The sirtuin SIRT6 regulates lifespan in male mice

SIRT6 in Regulation of Mitochondrial Damage and Associated Cardiac Dysfunctions: A Possible Therapeutic Target for CVDs

Cardiovascular diseases (CVDs) can be described as a global health emergency imploring possible prevention strategies. Although the pathogenesis of CVDs has been extensively studied, the role of mitochondrial dysfunction in CVD development has yet to be investigated. Diabetic cardiomyopathy, ischemic-reperfusion injury, and heart failure are some of the CVDs resulting from mitochondrial dysfunction Recent evidence from the research states that any dysfunction of mitochondria has an impact on metabolic alteration, eventually causes the death of a healthy cell and therefore, progressively directing to the predisposition of disease. Cardiovascular research investigating the targets that both protect and treat mitochondrial damage will help reduce the risk and increase the quality of life of patients suffering from various CVDs. One such target, i.e., nuclear sirtuin SIRT6 is strongly associated with cardiac function. However, the link between mitochondrial dysfunction and SIRT6 concerning cardiovascular pathologies remains poorly understood. Although the Role of SIRT6 in skeletal muscles and cardiomyocytes through mitochondrial regulation has been well understood, its specific role in mitochondrial maintenance in cardiomyocytes is poorly determined. The review aims to explore the domain-specific function of SIRT6 in cardiomyocytes and is an effort to know how SIRT6, mitochondria, and CVDs are related.

The age-related decline of helicase function-how G-quadruplex structures promote genome instability

The intricate mechanisms underlying transcription-dependent genome instability involve G-quadruplexes (G4) and R-loops. This perspective elucidates the potential link between these structures and genome instability in aging. The co-occurrence of G4 DNA and RNA-DNA hybrid structures (G-loop) underscores a complex interplay in genome regulation and instability. Here, we hypothesize that the age-related decline of sirtuin function leads to an increase in acetylated helicases that bind to G4 DNA and RNA-DNA hybrid structures, but are less efficient in resolving them. We propose that acetylated, less active, helicases induce persistent G-loop structures, promoting transcription-dependent genome instability in aging.

SIRT1, resveratrol and aging

Aging is linked to a time-associated decline in both cellular function and repair capacity leading to malfunction on an organismal level, increased frailty, higher incidence of diseases, and death. As the population grows older, there is a need to reveal mechanisms associated with aging that could spearhead treatments to postpone the onset of age-associated decline, extend both healthspan and lifespan. One possibility is targeting the sirtuin SIRT1, the founding member of the sirtuin family, a highly conserved family of histone deacetylases that have been linked to metabolism, stress response, protein synthesis, genomic instability, neurodegeneration, DNA damage repair, and inflammation. Importantly, sirtuins have also been implicated to promote health and lifespan extension, while their dysregulation has been linked to cancer, neurological processes, and heart disorders. SIRT1 is one of seven members of sirtuin family; each requiring nicotinamide adenine dinucleotide (NAD+) as co-substrate for their catalytic activity. Overexpression of yeast, worm, fly, and mice SIRT1 homologs extend lifespan in each animal, respectively. Moreover, lifespan extension due to calorie restriction are associated with increased sirtuin activity. These findings led to the search for a calorie restriction mimetic, which revealed the compound resveratrol; (3, 5, 4'-trihydroxy-trans-stilbene) belonging to the stilbenoids group of polyphenols. Following this finding, resveratrol and other sirtuin-activating compounds have been extensively studied for their ability to affect health and lifespan in a variety of species, including humans via clinical studies.

Sirtuins in kidney health and disease

Sirtuins (SIRTs) are putative regulators of lifespan in model organisms. Since the initial discovery that SIRTs could promote longevity in nematodes and flies, the identification of additional properties of these proteins has led to understanding of their roles as exquisite sensors that link metabolic activity to oxidative states. SIRTs have major roles in biological processes that are important in kidney development and physiological functions, including mitochondrial metabolism, oxidative stress, autophagy, DNA repair and inflammation. Furthermore, altered SIRT activity has been implicated in the pathophysiology and progression of acute and chronic kidney diseases, including acute kidney injury, diabetic kidney disease, chronic kidney disease, polycystic kidney disease, autoimmune diseases and renal ageing. The renoprotective roles of SIRTs in these diseases make them attractive therapeutic targets. A number of SIRT-activating compounds have shown beneficial effects in kidney disease models; however, further research is needed to identify novel SIRT-targeting strategies with the potential to treat and/or prevent the progression of kidney diseases and increase the average human healthspan.

Hepatic Sirt6 activation abrogates acute liver failure

Acute liver failure (ALF) is a deadly illness due to insufficient detoxification in liver induced by drugs, toxins, and other etiologies, and the effective treatment for ALF is very limited. Among the drug-induced ALF, acetaminophen (APAP) overdose is the most common cause. However, the molecular mechanisms underlying APAP hepatoxicity remain incompletely understood. Sirtuin 6 (Sirt6) is a stress responsive protein deacetylase and plays an important role in regulation of DNA repair, genomic stability, oxidative stress, and inflammation. Here, we report that genetic and pharmacological activation of Sirt6 protects against ALF in mice. We first observed that Sirt6 expression was significantly reduced in the liver tissues of human patients with ALF and mice treated with an overdose of APAP. Then we developed an inducible Sirt6 transgenic mice for Cre-mediated overexpression of the human Sirt6 gene in systemic (Sirt6-Tg) and hepatic-specific (Sirt6-HepTg) manners. Both Sirt6-Tg mice and Sirt6-HepTg mice exhibited the significant protection against APAP hepatoxicity. In contrast, hepatic-specific Sirt6 knockout mice exaggerated APAP-induced liver damages. Mechanistically, Sirt6 attenuated APAP-induced hepatocyte necrosis and apoptosis through downregulation of oxidative stress, inflammation, the stress-activated kinase JNK activation, and apoptotic caspase activation. Moreover, Sirt6 negatively modulated the level and activity of poly (ADP-ribose) polymerase 1 (PARP1) in APAP-treated mouse liver tissues. Importantly, the specific Sirt6 activator MDL-800 exhibited better therapeutic potential for APAP hepatoxicity than the current drug acetylcysteine. Furthermore, in the model of bile duct ligation induced ALF, hepatic Sirt6-KO exacerbated, but Sirt6-HepTg mitigated liver damage. Collectively, our results demonstrate that Sirt6 protects against ALF and suggest that targeting Sirt6 activation could be a new therapeutic strategy to alleviate ALF.

Caloric restriction, Sirtuins, and cardiovascular diseases

ABSTRACT

Caloric restriction (CR) is a well-established dietary intervention known to extend healthy lifespan and exert positive effects on aging-related diseases, including cardiovascular conditions. Sirtuins, a family of nicotinamide adenine dinucleotide (NAD + )-dependent histone deacetylases, have emerged as key regulators of cellular metabolism, stress responses, and the aging process, serving as energy status sensors in response to CR. However, the mechanism through which CR regulates Sirtuin function to ameliorate cardiovascular disease remains unclear. This review not only provided an overview of recent research investigating the interplay between Sirtuins and CR, specifically focusing on their potential implications for cardiovascular health, but also provided a comprehensive summary of the benefits of CR for the cardiovascular system mediated directly via Sirtuins. CR has also been shown to have considerable impact on specific metabolic organs, leading to the production of small molecules that enter systemic circulation and subsequently regulate Sirtuin activity within the cardiovascular system. The direct and indirect effects of CR offer a potential mechanism for Sirtuin modulation and subsequent cardiovascular protection. Understanding the interplay between CR and Sirtuins will provide new insights for the development of interventions to prevent and treat cardiovascular diseases.

Aging and the emerging role of cellular senescence in osteoarthritis

OBJECTIVE

The correlation between age and incidence of osteoarthritis (OA) is well known but the causal mechanisms involved are not completely understood. This narrative review summarizes selected key findings from the past 30 years that have elucidated key aspects of the relationship between aging and OA.

METHODS

The peer-reviewed English language literature was searched on PubMed using keywords including senescence, aging, cartilage, and osteoarthritis, for original studies and reviews published from 1993 to 2023 with a major focus on more recent studies. Manuscripts most relevant to aging and OA that examined one or more of the hallmarks of aging were selected for further review.

RESULTS

All proposed hallmarks of aging have been observed in articular cartilage and some have also been described in other joint tissues. Hallmarks include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, disabled macroautophagy, chronic inflammation, and dysbiosis. There is evidence that these age-related changes contribute to the development of OA in part by promoting cellular senescence. Senescence may therefore serve as a downstream mediator that connects numerous aging hallmarks to OA, likely through the senescence-associated secretory phenotype that is characterized by increased production of proinflammatory cytokines and matrix metalloproteinases.

CONCLUSIONS

Progress over the past 30 years has provided the foundation for emerging therapies, such as senolytics and senomorphics, that hold promise for OA disease modification. Mechanistic studies utilizing physiologically-aged animals and cadaveric human joint tissues will be important for continued progress.

SIRT6 activates PPARα to improve doxorubicin-induced myocardial cell aging and damage

The Sirtuins family, formally known as the Silent Information Regulator Factors, constitutes a highly conserved group of histone deacetylases. Recent studies have illuminated SIRT6's role in doxorubicin (DOX)-induced oxidative stress and apoptosis within myocardial cells. Nevertheless, the extent of SIRT6's impact on DOX-triggered myocardial cell aging and damage remains uncertain, with the associated mechanisms yet to be fully understood. In our research, we examined the influence of SIRT6 on DOX-induced cardiomyocyte senescence using β-galactosidase and γ-H2AX staining. Additionally, we gauged the mRNA expression of senescence-associated genes, namely p16, p21, and p53, through Real-time PCR. Employing ELISA assay kits, MDA, and total SOD activity assay kits, we measured inflammatory factors TNF-α, IL-6, and IL-1β, alongside oxidative stress-related indicators. The results unequivocally indicated that SIRT6 overexpression robustly inhibited DOX-induced cardiomyocyte senescence. Furthermore, we established that SIRT6 overexpression suppressed the inflammatory response and oxidative stress induced by DOX in cardiomyocytes. Conversely, silencing SIRT6 exacerbated DOX-induced cardiomyocyte injury. Our investigations further unveiled that SIRT6 upregulated the expression of genes CD36, CPT1, LCAD, MCAD associated with fatty acid oxidation through its interaction with PPARα, thereby exerting anti-aging effects. In vivo, the overexpression of SIRT6 was observed to restore DOX-induced declines in EF and FS to normal levels in mice. Echocardiography and HE staining revealed the restoration of cardiomyocyte alignment, affording protection against DOX-induced myocardial senescence and injury. The findings from this study suggest that SIRT6 holds significant promise as a therapeutic target for mitigating DOX-induced cardiomyopathy.

Unveiling the interplay of AMPK/SIRT1/PGC-1α axis in brain health: Promising targets against aging and NDDs

The escalating prevalence of neurodegenerative diseases (NDDs) within an aging global population presents a pressing challenge. The multifaceted pathophysiological mechanisms underlying these disorders, including oxidative stress, mitochondrial dysfunction, and neuroinflammation, remain complex and elusive. Among these, the AMPK/SIRT1/PGC-1α pathway emerges as a pivotal network implicated in neuroprotection against these destructive processes. This review sheds light on the potential therapeutic implications of targeting this axis, specifically emphasizing the promising role of flavonoids in mitigating NDD-related complications. Expanding beyond conventional pharmacological approaches, the exploration of non-pharmacological interventions such as exercise and calorie restriction (CR), coupled with the investigation of natural compounds, offers a beacon of hope. By strategically elucidating the intricate connections within these pathways, this review aims to pave the ways for novel multi-target agents and interventions, fostering a renewed optimism in the quest to combat and manage the debilitating impacts of NDDs on global health and well-being.

Decoding the secrets of longevity: unraveling nutraceutical and miRNA-Mediated aging pathways and therapeutic strategies

MicroRNAs (miRNAs) are short RNA molecules that are not involved in coding for proteins. They have a significant function in regulating gene expression after the process of transcription. Their participation in several biological processes has rendered them appealing subjects for investigating age-related disorders. Increasing data indicates that miRNAs can be influenced by dietary variables, such as macronutrients, micronutrients, trace minerals, and nutraceuticals. This review examines the influence of dietary factors and nutraceuticals on the regulation of miRNA in relation to the process of aging. We examine the present comprehension of miRNA disruption in age-related illnesses and emphasize the possibility of dietary manipulation as a means of prevention or treatment. Consolidating animal and human research is essential to validate the significance of dietary miRNA control in living organisms, despite the abundance of information already provided by several studies. This review elucidates the complex interaction among miRNAs, nutrition, and aging, offering valuable insights into promising areas for further research and potential therapies for age-related disorders.

Ergothioneine promotes longevity and healthy aging in male mice

Healthy aging has emerged as a crucial issue with the increase in the geriatric population worldwide. Food-derived sulfur-containing amino acid ergothioneine (ERGO) is a potential dietary supplement, which exhibits various beneficial effects in experimental animals although the preventive effects of ERGO on aging and/or age-related impairments such as frailty and cognitive impairment are unclear. We investigated the effects of daily oral supplementation of ERGO dissolved in drinking water on lifespan, frailty, and cognitive impairment in male mice from 7 weeks of age to the end of their lives. Ingestion of 4 ~ 5 mg/kg/day of ERGO remarkably extended the lifespan of male mice. The longevity effect of ERGO was further supported by increase in life and non-frailty spans of Caenorhabditis elegans in the presence of ERGO. Compared with the control group, the ERGO group showed significantly lower age-related declines in weight, fat mass, and average and maximum movement velocities at 88 weeks of age. This was compatible with dramatical suppression by ERGO of the age-related increments in plasma biomarkers (BMs) such as the chemokine ligand 9, creatinine, symmetric dimethylarginine, urea, asymmetric dimethylarginine, quinolinic acid, and kynurenine. The oral intake of ERGO also rescued age-related impairments in learning and memory ability, which might be associated with suppression of the age-related decline in hippocampal neurogenesis and TDP43 protein aggregation and promotion of microglial shift to the M2 phenotype by ERGO ingestion. Ingestion of ERGO may promote longevity and healthy aging in male mice, possibly through multiple biological mechanisms.

Current Trends in Sirtuin Activator and Inhibitor Development

Sirtuins are NAD+-dependent protein deacylases and key metabolic regulators, coupling the cellular energy state with selective lysine deacylation to regulate many downstream cellular processes. Humans encode seven sirtuin isoforms (Sirt1-7) with diverse subcellular localization and deacylase targets. Sirtuins are considered protective anti-aging proteins since increased sirtuin activity is canonically associated with lifespan extension and decreased activity with developing aging-related diseases. However, sirtuins can also assume detrimental cellular roles where increased activity contributes to pathophysiology. Modulation of sirtuin activity by activators and inhibitors thus holds substantial potential for defining the cellular roles of sirtuins in health and disease and developing therapeutics. Instead of being comprehensive, this review discusses the well-characterized sirtuin activators and inhibitors available to date, particularly those with demonstrated selectivity, potency, and cellular activity. This review also provides recommendations regarding the best-in-class sirtuin activators and inhibitors for practical research as sirtuin modulator discovery and refinement evolve.

Ergothioneine and its congeners: anti-ageing mechanisms and pharmacophore biosynthesis

Ergothioneine, Ovothiol, and Selenoneine are sulfur/selenium-containing histidine-derived natural products widely distributed across different organisms. They exhibit significant antioxidant properties, making them as potential lead compounds for promoting health. Increasing evidence suggests that Ergothioneine is positively correlated with healthy ageing and longevity. The mechanisms underlying Ergothioneine's regulation of the ageing process at cellular and molecular levels are beginning to be understood. In this review, we provide an in-depth and extensive coverage of the anti-ageing studies on Ergothioneine and discuss its possible intracellular targeting pathways. In addition, we highlight the recent efforts in elucidating the biosynthetic details for Ergothioneine, Ovothiol, and Selenoneine, with a particular focus on the study of their pharmacophore-forming enzymology.

Binding to nucleosome poises human SIRT6 for histone H3 deacetylation

Sirtuin 6 (SIRT6) is an NAD+-dependent histone H3 deacetylase that is prominently found associated with chromatin, attenuates transcriptionally active promoters and regulates DNA repair, metabolic homeostasis and lifespan. Unlike other sirtuins, it has low affinity to free histone tails but demonstrates strong binding to nucleosomes. It is poorly understood how SIRT6 docking on nucleosomes stimulates its histone deacetylation activity. Here, we present the structure of human SIRT6 bound to a nucleosome determined by cryogenic electron microscopy. The zinc finger domain of SIRT6 associates tightly with the acidic patch of the nucleosome through multiple arginine anchors. The Rossmann fold domain binds to the terminus of the looser DNA half of the nucleosome, detaching two turns of the DNA from the histone octamer and placing the NAD+ binding pocket close to the DNA exit site. This domain shows flexibility with respect to the fixed zinc finger and moves with, but also relative to, the unwrapped DNA terminus. We apply molecular dynamics simulations of the histone tails in the nucleosome to show that in this mode of interaction, the active site of SIRT6 is perfectly poised to catalyze deacetylation of the H3 histone tail and that the partial unwrapping of the DNA allows even lysines close to the H3 core to reach the enzyme.

Fisetin suppresses chondrocyte senescence and attenuates osteoarthritis progression by targeting sirtuin 6

Osteoarthritis (OA) is the most common type of arthritis and is an age-related joint disease that is particularly prevalent in subjects over 65 years old. The chronic rise of senescent cells has a close correlation with age-related diseases such as OA, and the senescence-associated secretory phenotype (SASP) is implicated in OA cartilage degeneration pathogenesis. Sirtuin 6 (SIRT6) is likely to be a key senescence-related regulator. Fisetin (FST) is a natural flavonol of the flavonoid family that is recommended as a senolytic drug to extend health and lifespan. However, the potential chondroprotective effects of FST on OA rats are largely unclarified. The aim of this study is to investigate the ameliorative effects of FST on OA joint cartilage and the relationship with SIRT6 and the detailed mechanisms from anti-inflammatory and anti-senescent perspectives. Rats were subjected to destabilization of the medial meniscus (DMM) surgery as a means of inducing the experimental OA model in vivo. Chondrocytes treated with IL-1β were utilized for mimicking the OA cell model in vitro. Intra-articular injection of FST, OSS_128,167 (OSS, SIRT6 inhibitor), and MDL800 (MDL, SIRT6 agonist) in vivo or administering them in IL-1β-induced rat chondrocytes in vitro were performed in order to determine the effects FST has on OA and the link with SIRT6. This study found SIRT6 level to be negatively correlated with OA severity. SIRT6 downregulation was validated in the joint cartilages of DMM rats and IL-1β-treated chondrocytes. It was also notably demonstrated that FST can activate SIRT6. Both the administration of FST and activation of SIRT6 using MDL were found to rescue cartilage erosion, decrease extracellular matrix (ECM) degradation, prevent cartilage from apoptosis, and improve detrimental senescence-related phenotype. The alleviative effects of FST against inflammation, ECM degradation, apoptosis, and senescence in IL-1β-stimulated chondrocytes were also confirmed. SIRT6 loss occurs in articular cartilage in OA pathogenesis, which is linked to aging. FST attenuates injury-induced aging-related phenotype changes in chondrocytes through the targeting of SIRT6.

Sirt6 regulates the proliferation of neural precursor cells and cortical neurogenesis in mice

Sirt6, a member of the class III histone deacetylases (HDACs), functions in the regulation of genomic stability, DNA repair, cancer, metabolism and aging. Sirt6 deficiency is lethal, and newborn SIRT6-null cynomolgus monkeys show unfinished brain development. After the generation of a cortex-specific Sirt6 conditional knockout mouse model, we investigated the specific deletion of Sirt6 in NPCs at E10.5. This study found that Sirt6 deficiency causes excessive proliferation of neural precursor cells (NPCs) and retards differentiation. The results suggest that endogenous Sirt6 in NPCs regulates histone acetylation and limits stemness-related genes, including Notch1, in order to participate in NPC fate determination. These findings help elucidate Sirt6's role in brain development and in NPC fate determination while providing data on species generality and differentiation.

PKCδ Regulates Chromatin Remodeling and DNA Repair through SIRT6

Irradiation (IR) is a highly effective cancer therapy; however, IR damage to tumor-adjacent healthy tissues can result in significant comorbidities and potentially limit the course of therapy. We have previously shown that protein kinase C delta (PKCδ) is required for IR-induced apoptosis and that inhibition of PKCδ activity provides radioprotection in vivo. Here we show that PKCδ regulates histone modification, chromatin accessibility, and double-stranded break (DSB) repair through a mechanism that requires Sirtuin 6 (SIRT6). Overexpression of PKCδ promotes genomic instability and increases DNA damage and apoptosis. Conversely, depletion of PKCδ increases DNA repair via nonhomologous end joining (NHEJ) and homologous recombination (HR) as evidenced by increased formation of DNA damage foci, increased expression of DNA repair proteins, and increased repair of NHEJ and HR fluorescent reporter constructs. Nuclease sensitivity indicates that PKCδ depletion is associated with more open chromatin, while overexpression of PKCδ reduces chromatin accessibility. Epiproteome analysis reveals increased chromatin associated H3K36me2 in PKCδ-depleted cells which is accompanied by chromatin disassociation of KDM2A. We identify SIRT6 as a downstream mediator of PKCδ. PKCδ-depleted cells have increased SIRT6 expression, and depletion of SIRT6 reverses changes in chromatin accessibility, histone modification and DSB repair in PKCδ-depleted cells. Furthermore, depletion of SIRT6 reverses radioprotection in PKCδ-depleted cells. Our studies describe a novel pathway whereby PKCδ orchestrates SIRT6-dependent changes in chromatin accessibility to regulate DNA repair, and define a mechanism for regulation of radiation-induced apoptosis by PKCδ.

IMPLICATIONS

PKCδ controls sensitivity to irradiation by regulating DNA repair.

SIRT6 Protects Against Lipopolysaccharide-Induced Inflammation in Human Pulmonary Lung Microvascular Endothelial Cells

Inflammatory response in the pulmonary endothelium drives the pathogenesis of acute lung injury and sepsis. Sirtuin 6 (SIRT6), a member of class III NAD+-dependent deacetylases belonging to the sirtuin family, regulates senescence, metabolism, and inflammation and extends lifespan in mice and model organisms. However, the role of SIRT6 in pulmonary endothelial inflammation is unknown. Thus, we hypothesized that SIRT6 suppresses inflammatory response in human lung microvascular cells (HLMEC) and ensues monocyte adhesion to endothelial cells. Primary HLMECs were treated with control or SIRT6 adenovirus or SIRT6 agonist, with or without lipopolysaccharide (LPS) treatment. We observed that treatment with LPS did not affect the protein expression of SIRT6 in HLMECs. However, adenovirus-mediated SIRT6 overexpression attenuated LPS-induced VCAM1 gene and protein expression, followed by decreased monocyte adhesion to endothelial cells. Similarly, activation of SIRT6 by a recently reported SIRT6 activator UBCS039, but not the regioisomer negative control compound UBCS060, ameliorated LPS-induced VCAM1 mRNA and protein expression as well as monocyte adhesion. Moreover, luciferase assay revealed that SIRT6 adenovirus decreased the activity of NF-κB, the master regulator of vascular inflammation. Taken together, these results indicate that molecular and pharmacological activation of SIRT6 protects against lung microvascular inflammation via suppressing NF-κB activation, implicating the therapeutic potential of the SIRT6 activators for lung disorders associated with microvascular inflammation.

SIRT6 Improves Hippocampal Neurogenesis Following Prolonged Sleep Deprivation Through Modulating Energy Metabolism in Developing rats

OBJECTIVE

Prolonged sleep deprivation is known to have detrimental effects on the hippocampus during development or in adulthood. Furthermore, it is well-established that sleep deprivation disrupts energy metabolism broadly. SIRT6 is a critical regulator of energy metabolism in both central and peripheral tissues. This study aims to investigate the role of SIRT6 in modulating hippocampal neurogenesis following sleep deprivation during development, and elucidate the underlying mechanism.

METHODS

Male Sprague-Dawley rats, aged three weeks, were subjected to 2 weeks of sleep deprivation using the modified multiple platform method. Metabolomic profiling was carried out using the liquid chromatography-electrospray ionization-tandem mass spectrometry (LC‒ESI‒MS/MS). To investigate the role of SIRT6 in energy metabolism, the rats were administered with either the SIRT6-specific inhibitor, OSS128167, or SIRT6-overexpressing adeno-associated virus (AAV). Hippocampal neurogenesis was assessed by immunostaining with markers for neural stem cells (SOX2), immature neurons [doublecortin (DCX)] and newborn cells (BrdU). Sparse labeling of adult neurons was used to determine the density of dendritic spines in the dentate gyrus (DG). The Y-maze and novel object recognition (NOR) tests were performed to evaluate the spatial and recognition memory. SIRT6 expression was examined using immunofluorescence and western blotting (WB). The inhibition of SIRT6 was confirmed by assessing the acetylation of histone 3 lysine 9 (aceH3K9), a well-known substrate of SIRT6, through WB.

RESULTS

Sleep deprivation for a period of two weeks leads to inhibited hippocampal neurogenesis, reduced density of dendritic spines in the DG, and impaired memory, accompanied by decreased SIRT6 expression and disrupted energy metabolism. Similar to sleep deprivation, administration of OSS128167 significantly decreased energy metabolism, leading to reduced neurogenesis and memory dysfunction. Notably, the abnormal hippocampal energy metabolism, neurogenetic pathological changes and memory dysfunction caused by sleep deprivation were alleviated by SIRT6 overexpression in the DG.

CONCLUSION

Our results suggest that SIRT6 plays a critical role in maintaining energy metabolism homeostasis in the hippocampus after sleep deprivation, promoting hippocampal neurogenesis and enhancing memory during development.

Treatment with Cerebrolysin Prolongs Lifespan in a Mouse Model of Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare familial neurological disorder caused by mutations in the NOTCH3 gene and characterized by migraine attacks, depressive episodes, lacunar strokes, dementia, and premature death. Since there is no therapy for CADASIL the authors investigate whether the multi-modal neuropeptide drug Cerebrolysin may improve outcome in a murine CADASIL model. Twelve-month-old NOTCH3R169C mutant mice (n=176) are treated for nine weeks with Cerebrolysin or Vehicle and histopathological and functional outcomes are evaluated within the subsequent ten months. Cerebrolysin treatment improves spatial memory and overall health, reduces epigenetic aging, and prolongs lifespan, however, CADASIL-specific white matter vacuolization is not affected. On the molecular level Cerebrolysin treatment increases expression of Calcitonin Gene-Related Peptide (CGRP) and Silent Information Regulator Two (Sir2)-like protein 6 (SIRT6), decreases expression of Insulin-like Growth Factor 1 (IGF-1), and normalizes the expression of neurovascular laminin. In summary, Cerebrolysin fosters longevity and healthy aging without specifically affecting CADASIL pathology. Hence, Cerebrolysin may serve a therapeutic option for CADASIL and other disorders characterized by accelerated aging.

SIRT3/6: an amazing challenge and opportunity in the fight against fibrosis and aging

Fibrosis is a typical aging-related pathological process involving almost all organs, including the heart, kidney, liver, lung, and skin. Fibrogenesis is a highly orchestrated process defined by sequences of cellular response and molecular signals mechanisms underlying the disease. In pathophysiologic conditions associated with organ fibrosis, a variety of injurious stimuli such as metabolic disorders, epigenetic changes, and aging may induce the progression of fibrosis. Sirtuins protein is a kind of deacetylase which can regulate cell metabolism and participate in a variety of cell physiological functions. In this review, we outline our current understanding of common principles of fibrogenic mechanisms and the functional role of SIRT3/6 in aging-related fibrosis. In addition, sequences of novel protective strategies have been identified directly or indirectly according to these mechanisms. Here, we highlight the role and biological function of SIRT3/6 focus on aging fibrosis, as well as their inhibitors and activators as novel preventative or therapeutic interventions for aging-related tissue fibrosis.

Transposable Elements: Emerging Therapeutic Targets in Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), are characterized by the progressive loss of neuronal function and structure. While several genetic and environmental factors have been implicated in the pathogenesis of these disorders, emerging evidence suggests that transposable elements (TEs), once considered "junk DNA," play a significant role in their development and progression. TEs are mobile genetic elements capable of moving within the genome, and their dysregulation has been associated with genomic instability, altered gene expression, and neuroinflammation. This review provides an overview of TEs, including long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), and endogenous retroviruses (ERVs), mechanisms of repression and derepression, and their potential impact on neurodegeneration. The evidence linking TEs to AD, PD, and ALS by shedding light on the complex interactions between TEs and neurodegeneration has been discussed. Furthermore, the therapeutic potential of targeting TEs in neurodegenerative diseases has been explored. Understanding the role of TEs in neurodegeneration holds promise for developing novel therapeutic strategies aimed at mitigating disease progression and preserving neuronal health.

HDAC1/2 inhibitor therapy improves multiple organ systems in aged mice

Aging increases the risk of age-related diseases, imposing substantial healthcare and personal costs. Targeting fundamental aging mechanisms pharmacologically can promote healthy aging and reduce this disease susceptibility. In this work, we employed transcriptome-based drug screening to identify compounds emulating transcriptional signatures of long-lived genetic interventions. We discovered compound 60 (Cmpd60), a selective histone deacetylase 1 and 2 (HDAC1/2) inhibitor, mimicking diverse longevity interventions. In extensive molecular, phenotypic, and bioinformatic assessments using various cell and aged mouse models, we found Cmpd60 treatment to improve age-related phenotypes in multiple organs. Cmpd60 reduces renal epithelial-mesenchymal transition and fibrosis in kidney, diminishes dementia-related gene expression in brain, and enhances cardiac contractility and relaxation for the heart. In sum, our two-week HDAC1/2 inhibitor treatment in aged mice establishes a multi-tissue, healthy aging intervention in mammals, holding promise for therapeutic translation to promote healthy aging in humans.

Spatial omics: An innovative frontier in aging research

Disentangling the impact of aging on health and disease has become critical as population aging progresses rapidly. Studying aging at the molecular level is complicated by the diverse aging profiles and dynamics. However, the examination of cellular states within aging tissues in situ is hampered by the lack of high-resolution spatial data. Emerging spatial omics technologies facilitate molecular and spatial analysis of tissues, providing direct access to precise information on various functional regions and serving as a favorable tool for unraveling the heterogeneity of aging. In this review, we summarize the recent advances in spatial omics application in multi-organ aging research, which has enhanced the understanding of aging mechanisms from multiple standpoints. We also discuss the main challenges in spatial omics research to date, the opportunities for further developing the technology, and the potential applications of spatial omics in aging and aging-related diseases.

The transcription factor GATA6 accelerates vascular smooth muscle cell senescence-related arterial calcification by counteracting the role of anti-aging factor SIRT6 and impeding DNA damage repair

Arterial calcification is a hallmark of vascular pathology in the elderly and in individuals with chronic kidney disease (CKD). Vascular smooth muscle cells (VSMCs), after attaining a senescent phenotype, are implicated in the calcifying process. However, the underlying mechanism remains to be elucidated. Here, we reveal an aberrant upregulation of transcriptional factor GATA6 in the calcified aortas of humans, mice with CKD and mice subjected to vitamin D3 injection. Knockdown of GATA6, via recombinant adeno-associated virus carrying GATA6 shRNA, inhibited the development of arterial calcification in mice with CKD. Further gain- and loss-of function experiments in vitro verified the contribution of GATA6 in osteogenic differentiation of VSMCs. Samples of human aorta exhibited a positive relationship between age and GATA6 expression and GATA6 was also elevated in the aortas of old as compared to young mice. Calcified aortas displayed senescent features with VSMCs undergoing premature senescence, blunted by GATA6 downregulation. Notably, abnormal induction of GATA6 in senescent and calcified aortas was rescued in Sirtuin 6 (SIRT6)-transgenic mice, a well-established longevity mouse model. Suppression of GATA6 accounted for the favorable effect of SIRT6 on VSMCs senescence prevention. Mechanistically, SIRT6 inhibited the transcription of GATA6 by deacetylation and increased degradation of transcription factor Nkx2.5. Moreover, GATA6 was induced by DNA damage stress during arterial calcification and subsequently impeded the Ataxia-telangiectasia mutated (ATM)-mediated DNA damage repair process, leading to accelerated VSMCs senescence and osteogenic differentiation. Thus, GATA6 is a novel regulator in VSMCs senescence. Our findings provide novel insight in arterial calcification and a potential new target for intervention.

Responses to Many Anti-Aging Interventions Are Sexually Dimorphic

There is increasing appreciation that sex differences are not limited to reproductive organs or traits related to reproduction and that sex is an important biological variable in most characteristics of a living organism. The biological process of aging and aging-related traits are no exception and exhibit numerous, often major, sex differences. This article explores one aspect of these differences, namely sex differences in the responses to anti-aging interventions. Aging can be slowed down and/or postponed by a variety of environmental ("lifestyle"), genetic or pharmacological interventions. Although many, particularly older studies utilized only one sex of experimental animals, there is considerable evidence that responses to these interventions can be very different in females and males. Calorie restriction (CR), that is reducing food intake without malnutrition can extend longevity in both sexes, but specific metabolic alterations and health benefits induced by CR are not the same in women and men. In laboratory mice, several of the genetic alterations that reduce insulin-like growth factor I (IGF-1) signaling extend longevity more effectively in females or in females only. Beneficial effects of rapamycin, an inhibitor of mTOR signaling, on mouse longevity are greater in females. In contrast, several anti-aging compounds, including a weak estrogen, 17 alpha estradiol, extend longevity of male, but not female, mice. Apparently, fundamental mechanisms of aging are not identical in females and males and it is essential to use both sexes in studies aimed at identifying novel anti-aging interventions. Recommendations for lifestyle modifications, drugs, and dietary supplements to maintain good health and functionality into advanced age and to live longer will likely need to be tailored to the sex of the user.

The Emerging Role of SIRT7 in Glucose and Lipid Metabolism

Sirtuins (SIRT1-7 in mammals) are a family of NAD+-dependent lysine deacetylases and deacylases that regulate diverse biological processes, including metabolism, stress responses, and aging. SIRT7 is the least well-studied member of the sirtuins, but accumulating evidence has shown that SIRT7 plays critical roles in the regulation of glucose and lipid metabolism by modulating many target proteins in white adipose tissue, brown adipose tissue, and liver tissue. This review focuses on the emerging roles of SIRT7 in glucose and lipid metabolism in comparison with SIRT1 and SIRT6. We also discuss the possible implications of SIRT7 inhibition in the treatment of metabolic diseases such as type 2 diabetes and obesity.

SIRT6 promotes metastasis and relapse in HER2-positive breast cancer

The histone deacetylase sirtuin 6 (SIRT6) has been endowed with anti-cancer capabilities in many tumor types. Here, we investigate the impact of SIRT6-overexpression (SIRT6-OE) in Delta16HER2 mice, which are a bona fide model of HER2-positive breast cancer. After an initial delay in the tumor onset, SIRT6-OE induces a more aggressive phenotype of Delta16HER2 tumors promoting the formation of higher number of tumor foci and metastases than controls. This phenotype of SIRT6-OE tumors is associated with cancer stem cell (CSC)-like features and tumor dormancy, and low senescence and oxidative DNA damage. Accordingly, a sub-set of HER2-positive breast cancer patients with concurrent SIRT6-OE has a significant poorer relapse-free survival (RFS) probability than patients with low expression of SIRT6. ChIP-seq, RNA-seq and RT-PCR experiments indicate that SIRT6-OE represses the expression of the T-box transcription factor 3 (Tbx3) by deacetylation of H3K9ac. Accordingly, loss-of-function mutations of TBX3 or low TBX3 expression levels are predictive of poor prognosis in HER2-positive breast cancer patients. Our work indicates that high levels of SIRT6 are indicative of poor prognosis and high risk of metastasis in HER2-positive breast cancer and suggests further investigation of TBX3 as a downstream target of SIRT6 and co-marker of poor-prognosis. Our results point to a breast cancer subtype-specific effect of SIRT6 and warrant future studies dissecting the mechanisms of SIRT6 regulation in different breast cancer subtypes.

Impact of NAD+ metabolism on ovarian aging

Nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme in cellular redox reactions, is closely associated with age-related functional degeneration and metabolic diseases. NAD exerts direct and indirect influences on many crucial cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cellular senescence, and immune cell functionality. These cellular processes and functions are essential for maintaining tissue and metabolic homeostasis, as well as healthy aging. Causality has been elucidated between a decline in NAD levels and multiple age-related diseases, which has been confirmed by various strategies aimed at increasing NAD levels in the preclinical setting. Ovarian aging is recognized as a natural process characterized by a decline in follicle number and function, resulting in decreased estrogen production and menopause. In this regard, it is necessary to address the many factors involved in this complicated procedure, which could improve fertility in women of advanced maternal age. Concerning the decrease in NAD+ levels as ovarian aging progresses, promising and exciting results are presented for strategies using NAD+ precursors to promote NAD+ biosynthesis, which could substantially improve oocyte quality and alleviate ovarian aging. Hence, to acquire further insights into NAD+ metabolism and biology, this review aims to probe the factors affecting ovarian aging, the characteristics of NAD+ precursors, and the current research status of NAD+ supplementation in ovarian aging. Specifically, by gaining a comprehensive understanding of these aspects, we are optimistic about the prominent progress that will be made in both research and therapy related to ovarian aging.

SIRT2 transgenic over-expression does not impact lifespan in mice

The NAD+ -dependent deacylase family of sirtuin enzymes have been implicated in biological ageing, late-life health and overall lifespan, though of these members, a role for sirtuin-2 (SIRT2) is less clear. Transgenic overexpression of SIRT2 in the BubR1 hypomorph model of progeria can rescue many aspects of health and increase overall lifespan, due to a specific interaction between SIRT2 and BubR1 that improves the stability of this protein. It is less clear whether SIRT2 is relevant to biological ageing outside of a model where BubR1 is under-expressed. Here, we sought to test whether SIRT2 over-expression would impact the overall health and lifespan of mice on a nonprogeroid, wild-type background. While we previously found that SIRT2 transgenic overexpression prolonged female fertility, here, we did not observe any additional impact on health or lifespan, which was measured in both male and female mice on standard chow diets, and in males challenged with a high-fat diet. At the biochemical level, NMR studies revealed an increase in total levels of a number of metabolites in the brain of SIRT2-Tg animals, pointing to a potential impact in cell composition; however, this did not translate into functional differences. Overall, we conclude that strategies to enhance SIRT2 protein levels may not lead to increased longevity.

Epigenetic aging of mammalian gametes

The process of aging refers to physiological changes that occur to an organism as time progresses and involves changes to DNA, proteins, metabolism, cells, and organs. Like the rest of the cells in the body, gametes age, and it is well established that there is a decline in reproductive capabilities in females and males with aging. One of the major pathways known to be involved in aging is epigenetic changes. The epigenome is the multitude of chemical modifications performed on DNA and chromatin that affect the ability of chromatin to be transcribed. In this review, we explore the effects of aging on female and male gametes with a focus on the epigenetic changes that occur in gametes throughout aging. Quality decline in oocytes occurs at a relatively early age. Epigenetic changes constitute an important part of oocyte aging. DNA methylation is reduced with age, along with reduced expression of DNA methyltransferases (DNMTs). Histone deacetylases (HDAC) expression is also reduced, and a loss of heterochromatin marks occurs with age. As a consequence of heterochromatin loss, retrotransposon expression is elevated, and aged oocytes suffer from DNA damage. In sperm, aging affects sperm number, motility and fecundity, and epigenetic changes may constitute a part of this process. 5 methyl-cytosine (5mC) methylation is elevated in sperm from aged men, but methylation on Long interspersed nuclear elements (LINE) elements is reduced. Di and trimethylation of histone 3 lysine 9 (H3K9me2/3) is reduced in sperm from aged men and trimethylation of histone 3 lysine 27 (H3K27me3) is elevated. The protamine makeup of sperm from aged men is also changed, with reduced protamine expression and a misbalanced ratio between protamine proteins protamine P1 and protamine P2. The study of epigenetic reproductive aging is recently gaining interest. The current status of the field suggests that many aspects of gamete epigenetic aging are still open for investigation. The clinical applications of these investigations have far-reaching consequences for fertility and sociological human behavior.

The Information Theory of Aging

Information storage and retrieval is essential for all life. In biology, information is primarily stored in two distinct ways: the genome, comprising nucleic acids, acts as a foundational blueprint and the epigenome, consisting of chemical modifications to DNA and histone proteins, regulates gene expression patterns and endows cells with specific identities and functions. Unlike the stable, digital nature of genetic information, epigenetic information is stored in a digital-analog format, susceptible to alterations induced by diverse environmental signals and cellular damage. The Information Theory of Aging (ITOA) states that the aging process is driven by the progressive loss of youthful epigenetic information, the retrieval of which via epigenetic reprogramming can improve the function of damaged and aged tissues by catalyzing age reversal.

The rosetta stone of successful ageing: does oral health have a role?

Ageing is an inevitable aspect of life and thus successful ageing is an important focus of recent scientific efforts. The biological process of ageing is mediated through the interaction of genes with environmental factors, increasing the body's susceptibility to insults. Elucidating this process will increase our ability to prevent and treat age-related disease and consequently extend life expectancy. Notably, centenarians offer a unique perspective on the phenomenon of ageing. Current research highlights several age-associated alterations on the genetic, epigenetic and proteomic level. Consequently, nutrient sensing and mitochondrial function are altered, resulting in inflammation and exhaustion of regenerative ability.Oral health, an important contributor to overall health, remains underexplored in the context of extreme longevity. Good masticatory function ensures sufficient nutrient uptake, reducing morbidity and mortality in old age. The relationship between periodontal disease and systemic inflammatory pathologies is well established. Diabetes, rheumatoid arthritis and cardiovascular disease are among the most significant disease burdens influenced by inflammatory oral health conditions. Evidence suggests that the interaction is bi-directional, impacting progression, severity and mortality. Current models of ageing and longevity neglect an important factor in overall health and well-being, a gap that this review intends to illustrate and inspire avenues for future research.

Activation of SIRT6 Deacetylation by DNA Strand Breaks

SIRT6 is an emerging regulator of longevity. Overexpression of SIRT6 extends the lifespan of mice. Conversely, SIRT6 knockout mice demonstrate severe metabolic defects and a shortened lifespan. The discrepancy between SIRT6's weak in vitro activity and robust in vivo activity has led to the hypothesis that this enzyme can be activated in response to DNA damage in cells. Here, we demonstrate that the deacetylase activity of SIRT6 can be stimulated by DNA strand breaks for synthetic peptide and histone substrates. The mechanism of activation is further explored by using an integrative chemical biology approach. SIRT6 can be preferentially activated by DNA lesions harboring a 5'-phosphate. The N- and C-termini of SIRT6 are strictly required for DNA break-induced activation. Additionally, the defatty-acylase activity of SIRT6 is also sensitive to DNA breaks, although the physiological significance needs further investigation. Collectively, our study sheds important light on the cellular regulation of diverse SIRT6 activities and suggests possible strategies for effective SIRT6 activation.

The CRTC-1 transcriptional domain is required for COMPASS complex-mediated longevity in C. elegans

Loss of function during aging is accompanied by transcriptional drift, altering gene expression and contributing to a variety of age-related diseases. CREB-regulated transcriptional coactivators (CRTCs) have emerged as key regulators of gene expression that might be targeted to promote longevity. Here we define the role of the Caenorhabditis elegans CRTC-1 in the epigenetic regulation of longevity. Endogenous CRTC-1 binds chromatin factors, including components of the COMPASS complex, which trimethylates lysine 4 on histone H3 (H3K4me3). CRISPR editing of endogenous CRTC-1 reveals that the CREB-binding domain in neurons is specifically required for H3K4me3-dependent longevity. However, this effect is independent of CREB but instead acts via the transcription factor AP-1. Strikingly, CRTC-1 also mediates global histone acetylation levels, and this acetylation is essential for H3K4me3-dependent longevity. Indeed, overexpression of an acetyltransferase enzyme is sufficient to promote longevity in wild-type worms. CRTCs, therefore, link energetics to longevity by critically fine-tuning histone acetylation and methylation to promote healthy aging.

The many faces of SIRT6 in the retina and retinal pigment epithelium

Sirtuin 6 (SIRT6) is a member of the mammalian sirtuin family of NAD+-dependent protein deacylases, homologues of the yeast silent information regulator 2 (Sir2). SIRT6 has remarkably diverse functions and plays a key role in a variety of biological processes for maintaining cellular and organismal homeostasis. In this review, our primary aim is to summarize recent progress in understanding SIRT6's functions in the retina and retinal pigment epithelium (RPE), with the hope of further drawing interests in SIRT6 to increase efforts in exploring the therapeutic potential of this unique protein in the vision field. Before describing SIRT6's role in the eye, we first discuss SIRT6's general functions in a wide range of biological contexts. SIRT6 plays an important role in gene silencing, metabolism, DNA repair, antioxidant defense, inflammation, aging and longevity, early development, and stress response. In addition, recent studies have revealed SIRT6's role in macrophage polarization and mitochondrial homeostasis. Despite being initially understudied in the context of the eye, recent efforts have begun to elucidate the critical functions of SIRT6 in the retina and RPE. In the retina, SIRT6 is essential for adult retinal function, regulates energy metabolism by suppressing glycolysis that affects photoreceptor cell survival, protects retinal ganglion cells from oxidative stress, and plays a role in Müller cells during early neurodegenerative events in diabetic retinopathy. In the RPE, SIRT6 activates autophagy in culture and protects against oxidative stress in mice. Taken together, this review demonstrates that better understanding of SIRT6's functions and their mechanisms, both in and out of the context of the eye, holds great promise for the development of SIRT6-targeted strategies for prevention and treatment of blinding eye diseases.

Cartilage-specific Sirt6 deficiency represses IGF-1 and enhances osteoarthritis severity in mice

OBJECTIVES

Prior studies noted that chondrocyte SIRT6 activity is repressed in older chondrocytes rendering cells susceptible to catabolic signalling events implicated in osteoarthritis (OA). This study aimed to define the effect of Sirt6 deficiency on the development of post-traumatic and age-associated OA in mice.

METHODS

Male cartilage-specific Sirt6-deficient mice and Sirt6 intact controls underwent destabilisation of the medial meniscus (DMM) or sham surgery at 16 weeks of age and OA severity was analysed at 6 and 10 weeks postsurgery. Age-associated OA was assessed in mice aged 12 and 18 months of age. OA severity was analysed by micro-CT, histomorphometry and scoring of articular cartilage structure, toluidine blue staining and osteophyte formation. SIRT6-regulated pathways were analysed in human chondrocytes by RNA-sequencing, qRT-PCR and immunoblotting.

RESULTS

Sirt6-deficient mice displayed enhanced DMM-induced OA severity and accelerated age-associated OA when compared with controls, characterised by increased cartilage damage, osteophyte formation and subchondral bone sclerosis. In chondrocytes, RNA-sequencing revealed that SIRT6 depletion significantly repressed cartilage extracellular matrix (eg, COL2A1) and anabolic growth factor (eg, insulin-like growth factor-1 (IGF-1)) gene expression. Gain-of-function and loss-of-function studies in chondrocytes demonstrated that SIRT6 depletion attenuated, whereas adenoviral overexpression or MDL-800-induced SIRT6 activation promoted IGF-1 signalling by increasing Aktser473 phosphorylation.

CONCLUSIONS

SIRT6 deficiency increases post-traumatic and age-associated OA severity in vivo. SIRT6 profoundly regulated the pro-anabolic and pro-survival IGF-1/Akt signalling pathway and suggests that preserving the SIRT6/IGF-1/Akt axis may be necessary to protect cartilage from injury-associated or age-associated OA. Targeted therapies aimed at increasing SIRT6 function could represent a novel strategy to slow or stop OA.

Effect of mitochondrial quantity and quality controls in white adipose tissue on healthy lifespan: Essential roles of GH/IGF-1-independent pathways in caloric restriction-mediated metabolic remodeling

Long-term caloric restriction is a conventional and reproducible dietary intervention to improve whole body metabolism, suppress age-related pathophysiology, and extend lifespan. The beneficial actions of caloric restriction are widely accepted to be regulated in both growth hormone/insulin-like growth factor 1-dependent and -independent manners. Although growth hormone/insulin-like growth factor 1-dependent regulatory mechanisms are well described, those occurring independent of growth hormone/insulin-like growth factor 1 are poorly understood. In this review, we focus on molecular mechanisms of caloric restriction regulated in a growth hormone/insulin-like growth factor 1-independent manner. Caloric restriction increases mitochondrial quantity and improves mitochondrial quality by activating an axis involving sterol regulatory element binding protein-c/peroxisome proliferator-activated receptor γ coactivator-1α/mitochondrial intermediate peptidase in a growth hormone/insulin-like growth factor 1-independent manner, particularly in white adipose tissue. Fibroblast growth factor 21 is also involved in this axis. Moreover, the axis may be regulated by lower leptin signaling. Thus, caloric restriction appears to induce beneficial actions partially by regulating mitochondrial quantity and quality in white adipose tissue in a growth hormone/insulin-like growth factor 1-independent manner.

G9a and Sirtuin6 epigenetically modulate host cholesterol accumulation to facilitate mycobacterial survival

Cholesterol derived from the host milieu forms a critical factor for mycobacterial pathogenesis. However, the molecular circuitry co-opted by Mycobacterium tuberculosis (Mtb) to accumulate cholesterol in host cells remains obscure. Here, we report that the coordinated action of WNT-responsive histone modifiers G9a (H3K9 methyltransferase) and SIRT6 (H3K9 deacetylase) orchestrate cholesterol build-up in in vitro and in vivo mouse models of Mtb infection. Mechanistically, G9a, along with SREBP2, drives the expression of cholesterol biosynthesis and uptake genes; while SIRT6 along with G9a represses the genes involved in cholesterol efflux. The accumulated cholesterol in Mtb infected macrophages promotes the expression of antioxidant genes leading to reduced oxidative stress, thereby supporting Mtb survival. In corroboration, loss-of-function of G9a in vitro and pharmacological inhibition in vivo; or utilization of BMDMs derived from Sirt6-/- mice or in vivo infection in haplo-insufficient Sirt6-/+ mice; hampered host cholesterol accumulation and restricted Mtb burden. These findings shed light on the novel roles of G9a and SIRT6 during Mtb infection and highlight the previously unknown contribution of host cholesterol in potentiating anti-oxidative responses for aiding Mtb survival.

Cardiac Aging Is Promoted by Pseudohypoxia Increasing p300-Induced Glycolysis

BACKGROUND

Heart failure is typical in the elderly. Metabolic remodeling of cardiomyocytes underlies inexorable deterioration of cardiac function with aging: glycolysis increases at the expense of oxidative phosphorylation, causing an energy deficit contributing to impaired contractility. Better understanding of the mechanisms of this metabolic switching could be critical for reversing the condition.

METHODS

To investigate the role of 3 histone modifications (H3K27ac, H3K27me3, and H3K4me1) in the metabolic remodeling occurring in the aging heart, we cross-compared epigenomic, transcriptomic, and metabolomic data from mice of different ages. In addition, the role of the transcriptional coactivator p300 (E1A-associated binding protein p300)/CBP (CREB binding protein) in cardiac aging was investigated using a specific inhibitor of this histone acetyltransferase enzyme.

RESULTS

We report a set of species-conserved enhancers associated with transcriptional changes underlying age-related metabolic remodeling in cardiomyocytes. Activation of the enhancer region of Hk2-a key glycolysis pathway gene-was fostered in old age-onset mouse heart by pseudohypoxia, wherein hypoxia-related genes are expressed under normal O2 levels, via increased activity of P300/CBP. Pharmacological inhibition of this transcriptional coactivator before the onset of cardiac aging led to a more aerobic, less glycolytic, metabolic state, improved heart contractility, and overall blunting of cardiac decline.

CONCLUSIONS

Taken together, our results suggest how epigenetic dysregulation of glycolysis pathway enhancers could potentially be targeted to treat heart failure in the elderly.

Genomic Instability and Epigenetic Changes during Aging

Aging is considered the deterioration of physiological functions along with an increased mortality rate. This scientific review focuses on the central importance of genomic instability during the aging process, encompassing a range of cellular and molecular changes that occur with advancing age. In particular, this revision addresses the genetic and epigenetic alterations that contribute to genomic instability, such as telomere shortening, DNA damage accumulation, and decreased DNA repair capacity. Furthermore, the review explores the epigenetic changes that occur with aging, including modifications to histones, DNA methylation patterns, and the role of non-coding RNAs. Finally, the review discusses the organization of chromatin and its contribution to genomic instability, including heterochromatin loss, chromatin remodeling, and changes in nucleosome and histone abundance. In conclusion, this review highlights the fundamental role that genomic instability plays in the aging process and underscores the need for continued research into these complex biological mechanisms.

Large-scale across species transcriptomic analysis identifies genetic selection signatures associated with longevity in mammals

Lifespan varies significantly among mammals, with more than 100-fold difference between the shortest and longest living species. This natural difference may uncover the evolutionary forces and molecular features that define longevity. To understand the relationship between gene expression variation and longevity, we conducted a comparative transcriptomics analysis of liver, kidney, and brain tissues of 103 mammalian species. We found that few genes exhibit common expression patterns with longevity in the three organs analyzed. However, pathways related to translation fidelity, such as nonsense-mediated decay and eukaryotic translation elongation, correlated with longevity across mammals. Analyses of selection pressure found that selection intensity related to the direction of longevity-correlated genes is inconsistent across organs. Furthermore, expression of methionine restriction-related genes correlated with longevity and was under strong selection in long-lived mammals, suggesting that a common strategy is utilized by natural selection and artificial intervention to control lifespan. Our results indicate that lifespan regulation via gene expression is driven through polygenic and indirect natural selection.

Genetic perturbation of AMP biosynthesis extends lifespan and restores metabolic health in a naturally short-lived vertebrate

During aging, the loss of metabolic homeostasis drives a myriad of pathologies. A central regulator of cellular energy, the AMP-activated protein kinase (AMPK), orchestrates organismal metabolism. However, direct genetic manipulations of the AMPK complex in mice have, so far, produced detrimental phenotypes. Here, as an alternative approach, we alter energy homeostasis by manipulating the upstream nucleotide pool. Using the turquoise killifish, we mutate APRT, a key enzyme in AMP biosynthesis, and extend the lifespan of heterozygous males. Next, we apply an integrated omics approach to show that metabolic functions are rejuvenated in old mutants, which also display a fasting-like metabolic profile and resistance to high-fat diet. At the cellular level, heterozygous cells exhibit enhanced nutrient sensitivity, reduced ATP levels, and AMPK activation. Finally, lifelong intermittent fasting abolishes the longevity benefits. Our findings suggest that perturbing AMP biosynthesis may modulate vertebrate lifespan and propose APRT as a promising target for promoting metabolic health.

Genomic Instability Evolutionary Footprints on Human Health: Driving Forces or Side Effects?

In this work, we propose a comprehensive perspective on genomic instability comprising not only the accumulation of mutations but also telomeric shortening, epigenetic alterations and other mechanisms that could contribute to genomic information conservation or corruption. First, we present mechanisms playing a role in genomic instability across the kingdoms of life. Then, we explore the impact of genomic instability on the human being across its evolutionary history and on present-day human health, with a particular focus on aging and complex disorders. Finally, we discuss the role of non-coding RNAs, highlighting future approaches for a better living and an expanded healthy lifespan.

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

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

Elevation of Arginase-II in Podocytes Contributes to Age-Associated Albuminuria in Male Mice

One of the manifestations of renal aging is podocyte dysfunction and loss, which are associated with proteinuria and glomerulosclerosis. Studies show a male bias in glomerular dysfunction and chronic kidney diseases, and the underlying mechanisms remain obscure. Recent studies demonstrate the role of an age-associated increase in arginase-II (Arg-II) in proximal tubules of both male and female mice. However, it is unclear whether Arg-II is also involved in aging glomeruli. The current study investigates the role of the sex-specific elevation of Arg-II in podocytes in age-associated increased albuminuria. Young (3-4 months) and old (20-22 months) male and female mice of wt and arginase-II knockout (arg-ii-/-) were used. Albuminuria was employed as a readout of glomerular function. Cellular localization and expression of Arg-II in glomeruli were analyzed using an immunofluorescence confocal microscope. A more pronounced age-associated increase in albuminuria was found in male than in female mice. An age-associated induction of Arg-II in glomeruli and podocytes (as demonstrated by co-localization of Arg-II with the podocyte marker synaptopodin) was also observed in males but not in females. Ablation of the arg-ii gene in mice significantly reduces age-associated albuminuria in males. Also, age-associated decreases in podocyte density and glomerulus hypertrophy are significantly prevented in male arg-ii-/- but not in female mice. However, age-associated glomerulosclerosis is not affected by arg-ii ablation in both sexes. These results demonstrate a role of Arg-II in sex-specific podocyte injury in aging. They may explain the sex-specific differences in the development of renal disease in humans during aging.

SIRT6 overexpression in the nucleus protects mouse retinal pigment epithelium from oxidative stress

Retinal pigment epithelium (RPE) is essential for the survival of retinal photoreceptors. To study retinal degeneration, sodium iodate (NaIO3) has been used to cause oxidative stress-induced RPE death followed by photoreceptor degeneration. However, analyses of RPE damage itself are still limited. Here, we characterized NaIO3-induced RPE damage, which was divided into three regions: periphery with normal-shaped RPE, transitional zone with elongated cells, and center with severely damaged or lost RPE. Elongated cells in the transitional zone exhibited molecular characteristics of epithelial-mesenchymal transition. Central RPE was more susceptible to stresses than peripheral RPE. Under stresses, SIRT6, an NAD+-dependent protein deacylase, rapidly translocated from the nucleus to the cytoplasm and colocalized with stress granule factor G3BP1, leading to nuclear SIRT6 depletion. To overcome this SIRT6 depletion, SIRT6 overexpression was induced in the nucleus in transgenic mice, which protected RPE from NaIO3 and partially preserved catalase expression. These results demonstrate topological differences of mouse RPE and warrant further exploring SIRT6 as a potential target for protecting RPE from oxidative stress-induced damage.

The Role of Increased Expression of Sirtuin 6 in the Prevention of Premature Aging Pathomechanisms

Sirtuins, in mammals, are a group of seven enzymes (SIRT1-SIRT7) involved in the post-translational modification of proteins-they are considered longevity proteins. SIRT6, classified as class IV, is located on the cell nucleus; however, its action is also connected with other regions, e.g., mitochondria and cytoplasm. It affects many molecular pathways involved in aging: telomere maintenance, DNA repair, inflammatory processes or glycolysis. A literature search for keywords or phrases was carried out in PubMed and further searches were carried out on the ClinicalTrials.gov website. The role of SIRT6 in both premature and chronological aging has been pointed out. SIRT6 is involved in the regulation of homeostasis-an increase in the protein's activity has been noted in calorie-restriction diets and with significant weight loss, among others. Expression of this protein is also elevated in people who regularly exercise. SIRT6 has been shown to have different effects on inflammation, depending on the cells involved. The protein is considered a factor in phenotypic attachment and the migratory responses of macrophages, thus accelerating the process of wound healing. Furthermore, exogenous substances will affect the expression level of SIRT6: resveratrol, sirtinol, flavonoids, cyanidin, quercetin and others. This study discusses the importance of the role of SIRT6 in aging, metabolic activity, inflammation, the wound healing process and physical activity.

Which Factors Influence Healthy Aging? A Lesson from the Longevity Village of Bama in China

A growing aging population is associated with increasing incidences of aging-related diseases and socioeconomic burdens. Hence, research into healthy longevity and aging is urgently needed. Longevity is an important phenomenon in healthy aging. The present review summarizes the characteristics of longevity in the elderly population in Bama, China, where the proportion of centenarians is 5.7-fold greater than the international standard. We examined the impact of genetic and environmental factors on longevity from multiple perspectives. We proposed that the phenomenon of longevity in this region is of high value for future investigations in healthy aging and aging-related disease and may provide guidance for fostering the establishment and maintenance of a healthy aging society.

PKCδ regulates chromatin remodeling and DNA repair through SIRT6

Protein kinase C delta (PKCδ) is a ubiquitous kinase whose function is defined in part by localization to specific cellular compartments. Nuclear PKCδ is both necessary and sufficient for IR-induced apoptosis, while inhibition of PKCδ activity provides radioprotection in vivo. How nuclear PKCδ regulates DNA-damage induced cell death is poorly understood. Here we show that PKCδ regulates histone modification, chromatin accessibility, and double stranded break (DSB) repair through a mechanism that requires SIRT6. Overexpression of PKCδ promotes genomic instability and increases DNA damage and apoptosis. Conversely, depletion of PKCδ increases DNA repair via non-homologous end joining (NHEJ) and homologous recombination (HR) as evidenced by more rapid formation of NHEJ (DNA-PK) and HR (Rad51) DNA damage foci, increased expression of repair proteins, and increased repair of NHEJ and HR fluorescent reporter constructs. Nuclease sensitivity indicates that PKCδ depletion is associated with more open chromatin, while overexpression of PKCδ reduces chromatin accessibility. Epiproteome analysis revealed that PKCδ depletion increases chromatin associated H3K36me2, and reduces ribosylation of KDM2A and chromatin bound KDM2A. We identify SIRT6 as a downstream mediator of PKCδ. PKCδ-depleted cells have increased expression of SIRT6, and depletion of SIRT6 reverses the changes in chromatin accessibility, histone modification and NHEJ and HR DNA repair seen with PKCδ-depletion. Furthermore, depletion of SIRT6 reverses radioprotection in PKCδ-depleted cells. Our studies describe a novel pathway whereby PKCδ orchestrates SIRT6-dependent changes in chromatin accessibility to increase DNA repair, and define a mechanism for regulation of radiation-induced apoptosis by PKCδ.