Variability of the SIRT3 gene, human silent information regulator Sir2 homologue, and survivorship in the elderly

Sirtuin Proteins and Memory: A Promising Target in Alzheimer's Disease Therapy?

Sirtuins (SIRTs), nicotine adenine dinucleotide (+)-dependent histone deacetylases, have emerged as critical regulators in many signalling pathways involved in a wide range of biological processes. Currently, seven mammalian SIRTs have been characterized and are found across a number of cellular compartments. There has been considerable interest in the role of SIRTs in the brain due to their role in a plethora of metabolic- and age-related diseases, including their involvement in learning and memory function in physiological and pathophysiological conditions. Although cognitive function declines over the course of healthy ageing, neurological disorders including Alzheimer's disease (AD) can be associated with progressive cognitive impairments. This review aimed to report and integrate recent advances in the understanding of the role of SIRTs in cognitive function and dysfunction in the context of AD. We have also reviewed the use of selective and/or natural SIRT activators as potential therapeutic agents and/or adjuvants for AD.

Interplay Between the Circadian Clock and Sirtuins

The circadian clock is an autonomous timekeeping system evolved by organisms to adapt to external changes, regulating a variety of important physiological and behavioral processes. Recent studies have shown that the sirtuin family of histone deacetylases is involved in regulating the expression of clock genes and plays an important role in maintaining the normal rhythm of clock gene expression and behavior. Moreover, sirtuins are regulated directly or indirectly by the circadian clock system. The mutual regulation between the circadian clock and sirtuins is likely involved in a variety of signal transduction and metabolism processes. In this review, we discuss the molecular mechanisms and research progress on the intertwined relationship between the circadian clock and sirtuins, mainly in mammals, highlighting sirtuins as molecular links between metabolic control and circadian rhythms and offering our perspectives on future developments in the field.

The role of SIRT3 in homeostasis and cellular health

Mitochondria are responsible for maintaining cellular energy levels, and play a major role in regulating homeostasis, which ensures physiological function from the molecular to whole animal. Sirtuin 3 (SIRT3) is the major protein deacetylase of mitochondria. SIRT3 serves as a nutrient sensor; under conditions of mild metabolic stress, SIRT3 activity is increased. Within the mitochondria, SIRT3 regulates every complex of the electron transport chain, the tricarboxylic acid (TCA) and urea cycles, as well as the mitochondria membrane potential, and other free radical scavengers. This article reviews the role of SIRT3 in regulating homeostasis, and thus physiological function. We discuss the role of SIRT3 in regulating reactive oxygen species (ROS), ATP, immunological function and mitochondria dynamics.

The Role of Mitochondrial Sirtuins (SIRT3, SIRT4 and SIRT5) in Renal Cell Metabolism: Implication for Kidney Diseases

Kidney diseases, including chronic kidney disease (CKD), diabetic nephropathy, and acute kidney injury (AKI), represent a significant global health burden. The kidneys are metabolically very active organs demanding a large amount of ATP. They are composed of highly specialized cell types in the glomerulus and subsequent tubular compartments which fine-tune metabolism to meet their numerous and diverse functions. Defective renal cell metabolism, including altered fatty acid oxidation or glycolysis, has been linked to both AKI and CKD. Mitochondria play a vital role in renal metabolism, and emerging research has identified mitochondrial sirtuins (SIRT3, SIRT4 and SIRT5) as key regulators of renal cell metabolic adaptation, especially SIRT3. Sirtuins belong to an evolutionarily conserved family of mainly NAD+-dependent deacetylases, deacylases, and ADP-ribosyl transferases. Their dependence on NAD+, used as a co-substrate, directly links their enzymatic activity to the metabolic status of the cell. In the kidney, SIRT3 has been described to play crucial roles in the regulation of mitochondrial function, and the antioxidative and antifibrotic response. SIRT3 has been found to be constantly downregulated in renal diseases. Genetic or pharmacologic upregulation of SIRT3 has also been associated with beneficial renal outcomes. Importantly, experimental pieces of evidence suggest that SIRT3 may act as an important energy sensor in renal cells by regulating the activity of key enzymes involved in metabolic adaptation. Activation of SIRT3 may thus represent an interesting strategy to ameliorate renal cell energetics. In this review, we discuss the roles of SIRT3 in lipid and glucose metabolism and in mediating a metabolic switch in a physiological and pathological context. Moreover, we highlight the emerging significance of other mitochondrial sirtuins, SIRT4 and SIRT5, in renal metabolism. Understanding the role of mitochondrial sirtuins in kidney diseases may also open new avenues for innovative and efficient therapeutic interventions and ultimately improve the management of renal injuries.

Sirtuins: exploring next-gen therapeutics in the pathogenesis osteoporosis and associated diseases

OBJECTIVE

Osteoporosis poses a substantial public health challenge due to an ageing population and the lack of adequate treatment options. The condition is marked by a reduction in bone mineral density, resulting in an elevated risk of fractures. The reduction in bone density and strength, as well as musculoskeletal issues that come with aging, present a significant challenge for individuals impacted by these conditions, as well as the healthcare system worldwide.

METHODS

Literature survey was conducted until May 2023 using databases such as Web of Science, PubMed, Scopus, and Google Scholar.

RESULT

Sirtuins 1-7 (SIRT1-SIRT7), which are a group of Nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, possess remarkable capabilities to increase lifespan and combat diseases related to aging. Research has demonstrated that these proteins play an important role in regular skeletal development and maintenance by directly impacting bone cells. Their dysfunction could be a factor in various bone conditions. Studies conducted on animals before clinical trials have shown that administering Sirtuins agonists to mice provides a safeguard against osteoporosis resulting from aging, menopause, and immobilization. These findings imply that Sirtuins may be a viable target for addressing the irregularity in bone remodeling and treating osteoporosis and other skeletal ailments.

CONCLUSION

The purpose of this review was to present a thorough and current evaluation of the existing knowledge on Sirtuins biology, with a particular emphasis on their involvement in maintaining bone homeostasis and contributing to osteoporosis. Additionally, the review examines potential pharmacological interventions targeting Sirtuins for the treatment of osteoporosis.

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.

Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality

Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.

Neuronal SIRT3 Deletion Predisposes to Female-Specific Alterations in Cellular Metabolism, Memory, and Network Excitability

Mitochondrial dysfunction is an early event in the pathogenesis of neurologic disorders and aging. Sirtuin 3 (SIRT3) regulates mitochondrial function in response to the cellular environment through the reversible deacetylation of proteins involved in metabolism and reactive oxygen species detoxification. As the primary mitochondrial deacetylase, germline, or peripheral tissue-specific deletion of SIRT3 produces mitochondrial hyperacetylation and the accelerated development of age-related diseases. Given the unique metabolic demands of neurons, the role of SIRT3 in the brain is only beginning to emerge. Using mass spectrometry-based acetylomics, high-resolution respirometry, video-EEG, and cognition testing, we report targeted deletion of SIRT3 from select neurons in the cortex and hippocampus produces altered neuronal excitability and metabolic dysfunction in female mice. Targeted deletion of SIRT3 from neuronal helix-loop-helix 1 (NEX)-expressing neurons resulted in mitochondrial hyperacetylation, female-specific superoxide dismutase-2 (SOD2) modification, increased steady-state superoxide levels, metabolic reprogramming, altered neuronal excitability, and working spatial memory deficits. Inducible neuronal deletion of SIRT3 likewise produced female-specific deficits in spatial working memory. Together, the data demonstrate that deletion of SIRT3 from forebrain neurons selectively predisposes female mice to deficits in mitochondrial and cognitive function.SIGNIFICANCE STATEMENT Mitochondrial SIRT3 is an enzyme shown to regulate energy metabolism and antioxidant function, by direct deacetylation of proteins. In this study, we show that neuronal SIRT3 deficiency renders female mice selectively vulnerable to impairment in redox and metabolic function, spatial memory, and neuronal excitability. The observed sex-specific effects on cognition and neuronal excitability in female SIRT3-deficient mice suggest that mitochondrial dysfunction may be one factor underlying comorbid neuronal diseases, such as Alzheimer's disease and epilepsy. Furthermore, the data suggest that SIRT3 dysfunction may predispose females to age-related metabolic and cognitive impairment.

A Promising Strategy to Treat Neurodegenerative Diseases by SIRT3 Activation

SIRT3, the primary mitochondrial deacetylase, regulates the functions of mitochondrial proteins including metabolic enzymes and respiratory chain components. Although SIRT3's functions in peripheral tissues are well established, the significance of its downregulation in neurodegenerative diseases is beginning to emerge. SIRT3 plays a key role in brain energy metabolism and provides substrate flexibility to neurons. It also facilitates metabolic coupling between fuel substrate-producing tissues and fuel-consuming tissues. SIRT3 mediates the health benefits of lifestyle-based modifications such as calorie restriction and exercise. SIRT3 deficiency is associated with metabolic syndrome (MetS), a precondition for diseases including obesity, diabetes, and cardiovascular disease. The pure form of Alzheimer's disease (AD) is rare, and it has been reported to coexist with these diseases in aging populations. SIRT3 downregulation leads to mitochondrial dysfunction, neuroinflammation, and inflammation, potentially triggering factors of AD pathogenesis. Recent studies have also suggested that SIRT3 may act through multiple pathways to reduce plaque formation in the AD brain. In this review, we give an overview of SIRT3's roles in brain physiology and pathology and discuss several activators of SIRT3 that can be considered potential therapeutic agents for the treatment of dementia.

Improving the effectiveness of anti-aging modalities by using the constrained disorder principle-based management algorithms

Aging is a complex biological process with multifactorial nature underlined by genetic, environmental, and social factors. In the present paper, we review several mechanisms of aging and the pre-clinically and clinically studied anti-aging therapies. Variability characterizes biological processes from the genome to cellular organelles, biochemical processes, and whole organs' function. Aging is associated with alterations in the degrees of variability and complexity of systems. The constrained disorder principle defines living organisms based on their inherent disorder within arbitrary boundaries and defines aging as having a lower variability or moving outside the boundaries of variability. We focus on associations between variability and hallmarks of aging and discuss the roles of disorder and variability of systems in the pathogenesis of aging. The paper presents the concept of implementing the constrained disease principle-based second-generation artificial intelligence systems for improving anti-aging modalities. The platform uses constrained noise to enhance systems' efficiency and slow the aging process. Described is the potential use of second-generation artificial intelligence systems in patients with chronic disease and its implications for the aged population.

Ginsenoside Rb1 improves intestinal aging via regulating the expression of sirtuins in the intestinal epithelium and modulating the gut microbiota of mice

Intestinal aging seriously affects the absorption of nutrients of the aged people. Ginsenoside Rb1 (GRb1) which has multiple functions on treating gastrointestinal disorders is one of the important ingredients from Ginseng, the famous herb in tradition Chinese medicine. However, it is still unclear if GRb1 could improve intestinal aging. To investigate the function and mechanism of GRb1 on improving intestinal aging, GRb1 was administrated to 104-week-old C57BL/6 mice for 6 weeks. The jejunum, colon and feces were collected for morphology, histology, gene expression and gut microbiota tests using H&E staining, X-gal staining, qPCR, Western blot, immunofluorescence staining, and 16S rDNA sequencing technologies. The numbers of cells reduced and the accumulation of senescent cells increased in the intestinal crypts of old mice, and administration of GRb1 could reverse them. The protein levels of CLDN 2, 3, 7, and 15 were all decreased in the jejunum of old mice, and administration of GRb1 could significantly increase them. The expression levels of Tert, Lgr5, mKi67, and c-Myc were all significantly reduced in the small intestines of old mice, and GRb1 significantly increased them at transcriptional or posttranscriptional levels. The protein levels of SIRT1, SIRT3, and SIRT6 were all reduced in the jejunum of old mice, and GRb1 could increase the protein levels of them. The 16S rDNA sequencing results demonstrated the dysbiosis of the gut microbiota of old mice, and GRb1 changed the composition and functions of the gut microbiota in the old mice. In conclusion, GRb1 could improve the intestinal aging via regulating the expression of Sirtuins family and modulating the gut microbiota in the aged mice.

Proteomic and phosphoproteomic profiling in heart failure with preserved ejection fraction (HFpEF)

Although the prevalence of heart failure with preserved ejection fraction (HFpEF) is increasing, evidence-based therapies for HFpEF remain limited, likely due to an incomplete understanding of this disease. This study sought to identify the cardiac-specific features of protein and phosphoprotein changes in a murine model of HFpEF using mass spectrometry. HFpEF mice demonstrated moderate hypertension, left ventricle (LV) hypertrophy, lung congestion and diastolic dysfunction. Proteomics analysis of the LV tissue showed that 897 proteins were differentially expressed between HFpEF and Sham mice. We observed abundant changes in sarcomeric proteins, mitochondrial-related proteins, and NAD-dependent protein deacetylase sirtuin-3 (SIRT3). Upregulated pathways by GSEA analysis were related to immune modulation and muscle contraction, while downregulated pathways were predominantly related to mitochondrial metabolism. Western blot analysis validated SIRT3 downregulated cardiac expression in HFpEF vs. Sham (0.8 ± 0.0 vs. 1.0 ± 0.0; P < 0.001). Phosphoproteomics analysis showed that 72 phosphosites were differentially regulated between HFpEF and Sham LV. Aberrant phosphorylation patterns mostly occurred in sarcomere proteins and nuclear-localized proteins associated with contractile dysfunction and cardiac hypertrophy. Seven aberrant phosphosites were observed at the z-disk binding region of titin. Additional agarose gel analysis showed that while total titin cardiac expression remained unaltered, its stiffer N2B isoform was significantly increased in HFpEF vs. Sham (0.144 ± 0.01 vs. 0.127 ± 0.01; P < 0.05). In summary, this study demonstrates marked changes in proteins related to mitochondrial metabolism and the cardiac contractile apparatus in HFpEF. We propose that SIRT3 may play a role in perpetuating these changes and may be a target for drug development in HFpEF.

The Role of SIRT3 in Exercise and Aging

The health benefits of regular exercise are well established. Nonetheless, the molecular mechanism(s) responsible for exercise-induced health benefits remain a topic of debate. One of the key cell-signaling candidates proposed to provide exercise-induced benefits is sirtuin 3 (SIRT3). SIRT3, an NAD+ dependent mitochondrial deacetylase, positively modulates many cellular processes, including energy metabolism, mitochondrial biogenesis, and protection against oxidative stress. Although the exercise-induced change in SIRT3 signaling is a potential mechanism contributing to the health advantages of exercise on aging, studies investigating the impact of exercise on SIRT3 abundance in cells provide conflicting results. To resolve this conundrum, this narrative review provides a detailed analysis of the role that exercise-induced changes in SIRT3 play in providing the health and aging benefits associated with regular physical activity. We begin with an overview of SIRT3 function in cells followed by a comprehensive review of the impact of exercise on SIRT3 expression in humans and other mammalians. We then discuss the impact of SIRT3 on aging, followed by a thorough analysis of the cell-signaling links between SIRT3 and exercise-induced adaptation. Notably, to stimulate future research, we conclude with a discussion of key unanswered questions related to exercise, aging, and SIRT3 expression.

SIRT3 regulates mitochondrial biogenesis in aging-related diseases

Sirtuin 3 (SIRT3), the main family member of mitochondrial deacetylase, targets the majority of substrates controlling mitochondrial biogenesis via lysine deacetylation and modulates important cellular functions such as energy metabolism, reactive oxygen species production and clearance, oxidative stress, and aging. Deletion of SIRT3 has a deleterious effect on mitochondrial biogenesis, thus leading to the defect in mitochondrial function and insufficient ATP production. Imbalance of mitochondrial dynamics leads to excessive mitochondrial biogenesis, dampening mitochondrial function. Mitochondrial dysfunction plays an important role in several diseases related to aging, such as cardiovascular disease, cancer and neurodegenerative diseases. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) launches mitochondrial biogenesis through activating nuclear respiratory factors. These factors act on genes, transcribing and translating mitochondrial DNA to generate new mitochondria. PGC1α builds a bridge between SIRT3 and mitochondrial biogenesis. This review described the involvement of SIRT3 and mitochondrial dynamics, particularly mitochondrial biogenesis in aging-related diseases, and further illustrated the role of the signaling events between SIRT3 and mitochondrial biogenesis in the pathological process of aging-related diseases.

The Double-Edged Sword of SIRT3 in Cancer and Its Therapeutic Applications

Reprogramming of cellular energy metabolism is considered an emerging feature of cancer. Mitochondrial metabolism plays a crucial role in cancer cell proliferation, survival, and metastasis. As a major mitochondrial NAD⁺-dependent deacetylase, sirtuin3 (SIRT3) deacetylates and regulates the enzymes involved in regulating mitochondrial energy metabolism, including fatty acid oxidation, the Krebs cycle, and the respiratory chain to maintain metabolic homeostasis. In this article, we review the multiple roles of SIRT3 in various cancers, and systematically summarize the recent advances in the discovery of its activators and inhibitors. The roles of SIRT3 vary in different cancers and have cell- and tumor-type specificity. SIRT3 plays a unique function by mediating interactions between mitochondria and intracellular signaling. The critical functions of SIRT3 have renewed interest in the development of small molecule modulators that regulate its activity. Delineation of the underlying mechanism of SIRT3 as a critical regulator of cell metabolism and further characterization of the mitochondrial substrates of SIRT3 will deepen our understanding of the role of SIRT3 in tumorigenesis and progression and may provide novel therapeutic strategies for cancer targeting SIRT3.

The Unfolded Protein Responses in Health, Aging, and Neurodegeneration: Recent Advances and Future Considerations

Aging and age-related neurodegeneration are both associated with the accumulation of unfolded and abnormally folded proteins, highlighting the importance of protein homeostasis (termed proteostasis) in maintaining organismal health. To this end, two cellular compartments with essential protein folding functions, the endoplasmic reticulum (ER) and the mitochondria, are equipped with unique protein stress responses, known as the ER unfolded protein response (UPR ER ) and the mitochondrial UPR (UPR mt ), respectively. These organellar UPRs play roles in shaping the cellular responses to proteostatic stress that occurs in aging and age-related neurodegeneration. The loss of adaptive UPR ER and UPR mt signaling potency with age contributes to a feed-forward cycle of increasing protein stress and cellular dysfunction. Likewise, UPR ER and UPR mt signaling is often altered in age-related neurodegenerative diseases; however, whether these changes counteract or contribute to the disease pathology appears to be context dependent. Intriguingly, altering organellar UPR signaling in animal models can reduce the pathological consequences of aging and neurodegeneration which has prompted clinical investigations of UPR signaling modulators as therapeutics. Here, we review the physiology of both the UPR ER and the UPR mt , discuss how UPR ER and UPR mt signaling changes in the context of aging and neurodegeneration, and highlight therapeutic strategies targeting the UPR ER and UPR mt that may improve human health.

Molecular mechanisms of dietary restriction promoting health and longevity

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

Sirtuin 3 (SIRT3) Pathways in Age-Related Cardiovascular and Neurodegenerative Diseases

Age-associated cardiovascular and neurodegenerative diseases lead to high morbidity and mortality around the world. Sirtuins are vital enzymes for metabolic adaptation and provide protective effects against a wide spectrum of pathologies. Among sirtuins, mitochondrial sirtuin 3 (SIRT3) is an essential player in preserving the habitual metabolic profile. SIRT3 activity declines as a result of aging-induced changes in cellular metabolism, leading to increased susceptibility to endothelial dysfunction, hypertension, heart failure and neurodegenerative diseases. Stimulating SIRT3 activity via lifestyle, pharmacological or genetic interventions could protect against a plethora of pathologies and could improve health and lifespan. Thus, understanding how SIRT3 operates and how its protective effects could be amplified, will aid in treating age-associated diseases and ultimately, in enhancing the quality of life in elders.

Therapeutic Potential of Mitophagy-Inducing Microflora Metabolite, Urolithin A for Alzheimer's Disease

Mitochondrial dysfunction including deficits of mitophagy is seen in aging and neurodegenerative disorders including Alzheimer’s disease (AD). Apart from traditionally targeting amyloid beta (Aβ), the main culprit in AD brains, other approaches include investigating impaired mitochondrial pathways for potential therapeutic benefits against AD. Thus, a future therapy for AD may focus on novel candidates that enhance optimal mitochondrial integrity and turnover. Bioactive food components, known as nutraceuticals, may serve as such agents to combat AD. Urolithin A is an intestinal microbe-derived metabolite of a class of polyphenols, ellagitannins (ETs). Urolithin A is known to exert many health benefits. Its antioxidant, anti-inflammatory, anti-atherogenic, anti-Aβ, and pro-mitophagy properties are increasingly recognized. However, the underlying mechanisms of urolithin A in inducing mitophagy is poorly understood. This review discusses the mitophagy deficits in AD and examines potential molecular mechanisms of its activation. Moreover, the current knowledge of urolithin A is discussed, focusing on its neuroprotective properties and its potential to induce mitophagy. Specifically, this review proposes potential mechanisms by which urolithin A may activate and promote mitophagy.

Are the estrogen receptor and SIRT3 axes of the mitochondrial UPR key regulators of breast cancer sub-type determination according to age?

Aging is a major risk factor of developing breast cancer. Despite the fact that post-menopausal women have lower levels of estrogen, older women have a higher rate of estrogen receptor alpha (ERα) positive breast cancer. Conversely, young women who have elevated levels of estrogen tend to develop ERα negative disease that is associated with higher rate of metastasis. This perspective proposes a unifying model centered around the importance of mitochondrial biology in cancer and aging to explain these observations. Mitochondria are essential for the survival of cancer cells and therefore pathways that maintain the functionality of the mitochondrial network in cancer cells fulfill a critical role in the survival of cancer cells. The ERα and the mitochondrial sirtuin-3 (SIRT3) have been reported to be key players of the mitochondrial unfolded protein response (UPR^mt) ^1-5. The UPR^mt is a complex retrograde signaling cascade that regulates the communication between the mitochondria and the nucleus to restore mitochondrial fitness in response to oxidative stress ^5-7. SIRT3 is a major regulator of aging ⁸. Its level decreases with age and single nucleotide polymorphisms (SNPs) that preserve its expression at higher levels are observed in centenarians ^9,10. We propose a model whereby the ERα axis of the UPR^mt acts to compensate for the loss of SIRT3 observed with age, and becomes the dominant axis of the UPR^mt to maintain the integrity of the mitochondria during transformation, thus explaining the selective advantage of ERα positive luminal cells in breast cancer arising from older women.

Sirtuins and Renal Oxidative Stress

Renal failure is a major health problem that is increasing worldwide. To improve clinical outcomes, we need to understand the basic mechanisms of kidney disease. Aging is a risk factor for the development and progression of kidney disease. Cells develop an imbalance of oxidants and antioxidants as they age, resulting in oxidative stress and the development of kidney damage. Calorie restriction (CR) is recognized as a dietary approach that promotes longevity, reduces oxidative stress, and delays the onset of age-related diseases. Sirtuins, a type of nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylase, are considered to be anti-aging molecules, and CR induces their expression. The sirtuin family consists of seven enzymes (Sirt1–7) that are involved in processes and functions related to antioxidant and oxidative stress, such as DNA damage repair and metabolism through histone and protein deacetylation. In fact, a role for sirtuins in the regulation of antioxidants and redox substances has been suggested. Therefore, the activation of sirtuins in the kidney may represent a novel therapeutic strategy to enhancing resistance to many causative factors in kidney disease through the reduction of oxidative stress. In this review, we discuss the relationship between sirtuins and oxidative stress in renal disease.

SIRT3 consolidates heterochromatin and counteracts senescence

Sirtuin 3 (SIRT3) is an NAD⁺-dependent deacetylase linked to a broad range of physiological and pathological processes, including aging and aging-related diseases. However, the role of SIRT3 in regulating human stem cell homeostasis remains unclear. Here we found that SIRT3 expression was downregulated in senescent human mesenchymal stem cells (hMSCs). CRISPR/Cas9-mediated depletion of SIRT3 led to compromised nuclear integrity, loss of heterochromatin and accelerated senescence in hMSCs. Further analysis indicated that SIRT3 interacted with nuclear envelope proteins and heterochromatin-associated proteins. SIRT3 deficiency resulted in the detachment of genomic lamina-associated domains (LADs) from the nuclear lamina, increased chromatin accessibility and aberrant repetitive sequence transcription. The re-introduction of SIRT3 rescued the disorganized heterochromatin and the senescence phenotypes. Taken together, our study reveals a novel role for SIRT3 in stabilizing heterochromatin and counteracting hMSC senescence, providing new potential therapeutic targets to ameliorate aging-related diseases.

Protein signatures from blood plasma and urine suggest changes in vascular function and IL-12 signaling in elderly with a history of chronic diseases compared with an age-matched healthy cohort

Key processes characterizing human aging are immunosenescence and inflammaging. The capacity of the immune system to adequately respond to external perturbations (e.g., pathogens, injuries, and biochemical irritants) and to repair somatic mutations that may cause cancers or cellular senescence declines. An important goal remains to identify genetic or biochemical, predictive biomarkers for healthy aging. We recruited two cohorts in the age range 70 to 82, one afflicted by chronic illnesses (non-healthy aging, NHA) and the other in good health (healthy aging, HA). NHA criteria included major cardiovascular, neurodegenerative, and chronic pulmonary diseases, diabetes, and cancers. Quantitative analysis of forty proinflammatory cytokines in blood plasma and more than 500 proteins in urine was performed to identify candidate biomarkers for and biological pathway implications of healthy aging. Nine cytokines revealed lower quantities in blood plasma for the NHA compared with the HA groups (fold change > 1.5; p value < 0.025) including IL-12p40 and IL-12p70. We note that, sampling at two timepoints, intra-individual cytokine abundance patterns clustered in 86% of all 60 cases, indicative of person-specific, highly controlled multi-cytokine signatures in blood plasma. Twenty-three urinary proteins were differentially abundant (HA versus NHA; fold change > 1.5; p value < 0.01). Among the proteins increased in abundance in the HA cohort were glycoprotein MUC18, ephrin type-B receptor 4, matrix remodeling-associated protein 8, angiopoietin-related protein 2, K-cadherin, and plasma protease C1 inhibitor. These proteins have been linked to the extracellular matrix, cell adhesion, and vascular remodeling and repair processes. In silico network analysis identified the regulation of coagulation, antimicrobial humoral immune responses, and the IL-12 signaling pathway as enriched GO terms. To validate links of these preliminary biomarkers and IL-12 signaling with healthy aging, clinical studies using larger cohorts and functional characterization of the genes/proteins in cellular models of aging need to be conducted.

Icariin enhances youth-like features by attenuating the declined gut microbiota in the aged mice

We previously reported the neuroprotective effects of icariin in rat cortical neurons. Here, we present a study on icariin's anti-aging effect in 24-month aged mice by treating them with a single daily dose of 100 mg/kg of icariin for 15 consecutive days. Icariin treatment improved motor coordination and learning skills while lowered oxidative stress biomarkers in the serum, brain, kidney, and liver of the aged mice. In addition, icariin improved the intestinal integrity of the aged mice by upregulating tight junction adhesion molecules and the Paneth and goblet cells, along with the reduction of iNOS and pro-inflammatory cytokines (IL-1β, TNF-α, IL-2 and IL-6, and IL-12). Icariin treatments also significantly upregulated aging-related signaling molecules, Sirt 1, 3 & 6, Pot1α, BUB1b, FOXO1, Ep300, ANXA3, Calb1, SNAP25, and BDNF in old mice. Through gut microbiota (GM) analysis, we observed icariin-associated improvements in GM composition of aged mice by reinstating bacteria found in the young mice, while suppressing some bacteria found in the untreated old mice. To clarify whether icariin's anti-aging effect is rooted in the GM, we performed fecal microbiota transfer (FMT) from icariin-treated old mice to the old mice. FMT-recipients exhibited similar improvements in the rotarod score and age-related biomarkers as observed in the icariin-treated old mice. Equal or better improvement on the youth-like features was noticed when aged mice were FMT with feces from young mice. Our study shows that both direct treatments with icariin and fecal transplant from the icariin-treated aged mice produce similar anti-aging phenotypes in the aged mice. We prove that GM plays a pivotal role in the healing abilities of icariin. Icariin has the potentials to be developed as a medicine for the wellness of the aged adults.

Restoration of SIRT3 gene expression by airway delivery resolves age-associated persistent lung fibrosis in mice

Aging is a risk factor for progressive fibrotic disorders involving diverse organ systems, including the lung. Idiopathic pulmonary fibrosis, an age-associated degenerative lung disorder, is characterized by persistence of apoptosis-resistant myofibroblasts. In this report, we demonstrate that sirtuin-3 (SIRT3), a mitochondrial deacetylase, is downregulated in lungs of IPF human subjects and in mice subjected to lung injury. Over-expression of the SIRT3 cDNA via airway delivery restored capacity for fibrosis resolution in aged mice, in association with activation of the forkhead box transcription factor, FoxO3a, in fibroblasts, upregulation of pro-apoptotic members of the Bcl-2 family, and recovery of apoptosis susceptibility. While transforming growth factor-β1 reduced levels of SIRT3 and FoxO3a in lung fibroblasts, cell non-autonomous effects involving macrophage secreted products were necessary for SIRT3-mediated activation of FoxO3a. Together, these findings reveal a novel role of SIRT3 in pro-resolution macrophage functions that restore susceptibility to apoptosis in fibroblasts via a FoxO3a-dependent mechanism.

Role of sirtuins in bone biology: Potential implications for novel therapeutic strategies for osteoporosis

The decline in bone mass and bone strength and musculoskeletal problems associated with aging constitute a major challenge for affected individuals and the healthcare system globally. Sirtuins 1-7 (SIRT1-SIRT7) are a family of nicotinamide adenine dinucleotide-dependent deacetylases with remarkable abilities to promote longevity and counteract age-related diseases. Sirtuin knockout and transgenic models have provided novel insights into the function and signaling of these proteins in bone homeostasis. Studies have revealed that sirtuins play a critical role in normal skeletal development and homeostasis through their direct action on bone cells and that their dysregulation might contribute to different bone diseases. Preclinical studies have demonstrated that mice treated with sirtuin agonists show protection against age-related, postmenopausal, and immobilization-induced osteoporosis. These findings suggest that sirtuins could be potential targets for the modulation of the imbalance in bone remodeling and treatment of osteoporosis and other bone disorders. The aim of this review was to provide a comprehensive updated review of the current knowledge on sirtuin biology, focusing specifically on their roles in bone homeostasis and osteoporosis, and potential pharmacological interventions targeting sirtuins for the treatment of osteoporosis.

Neuroproteomics in Epilepsy: What Do We Know so Far?

Epilepsies are chronic neurological diseases that affect approximately 2% of the world population. In addition to being one of the most frequent neurological disorders, treatment for patients with epilepsy remains a challenge, because a proportion of patients do not respond to the antiseizure medications that are currently available. This results in a severe economic and social burden for patients, families, and the healthcare system. A characteristic common to all forms of epilepsy is the occurrence of epileptic seizures that are caused by abnormal neuronal discharges, leading to a clinical manifestation that is dependent on the affected brain region. It is generally accepted that an imbalance between neuronal excitation and inhibition generates the synchronic electrical activity leading to seizures. However, it is still unclear how a normal neural circuit becomes susceptible to the generation of seizures or how epileptogenesis is induced. Herein, we review the results of recent proteomic studies applied to investigate the underlying mechanisms leading to epilepsies and how these findings may impact research and treatment for these disorders.

Aging mechanisms-A perspective mostly from Drosophila

A mechanistic understanding of the natural aging process, which is distinct from aging-related disease mechanisms, is essential for developing interventions to extend lifespan or healthspan. Here, we discuss current trends in aging research and address conceptual and experimental challenges in the field. We examine various molecular markers implicated in aging with an emphasis on the role of heterochromatin and epigenetic changes. Studies in model organisms have been advantageous in elucidating conserved genetic and epigenetic mechanisms and assessing interventions that affect aging. We highlight the use of Drosophila, which allows controlled studies for evaluating genetic and environmental contributors to aging conveniently. Finally, we propose the use of novel methodologies and future strategies using Drosophila in aging research.

Protein signatures from blood plasma and urine suggest changes in vascular function and IL-12 signaling in elderly with a history of chronic diseases compared with an age-matched healthy cohort

Key processes characterizing human aging are immunosenescence and inflammaging. The capacity of the immune system to adequately respond to external perturbations (e.g., pathogens, injuries, and biochemical irritants) and to repair somatic mutations that may cause cancers or cellular senescence declines. An important goal remains to identify genetic or biochemical, predictive biomarkers for healthy aging. We recruited two cohorts in the age range 70 to 82, one afflicted by chronic illnesses (non-healthy aging, NHA) and the other in good health (healthy aging, HA). NHA criteria included major cardiovascular, neurodegenerative, and chronic pulmonary diseases, diabetes, and cancers. Quantitative analysis of forty proinflammatory cytokines in blood plasma and more than 500 proteins in urine was performed to identify candidate biomarkers for and biological pathway implications of healthy aging. Nine cytokines revealed lower quantities in blood plasma for the NHA compared with the HA groups (fold change > 1.5; p value < 0.025) including IL-12p40 and IL-12p70. We note that, sampling at two timepoints, intra-individual cytokine abundance patterns clustered in 86% of all 60 cases, indicative of person-specific, highly controlled multi-cytokine signatures in blood plasma. Twenty-three urinary proteins were differentially abundant (HA versus NHA; fold change > 1.5; p value < 0.01). Among the proteins increased in abundance in the HA cohort were glycoprotein MUC18, ephrin type-B receptor 4, matrix remodeling-associated protein 8, angiopoietin-related protein 2, K-cadherin, and plasma protease C1 inhibitor. These proteins have been linked to the extracellular matrix, cell adhesion, and vascular remodeling and repair processes. In silico network analysis identified the regulation of coagulation, antimicrobial humoral immune responses, and the IL-12 signaling pathway as enriched GO terms. To validate links of these preliminary biomarkers and IL-12 signaling with healthy aging, clinical studies using larger cohorts and functional characterization of the genes/proteins in cellular models of aging need to be conducted.

Sirtuins and their Biological Relevance in Aging and Age-Related Diseases

Sirtuins, initially described as histone deacetylases and gene silencers in yeast, are now known to have many more functions and to be much more abundant in living organisms. The increasing evidence of sirtuins in the field of ageing and age-related diseases indicates that they may provide novel targets for treating diseases associated with aging and perhaps extend human lifespan. Here, we summarize some of the recent discoveries in sirtuin biology that clearly implicate the functions of sirtuins in the regulation of aging and age-related diseases. Furthermore, human sirtuins are considered promising therapeutic targets for anti-aging and ageing-related diseases and have attracted interest in scientific communities to develop small molecule activators or drugs to ameliorate a wide range of ageing disorders. In this review, we also summarize the discovery and development status of sirtuin-targeted drug and further discuss the potential medical strategies of sirtuins in delaying aging and treating age-related diseases.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Microglia mediated neuroinflammation - signaling regulation and therapeutic considerations with special reference to some natural compounds

Neuroinflammation plays a central role in multiple neurodegenerative diseases and neurological disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), cerebral ischemic injury etc. In this connection, microglia, the key players in the central nervous system, mediate the inflammatory response process. In brain injuries, activated microglia can clear the cellular debris and invading pathogens and release neurotrophic factors; however, prolonged microglia activation may cause neuronal death through excessive release of inflammatory mediators. Therefore, it is of paramount importance to understand the underlying molecular mechanisms of microglia activation to design an effective therapeutic strategy to alleviate neuronal injury. Recent studies have shown that some natural compounds and herbal extracts possess anti-inflammatory properties that may suppress microglial activation and ameliorate neuroinflammation and hence are neuroprotective. In this review, we will update some of the common signaling pathways that regulate microglia activation. Among the various signaling pathways, the Notch-1, mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) have been reported to exacerbate microglia mediated neuroinflammation that is implicated in different neuropathological diseases. The search for natural compounds or agents, specifically those derived from natural herbal extracts such as Gastrodin, scutellarin, RG1 etc. has been the focus of many of our recent studies because they have been found to regulate microglia activation. The pharmacological effects of these agents and their potential mechanisms for regulating microglia activation are systematically reviewed here for a fuller understanding of their biochemical action and therapeutic potential for treatment of microglia mediated neuropathological diseases.

Mitochondrial Sirtuin 3: New emerging biological function and therapeutic target

Sirtuin 3 (SIRT3) is one of the most prominent deacetylases that can regulate acetylation levels in mitochondria, which are essential for eukaryotic life and inextricably linked to the metabolism of multiple organs. Hitherto, SIRT3 has been substantiated to be involved in almost all aspects of mitochondrial metabolism and homeostasis, protecting mitochondria from a variety of damage. Accumulating evidence has recently documented that SIRT3 is associated with many types of human diseases, including age-related diseases, cancer, heart disease and metabolic diseases, indicating that SIRT3 can be a potential therapeutic target. Here we focus on summarizing the intricate mechanisms of SIRT3 in human diseases, and recent notable advances in the field of small-molecule activators or inhibitors targeting SIRT3 as well as their potential therapeutic applications for future drug discovery.

The Role of Vascular Aging in Atherosclerotic Plaque Development and Vulnerability

BACKGROUND

The ongoing demographical shift is leading to an unprecedented aging of the population. As a consequence, the prevalence of age-related diseases, such as atherosclerosis and its thrombotic complications is set to increase in the near future. Endothelial dysfunction and vascular stiffening characterize arterial aging and set the stage for the development of cardiovascular diseases. Atherosclerotic plaques evolve over time, the extent to which these changes might affect their stability and predispose to sudden complications remains to be determined. Recent advances in imaging technology will allow for longitudinal prospective studies following the progression of plaque burden aimed at better characterizing changes over time associated with plaque stability or rupture. Oxidative stress and inflammation, firmly established driving forces of age-related CV dysfunction, also play an important role in atherosclerotic plaque destabilization and rupture. Several genes involved in lifespan determination are known regulator of redox cellular balance and pre-clinical evidence underlines their pathophysiological roles in age-related cardiovascular dysfunction and atherosclerosis.

OBJECTIVE

The aim of this narrative review is to examine the impact of aging on arterial function and atherosclerotic plaque development. Furthermore, we report how molecular mechanisms of vascular aging might regulate age-related plaque modifications and how this may help to identify novel therapeutic targets to attenuate the increased risk of CV disease in elderly people.

The dominant model analysis of Sirt3 genetic variants is associated with susceptibility to tuberculosis in a Chinese Han population

Tuberculosis (TB) is a complex infectious disease caused by the pathogen Mycobacterium tuberculosis (Mtb) which has coexisted with humanity since the Neolithic. Recent research indicated that SIRT3 plays a pivotal role in promoting the antimycobacterial response of mitochondria and autophagy during Mtb infection. A case-control study comprised 900 TB patients and 1534 healthy controls who were retrospectively enrolled to assess the association between Sirt3 gene polymorphisms and TB susceptibility. In total, five single-nucleotide polymorphisms (SNPs) (rs511744, rs3782118, rs7104764, rs536715 and rs28365927) were selected through database 1000 Genomes Project and offline software Haploview V4.2 and genotyped by a customized 2 × 48-Plex SNPscan™ Kit. Our results suggested that the minor allele genotypes (A carriers) of rs3782118 confers the decreased risk of TB susceptibility (p_Bonferroni = 0.032), and a similar but more significant effect was observed under the dominant model analysis (OR 0.787, 95% CI 0.666-0.931, p_Bonferroni = 0.026). Haplotype analysis showed that haplotype AGAAG (rs511744/rs3782118/rs7104764/rs536715/rs28365927) was associated with an increased risk of TB (p = 0.023, OR 1.159, 95% CI 1.019-1.317). In stratification analysis, we found that rs3782118 was associated with decreased risk of TB in female subgroup under the dominant model analysis (p_Bonferroni = 0.016, OR 0.678, 95% CI 0.523-0.878). Moreover, functional annotations for three loci (rs7930823, rs3782116 and rs3782115) which are strongly linked to rs3782118 indicated that they may be responsible for the changes in some motifs. In conclusion, our study suggested that the SNP rs3782118 was associated with a lower susceptibility to TB, especially under the dominant model analysis and that the haplotype AGAAG (containing the major allele G of rs3782118) was associated with an increased risk of TB. Further independent cohort studies are necessary to validate the protective effect of Sirt3 genetic variants on the risk of TB.

Gastro-intestinal and oral microbiome signatures associated with healthy aging

The human oral and gut microbiomes influence health via competition for a distinct niche in the body with pathogens, via metabolic capabilities that increase host digestive capacity and generate compounds engaged in signaling pathways and modulation of immune system functions. Old age alters our metabolic and regenerative capacity. Following recruitment of 65 human subjects in the age range of 70 to 82, we discerned healthy aging (HA) and non-healthy aging (NHA) cohorts discordant in the occurrence of one or more major diseases: (1) cancer, (2) acute or chronic cardiovascular diseases, (3) acute or chronic pulmonary diseases, (4) diabetes, and (5) stroke or neurodegenerative disorders. We analyzed these cohorts' oral microbiomes (saliva) and gut microbiomes (stool) to assess diversity and identify microbial biomarkers for HA. In contrast to the gut microbiome where no change was observed, we found that the saliva microbiome had higher α-diversity in the HA compared with the NHA group. We observed the genus Akkermansia to be significantly more abundant in the gut microbiota of the HA group. Akkermansia muciniphila is a colonic mucin-degrading bacterium believed to have beneficial effects on gastrointestinal health, particularly in the context of diabetes and obesity. Erysipelotrichaceae UCG-003 was a taxon increased in abundance in the HA cohort. Streptococcus was the only genus observed to be significantly decreased in abundance in both the gut and oral microbiomes of the HA cohort compared with the NHA cohort. Our data support the notion that these microbes are potential probiotics to decrease the risks of non-healthy aging.

The nuclear and mitochondrial sirtuins, Sirt6 and Sirt3, regulate each other's activity and protect the heart from developing obesity-mediated diabetic cardiomyopathy

Sirtuins (Sirts) are implicated in regulating a myriad of biologic functions ranging from cell growth and metabolism to longevity. Here, we show that nuclear Sirt, Sirt6, and mitochondrial Sirt, Sirt3, regulate each other's activity and protect the heart from developing diabetic cardiomyopathy. We found that expression of both Sirt6 and Sirt3 was reduced in cardiomyocytes treated with palmitate and in hearts of mice fed with a high-fat, high-sucrose (HF-HS) diet to develop obesity and diabetes. Conversely, whole-body overexpressing Sirt6 transgenic (Tg.Sirt6) mice were protected from developing obesity and insulin resistance when fed with the same HF-HS diet. The hearts of Tg.Sirt6 mice were also protected from mitochondrial fragmentation and decline of Sirt3, resulting otherwise from HF-HS diet feeding. Mechanistic studies showed that Sirt3 preserves Sirt6 levels by reducing oxidative stress, whereas Sirt6 maintains Sirt3 levels by up-regulating nuclear respiratory factor 2 (Nrf2)-dependent Sirt3 gene transcription. We found that Sirt6 regulates Nrf2-mediated cardiac gene expression in 2 ways; first, Sirt6 suppresses expression of Kelch-like ECH-associated protein 1 (Keap1), a negative regulator of Nrf2, and second, Sirt6 binds to Nrf2 and antagonizes its interaction with Keap1, thereby stabilizing Nrf2 levels in cardiomyocytes. Together, these studies demonstrate that Sirt6 and Sirt3 maintain each other's activity and protect the heart from developing diabetic cardiomyopathy.-Kanwal, A., Pillai, V. B., Samant, S., Gupta, M., Gupta, M. P. The nuclear and mitochondrial sirtuins, Sirt6 and Sirt3, regulate each other's activity and protect the heart from developing obesity-mediated diabetic cardiomyopathy.

Genetics of Human Longevity Within an Eco-Evolutionary Nature-Nurture Framework

Human longevity is a complex trait, and to disentangle its basis has a great theoretical and practical consequences for biomedicine. The genetics of human longevity is still poorly understood despite several investigations that used different strategies and protocols. Here, we argue that such rather disappointing harvest is largely because of the extraordinary complexity of the longevity phenotype in humans. The capability to reach the extreme decades of human lifespan seems to be the result of an intriguing mixture of gene-environment interactions. Accordingly, the genetics of human longevity is here described as a highly context-dependent phenomenon, within a new integrated, ecological, and evolutionary perspective, and is presented as a dynamic process, both historically and individually. The available literature has been scrutinized within this perspective, paying particular attention to factors (sex, individual biography, family, population ancestry, social structure, economic status, and education, among others) that have been relatively neglected. The strength and limitations of the most powerful and used tools, such as genome-wide association study and whole-genome sequencing, have been discussed, focusing on prominently emerged genes and regions, such as apolipoprotein E, Forkhead box O3, interleukin 6, insulin-like growth factor-1, chromosome 9p21, 5q33.3, and somatic mutations among others. The major results of this approach suggest that (1) the genetics of longevity is highly population specific; (2) small-effect alleles, pleiotropy, and the complex allele timing likely play a major role; (3) genetic risk factors are age specific and need to be integrated in the light of the geroscience perspective; (4) a close relationship between genetics of longevity and genetics of age-related diseases (especially cardiovascular diseases) do exist. Finally, the urgent need of a global approach to the largely unexplored interactions between the 3 genetics of human body, that is, nuclear, mitochondrial, and microbiomes, is stressed. We surmise that the comprehensive approach here presented will help in increasing the above-mentioned harvest.

Sirtuin 3 Therapy Attenuates Aging Expression, Oxidative Stress Parameters, and Neointimal Hyperplasia Formation in Vein Grafts

BACKGROUND

Vein graft (VG) failure due to neointimal hyperplasia remains an important and unresolved problem in cardiovascular surgery. Sirtuin3 (SIRT3) is associated with oxidative stress and lifespan. We aimed to measure SIRT3 expression in the veins of humans and rats during aging, explore the inhibitory effects of SIRT3 on vascular smooth muscle cell (VSMC) proliferation and neointimal hyperplasia in VGs, and investigate the underlying mechanisms.

METHODS

SIRT3 mRNA and protein levels in saphenous veins of young and older humans and in veins of young and old rats were measured by quantitative real-time polymerized chain reaction (PCR) and Western blot analysis. Young and old male rats were randomized to the control (control), graft (graft), adenovirus-encoding green fluorescent protein (Ad-GFP), and adenovirus encoding SIRT3 (Ad-SIRT3) groups. At 7 days after operation, the mRNA and protein levels of SIRT3 and endothelial nitric oxide synthase (eNOS) were measured by quantitative real-time PCR and Western blot analysis. The mRNA levels and enzyme activity of manganese superoxide dismutase (MnSOD) and catalase (CAT) were measured by quantitative real-time PCR and enzymatic activity assay kits, and total nitric oxide (NO) levels were measured by biochemical assay kits. Histomorphometric analysis of VGs and immunohistochemical staining for proliferative activity were performed at 4 weeks after operation. The hemodynamic parameters of the VGs were also measured by ultrasonic examination.

RESULTS

SIRT3 mRNA and protein levels were lower in older human and rat veins than in younger human and rat veins. Ad-SIRT3 treatment significantly increased the expression and concentration of SIRT3, MnSOD, CAT, eNOS, and NO in VGs at 7 days after operation. Ad-SIRT3 gene transfer reduced the neointimal thickness and neointimal area/media area ratio in the VGs of the Ad-SIRT3 groups compared with the graft and Ad-GFP groups, especially in old rats. Proliferative activity was lower in the Ad-SIRT3 groups than in the other groups. The hemodynamic parameters of VGs were obviously improved in the Ad-SIRT3 groups.

CONCLUSIONS

SIRT3 expression decreases in the veins of humans and rats during aging. Furthermore, SIRT3 overexpression can significantly reduce VSMC proliferation and neointimal hyperplasia in VGs. Local intravenous delivery of adenovirus encoding SIRT3 may be a promising gene therapy for preventing VG failure.

Genetic and epigenetic regulation of human aging and longevity

Here we summarize the latest data on genetic and epigenetic contributions to human aging and longevity. Whereas environmental and lifestyle factors are important at younger ages, the contribution of genetics appears more important in reaching extreme old age. Genome-wide studies have implicated ~57 gene loci in lifespan. Epigenomic changes during aging profoundly affect cellular function and stress resistance. Dysregulation of transcriptional and chromatin networks is likely a crucial component of aging. Large-scale bioinformatic analyses have revealed involvement of numerous interaction networks. As the young well-differentiated cell replicates into eventual senescence there is drift in the highly regulated chromatin marks towards an entropic middle-ground between repressed and active, such that genes that were previously inactive "leak". There is a breakdown in chromatin connectivity such that topologically associated domains and their insulators weaken, and well-defined blocks of constitutive heterochromatin give way to generalized, senescence-associated heterochromatin, foci. Together, these phenomena contribute to aging.

Nuclear Genomic Instability and Aging

The nuclear genome decays as organisms age. Numerous studies demonstrate that the burden of several classes of DNA lesions is greater in older mammals than in young mammals. More challenging is proving this is a cause rather than a consequence of aging. The DNA damage theory of aging, which argues that genomic instability plays a causal role in aging, has recently gained momentum. Support for this theory stems partly from progeroid syndromes in which inherited defects in DNA repair increase the burden of DNA damage leading to accelerated aging of one or more organs. Additionally, growing evidence shows that DNA damage accrual triggers cellular senescence and metabolic changes that promote a decline in tissue function and increased susceptibility to age-related diseases. Here, we examine multiple lines of evidence correlating nuclear DNA damage with aging. We then consider how, mechanistically, nuclear genotoxic stress could promote aging. We conclude that the evidence, in toto, supports a role for DNA damage as a nidus of aging.

Sirtuin signaling in cellular senescence and aging

Sirtuin is an essential factor that delays cellular senescence and extends the organismal lifespan through the regulation of diverse cellular processes. Suppression of cellular senescence by Sirtuin is mainly mediated through delaying the age-related telomere attrition, sustaining genome integrity and promotion of DNA damage repair. In addition, Sirtuin modulates the organismal lifespan by interacting with several lifespan regulating signaling pathways including insulin/IGF-1 signaling pathway, AMP-activated protein kinase, and forkhead box O. Although still controversial, it is suggested that the prolongevity effect of Sirtuin is dependent with the level of and with the tissue expression of Sirtuin. Since Sirtuin is also believed to mediate the prolongevity effect of calorie restriction, activators of Sirtuin have attracted the attention of researchers to develop therapeutics for age-related diseases. Resveratrol, a phytochemical rich in the skin of red grapes and wine, has been actively investigated to activate Sirtuin activity with consequent beneficial effects on aging. This article reviews the evidences and controversies regarding the roles of Sirtuin on cellular senescence and lifespan extension, and summarizes the activators of Sirtuin including Sirtuin-activating compounds and compounds that increase the cellular level of nicotinamide dinucleotide.

Microvascular Rarefaction and Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and is commonly seen in the elderly and diabetic and hypertensive patients. Despite its rising prevalence, the pathophysiology of HFpEF is poorly understood and its optimal treatment remains undefined. Recent clinical studies indicate that coronary microvascular rarefaction (reduced myocardial capillary density) with reduced coronary flow reserve (CFR) is a major contributor to diastolic dysfunction in HFpEF patients. On a molecular level, endothelial cells (EC) are dependent on glycolysis for supporting their functions and vascular homeostasis. Sirtuin 3 (SIRT3) has a critical role in the regulation of endothelial glycolytic metabolism and thus affects angiogenesis. Disruption of SIRT3-mediated EC metabolism and impairment of angiogenesis may promote cardiomyocyte hypoxia and myocardial fibrosis, leading to diastolic dysfunction and HFpEF. This review summarizes current knowledge of SIRT3 in EC metabolism, coronary microvascular rarefaction and HFpEF.

Sirtuins and Type 2 Diabetes: Role in Inflammation, Oxidative Stress, and Mitochondrial Function

The rising incidence of type 2 diabetes mellitus (T2DM) is a major public health concern, and novel therapeutic strategies to prevent T2DM are urgently needed worldwide. Aging is recognized as one of the risk factors for metabolic impairments, including insulin resistance and T2DM. Inflammation, oxidative stress, and mitochondrial dysfunction are closely related to both aging and metabolic disease. Calorie restriction (CR) can retard the aging process in organisms ranging from yeast to rodents and delay the onset of numerous age-related disorders, such as insulin resistance and diabetes. Therefore, metabolic CR mimetics may represent new therapeutic targets for insulin resistance and T2DM. Sirtuin 1 (SIRT1), the mammalian homolog of Sir2, was originally identified as a nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase. The activation of SIRT1 is closely associated with longevity under CR, and it is recognized as a CR mimetic. Currently, seven sirtuins have been identified in mammals. Among these sirtuins, SIRT1 and SIRT2 are located in the nucleus and cytoplasm, SIRT3 exists predominantly in mitochondria, and SIRT6 is located in the nucleus. These sirtuins regulate metabolism through their regulation of inflammation, oxidative stress and mitochondrial function via multiple mechanisms, resulting in the improvement of insulin resistance and T2DM. In this review, we describe the current understanding of the biological functions of sirtuins, especially SIRT1, SIRT2, SIRT3, and SIRT6, focusing on oxidative stress, inflammation, and mitochondrial function, which are closely associated with aging.

Mechanisms of Age-Dependent Loss of Dietary Restriction Protective Effects in Acute Kidney Injury

Dietary restriction (DR) is one of the most efficient approaches ameliorating the severity of different pathological conditions including aging. We investigated the protective potential of short-term DR in the model of acute kidney injury (AKI) in young and old rats. In kidney tissue, the levels of autophagy and mitophagy were examined, and proliferative properties of renal cells obtained from rats of different age were compared. DR afforded a significant nephroprotection to ischemic kidneys of young rats. However, in old rats, DR did not provide such beneficial effect. On the assessment of the autophagy marker, the LC3 II/LC3 I ratio, and after staining the tissue with LysoTracker Green, we concluded that in old rats activity of the autophagic-lysosomal system decreased. Mitophagy, as assessed by the levels of PINK-1, was also deteriorated in old animals. Renal cells from old rats showed impaired proliferative capacity, a worse rate of recovery after ischemic injury, increased levels of oxidative stress, accumulation of lipofuscin granules and lower mitochondria membrane potential. The results suggest that the loss of DR benefits in old animals could be due to deterioration in the autophagy/mitophagy flux.

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.

Acetylation of Mitochondrial Proteins in the Heart: The Role of SIRT3

A growing number of studies have demonstrated the role of post-translational modifications of proteins, particularly acetylation, in human diseases including neurodegenerative and cardiovascular diseases, diabetes, cancer, and in aging. Acetylation of mitochondrial proteins has been shown to be involved in the pathogenesis of cardiac diseases such as myocardial infarction (ischemia-reperfusion) and heart failure. Indeed, over 60% of mitochondrial proteins contain acetylation sites, and most of these proteins are involved in mitochondrial bioenergetics. Mitochondrial non-enzymatic acetylation is enabled by acetyl-coenzyme A abundance and serves as the primary pathway of acetylation in mitochondria. Hence, regulation of enzymatic deacetylation becomes the most important mechanism to control acetylation/deacetylation of mitochondrial proteins. Acetylation/deacetylation of mitochondrial proteins has been regarded as a key regulator of mitochondrial metabolism and function. Proteins are deacetylated by NAD⁺-dependent deacetylases known as sirtuins (SIRTs). Among seven sirtuin isoforms, only SIRT3, SIRT4, and SIRT5 are localized in the mitochondria. SIRT3 is the main mitochondrial sirtuin which plays a key role in maintaining metabolic and redox balance in the mitochondria under physiological and pathological conditions. SIRT3 regulates the enzymatic activity of proteins involved in fatty acid oxidation, tricarboxylic acid cycle, electron transport chain, and oxidative phosphorylation. Although many enzymes have been identified as targets for SIRT3, cardiac-specific SIRT3 effects and regulations could differ from those in non-cardiac tissues. Therefore, it is important to elucidate the contribution of SIRT3 and mitochondrial protein acetylation/deacetylation in mitochondrial metabolism and cardiac dysfunction. Here, we summarize previous studies and provide a comprehensive analysis of the role of SIRT3 in mitochondria metabolism and bioenergetics under physiological conditions and in cardiac diseases. In addition, the review discusses mitochondrial protein acetylation as a potential target for cardioprotection.

Enhanced longevity and metabolism by brown adipose tissue with disruption of the regulator of G protein signaling 14

Disruption of the regulator for G protein signaling 14 (RGS14) knockout (KO) in mice extends their lifespan and has multiple beneficial effects related to healthful aging, that is, protection from obesity, as reflected by reduced white adipose tissue, protection against cold exposure, and improved metabolism. The observed beneficial effects were mediated by improved mitochondrial function. But most importantly, the main mechanism responsible for the salutary properties of the RGS14 KO involved an increase in brown adipose tissue (BAT), which was confirmed by surgical BAT removal and transplantation to wild-type (WT) mice, a surgical simulation of a molecular knockout. This technique reversed the phenotype of the RGS14 KO and WT, resulting in loss of the improved metabolism and protection against cold exposure in RGS14 KO and conferring this protection to the WT BAT recipients. Another mechanism mediating the salutary features in the RGS14 KO was increased SIRT3. This mechanism was confirmed in the RGS14 X SIRT3 double KO, which no longer demonstrated improved metabolism and protection against cold exposure. Loss of function of the Caenorhabditis elegans RGS-14 homolog confirmed the evolutionary conservation of this mechanism. Thus, disruption of RGS14 is a model of healthful aging, as it not only enhances lifespan, but also protects against obesity and cold exposure and improves metabolism with a key mechanism of increased BAT, which, when removed, eliminates the features of healthful aging.

Gastrodin attenuates microglia activation through renin-angiotensin system and Sirtuin3 pathway

Microglia activation and its mediated production of proinflammatory mediators play important roles in different neurodegenerative diseases; hence, modulation of microglia activation has been considered a potential therapeutic strategy to ameliorate neurodegeneration. This study was aimed to determine whether Gastrodin, a common herbal agent known to possess neuroprotective property, can attenuate production of proinflammatory mediators in activated microglia through the renin-angiotensin system (RAS) and Sirtuin3 (SIRT3). Expression of various members of the RAS including ACE, AT₁, AT_2, and SIRT3 in activated microglia was assessed by immunofluorescence and Western blot in hypoxic-ischemia brain damage (HIBD) in postnatal rats, and in BV-2 microglia in vitro challenged with lipopolysaccharide (LPS) with or without Gastrodin treatment. Expression of NOX-2, a subunit of NADPH oxidase, and proinflammatory mediators including iNOS and TNF-α, was also evaluated. The present results showed that expression of ACE, AT₁, NOX-2, iNOS and TNF-α was markedly increased in activated microglia in the corpus callosum of HIBD rats, and in LPS stimulated BV-2 microglia. Remarkably, the expression was markedly attenuated following Gastrodin treatment. Conversely, Gastrodin enhanced AT₂ and SIRT3 protein expression. In BV-2 microglia treated with Azilsartan, a specific inhibitor of AT₁ (AT₁I group), NOX-2 expression was decreased whereas that of SIRT3 in LPS + AT₁I and LPS + Gastrodin group was increased when compared with the controls. In LPS + AT₁I + Gastrodin group, SIRT3 expression was further augmented. More importantly, Gastrodin effectively reduced caspase 3 protein expression level in the HIBD rats coupled with a significant decrease in caspase 3 positive cells. We conclude that Gastrodin can exert its protective effects against the hypoxic-ischemia brain damage in the present experimental HIBD model. It is suggested that this is mainly through suppression of expression of RAS (except for AT₂ and SIRT3) and proinflammatory mediators e.g. TNF-α in activated microglia.