Differential response of UCP3 to medium versus long chain triacylglycerols; manifestation of a functional adaptation

Differential response of UCP3 to medium versus long chain triacylglycerols; manifestation of a functional adaptation.Hoeks J, Hesselink MK, van Bilsen M, Schaart G, van der Vusse GJ, Saris WH, Schrauwen P.Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. j.hoeks@hb.unimaas.nlWe compared UCP3 protein in rat cardiac, glycolytic and oxidative skeletal muscle and examined the effect of high-fat medium chain vs. long chain triacylglycerol feeding on UCP3 content in these tissues. Cardiac muscle displays the lowest basal levels of UCP3 protein. Increasing long chain - but not medium chain - fatty acid supply upregulates UCP3 in all muscles. Since plasma non-esterified fatty acids and the expression of two peroxisome proliferator-activated receptor (PPAR)-responsive genes, were not different between groups, we conclude that the differential upregulation of UCP3 is not merely PPAR-mediated. This study supports a role of UCP3 in export of non-metabolizable fatty acids.