Peroxisome Proliferator-Activated Receptor-α Regulates Fatty Acid Utilization in Primary Human Skeletal Muscle Cells

Peroxisome Proliferator-Activated Receptor-α Regulates Fatty Acid Utilization in Primary Human Skeletal Muscle Cells Deborah M. Muoio 1 2 , James M. Way 3 , Charles J. Tanner 2 , Deborah A. Winegar 3 , Steven A. Kliewer 3 , Joseph A. Houmard 2 , William E. Kraus 1 and G. Lynis Dohm 2 1 Department of Medicine and Cell Biology, Duke University Medical Center, Durham, North Carolina 2 Department of Biochemistry and the Human Performance Laboratory, East Carolina University, Greenville, North Carolina 3 Departments of Molecular Endocrinology and Metabolic Diseases, GlaxoSmithKline, Research Triangle Park, North Carolina Abstract In humans, skeletal muscle is a major site of peroxisome proliferator–activated receptor-α (PPAR-α) expression, but its function in this tissue is unclear. We investigated the role of hPPAR-α in regulating muscle lipid utilization by studying the effects of a highly selective PPAR-α agonist, GW7647, on [ 14 C]oleate metabolism and gene expression in primary human skeletal muscle cells. Robust induction of PPAR-α protein expression occurred during muscle cell differentiation and corresponded with differentiation-dependent increases in oleate oxidation. In mature myotubes, 48-h treatment with 10–1,000 nmol/l GW7647 increased oleate oxidation dose-dependently, up to threefold. Additionally, GW7647 decreased oleate esterification into myotube triacylglycerol (TAG), up to 45%. This effect was not abolished by etomoxir, a potent inhibitor of β-oxidation, indicating that PPAR-α–mediated TAG depletion does not depend on reciprocal changes in fatty acid catabolism. Consistent with its metabolic actions, GW7647 induced mRNA expression of mitochondrial enzymes that promote fatty acid catabolism; carnitine palmityltransferase 1 and malonyl-CoA decarboxylase increased ∼2-fold, whereas pyruvate dehydrogenase kinase 4 increased 45-fold. Expression of several genes that regulate glycerolipid synthesis was not changed by GW7647 treatment, implicating involvement of other targets to explain the TAG-depleting effect of the compound. These results demonstrate a role for hPPAR-α in regulating muscle lipid homeostasis. Footnotes Address correspondence and reprint requests to Deborah M. Muoio, P.O. Box 3327, Duke University Medical Center, Durham, NC 27710. E-mail: muoio{at}duke.edu . Received for publication 22 August 2001 and accepted in revised form 4 January 2002. D.M.M. has received funding from GlaxoSmithKline to support studies focused on developing n