[Changes of the circulating leptin levels and sexual development associated index in dietetic obese rats]

To observe the serum levels of leptin and estradiol, ovary development.

Dietetic obese model were established in female SD rats. Three groups were used: control group, obesity group (fat-enriched diet) and reducing group (fat-enriched diet for 6 weeks, then replaced by a normal diet), and were sacrificed at 0, 3, 6, 9, 12 and 15 weeks after the start of the experiment. We measured the serum levels of leptin and estradiol (E2) and observed ovary development by microscope.

Mean body weight of obese rats was over 21.4% than that of normal rats in the end of experiment. The serum E2 levels increased with age and they were higher in obese group than that in control group at same time point (but P > 0.05). The serum leptin levels in obese group were obviously higher than that in control and reducing group (P = 0.000), and they showed a positive correlation with body weight and serum E2 levels (r = 0.958 and 0.896, P = 0.010 and 0.039). There were more mature ovarian follicle and luteum in obese group, but development of them were bad than that of control and reducing group groups.

There were a tendency of ahead sexual maturation in female obese rats. Leptin probably play an important role in obesity and sexual maturation. This support that Leptin causes a female-specific facilitatory effect on GnRH pulse amplitude.