This paper reports on the effect of GCP-02, a dual activator of the peroxisome proliferator-activated receptors alpha/gamma (PPARalpha/gamma), on glucose and lipid metabolism in insulin-resistant obese mice induced by monosodium glutamate. The mice were divided into four groups on the basis of treatment: control group, rosiglitazone (positive control) (7 micromol/kg), and low- and high-dosage GCP-02 (7 micromol/kg and 3.5 micromol/kg, respectively). Drugs were given orally once a day for 19 days, and mice underwent testing for insulin tolerance, oral glucose tolerance and gluconeogenesis, and plasma cholesterol, triglyceride and free fatty acid levels. Mice were sacrificed, and body length and weight were measured; intraperitoneal adipose, heart and liver weighed; and plasma alanine aminotransferase (ALT) level and aspartate aminotransferase (AST) activity measured. Liver, soleus muscle and myocardium were assayed for glycogen, triglyceride and free fatty acid content and myocardia tested for superoxide dismutase (SOD) activity and malonaldehyde content. RT-PCR revealed expression of insulin receptor substrate 1 and 2 (IRS1, IRS2) and related genes in liver. GCP-02 had a more powerful effect than rosiglitazone on improving insulin sensitivity, ameliorating glucose tolerance, suppressing L-alanine-induced gluconeogenesis, and decreasing plasma levels of cholesterol, triglyceride and free fatty acid. It reduced body weight in control mice, significantly lowered hepatic content of glycogen, triglyceride and free fatty acid and myocardial content of triglyceride, and increased myocardial SOD activity. IRS2 mRNA was down-regulated in control mice but up-regulated by GCP-02. Thus, GCP-02 is a potential candidate for the prevention and therapy of diseases associated with insulin resistance such as type 2 diabetes mellitus and cardiovascular disease.