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Fatty acid‐induced defects in insulin signalling, in myotubes derived from children, are related to ceramide production from palmitate rather than the accumulation of intramyocellular lipid
Author(s) -
Sabin Matthew A.,
Stewart Claire E.H.,
Crowne Elizabeth C.,
Turner Stephen J.,
Hunt Linda P.,
Welsh Gavin I.,
Grohmann Malcolm J.,
Holly Jeff M.P.,
Shield Julian P.H.
Publication year - 2007
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.20922
Subject(s) - medicine , ceramide , endocrinology , insulin resistance , palmitic acid , insulin , biology , fatty acid , lipotoxicity , lipid metabolism , chemistry , apoptosis , biochemistry
The elevation of free fatty acids (FFAs), observed in childhood obesity results in intramyocellular lipid (IMCL) accumulation with consequent insulin resistance. Using in vitro differentiated myotubes from normal weight pre‐pubertal children (n = 8), we examined the effects of saturated (palmitate) and unsaturated (oleate) FFAs on insulin‐stimulated AKT phosphorylation (pAKT) and IMCL accumulation. Palmitate decreased pAKT (Mean [SEM] % change pAKT with palmitate 750 µM vs. control; pThr308 site −50.5% [28.7] and pSer473 site −38.7% [11.7]; P < 0.001) with no effect on IMCL formation. Equimolar bromopalmitate did not effect pAKT and blocking ceramide production abolished the palmitate‐induced reduction in signalling, suggesting that ceramide synthesis is critical for palmitate's actions. Oleate did not effect pAKT (1,000 µM oleate; pSer473 site −3.4% [11.4]; P = NS) but increased IMCL accumulation (+32.3% [7.1%]; P < 0.001). Co‐administration of oleate diminished the reduction in pAKT seen with palmitate (+36.4% [23.6] vs. −13.3% [13.6]; P = 0.28), with similar IMCL levels to oleate alone. Co‐administration also caused a significant reduction in 14 C‐ceramide synthesis from 14 C‐palmitate (101.6 [21.6] vs. 371.5 [122.4] DPM/mg protein; P < 0.001). In summary, palmitate appears to cause insulin resistance in children's myotubes via its metabolism to ceramide, and this process appears unrelated to IMCL formation and is ameliorated by oleate. J. Cell. Physiol. 211: 244–252, 2007. © 2007 Wiley‐Liss, Inc.