The crosstalks between adipocytes and other endocrine cells.

Abstract

Adipocytes were traditionally thought as a passive depot of energy (fat). It has recently been recognized that adipocytes are pivotal endocrine cells secreting a spectrum of important hormones called adipokines, including leptin, resistin and neuropeptide-Y (NPY). Adipokines are relevant to various common diseases such as obesity, diabetes, and cardiovascular disorders.

Metabolism is regulated by the collaborative actions of several types of endocrine cells including adipokine secreting adipocytes, insulin secreting pancreatic beta cells, catecholamine secreting chromaffin cell in adrenal gland. In this study, we investigate the crosstalks and regulatory mechanism that leptin and resistin has on catecholamines and the chromaffin cells in adrenal glands, and their feedback reactions upon themselves. We found catecholamines directly suppress endogenous leptin and resistin secretion in adipocytes through α adrenergic receptor, and the decreased leptin and resistin has a reduced effect of stimulating catecholamines – a negative feedback loop. Leptin, as well as resistin regulation of catecholamines was found to be dependent on multiple pathways. Preliminary results showing NPY – a newly found adipocyte-secreted cytokine- and its effects regulating other adipokines secreted was also presented. In this study, we focus mainly on adipokines in terms of cellular and hormonal secretions, vesicular trafficking, intracellular localization, signals transduction, and interactions with various secretory factors. Studies of adipokines’ secretion and their crosstalks may lead to new insights into energy metabolism and metabolic homeostasis. The study offers the hope of finding new therapies and treatments for metabolic disorders such as obesity and diabetes.