The differential effect of food intake and beta-adrenergic stimulation on adipose-derived hormones and cytokines in man

We determined whether the physiologic changes that accompany food intake or sympathetic activation by beta-adrenergic stimulation result in alteration s in the secretion of leptin, tumor necrosis factor-cu (TNF alpha), or inte rleukin-6 (IL-6) by serially sampling sc abdominal adipose interstitial flu id by open-flow microperfusion before and after a standardized meal and in response to isoproterenol (1 mu mol/L) delivered locally. Post cibum IL-6 r ose up to 5-fold, whereas leptin and TNF alpha secretion did not change; TN F alpha, but not IL-6, correlated positively with indices of lipolysis. Iso proterenol-induced lipolysis was accompanied by a transient 40% reduction i n leptin and a parallel 85% elevation of TNF alpha concentration, whereas I L-6 levels did not change; again, TNF alpha correlated positively with lipo lysis. These data show that secretion of some, but not all, metabolically r elevant polypeptides by adipose tissue is modulated within a short time fra me by food or stress stimuli, suggesting a role of these peptides in local autocrine/paracrine or distant endocrine effects on fat metabolism TNF alph a's close correlation with lipolysis suggests that this cytokine participat es in a local positive autocrine feedback loop, potentiating lipolysis and inhibiting insulin's antilipolytic actions. The regulations of adipose lept in, TNF alpha, and IL-6 secretion seem distinct from each other and differe nt in the fed vs. fasting state.