The SIRT5-SUCLG2 desuccinylation axis delays ovarian aging via a mitochondrial-epigenetic regulatory mechanism

Mitochondrial dysfunction and epigenetic alterations play critical roles in aging-related diseases, yet the molecular mechanisms linking mito-nuclear crosstalk to ovarian aging remain poorly understood. Here, single-cell transcriptome analysis of aging ovaries revealed senescence-associated hallmark alterations, including abnormally elevated mitochondrial metabolism, disrupted histone modification patterns, and enrichment of the senescence-associated secretory phenotype (SASP). We demonstrated that impaired SIRT5-mediated desuccinylation constitutes a key driver of ovarian aging. Mechanistically, we identified succinyl-coenzyme A (CoA) synthetase GDP-forming subunit β (SUCLG2) in the tricarboxylic acid (TCA) cycle as the main target of SIRT5-mediated desuccinylation. SUCLG2 desuccinylation at lysine residues K93 and K101 enhanced its protein stability and activity, thereby improving mitochondrial function upon cellular senescence. However, SUCLG2 hypersuccinylation specifically increased H4K8ac through acetyl-CoA accumulation in nucleus, leading to the overexpression of metabolism-related genes to compensate for the energy demand deficiency caused by decreased mitochondrial function during cellular senescence. In vivo functional studies demonstrated that acetyl-CoA oversupply accelerated ovarian aging, whereas ovarian gene therapy employing a SUCLG2 desuccinylation mutant ameliorated this condition. This study illuminates the molecular mechanisms underlying ovarian aging and identifies the SIRT5-SUCLG2 axis as a promising therapeutic target for age-related ovarian dysfunction.