Dietary supplementation with metformin improves testis function and semen quality and increases antioxidants and autophagy capacity in goats.

ATP is essential for mammalian sperm to maintain fertilizing capacity. Metformin (Met) can activate 5'-AMP-activated protein kinase (AMPK) to maintain energy homeostasis. Thus, the aim of the present study was to investigate whether Met can improve testis function, semen quality, antioxidant and autophagy capacity through AMPK mediation of energy metabolism in goats. Twelve adult goats were randomly divided into three dietary treatments. All goats were fed a basal diet for 3 weeks and then assigned to a Met supplementation diet containing 0, 150, or 300 mg/kg for 8 weeks. The results showed that sperm viability, sperm membranal functional integrity, and acrosome integrity increased (P < 0.05) relative to the other treatments in the 300 mg/kg Met group. Growth hormone (GH) and insulin-like growth factor (IGF-1) in the 300 mg/kg Met group significantly decreased (P < 0.05) relative to the control group. Estrogen levels (E) in the 300 mg/kg Met group remarkably improved (P < 0.05) compared with the control group. The activities of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GSH-px), and superoxide dismutase (SOD) significantly increased (P < 0.05) in the 300 mg/kg Met group relative to the control group. A significant increase in AMPK and p-AMPK protein expression in the 300 mg/kg Met group was observed relative to the control group (P < 0.05). Belicin-1 and LC3II/I protein expression was significantly increased by adding Met to the diet (P < 0.05) and reached a maximum in the 300 mg/kg Met group. In addition, differentially expressed genes (DEGs) of goat testis were confirmed by RNA-seq. GO enrichment analysis revealed that DEGs were enriched in testicular metabolism and sperm development-related functional pathways. Overall, the results indicate that Met may play an important role in the regulation of testis function, semen quality, antioxidant, and autophagy capacity. These findings will help elucidate the role of Met in goat testis development.