Aim To explore the relationship of serum leptin,adiponectin concentrations and adiponectin-to-leptin ratio(A/L) to coronary lesion in patients with type 2 diabetes mellitius. Methods Serum levels of adiponectin and leptin in 180 patients with type 2 diabetes mellitius were measured by specific monoclonal antibody-based amplified ELISA.Coronary lesion was measured by using coronary angiography.The patients with type 2 diabetes mellitius were divided into coronary heart disease group(coronary artery stenosis in a major blood vessel was more than 50%,n=94) and control group(coronary artery stenosis in a major blood vessel was less than 25%,n=86).Coronary heart disease group was subdivided into single-vessel disease group(n=31),double-vessel disease group(n=31) and multi-vessel disease group(n=32).Then,the correlation between risk factors for coronary heart disease and A/L or homeostasis assessment for insulin resistance(HOMA-IR) was analyzed. Results Age,gender composition ratio,blood pressure,blood sugar and body mass index(BMI) were matched in two groups.Serum levels of total cholesterol,C-reactive protein(CRP) and fibrinogen in coronary heart disease group were significantly higher than those of the control group.Serum levels of high-density lipoprotein cholesterol(HDLC),adiponectin and A/L in coronary heart disease group were significantly lower than those of the control group.Correlation analysis showed that age,fibrinogen and CRP were positively associated with coronary lesion and that adiponectin and A/L were negatively associated with coronary lesion.After calibration of BMI,there was also a negative correlation between severity of coronary artery stenosis and A/L(r=-0.541).This relationship remained in multivariate Logistic regression analysis.A/L became smaller with the increase in the number of coronary lesions branches(2.10 vs 1.37 vs 0.72),with a significant difference in the three groups.The hierarchical results showed that A/L ratio was significantly correlated with BMI,blood pressure,blood sugar,triglycerides,HDLC,CRP and fibrinogen in coronary heart disease group,and significant correlation of these parameters except HOMA-IR with A/L ratio still existed as degree of coronary lesion was gradually increased. Conclusion A/L is in relation to the formation of atherosclerosis and may serve as atherosclerosis index.A/L is also effective as a parameter of insulin resistance to coronary artery disease as compared with adiponectin,leptin,or HOMA-IR alone in patients with type 2 diabetes.