A Study of Serum C-Reactive Protein and Interleukin-6 in Patients with Type 2 Diabetes Mellitus and Their Correlation with Diabetic Nephropathy

Abstract Background: Type 2 diabetes mellitus (T2DM) represents the predominant form of diabetes globally and is a major contributor to chronic kidney disease (CKD) through diabetic nephropathy (DN). DN is associated with both hyperglycemia-induced microvascular damage and low-grade systemic inflammation. Inflammatory biomarkers such as C-reactive protein (CRP) and interleukin-6 (IL-6) have been implicated in the pathogenesis of DN. This study aimed to assess serum CRP and IL-6 levels in T2DM patients and to correlate them with the stages of nephropathy and CKD. Materials and Methods: This hospital-based observational study included 60 patients with T2DM and 30 age- and sex-matched healthy controls. Patients were stratified into normoalbuminuria, microalbuminuria, and macroalbuminuria groups based on 24-h urinary albumin excretion. Serum CRP and IL-6 were measured via enzyme-linked immunosorbent assay. Renal function was evaluated using serum creatinine and estimated glomerular filtration rate (eGFR) to classify CKD stages. Glycemic parameters (fasting blood sugar, postprandial blood sugar, and glycated hemoglobin A1c) and duration of diabetes were also recorded. Statistical analysis included t tests, analysis of variance, and correlation tests, with significance set at P < 0.05. Results: CRP and IL-6 levels were significantly elevated in T2DM cases compared to controls (CRP: 12.9 ± 14 mg/dL vs. 0.7 ± 0.1 mg/dL; IL-6: 27.2 ± 35.9 pg/mL vs. 2.5 ± 0.6 pg/mL; P < 0.0001). A progressive increase in both markers was observed with worsening albuminuria and advancing CKD stage. Mean CRP and IL-6 were highest in the macroalbuminuria group (30.77 ± 9.63 mg/dL and 79.13 ± 19.31 pg/mL, respectively). CRP and IL-6 also correlated positively with declining eGFR and higher CKD stages ( P = 0.0011 and P = 0.0024, respectively). Glycemic indices and duration of diabetes were significantly associated with albuminuria severity. Conclusion: Elevated CRP and IL-6 levels are significantly associated with the severity of DN and CKD progression in T2DM patients. These markers may serve as noninvasive indicators for early detection and monitoring of renal complications in diabetes. Future studies should explore their role in therapeutic decision-making and inflammation-targeted interventions.