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Sirtuin 3 (SIRT3) is well known as a conserved nicotinamide adenine dinucleotide + (NAD + )-dependent deacetylase located in the mitochondria that may regulate oxidative stress, catabolism and ATP production. Accumulating evidence has recently revealed that SIRT3 plays its critical roles in cardiac fibrosis, myocardial fibrosis and even heart failure (HF), through its deacetylation modifications. Accordingly, discovery of SIRT3 activators and elucidating their underlying mechanisms of HF should be urgently needed. Herein, we identified a new small-molecule activator of SIRT3 (named 2-APQC) by the structure-based drug designing strategy. 2-APQC was shown to alleviate isoproterenol (ISO)-induced cardiac hypertrophy and myocardial fibrosis in vitro and in vivo rat models. Importantly, in SIRT3 knockout mice, 2-APQC could not relieve HF, suggesting that 2-APQC is dependent on SIRT3 for its protective role. Mechanically, 2-APQC was found to inhibit the mammalian target of rapamycin (mTOR)-p70 ribosomal protein S6 kinase (p70S6K), c-jun N-terminal kinase (JNK) and transforming growth factor-β (TGF-β)/ small mother against decapentaplegic 3 (Smad3) pathways to improve ISO-induced cardiac hypertrophy and myocardial fibrosis. Based upon RNA-seq analyses, we demonstrated that SIRT3-pyrroline-5-carboxylate reductase 1 (PYCR1) axis was closely assoiated with HF. By activating PYCR1, 2-APQC was shown to enhance mitochondrial proline metabolism, inhibited reactive oxygen species (ROS)-p38 mitogen activated protein kinase (p38MAPK) pathway and thereby protecting against ISO-induced mitochondrialoxidative damage. Moreover, activation of SIRT3 by 2-APQC could facilitate AMP-activated protein kinase (AMPK)-Parkin axis to inhibit ISO-induced necrosis. Together, our results demonstrate that 2-APQC is a targeted SIRT3 activator that alleviates myocardial hypertrophy and fibrosis by regulating mitochondrial homeostasis, which may provide a new clue on exploiting a promising drug candidate for the future HF therapeutics., (© 2024. The Author(s).)

Background: Bawei Chenxiang Wan (BCW) is among the most effective and widely used therapies for coronary heart disease and angina pectoris in Tibet. However, whether it confers protection through a right-ventricle (RV) myocardial metabolic mechanism is unknown., Methods: Male Sprague-Dawley rats were orally administrated with BCW, which was injected concurrently with a bolus of Sugen5416, and subjected to hypoxia exposure (SuHx; 5000 m altitude) for 4 weeks. Right ventricular hypertrophy (RVH) in high-altitude heart disease (HAHD) was assessed using Fulton's index (FI; ratio of RV to left ventricle + septum weights) and heart-weight-to-body-weight ratio (HW/BW). The effect of therapeutic administration of BCW on the RVH hemodynamics was assessed through catheterization (mean right ventricular pressure and mean pulmonary artery pressure (mRVP and mPAP, respectively)). Tissue samples were used to perform histological staining, and confirmatory analyses of mRNA and protein levels were conducted to detect alterations in the mechanisms of RVH in HAHD. The protective mechanism of BCW was further verified via cell culture., Results: BCW considerably reduced SuHx-associated RVH, as indicated by macro morphology, HW/BW ratio, FI, mPAP, mRVP, hypertrophy markers, heart function, pathological structure, and myocardial enzymes. Moreover, BCW can alleviate the disorder of glucose and fatty acid metabolism through upregulation of carnitine palmitoyltransferase1ɑ, citrate synthase, and acetyl-CoA and downregulation of glucose transport-4, phosphofructokinase, and pyruvate, which resulted in the reduced levels of free fatty acid and lactic acid and increased aerobic oxidation. This process may be mediated via the regulation of sirtuin 3 (SIRT3)-hypoxia-inducible factor 1α (HIF1α)-pyruvate dehydrogenase kinase (PDK)/pyruvate dehydrogenase (PDH) signaling pathway. Subsequently, the inhibition of SIRT3 expression by 3-TYP (a selective inhibitor of SIRT3) can reverse substantially the anti-RVH effect of BCW in HAHD, as indicated by hypertrophy marker and serum myocardial enzyme levels., Conclusions: BCW prevented SuHx-induced RVH in HAHD via the SIRT3-HIF1ɑ-PDK/PDH signaling pathway to alleviate the disturbance in fatty acid and glucose metabolism. Therefore, BCW can be used as an alternative drug for the treatment of RVH in HAHD., (© 2024. The Author(s).)

Granulosa cells are somatic cells located inside follicles that play a crucial role in the growth and development of follicles. Quercetin and tanshinone are two key monomers in traditional Chinese medicine that have antioxidant and anti-aging properties. The KGN cell apoptosis model caused by triptolide (TP) was employed in this work to investigate granulosa cell death and medication rescue. Quercetin and tanshinone therapy suppressed KGN cell death and oxidation while also regulating the expression of critical apoptosis and oxidation-related markers such as B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax). Further research revealed that the effects of Quercetin and Tanshinone were accomplished via deacetylation of FOXO3A in the cytoplasm and mitochondria via the SIRT1/SIRT3-FOXO3a axis. In summary, Quercetin and tanshinone protect KGN cells from apoptosis by reducing mitochondrial apoptosis and oxidation via the SIRT1/SIRT3-FOXO3a axis.

Sirtuins catalyze deacetylation of lysine residues with a NAD + -dependent mechanism. In mammals, the sirtuin family is composed of seven members, divided into four subclasses that differ in substrate specificity, subcellular localization, regulation, as well as interactions with other proteins, both within and outside the epigenetic field. Recently, much interest has been growing in SIRT3, which is mainly involved in regulating mitochondrial metabolism. Moreover, SIRT3 seems to be protective in diseases such as age-related, neurodegenerative, liver, kidney, heart, and metabolic ones, as well as in cancer. In most cases, activating SIRT3 could be a promising strategy to tackle these health problems. Here, we summarize the main biological functions, substrates, and interactors of SIRT3, as well as several molecules reported in the literature that are able to modulate SIRT3 activity. Among the activators, some derive from natural products, others from library screening, and others from the classical medicinal chemistry approach.

Renal interstitial fibrosis is the common pathological process of various chronic kidney diseases to end-stage renal disease. Inhibition of fibroblast activation attenuates renal interstitial fibrosis. Our previous studies show that poricoic acid A (PAA) isolated from Poria cocos is a potent anti-fibrotic agent. In the present study we investigated the effects of PAA on renal fibroblast activation and interstitial fibrosis and the underlying mechanisms. Renal interstitial fibrosis was induced in rats or mice by unilateral ureteral obstruction (UUO). UUO rats were administered PAA (10 mg·kg -1 ·d -1 , i.g.) for 1 or 2 weeks. An in vitro model of renal fibrosis was established in normal renal kidney fibroblasts (NRK-49F cells) treated with TGF-β1. We showed that PAA treatment rescued Sirt3 expression, and significantly attenuated renal fibroblast activation and interstitial fibrosis in both the in vivo and in vitro models. In TGF-β1-treated NRK-49F cells, we demonstrated that Sirt3 deacetylated β-catenin (a key transcription factor of fibroblast activation) and then accelerated its ubiquitin-dependent degradation, thus suppressing the protein expression and promoter activity of pro-fibrotic downstream target genes (twist, snail1, MMP-7 and PAI-1) to alleviate fibroblast activation; the lysine-49 (K49) of β-catenin was responsible for Sirt3-mediated β-catenin deacetylation. In molecular docking analysis, we found the potential interaction of Sirt3 and PAA. In both in vivo and in vitro models, pharmacological activation of Sirt3 by PAA significantly suppressed renal fibroblast activation via facilitating β-catenin K49 deacetylation. In UUO mice and NRK-49F cells, Sirt3 overexpression enhanced the anti-fibrotic effect of PAA, whereas Sirt3 knockdown weakened the effect. Taken together, PAA attenuates renal fibroblast activation and interstitial fibrosis by upregulating Sirt3 and inducing β-catenin K49 deacetylation, highlighting Sirt3 functions as a promising therapeutic target of renal fibroblast activation and interstitial fibrosis., (© 2022. The Author(s).)

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cognitive impairment that currently is uncurable. Previous study shows that trilobatin (TLB), a naturally occurring food additive, exerts neuroprotective effect in experimental models of AD. In the present study we investigated the molecular mechanisms underlying the beneficial effect of TLB on experimental models of AD in vivo and in vitro. APP/PS1 transgenic mice were administered TLB (4, 8 mg· kg -1 ·d -1 , i.g.) for 3 months; rats were subjected to ICV injection of Aβ 25-35 , followed by administration of TLB (2.5, 5, 10 mg· kg -1 ·d -1 , i.g.) for 14 days. We showed that TLB administration significantly and dose-dependently ameliorated the cognitive deficits in the two AD animal models, assessed in open field test, novel object recognition test, Y-maze test and Morris water maze test. Furthermore, TLB administration dose-dependently inhibited microglia and astrocyte activation in the hippocampus of APP/PS1 transgenic mice accompanied by decreased expression of high-mobility group box 1 (HMGB1), TLR4 and NF-κB. In Aβ 25-25 -treated BV2 cells, TLB (12.5-50 μM) concentration-dependently increased the cell viability through inhibiting HMGB1/TLR4/NF-κB signaling pathway. HMGB1 overexpression abrogated the beneficial effects of TLB on BV2 cells after Aβ 25-35 insults. Molecular docking and surface plasmon resonance assay revealed that TLB directly bound to HMGB1 with a K D value of 8.541×10 -4 M. Furthermore, we demonstrated that TLB inhibited Aβ 25-35 -induced acetylation of HMGB1 through activating SIRT3/SOD2 signaling pathway, thereby restoring redox homeostasis and suppressing neuroinflammation. These results, for the first time, unravel a new property of TLB: rescuing cognitive impairment of AD via targeting HMGB1 and activating SIRT3/SOD2 signaling pathway., (© 2022. The Author(s), under exclusive licence to Shanghai Institute of Materia Medica, Chinese Academy of Sciences and Chinese Pharmacological Society.)

The goal of this study was to explore the mechanism of action of DL-3-n-butylphthalidein (NBP) the treatment of vascular dementia (VD) in mice. A vascular dementia mouse model was established with repeated cerebral ischemia/reperfusion (I/R), followed by administration of two different doses of NBP for 28 days. A Morris water maze was used to detect any changes in spatial cognition, while H&E staining was used to observe any histopathological changes in the hippocampus. The number of Caspase-3 and Caspase-9 positive neurons in the hippocampal CA1 region were also assessed using immunohistochemistry. The expression of Nrf2, Sirt3, and autophagy-related factors LC3 II/I and p62 in the hippocampus were detected by Western blotting. The results indicated that NBP treatment ameliorated learning and memory deficits, attenuated pathological damage in the CA1 regions, and reduced autophagy and apoptosis via the Nrf2/SIRT3 pathway after repeated cerebral I/R. Therefore, NBP treatment can improve the learning and cognitive memory of VD mice, possibly through the inhibition of autophagy and apoptosis mediated by the Nrf2/SIRT3 signaling pathway., (Copyright © 2022. Published by Elsevier B.V.)

Purpose: Atherosclerosis, a chronic disease of the arteries, results from pathological processes including the accumulation and aggregation of oxidized low-density lipoprotein (oxLDL) in the vessel walls, development of neointima, formation of a fibrous cap, and migration of immune cells to damaged vascular endothelium. Recent studies have shown that mitochondrial dysfunction is closely associated with the development and progression of atherosclerosis. Idebenone, a short-chain benzoquinone similar in structure to coenzyme Q10, can effectively clear oxygen free radicals as an electron carrier and antioxidant. In the present study, we aim to investigate weather idebenone protects against atherosclerosis in apolipoprotein E-deficient (apoE-/-) mice., Methods: apoE-/- mice receiving a high-fat diet (HFD) were treated with idebenone for 16 weeks. A total of 60 mice were randomized into the following four groups: (1) HFD, (2) HFD and low-dose idebenone (100 mg/kg/d), (3) HFD and medium-dose idebenone (200 mg/kg/d), and (4) HFD and high-dose (400 mg/kg/d). Proteomic analysis was performed between the HFD and idebenone-high-dose group. Plaque analysis was carried out by histological and immunohistochemical staining. Western blot, TUNEL staining, and MitoSOX assays were performed in human umbilical vein endothelial cells (HUVECs) to investigate the SIRT3-SOD2-mtROS pathway., Results: Histological and morphological analysis demonstrated that idebenone significantly reduced plaque burden and plaque size. Idebenone treatment effectively stabilized the atherosclerotic plaques. In mice treated with idebenone, 351 up-regulated and 379 down-regulated proteins were found to be significantly altered in proteomic analysis. In particular, the expression of SIRT3, SOD2, and NLRP3 was significantly regulated in the idebenone treatment groups compared with the HFD group both in vivo and in vitro. We further confirmed that idebenone protected against endothelial cell damage and inhibited the production of mitochondrial reactive oxygen species (mtROS) in cholesterol-treated HUVECs., Conclusions: We demonstrated that idebenone acted as a mitochondrial protective agent by inhibiting the activation of NLPR3 via the SIRT3-SOD2-mtROS pathway. Idebenone may be a promising therapy for patients with atherosclerosis by improving mitochondrial dysfunction and inhibiting oxidative stress., (© 2020. Springer Science+Business Media, LLC, part of Springer Nature.)

Competitive endogenous RNAs (ceRNAs), as a newly identified regulating mechanism, have been demonstrated to play a crucial role in various human diseases. An increasing number of recent studies have revealed that circular RNAs (circRNAs) can function as ceRNAs. However, little is known about the role of circFAM160A2 in the pathological process of osteoarthritis (OA). This study is the first to examine the crucial role of the circFAM160A2-miR-505-3p-SIRT3 axis in osteoarthritis progression. miR-505-3p was selected from the interaction of a microRNA (miRNA) microarray comparing chondrocytes in OA and normal conditions and prediction results from TargetScan. RT-qPCR was performed to assess the expression of circFAM160A2, miR-505-3p, and SIRT3. A dual luciferase assay was used to validate the binding of circFAM160A2, miR-505-3p, and SIRT3. We used lentivirus and adeno-associated virus to establish in vitro and in vivo overexpression models. Western blotting, apoptosis assay, ROS detection assay, Safranin O staining, and CCK-8 assay were employed to assess the role of circFAM160A2, miR-505-3p, and SIRT3. We found that miR-505-3p was upregulated and circFAM160A2 was downregulated in OA. While overexpression of circFAM160A2 decreased the production of extracellular matrix (ECM) degrading enzymes and ameliorated chondrocyte apoptosis and mitochondrial dysfunction, inhibition of miR-505-3p could reverse the protective effect of circFAM160A2 on the OA phenotype both in vitro and in vivo. In conclusion, circFAM160A2 can promote mitochondrial stabilization and apoptosis reduction in OA chondrocytes by targeting miR-505-3p and SIRT3, which might be a potential therapeutic target for OA therapy., Competing Interests: All authors have no conflicts of interest to declare., (Copyright © 2021 Jiapeng Bao et al.)

It has been documented that aging increases the risk of cardiovascular disease including myocardial ischemia/reperfusion (IR) injury and acute myocardial infarction. In this study, we aimed to investigate the individual or combined effects of nicotinamide mononucleotide (NMN) and melatonin (Mel) treatment on apoptotic markers, expression of SIRT3, and FOXO1, and infarct size of the aged myocardium subjected to IR injury. Sixty aged Wistar rats (22-24 months) were assigned to five groups including sham, IR, NMN+IR, Mel+IR, and NMN+Mel+IR (combination therapy). Isolated hearts were exposed to 30-min regional ischemia followed by 60-min reperfusion. NMN (100 mg/kg/day/i.p.) was injected every second day starting on day 28 before IR injury. Melatonin was added to the perfusion solution five minutes prior to and until 15 min after the start of reperfusion. The infarct size was assessed by computerized planimetry. The mRNA levels of SIRT3, FOXO1, and apoptotic genes Bax, Bcl-2, and Caspase-3 were estimated by real-time PCR. All treatments reduced infarct size as compared with the IR group. Melatonin and NMN upregulated the gene expression of Bcl-2, SIRT3, and FOXO1 and downregulated the gene expression of Bax, and Caspase-3, in comparison to the IR group. Also, the protein levels of SIRT3, quantified by Western blotting, were upregulated by the interventions. The effects of combination therapy were significantly greater than those of melatonin or NMN alone. These findings indicate that the combined administration of NMN and melatonin can protect the aged heart against IR injury by decreasing apoptosis and activating the SIRT3/FOXO1 pathway.

Background and Purpose: Hepatic fatty acid metabolism disorder, a key pathogenic mechanism underlying non-alcoholic fatty liver disease (NAFLD), is associated with the hyperacetylation of mitochondrial enzymes. Acyl-CoA synthetase family member 3 (ACSF3), which is involved in the regulation of fatty acid metabolism, was predicted to contain lysine acetylation sites related to the mitochondrial deacetylase sirtuin 3 (SIRT3). The purpose of this study was to explore the underlying mechanism by which SIRT3 deacetylates ACSF3 in NAFLD and the protective effect of the natural phenolic compound protocatechuic acid (PCA) against fatty acid metabolism disorder via the SIRT3/ACSF3 pathway., Experimental Approach: The role of protocatechuic acid and its molecular mechanism in NAFLD were detected in rats and SIRT3-knockout mice fed a high-fat diet (HFD) and in AML-12 cells treated with palmitic acid (PA)., Key Results: Pharmacological treatment with protocatechuic acid significantly attenuated high-fat diet-induced fatty acid metabolism disorder in NAFLD. Molecular docking assays showed that protocatechuic acid specifically bound SIRT3 as a substrate and increased SIRT3 protein expression. However, the protective role of protocatechuic acid was abolished by SIRT3 knockdown, which increased ACSF3 expression and exacerbated fatty acid metabolism disorder. Mechanistically, SIRT3 was shown to specifically regulate the acetylation and degradation of ACSF3, which govern the capacity of ACSF3 to mediate fatty acid metabolism disorder during NAFLD., Conclusion and Implications: SIRT3-mediated ACSF3 deacetylation is a novel molecular mechanism in NAFLD therapy and protocatechuic acid confers protection against high-fat diet- and palmitic acid-induced hepatic fatty acid metabolism disorder through the SIRT3/ACSF3 pathway., (© 2020 The British Pharmacological Society.)

Background: Alzheimer's disease (AD) features reductions in key bioenergetic fluxes and perturbed mitochondrial function. Cytoplasmic hybrids (cybrids) generated through the transfer of AD subject mitochondria to mtDNA-depleted SH-SY5Y neuroblastoma cells recapitulate some of these features in an in vitro setting., Objective: For this study, we used the AD cybrid model to assess the impact of a nutrient-excess like-state via increasing O-GlcNAcylation on whole cell and mitochondrial homeostasis., Methods: We induced increased O-GlcNAc by treating AD and control cybrid cell lines with Thiamet G (TMG), an inhibitor of the O-GlcNAcase enzyme that mediates removal of the nutrient-dependent O-GlcNAc modification., Results: Relative to control cybrid cell lines, AD cybrid lines showed a blunted response to TMG-induced O-GlcNAcylation. At baseline, AD cybrid cell line mitochondria showed partial activation of several proteins that help maintain bioenergetic homeostasis such as AMP-Regulated Kinase suggesting that AD mitochondria initiate a state of nutrient stress promoting energetic compensation; however, this compensation reduces the capacity of cells to respond to additional nutrient-related stresses such as TMG treatment. Also, TMG caused disruptions in acetylation and Sirtuin 3 expression, while lowing total energetic output of the cell., Conclusion: Together, these findings suggest that modulation of O-GlcNAc is essential for proper energetic function of the mitochondria, and AD mitochondrial capacity to handle nutrient-excess is limited.

Berberine (BBR) shows promising effects in the treatment of nonalcoholic fatty liver disease (NAFLD) by influencing various metabolic aspects. Inhibition of mitochondrial β-oxidation (β-OX) participates in the pathogenesis of NAFLD. Silent mating-type information regulation 2 homolog 3 (SIRT3) has been reported to regulate mitochondrial β-OX by deacetylating its substrate, long-chain acyl-coenzyme A dehydrogenase (LCAD). This study aimed to explore whether BBR can promote mitochondrial β-OX and the role of SIRT3 as well as the mechanisms underlying the effects of BBR on hepatic lipid metabolism in mice fed a high-fat diet (HFD). BBR can significantly improve systematic and hepatic lipid metabolism in HFD-fed mice. Metabolomics analysis revealed that β-OX was inhibited in HFD-induced mice, as indicated by the reduced production of short and medium carbon chain acyl-carnitines, the activated form of free fatty acids, via β-OX, which was reversed by BBR intervention. Exploration of the mechanism found that BBR intervention reversed the down-regulation of SIRT3 and decreased the LCAD hyperacetylation level in HFD-fed mice. SIRT3 knockout (KO) mice were used to identify the role of SIRT3 in the BBR's influence of β-OX. The beneficial effects of BBR on systemic and hepatic metabolism were profoundly attenuated in KO mice. Moreover, the promotive effect of BBR on β-OX in HFD-induced mice was partially abolished in KO mice. These results suggested that BBR alleviates HFD-induced inhibition of fatty acid β-OX partly through SIRT3-mediated LCAD deacetylation, which may provide a novel mechanism and support BBR as a promising therapeutic for NAFLD.-Xu, X., Zhu, X.-P., Bai, J.-Y., Xia, P., Li, Y., Lu, Y., Li, X.-Y., Gao, X. Berberine alleviates nonalcoholic fatty liver induced by a high-fat diet in mice by activating SIRT3.

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, AT 1 , 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, AT 1 , 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 AT 2 and SIRT3 protein expression. In BV-2 microglia treated with Azilsartan, a specific inhibitor of AT 1 (AT 1 I group), NOX-2 expression was decreased whereas that of SIRT3 in LPS + AT 1 I and LPS + Gastrodin group was increased when compared with the controls. In LPS + AT 1 I + 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 AT 2 and SIRT3) and proinflammatory mediators e.g. TNF-α in activated microglia., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

BACKGROUND A mouse model of subarachnoid hemorrhage (SAH) investigated the effects of melatonin treatment on the generation of reactive oxygen species (ROS) and the activation of the SIRT3 gene in early brain injury (EBI). MATERIAL AND METHODS Male C57BL/6J mice were assigned to three groups: the SAH group; the sham group; and the SAH + melatonin-treated group (intraperitoneal dose, 150 mg/kg). TUNEL was used to study apoptosis of neuronal cells, Western-blot and immunohistochemistry detected expression of Sirt3, Bcl-2, superoxide dismutase 2 (SOD2), Bax, and cleaved caspase-3. Real-time polymerase chain reaction (PCR) and a luciferase reporter assay evaluated the effects of melatonin on SIRT3 gene expression. Malondialdehyde (MDA) and the reactive oxygen species (ROS) scavenger, reduced glutathione (GSH), and its ratio with oxidized glutathione (GSSG) was measured. RESULTS The increase in neurological score and increase in cerebral edema following SAH were reduced in the SAH + melatonin-treated group. Neuronal apoptosis following SAH was reduced in the SAH + melatonin-treated group. Increased levels of SOD2, Bax, and cleaved caspase-3 following SAH were reduced in the SAH + melatonin-treated group; reduced levels of Sirt3 and Bcl-2 following SAH were increased in the SAH + melatonin-treated group. The GSH: GSSG ratio was increased, and the MDA level was decreased when melatonin treatment was used following SAH. Melatonin upregulated SIRT3 expression by increasing the transcription efficiency of the SIRT3 promoter in human glioma cell lines U87 and U251. CONCLUSIONS Melatonin provided protection from the effects of EBI following SAH by regulating the expression of murine SIRT3.

Honokiol (poly-phenolic lignan from Magnolia grandiflora) is a Sirtuin-3 (SIRT3) activator which exhibit antioxidant activity and augment mitochondrial functions in several experimental models. Modern evidence suggests the critical role of SIRT3 in the progression of several metabolic and neurodegenerative diseases. Amyloid beta (Aβ), the precursor to extracellular senile plaques, accumulates in the brains of patients with Alzheimer's disease (AD) and is related to the development of cognitive impairment and neuronal cell death. Aβ is generated from amyloid-β precursor protein (APP) through sequential cleavages, first by β-secretase and then by γ-secretase. Drugs modulating this pathway are believed to be one of the most promising strategies for AD treatment. In the present study, we found that Honokiol significantly enhanced SIRT3 expression, reduced reactive oxygen species generation and lipid peroxidation, enhanced antioxidant activities, and mitochondrial function thereby reducing Aβ and sAPPβ levels in Chinese Hamster Ovarian (CHO) cells (carrying the amyloid precursor protein-APP and Presenilin PS1 mutation). Mechanistic studies revealed that Honokiol affects neither protein levels of APP nor α-secretase activity. In contrast, Honokiol increased the expression of AMPK, CREB, and PGC-1α, thereby inhibiting β-secretase activity leading to reduced Aβ levels. These results suggest that Honokiol is an activator of SIRT3 capable of improving antioxidant activity, mitochondrial energy regulation, while decreasing Aβ, thereby indicating it to be a lead compound for AD drug development.

The sirtuins, silent mating-type information regulation 2 (SIRTs), are a family of nicotinamide adenine dinucleotide (NAD + )-dependent histone deacetylases with important roles in regulating energy metabolism and senescence. Activation of SIRTs appears to have beneficial effects on lipid metabolism and antioxidants, prompting investigation of the roles of these proteins in atherogenesis. Although clinical data are currently limited, the availability and safety of SIRT activators such as metformin and resveratrol provide an excellent opportunity to conduct research to better understand the role of SIRTs in human atherosclerosis. Encouraging observations from preclinical studies necessitate rigorous large, prospective, randomized clinical trials to determine the roles of SIRT activators on the progression of atherosclerosis and ultimately on cardiac outcomes, such as myocardial infarction and mortality., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Advanced glycation end products (AGEs) have been confirmed to induce dysfunction in endothelial progenitor cells (EPCs) and play key roles in pathogenesis of diabetes-related vascular complications. The major function of sirtuin 3 (SIRT3) is to orchestrate oxidative metabolism and control reactive oxygen species (ROS) homeostasis, which are more closely related to EPCs' dysfunction. Our study therefore was designed to explore the role of SIRT3 on AGEs-induced EPCs dysfunction of. EPCs isolated from healthy adults were stimulated with AGEs and the expression of SIRT3 was assessed. Then, EPCs transfected with ad-SIRT3 or siRNA-SIRT3 were cultured with or without AGEs. EPCs function, including proliferation, migration; expression of manganese superoxide dismutase (MnSOD), ROS production, and interleukin-8 (IL-8); and vascular endothelial growth factor (VEGF) production were measured. In some experiments, EPCs were pre-cultured with anti-receptor for advanced glycation end products (RAGE) antibody or anti-neutralizing antibody, and then proliferation, migration, expression of MnSOD, ROS production, and IL-8 and VEGF production were measured. Our results showed that SIRT3 expressed in EPCs and AGEs decreased SIRT3 expression. SIRT3 knockdown with siRNA-SIRT3 promoted dysfunction in EPCs whereas SIRT3 activation with ad-SIRT3 strengthened anti-oxidant capacity and protected AGE-impaired dysfunction. Moreover, RAGE may involve in AGEs-decreased SIRT3 expression in EPCs. These data suggested an important role of SIRT3 in regulating EPCs bioactivity.

Clinical application of triptolide (TP), a main active ingredient of the traditional Chinese herb Tripterygium wilfordii Hook f. (TWHF), is limited by a series of severe toxicities, including cardiotoxicity. In previous studies, we found the activation of sirtuin 3 (SIRT3) attenuated TP-induced toxicity in cardiomyocytes. Resveratrol (RSV), a polyphenol from the skins of grapes and red wine, is an activator of SIRT3. The current study aimed to investigate the protective effect of RSV against TP-induced cardiotoxicity and the underlying mechanisms. Mice were treated with a single dose of TP (2.5 mg/kg) via the intragastric (i.g.) route. After 24 h, TP induced abnormal changes of serum biochemistry, activity decrease of antioxidant enzymes and damage of heart tissue such as myocardial fiber rupture, cell swelling and interstitial congestion. In contrast, administration with RSV (50 mg/kg i.g. 12 h before and 2 h after the administration of TP) attenuated the detrimental effects induced by TP in BALB/c mice. Moreover, the cardiomyocyte protective effects of RSV on TP-induced heart injury were associated with the activation of SIRT3 and its downstream targets. In vitro study also indicated that RSV counteracted TP-induced cardiotoxicity through SIRT3-FOXO3 signaling pathway in H9c2 cells. Collectively, these findings suggest the potential of RSV as a promising agent in protecting heart from TP-induced damage.

Stroke is one of the leading causes of death. Growing evidence indicates that ketone bodies have beneficial effects in treating stroke, but their underlying mechanism remains unclear. Our previous study showed ketone bodies reduced reactive oxygen species by using NADH as an electron donor, thus increasing the NAD(+)/NADH ratio. In this study, we investigated whether mitochondrial NAD(+)-dependent Sirtuin 3 (SIRT3) could mediate the neuroprotective effects of ketone bodies after ischemic stroke. We injected mice with either normal saline or ketones (beta-hydroxybutyrate and acetoacetate) at 30 minutes after ischemia induced by transient middle cerebral artery (MCA) occlusion. We found that ketone treatment enhanced mitochondria function, reduced oxidative stress, and therefore reduced infarct volume. This led to improved neurologic function after ischemia, including the neurologic score and the performance in Rotarod and open field tests. We further showed that ketones' effects were achieved by upregulating NAD(+)-dependent SIRT3 and its downstream substrates forkhead box O3a (FoxO3a) and superoxide dismutase 2 (SOD2) in the penumbra region since knocking down SIRT3 in vitro diminished ketones' beneficial effects. These results provide us a foundation to develop novel therapeutics targeting this SIRT3-FoxO3a-SOD2 pathway.

Insulin resistance in skeletal muscle is a key feature in the pathogenesis of type 2 diabetes (T2D) that often manifests early in its development. Pharmaceutical and dietary strategies have targeted insulin resistance to control T2D, and many natural products with excellent pharmacological properties are good candidates for the control or prevention of T2D. Dihydromyricetin (DHM) is a natural flavonol which provides a wide range of health benefits including anti-inflammatory and anti-tumor effects. However, little information is available regarding the effects of DHM on skeletal muscle insulin sensitivity as well as the underlying mechanisms. In the present study, we found that DHM activated insulin signaling and increased glucose uptake in skeletal muscle in vitro and in vivo. The expression of light chain 3, the degradation of sequestosome 1, and the formation of autophagosomes were also upregulated by DHM. DHM-induced insulin sensitivity improvement was significantly abolished in the presence of 3-methyladenine, bafilomycin A1, or Atg5 siRNA in C2C12 myotubes. Furthermore, DHM increased the levels of phosphorylated AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), and Sirt3 in skeletal muscle in vitro and in vivo. Autophagy was inhibited in the presence of Sirt3 siRNA in C2C12 myotubes and in skeletal muscles from Sirt3-/- mice. Additionally, PGC-1α or AMPK siRNA transfection attenuated DHM-induced Sirt3 expression, thereby abrogating DHM-induced autophagy in C2C12 myotubes. In conclusion, DHM improved skeletal muscle insulin sensitivity by partially inducing autophagy via activation of the AMPK-PGC-1α-Sirt3 signaling pathway.

Nonalcoholic steatosis is an important hepatic complication of obesity linked to mitochondrial dysfunction and oxidative stress. Lipoic acid (LA) has been reported to have beneficial effects on mitochondrial function and to attenuate oxidative stress. The sirtuin (SIRT) family has been demonstrated to play an important role in the regulation of mitochondrial function and in the activation of antioxidant defenses. In this study, we analyzed the potential protective effect of LA supplementation, via the modulation of mitochondrial defenses through the SIRT pathway, against oxidative stress associated with high-fat feeding. Wistar rats were fed a standard diet (control group (C), n = 10), a high-fat diet (obese group (OB), n = 10) and a high-fat diet supplemented with LA (OLIP, n = 10). A group pair-fed to the latter group (pair-fed OLIP group (PFO), n = 6) was also included. LA prevented hepatic triglyceride (TG) accumulation (-68.2%) and liver oxidative damage (P < 0.01) through the inhibition of hydroperoxide (H(2)O(2)) production (P < 0.001) and the stimulation of mitochondrial antioxidant defenses. LA treatment upregulated manganese superoxide dismutase (SOD2) (60.6%) and glutathione peroxidase (GPx) (100.2%) activities, and increased the reduced glutathione (GSH): oxidized glutathione (GSSG) ratio and UCP2 mRNA levels (P < 0.001-P < 0.01). Moreover, this molecule reduced oxidative damage in mitochondrial DNA (mtDNA) and increased mitochondrial copy number (P < 0.001- P < 0.01). LA treatment decreased the acetylation levels of Forkhead transcription factor 3a (Foxo3a) and PGC1β (P < 0.001- P < 0.01) through the stimulation of SIRT3 and SIRT1 (P < 0.001). In summary, our results demonstrate that the beneficial effects of LA supplementation on hepatic steatosis could be mediated by its ability to restore the oxidative balance by increasing antioxidant defenses through the deacetylation of Foxo3a and PGC1β by SIRT1 and SIRT3.