Abstract
Glucagon-like peptide-1 (GLP-1) is a peptide hormone involved in regulating insulin secretion and energy metabolism. It typically needs to bind to Glucagon-like peptide-1 Receptor (GLP-1R) in the body to exert its regulatory effects. Exenatide-4 (EX-4) is a synthetic GLP-1 analogue that is widely used as a weight loss and blood sugar-lowering medication due to its high stability and slow degradation rate. Since there is no current research on whether GLP-1 affects energy metabolism and sperm motility, it is necessary thatthe effects of GLP-1 analogues on sperm motility and energy metabolism will be investigated by treating sheep sperm with EX-4. Our results showed that GLP-1R was present in sheep sperm, and expressed in the head of the sperm. After concentration screening, it was found that 300 pM EX-4 was most effective for improving sheep sperm motility. Incubating sperm with EX-4 resulted in a significant increase in LDH, G6PDH, lipase activity, and ATP content (P < 0.05), while triglyceride content significantly decreased (P < 0.05). Additionally, EX-4 significantly promoted insulin secretion in sheep sperm (P < 0.05). When EX-4 was used in combination with GLP-1R inhibitor (GLP-1R AB), the levels of LDH, G6PDH, lipase activity, ATP content, and insulin concentration significantly decreased (P < 0.05), while triglyceride content significantly increased (P < 0.05). The further results showed that EX-4 effectively promoted cholesterol efflux in sheep sperm (P < 0.05), which is beneficial for sperm energy acquisition and maturation. Both insulin receptor inhibitors (IR AB) and GLP-1R AB reduced the promoting effect of EX-4 on cholesterol efflux in sheep sperm (P < 0.05). Our other results revealed that EX-4 regulates sperm metabolism through the GLP-1R/PI3K/Akt pathway, enhancing energy levels in sheep sperm. Generally, sperm motility is closely related to metabolic levels, and it is believed that EX-4 enhances the activity of some metabolic enzymes in sheep sperm by activating this signaling pathway, thereby promoting energy acquisition, maturation, and significantly improving sperm motility.