Fig. 2.

PA inhibits insulin signaling in primary mouse hepatocytes through a JNK-dependent mechanism. (A) Effect of JNK inhibition on PA-induced insulin resistance. Cells were incubated with or without PA (0.5 mM) for 2 h. When indicated, the peptide inhibitor of JNK, D-JNKi, was added during PA treatment before and 10 min after addition of insulin. AKT phosphorylation was assessed by immunoblotting. (B) PA inhibits IRS1–2-associated PI3K activity. Primary hepatocytes were treated as above, and PI3K activity was separately measured in PY, IRS1, and IRS2 immunoprecipitates. (C) Effects of PA on IRS1 Ser-307 phosphorylation. Cells were treated with PA (0.5 mM) for the indicated times before IRS1 Ser-307 phosphorylation was assessed by immunoblotting. (D) Effect of JNK inhibition on PA-induced IRS1 Ser-307 phosphorylation. Cells were treated as above, except that D-JNKi was present during the PA treatment.