Intracellular ceramide synthesis and protein kinase Cζ activation play an essential role in palmitate-induced insulin resistance in rat L6 skeletal muscle cells

Darren J. Powell, Sophie Turban, Alexander Gray, Eric Hajduch, Harinder S. Hundal

    Research output: Contribution to journalArticle

    200 Citations (Scopus)

    Abstract

    Non-esterified fatty acids (NEFAs) have been implicated in the pathogenesis of skeletal muscle insulin resistance that may develop, in part, as a consequence of a direct inhibitory effect on early insulin signalling events. Here we report work investigating the mechanism by which palmitate (a saturated free fatty acid) inhibits insulin action in rat L6 myotubes. Palmitate suppressed the insulin-induced plasma membrane recruitment and phosphorylation of protein kinase B (PKB) and this was associated with a loss in insulin-stimulated glucose transport. The inhibition in PKB was not due to a loss in insulin receptor substrate (IRS)1 tyrosine phosphorylation, IRS-1/p85 (phosphoinositide 3-kinase) association or suppression in phosphatidyl 3,4,5 triphosphate synthesis, but was attributable to an elevated intracellular synthesis of ceramide (6-fold) from palmitate and a concomitant activation of protein kinase PKCζ (5-fold). Inhibitors of serine palmitoyl transferase suppressed the intracellular synthesis of ceramide from palmitate, prevented PKCζ activation, and antagonized the inhibition in PKB recruitment/ phosphorylation and the loss in insulin-stimulated glucose transport elicited by the NEFA. Inhibiting the palmitate-induced activation of PKCζ with Ro 31.8220, also prevented the loss in the insulin-dependent phosphorylation of PKB caused by palmitate. These findings indicate that intracellular ceramide synthesis and PKCζ activation are important aspects of the mechanism by which palmitate desensitizes L6 muscle cells to insulin.

    Original languageEnglish
    Pages (from-to)619-629
    Number of pages11
    JournalBiochemical Journal
    Volume382
    Issue number2
    DOIs
    Publication statusPublished - 1 Sep 2004

    Keywords

    • Adipocytes
    • Free fatty acids
    • Muscle
    • Protein kinase B (PKB)/Akt
    • Serine palmitoyl transferase (SPT)

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