Effects of eicosapentaenoic acid and docosahexaenoic acid on uncoupling protein 3 gene expression in C(2)C(12) muscle cells.

Uncoupling protein 3 (UCP3) is a mitochondrial membrane transporter that is expressed mainly in skeletal muscle where it plays an important role in energy expenditure and fat oxidation. In this study, we investigated the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on UCP3 gene expression in C(2)C(12) muscle cells. EPA and DHA up-regulated UCP3 mRNA level in a dose-dependent manner and similarly increased UCP3 promoter activity in C(2)C(12) muscle cells. To determine whether AMP-activated protein kinase (AMPK) signaling may also directly regulate UCP3 expression, 5'-amino-4-imidazolecarboxamide-ribonucleoside (AICAR), an AMP analog that activates AMPK, was treated in C(2)C(12) muscle cells. AICAR showed additive effects with EPA or DHA on the UCP3 promoter activation. These results indicate that EPA and DHA directly regulate the gene expression of UCP3, potentially through AMPK-mediated pathway in C(2)C(12) muscle cells.