PGC-1α Deacetylation Research Articles

Resveratrol improved mitochondrial biogenesis by activating SIRT1/PGC-1α signal pathway in SAP

NLRP3 inflammasomes- pyroptosis axis is activated by microcirculation dysfunction and touched off severe acute pancreatitis (SAP). Activation of PGC-1α can improve microcirculation dysfunction by promoting mitochondrial biogenesis. Resveratrol (RSV), one typical SIRT1 agonist, possesses the ability of alleviating SAP and activing PGC-1α. Therefore, the study was designated to explore whether the protective effect of RSV in SAP was though suppressing NLRP3 inflammasomes- pyroptosis axis via advancing SIRT1/PGC-1α-dependent mitochondrial biogenesis. The models of SAP were induced by treating with sodium taurodeoxycholate in rats and AR42J cells. The pathological injury, water content (dry/wet ratio) and microcirculation function of pancreas, activity of lipase and amylase were used to evaluate pancreatic damage. The expression of inflammatory cytokine was measured by ELISA and RT-PCR. The damage of mitochondrial was evaluated by measuring the changes in Mitochondrial Membrane Potential (ΔΨm), mitochondrial ROS, ATP content and MDA as well as relocation of mtDNA and the activity of SOD and GSH. The expressions of NLRP3 inflammasomes- pyroptosis axis proteins were detected by Western blotting as well as SIRT1/PGC-1α/NRF1/TFAM pathway protein. Moreover, the modification of PGC-1α was measured by co-immunoprecipitation. The results displayed that RSV can significantly improve the damage of pancreas and mitochondrial, decrease the expression of pro-inflammatory factor and the activation of NLRP3 inflammasomes- pyroptosis axis, promote the expression of an-inflammatory factor and the deacetylation of PGC-1α together with facilitating SIRT1/PGC-1α-mediating mitochondrial biogenesis. Therefore, the protective effect of RSV in SAP is though inactivation of NLRP3 inflammasomes- pyroptosis axis via promoting mitochondrial biogenesis in a SIRT1/PGC-1α-dependent manner.

Sirt1-mediated deacetylation of PGC-1α alleviated hepatic steatosis in type 2 diabetes mellitus via improving mitochondrial fatty acid oxidation

Being activated by deacetylation, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) has become an important regulator of metabolic-related diseases. The activation of Sirtuin 1 (Sirt1) by resveratrol was likely to deacetylate PGC-1α. However, the role of deacetylated PGC-1α in the alleviation of activated Sirt1 on type 2 diabetes mellitus (T2DM)-related fatty liver disease (FLD) remained unexplored. The aim of this study was to investigate the potential impact of Sirt1-mediated deacetylation of PGC-1α on T2DM-associated FLD and its underlying mechanisms. Our findings revealed that, along with the decreased Sirt1, the levels of acetylated PGC-1α were up-regulated in hepatocytes co-stimulated with high glucose (HG) and free fatty acids (FFA). Down-regulated Sirt1 inactivated PGC-1α by inhibiting its deacetylation, while activating Sirt1 improved hepatic injury by reducing lipid droplet accumulation through the deacetylation of PGC-1α. However, the beneficial effects of Sirt1 activation on hepatic steatosis were inhibited by PGC-1α antagonist in vitro. Mechanistically, activating Sirt1 enhanced mitochondrial function by promoting PGC-1α activity, thereby facilitating hepatic fatty acid oxidation (FAO). In conclusion, Sirt1-mediated deacetylation of PGC-1α mitigated hepatic lipotoxicity by enhancing mitochondrial FAO, which contributed to the restoration of mitochondrial function in T2DM. The activation of Sirt1-mediated PGC-1α deacetylation might represent a promising therapeutic approach for T2DM-associated FLD.

Gut microbiota-derived indole-3-propionic acid alleviates diabetic kidney disease through its mitochondrial protective effect via reducing ubiquitination mediated-degradation of SIRT1

IntroductionGut microbes and their metabolites play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, which one and how specific gut-derived metabolites affect the progression of DKD remain largely unknown. ObjectivesThis study aimed to investigate the potential roles of indole-3-propionic acid (IPA), a microbial metabolite of tryptophan, in DKD. MethodsMetagenomic sequencing was performed to analyze the microbiome structure in DKD. Metabolomics screening and validation were conducted to identify characteristic metabolites associated with DKD. The protective effect of IPA on DKD glomerular endothelial cells (GECs) was assessed through in vivo and in vitro experiments. Further validation via western blot, immunoprecipitation, gene knockout, and site-directed mutation elucidated the mechanism of IPA on mitochondrial injury. ResultsAlterations in gut microbial community structure and dysregulated tryptophan metabolism were evident in DKD mice. Serum IPA levels were significantly reduced in DKD patients and correlated with fasting blood glucose, HbA1c, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR). IPA supplementation ameliorated albuminuria, bolstered the integrity of the glomerular filtration barrier, and mitigated mitochondrial impairments in GECs. Mechanistically, IPA hindered SIRT1 phosphorylation-mediated ubiquitin–proteasome degradation, restoring SIRT1′s role in promoting PGC-1α deacetylation and nuclear translocation, thereby upregulating genes associated with mitochondrial biosynthesis and antioxidant defense. ConclusionOur findings underscore the potential of the microbial metabolite IPA to attenuate DKD progression, offering novel insights and potential therapeutic strategies for its management.

The promotion of fatty acid β-oxidation by hesperidin via activating SIRT1/PGC1α to improve NAFLD induced by a high-fat diet.

Reducing fat deposits in hepatocytes is a direct treatment for nonalcoholic fatty liver disease (NAFLD) and the fatty acid metabolic processes mediated by fatty acid β-oxidation are important for the prevention of NAFLD. In this study, we established high-fat-diet models in vitro and in vivo to investigate the mechanism by which hesperidin (HDN) prevents NAFLD by modulating fatty acid β oxidation. Based on LC-MS screening of differential metabolites, many metabolites involved in phospholipid and lipid metabolism were found to be significantly altered and closely associated with fatty acid β-oxidation. The results from COIP experiments indicated that HDN increased the deacetylation of PGC1α by SIRT1. In addition, the results of CETSA and molecular docking experiments suggest that HDN targeting of SIRT1 plays an important role in their stable binding. Meanwhile, it was found that HDN reduced fatty acid uptake and synthesis and promoted the expression of SIRT1/PGC1α and fatty acid β-oxidation, and the latter process was inhibited after transfection to knockdown SIRT1. The results suggest that HDN improves NAFLD by promoting fatty acid β-oxidation through activating SIRT1/PGC1α. Thus, the findings indicate that HDN may be a potential drug for the treatment of NAFLD.

Formononetin promotes fatty acid β-oxidation to treat non-alcoholic steatohepatitis through SIRT1/PGC-1α/PPARα pathway

BackgroundNon-alcoholic steatohepatitis (NASH), the progressive form of non-alcoholic fatty liver disease (NAFLD), carries a high risk of cirrhosis and hepatocellular carcinoma. With the increasing incidence of NASH, the accompanying medical burden is also increasing rapidly, so the development of safe and reliable drugs is urgent. Formononetin (FMNT) has a variety of pharmacological effects such as antioxidant and anti-inflammation, and plays a major role in regulating lipid metabolism, reducing hepatic steatosis and so on, but the mechanism for alleviating NASH is unclear. Materials and methodsWe firstly established a mouse model on NASH through methionine-choline deficient (MCD) diet to investigate the improvement of FMNT as well as the effects of fatty acid β oxidation and SIRT1/PGC-1α/PPARα pathway. Then, we explored the mechanisms of FMNT regulation in SIRT1/PGC-1α/PPARα pathway and fatty acid β oxidation based on genes silencing of SIRT1 and PGC1A. In addition, SIRT1 agonist (SRT1720) and inhibitor (EX527) were used to verify the mechanism of FMNT on improvement of NASH. ResultsOur study found that after FMNT intervention, activities of ALT and AST and TG level were improved, and liver function and hepatocellular steatosis on NASH mice were significantly improved. The detection of β oxidation related indicators showed that FMNT intervention up-regulated FAO capacity, level of carnitine, and the levels of ACADM and CPT1A. The detection of factors related to the SIRT1/PGC-1α/PPARα pathway showed that FMNT activated and promoted the expression of SIRT1/PGC-1α/PPARα pathway, including up-regulating the expression level of SIRT1, improving the activity of SIRT1, promoting the deacetylation of PGC-1α, and promoting the transcriptional activity of PPARα. Furthermore, after genes silencing of SIRT1 and PGC1A, we found that FMNT intervention could not alleviate NASH, including improvement of hepatocellular steatosis, enhancement of β oxidation, and regulation of SIRT1/PGC-1α/PPARα pathway. Afterwards, we used SRT1720 as a positive control, and the results indicated that FMNT and SRT1720 intervention had no significant difference on improving hepatocellular steatosis and promoting fatty acid β oxidation. Besides, we found that when EX527 intervention inhibited expression of SIRT1, the improvement of FMNT on NASH was weakened or even disappeared. ConclusionIn summary, our results demonstrated that FMNT intervention activated SIRT1/PGC-1α/PPARα pathway to promote fatty acid β oxidation and regulate lipid metabolism in liver, ultimately improved hepatocellular steatosis on NASH mice.

Naringenin ameliorates vascular senescence and atherosclerosis involving SIRT1 activation.

This study was to explore the potential effects and mechanism of naringenin against vascular senescence in atherosclerosis focusing on the SIRT1-mediated signalling pathway. Aged apoE-/- mice were administrated with naringenin continuously for three months. Lipid parameters in serum and pathological changes and associated protein expression in aorta were examined. In vitro, endothelial cells were treated with H2O2 to induce senescence. Dyslipidemia, atherosclerotic lesion formation and vascular senescence were found in ApoE-/- mice, which were significantly ameliorated by naringenin treatment. Naringenin decreased reactive oxygen species overproduction and enhanced the activities of antioxidant enzymes in aorta. It also decreased mitoROS production and increased protein expressions of mitochondrial biogenesis-related genes in aorta. Moreover, naringenin treatment enhanced aortic protein expression and activity of SIRT1. Meanwhile, naringenin increased deacetylation and protein expression of SIRT1's target genes FOXO3a and PGC1α. In vitro study, the benefits of naringenin on endothelial senescence, oxidative stress and mitochondrial injury as well as protein expressions and acetylated levels of FOXO3a and PGC1α were diminished in cells transfected with SIRT1 siRNA. Naringenin could ameliorate vascular senescence and atherosclerosis and the activation of SIRT1, with subsequent deacetylation and regulation of FOXO3a and PGC1α, is involved in this process.

Hippocampus mitochondrial MnSOD activation by a SIRT3 activator, honokiol, correlates with its deacetylation and upregulation of FoxO3a and PGC1α in a rat model of ammonia neurotoxicity.

We have recently reported that honokiol (HKL), by activating mitochondrial SIRT3, normalizes reactive oxygen species level and mitochondrial integrity in hippocampus of the moderate grade hepatic encephalopathy (MoHE) rat model of ammonia neurotoxicity. To delineate the mechanism by which HKL does so, the present study describes activity versus level of the deacetylated mitochondrial Mn-superoxide dismutase (MnSOD) and expression of MnSOD versus levels of its main transcription regulators, FoxO3a and PGC1α, in the hippocampus of the MoHE rats. MoHE in rat was developed by administration of 100 mg/kg bw thioacetamide i.p. for 10 days. The study parameters were compared between the control, the MoHE rats and the MoHE rats treated with HKL (10 mg/Kg b.w.) for 7 days. As compared to control, the hippocampus mitochondria from MoHE rats showed a significantly declined activity of MnSOD vs enhanced lipid peroxidation coinciding with the increased level of its acetylated form. The HKL treatment could, however, normalize all these parameters in those MoHE rats. Also, a significantly reduced expression of MnSOD in the hippocampus of the MoHE rats coincided with a similar decline in transcript level of Foxo3a and Pgc1α. This was consistent with the reduced level of immuno-stained Foxo3a and Pgc1α proteins in hippocampus DG, CA1 and CA3 regions of those MoHE rats. However, all these factors were observed to be restored back to their normal levels due to the treatment with HKL. As HKL is a specific activator of mitochondrial SIRT3, these findings suggest involvement of Sirt3 activation led deacetylation of MnSOD and upregulation of its transcription activators, FoxO3a and PGC1α, in restoring mitochondrial MnSOD level in the hippocampus of the MoHE rat model of ammonia neurotoxicity.

PGC-1α/NRF1-dependent cardiac mitochondrial biogenesis: A druggable pathway of calycosin against triptolide cardiotoxicity.

Mitochondrion-related cardiotoxicity due to cardiotoxin stimuli is closely linked to abnormal activities of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), followed by co-inactivation of nuclear respiratory factor-1(NRF1). Pharmacological interventions targeting mitochondria may be effective for developing agents against cardiotoxicity. Herein, in triptolide-treated H9C2 cardiomyocytes, we observed defective mitochondrial biogenesis and respiration, characterized by depletion of mitochondrial mass and mitochondrial DNA copy number, downregulation of mitochondrial respiratory chain complexes subunits, and disorders of mitochondrial membrane potential and mitochondrial oxidative phosphorylation. Dysregulation of mitochondria led to cardiac pathological features, such as myocardial fiber fracture, intercellular space enlargement, and elevation of serum aspartate aminotransferase, creatine kinase isoenzyme, lactate dehydrogenase, and cardiac troponin I. However, following calycosin treatment, an active compound from Astragali Radix, the mitochondrion-related disorders at both cell and tissue levels were significantly ameliorated, which was facilitated by the activation of PGC-1α via deacetylation, followed by NRF1 co-activation. Calycosin-enhanced PGC-1α deacetylation is impelled by increasing sirtuin-1 expression and NAD+/NADH ratio. PGC-1α/NRF1 signaling in calycosin-mediated mitochondrial biogenesis protection was further confirmed by NRF1 knockdown and PGC-1α inhibition with SR18292. We conclude that calycosin ameliorated triptolide-induced cardiotoxicity by protecting PGC-1α/NRF1-dependent cardiac mitochondrial biogenesis and respiration, which is the druggable pathway for cardiotoxicity mitigation.

NAD Supplement Alleviates Intestinal Barrier Injury Induced by Ethanol Via Protecting Epithelial Mitochondrial Function.

The epithelial tight junction is an important intestinal barrier whose disruption can lead to the release of harmful intestinal substances into the circulation and cause damage to systemic injury. The maintenance of intestinal epithelial tight junctions is closely related to energy homeostasis and mitochondrial function. Nicotinamide riboside (NR) is a NAD booster that can enhance mitochondrial biogenesis in liver. However, whether NR can prevent ethanol-induced intestinal barrier dysfunction and the underlying mechanisms remain unclear. We applied the mouse NIAAA model (chronic plus binge ethanol feeding) and Caco-2 cells to explore the effects of NR on ethanol-induced intestinal barrier dysfunction and the underlying mechanisms. NAD homeostasis and mitochondrial function were measured. In addition, knockdown of SirT1 in Caco-2 cells was further applied to explore the role of SirT1 in the protection of NR. We found that ethanol increased intestinal permeability, increased the release of LPS into the circulation and destroyed the intestinal epithelial barrier structure in mice. NR supplementation attenuated intestinal barrier injury. Both in vivo and in vitro experiments showed that NR attenuated ethanol-induced decreased intestinal tight junction protein expressions and maintained NAD homeostasis. In addition, NR supplementation activated SirT1 activity and increased deacetylation of PGC-1α, and reversed ethanol-induced mitochondrial dysfunction and mitochondrial biogenesis. These effects were diminished with the knockdown of SirT1 in Caco-2 cells. Boosting NAD by NR alleviates ethanol-induced intestinal epithelial barrier damage via protecting mitochondrial function in a SirT1-dependent manner.

Resveratrol improves diabetic cardiomyopathy by preventing asymmetric dimethylarginine-caused peroxisome proliferator-activated receptor-γ coactivator-1α acetylation

ObjectivesCardiac protection of resveratrol is related to the improvement of mitochondrial function through sirtuin1 (SIRT1) activation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) deacetylation. Asymmetric dimethylarginine (ADMA) as an endogenous inhibitor of nitric oxide synthases is associated with diabetic cardiovascular complications and has a cross-talk with lysine acetylation. This study was to determine whether resveratrol reverses ADMA's pathogenic role in diabetic cardiomyopathy and elucidate the underlying mechanisms in type 2 diabetic (T2DM) rats and cardiomyocytes. MethodsT2DM Rats were induced by high-fat diet plus small-dose streptozotocin injection (35 mg/kg). Resveratrol was given by gavage (50 mg/kg/d) to some rats for 16w. Cardiac function was measured by echocardiography, and PGC-1α acetylation was detected by immunoprecipitation. Mitochondrial DNA and ATP contents were analyzed to evaluate mitochondrial biogenesis and function. ResultsEndogenous ADMA accumulation and its signal disorders were associated with cardiac and mitochondrial dysfunctions in accompany with increased PGC-1α acetylation and decreased PGC-1α expression in the myocardium of T2DM rats compared with control rats. Resveratrol treatment attenuated ADMA accumulation, cardiac and mitochondrial dysfunctions in parallel with reversing altered PGC-1α expression and acetylation in the myocardium of T2DM rats. Exogenous ADMA not only reproduced mitochondrial dysfunction and cardiac hypertrophy but also reduced PGC-1α expression and enhanced PGC-1α acetylation in accompany of down-regulating SIRT1 and up-regulating acetyltransferase expression, all of which could be prevented by resveratrol pretreatment in cardiomyocytes. ConclusionsThese results indicate that ADMA promotes PGC-1α acetylation as a potential therapeutic target for resveratrol of management diabetic cardiomyopathy in T2DM rats.

Nicotinamide riboside promotes Mfn2-mediated mitochondrial fusion in diabetic hearts through the SIRT1-PGC1α-PPARα pathway

Myocardial dysfunction is associated with an imbalance in mitochondrial fusion/fission dynamics in patients with diabetes. However, effective strategies to regulate mitochondrial dynamics in the diabetic heart are still lacking. Nicotinamide riboside (NR) supplementation ameliorated mitochondrial dysfunction and oxidative stress in both cardiovascular and aging-related diseases. This study investigated whether NR protects against diabetes-induced cardiac dysfunction by regulating mitochondrial fusion/fission and further explored the underlying mechanisms. Here, we showed an evident decrease in NAD+ (nicotinamide adenine dinucleotide) levels and mitochondrial fragmentation in the hearts of leptin receptor-deficient diabetic (db/db) mouse models. NR supplementation significantly increased NAD+ content in the diabetic hearts and promoted mitochondrial fusion by elevating Mfn2 level. Furthermore, NR-induced mitochondrial fusion suppressed mitochondrial H2O2 and O2•− production and reduced cardiomyocyte apoptosis in both db/db mice hearts and neonatal primary cardiomyocytes. Mechanistically, chromatin immunoprecipitation (ChIP) and luciferase reporter assay analyses revealed that PGC1α and PPARα interdependently regulated Mfn2 transcription by binding to its promoter region. NR treatment elevated NAD+ levels and activated SIRT1, resulting in the deacetylation of PGC1α and promoting the transcription of Mfn2. These findings suggested the promotion of mitochondrial fusion via oral supplementation of NR as a potential strategy for delaying cardiac complications in patients with diabetes.

IBF-R, a botanical extract of Rhus verniciflua controls obesity in which AMPK-SIRT1 axis and ROS regulatory mechanism are involved in mice

Obesity is a major health concern worldwide and adds woes to the quality of life. Several natural herbs have been shown protective effects against obesity. Here, we investigated the protective effect of Rhus verniciflua extract (IBF-R) against obesity and the underlying mechanism in obese mice. IBF-R alleviated body weight, liver weight as well as adipose tissue weight without altering food intake. IBF-R extract reduced lipogenesis and adipogenesis in liver and epididymal white adipose tissue (eWAT). At the molecular level, AMPK-SIRT1 axis increased, and mTOR-SREBP1-ER stress axis decreased. In brown adipose tissue (BAT), IBF-R administration increased mitochondrial biogenesis and thermogenesis markers like PGC1α and UCP1 via AMPK-SIRT1 signaling and mTOR-SREBP1-ER stress-mitochondrial function axis. Moreover, IBF-R influenced the recovery of PGC1α deacetylation via SIRT1 activation. These observations suggest that IBF-R protects against obesity by playing multiple modulatory roles in liver steatosis, adipocyte metabolism, and BAT function mediated by AMPK-SIRT1 axis and ROS regulating pathways.

Resveratrol-induced Sirt1 phosphorylation by LKB1 mediates mitochondrial metabolism

The NAD+-dependent deacetylase Sirt1 has been implicated in the prevention of many age-related diseases, including cancer, type 2 diabetes, and cardiovascular disease. Resveratrol, a plant polyphenol, exhibits antiaging, antitumor, and vascular protection effects by activating Sirt1. However, the molecular mechanism of Sirt1 activation as induced by resveratrol remains unclear. By knockdown/rescue experiments, fluorometric Sirt1 activity assay, immunoprecipitation, and pull-down assays, we identify here that the tumor suppressor LKB1 (liver kinase B1) as a direct activator of Sirt1 elicited by resveratrol. Resveratrol promotes the binding between LKB1 and Sirt1, which we first reported, and this binding leads to LKB1-mediated phosphorylation of Sirt1 at three different serine residues in the C terminus of Sirt1. Mechanistically, LKB1-mediated phosphorylation increases intramolecular interactions in Sirt1, such as the binding of the C terminus to the deacetylase core domain, thereby eliminating DBC1 (Deleted in Breast Cancer 1, Sirt1 endogenous inhibitor) inhibition and promoting Sirt1–substrate interaction. Functionally, LKB1-dependent Sirt1 activation increases mitochondrial biogenesis and respiration through deacetylation and activation of the transcriptional coactivator PGC-1α. These results identify Sirt1 as a context-dependent target of LKB1 and suggest that a resveratrol-stimulated LKB1-Sirt1 pathway plays a vital role in mitochondrial metabolism, a key physiological process that contributes to numerous age-related diseases.

Omega-3 Fatty Acids Upregulate SIRT1/3, Activate PGC-1α via Deacetylation, and Induce Nrf1 Production in 5/6 Nephrectomy Rat Model.

Mitochondrial dysfunction contributes to the pathogenesis of kidney injury related with cardiovascular disease. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) protects renal tubular cells by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2). AMP-activated protein kinase (pAMPK)-mediated phosphorylation and sirtuin 1/3 (SIRT1/3)-mediated deacetylation are required for PGC-1α activation. In the present study, we aimed to investigate whether omega-3 fatty acids (FAs) regulate the expression of mediators of mitochondrial biogenesis in 5/6 nephrectomy (Nx) rats. Male Sprague-Dawley rats were assigned to the following groups: sham control, Nx, and Nx treated with omega-3 FA. The expression of PGC-1α, phosphorylated PGC-1α (pPGC-1α), acetylated PGC-1α, and factors related to mitochondrial biogenesis was examined through Western blot analysis. Compared to the control group, the expression of PGC-1α, pAMPK, SIRT1/3, Nrf1, mTOR, and Nrf2 was significantly downregulated, and that of Keap 1, acetylated PGC-1α, and FoxO1/3, was significantly upregulated in the Nx group. These changes in protein expression were rescued in the omega-3 FA group. However, the expression of pPGC-1α was similar among the three groups. Omega-3 FAs may involve mitochondrial biogenesis by upregulating Nrf1 and Nrf2. This protective mechanism might be attributed to the increased expression and deacetylation of PGC-1α, which was triggered by SIRT1/3.

Curcumin induces mitochondrial biogenesis by increasing cyclic AMP levels via phosphodiesterase 4A inhibition in skeletal muscle.

Previous research has suggested that curcumin potentially induces mitochondrial biogenesis in skeletal muscle via increasing cyclic AMP (cAMP) levels. However, the regulatory mechanisms for this phenomenon remain unknown. The purpose of the present study was to clarify the mechanism by which curcumin activates cAMP-related signalling pathways that upregulate mitochondrial biogenesis and respiration in skeletal muscle. The effect of curcumin treatment (i.p., 100 mg/kg-BW/d for 28 d) on mitochondrial biogenesis was determined in rats. The effects of curcumin and exercise (swimming for 2 h/d for 3 d) on the cAMP signalling pathway were determined in the absence and presence of phosphodiesterase (PDE) or protein kinase A (PKA) inhibitors. Mitochondrial respiration, citrate synthase (CS) activity, cAMP content and protein expression of cAMP/PKA signalling molecules were analysed. Curcumin administration increased cytochrome c oxidase subunit (COX-IV) protein expression, and CS and complex I activity, consistent with the induction of mitochondrial biogenesis by curcumin. Mitochondrial respiration was not altered by curcumin treatment. Curcumin and PDE inhibition tended to increase cAMP levels with or without exercise. In addition, exercise increased the phosphorylation of phosphodiesterase 4A (PDE4A), whereas curcumin treatment strongly inhibited PDE4A phosphorylation regardless of exercise. Furthermore, curcumin promoted AMP-activated protein kinase (AMPK) phosphorylation and PPAR gamma coactivator (PGC-1α) deacetylation. Inhibition of PKA abolished the phosphorylation of AMPK. The present results suggest that curcumin increases cAMP levels via inhibition of PDE4A phosphorylation, which induces mitochondrial biogenesis through a cAMP/PKA/AMPK signalling pathway. Our data also suggest the possibility that curcumin utilises a regulatory mechanism for mitochondrial biogenesis that is distinct from the exercise-induced mechanism in skeletal muscle.

Research Article Short Alkyl Chain-Length Resorcinol Olivetol Protects Against Obesity with Mitochondrial Activation by Pgc-1α Deacetylation

Summary: The deacetylation of PGC-1α by the activation of sirtuins (SIRTs) with resveratrol (Res) promotes mitochondrial function and metabolic homeostasis. However, Res may not have the ability to specifically promote the deacetylation of PGC-1α by activating SIRT1. We investigated whether the specific deacetylation of PGC-1α is enhanced by increasing the rate of the enzyme-catalyzed reaction of SIRT1 and affects mitochondrial function and metabolic homeostasis. We previously demonstrated that alkylresorcinols (ARs) raised the Vmax of recombinant SIRT1 for NAD+ and extended the Drosophila melanogaster lifespan. Herein, we observed that treatment with the short alkyl chain-length resorcinol olivetol protected mice against diet-induced obesity with SIRT1 activation for PGC-1α. These olivetol effects were superior to Res for all parameters. Olivetol effects were associated with an induction of genes for lipid metabolism and were largely explained by PGC-1α deacetylation. Olivetol specifically activated PGC-1α deacetylation, increased mitochondrial numbers, and accelerated fat burning.

Trpv4 regulates Nlrp3 inflammasome via SIRT1/PGC-1α pathway in a cuprizone-induced mouse model of demyelination

Increasing evidence has demonstrated that the Nod-like receptor pyrin domain containing 3 (Nlrp3) inflammasome overactivated during demyelinating disorders. It has been implicated that transient receptor potential type 4 (Trpv4) is regarded as a polymodal ionotropic receptor that plays an important role in a multitude of pathological conditions, including inflammation. The aim of this study was to investigate whether the Trpv4 channel regulates Nlrp3 inflammasome in the corpus callosum of mice with demyelination. Our results showed that CPZ treatment significantly increased the expression of Trpv4, activated Nlrp3 inflammasome, reduced peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) and decreased mitochondrial function. siRNA-mediated Nlrp3 knockdown inhibited glial activation and alleviated demyelination. Whereas knockdown of Trpv4 by siRNA markedly ameliorated Nlrp3 inflammasome activation and restored mitochondrial function as well as reducing the level of reactive oxygen species (ROS). Meanwhile, glial activation, demyelination and behavioral impairment induced by CPZ were also alleviated by siRNA-mediated Trpv4 knockdown. Furthermore, immunoprecipitation and use of a lysine acetylation assay showed that Sirtuin1 (SIRT1) mediated the PGC-1α deacetylation, which is involved in Nlrp3 inflammasome activation. These findings suggest that Trpv4 regulates mitochondrial function through the SIRT1/PGC-1α pathway, which further trigger Nlrp3 inflammasome activation in the CPZ-induced demyelination in mice.

Naringenin alleviates nonalcoholic steatohepatitis in middle-aged Apoe−/−mice: role of SIRT1

BackgroundNaringenin is naturally isolated from citrus fruits possessing many pharmacological activities. However, little is known about the effect of naringenin on nonalcoholic steatohepatitis (NASH) in the model of metabolic syndrome. PurposeThe present study is aimed to investigate the effect of naringenin on NASH in 12-mo-old male ApoE−/− mice and its possible underlying mechanism. MethodsIn vivo, 12-mo-old male ApoE−/− mice were administrated with naringenin by intragastric gavage for 12 weeks. At the end of experiment, the blood samples and liver tissues were collected. Metabolic parameters in serum, levels of triglyceride, cholesterol and hydroxyproline, activities of antioxidant enzymes, and content of inflammatory cytokines (TNF-α and IL-6) in liver were examined by corresponding assay kits. Pathological changes in liver were observed by hematoxylin-eosin, oil red O, masson's trichrome, picro-sirius red and senescence β-galactosidase staining. Dihydroethidium was used for detection of reactive oxygen species (ROS). In vitro, AML-12 cells were treated with oleic acid in the presence or absence of naringenin for 24 h. Transfection of SIRT1 siRNA was also conducted in vitro. Lipid accumulation, cellular ROS generation, malondialdehyde content, antioxidant enzyme activities and secretion levels of TNF-α and IL-6 were examined. Both in vivo and in vitro, gene expressions were detected by real-time PCR or western blot. ResultsNaringenin administration improved metabolic parameters, suppressed hepatic steatosis, regulated expression of genes involved in lipid metabolism (FASN, SCD1, PPARα and CPT1α), reduced hepatic fibrosis and cell senescence, inhibited hepatic inflammation as evidenced by the decreased macrophage recruitment and content of TNF-α and IL-6, and reduced hepatic oxidative stress by suppressing ROS generation and normalizing activities of antioxidant enzymes. Notably, naringenin administration increased hepatic SIRT1 protein expression and activity along with the increased deacetylation of liver kinase B1 (LKB1), PGC1α and NF-κB. In vitro study, the benefits of naringenin on lipid accumulation, oxidative stress and inflammation were diminished by SIRT1 siRNA transfection. ConclusionsThese results indicate that naringenin administration may be a potential curative therapy for NASH treatment and the activation of hepatic SIRT1-mediated signaling cascades is involved in its beneficial effects.

Resveratrol-Induced Sirt1 Activation Derives from Sirt1 Phosphorylation by LKB1

The NAD+-dependent deacetylase Sirt1 is implicated in the prevention of many age-related diseases such as cancer, type 2 diabetes, and cardiovascular disease. Resveratrol, a plant polyphenol, exhibits anti-aging, anti-tumor and vascular protection effects by activating Sirt1. However, the molecular mechanism of Sirt1 activation induced by resveratrol remains unclear. Here, we identify the tumor suppressor LKB1 as a direct activator of Sirt1. Resveratrol promotes the binding between LKB1 and Sirt1, which drives LKB1 to directly phosphorylate Sirt1 at three different serine residues in the C-terminus. Mechanistically, LKB1-mediated phosphorylation increases the intramolecular interaction of Sirt1, that the binding of C-terminus to deacetylase core domain, thereby eliminating DBC1 inhibition and promoting Sirt1-substrate interaction. Functionally, LKB1-dependent Sirt1 activation increases mitochondrial biogenesis and respiration through deacetylation and activation of co-activator PGC-1α. These results uncover Sirt1 as a direct target of LKB1 and suggest that resveratrol-stimulated LKB1-Sirt1 pathway plays a vital role in mitochondrial metabolism.

Sirtuin 3 is required for the protective effect of Resveratrol on Manganese-induced disruption of mitochondrial biogenesis in primary cultured neurons.

Chronic manganese (Mn) exposure can disturb mitochondrial homeostasis leading to mitochondrial dysfunction, which is involved in Mn-induced neurodegenerative diseases. Resveratrol (RSV), as a promoter of mitochondrial biogenesis, plays a significant role against mitochondrial dysfunction. However, whether RSV can relieve Mn-induced neuronal injury and mitochondrial dysfunction remains unknown. Sirtuin 3 (SIRT3), a main mitochondrial sirtuin, is an important regulator of mitochondria to maintain mitochondrial homeostasis. Therefore, this study investigated whether SIRT3 was required for RSV alleviating Mn-induced mitochondrial dysfunction in primary cultured neurons from C57BL/6 mice. Here, we showed that Mn (100 and 200μM) exposure for 24hr caused significant neuronal damage and mitochondrial dysfunction through increasing mitochondrial ROS, reducing mitochondrial membrane potential and adenosine triphosphate level, and leading to mitochondrial network fragmentation, which could be ameliorated by RSV pretreatment in primary cultured neurons. Additionally, our results also indicated that RSV could activate the SIRT1/PGC-1α signaling pathway and alleviate Mn-induced disruption of mitochondrial biogenesis by increasing SIRT1 expression and activity, enhancing deacetylation of PGC-1α. Furthermore, SIRT3 over-expression increased deacetylation of mitochondrial transcription factor A and mitochondrial DNA (mtDNA) copy number. Oppositely, silencing SIRT3 increased acetylation of mitochondrial transcription factor A and decreased mtDNA copy number. Our results showed SIRT3 was required for the protective effect of RSV in mitochondrial biogenesis. In conclusion, our findings demonstrated that RSV could ameliorate Mn-induced neuronal injury and mitochondrial dysfunction in primary cultured neurons through activating the SIRT1/ PGC-1α signaling pathway, and that SIRT3 is required for promoting mitochondrial biogenesis and attenuating Mn-induced mitochondrial dysfunction.