L26/P-318 Ectopic endometrium–derived lactate induces ECHS1 lactylation and impairs oocyte quality in ovarian endometriosis

Abstract Study question Does the metabolic interaction between ectopic lesions and the ovarian microenvironment drive oocyte impairment and infertility in endometriosis? Summary answer Ectopic endometrium–derived lactate induces ECHS1 K43 lactylation in granulosa cells, disrupting ATP synthase assembly and impairing oocyte quality. What is known already Ovarian endometriosis is the predominant subtype of endometriosis, affecting over 40% of patients and significantly disrupting ovarian function. Emerging evidence suggests that ectopic endometrial tissues undergo Warburg-like metabolic reprogramming, leading to lactate accumulation, yet the pathogenic impact of ectopic endometrium-derived lactate on ovarian tissue remains unclear. Study design, size, duration Spatial multi-omics was employed to delineate cross-tissue lactate diffusion within the endometriosis microenvironment. Mechanistic investigations focused on lactate-induced protein lactylation and ATP synthase assembly. The physiological impact of the lactate-enriched microenvironment on oocyte competence and overall fertility was further validated using a combination of mice and gene-knockout zebrafish. Participants/materials, setting, methods Integration of spatial transcriptomics and metabolomics revealed cross-tissue lactate diffusion in endometriosis. Molecular interactions were validated via co-immunoprecipitation, GST pull-down, and microscale thermophoresis. Mitochondrial complex assembly and cellular metabolism were analyzed by blue native polyacrylamide gel electrophoresis and Seahorse assays. Lactylated proteins were identified by mass spectrometry. Oocyte quality was assessed through mitochondrial membrane potential and spindle morphology in mouse and gene-knockout zebrafish models. Main results and the role of chance We combined single-nucleus and spatial transcriptomics with spatial metabolomics to map lactate distribution in ovarian endometriosis and found that lactate diffuses from ectopic endometrial lesions into adjacent ovarian tissue down its concentration gradient. In vivo, exogenous or ovarian endometriosis-induced lactate accumulation impaired oocyte quality in zebrafish and mice by disrupting follicle maturation, reducing mitochondrial membrane potential, and disrupting spindle morphology. These defects were partially restored by deficiency of lactate dehydrogenase A or alanyl-tRNA synthetase 1 (aars1). Mechanistically, lactate induced enoyl-coenzyme A hydratase, short chain 1 (ECHS1) lactylation at K43 in granulosa cells, which sequesters ATP synthase membrane subunit J (ATP5MJ), disrupting ATP synthase assembly, and impairing mitochondrial function. Moreover, β-alanine, serving as an antagonist of AARS1, effectively limited ECHS1 lactylation and rescued oocyte competence. Limitations, reasons for caution While β-alanine shows promise in animal models, the clinical safety and efficacy for improving human oocyte quality require further validation through controlled trials. Wider implications of the findings This study identifies protein lactylation as a novel link between metabolic reprogramming and oocyte quality in endometriosis. The findings highlight ECHS1 as a key metabolic rheostat and suggest that targeting the AARS1–ECHS1–ATP5MJ axis, through β-alanine supplementation, offers a potential therapeutic strategy for infertility. Trial registration number No