Protocatechuic acid promotes lactate synthesis in Sertoli cells of Tibetan sheep through AMPK/mTOR-mediated autophagy

OBJECTIVE: This study aimed to investigate the effects of protocatechuic acid (PCA) on Sertoli cells (SCs) in Tibetan sheep, focusing on its impact on cell proliferation, lactate synthesis, and the underlying molecular mechanisms. METHODS: Primary SCs were isolated from the testes of Tibetan sheep and subsequently cultured. The effects of PCA on the functionality of SCs were evaluated through in vitro experiments, with an additional investigation into its molecular mechanisms. In vivo and in vitro mouse models were employed to validate the regulatory mechanisms of PCA on male reproductive function and SCs. RESULTS: PCA significantly upregulated the expression of proliferation and lactate synthesis- related genes in Tibetan sheep SCs, and increased the intracellular levels of pyruvate and lactate. Mechanistically, PCA activated the AMP-activated protein kinase (AMPK) pathway and inhibited the mechanistic target of rapamycin (mTOR) pathway, leading to the induction of autophagy in SCs. The use of autophagy inhibitors and AMPK inhibitors effectively blocked PCA-induced promotion of SCs proliferation and lactate synthesis. In mouse model studies, PCA demonstrated enhancements in sperm count, pregnancy rates, and litter size, while reduction in the rate of sperm abnormality. It also elevated activin A levels and decreased inhibin B levels in testicular tissues, increased serum follicle-stimulating hormone, luteinizing hormone, and testosterone levels, enhanced testicular antioxidant enzyme activities, and reduced malondialdehyde content. Furthermore, PCA upregulated the expression of proteins associated with proliferation and lactate synthesis in mouse testicular tissues and primary SCs, modulated the AMPK/mTOR pathway, and increased autophagic activity. CONCLUSION: PCA promotes proliferation and lactate synthesis in SCs of Tibetan sheep through AMPK/mTOR-mediated autophagy.