Insulin-induced cytokine production in macrophages causes insulin resistance in hepatocytes.
Overweight and obesity are associated with hyperinsulinemia, insulin resistance, and a low-grade inflammation. Although hyperinsulinemia is generally thought to result from an attempt of the β-cell to compensate for insulin resistance, there is evidence that hyperinsulinaemia itself may contribute to the development of insulin resistance and possibly the low-grade inflammation. To test this hypothesis, U937 macrophages were exposed to insulin. In these cells, insulin induced expression of the proinflammatory cytokines IL-1β, IL-8, CCL2, and OSM. The insulin-elicited induction of IL-1β was independent of the presence of endotoxin and most likely mediated by an insulin-dependent activation of NF-κB. Supernatants of the insulin-treated U937 macrophages rendered primary cultures of rat hepatocytes insulin resistant; they attenuated the insulin-dependent induction of glucokinase by 50%. The cytokines contained in the supernatants of insulin-treated U937 macrophages activated ERK1/2 and IKKβ, resulting in an inhibitory serine phosphorylation of the insulin receptor substrate. In addition, STAT3 was activated and SOCS3 induced, further contributing to the interruption of the insulin receptor signal chain in hepatocytes. These results indicate that hyperinsulinemia per se might contribute to the low-grade inflammation prevailing in overweight and obese patients and thereby promote the development of insulin resistance particularly in the liver, because the insulin concentration in the portal circulation is much higher than in all other tissues.
University of Potsdam, Institute of Nutritional Science, Nutritional Biochemistry, Nuthetal, Germany; jhenkel@uni-potsdam.de.
Julia
J
Manowsky
University of Potsdam, Institute of Nutritional Science, Nutritional Biochemistry, Nuthetal, Germany; Cancer Metabolism Research Group, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil; and.
Rodolfo Gonzalez
RG
Camargo
German Institute for Human Nutrition, Nuthetal, Germany.
Anna P
AP
Kipp
University of Potsdam, Institute of Nutritional Science, Nutritional Biochemistry, Nuthetal, Germany;
Janin
J
Henkel
University of Potsdam, Institute of Nutritional Science, Nutritional Biochemistry, Nuthetal, Germany;
Gerhard P
GP
Püschel
D000818:Animals; D002450:Cell Communication / Q000276:immunology*; D002460:Cell Line; D016207:Cytokines / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D022781:Hepatocytes / Q000276:immunology*; D007328:Insulin / Q000008:administration & dosage / Q000276:immunology*; D007333:Insulin Resistance / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D016207:Cytokines; D007328:Insulin
cytokines; inflammation; insulin; macrophage; metabolic syndrome; type 2 diabetes