SIRT6 in Vascular Diseases, from Bench to Bedside

Application of crotonylation modification in pan-vascular diseases

Pan-vascular diseases, based on systems biology theory, explore the commonalities and individualities of important target organs such as cardiovascular, cerebrovascular and peripheral blood vessels, starting from the systemic and holistic aspects of vascular diseases. The purpose is to understand the interrelationships and results between them, achieve vascular health or sub-health, and comprehensively improve the physical and mental health of the entire population. Post-translational modification (PTM) is an important part of epigenetics, including phosphorylation, acetylation, ubiquitination, methylation, etc., playing a crucial role in the pan-vascular system. Crotonylation is a novel type of PTM that has made significant progress in the research of pan-vascular related diseases in recent years. Based on the review of previous studies, this article summarises the various regulatory factors of crotonylation, physiological functions and the mechanisms of histone and non-histone crotonylation in regulating pan-vascular related diseases to explore the possibility of precise regulation of crotonylation sites as potential targets for disease treatment and the value of clinical translation.

SIRT-associated attenuation of cellular senescence in vascular wall

This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Cardiovascular aging: spotlight on mitochondria

Mitochondria are cellular organelles critical for ATP production and are particularly relevant to cardiovascular diseases including heart failure, atherosclerosis, ischemia-reperfusion injury, and cardiomyopathies. With advancing age, even in the absence of clinical disease, mitochondrial homeostasis becomes disrupted (e.g., redox balance, mitochondrial DNA damage, oxidative metabolism, and mitochondrial quality control). Mitochondrial dysregulation leads to the accumulation of damaged and dysfunctional mitochondria, producing excessive reactive oxygen species and perpetuating mitochondrial dysfunction. In addition, mitochondrial DNA, cardiolipin, and N-formyl peptides are potent activators of cell-intrinsic and -extrinsic inflammatory pathways. These age-related mitochondrial changes contribute to the development of cardiovascular diseases. This review covers the impact of aging on mitochondria and links these mechanisms to therapeutic implications for age-associated cardiovascular diseases.

Role of the intestinal microbiome and its therapeutic intervention in cardiovascular disorder

The gut microbiome is a heterogeneous population of microbes comprising viruses, bacteria, fungi, and protozoa. Such a microbiome is essential for sustaining host equilibrium, and its impact on human health can be altered by a variety of factors such as external variables, social behavior, age, nutrition, and genetics. Gut microbes' imbalances are related to a variety of chronic diseases including cancer, obesity, and digestive disorders. Globally, recent findings show that intestinal microbes have a significant role in the formation of cardiovascular disease (CVD), which is still the primary cause of fatalities. Atherosclerosis, hypertension, diabetes, inflammation, and some inherited variables are all cardiovascular risk variables. However, studies found correlations between metabolism, intestinal flora, and dietary intake. Variations in the diversity of gut microbes and changes in their activity are thought to influence CVD etiology. Furthermore, the gut microbiota acts as an endocrine organ, producing bioactive metabolites such as TMA (trimethylamine)/TMAO (trimethylamine N-oxide), SCFA (short-chain fatty acids), and bile acids, which have a substantial impact on host wellness and disease by multiple mechanisms. The purpose of this overview is to compile current evidence highlighting the intricate links between gut microbiota, metabolites, and the development of CVD. It focuses on how intestinal dysbiosis promotes CVD risk factors such as heart failure, hypertension, and atherosclerosis. This review explores the normal physiology of intestinal microbes and potential techniques for targeting gut bacteria for CVD treatment using various microbial metabolites. It also examines the significance of gut bacteria in disease treatment, including supplements, prebiotics, probiotics, antibiotic therapies, and fecal transplantation, which is an innovative approach to the management of CVD. As a result, gut bacteria and metabolic pathways become increasingly attractive as potential targets for CVD intervention.

Helpful to Live Healthier? Intermittent Hypoxic/Ischemic Training Benefits Vascular Homeostasis and Lipid Metabolism with Activating SIRT1 Pathways in Overweight/Obese Individuals

INTRODUCTION

The present study aimed to investigate whether and how normobaric intermittent hypoxic training (IHT) or remote ischemic preconditioning (RIPC) plus normoxic training (RNT) has a synergistic protective effect on lipid metabolism and vascular function compared with normoxic training (NT) in overweight or obese adults.

METHODS

A total of 37 overweight or obese adults (36.03 ± 10.48 years) were randomly assigned to 3 groups: NT group (exercise intervention in normoxia), IHT group (exercise intervention in normobaric hypoxic chamber), and RNT group (exercise intervention in normoxia + RIPC twice daily). All participants carried out the same 1-h exercise intervention for a total of 4 weeks, 5 days per week. Physical fitness parameters were evaluated at pre- and postexercise intervention.

RESULTS

After training, all three groups had a significantly decreased body mass index (p < 0.05). The IHT group had reduced body fat percentage, visceral fat mass (p < 0.05), blood pressure (p < 0.01), left ankle-brachial index (ABI), maximal heart rate (HRmax) (p < 0.05), expression of peroxisome proliferator-activated receptor-γ (PPARγ) (p < 0.01) and increased expression of SIRT1 (p < 0.05), VEGF (p < 0.01). The RNT group had lowered waist-to-hip ratio, visceral fat mass, blood pressure (p < 0.05), and HRmax (p < 0.01).

CONCLUSION

IHT could effectively reduce visceral fat mass and improve vascular elasticity in overweight or obese individuals than pure NT with the activation of SIRT1-related pathways. And RNT also produced similar benefits on body composition and vascular function, which were weaker than those of IHT but stronger than NT. Given the convenience and economy of RNT, both intermittent hypoxic and ischemic training have the potential to be successful health promotion strategies for the overweight/obese population.

Correlation of MicroRNA-125b, Sirtuin, and Signal Transducer and Activator of Transcription 3 with Biochemical Parameters and Risk Factors in Atherosclerosis Patients

Background

Atherosclerosis (AS) is an inflammatory disease linked to vascular events, with dysregulation of microRNA (miR)-125b, contributing to cardiovascular disease pathogenesis. Moreover, there is evidence of the involvement of signal transducer and activator of transcription 3 (STAT3) and sirtuin 6 (SIRT6) in AS. This study aimed to survey the expression levels of miR-125b, STAT3, and SIRT6 in the peripheral blood mononuclear cells (PBMCs) of AS patients and controls, and to find their correlations with biochemical parameters and risk factors.

Methods

This study included blood samples from 45 controls and 45 AS patients, with PBMCs isolated using Ficoll solution. Expression levels of miR-125b, STAT3, and SIRT6 were determined via quantitative Real Time-PCR.

Results

The findings revealed a significant increase in miR-125b levels in patients compared to controls (P = 0.017). However, alterations in STAT3 and SIRT6 expression were not significant (P> 0.05). There was no substantial relationship between miR-125b and STAT3 (P = 0.522) or SIRT6 (P = 0.88). miR-125b showed a significant relationship with atherogenic indexes and creatinine (P<0.05), while the association of SIRT6 with HDL and creatinine was significant (P<0.05). STAT3 exhibited high diagnostic power for identifying individuals at risk of heart disease and hypertension (P<0.05).

Conclusion

STAT3 can serve as a valuable biomarker for detecting AS and AS-related risk factors. miR-125b and SIRT6 may be associated with AS lipid metabolism. However, further studies with larger sample sizes are recommended to mechanistically elucidate the association of these genes.

Histidine Triad Nucleotide-Binding Protein 1 Improves Critical Limb Ischemia by Regulating Mitochondrial Homeostasis

Critical limb ischemia (CLI) is a common complication of diabetes mellitus that typically occurs in the later stages of the disease. Vascularization is indeed an important physiological process involving the formation of new blood vessels from existing ones. It occurs in response to various normal and pathophysiological conditions, and one of its critical roles is to compensate for inadequate oxygen supply, which is often seen in situations like chronic limb ischemia (CLI). Histidine triad nucleotide-binding protein 1 (Hint1) is a member of the Hint family that has been shown to attenuate cardiac hypertrophy, but its role in vascularization still needs to be clarified. In this study, we investigated the role of Hint1 in CLI. We found that Hint1 is significantly reduced in the muscle tissue of STZ-induced diabetic mice and high-glucose (HG)-treated endothelial cells (ECs). Hint1 deletion impaired blood flow recovery and vascularization, whereas Hint1 overexpression promoted these processes. In addition, our in vitro study showed that Hint1 deficiency aggravated mitochondrial dysfunction in ECs, as evidenced by impaired mitochondrial respiration, decreased mitochondrial membrane potential, and increased reactive oxygen species. Our findings suggest that Hint1 deficiency impairs blood perfusion by damaging mitochondrial function and that Hint1 may represent a potential therapeutic target for treating CLI.

Gut microbiota and microbiota-derived metabolites in cardiovascular diseases

ABSTRACT

Cardiovascular diseases, including heart failure, coronary artery disease, atherosclerosis, aneurysm, thrombosis, and hypertension, are a great economic burden and threat to human health and are the major cause of death worldwide. Recently, researchers have begun to appreciate the role of microbial ecosystems within the human body in contributing to metabolic and cardiovascular disorders. Accumulating evidence has demonstrated that the gut microbiota is closely associated with the occurrence and development of cardiovascular diseases. The gut microbiota functions as an endocrine organ that secretes bioactive metabolites that participate in the maintenance of cardiovascular homeostasis, and their dysfunction can directly influence the progression of cardiovascular disease. This review summarizes the current literature demonstrating the role of the gut microbiota in the development of cardiovascular diseases. We also highlight the mechanism by which well-documented gut microbiota-derived metabolites, especially trimethylamine N-oxide, short-chain fatty acids, and phenylacetylglutamine, promote or inhibit the pathogenesis of cardiovascular diseases. We also discuss the therapeutic potential of altering the gut microbiota and microbiota-derived metabolites to improve or prevent cardiovascular diseases.

The crosstalk between Nrf2 and NF-κB pathways in coronary artery disease: Can it be regulated by SIRT6?

Coronary artery disease (CAD) is the leading cause of death worldwide. Oxidative stress and inflammation are major mechanisms responsible for the progression of CAD. Nuclear transcription factor erythroid-2 related factor 2 (Nrf2) is a transcription factor that modulates the cellular redox status. Nrf2 upregulation increases the expression of antioxidant genes, decreases the expression of Nuclear factor-kappa B (NF-kB), and increases free radical metabolism. Activated NF-kB increases the production of inflammatory cytokines causing endothelial dysfunction. The two pathways of Nrf2 and NF-kB can regulate the expression of each other. Foremost, the Nrf2 pathway can decrease the level of active NF-κB by increasing the level of antioxidants and cytoprotective enzymes. Furthermore, the Nrf2 pathway prevents IκB-α degradation, an inhibitor of NF-kB, and thus inhibits NF-κB mediated transcription. Also, NF-kB transcription inhibits Nrf2 activation by reducing the antioxidant response element (ARE) transcription. Sirtuin 6 (SIRT6) is a member of the Sirtuins family that was found to protect against cardiovascular diseases. SIRT6 can suppress the production of Reactive oxygen species (ROS) through deacetylation of NRF2 which results in NRF2 activation. Furthermore, SIRT6 can inhibit the inflammatory process through the downregulation of NF-kB transcription. Therefore, targeting sirtuins could be a therapeutic strategy to treat CAD. This review describes the potential role of SIRT6 in regulating the crosstalk between NRF2 and NF-kB signaling pathways in CAD.

m 6A methylation in cellular senescence of age-associated diseases

Cellular senescence is a state of irreversible cellular growth arrest that occurs in response to various stresses. In addition to exiting the cell cycle, senescent cells undergo many phenotypic alterations, including metabolic reprogramming, chromatin rearrangement, and senescence-associated secretory phenotype (SASP) development. Furthermore, senescent cells can affect most physiological and pathological processes, such as physiological development; tissue homeostasis; tumour regression; and age-associated disease progression, including diabetes, atherosclerosis, Alzheimer's disease, and hypertension. Although corresponding anti-senescence therapies are actively being explored for the treatment of age-associated diseases, the specific regulatory mechanisms of senescence remain unclear. N 6-methyladenosine (m 6A), a chemical modification commonly distributed in eukaryotic RNA, plays an important role in biological processes such as translation, shearing, and RNA transcription. Numerous studies have shown that m 6A plays an important regulatory role in cellular senescence and aging-related disease. In this review, we systematically summarize the role of m 6A modifications in cellular senescence with regard to oxidative stress, DNA damage, telomere alterations, and SASP development. Additionally, diabetes, atherosclerosis, and Alzheimer's disease regulation via m 6A-mediated cellular senescence is discussed. We further discuss the challenges and prospects of m 6A in cellular senescence and age-associated diseases with the aim of providing rational strategies for the treatment of these age-associated diseases.

SIRT6 is an epigenetic repressor of thoracic aortic aneurysms via inhibiting inflammation and senescence

Thoracic aortic aneurysms (TAAs) develop asymptomatically and are characterized by dilatation of the aorta. This is considered a life-threating vascular disease due to the risk of aortic rupture and without effective treatments. The current understanding of the pathogenesis of TAA is still limited, especially for sporadic TAAs without known genetic mutation. Sirtuin 6 (SIRT6) expression was significantly decreased in the tunica media of sporadic human TAA tissues. Genetic knockout of Sirt6 in mouse vascular smooth muscle cells accelerated TAA formation and rupture, reduced survival, and increased vascular inflammation and senescence after angiotensin II infusion. Transcriptome analysis identified interleukin (IL)-1β as a pivotal target of SIRT6, and increased IL-1β levels correlated with vascular inflammation and senescence in human and mouse TAA samples. Chromatin immunoprecipitation revealed that SIRT6 bound to the Il1b promoter to repress expression partly by reducing the H3K9 and H3K56 acetylation. Genetic knockout of Il1b or pharmacological inhibition of IL-1β signaling with the receptor antagonist anakinra rescued Sirt6 deficiency mediated aggravation of vascular inflammation, senescence, TAA formation and survival in mice. The findings reveal that SIRT6 protects against TAA by epigenetically inhibiting vascular inflammation and senescence, providing insight into potential epigenetic strategies for TAA treatment.

Sirtuin 2 deficiency aggravates ageing-induced vascular remodelling in humans and mice

AIMS

The mechanisms underlying ageing-induced vascular remodelling remain unclear. This study investigates the role and underlying mechanisms of the cytoplasmic deacetylase sirtuin 2 (SIRT2) in ageing-induced vascular remodelling.

METHODS AND RESULTS

Transcriptome and quantitative real-time PCR data were used to analyse sirtuin expression. Young and old wild-type and Sirt2 knockout mice were used to explore vascular function and pathological remodelling. RNA-seq, histochemical staining, and biochemical assays were used to evaluate the effects of Sirt2 knockout on the vascular transcriptome and pathological remodelling and explore the underlying biochemical mechanisms. Among the sirtuins, SIRT2 had the highest levels in human and mouse aortas. Sirtuin 2 activity was reduced in aged aortas, and loss of SIRT2 accelerated vascular ageing. In old mice, SIRT2 deficiency aggravated ageing-induced arterial stiffness and constriction-relaxation dysfunction, accompanied by aortic remodelling (thickened vascular medial layers, breakage of elastin fibres, collagen deposition, and inflammation). Transcriptome and biochemical analyses revealed that the ageing-controlling protein p66Shc and metabolism of mitochondrial reactive oxygen species (mROS) contributed to SIRT2 function in vascular ageing. Sirtuin 2 repressed p66Shc activation and mROS production by deacetylating p66Shc at lysine 81. Elimination of reactive oxygen species by MnTBAP repressed the SIRT2 deficiency-mediated aggravation of vascular remodelling and dysfunction in angiotensin II-challenged and aged mice. The SIRT2 coexpression module in aortas was reduced with ageing across species and was a significant predictor of age-related aortic diseases in humans.

CONCLUSION

The deacetylase SIRT2 is a response to ageing that delays vascular ageing, and the cytoplasm-mitochondria axis (SIRT2-p66Shc-mROS) is important for vascular ageing. Therefore, SIRT2 may serve as a potential therapeutic target for vascular rejuvenation.

Metabolic landscape in cardiac aging: insights into molecular biology and therapeutic implications

Cardiac aging is evident by a reduction in function which subsequently contributes to heart failure. The metabolic microenvironment has been identified as a hallmark of malignancy, but recent studies have shed light on its role in cardiovascular diseases (CVDs). Various metabolic pathways in cardiomyocytes and noncardiomyocytes determine cellular senescence in the aging heart. Metabolic alteration is a common process throughout cardiac degeneration. Importantly, the involvement of cellular senescence in cardiac injuries, including heart failure and myocardial ischemia and infarction, has been reported. However, metabolic complexity among human aging hearts hinders the development of strategies that targets metabolic susceptibility. Advances over the past decade have linked cellular senescence and function with their metabolic reprogramming pathway in cardiac aging, including autophagy, oxidative stress, epigenetic modifications, chronic inflammation, and myocyte systolic phenotype regulation. In addition, metabolic status is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and chronic inflammation. However, further elucidation of the metabolism involvement in cardiac degeneration is still needed. Thus, deciphering the mechanisms underlying how metabolic reprogramming impacts cardiac aging is thought to contribute to the novel interventions to protect or even restore cardiac function in aging hearts. Here, we summarize emerging concepts about metabolic landscapes of cardiac aging, with specific focuses on why metabolic profile alters during cardiac degeneration and how we could utilize the current knowledge to improve the management of cardiac aging.

Acylations in cardiovascular biology and diseases, what's beyond acetylation

Metabolism regulates cardiovascular biology through multiple mechanisms, including epigenetic modifications. Over the past two decades, experimental and preclinical studies have highlighted the critical roles of histone modifications in cardiovascular development, homeostasis, and diseases. The widely studied histone acetylation is critical in cardiovascular biology and diseases, and inhibitors of histone deacetylases show therapeutic values. In addition to lysine acetylation, a series of novel non-acetyl lysine acylations have recently been recognized. These non-acetyl lysine acylations have been demonstrated to have physiological and pathological functions, and recent studies have analyzed the roles of these non-acetyl lysine acylations in cardiovascular biology. Herein, we review the current advances in the understanding of non-acetyl lysine acylations in cardiovascular biology and discuss open questions and translational perspectives. These new pieces of evidence provide a more extensive insight into the epigenetic mechanisms underlying cardiovascular biology and help assess the feasibility of targeting acylations to treat cardiovascular diseases.

Downregulation of Sirt6 by CD38 promotes cell senescence and aging

Decreased nicotinamide adenine dinucleotide (NAD+) levels accompany aging. CD38 is the main cellular NADase. Cyanidin-3-O-glucoside (C3G), a natural inhibitor of CD38, is a well-known drug that extends the human lifespan. We investigated mechanisms of CD38 in cell senescence and C3G in antiaging. Myocardial H9c2 cells were induced to senescence with D-gal. CD38 siRNA, C3G and UBCS039 (a chemical activator of Sirt6) inhibited D-gal-induced senescence by reducing reactive oxygen species, hexokinase 2 and SA-β-galactosidase levels. These activators also stimulated cell proliferation and telomerase reverse transcriptase levels, while OSS-128167 (a chemical inhibitor of Sirt6) and Sirt6 siRNA exacerbated the senescent process. H9c2 cells that underwent D-gal-induced cell senescence increased CD38 expression and decreased Sirt6 expression; CD38 siRNA and C3G decreased CD38 expression and increased Sirt6 expression, respectively; and Sirt6 siRNA stimulated cell senescence in the presence of C3G and CD38 siRNA. In D-gal-induced acute aging mice, CD38 and Sirt6 exhibited increased and decreased expression, respectively, in myocardial tissues, and C3G treatment decreased CD38 expression and increased Sirt6 expression in the tissues. C3G also reduced IL-1β, IL-6, IL-17A, TNF-α levels and restored NAD+ and NK cell levels in the animals. We suggest that CD38 downregulates Sirt6 expression to promote cell senescence and C3G exerts an antiaging effect through CD38-Sirt6 signaling.