Role of Tumor Suppressor PTEN in Tumor Necrosis Factor α-Induced Inhibition of Insulin Signaling in Murine Skeletal Muscle C2C12 Cells

In an attempt to clarify the role of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in muscle insulin resistance, we investigated the effect of PTEN on phosphoinositide 3 (PI3)-kinase/Akt related insulin signaling pathway in skeletal muscle-like C2C12 cells damaged by tumor necrosis factor-alpha (TNFα). C2C12 cells cultured with TNFα (10 ng/ml) for 1 h displayed a marked decrease of insulin-stimulated 2-[14C]-deoxy-d-glucose (2-DG) uptake in parallel with an elevation of PTEN mRNA and protein levels. However, pretreatment of PTEN antisense oligonucleotide (AS) (1 μmol/l for 3 days) for specific inhibition of PTEN expression in C2C12 cells abolished the TNFα-induced changes in 2-DG uptake. Similar pretreatment with PTEN AS, but not with sense oligonucleotide (1 μmol/l for 3 days), eliminated the ability of TNFα to impair insulin-stimulated signals including p85 regulatory subunit of PI3-kinase expression and the degree of Akt serine phosphorylation as well as protein expression in glucose transporter subtype 4. Data taken from cultured C2C12 cells emphasize the negative regulatory of muscle PI3-kinase/Akt signaling pathways as the major substrate of PTEN but also support the concept that PTEN contributes to the development of insulin resistance in skeletal muscle.