Expression And Function Of Leptin And Leptin Receptor In Human Ovary

Objective: To detect the expression of leptin receptor on human luteinizing granulosa cells and the presence of leptin in human follicular fluid in order to explore if Ieptin has a direct action on human ovary, and to study the effects of leptin on steriodgenesis by granulosa cells and the serum leptin levels during menstrual cycle. Methods: 1. 35 healthy, regularly cycling women ( 27±4.4 years old, BMI=18.87± 4.25kg/m2) were evaluated. Morning blood samples were collected on day 2 and day 8 of spontaneous menstrual cycle, day 1 and day 6 after ovulation. 2. Human GCs were recovered from follicular aspirates obtained during transvaginal ultrasound-guided oocyte retrieval for in vitro fertilization- embryo transfer and were cultured for 3 days with M199 medium. 3. The expression of leptin receptor on cultured human granulosa cells was detected by immunocytochemistry technique under fluoroscopy. 4. The concentration of leptin in human follicular fluid and serum were measured by enzyme-labeled immunosordent assay (ELLSA). 5. The GCs were cultured with M199 medium with various concentration of leptin (0, 10, 30, 100, 300ng/ml), hMG (human menopausal hormone, 0, 0.1, 0.2, 0.5, 1, 2, 5, 1Oμg/ml), testosterone 100 μg/ml. The mediums were collected for estradiol and progesterone measurement. Results: 1. Circulating leptin showed significant changes in menstrual cycle. Serum leptin levels increased after ovulation (P<0.05), and on day 6 after ovulation were higher than day 1 after ovulation (P<0.05). 2. The green fluorescence was observed on the memberence and cytoplasm of human GC under fluoroscopy. 3. The leptin levels in the serum and follicular fluid were not significantly different, mean±SD 19.28±4.22 and 20.02±3.45ng/ml, respectiyely (P>0.05). The serum and follicular fluid levels were significantly correlated (correlation coefficient=0.713, P<0.01). 4. Addition of leptin did not alter basal estradiol and progesterone production (P>0.05). Leptin caused a dose-dependent inhibition of the FSH and LH-stimulated estradiol production (P<0.05). There was no effect of leptin on FSH and LH-stimulated progesterone production (P> 0.05). Conclusion 1. Serum leptin levels of women showed significant changes in spontaneous menstrual cycles. This strongly suggests a dynamic relationship between leptin and reproductive system. 2. Our study demonstrated that Ieptin receptor was expressed on human Iuteinizing granulosa cells, and leptin is present in human follicular fluid,which suggests leptin may have a direct effect on human ovary.3. The results demonstrate that leptin can directly inhibit FSH and LH-stimulated estradiol production by human luteinizing granulosa cells invitro, but has no effect on progeSterone production. These effects maycontribute to the conversion of ovary from follicular phase to lutealphase. Leptin may pIay an important role in follicular deveIopment andluteal establishmont.