Cytokine release from adipose tissue of nonobese individuals

Explants of human adipose tissue from nonobese subjects were cultured for 24 h with or without the presence of 20 ng/ml TNFalpha. Gene expression and/or medium concentrations of interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1 RA), TNFalpha, IL-6, IL-8, resistin, PAI-1 and leptin were analysed. TNFalpha increased the mRNA levels of TNFalpha itself as well as IL-6, IL-8, IL-1beta and PAI-1, but not leptin. The medium concentrations of IL-1 RA, IL-6 and IL-8 were markedly increased by TNFalpha while no measurable release of TNFalpha, resistin or IL-1beta to the medium was found. Thus, human adipose tissue from nonobese individuals releases substantial amounts of IL-6, IL-8 and IL-1 RA and the gene expression of these cytokines, like that of IL-1beta and PAI-1, is regulated by TNFalpha. However, since neither TNFalpha, resistin or IL-1beta was found in the culture medium, such a regulatory effect by TNFalpha on adipose tissue in vivo is likely to be mediated through a paracrine mechanism where invaded inflammatory cells may play a critical role.