Food restriction regulates adipose-specific cytokines in pituitary gland but not in hypothalamus.

ABSTRACT

White adipose tissue is now recognized as the source of a growing list of novel adipocyte-specific factors, or adipokines. These factors regulate energy homeostasis, including the response to food deprivation. We hypothesized that the brain and pituitary gland would also express adipokines and their regulatory factors and subsequently demonstrated that the rodent brain-pituitary system expresses mRNA and protein for leptin and resistin. We now report that the adipokines FIAF and adiponutrin, as well as the nuclear hormone receptor PPAR gamma, are expressed in pituitary, brain and adipose tissue. In pituitary gland, 24 h of food restriction reduced PPAR gamma expression by 54% whereas both adiponutrin and FIAF were increased 1.7 and 2.3 fold, respectively. These changes in expression were similar to those observed in fat, except for adiponutrin, which by contrast is dramatically reduced 95% by fasting. Furthermore, whereas PPAR gamma 2 is the main isoform affected by fasting in adipose tissue, our data suggest that only PPAR gamma 1 is present and downregulated by fasting in pituitary tissue. In contrast to the sensitivity of pituitary tissue to the effects of fasting, no significant change in expression was observed in basal hypothalamus for any of the genes studied. Overall, our data suggest that pituitary-derived adipokines may play an unexpected role in the neuroendocrine regulation of energy homeostasis.