Adiponectin is secreted by theca layer cells isolated from chicken ovarian follicles

Abstract

Adiponectin, an adipokine hormone, influences glucose utilization, insulin sensitivity and energy homeostasis by signaling through two distinct receptors, ADIPOR1 and ADIPOR2. We previously reported that adiponectin and its receptors are expressed in several organs, including testes in chicken. We report herein that adiponectin gene is expressed exclusively in theca layer while ADIPOR1 and ADIPOR2 genes are expressed in granulosa and theca layers of all preovulatory and prehierarchical follicles of the chicken ovary. Estradiol and/or progesterone treatment of sexually immature chickens significantly altered expression of adiponectin and ADIPOR1 in the ovary. Using anti-chicken adiponectin-, ADIPOR1-, or ADIPOR2- antibodies, adiponectin-immunoreactive (ir) cells were found exclusively in the theca layer, and ADIPOR1-ir and ADIPOR2-ir cells were found both in theca and granulosa layers. Theca layer cells dispersed from preovulatory and prehierarchical follicles were found to synthesize and secrete a 720 kDa heavy molecular weight (HMW) isoform of adiponectin in vitro. Recombinant chicken adiponectin (rcADN) expressed in eukaryotic cells under serum-free conditions comprised primarily of the HMW isoform. Treatment of granulosa cells dispersed from 9 to 12 mm preovulatory follicle and 6 to 8 mm prehierarchical follicle with rcADN or an adiponectin receptor agonist, adipoRon, increased pERK and pACC abundance. In addition, both rcADN and adipoRon were found to significantly decrease the expression of steroidogenic acute regulatory protein gene expression in granulosa cells of preovulatory and prehierarchical follicles. In conclusion, adiponectin secreted by theca cell layer is identical in mass to circulating adiponectin. Systemic and/or theca-derived adiponectin is likely to affect proliferation, metabolism, and steroidogenesis of ovarian follicular cells.