SIRT5 affects lipid accumulation in cells of a metabolic-associated fatty liver disease model by regulating the succinylation status of HSPD1

BACKGROUND: Metabolic-associated fatty liver disease (MAFLD) is a liver disease characterized by abnormal lipid metabolism. This study investigated the effects of succinylation on hepatocyte steatosis and lipid storage in MAFLD in vitro. METHODS: mRNA and protein levels of two desuccinylases (SIRT5 and SIRT7) and three succinylases (KAT2A, KAT3B, and CPT1A) were evaluated in blood samples from MAFLD patients. Exposure of HepG2 and Huh7 cells to free fatty acids (FFA) was established to mimic MAFLD in vitro. Triglyceride (TG) content, total cholesterol (TC) content, and lipid accumulation were combined to evaluate lipid metabolism. HSPD1 protein was pulled-down using immunoprecipitation (IP). Co-immunoprecipitation (co-IP) combined with immunofluorescence was used to verify the interaction between SIRT5 and HSPD1. RESULTS: SIRT5 was prominently down-regulated in blood samples of patients with MAFLD. FFA exposure induced lipid metabolism dysfunction by increasing TC, TG levels, and the number of Oil Red O and BODIPY-stained lipid droplets. Overexpression of SIRT5 significantly attenuated the effects of FFA on lipid metabolism. HSPD1 was found to interact with SIRT5, which mediated HSPD1 desuccinylation and accelerated its protein degradation. Overexpression of HSPD1 sharply reversed the protective effects of elevated SIRT5 on cellular steatosis in HepG2 and Huh7 cells. SIRT5 directly interacted with HSPD1, and elevated SIRT5 levels reduced HSPD1 protein stability through desuccinylation modification. CONCLUSION: SIRT5-mediated desuccinylation of HSPD1 protects against hepatic steatosis in MAFLD model cells, suggesting that targeting SIRT5 and HSPD1 may represent a novel therapeutic strategy for preventing and treating MAFLD.