Abstract 9328: Sirt5 Deficiency Promotes Metabolic Reprogramming to Aggravate Cardiac Fibrosis

Introduction: Metabolic remodeling is critically involved in the pathogenesis of cardiac fibrosis. Glycolytic switch provides rapid energy production and biosynthetic intermediates to support proliferation and collagen synthesis of fibroblast. Sirtuin 5 (Sirt5) is a protein lysine de-succinylase that impacts diverse metabolic pathways. Objective: This study aimed to determine the function and mechanism of Sirt5 in cardiac fibroblast activation and cardiac fibrosis. Methods and Results: SIRT5 expression was examined in human and mouse myocardia, and was found to be downregulated in fibrotic myocardial tissues compared to non-fibrotic tissues. In a mouse model of myocardial infarction, Sirt5-knockout (KO) mice showed more severe cardiac fibrosis compared with wild-type mice. The aggravating cardiac fibrosis of Sirt5-KO mice were also found after transverse aortic constriction or angiotensin II plus phenylephrine-infusion. Proliferation and collagen synthesis of cardiac fibroblasts (CFBs) were both significantly enhanced by SIRT5 deficiency after AngII/PE-infusion in vivo and transform growth factor (TGF)-β1-treatment in vitro , but were attenuated by overexpression of Sirt5 in vitro . Moreover, Sirt5 deficiency enhanced a metabolic switch from oxidative phosphorylation to glycolysis in the isolated CFBs, and inhibition of glycolysis diminished the effect of Sirt5 deficiency on CFBs activation. Mechanistically, lysine succinylome analysis identified phosphoenolpyruvate carboxykinase 2 (Pck2), a rate-limiting enzyme in glycolysis pathway, as the protein mostly succinylated after Sirt5 deficiency. Activity of Pck2 was significantly inhibited by Sirt5 deficiency-mediated hypersuccinylation both in vivo and in vitro . K489R mutation of Pck2 diminished its succinylation and the reduction of its enzymatic activity mediated by Sirt5 deficiency, which also blunted the effect of Sirt5 deficiency on CFBs activation. Conclusions: Sirt5 deficiency enhances a metabolic reprogramming from oxidative phosphorylation to glycolysis in CFBs by succinylating Pck2, which promotes CFBs activation and aggravates cardiac fibrosis.