1. College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, China 2. College of Life Sciences, TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, China
Abstract Text: Macroautophagy, also known as autophagy, serves as a critical cellular and energy regulatory mechanism, contributing to the preservation of primordial follicles, germ cell viability, and counteracting ovarian aging. However, it remains unclear whether autophagy in granulosa cells influences oocyte maturation. Our study demonstrates a noticeable decrease in autophagy levels in human granulosa cells obtained from older women, suggesting a potential inverse relationship between autophagy levels and oocyte quality. Through the establishment of a co-culture system, we observed that either pharmacological inhibition or genetic knockout of autophagy in granulosa cells detrimentally impacts oocyte quality and fertilization potential. Metabolomics analysis further revealed that the deleterious effects of autophagy deficiency on oocyte quality are mediated by reduced citrate levels, with exogenous citrate supplementation significantly enhancing oocyte maturation. Mechanistically, we identified ATP citrate lyase (ACLY), a key enzyme involved in citrate cleavage, as preferentially targeted for selective autophagic degradation via its association with K63-linked ubiquitin chains and recognition by the autophagy receptor protein SQSTM1/p62. In human follicles, autophagy levels in granulosa cells decline with maternal aging, concomitant with decreased citrate levels in the follicular fluid, suggesting a potential link between citrate metabolism and oocyte quality. Furthermore, elevated citrate levels in porcine follicular fluid promote oocyte maturation. Taken together, our findings elucidate the role of autophagy in granulosa cells in maintaining optimal citrate levels during oocyte maturation, highlighting its importance as a protective mechanism for reproductive health.
