Adiponectin gene expression and secretion is inhibited by interleukin-6 in 3T3-L1 adipocytes.
Recently, it has been shown that adiponectin is an important insulin-sensitizing fat-derived protein which is downregulated in insulin resistance and obesity, and replenishment of which improves insulin sensitivity. In contrast, interleukin (IL)-6 appears as an adipocytokine serum concentrations of which are elevated in these states. However, it has not been determined whether IL-6 might impact on expression and secretion of adiponectin. To clarify this, 3T3-L1 adipocytes were treated with different concentrations of IL-6 for various periods of time. Adiponectin mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction and secretion was determined by radioimmunoassays. Interestingly, treatment of 3T3-L1 cells with 30 ng/ml IL-6 significantly decreased adiponectin secretion to 75% of control levels. Adiponectin secretion was also inhibited between 25% and 45% by chronic treatment with forskolin (50 microM), tumor necrosis factor alpha (100 ng/ml), and dexamethasone (100 nM). Furthermore, adiponectin mRNA expression was downregulated by up to 50% in a time- and dose-dependent manner, with significant inhibition detectable at concentrations as low as 3 ng/ml IL-6 and as early as 8h after effector addition. The inhibitory effect of IL-6 was partially reversed by pretreatment of 3T3-L1 cells with pharmacological inhibitors of a p44/42 mitogen-activated protein (MAP) kinase. Moreover, the negative effect of IL-6 on adiponectin mRNA expression could be reversed by withdrawal of the hormone for 24h. Taken together, our results suggest that adiponectin gene expression is reversibly downregulated by IL-6 and support the concept of adiponectin being an important selectively controlled modulator of insulin sensitivity.
Fasshauer
Mathias
M
Department of Internal Medicine III, University of Leipzig, Ph.-Rosenthal-Str. 27, 04103, Leipzig, Germany.
Kralisch
Susan
S
Klier
Margit
M
Lossner
Ulrike
U
Bluher
Matthias
M
Klein
Johannes
J
Paschke
Ralf
R
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D052242:Adiponectin; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D007333:Insulin Resistance / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins; D015850:Interleukin-6 / Q000494:pharmacology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D052242:Adiponectin; D036341:Intercellular Signaling Peptides and Proteins; D015850:Interleukin-6; D011506:Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D003907:Dexamethasone; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases