Diabetes 54:1108-1115, 2005
© 2005 by the American Diabetes Association, Inc.
Skeletal Muscle Lipid Accumulation in Type 2 Diabetes May Involve the Liver X Receptor Pathway
Eili T. Kase1,
Andreas J. Wensaas1,
Vigdis Aas1,
Kurt Højlund2,
Klaus Levin2,
G. Hege Thoresen1,
Henning Beck-Nielsen2,
Arild C. Rustan1, and
Michael Gaster2
1 Department of Pharmacology, School of Pharmacy, University of Oslo, Norway
2 KMEB (Clinic of Molecular Endocrinological Treatment), Department of Endocrinology, Odense University Hospital, Odense, Denmark
Liver X receptors (LXRs) are important regulators of cholesterol and lipid metabolism and are also involved in glucose metabolism. However, the functional role of LXRs in human skeletal muscle is at present unknown. This study demonstrates that chronic ligand activation of LXRs by a synthetic LXR agonist increases the uptake, distribution into complex cellular lipids, and oxidation of palmitate as well as the uptake and oxidation of glucose in cultured human skeletal muscle cells. Furthermore, the effect of the LXR agonist was additive to acute effects of insulin on palmitate uptake and metabolism. Consistently, activation of LXRs induced the expression of relevant genes: fatty acid translocase (CD36/FAT), glucose transporters (GLUT1 and -4), sterol regulatory elementbinding protein-1c, peroxisome proliferatoractivated receptor- , carnitine palmitoyltransferase-1, and uncoupling protein 2 and 3. Interestingly, in response to activation of LXRs, myotubes from patients with type 2 diabetes showed an elevated uptake and incorporation of palmitate into complex lipids but an absence of palmitate oxidation to CO2. These results provide evidence for a functional role of LXRs in both lipid and glucose metabolism and energy uncoupling in human myotubes. Furthermore, these data suggest that increased intramyocellular lipid content in type 2 diabetic patients may involve an altered response to activation of components in the LXR pathway.
Address correspondence and reprint requests to Arild Chr. Rustan, PhD, Department of Pharmacology, School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, N-0316 Oslo, Norway. E-mail: arild.rustan{at}farmasi.uio.no

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Copyright © 2005 by the American Diabetes Association.
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