Sphingolipid changes do not underlie fatty acid-evoked GLUT4 insulin resistance nor inflammation signals in muscle cells

J Lipid Res. 2018 Jul;59(7):1148-1163. doi: 10.1194/jlr.M080788. Epub 2018 May 23.


Ceramides contribute to obesity-linked insulin resistance and inflammation in vivo, but whether this is a cell-autonomous phenomenon is debated, particularly in muscle, which dictates whole-body glucose uptake. We comprehensively analyzed lipid species produced in response to fatty acids and examined the consequence to insulin resistance and pro-inflammatory pathways. L6 myotubes were incubated with BSA-adsorbed palmitate or palmitoleate in the presence of myriocin, fenretinide, or fumonisin B1. Lipid species were determined by lipidomic analysis. Insulin sensitivity was scored by Akt phosphorylation and glucose transporter 4 (GLUT4) translocation, while pro-inflammatory indices were estimated by IκBα degradation and cytokine expression. Palmitate, but not palmitoleate, had mild effects on Akt phosphorylation but significantly inhibited insulin-stimulated GLUT4 translocation and increased expression of pro-inflammatory cytokines Il6 and Ccl2 Ceramides, hexosylceramides, and sphingosine-1-phosphate significantly heightened by palmitate correlated negatively with insulin sensitivity and positively with pro-inflammatory indices. Inhibition of sphingolipid pathways led to marked changes in cellular lipids, but did not prevent palmitate-induced impairment of insulin-stimulated GLUT4 translocation, suggesting that palmitate-induced accumulation of deleterious lipids and insulin resistance are correlated but independent events in myotubes. We propose that muscle cell-endogenous ceramide production does not evoke insulin resistance and that deleterious effects of ceramides in vivo may arise through ancillary cell communication.

Keywords: ceramides; glucose transporter 4; inflammation; lipidomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Fatty Acids / metabolism*
  • Glucose Transporter Type 4 / metabolism*
  • Inflammation / metabolism
  • Inflammation / pathology
  • Insulin Resistance*
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / metabolism
  • Muscle Fibers, Skeletal / pathology
  • Muscles / metabolism*
  • Muscles / pathology*
  • NF-kappa B / metabolism
  • Palmitic Acid / pharmacology
  • Protein Transport / drug effects
  • Rats
  • Signal Transduction* / drug effects
  • Sphingolipids / metabolism*


  • Fatty Acids
  • Glucose Transporter Type 4
  • NF-kappa B
  • Sphingolipids
  • Palmitic Acid