Adipokines (Leptin, Adiponectin, Resistin) Differentially Regulate All Hormonal Cell Types in Primary Anterior Pituitary Cell Cultures from Two Primate Species

Adipose-tissue (AT) is an endocrine organ that dynamically secretes multiple hormones, the adipokines, which regulate key physiological processes. However, adipokines and their receptors are also expressed and regulated in other tissues, including the pituitary, suggesting that locally- and AT-produced adipokines might comprise a regulatory circuit that relevantly modulate pituitary cell-function. Here, we used primary pituitary cell-cultures from two normal nonhuman-primate species [Papio-anubis/Macaca-fascicularis] to determine the impact of different adipokines on the functioning of all anterior-pituitary cell-types. Leptin and resistin stimulated GH-release, a response that was blocked by somatostatin. Conversely, adiponectin decreased GH-release, and inhibited GHRH-, but not ghrelin-stimulated GH-secretion. Furthermore: 1) Leptin stimulated PRL/ACTH/FSH- but not LH/TSH-release; 2) adiponectin stimulated PRL-, inhibited ACTH- and did not alter LH/FSH/TSH-release; and 3) resistin increased ACTH-release and did not alter PRL/LH/FSH/TSH-secretion. These effects were mediated through the activation of common (AC/PKA) and distinct (PLC/PKC, intra-/extra-cellular calcium, PI3K/MAPK/mTOR) signaling-pathways, and by the gene-expression regulation of key receptors/transcriptional-factors involved in the functioning of these pituitary cell-types (e.g. GHRH/ghrelin/somatostatin/insulin/IGF-I-receptors/Pit-1). Finally, we found that primate pituitaries expressed leptin/adiponectin/resistin. Altogether, these and previous data suggest that local-production of adipokines/receptors, in conjunction with circulating adipokine-levels, might comprise a relevant regulatory circuit that contribute to the fine-regulation of pituitary functions.