PGC-1α Acetylation Research Articles

PGC-1α repression dysregulates lipid metabolism and induces lipid droplet accumulation in the retinal pigment epithelium

Drusen, the yellow deposits under the retina, are composed of lipids and proteins, and represent a hallmark of age-related macular degeneration (AMD). Lipid droplets are also reported in the retinal pigment epithelium (RPE) from AMD donor eyes. However, the mechanisms underlying these disease phenotypes remain elusive. Previously, we showed that Pgc-1α repression, combined with a high-fat diet (HFD), induce drastic AMD-like phenotypes in mice. We also reported increased PGC-1α acetylation and subsequent deactivation in the RPE derived from AMD donor eyes. Here, through a series of in vivo and in vitro experiments, we sought to investigate the molecular mechanisms by which PGC-1α repression could influence RPE and retinal function. We show that PGC-1α plays an important role in RPE and retinal lipid metabolism and function. In mice, repression of Pgc-1α alone induced RPE and retinal degeneration and drusen-like deposits. In vitro inhibition of PGC1A by CRISPR-Cas9 gene editing in human RPE (ARPE19- PGC1A KO) affected the expression of genes responsible for lipid metabolism, fatty acid β-oxidation (FAO), fatty acid transport, low-density lipoprotein (LDL) uptake, cholesterol esterification, cholesterol biosynthesis, and cholesterol efflux. Moreover, inhibition of PGC1A in RPE cells caused lipid droplet accumulation and lipid peroxidation. ARPE19-PGC1A KO cells also showed reduced mitochondrial biosynthesis, impaired mitochondrial dynamics and activity, reduced antioxidant enzymes, decreased mitochondrial membrane potential, loss of cardiolipin, and increased susceptibility to oxidative stress. Our data demonstrate the crucial role of PGC-1α in regulating lipid metabolism. They provide new insights into the mechanisms involved in lipid and drusen accumulation in the RPE and retina during aging and AMD, which may pave the way for developing novel therapeutic strategies targeting PGC-1α.

LncRNA NORAD defects deteriorate the formation of age-related macular degeneration.

Long noncoding RNAs (lncRNAs) play important roles in the development of age-related macular degeneration (AMD). However, the effect of long non-coding RNA activated by DNA damage (NORAD) on AMD remains unknown. This study aimed to investigate the effect of NORAD on RPE cell senescence and degeneration. Irradiated adult retinal pigment epithelial cell line-19 (ARPE-19) and sodium iodate-treated mice were used as in vitro and in vivo AMD models. Results showed that irradiation-induced AMD characteristics of ARPE-19 and NORAD-knockdown aggravated cell cycle arrest in the G2/M phase, cell apoptosis and cell senescence along with the increased expression of phosphorylated P53 (p-P53) and P21. AMD factors C3, ICAM-1, APP, APOE, and VEGF-A were also increased by NORAD-knockdown. Moreover, NORAD-knockdown increased irradiation-induced reduction of mitochondrial homeostasis factors, (i.e., TFAM and POLG) and mitochondrial respiratory chain complex genes (i.e., ND1 and ND5) along with mitochondrial reactive oxygen species (ROS). We also identified a strong interaction of NORAD and PGC-1α and sirtuin 1 (SIRT1) in ARPE-19; that is, NORAD knockdown increases the acetylation of PGC-1α. In NORAD knockout mice, NORAD-knockout accelerated the sodium iodate-reduced retinal thickness reduction, function impairment and loss of retinal pigment in the fundus. Therefore, NORAD-knockdown accelerates retinal cell senescence, apoptosis, and AMD markers via PGC-1α acetylation, mitochondrial ROS, and the p-P53-P21signaling pathway, in which NORAD-mediated effect on PGC-1α acetylation might occur through the direct interaction with PGC-1α and SIRT1.

Mitochondrial energy metabolism is downregulated in repeated implantation failure patients related to alteration of PGC-1α acetylation level.

Herein we aimed at exploring mitochondrial energy metabolism status in patients with repeated implantation failure (RIF) and whether key regulatory factor PGC-1α of energy metabolism is involved in the decidualization of endometrial stromal cells. Mitochondrial oxidative phosphorylation level and ATP synthesis were compared in primary endometrial stromal cells from RIF and control group. At the same time, as one of key transcription regulators of mitochondrial energy metabolism, the expression level and acetylation level of PGC-1α were compared with two groups. Then, we downregulated the acetylation levels of PGC-1α, and the expression of decidual markers (PRL and IGFBP1) was observed further. Mitochondrial energy metabolism, showing by mitochondrial oxidative phosphorylation level and ATP synthesis, was decreased in the endometrial stromal cells of the RIF group (RIF-hEnSCs). Meanwhile, PGC-1α acetylation levels were significantly higher in RIF-hEnSCs. When we reduced the acetylation levels of PGC-1α in RIF-hEnSCs, the basal O2 consumption rate and maximal respiration were increased, and also the PRL and IGFBP1. Overall, our data indicated that the endometrial stromal cells of the RIF patients had low level of mitochondrial energy metabolism. Reducing acetylation level of key energy metabolism regulator PGC-1α can increase the decidualization level of RIF-hEnSCs. These findings may inspire new ideas about the treatment of RIF.

Effects of Gestational Hypoxia on PGC1α and Mitochondrial Acetylation in Fetal Guinea Pig Hearts

Chronic intrauterine hypoxia is a significant pregnancy complication impacting fetal heart growth, metabolism, and mitochondrial function, contributing to cardiovascular programming of the offspring. PGC1α (peroxisome proliferator-activated receptor γ co-activator 1α) is the master regulator of mitochondrial biogenesis. We investigated the effects of hypoxia on PGC1α expression following exposure at different gestational ages. Time-mated pregnant guinea pigs were exposed to normoxia (NMX, 21% O2) or hypoxia (HPX, 10.5% O2) at either 25-day (early-onset) or 50-day (late-onset) gestation, and all fetuses were extracted at term (term = ~65-day gestation). Expression of nuclear PGC1α, sirtuin 1 (SIRT1), AMP-activated protein kinase (AMPK), and mitochondrial sirtuin 3 (SIRT3) was measured, along with SIRT3 activity and mitochondrial acetylation of heart ventricles of male and female fetuses. Early-onset hypoxia increased (P<0.05) fetal cardiac nuclear PGC1α and had no effect on mitochondrial acetylation of either growth-restricted males or females. Late-onset hypoxia had either no effect or decreased (P<0.05) PCC1α expression in males and females, respectively, but increased (P<0.05) mitochondrial acetylation in both sexes. Hypoxia had variable effects on expression of SIRT1, AMPK, SIRT3, and SIRT3 activity depending on the sex. The capacity of the fetal heart to respond to hypoxia differs depending on the gestational age of exposure and sex of the fetus. Further, the effects of late-onset hypoxia on fetal heart function impose a greater risk to male than female fetuses, which has implications toward cardiovascular programming effects of the offspring.

Both prolonged high-fat diet consumption and calorie restriction boost hepatic NAD+ metabolism in mice

Hepatic NAD+ homeostasis is essential to metabolic flexibility upon energy balance challenges. The molecular mechanism is unclear. This study aimed to determine how the enzymes involved in NAD+ salvage (Nampt, Nmnat1, Nrk1), clearance (Nnmt, Aox1, Cyp2e1), and consumption pathways (Sirt1, Sirt3, Sirt6, Parp1, Cd38) were regulated in the liver upon energy overload or shortage, as well as their relationships with glucose and lipid metabolism. Male C57BL/6N mice were fed ad libitum with the CHOW diet, high-fat diet (HFD), or subjected to 40% calorie restriction (CR) CHOW diet for 16 weeks respectively. HFD feeding increased hepatic lipids content and inflammatory markers, while lipids accumulation was not changed by CR. Both HFD feeding and CR elevated the hepatic NAD+ levels, as well as gene and protein levels of Nampt and Nmnat1. Furthermore, both HFD feeding and CR lowered acetylation of PGC-1α in parallel with the reduced hepatic lipogenesis and enhanced fatty acid oxidation, while CR enhanced hepatic AMPK activity and gluconeogenesis. Hepatic Nampt and Nnmt gene expression negatively correlated with fasting plasma glucose levels concomitant with positive correlations with Pck1 gene expression. Nrk1 and Cyp2e1 gene expression positively correlated with fat mass and plasma cholesterol levels, as well as Srebf1 gene expression. These data highlight that hepatic NAD+ metabolism will be induced for either the down-regulation of lipogenesis upon over nutrition or up-regulation of gluconeogenesis in response to CR, thus contributing to the hepatic metabolic flexibility upon energy balance challenges.

Garcinol Promotes the Formation of Slow-Twitch Muscle Fibers by Inhibiting p300-Dependent Acetylation of PGC-1α.

The conversion of skeletal muscle fiber from fast-twitch to slow-twitch is crucial for sustained contractile and stretchable events, energy homeostasis, and anti-fatigue ability. The purpose of our study was to explore the mechanism and effects of garcinol on the regulation of skeletal muscle fiber type transformation. Forty 21-day-old male C57/BL6J mice (n = 10/diet) were fed a control diet or a control diet plus garcinol at 100 mg/kg (Low Gar), 300 mg/kg (Mid Gar), or 500 mg/kg (High Gar) for 12 weeks. The tibialis anterior (TA) and soleus muscles were collected for protein and immunoprecipitation analyses. Dietary garcinol significantly downregulated (p < 0.05) fast myosin heavy chain (MyHC) expression and upregulated (p < 0.05) slow MyHC expression in the TA and soleus muscles. Garcinol significantly increased (p < 0.05) the activity of peroxisome proliferator-activated receptor gamma co-activator 1α (PGC-1α) and markedly decreased (p < 0.05) the acetylation of PGC-1α. In vitro and in vivo experiments showed that garcinol decreased (p < 0.05) lactate dehydrogenase activity and increased (p < 0.05) the activities of malate dehydrogenase and succinic dehydrogenase. In addition, the results of C2C12 myotubes showed that garcinol treatment increased (p < 0.05) the transformation of glycolytic muscle fiber to oxidative muscle fiber by 45.9%. Garcinol treatment and p300 interference reduced (p < 0.05) the expression of fast MyHC but increased (p < 0.05) the expression of slow MyHC in vitro. Moreover, the acetylation of PGC-1α was significantly decreased (p < 0.05). Garcinol promotes the transformation of skeletal muscle fibers from the fast-glycolytic type to the slow-oxidative type through the p300/PGC-1α signaling pathway in C2C12 myotubes.

Myostatin Knockout Affects Mitochondrial Function by Inhibiting the AMPK/SIRT1/PGC1α Pathway in Skeletal Muscle.

Myostatin (Mstn) is a major negative regulator of skeletal muscle mass and initiates multiple metabolic changes. The deletion of the Mstn gene in mice leads to reduced mitochondrial functions. However, the underlying regulatory mechanisms remain unclear. In this study, we used CRISPR/Cas9 to generate myostatin-knockout (Mstn-KO) mice via pronuclear microinjection. Mstn-KO mice exhibited significantly larger skeletal muscles. Meanwhile, Mstn knockout regulated the organ weights of mice. Moreover, we found that Mstn knockout reduced the basal metabolic rate, muscle adenosine triphosphate (ATP) synthesis, activities of mitochondrial respiration chain complexes, tricarboxylic acid cycle (TCA) cycle, and thermogenesis. Mechanistically, expressions of silent information regulator 1 (SIRT1) and phosphorylated adenosine monophosphate-activated protein kinase (pAMPK) were down-regulated, while peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) acetylation modification increased in the Mstn-KO mice. Skeletal muscle cells from Mstn-KO and WT were treated with AMPK activator 5-aminoimidazole-4-carboxamide riboside (AICAR), and the AMPK inhibitor Compound C, respectively. Compared with the wild-type (WT) group, Compound C treatment further down-regulated the expression or activity of pAMPK, SIRT1, citrate synthase (CS), isocitrate dehydrogenase (ICDHm), and α-ketoglutarate acid dehydrogenase (α-KGDH) in Mstn-KO mice, while Mstn knockout inhibited the AICAR activation effect. Therefore, Mstn knockout affects mitochondrial function by inhibiting the AMPK/SIRT1/PGC1α signaling pathway. The present study reveals a new mechanism for Mstn knockout in regulating energy homeostasis.

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.

Pyrroloquinoline quinone (PQQ) protects mitochondrial function of HEI-OC1 cells under premature senescence

The aim of this study was to investigate the effects of pyrroloquinoline quinone (PQQ), an oxidoreductase cofactor, on the H2O2-induced premature senescence model in HEI-OC1 auditory cells and to elucidate its mechanism of action in vitro. Cells were treated with PQQ for 1 day before H2O2 (100 μM) exposure. Mitochondrial respiratory capacity was damaged in this premature senescence model but was restored in cells pretreated with PQQ (0.1 nM or 1.0 nM). A decrease in mitochondrial potential, the promotion of mitochondrial fusion and the accelerated movement of mitochondria were all observed in PQQ-pretreated cells. The protein expression of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) were significantly decreased under H2O2 exposure while they were increased with PQQ pretreatment, and PGC-1α acetylation was significantly decreased. In conclusion, PQQ has a protective effect on the premature senescence model of HEI-OC1 auditory cells and is associated with the SIRT1/PGC-1α signaling pathway, mitochondrial structure, and mitochondrial respiratory capacity.

Resveratrol reduces DRP1-mediated mitochondrial dysfunction via the SIRT1-PGC1α signaling pathway in manganese-induced nerve damage in mice.

Excessive manganese (Mn) exposure can cause nerve damage and mitochondrial dysfunction, which may involve defects in mitochondrial dynamics. Resveratrol (RSV) exerts a wide range of beneficial effects via activation of sirtuin 1 (SIRT1) and thus may positively impact Mn-induced mitochondrial damage through the regulation of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) by SIRT1. In this study, we investigated the molecular mechanisms by which RSV alleviates the nerve injury and mitochondrial fragmentation caused by Mn in C57 BL/6 mice. Our results demonstrated that RSV activated the deacetylase activity of SIRT1 and protected against the surge of mitochondrial reactive oxygen species, the loss of mitochondrial membrane potential, and the attenuation of ATP caused by Mn. RSV, therefore, inhibits mitochondrial fragmentation and safeguards neural cells. Increased deacetylase activity led to a reduction in the acetylation of PGC-1α, which directly regulates DRP1 expression by binding to the DRP1 promoter. The resultant attenuation of DRP1-mediated mitochondrial fragmentation in RSV-pretreated mice was abolished by the addition of the SIRT1 inhibitor EX527. Taken together, these findings indicate that RSV alleviates Mn-induced mitochondrial dysfunction mediated by DRP1 by modulating the SIRT1/PGC-1α signaling pathway.

Mitochondrial Disruption Is Involved in the Effect of Nuclear Factor of Activated T cells, Cytoplasmic 4 on Aggravating Cardiomyocyte Hypertrophy.

Nuclear factor of activated T cells, cytoplasmic 4 (NFATc4), a nuclear transcription factor, has been implicated in cardiac hypertrophy through the enhancement of hypertrophic gene expression. However, the role of NFATc4 in mitochondrial modulation is mostly unknown. The current study aimed to investigate the role of NFATc4 in regulating mitochondrial function during phenylephrine (PE)-induced cardiac hypertrophy. Our results showed that overexpression of NFATc4 aggravated the PE-induced decrease in mitochondrial genesis, membrane potential, and mitochondrial gene expression as well as impaired mitochondrial respiration. However, knockdown of NFATc4 relieved PE-induced perturbations in mitochondria and cardiomyocyte hypertrophy. Mechanistically, by activating phosphoinositide-dependent kinase 1 and promoting a combination of AKT and phosphoinositide-dependent kinase 1, phosphorylation and sequential acetylation of PGC-1α were aggravated by NFATc4 and suppressed the activity of PGC-1α. In conclusion, NFATc4-regulated factors were shown to be associated with mitochondrial function and exacerbated PE-induced mitochondrial dysfunction. These findings revealed new roles of NFATc4 in cardiac hypertrophy.

A SIRT1 Activator, Ginsenoside Rc, Promotes Energy Metabolism in Cardiomyocytes and Neurons.

Targeting SIRT1 signaling pathway could improve glucose aerobic metabolism and mitochondrial biosynthesis to resist cardiac and neurological injuries. Ginsenoside Rc has been identified for targeting mitochondrial function, but how ginsenoside Rc interacts with SIRT1 to regulate energy metabolism in cardiomyocytes and neurons under physiological or ischemia/reperfusion (I/R)-injured conditions has not been clearly investigated. Here, we confirm the interaction of Rc on the residue sites of SIRT1 in promoting its activity. Ginsenoside Rc significantly promotes mitochondrial biogenesis and increases the levels of electron-transport chain complex II-IV in cardiomyocytes and neurons. Meanwhile, ginsenoside Rc pretreatment increases ATP production, glucose uptake, and the levels of hexokinase I/II and mitochondrial pyruvate carrier I/II in both cell models. In addition, ginsenoside Rc activates the PGC1α pathway to induce mitochondrial biosynthesis. More importantly, ginsenoside Rc reduces mitochondrial damage and apoptosis through SIRT1 restoration-mediated reduction of PGC1α acetylation in the I/R-induced cardiac and neuronal models. Collectively, the in vitro and in vivo data indicate that ginsenoside Rc as a SIRT1 activator promotes energy metabolism to improve cardio- and neuroprotective functions under normal and I/R injury conditions, which provides new insights into the molecular mechanism of ginsenoside Rc as a protective agent.

Measuring PGC-1α and Its Acetylation Status in Mouse Primary Myotubes.

Metabolic flexibility is vital for organisms to respond to and survive changes in energy availability. A critical metabolic flexibility regulator is peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), which regulates various transcription factors and nuclear receptors that, in turn, regulate mitochondrial homeostasis and fatty acid oxidation. PGC-1α is itself regulated, with one of the significant modes of regulation being acetylation. Thus, measuring the acetylation status of PGC-1α is a critical indicator of cells' metabolic flexibility. In this chapter, we describe a method of evaluating PGC-1α acetylation in primary mouse myotubes. This method can also be used with other cell types and tissues.

Adipose Tissue SIRT1 Regulates Insulin Sensitizing and Anti-Inflammatory Effects of Berberine.

Berberine (BBR), which is an active component of Coptis chinensis Franch, has been reported to improve glucose metabolism and insulin resistance in animal and human studies, predominantly via activation of the 5′-adenosine monophosphate kinase (AMPK) pathway and suppression of the inflammation response. However, the mechanisms underlying the effects of BBR on AMPK and inflammation remain unclear. In this present study, we found that BBR upregulated SIRT1 expression in 3T3L-1 adipocytes and adipose tissue. Inhibition of SIRT1 blunted the BBR-induced increase in glucose consumption and uptake in adipocytes. The BBR-induced activation of the AMPK pathway and AKT phosphorylation in adipocytes and adipose tissue were also attenuated by inhibition or knockout of Sirt1. The BBR-induced improvement of systemic insulin sensitivity was impaired by Sirt1 knockout in HFD-induced obese mice. The suppressing effects of BBR on systemic and local inflammatory responses, such as serum concentrations and expression of inflammatory cytokines, phosphorylation of c-Jun N-terminal kinase (JNK) and IKKβ, and the accumulation of F4/80-positive macrophages in adipose tissue were also attenuated in Sirt1 knockout mice. The BBR-induced decrease in PGC-1α acetylation was reversed by inhibition or knockout of Sirt1 in adipocytes and adipose tissue. Together, these results indicate that adipose tissue SIRT1 is a key regulator of the insulin sensitizing and anti-inflammatory effects of BBR, which contributes to the improvement of metabolic dysregulation.

Garcinol promotes hepatic gluconeogenesis by inhibiting P300/CBP-associated factor in late-pregnant sows.

Disorder of hepatic glucose metabolism is the characteristic of late-pregnant sows. The purpose of our study was to look into the mechanism of garcinol on the improvement of hepatic gluconeogenic enzyme in late-pregnant sows. Thirty second- and third-parity sows (Duroc × Yorkshire × Landrace, n 10/diet) were fed a basal diet (control) or that diet supplemented with 100 mg/kg (Low Gar) or 500 mg/kg (High Gar) garcinol from day 90 of gestation to the end of farrowing. The livers were processed to measure enzymatic activity. Hepatocytes from pregnant sows were transfected with P300/CBP-associating factor (PCAF) small interfering RNA (siRNA) or treated with garcinol. Dietary garcinol had no effect on average daily feed intake, body weight (BW), backfat and BW gain of late-pregnant sows. Garcinol promoted plasma glucose levels in pregnant sows and newborn piglets. Garcinol up-regulated hepatic gluconeogenic enzyme expression and decreased PCAF activity. Garcinol had no effect on the expression of PPAR-γ co-activator 1α (PGC-1α) and Forkhead box O1 (FOXO1) but significantly increased their activity and decreased their acetylation in late-pregnant sows. Transfection of PCAF siRNA to hepatocytes of pregnant sows increased PGC-1α and FOXO1 activities. Furthermore, in hepatocytes of pregnant sows, garcinol treatment also up-regulated the activities of PGC-1α and FOXO1 and inhibited the acetylation of PGC-1α and FOXO1. Garcinol improves hepatic gluconeogenic enzyme expression in late-pregnant sows, and this may be due to the mechanism of down-regulating the acetylation of PGC-1α and FOXO1 induced by PCAF in isolated hepatocytes.

458-P: Resveratrol Attenuates Diabetic Cardiomyopathy by Inhibiting Asymmetric Dimethylarginine-Induced PGC-1a Acetylation

The cardiac protection of resveratrol may due to improvement of mitochondrial function through SIRT1 activation and PGC-1α deacetylation. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthases, is associated with diabetic cardiovascular complications and reported to have cross-talk with lysine acetylation in cells. This study was to determine the role of ADMA in the pathogenesis of diabetic cardiomyopathy, whether resveratrol could revise ADMA-induced pathological changes and elucidate the underlying mechanisms in rat model of type 2 diabetes mellitus (T2DM). Resveratrol was orally administered (50mg/kg/d) to T2DM rats for 16w. Echocardiography was performed to detect cardiac function. Contents of myocardial ATP and mitochondrial DNA were measured to evaluate mitochondrial function and biogenesis. Elevated endogenous ADMA content and its signal disorders were associated with cardiac and mitochondrial dysfunction in the myocardium of T2DM rats compared with control rats. Treatment with resveratrol significantly attenuated endogenous ADMA accumulation and cardiac dysfunction, increased myocardial mitochondrial DNA and ATP contents, as well as upregulated PGC-1α expression in the myocardium of resveratrol-treated diabetic rats compared with untreated diabetic rats. A positive feedback was observed in vitro that elevated ADMA return promoting its synthetic enzyme PRMT1 expression, reducing its metabolic enzymes DDAH2 expression, reproducing myocardial hypertrophy and mitochondrial dysfunction. Resveratrol treatment could reverse these pathological changes. More importantly, ADMA could enhance PGC-1α acetylation and reduced SIRT1 expressions, all of which were antagonized by resveratrol in cardiomyocytes. These results suggest that ADMA-induced PGC-1α hyperacetylation may serve as potential therapeutic targets for resveratrol to improve diabetic cardiomyopathy.

Regulation of PGC-1α mediated by acetylation and phosphorylation in MPP+ induced cell model of Parkinson's disease.

Background: Parkinson’s disease (PD) is one of the most common neurodegenerative diseases with complex etiology in sporadic cases. Accumulating evidence suggests that oxidative stress and defects in mitochondrial dynamics are associated with the pathogenesis of PD. The oxidative stress and mitochondrial dynamics are regulated strictly by peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). We investigated whether acetylation and phosphorylation of PGC-1α contribute to protecting neuronal cell against oxidative stress.Results: We found that acetylation and phosphorylation mediated the nuclear translocation of PGC-1α protects against oxidative damage. In contrast to the increased nuclear PGC-1α, the cytosolic PGC-1α was decreased upon inhibition of GCN5 acetyltransferase. Similarly to the inhibition of GCN5 acetyltransferase, the increased nuclear PGC-1α and the decreased cytosolic PGC-1α were observed upon p38MAPK and AMPK activation. Briefly, the significantly increased nuclear PGC-1α is regulated either by inhibiting the acetylation of PGC-1α or by the phosphorylating PGC-1α, which results in a reduction in ROS.Conclusion: PGC-1α protects neuronal cells against MPP+-induced toxicity partially through the acetylation of PGC-1α mediated by GCN5, and mostly through the phosphorylation PGC-1α mediated by p38MAPK or AMPK. Therapeutic reagents activating PGC-1α may be valuable for preventing mitochondrial dysfunction in PD by against oxidative damage.Methods: With established the 1-methyl-4-phenylpyridinium (MPP+)-induced cell model of PD, the effects of MPP+ and experimental reagents on the cell viability was investigated. The expression of PGC-1α, general control of nucleotide synthesis 5 (GCN5), p38 mitogen-activated protein kinase (p38MAPK) and adenosine monophosphate activated protein kinase (AMPK) were detected by Western blotting and quantitative real-time PCR. The level of reactive oxygen species (ROS) was measured by flow cytometry. All statistical analyses were carried out using one-way ANOVA.

Exendin-4 Protects Against Myocardial Ischemia-Reperfusion Injury by Upregulation of SIRT1 and SIRT3 and Activation of AMPK.

This study evaluatedif the cardioprotectiveeffect of Exendin-4 against ischemia/reperfusion (I/R) injury in male rats involves modulation of AMPK and sirtuins. Adult male rats were divided into sham, sham + Exendin-4, I/R, I/R + Exendin-4, and I/R + Exendin-4 + EX-527, a sirt1 inhibitor. Exendin-4 reduced infarct size and preserved the function and structure of the left ventricles (LV) of I/R rats. It also inhibited oxidative stress and apoptosis and upregulated MnSOD and Bcl-2 in their infarcted myocardium. With no effect on SIRTs 2/6/7, Exendin-4 activated and upregulated mRNA and protein levels of SIRT1, increased levels of SIRT3 protein, activated AMPK, and reduced the acetylation of p53 and PGC-1α as well as the phosphorylation of FOXO-1. EX-527 completely abolished all beneficial effects of Exendin-4 in I/R-induced rats. In conclusion, Exendin-4 cardioprotective effect against I/R involves activation of SIRT1 and SIRT3. Graphical Abstract Exendin-4 could scavenge free radical directly, upregulate p53, andthrough upregulation of SIRT1 and stimulating SIRT1nuclear accumulation. In addition, Exendin-4 also upregulates SIRT3 which plays an essential role in the upregulation of antioxidants, inhibition of reactive oxygen species (ROS) generation, and prevention of mitochondria damage. Accordingly, SIRT1 induces the deacetylation of PGC-1α and p53 and is able to bind p-FOXO-1. This results in inhibition of cardiomyocyte apoptosis through increasing Bcl-2 levels, activity, and levels of MnSOD; decreasing expression of Bax; decreasing cytochrome C release; and improving mitochondria biogenesis through upregulation of Mfn-2.

Dysregulated metabolic pathways in age-related macular degeneration

Age-related macular degeneration is a major cause of vision impairment in the Western world among people of 55 years and older. Recently we have shown that autophagy is dysfunctional in the retinal pigment epithelium (RPE) of the AMD donor eyes (AMD RPE). We also showed increased reactive oxygen (ROS) production, increased cytoplasmic glycogen accumulation, mitochondrial dysfunction and disintegration, and enlarged and annular LAMP-1-positive organelles in AMD RPE. However, the underlying mechanisms inducing these abnormalities remain to be elucidated. Here, by performing a comprehensive study, we show increased PAPR2 expression, deceased NAD+, and SIRT1, increased PGC-1α acetylation (inactive form), lower AMPK activity, and overactive mTOR pathway in AMD RPE as compared to normal RPE. Metabolomics and lipidomics revealed dysregulated metabolites in AMD RPE as compared to normal RPE, including glycerophospholipid metabolism, involved in autophagy, lipid, and protein metabolisms, glutathione, guanosine, and L-glutamic acid, which are implicated in protection against oxidative stress and neurotoxicity, further supporting our observations. Our data show dysregulated metabolic pathways as important contributors to AMD pathophysiology, and facilitate the development of new treatment strategies for this debilitating disease of the visual system.

Combined overexpression of SIRT1 and knockout of GCN5 in adult skeletal muscle does not affect glucose homeostasis or exercise performance in mice.

Sirtuin 1 (SIRT1) and general control of amino acid synthesis 5 (GCN5) regulate mitochondrial biogenesis via opposing modulation of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) acetylation status and activity. However, the combined contribution of SIRT1 and GCN5 to skeletal muscle metabolism and endurance performance in vivo is unknown. In this study, we investigated the impact of combined skeletal muscle-specific overexpression of SIRT1 and deletion of GCN5 on glucose homeostasis, skeletal muscle mitochondrial biogenesis and function, and metabolic adaptation to endurance exercise training in mice. We generated mice with combined and tamoxifen-inducible skeletal muscle-specific overexpression of SIRT1 and knockout of GCN5 (dTG) and floxed [wild type (WT)] littermates using a Cre-LoxP approach. All mice were treated with tamoxifen at 5-6 wk of age, and 4-7 wk later glucose homeostasis, skeletal muscle contractile function, mitochondrial function, and the effects of 14 days of voluntary wheel running on expression of metabolic proteins and exercise capacity were assessed. There was no difference in oral glucose tolerance, skeletal muscle contractile function, mitochondrial abundance, or maximal respiratory capacity between dTG and WT mice. Additionally, there were no genotype differences in exercise performance and markers of mitochondrial biogenesis after 14 days of voluntary wheel running. These results demonstrate that combined overexpression of SIRT1 and loss of GCN5 in vivo does not promote metabolic remodeling in skeletal muscle of sedentary or exercise-trained mice.