Superactive human leptin antagonist reverses leptin-induced excessive progesterone and testosterone secretion in porcine ovarian follicles by blocking leptin receptors

Abstract

Accumulating evidence indicates that leptin plays an important role in controlling reproductive function. At physiological levels, leptin stimulates steroidogenesis and follicle maturation, whereas supraphysiological concentrations of leptin have been suggested to be an independent risk factor for cyst formation. Since the discovery of the link between leptin and obesity, which is frequently associated with polycystic ovarian syndrome (PCOS), a number of leptin mutants exhibiting antagonistic properties have been developed, opening new avenues for leptin-related research. Here, using a superactive human leptin antagonist (SHLA), we sought to determine whether blocking leptin receptors can reverse the actions of leptin in ovarian follicles. Antral porcine ovarian follicles, collected from prepubertal and mature animals, were exposed to 100, 250 and 500 ng/ml SHLA for 24 hours, after which leptin receptor (ObR), leptin, CYP11A1 and 17β-hydroxysteroid dehydrogenase (17β-HSD) levels in follicles were evaluated by Western blotting. Levels of secreted leptin, progesterone (P4), and testosterone (T) in the follicle incubation medium were measured using enzyme-linked immunosorbent assays. The effects of SHLA on leptin-stimulated P4 and T secretion were also tested by exposing follicles to 40 ng/ml leptin in the presence and absence of SHLA. These experiments revealed that SHLA acted through inhibition of ObR expression and leptin expression and secretion decreased P4 and T secretion by ovarian follicles from both prepubertal and mature animals. Our data further suggest that the mechanism underlying this action of SHLA involves inhibition of CYP11A1 and 17β-HSD protein expression. Importantly, SHLA reversed leptin-induced increases in P4 and T secretion. Collectively, these data indicate that, in addition to their potential application in novel therapeutic strategies in oncology, which has received considerable recent research attention, leptin receptors antagonists might also be beneficial in controlling reproduction.