Insulin stimulates interleukin-6 expression and release in LS14 human adipocytes through multiple signaling pathways

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Abstract

IL-6 is an important cytokine that regulates both immune and metabolic functions. Within adipose tissue, preadipocytes produce significant amounts of IL-6, but little is known about the factors or mechanisms that regulate IL-6 production in these cells. Using LS14, a newly developed human adipocyte cell line, our objective was to determine the mechanisms by which insulin stimulates IL-6 production and release in preadipocytes. Insulin increased IL-6 gene expression and secretion in a time- and dose-dependent manner. Insulin decreased cyclic AMP (cAMP) but increased cyclic GMP (cGMP) levels, and IL-6 expression/release was stimulated by a cGMP analog. The stimulatory effect of insulin and cGMP was abrogated by a specific inhibitor of protein kinase G (cyclic GMP-dependent protein kinase). Both insulin and cGMP rapidly induced phosphorylation of cAMP response element binding protein. Insulin also activated the MAPK signaling pathway, and its blockade prevented the insulin-stimulated increases in IL-6 cell content and release, but not IL-6 gene expression. Although inhibition of the proteosome increased IL-6 cell content and release, proteosome activity was unaffected by insulin. These data suggest that the stimulatory effects of insulin on IL-6 release involve several interrelated components: transcription, intracellular releasable pool, and secretion, which are differentially regulated and, thus, determine the size of the releasable pool of IL-6. Insulin-induced IL-6 gene expression is mediated by cGMP/cyclic GMP-dependent protein kinase/cAMP response element binding protein, whereas MAPK is involved in the insulin-stimulated IL-6 synthesis/release. Copyright © 2008 by The Endocrine Society.

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LaPensee, C. R., Hugo, E. R., & Ben-Jonathan, N. (2008). Insulin stimulates interleukin-6 expression and release in LS14 human adipocytes through multiple signaling pathways. Endocrinology, 149(11), 5415–5422. https://doi.org/10.1210/en.2008-0549

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