SIRT3 inhibits cardiac hypertrophy by regulating PARP-1 activity

4'-O-methylbavachalcone alleviates ischemic stroke injury by inhibiting parthanatos and promoting SIRT3

Cerebral ischemia-reperfusion injury (CIRI) can induce massive death of ischemic penumbra neurons via oxygen burst, exacerbating brain damage. Parthanatos is a form of caspase-independent cell death involving excessive activation of PARP-1, closely associated with intense oxidative stress following CIRI. 4'-O-methylbavachalcone (MeBavaC), an isoprenylated chalcone component in Fructus Psoraleae, has potential neuroprotective effects. This study primarily investigates whether MeBavaC can act on SIRT3 to alleviate parthanatos of ischemic penumbra neurons induced by CIRI. MeBavaC was oral gavaged to the middle cerebral artery occlusion-reperfusion (MCAO/R) rats after occlusion. The effects of MeBavaC on cerebral injury were detected by the neurological deficit score and cerebral infarct volume. In vitro, PC-12 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R), and assessed cell viability and cell injury. Also, the levels of ROS, mitochondrial membrane potential (MMP), and intracellular Ca2+ levels were detected to reflect mitochondrial function. We conducted western blotting analyses of proteins involved in parthanatos and related signaling pathways. Finally, the exact mechanism between the neuroprotection of MeBavaC and parthanatos was explored. Our results indicate that MeBavaC reduces the cerebral infarct volume and neurological deficit scores in MCAO/R rats, and inhibits the decreased viability of PC-12 cells induced by OGD/R. MeBavaC also downregulates the expression of parthanatos-related death proteins PARP-1, PAR, and AIF. However, this inhibitory effect is weakened after the use of a SIRT3 inhibitor. In conclusion, the protective effect of MeBavaC against CIRI may be achieved by inhibiting parthanatos of ischemic penumbra neurons through the SIRT3-PARP-1 axis.

Macrod1 suppresses diabetic cardiomyopathy via regulating PARP1-NAD+-SIRT3 pathway

Diabetic cardiomyopathy (DCM), one of the most serious long-term consequences of diabetes, is closely associated with oxidative stress, inflammation and apoptosis in the heart. MACRO domain containing 1 (Macrod1) is an ADP-ribosylhydrolase 1 that is highly enriched in mitochondria, participating in the pathogenesis of cardiovascular diseases. In this study, we investigated the role of Macrod1 in DCM. A mice model was established by feeding a high-fat diet (HFD) and intraperitoneal injection of streptozotocin (STZ). We showed that Macrod1 expression levels were significantly downregulated in cardiac tissue of DCM mice. Reduced expression of Macrod1 was also observed in neonatal rat cardiomyocytes (NRCMs) treated with palmitic acid (PA, 400 μM) in vitro. Knockout of Macrod1 in DCM mice not only worsened glycemic control, but also aggravated cardiac remodeling, mitochondrial dysfunction, NAD+ consumption and oxidative stress, whereas cardiac-specific overexpression of Macrod1 partially reversed these pathological processes. In PA-treated NRCMs, overexpression of Macrod1 significantly inhibited PARP1 expression and restored NAD+ levels, activating SIRT3 to resist oxidative stress. Supplementation with the NAD+ precursor Niacin (50 μM) alleviated oxidative stress in PA-stimulated cardiomyocytes. We revealed that Macrod1 reduced NAD+ consumption by inhibiting PARP1 expression, thereby activating SIRT3 and anti-oxidative stress signaling. This study identifies Macrod1 as a novel target for DCM treatment. Targeting the PARP1-NAD+-SIRT3 axis may open a novel avenue to development of new intervention strategies in DCM. Schematic illustration of macrod1 ameliorating diabetic cardiomyopathy oxidative stress via PARP1-NAD+-SIRT3 axis.

SIRT3 regulates mitochondrial function: A promising star target for cardiovascular disease therapy

Dysregulation of mitochondrial homeostasis is common to all types of cardiovascular diseases. SIRT3 regulates apoptosis and autophagy, material and energy metabolism, mitochondrial oxidative stress, inflammation, and fibrosis. As an important mediator and node in the network of mechanisms, SIRT3 is essential to many activities. This review explains how SIRT3 regulates mitochondrial homeostasis and the tricarboxylic acid cycle to treat common cardiovascular diseases. A novel description of the impact of lifestyle factors on SIRT3 expression from the angles of nutrition, exercise, and temperature is provided.

NAD+: A key metabolic regulator with great therapeutic potential for myocardial infarction via Sirtuins family

Myocardial infarction (MI) is one of the complex phenotypes of coronary artery disease, which results from the interaction of multiple genetic and environmental factors. Nicotinamide Adenine Dinucleotide (NAD+) is an important cofactor regulating metabolic homeostasis and a rate-limiting substrate for sirtuin (SIRT) deacetylase. Numerous NAD+ studies have shown that it can be used as an anti-MI treatment. However, there have been few systematic reviews of the overall role of NAD+ in treating MI. MI, which has long been a global health problem, still lacks effective treatment till now, and the discovery of NAD+ provides a new perspective on its adjuvant treatment. This review summarizes the role of NAD+ signaling in SIRTs in alleviating MI.

The Complex Network of ADP-Ribosylation and DNA Repair: Emerging Insights and Implications for Cancer Therapy

ADP-ribosylation is a post-translational modification of proteins that plays a key role in various cellular processes, including DNA repair. Recently, significant progress has been made in understanding the mechanism and function of ADP-ribosylation in DNA repair. ADP-ribosylation can regulate the recruitment and activity of DNA repair proteins by facilitating protein-protein interactions and regulating protein conformations. Moreover, ADP-ribosylation can influence additional post-translational modifications (PTMs) of proteins involved in DNA repair, such as ubiquitination, methylation, acetylation, phosphorylation, and SUMOylation. The interaction between ADP-ribosylation and these additional PTMs can fine-tune the activity of DNA repair proteins and ensure the proper execution of the DNA repair process. In addition, PARP inhibitors have been developed as a promising cancer therapeutic strategy by exploiting the dependence of certain cancer types on the PARP-mediated DNA repair pathway. In this paper, we review the progress of ADP-ribosylation in DNA repair, discuss the crosstalk of ADP-ribosylation with additional PTMs in DNA repair, and summarize the progress of PARP inhibitors in cancer therapy.

Baicalin inhibits pressure overload-induced cardiac hypertrophy by regulating the SIRT3-dependent signaling pathway

BACKGROUND

The conserved sirtuin protein sirtuin 3 (SIRT3) is a vital protective protein for cardiac hypertrophy. Inhibition of SIRT3 accelerated the development of heart hypertrophy. On the other hand, myocardial hypertrophy was prevented by overexpressing SIRT3. SIRT3 has been proposed as a potential therapeutic target for managing or averting heart hypertrophy. Baicalin, a flavonoid extracted from the Scutellaria baicalensis plant, has anti-cardiovascular properties, including protection against cardiac hypertrophy. However, the molecular mechanism of the anti-hypertrophic effect of baicalin is not well known.

PURPOSE

In this study, we aim to investigate the effect of baicalin on cardiac hypertrophy and explored its underlying molecular mechanisms.

STUDY-DESIGN/METHODS

Abdominal aortic constriction (AAC)-induced mouse cardiac hypertrophy and angiotensin II (Ang II)-induced cardiomyocyte hypertrophy models were established. After baicalin treatment, cardiac hypertrophy was monitored by detecting the expression of hypertrophic genes and cell surface area. Echocardiogram was performed to check the heart function in vivo. Moreover, the protein expression of the SIRT3-dependent pathway was detected by Western blotting.

RESULTS

In this work, we demonstrated that baicalin might suppress the cell surface area and the expression of the Ang II -induced myosin heavy chain β (β-MHC), brain natriuretic polypeptide (BNP), and atrial natriuretic factor (ANF). Additionally, it reduced the AAC rats' hypertrophic impact. We also found that baicalin prevents cardiac hypertrophy by regulating SIRT3/LKB1/AMPK signaling pathway. Moreover, we showed that baicalin upregulated the SIRT3 protein expression by inhibiting proteasome and by the activation of 20 S proteasome subunit beta type-5 (PSMB5).

CONCLUSION

These results offer the first proof that baicalin inhibits cardiac hypertrophy due to its effect on the SIRT3-dependent signaling pathway, indicating its potential for treating cardiac hypertrophy and heart failure. The present study provides a preliminary experimental basis for the clinical application of baicalin and baicalin-like compounds.

Impact of polyphenols on heart failure and cardiac hypertrophy: clinical effects and molecular mechanisms

Polyphenols are abundant in regular diets and possess antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and cardioprotective effects. Regarding the inadequacy of the current treatments in preventing cardiac remodeling following cardiovascular diseases, attention has been focused on improving cardiac function with potential alternatives such as polyphenols. The following online databases were searched for relevant orginial published from 2000 to 2023: EMBASE, MEDLINE, and Web of Science databases. The search strategy aimed to assess the effects of polyphenols on heart failure and keywords were "heart failure" and "polyphenols" and "cardiac hypertrophy" and "molecular mechanisms". Our results indicated polyphenols are repeatedly indicated to regulate various heart failure-related vital molecules and signaling pathways, such as inactivating fibrotic and hypertrophic factors, preventing mitochondrial dysfunction and free radical production, the underlying causes of apoptosis, and also improving lipid profile and cellular metabolism. In the current study, we aimed to review the most recent literature and investigations on the underlying mechanism of actions of different polyphenols subclasses in cardiac hypertrophy and heart failure to provide deep insight into novel mechanistic treatments and direct future studies in this context. Moreover, due to polyphenols' low bioavailability from conventional oral and intravenous administration routes, in this study, we have also investigated the currently accessible nano-drug delivery methods to optimize the treatment outcomes by providing sufficient drug delivery, targeted therapy, and less off-target effects, as desired by precision medicine standards.

Cardioprotective effect of ultrasound-targeted destruction of Sirt3-loaded cationic microbubbles in a large animal model of pathological cardiac hypertrophy

Pathological cardiac hypertrophy occurs in response to numerous increased afterload stimuli and precedes irreversible heart failure (HF). Therefore, therapies that ameliorate pathological cardiac hypertrophy are urgently required. Sirtuin 3 (Sirt3) is a main member of histone deacetylase class III and is a crucial anti-oxidative stress agent. Therapeutically enhancing the Sirt3 transfection efficiency in the heart would broaden the potential clinical application of Sirt3. Ultrasound-targeted microbubble destruction (UTMD) is a prospective, noninvasive, repeatable, and targeted gene delivery technique. In the present study, we explored the potential and safety of UTMD as a delivery tool for Sirt3 in hypertrophic heart tissues using adult male Bama miniature pigs. Pigs were subjected to ear vein delivery of human Sirt3 together with UTMD of cationic microbubbles (CMBs). Fluorescence imaging, western blotting, and quantitative real-time PCR revealed that the targeted destruction of ultrasonic CMBs in cardiac tissues greatly boosted Sirt3 delivery. Overexpression of Sirt3 ameliorated oxidative stress and partially improved the diastolic function and prevented the apoptosis and profibrotic response. Lastly, our data revealed that Sirt3 may regulate the potential transcription of catalase and MnSOD through Foxo3a. Combining the advantages of ultrasound CMBs with preclinical hypertrophy large animal models for gene delivery, we established a classical hypertrophy model as well as a strategy for the targeted delivery of genes to hypertrophic heart tissues. Since oxidative stress, fibrosis and apoptosis are indispensable in the evolution of cardiac hypertrophy and heart failure, our findings suggest that Sirt3 is a promising therapeutic option for these diseases. STATEMENT OF SIGNIFICANCE: : Pathological cardiac hypertrophy is a central prepathology of heart failure and is seen to eventually precede it. Feasible targets that may prevent or reverse disease progression are scarce and urgently needed. In this study, we developed surface-filled lipid octafluoropropane gas core cationic microbubbles that could target the release of human Sirt3 reactivating the endogenous Sirt3 in hypertrophic hearts and protect against oxidative stress in a pig model of cardiac hypertrophy induced by aortic banding. Sirt3-CMBs may enhance cardiac diastolic function and ameliorate fibrosis and apoptosis. Our work provides a classical cationic lipid-based, UTMD-mediated Sirt3 delivery system for the treatment of Sirt3 in patients with established cardiac hypertrophy, as well as a promising therapeutic target to combat pathological cardiac hypertrophy.

SIRT3 improved peroxisomes-mitochondria interplay and prevented cardiac hypertrophy via preserving PEX5 expression

The present study identified a novel mechanism underlying the protective effect of Sirtuin 3 (SIRT3) against pathological cardiac hypertrophy, beyond its well-accepted role as a deacetylase in mitochondria. SIRT3 modulates the peroxisomes-mitochondria interplay by preserving the expression of peroxisomal biogenesis factor 5 (PEX5), thereby improving mitochondrial function. Downregulation of PEX5 was observed in the hearts of Sirt3^-/- mice and angiotensin II-induced cardiac hypertrophic mice, as well as in cardiomyocytes with SIRT3 silencing. PEX5 knockdown abolished the protective effect of SIRT3 against cardiomyocyte hypertrophy, whereas PEX5 overexpression alleviated the hypertrophic response induced by SIRT3 inhibition. PEX5 was involved in the regulation of SIRT3 in mitochondrial homeostasis, including mitochondrial membrane potential, mitochondrial dynamic balance, mitochondrial morphology and ultrastructure, as well as ATP production. In addition, SIRT3 alleviated peroxisomal abnormalities in hypertrophic cardiomyocytes via PEX5, as implied by improvement of peroxisomal biogenesis and ultrastructure, as well as increase of peroxisomal catalase and repression of oxidative stress. Finally, the role of PEX5 as a key regulator of the peroxisomes-mitochondria interplay was confirmed, since peroxisomal defects caused by PEX5 deficiency led to mitochondrial impairment. Taken together, these observations indicate that SIRT3 could maintain mitochondrial homeostasis by preserving the peroxisomes-mitochondria interplay via PEX5. Our findings provide a new understanding of the role of SIRT3 in mitochondrial regulation via interorganelle communication in cardiomyocytes.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Fueling genome maintenance: On the versatile roles of NAD+ in preserving DNA integrity

NAD⁺ is a versatile biomolecule acting as a master regulator and substrate in various cellular processes, including redox regulation, metabolism, and various signaling pathways. In this article, we concisely and critically review the role of NAD⁺ in mechanisms promoting genome maintenance. Numerous NAD⁺-dependent reactions are involved in the preservation of genome stability, the cellular DNA damage response, and other pathways regulating nucleic acid metabolism, such as gene expression and cell proliferation pathways. Of note, NAD⁺ serves as a substrate to ADP-ribosyltransferases, sirtuins, and potentially also eukaryotic DNA ligases, all of which regulate various aspects of DNA integrity, damage repair, and gene expression. Finally, we critically analyze recent developments in the field as well as discuss challenges associated with therapeutic actions intended to raise NAD⁺ levels.

Sirt3 ameliorates mitochondrial dysfunction and oxidative stress through regulating mitochondrial biogenesis and dynamics in cardiomyoblast

Sirtuins are the endogenously present anti-aging protein deacetylases that regulate the mitochondrial biogenesis and function. Especially Sirt3, a mitochondrial sirtuin, is well known for maintaining mitochondrial function and health. In the present study, we have explored the novel role of Sirt3 in mitochondrial biogenesis and shown the role of Sirt3 in mito-nuclear communication through AMPK-α in Sirt3 knockdown and Sirt3 overexpressed H9c2 cells. The study found that impaired mitochondrial function in Sirt3-knockdown H9c2 cells was associated with decreased expression of mitochondrial DNA encoded genes, reduced SOD2 expression and activity. The study also revealed that Sirt3 knockdown affects mitochondrial biogenesis and dynamics. To further confirm the role of Sirt3 on mitochondrial biogenesis and health, we did Sirt3 overexpression in H9c2 cells. Sirt3 overexpression enhanced the expression of mitochondrial DNA encoded genes, increased SOD2 activity and altered mitochondrial dynamics. Sirt3 overexpression also caused an increase in mitochondrial biogenesis gene and protein (PGC-1α and TFAM) expression. All these changes were confirmed with mitochondrial functional parameters like basal respiration, maximal respiratory capacity, spare respiratory capacity and ATP production. We found decreased mitochondrial function in Sirt3-knockdown H9c2 cells when compared to control H9c2 cells. Together our data conclude that Sirt3 regulates cardiac mitochondrial health and function through the Sirt3-AMPKα-PGC-1α axis.

Mitochondria in Pathological Cardiac Hypertrophy Research and Therapy

Cardiac hypertrophy, a stereotypic cardiac response to increased workload, ultimately progresses to severe contractile dysfunction and uncompensated heart failure without appropriate intervention. Sustained cardiac overload inevitably results in high energy consumption, thus breaking the balance between mitochondrial energy supply and cardiac energy demand. In recent years, accumulating evidence has indicated that mitochondrial dysfunction is implicated in pathological cardiac hypertrophy. The significant alterations in mitochondrial energetics and mitochondrial proteome composition, as well as the altered expression of transcripts that have an impact on mitochondrial structure and function, may contribute to the initiation and progression of cardiac hypertrophy. This article presents a summary review of the morphological and functional changes of mitochondria during the hypertrophic response, followed by an overview of the latest research progress on the significant modulatory roles of mitochondria in cardiac hypertrophy. Our article is also to summarize the strategies of mitochondria-targeting as therapeutic targets to treat cardiac hypertrophy.

OUP accepted manuscript

Cardiovascular diseases (CVDs) arise from a complex interplay among genomic, proteomic, and metabolomic abnormalities. Emerging evidence has recently consolidated the presence of robust DNA damage in a variety of cardiovascular disorders. DNA damage triggers a series of cellular responses termed DNA damage response (DDR) including detection of DNA lesions, cell cycle arrest, DNA repair, cellular senescence, and apoptosis, in all organ systems including hearts and vasculature. Although transient DDR in response to temporary DNA damage can be beneficial for cardiovascular function, persistent activation of DDR promotes the onset and development of CVDs. Moreover, therapeutic interventions that target DNA damage and DDR have the potential to attenuate cardiovascular dysfunction and improve disease outcome. In this review, we will discuss molecular mechanisms of DNA damage and repair in the onset and development of CVDs, and explore how DDR in specific cardiac cell types contributes to CVDs. Moreover, we will highlight the latest advances regarding the potential therapeutic strategies targeting DNA damage signalling in CVDs.

Post-translational modifications by SIRT3 de-2-hydroxyisobutyrylase activity regulate glycolysis and enable nephrogenesis

Abnormal kidney development leads to lower nephron number, predisposing to renal diseases in adulthood. In embryonic kidneys, nephron endowment is dictated by the availability of nephron progenitors, whose self-renewal and differentiation require a relatively repressed chromatin state. More recently, NAD⁺-dependent deacetylase sirtuins (SIRTs) have emerged as possible regulators that link epigenetic processes to the metabolism. Here, we discovered a novel role for the NAD⁺-dependent deacylase SIRT3 in kidney development. In the embryonic kidney, SIRT3 was highly expressed only as a short isoform, with nuclear and extra-nuclear localisation. The nuclear SIRT3 did not act as deacetylase but exerted de-2-hydroxyisobutyrylase activity on lysine residues of histone proteins. Extra-nuclear SIRT3 regulated lysine 2-hydroxyisobutyrylation (Khib) levels of phosphofructokinase (PFK) and Sirt3 deficiency increased PFK Khib levels, inducing a glycolysis boost. This altered Khib landscape in Sirt3^−/− metanephroi was associated with decreased nephron progenitors, impaired nephrogenesis and a reduced number of nephrons. These data describe an unprecedented role of SIRT3 in controlling early renal development through the regulation of epigenetics and metabolic processes.

Quercetin Attenuates Cardiac Hypertrophy by Inhibiting Mitochondrial Dysfunction Through SIRT3/PARP-1 Pathway

Cardiac hypertrophy is an important characteristic in the development of hypertensive heart disease. Mitochondrial dysfunction plays an important role in the pathology of cardiac hypertrophy. Recent studies have shown that sirtuin 3 (SIRT3)/poly (ADP-ribose) polymerase-1 (PARP-1) pathway modulation inhibits cardiac hypertrophy. Quercetin, a natural flavonol agent, has been reported to attenuate cardiac hypertrophy. However, the molecular mechanism is not completely elucidated. In this study, we aimed to explore the mechanism underlying the protective effect of quercetin on cardiac hypertrophy. Spontaneously hypertensive rats (SHRs) were treated with quercetin (20 mg/kg/d) for 8 weeks to evaluate the effects of quercetin on blood pressure and cardiac hypertrophy. Additionally, the mitochondrial protective effect of quercetin was assessed in H9c2 cells treated with Ang II. SHRs displayed aggravated cardiac hypertrophy and fibrosis, which were attenuated by quercetin treatment. Quercetin also improved cardiac function, reduced mitochondrial superoxide and protected mitochondrial structure in vivo. In vitro, Ang II increased the mRNA level of hypertrophic markers including atrial natriuretic factor (ANF) and β-myosin heavy chain (β-MHC), whereas quercetin ameliorated this hypertrophic response. Moreover, quercetin prevented mitochondrial function against Ang II induction. Importantly, mitochondrial protection and PARP-1 inhibition by quercetin were partly abolished after SIRT3 knockdown. Our results suggested that quercetin protected mitochondrial function by modulating SIRT3/PARP-1 pathway, contributing to the inhibition of cardiac hypertrophy.

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.

SIRT3 as a potential therapeutic target for heart failure

Heart failure causes significant morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with heart failure are exceptionally complex. Despite recent advances in heart failure research, treatment outcomes remain poor. The sirtuin family member sirtuin-3 (SIRT3) is involved in several key biological processes, including ATP production, catabolism, and reactive oxygen species detoxification. In addition to its role in metabolism, SIRT3 regulates cell death and survival and has been implicated in the pathogenesis of cardiovascular diseases. Emerging evidence also shows that SIRT3 can protect cardiomyocytes from hypertrophy, ischemia-reperfusion injury, cardiac fibrosis, and impaired angiogenesis. In this review article, we summarize the recent advances in SIRT3 research and discuss the role of SIRT3 in heart failure. We also discuss the potential use of SIRT3 as a therapeutic target in heart failure.

Pancreatic Sirtuin 3 Deficiency Promotes Hepatic Steatosis by Enhancing 5-Hydroxytryptamine Synthesis in Mice With Diet-Induced Obesity

Sirtuin 3 (SIRT3) is a protein deacetylase regulating β-cell function through inhibiting oxidative stress in obese and diabetic mice, but the detailed mechanism and potential effect of β-cell-specific SIRT3 on metabolic homeostasis, and its potential effect on other metabolic organs, are unknown. We found that glucose tolerance and glucose-stimulated insulin secretion were impaired in high-fat diet (HFD)-fed β-cell-selective Sirt3 knockout (Sirt3 f/f;Cre/+) mice. In addition, Sirt3 f/f;Cre/+ mice had more severe hepatic steatosis than Sirt3 f/f mice upon HFD feeding. RNA sequencing of islets suggested that Sirt3 deficiency overactivated 5-hydroxytryptamine (5-HT) synthesis as evidenced by upregulation of tryptophan hydroxylase 1 (TPH1). 5-HT concentration was increased in both islets and serum of Sirt3 f/f;Cre/+ mice. 5-HT also facilitated the effect of palmitate to increase lipid deposition. Treatment with TPH1 inhibitor ameliorated hepatic steatosis and reduced weight gain in HFD-fed Sirt3 f/f;Cre/+ mice. These data suggested that under HFD feeding, SIRT3 deficiency in β-cells not only regulates insulin secretion but also modulates hepatic lipid metabolism via the release of 5-HT.

Natural products: The role and mechanism in low-density lipoprotein oxidation and atherosclerosis

Atherosclerosis is a chronic inflammatory, metabolic, and epigenetic disease, which leads to the life-threatening coronary artery disease. Emerging studies from bench to bedside have demonstrated the pivotal role of low-density lipoprotein (LDL) oxidation in the initiation and progression of atherosclerosis. This article hereby reviews oxidation mechanism of LDL, and the pro-atherogenic and biomarker role of oxidized LDL in atherosclerosis. We also review the pharmacological effects of several representative natural products (vitamin E, resveratrol, quercetin, probucol, tanshinone IIA, epigallocatechin gallate, and Lycopene) in protecting against LDL oxidation and atherosclerosis. Clinical and basic research supports the beneficial effects of these natural products in inhibiting LDL oxidation and preventing atherosclerosis, but the data are still controversial. This may be related to factors such as the population and the dosage and time of taking natural products involved in different studies. Understanding the mechanism of LDL oxidation and effect of oxidized LDL help researchers to find novel therapies against atherosclerosis.

Role of PARP-1 in mitochondrial homeostasis

BACKGROUND

Nuclear poly(ADP-ribose) polymerase-1 (PARP-1) is a well characterised protein that accounts for the majority of PARylation reactions using NAD⁺ as a substrate, regulating diverse cellular functions. In addition to its nuclear functions, several recent studies have identified localization of PARP-1 in mitochondria and emphasized its possible role in maintaining mitochondrial homeostasis. Various reports suggest that nuclear PARP-1 has been implicated in diverse mitochondria-specific communication processes.

SCOPE OF REVIEW

The present review emphasizes on the potential role of PARP-1 in mitochondrial processes such as bioenergetics, mtDNA maintenance, cell death and mitophagy.

MAJOR CONCLUSIONS

The origin of mitochondrial PARP-1 is still an enigma; however researchers are trying to establish the cross-talk between nuclear and mitochondrial PARP-1 and how these PARP-1 pools modulate mitochondrial activity.

GENERAL SIGNIFICANCE

A better understanding of the possible role of PARP-1 in mitochondrial homeostasis helps us to explore the potential therapeutic targets to protect mitochondrial dysfunctions.