Serum complement hs-CRP, C3d, and MBL levels in microvascular complications of type 2 diabetes

Background: To investigate the connections between microvascular complications (DMCs) and serum complement hs-CRP, C3d, and MBL levels in individuals with type 2 diabetes mellitus (T2DM). Methods: From January 2023 to January 2025, 100 patients with simple T2DM admitted to our hospital were selected as the T2DM group, 100 patients with T2DM combined with DMC were selected as the DMC group, and 100 healthy individuals who underwent physical examinations during the same period were selected as the control group. The serum levels of complement hs-CRP, C3d, and MBL were compared among the three groups. The relationships between complement hs-CRP, C3d, and MBL and the blood glucose and lipid markers of DMC patients were examined using Pearson correlation analysis. Binary logistic regression analysis was used to investigate the risk factors for DMC in patients with type 2 diabetes. The diagnostic value of blood complement hs-CRP, C3d, and MBL for DMC in T2DM patients was evaluated using the receiver operating characteristic curve (ROC) and the area under the curve (AUC). Results: Comparison of serum complement hs-CRP, C3d, and MBL levels revealed the following trend: DMC group > T2DM group > control group, with statistically significant differences (P<0.05). Body mass index (BMI), length of illness, fasting blood glucose (FPG), glycosylated haemoglobin (HbA1c), lipid markers (triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), insulin resistance index (HOMA-IR), blood uric acid (UA), and creatinine (Scr) were significantly different between the DMC and T2DM groups. In T2DM patients who developed DMC, blood complement hs-CRP, C3d, and MBL levels were favourably correlated with FPG, HbA1c, TG, TC, and LDL-C levels and negatively correlated with HDL-C levels (P<0.05), according to the Pearson correlation analysis. Binary logistic regression analysis revealed that disease duration and FPG, HbA1c, hs-CRP, C3d, and MBL levels were factors associated with DMCs in patients with T2DM (P<0.05). ROC curve analysis showed that the optimal hs-CRP cut-off value for detecting DMCs in patients with T2DM was 293.68 mg/L, with an AUC of 0.834 (95% CI 0.754–0.914), a sensitivity of 0.844, and a specificity of 0.803. The optimal C3d cut-off value was 394.25 mg/L, with an AUC of 0.835 (95% CI 0.741–0.919), a sensitivity of 0.830, and a specificity of 0.805. The optimal MBL cut-off value was 330.32 mg/L, with an AUC of 0.827 (95% CI 0.739–0.915), a sensitivity of 0.823, and a specificity of 0.776. Conclusion: The pathogenic progression of DMC in T2DM is significantly influenced by serum complement activation. Elevated levels of serum complement components hs-CRP, C3d, and MBL can increase the risk of DMC in T2DM patients. In patients with type 2 diabetes, these three markers can be used as trustworthy predictors of the development of DMC.