Abstract: Objective　To observe the changes of serum endogenous nociceptin/orphanin FQ (N/OFQ) and serum lipoprotein-associated phospholipase A2 (Lp-PLA2) levels in diabetic patients with silent myocardial ischemia (SMI), and to explore its significance. Methods　A total of 120 diabetes patients underwent coronary angiography were included in this study. Patients were divided into simple type 2 diabetes group (D group, n=60) and type 2 diabetes with SMI group (DS group, n=60). Clinical data of both groups were collected. The levels of fasting blood glucose (FBG), triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), aspartate aminotransferase (AST), alanine aminotransferase (ALT), serum N/OFQ and Lp-PLA2 were detected. The differences of serum N/OFQ and Lp-PLA2 levels were compared between the two groups. The risk factors of type 2 diabetes with SMI and the correlation between     N/OFQ, Lp-PLA2 and various indicators were analyzed. The receiver operating characteristic (ROC) curve was used to analyze the predictive values of N/OFQ and Lp-PLA2 for type 2 diabetes with SMI. Results　The diabetes course, FBG, TG, LDL-C, serum N/OFQ and Lp-PLA2 levels were significantly higher in DS group than those in D group, and the HDL-C level was significantly lower in DS group than that in D group (P＜0.01). Multiple Logistic regression analysis showed that the increased serum levels of FBG, TG, LDL- C, N/OFQ and Lp-PLA2 were the risk factors of diabetic patients with SMI (P＜0.05). The serum levels of N/OFQ and Lp-PLA2 were positively correlated with FBG, LDL-C, and Gensini score in DS group. The diabetes course, HbA1c and serum N/OFQ levels were positively correlated. There was no significant correlation between diabetes course, HbA1c and serum Lp-PLA2 levels. The serum N/OFQ and Lp-PLA2 levels were positively correlated. ROC curve analysis results showed that the areas under the curves of N/OFQ, Lp-PLA2 and combined predictors predicting the occurrence of diabetes with SMI were 0.949, 0.899 and 0.956 (P＜0.01). Conclusion　The serum levels of    N/OFQ and Lp-PLA2 are higher in patients with diabetes and SMI. N/OFQ and Lp-PLA2 are closely related to the occurrence of diabetes and SMI.

Key words: diabetes mellitus, type 2, coronary disease, phospholipases A2, lipoproteins, silent myocardial ischemia, orphanin FQ