AimTo investigate the association between serum YKL-40 and degree of coronary artery disease (CAD) in patients with type 2 diabetes mellitus.Methods197 patients with type 2 diabetes mellitus undergoing coronary angiography because of angina-like symptoms were divided into control group (n=89) and CAD group (n=108) according to the absence or presence of significant coronary stenosis (luminal diameter narrowing of ≥50%).The degree of CAD was graded as single-, double- or three-vessel disease, and Gensini score was used to evaluate the extent of CAD.Serum YKL-40 and high sensitivity C-reactive protein (hs-CRP) levels were assessed by ELISA.ResultsCompared with control group, CAD patients were more cigarette smoker and had higher systolic blood pressure and serum levels of total cholesterol (TC), low density lipoprotein cholesterol (LDLC), apolipoprotein B (ApoB), lipoprotein (a) (Lp(a)), 2 h postprandial blood glucose (2h BG), HbA1c, YKL-40, and hs-CRP (all p<0.05).Serum YKL-40 level was increased in patients with CAD, which was more remarkable in those with two- or three-vessel disease (p<0.01), and the Gensini score of single-vessel disease was lower than that of two-disease and three-disease vessel (p<0.01).Furthermore, significant correlation between serum YKL-40 and Gensini score was observed (r=0.611, p<0.01).Multivariate Logistic regression analysis indicated that serum YKL-40 was a risk factor for CAD in patents with 2 diabtetes mellitus (OR=1.229, 95%CI was 1.086～1.427, p=0.003).ConclusionsYKL-40 may be involved in the initiation and development of atherosclerosis in diabetic patients, and serum YKL-40 level is associated with the severity of CAD in patients with type 2 diabetes mellitus.