Effect of TNF-Alpha on Caveolin-1 Expression and Insulin Signaling During Adipocyte Differentiation and in Mature Adipocytes

• Main Authors: Sara Palacios-Ortega, Maider Varela-Guruceaga, Miriam Algarabel, Fermín Ignacio Milagro, J. Alfredo Martínez, Carlos de Miguel
• Format: Article
• Language: English
• Published: Cell Physiol Biochem Press GmbH & Co KG 2015-07-01
• Series: Cellular Physiology and Biochemistry
• Subjects: Adipogenesis; Insulin receptor; Insulin-stimulated glucose uptake; DNA methylation; 3T3-L1; Inflammation
• Online Access: http://www.karger.com/Article/FullText/430314

Background/Aims: Tumor necrosis factor-α (TNF-α)-mediated chronic low-grade inflammation of adipose tissue is associated with obesity and insulin resistance. Caveolin-1 (Cav-1) is the central component of adipocyte caveolae and has an essential role in the regulation of insulin signaling. The effects of TNF-α on Cav-1 expression and insulin signaling during adipocyte differentiation and in mature adipocytes were studied. Methods: 3T3-L1 cells were differentiated (21 days) in the presence TNF-α (10 ng/mL) and mature adipocytes were also treated with TNF-α for 48 hours. Cav-1 and insulin receptor (IR) gene methylation were determined as well as Cav-1, IR, PKB/AKT-2 and Glut-4 expression and activation by real time RT-PCR and western blot. Baseline and insulin-induced glucose uptake was measured by the 2-[C14]-deoxyglucose uptake assay. Results: TNF-α slowed down the differentiation program, hindering the expression of some insulin signaling intermediates without fully eliminating insulin-mediated glucose uptake. In mature adipocytes, TNF-α did not compromise lipid-storage capacity, but downregulated the expression of the insulin signaling intermediates, totally blocking insulin-mediated glucose uptake. Insulin sensitivity correlated with the level of activated phospho-Cav-1 in both situations, strongly suggesting the direct contribution of Cav-1 to the maintenance of this physiological response. Conclusion: Cav-1 activation by phosphorylation seems to be essential for the maintenance of an active and insulin-sensitive glucose uptake.