LAUSR

A suitable additive for fish sperm storage in vitro is necessary for artificial reproduction. In this study, we evaluated the effects of different concentrations (100, 200, 400, and 800 µmol/L) of metformin (Met) on Schizthorax prenanti and Onychostoma macrolepis sperm under storage in vitro for 72 h. Compared with the control group, 400 µmol/L Met was more effective at improving the quality and fertilization capacity of Schizothorax prenanti sperm by increasing the adenosine triphosphate (ATP) content within the sperm. Further study found that metformin stabilized the ATP level by enhancing the glucose uptake in Schizothorax prenanti sperm, and this effect might be associated with the activation of AMP-activated protein kinase (AMPK) in sperm. In this study, we also found that the glucose could be absorbed by the sperm of Schizothorax prenanti, which was mainly accumulated in the midpiece of Schizothorax prenanti sperm, where mitochondria were located. In addition, Compound C(CC) significantly inhibited the beneficial effects of Met on the quality and glucose uptake capacity of Schizothorax prenanti sperm by inhibiting AMPK phosphorylation. These results revealed that AMPK played an important role in vitro sperm storage, and Met maintained ATP content, and increased the storage time of Schizothorax prenanti sperm in vitro for 72 h, possibly due to Met enhanced glucose uptake capacity of sperm by activating AMPK. Similarly, the beneficial effects of Met on Schizothorax prenanti sperm were also found in O. macrolepis sperm, suggesting that Met may hold great promise for the practice of storing fish in vitro.