There is a growing body of evidence that the formation and accumulation of advanced glycation end products (AGE) have been known to progress under diabetic conditions, thereby being involved in diabetic vascular complications. Further, we, along with others, have recently found AGE could disturb insulin actions in cultured adipocytes and skeletal muscles. However, the pathological role of AGE in insulin resistance in vivo is not fully understood. Therefore, in this study, we examined whether pyridoxamine, an inhibitor of AGE formation could ameliorate insulin resistance in KK-Ay mice, a model animal of obese, type 2 diabetes. Fasting blood glucose, serum levels of insulin and AGE in KK-Ay mice were elevated as the mice got older (from 5 weeks old to 15 weeks old). Serum levels of AGE were positively correlated with insulin (R2=0.3956, P=0.002) in KK-Ay mice. Administration of pyridoxamine dose-dependently decreased fasting insulin levels and improved insulin sensitivity in KK-Ay mice of 10 weeks old, although it did not affect fasting blood glucose levels. Our present study suggests the involvement of AGE in insulin resistance in KK-Ay mice. Inhibition of AGE formation may be a novel therapeutic target for improving insulin resistance in diabetes with obesity.