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This Article Full Text Full Text (PDF) All Versions of this Article: JOE-08-0122v1 198/2/375    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Kelly, K. R Articles by Turcotte, L. P PubMed PubMed Citation Articles by Kelly, K. R Articles by Turcotte, L. P

¹ Departments of Kinesiology and Biological Sciences, College of Letters, Arts, and Sciences, University of Southern California, 3560 Watt Way, PED 107,  Los Angeles, California 90089-0652, USA Departments of² Biological Sciences, College of Letters, Arts, and Sciences³ Physiology and Biophysics, School of Medicine, University of Southern California, Los Angeles, California 90033, USA

(Correspondence should be addressed to L P Turcotte; Email: turcotte{at}usc.edu)

Insulin is important in the regulation of muscle metabolism. However, its role in the regulation of muscle long-chain fatty acid (LCFA) metabolism, independent of glucose, is not clear. To determine whether insulin regulates LCFA metabolism independent of glucose and if so, via which signaling pathway, L6 myotubes were incubated, in the presence or absence of insulin (100 nM) and with either an inhibitor of phosphatidylinositol 3-kinase (PI3K) (wortmannin (W), 50 nM), protein kinase B (PKB)/Akt (A, 10 µM), or atypical protein kinase C- (aPKC-) (mP, 100 µM). LCFA kinetic parameters were measured via incubation with [1-¹⁴C]palmitate. Basal LCFA uptake was found to increase linearly with time (1–60 min) and concentration (50–750 µM). LCFA uptake increased in the presence of insulin and was maximum at 10 nM (P<0.05). Wortmannin prevented the insulin-induced increase in LCFA uptake and decrease in LCFA oxidation. While mP abolished the insulin-induced increase in LCFA uptake, it did not prevent the insulin-induced decrease in LCFA oxidation. None of the variables were affected by Akt inhibition. These results suggest a direct effect of insulin on LCFA metabolism in muscle cells, and that downstream of PI3K, aPKC-, but not PKB/Akt mediates the effects of insulin on LCFA uptake but not oxidation.