGM: nematode growth medium; PAH: paired amphipathic α-helix; PE: phosphatidylethanolamine; RFU: relative fluorescence unit; ROS: reactive oxygen species; sin-3/SIN3: yeast Switch Independent; SOD: superoxide dismutase; NADP: nicotinamide adenine dinucleotide phosphate; SQST-1: SeQueSTosome related-1; ATG: AuTophaGy related.

Detection of Sirtuin-1 protein expression in peripheral blood leukocytes in dogs

Sirtuin-1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase with a large number of protein substrates. It has attracted a lot of attention in association with extending lifespan. The objective of this study was to enable the evaluation of SIRT1 expression in peripheral blood mononuclear cells (PBMCs) from dogs by flow cytometry. Three transcript variants were amplified from PBMCs by reverse transcription PCR and the nucleotide sequences were analyzed. On the basis of deduced amino acid sequence, a monoclonal antibody against human SIRT1, 1F3, was selected to detect canine SIRT1. Canine SIRT1 in peripheral blood mononuclear cells was successfully detected by western blotting using this antibody. Intracellular canine SIRT1 was also detected in permeabilized 293T cells transfected with a canine SIRT1 expression plasmid by flow cytometry using this antibody. SIRT1 was detected in all leukocyte subsets including lymphocytes, granulocytes and monocytes. The expression level was markedly different among individual dogs. These results indicated that the method applied in this study is useful for evaluating canine SIRT1 levels in PBMCs from dogs.

Involvement of Flavonoids from the Leaves of Carya cathayensis Sarg. in Sirtuin 1 Expression in HUVEC Senescence

Atherosclerosis is the commonest cause of death in the world and one of the most important processes that occurs with increasing age because it is accompanied by progressive endothelial dysfunction. Recent studies demonstrated that Sirtuin 1 (SIRT1) might potentially affect cell senescence. However, the effect of SIRT1 on the regulation of human umbilical vein endothelial cell (HUVEC) senescence with total flavonoids (TFs) has not been addressed previously. This study investigated how SIRT1 functions in the process of HUVEC senescence when TFs are present and identified the potential molecular mechanisms involved. Using a model of HUVEC senescence induced by angiotensin II, TFs pretreatment reduced the percentage of senescence-associated β-galactosidase (SA-β-gal) cells and p53 mRNA expression. The level of SIRT1 protein and E2F1 decreased during HUVEC senescence and could be partially recovered when cells were coincubated with TFs, while the levels of proteins p53 and p21 increased during cell senescence and diminished in response to the TFs treatment. When coincubated with 20 mM nicotinamide, the results with SA-β-gal-positive cells and the expression of SIRT1, E2F1, p53, and p21 were contrary to that obtained with only TFs pretreatment. The data indicate that the TFs exert their effect on HUVEC senescence through SIRT1.

Sir-2.1 mediated attenuation of α-synuclein expression by Alaskan bog blueberry polyphenols in a transgenic model of Caenorhabditis elegans

Misfolding and accumulation of cellular protein aggregates are pathological hallmarks of aging and neurodegeneration. One such protein is α-synuclein, which when misfolded, forms aggregates and disrupts normal cellular functions of the neurons causing Parkinson's disease. Nutritional interventions abundant in pharmacologically potent polyphenols have demonstrated a therapeutic role for combating protein aggregation associated with neurodegeneration. The current study hypothesized that Alaskan bog blueberry (Vaccinum uliginosum), which is high in polyphenolic content, will reduce α-synuclein expression in a model of Caenorhabditis elegans (C. elegans). We observed that blueberry extracts attenuated α-synuclein protein expression, improved healthspan in the form of motility and restored lipid content in the transgenic strain of C. elegans expressing human α-synuclein. We also found reduced gene expression levels of sir-2.1 (ortholog of mammalian Sirtuin 1) in blueberry treated transgenic animals indicating that the beneficial effects of blueberries could be mediated through partial reduction of sirtuin activity. This therapeutic effect of the blueberries was attributed to its xenohormetic properties. The current results highlight the role of Alaskan blueberries in mediating inhibition of sir-2.1 as a novel therapeutic approach to improving pathologies of protein misfolding diseases. Finally, our study warrants further investigation of the structure, and specificity of such small molecules from indigenous natural compounds and its role as sirtuin regulators.

Unveiling "Musica Universalis" of the Cell: A Brief History of Biological 12-Hour Rhythms

"Musica universalis" is an ancient philosophical concept claiming the movements of celestial bodies follow mathematical equations and resonate to produce an inaudible harmony of music, and the harmonious sounds that humans make were an approximation of this larger harmony of the universe. Besides music, electromagnetic waves such as light and electric signals also are presented as harmonic resonances. Despite the seemingly universal theme of harmonic resonance in various disciplines, it was not until recently that the same harmonic resonance was discovered also to exist in biological systems. Contrary to traditional belief that a biological system is either at stead-state or cycles with a single frequency, it is now appreciated that most biological systems have no homeostatic "set point," but rather oscillate as composite rhythms consisting of superimposed oscillations. These oscillations often cycle at different harmonics of the circadian rhythm, and among these, the ~12-hour oscillation is most prevalent. In this review, we focus on these 12-hour oscillations, with special attention to their evolutionary origin, regulation, and functions in mammals, as well as their relationship to the circadian rhythm. We further discuss the potential roles of the 12-hour clock in regulating hepatic steatosis, aging, and the possibility of 12-hour clock-based chronotherapy. Finally, we posit that biological rhythms are also musica universalis: whereas the circadian rhythm is synchronized to the 24-hour light/dark cycle coinciding with the Earth's rotation, the mammalian 12-hour clock may have evolved from the circatidal clock, which is entrained by the 12-hour tidal cues orchestrated by the moon.

Supplementation with resveratrol as Polygonum cuspidatum Sieb. et Zucc. extract induces changes in the excretion of urinary markers associated to aging in rats

An UPLC-HR-MS metabolomics approach was used to study the effects of a 49-days oral supplementation with Polygonum cuspidatum extract in healthy rats. Multivariate analysis allowed to observe significant differences in the excretion of several markers between treated animals and control group. Among the others, the amounts of N-methyl-2-pyridone-5-carboxamide (2PY) and phenylacetylglycine (PAG) were reduced in the treated group compared to control. These compounds have been previously considered as markers of aging. Furthermore, the excretion of 3-hydroxysebacic acid and 4,6-dihydroxyquinoline was also changed following supplementation, although not significantly. Despite the relatively short time of treatment (7 weeks), the significant changes in the urinary levels of aging markers observed at day 49 suggests a potential role of this type of studies as a new approach in the evaluation of the anti-aging effects of plant extracts.

An NAD+-Dependent Sirtuin Depropionylase and Deacetylase (Sir2La) from the Probiotic Bacterium Lactobacillus acidophilus NCFM

Sirtuins, a group of NAD⁺-dependent deacylases, have emerged as the key connection between NAD⁺ metabolism and aging. This class of enzymes hydrolyzes a range of ε- N-acyllysine PTMs, and determining the repertoire of catalyzed deacylation reactions is of high importance to fully elucidate the roles of a given sirtuin. Here we have identified and produced two potential sirtuins from the probiotic bacterium Lactobacillus acidophilus NCFM. Screening more than 80 different substrates, covering 26 acyl groups on five peptide scaffolds, demonstrated that one of the investigated proteins, Sir2La, is a bona fide NAD⁺-dependent sirtuin, catalyzing hydrolysis of acetyl-, propionyl-, and butyryllysine. Further substantiating the identity of Sir2La as a sirtuin, known sirtuin inhibitors, nicotinamide and suramin, as well as a thioacetyllysine compound inhibit the deacylase activity in a concentration-dependent manner. On the basis of steady-state kinetics, Sir2La showed a slight preference for propionyllysine (Kpro) over acetyllysine (Kac). For nonfluorogenic peptide substrates, the preference is driven by a remarkably low K_M (280 nM vs 700 nM, for Kpro and Kac, respectively), whereas k_cat was similar (21 × 10^-3 s^-1). Moreover, while NAD⁺ is a prerequisite for Sir2La-mediated deacylation, Sir2La has a very high K_M for NAD⁺ compared to the expected levels of the dinucleotide in L. acidophilus. Sir2La is the first sirtuin from Lactobacillales and of the Gram-positive bacterial subclass of sirtuins to be functionally characterized. The ability to hydrolyze propionyl- and butyryllysine emphasizes the relevance of further exploring the role of other short-chain acyl moieties as PTMs.

Increased podocyte Sirtuin-1 function attenuates diabetic kidney injury

Podocyte injury and loss contribute to the progression of glomerular diseases, including diabetic kidney disease. We previously found that the glomerular expression of Sirtuin-1 (SIRT1) is reduced in human diabetic glomeruli and that the podocyte-specific loss of SIRT1 aggravated albuminuria and worsened kidney disease progression in diabetic mice. SIRT1 encodes an NAD-dependent deacetylase that modifies the activity of key transcriptional regulators affected in diabetic kidneys, including NF-κB, STAT3, p53, FOXO4, and PGC1-α. However, whether the increased glomerular SIRT1 activity is sufficient to ameliorate the pathogenesis of diabetic kidney disease has not been explored. We addressed this by inducible podocyte-specific SIRT1 overexpression in diabetic OVE26 mice. The induction of SIRT1 overexpression in podocytes for six weeks in OVE26 mice with established albuminuria attenuated the progression of diabetic glomerulopathy. To further validate the therapeutic potential of increased SIRT1 activity against diabetic kidney disease, we developed a new, potent and selective SIRT1 agonist, BF175. In cultured podocytes BF175 increased SIRT1-mediated activation of PGC1-α and protected against high glucose-mediated mitochondrial injury. In vivo, administration of BF175 for six weeks in OVE26 mice resulted in a marked reduction in albuminuria and in glomerular injury in a manner similar to podocyte-specific SIRT1 overexpression. Both podocyte-specific SIRT1 overexpression and BT175 treatment attenuated diabetes-induced podocyte loss and reduced oxidative stress in glomeruli of OVE26 mice. Thus, increased SIRT1 activity protects against diabetes-induced podocyte injury and effectively mitigates the progression of diabetic kidney disease.

SIRT1, miR-132 and miR-212 link human longevity to Alzheimer's Disease

Alzheimer's Disease (AD) is the most common cause of dementia in the elderly. Centenarians - reaching the age of >100 years while maintaining good cognitive skills - seemingly have unique biological features allowing healthy aging and protection from dementia. Here, we studied the expression of SIRT1 along with miR-132 and miR-212, two microRNAs known to regulate SIRT1, in lymphoblastoid cell lines (LCLs) from 45 healthy donors aged 21 to 105 years and 24 AD patients, and in postmortem olfactory bulb and hippocampus tissues from 14 AD patients and 20 age-matched non-demented individuals. We observed 4.0-fold (P = 0.001) lower expression of SIRT1, and correspondingly higher expression of miR-132 (1.7-fold; P = 0.014) and miR-212 (2.1-fold; P = 0.036), in LCLs from AD patients compared with age-matched healthy controls. Additionally, SIRT1 expression was 2.2-fold (P = 0.001) higher in centenarian LCLs compared with LCLs from individuals aged 56-82 years; while centenarian LCLs miR-132 and miR-212 indicated 7.6-fold and 4.1-fold lower expression, respectively. Correlations of SIRT1, miR-132 and miR-212 expression with cognitive scores were observed for AD patient-derived LCLs and postmortem AD olfactory bulb and hippocampus tissues, suggesting that higher SIRT1 expression, possibly mediated by lower miR-132 and miR-212, may protect aged individuals from dementia and is reflected in their peripheral tissues.

NADPH Oxidases and Mitochondria in Vascular Senescence

Aging is the major risk factor in the development of cardiovascular diseases (CVDs), including hypertension, atherosclerosis, and myocardial infarction. Oxidative stress caused by overproduction of reactive oxygen species (ROS) and/or by reduced expression of antioxidant enzymes is a major contributor to the progression of vascular senescence, pathologic remodeling of the vascular wall, and disease. Both oxidative stress and inflammation promote the development of senescence, a process by which cells stop proliferating and become dysfunctional. This review focuses on the role of the mitochondria and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases Nox1 and Nox4 in vascular senescence, and their contribution to the development of atherosclerosis. Recent findings are reviewed, supporting a critical role of the mitochondrial regulator peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1α (PGC-1α), the inflammatory gene nuclear factor κB (NF-κB), zinc, the zinc transporters (ZnTs) ZnT3 and ZnT10, and angiotensin II (Ang II) in mitochondrial function, and their role in telomere stability, which provides new mechanistic insights into a previously proposed unified theory of aging.

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

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

Genomic Instabilities, Cellular Senescence, and Aging: In Vitro, In Vivo and Aging-Like Human Syndromes

As average life span and elderly people prevalence in the western world population is gradually increasing, the incidence of age-related diseases such as cancer, heart diseases, diabetes, and dementia is increasing, bearing social and economic consequences worldwide. Understanding the molecular basis of aging-related processes can help extend the organism’s health span, i.e., the life period in which the organism is free of chronic diseases or decrease in basic body functions. During the last few decades, immense progress was made in the understanding of major components of aging and healthy aging biology, including genomic instability, telomere attrition, epigenetic changes, proteostasis, nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and intracellular communications. This progress has been made by three spear-headed strategies: in vitro (cell and tissue culture from various sources), in vivo (includes diverse model and non-model organisms), both can be manipulated and translated to human biology, and the study of aging-like human syndromes and human populations. Herein, we will focus on current repository of genomic “senescence” stage of aging, which includes health decline, structural changes of the genome, faulty DNA damage response and DNA damage, telomere shortening, and epigenetic alterations. Although aging is a complex process, many of the “hallmarks” of aging are directly related to DNA structure and function. This review will illustrate the variety of these studies, done in in vitro, in vivo and human levels, and highlight the unique potential and contribution of each research level and eventually the link between them.

Sirtuin activators and inhibitors: Promises, achievements, and challenges

The NAD⁺-dependent protein lysine deacylases of the Sirtuin family regulate various physiological functions, from energy metabolism to stress responses. The human Sirtuin isoforms, SIRT1-7, are considered attractive therapeutic targets for aging-related diseases, such as type 2 diabetes, inflammatory diseases and neurodegenerative disorders. We review the status of Sirtuin-targeted drug discovery and development. Potent and selective pharmacological Sirt1 activators and inhibitors are available, and initial clinical trials have been carried out. Several promising inhibitors and activators have also been described for other isoforms. Progress in understanding the mechanisms of Sirtuin modulation by such compounds provides a rational basis for further drug development.

Development of Activity-Based Chemical Probes for Human Sirtuins

Sirtuins consume stoichiometric amounts of nicotinamide adenine dinucleotide (NAD⁺) to remove an acetyl group from lysine residues. These enzymes have been implicated in regulating various cellular events and have also been suggested to mediate the beneficial effects of calorie restriction (CR). However, controversies on sirtuin biology also peaked during the past few years because of conflicting results from different research groups. This is partly because these enzymes have been discovered recently and the intricate interaction loops between sirtuins and other proteins make the characterization of them extremely difficult. Current molecular biology and proteomics techniques report protein abundance rather than active sirtuin content. Innovative chemical tools that can directly probe the functional state of sirtuins are desperately needed. We have obtained a set of powerful activity-based chemical probes that are capable of assessing the active content of sirtuins in model systems. These probes consist of a chemical "warhead" that binds to the active site of active enzyme and a handle that can be used for the visualization of these enzymes by fluorescence. In complex native proteome, the probes can selectively "highlight" the active sirtuin components. Furthermore, these probes were also able to probe the dynamic change of sirtuin activity in response to cellular stimuli. These chemical probes and the labeling strategies will provide transformative technology to allow the direct linking of sirtuin activity to distinct physiological processes. They will create new opportunities to investigate how sirtuins provide health benefits in adapting cells to environmental cues and provide critical information to dissect sirtuin regulatory networks.

Longevity promoting efficacies of different plant extracts in lower model organisms

Past investigations have shown that various plant extracts are capable of promoting longevity in lower model organisms like Caenorhabditis elegans, Drosophila melanogaster, Saccharomyces cerevisiae, Bombyx mori etc. Longevity studies on such organisms provide a foundation to explore anti-aging efficacies of such plant extracts in higher organisms. Plant extracts of acai palm, apple, asparagus, blueberry, cinnamon, cocoa, Damnacanthus, maize, milk thistle, mistletoe, peach, pomegranate, Rhodiola, rose, Sasa, turmeric, and Withania have extended lifespan in lower model organisms via diverse mechanisms like insulin like growth factor (IGF) signaling pathway, and antioxidant defense mechanisms. Knowledge of pathways altered by the extracts can be investigated as potential drug-targets for natural anti-aging interventions. Thus, the aim of the review is to scrutinize longevity promoting efficacies of various plant extracts in lower model organisms.

Prediction and characterization of human ageing-related proteins by using machine learning

Ageing has a huge impact on human health and economy, but its molecular basis - regulation and mechanism - is still poorly understood. By today, more than three hundred genes (almost all of them function as protein-coding genes) have been related to human ageing. Although individual ageing-related genes or some small subsets of these genes have been intensively studied, their analysis as a whole has been highly limited. To fill this gap, for each human protein we extracted 21000 protein features from various databases, and using these data as an input to state-of-the-art machine learning methods, we classified human proteins as ageing-related or non-ageing-related. We found a simple classification model based on only 36 protein features, such as the "number of ageing-related interaction partners", "response to oxidative stress", "damaged DNA binding", "rhythmic process" and "extracellular region". Predicted values of the model quantify the relevance of a given protein in the regulation or mechanisms of the human ageing process. Furthermore, we identified new candidate proteins having strong computational evidence of their important role in ageing. Some of them, like Cytochrome b-245 light chain (CY24A) and Endoribonuclease ZC3H12A (ZC12A) have no previous ageing-associated annotations.

ER stress and cancer: The FOXO forkhead transcription factor link

The endoplasmic reticulum (ER) is a cellular organelle with central roles in maintaining proteostasis due to its involvement in protein synthesis, folding, quality control, distribution and degradation. The accumulation of misfolded proteins in the ER lumen causes 'ER stress' and threatens overall cellular proteostasis. To restore ER homeostasis, cells evoke an evolutionarily conserved adaptive signalling and gene expression network collectively called the 'unfolded protein response (UPR)', a complex biological process which aims to restore proteostasis. When ER stress is overwhelming and beyond rectification, the normally pro-survival UPR can shift to induce cell termination. Emerging evidence from mammalian, fly and nematode worm systems reveals that the FOXO Forkhead proteins integrate upstream ER stress and UPR signals with the transcriptional machinery to decrease translation, promote cell survival/termination and increase the levels of ER-resident chaperones and of ER-associated degradation (ERAD) components to restore ER homeostasis. The high rates of protein synthesis/translation associated with cancer cell proliferation and metabolism, as well as mutations resulting in aberrant proteins, also induce ER stress and the UPR. While the pro-survival side of the UPR underlies its ability to sustain and promote cancers, its apoptotic functions can be exploited for cancer therapies by offering the chance to 'flick the proteostatic switch'. To this end, further studies are required to fully reevaluate the roles and regulation of these UPR signalling molecules, including FOXO proteins and their targets, in cancer initiation and progression as well as the effects on inhibiting their functions in cancer cells. This information will help to establish these UPR signalling molecules as possible therapeutic targets and putative biomarkers in cancers.

Mitochondrial sirtuins in the heart

Sirtuins (SIRTs) are NAD(+)-dependent enzymes that catalyze deacylation of protein lysine residues. In mammals, seven sirtuins have been identified, SIRT1-7. SIRT3-5 are mainly or exclusively localized within mitochondria and mainly participate in the regulation of energy metabolic pathways. Since mitochondrial ATP regeneration is inevitably linked to the maintenance of cardiac pump function, it is not surprising that recent studies revealed a role for mitochondrial sirtuins in the regulation of myocardial energetics and function. In addition, mitochondrial sirtuins modulate the extent of myocardial ischemia reperfusion injury and the development of cardiac hypertrophy and failure. Thus, targeting mitochondrial sirtuins has been proposed as a novel approach to improve myocardial mitochondrial energetics, which is frequently impaired in cardiac disease and considered an important underlying cause contributing to several cardiac pathologies, including myocardial ischemia reperfusion injury and heart failure. In the current review, we present and discuss the available literature on mitochondrial sirtuins and their potential roles in cardiac physiology and disease.