Abstract: Objective To explore the correlation between peripheral blood cysteine-rich protein 61 (CCN1) and early renal injury in patients with type 2 diabetes mellitus (T2DM). 
Methods A retrospective study was conducted on 321 patients with T2DM in the Second Hospital of Shijiazhuang City. Using the urinary albumin excretion rate (UAER) as the gold standard, the patients were divided into three groups: early renal injury group (n=78, 20 μg/min≤UAER≤200 μg/min), diabetic nephropathy (DN) group (n=28, UAER＞200 μg/min) and normal group (n=215, UAER＜20 μg/min). The expression of CCN1 in peripheral blood of the three groups was compared. Pearson method was used to determine the correlation between UAER and CCN1 in peripheral blood, and receiver operating characteristic (ROC) curve was used to evaluate the predictive value of CCN1 in peripheral blood for early renal injury and DN in T2DM patients. Univariate analysis was used to analyze baseline data and multivariate logistic regression analysis was used to determine the influencing factors of early renal injury or DN. 
Results The levels of CCN1 and UAER in DN group were higher than those in early renal injury group and normal group, and the levels of CCN1 and UAER in the early renal injury group were also higher than those in the normal group (P＜0.05). There was a positive correlation between peripheral blood CCN1 and UAER, and the difference was statistically significant (r=0.916, P＜0.001). Using peripheral blood CCN1 as the test variable, the ROC curve was plotted with early renal injury as the state scalar, sensitivity as the Y-axis, and "1-specificity" as the X-axis. The ROC results showed that the critical value for CCN1 diagnosis was 1.59 μg/L, with a corresponding sensitivity of 85.85%, specificity of 73.02%, and AUC of 0.871 (95%CI: 0.831-0.903). Peripheral blood CCN1 was used as the test variable, with the occurrence of DN as the state scalar, sensitivity as the Y axis, and "1-specificity" as the X axis to draw the ROC curve. The ROC results showed that the critical value for CCN1 diagnosis was 3.41 μg/L, with a corresponding sensitivity of 71.43%, specificity of 73.72%, and AUC of 0.761 (95%CI: 0.707-0.813). There were significant differences in the course of disease, hypertension, hyperlipidemia, systolic blood pressure(SBP), fasting plasma glucose(FPG), HbA1c, uric acid (UA), total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL)among the DN group, the early renal injury group and the normal group (P＜0.05). Logistic regression analysis showed that the course of disease (OR=1.740, 95%CI: 1.180-2.565), SBP (OR=1.943, 95%CI: 1.267-2.978), hyperlipidemia (OR=1.654, 95%CI: 1.310-2.088), FPG (OR=2.776, 95%CI: 1.260-6.116), UA (OR=2.228, 95%CI: 1.174-4.229) and CCN1 (OR=3.744, 95%CI: 1.709-8.200) were the influencing factors of early renal injury in T2DM patients (P＜0.05). Logistic regression analysis showed that the course of disease (OR=1.752, 95%CI: 1.177-2.609), SBP (OR=1.818, 95%CI: 1.034-3.198), hyperlipidemia (OR=1.680, 95%CI: 1.320-2.138), FPG (OR=2.389, 95%CI: 1.519-3.758), UA (OR=1.260, 95%CI: 1.038-1.530) and CCN1 (OR=3.815, 95%CI: 1.636-8.897) were the influencing factors of DN (P＜0.05). 
Conclusion Peripheral blood CCN1 demonstrates a positive correlation with urinary albumin excretion rate, thereby serving as a risk factor for the onset of early-stage renal injury and DN. It can be used to predict the occurrence of early renal injury or DN, which is worthy of further clinical research and promotion. 

Key words: diabetes mellitus, type 2, cysteine-rich protein 61, renal injury