PPAR‐ γ expression modulates insulin sensitivity in C2C12 skeletal muscle cells

Peroxisome proliferator‐activated receptor‐ γ (PPAR‐ γ ) expression is very low in skeletal muscle cells, which is one of the most important target tissues for insulin and plays a predominant role in glucose homeostasis. It has recently been shown that muscle‐specific PPAR‐ γ deletion in mouse causes insulin resistance. However, it is likely that the observed effects might be due to secondary interaction in whole animal. The aim of the study was to explore the role of muscle PPAR‐ γ in insulin sensitivity. We stably transfected C2C12 skeletal muscle cells with plasmids containing sense or antisense constructs of PPAR‐ γ and examined the effect of modulation of PPAR‐ γ expression in terms of glucose uptake. Effect was also examined in insulin‐resistant C2C12 skeletal muscle cells. In transfected C2C12 cell line, the inhibition of PPAR‐ γ expression (23.0±0.005%) was observed to induce insulin resistance as determined by functional assessment of 2‐deoxyglucose incorporation. Overexpression of PPAR‐ γ (28.5±0.008%) produced an additional effect on insulin (100 n M ) and Pioglitazone (50 μ M ), resulting in 42.7±3.5% increase in glucose uptake as against 29.2±2.8% in wild‐type C2C12 skeletal muscle cells differentiated under normal (2% horse serum) condition. Under similar treatment, PPAR‐ γ overexpressing cells resistant to insulin exhibited enhanced glucose uptake upto 60.7±4.08%, as compared to 23.8±5.1% observed in wild‐type C2C12 skeletal muscle cells. These data demonstrate a direct involvement of PPAR‐ γ in insulin sensitization of TZD action on skeletal muscle cells, and suggest that pharmacological overexpression of muscle PPAR‐ γ gene in skeletal muscle might be a useful strategy for the treatment of insulin resistance.British Journal of Pharmacology (2004) 143 , 1006–1013. doi: 10.1038/sj.bjp.0706002