Inhibition of glycogen synthesis by fatty acid in C(2)C(12) muscle cells is independent of PKC-alpha, -epsilon, and -theta.
We have previously shown that glycogen synthesis is reduced in lipid-treated C(2)C(12) skeletal muscle myotubes and that this is independent of changes in glucose uptake. Here, we tested whether mitochondrial metabolism of these lipids is necessary for this inhibition and whether the activation of specific protein kinase C (PKC) isoforms is involved. C(2)C(12) myotubes were pretreated with fatty acids and subsequently stimulated with insulin for the determination of glycogen synthesis. The carnitine palmitoyltransferase-1 inhibitor etomoxir, an inhibitor of beta-oxidation of acyl-CoA, did not protect against the inhibition of glycogen synthesis caused by the unsaturated fatty acid oleate. In addition, although oleate caused translocation, indicating activation, of individual PKC isoforms, inhibition of PKC by pharmacological agents or adenovirus-mediated overexpression of dominant negative PKC-alpha, -epsilon, or -theta mutants was unable to prevent the inhibitory effects of oleate on glycogen synthesis. We conclude that neither mitochondrial lipid metabolism nor activation of PKC-alpha, -epsilon, or -theta plays a role in the direct inhibition of glycogen synthesis by unsaturated fatty acids.
Cazzolli
R
R
Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia.
Craig
D L
DL
Biden
T J
TJ
Schmitz-Peiffer
C
C
D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004852:Epoxy Compounds / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D015870:Gene Expression; D006003:Glycogen / Q000096:biosynthesis*; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D050356:Lipid Metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D009154:Mutation; D019301:Oleic Acid / Q000494:pharmacology; D010084:Oxidation-Reduction; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D000074121:Protein Kinase C-theta; D014162:Transfection
D004791:Enzyme Inhibitors; D004852:Epoxy Compounds; D005231:Fatty Acids, Unsaturated; D007328:Insulin; D007527:Isoenzymes; D019301:Oleic Acid; D006003:Glycogen; C497256:Prkce protein, mouse; C496630:Prkca protein, mouse; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D000074121:Protein Kinase C-theta; C054207:etomoxir