Effect of EGB on pituitary-testicular axis and expressions of LHR and StAR in type II diabetic rats

AIM: To observe the effect of the extract of Ginkgo biloba(EGB) on pituitary-testicular axis and the mRNA expressions of luteinizing hormone receptor (LHR) and steroidogenic acute regulatory protein (StAR). METHODS: Thirty male Sprague-Dauley rats were divided into three groups randomly: normal control group, type II diabetic group and EGB treatment group. After fed with high-fat diet for 4 weeks, the later two groups were injected with strepozotocin intraperitoneally to induce type II diabetes mellitus. The EGB treatment group was given EGB at the dose of 50 mg/kg once a day for 12 weeks by intragastric administration. The normal control and diabetic group were given normal saline of equal volume per day for 12 weeks. The indices of blood glucose, insulin and low-density lipoprotein-cholesterol (LDL-c) were measured. The morphologic change of testicular tissue was observed under light microscopy (LM) and transmission electron microscopy (TEM) respectively. The concentrations of blood luteinizing hormone (LH) and testosterone (T) were assayed by the technique of enzyme linked immunosorbent assay (ELISA). The mRNA expressions of LHR and StAR from Leydig cells were detected by RT-PCR. RESULTS: The concentrations of blood glucose, insulin and LDL-c increased obviously, and the testis weights lessened obviously in type II diabetic groups compared to those in normal control groups. Rare spermatogenic cells of seminiferous tubule and germinal arrest were observed in diabetic group under LM. Ultrastructural analysis of testicular tissue by TEM showed dilation of the endoplasmic reticulum and mitochondrial swelling in Leydig cell and sertoli cell in diabetic group. The level of blood LH and T decreased in type II diabetic groups in comparison with that in the normal control group. Compared to normal groups, the mRNA expression of StAR in type II diabetic groups decreased, while the mRNA expression of LHR increased. After the treatment of EGB, the pathological change of testis was relieved, the concentrations of blood glucose, insulin and LDL-c were decreased, the level of blood LH and T, and the mRNA expression of StAR were increased, and the mRNA expression of LHR descended compared to type II diabetic groups. CONCLUSION: EGB may increase the LH-induced testosterone production by correcting metabolic disorder of glucose and lipid, improving the function of pituitary-testicular axis and regulating the expression of LHR and StAR mRNA.