Role of leptin and the leptin receptor in the pathogenesis of varicocele-induced testicular dysfunction

The present study investigated the expression of leptin and its receptor in the left testis and hypothalamus of rats with varicocele and clarified their roles in the pathogenesis of varicocele-induced testicular dysfunction. A total of 40 male rats were divided randomly into four groups. Groups 1 (G1) and 3 (G3) underwent a sham operation. Groups 2 (G2) and 4 (G4) underwent operations to form a varicocele created by partial ligation of the left renal vein. G1 and G2 rats were euthanized 4 weeks after the operation while G3 and G4 rats were euthanized at 8 weeks. The expression of leptin and its receptor was analyzed by immunohistochemistry. The mRNA levels of leptin, its receptor, kisspeptin (KiSS-1), G-protein coupled receptor 54 (GPR54), gonadotropin releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured by reverse transcription-quantitative polymerase chain reaction. Testicular spermatogenesis function and gonadal hormone levels were measured. Compared with G1 and G3, the expression of leptin and its receptor in rat testis was significantly higher in G2 and G4, respectively. Leptin expression was inversely associated with the number of sperm in the left epididymis, thickness of the seminiferous epithelium and the diameter of seminiferous tubules. The expression of leptin receptors in the hypothalamus of G2 and G4 was significantly increased compared with that in G1 and G3, respectively. The mRNA levels of KiSS-1, GPR54, GnRH, LH and FSH in G2 and G4 were significantly increased compared with that in G1 and G3, respectively. Serum testosterone levels in G2 and G4 rats were significantly lower than those in G1 and G3 rats, respectively. There was no significant difference between the serum levels of FSH, LH and leptin. These results suggest that leptin and its receptor may serve significant roles in the pathogenesis of varicocele-induced testicular dysfunction.