Aims: Elevated plasma free fatty acids impair the insulin signaling by induction of the expression of protein phosphatases. However, the effect of palmitate on SH2-containing inositol 5'-phosphatase 2 (SHIP2) expression has not been investigated. Here we investigated the effects of palmitate on SHIP2 expression and elucidated the underlying mechanisms in skeletal muscle cells.
Main methods: SHIP2 mRNA and protein levels were measured in C2C12 myotubes exposed to palmitate. Specific inhibitors were used to identify the signaling pathways involved in SHIP2 expression.
Key findings: The results showed that 0.5mM palmitate significantly upregulates the mRNA and protein levels of SHIP2 in C2C12 cells. To address the role of palmitate intracellular metabolites in SHIP2 expression, the myotubes were treated with palmitate in the presence of ceramide and diacylglycerol synthesis inhibitors. The results demonstrated that only ceramide synthesis inhibition could prevent palmitate-induced SHIP2 expression in these cells. In addition, the incubation of muscle cells with different concentrations of C2-ceramide dose-dependently enhanced SHIP2 expression. Furthermore, the inhibition of both JNK and NF-κB pathways could prevent ceramide-induced SHIP2 expression in myotubes.
Significance: These findings suggest that palmitate contributes to SHIP2 overexpression in skeletal muscle via the mechanisms involving the activation of ceramide-JNK and NF-κB pathways.
Keywords: C2C12; Ceramide; Insulin resistance; Palmitate; SHIP2.
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