Endocrine Abstracts

Resistin is a recently discovered 12.5 kDa cysteine-rich secreted polypeptide first reported from rodent adipocytes and plays important role in the development of insulin resistance and obesity. Recently, many investigators have linked resistin to reproductive function. Resistin expression was observed in bovine and rat ovaries and showed that resistin modulate granulosa cells function such as steroidogenesis and proliferation, in basal state or in response to IGF-I in vitro. Our previous study showed that resistin was present in porcine small, medium and large follicles in prepubertal and normal estrous cycling animals. Additionally, resistin could modulate ovarian steroid synthesis by increasing androgen production. Porcine ovaries were collected from normal oestrus cycling crossbred gilts (6–8 months of age; Large White and Polish Landrace) at a local abattoir. Small (2–4 mm; SFs, n=6) and medium (4–6 mm; MFs, n=6) follicles collected at days 4–6 and 10–12 respectively. Ovarian follicles were cultured in the presence or absence of resistin (at doses 0.1, 1 and 10) and LH (100 ng/ml) or FSH (100 ng/ml) in M199 medium. After 24 h, conditioned culture media were collected for steroid hormone secretion (progesterone-P4, androstendione-A4, testosterone-T, and oestradiol-E2) by enzyme immunoassay (EIA) but ovarian follicles were homogenized to measurement expression of steroid enzymes (3β-HSD, CYP17, 17β-HSD, and CYP19) by western immunoblot. Statistical analyses were performed using GraphPad Prism 5 software. Data were analyzed using a one-way analysis of variance (ANOVA) test, followed by Tukey’s honestly significant difference (HSD) test. We observed that resistin increased stimulated LH and FSH P4, and A4 secretion by up-regulating the steady state levels of CYP11A1, 3β-HSD and CYP17A1, and 17β-HSD and had no effects on E2 secretion and CYP19A1 expression in ovarian follicles. Direct effects of resistin on steroidogenesis suggest that resistin is a new regulator of ovary function in animals during estrous cycle.