Serum Cystatin C levels increase with increasing visceral fat area in patients with type 2 diabetes mellitus

The present study aimed to explore the association between serum cystatin C (Cys-C) levels and visceral fat area (VFA) in patients with type 2 diabetes mellitus (T2DM). A total of 208 previously diagnosed T2DM patients who visited our hospital from September 2019 to December 2021 were included and divided into three groups based on tertiles of Cys-C levels, namely, Groups C1, C2, and C3. The clinical data of the subjects were collected, biochemical parameters such as Cys-C levels were determined, and bioelectrical impedance analysis was applied to determine the VFA and subcutaneous fat area (SFA). The VFA in Group C1 was lower than that in Groups C2 and C3 (all P < 0.05), with no significant difference in VFA between Groups C2 and C3 (P > 0.05). Spearman's correlation analysis revealed that the serum Cys-C level was positively correlated with age, VFA, SFA, insulin resistance index, waist circumference, body mass index, systolic blood pressure, serum creatinine level, and blood uric acid level (r = 0.543, 0.353, 0.168, 0.148, 0.365, 0.264, 0.25, 0.497, and 0.155, respectively; P < 0.05) and negatively correlated with glycated haemoglobin levels (r = -0.175, P < 0.05). Univariate linear regression analysis revealed that VFA was positively correlated with the Cys-C level (β = 0.002, 95% CI = 0.001-0.003, P < 0.05), with an increase of 0.002 mg/L in the Cys-C level for each 1 cm² increase in VFA. Further multivariate linear regression analysis was performed with the serum Cys-C level as the dependent variable and age, VFA, SFA, insulin resistance (HOMA-IR), WC, BMI, SBP, Cr, UA, and HbA1c as the independent variables. The results suggested that VFA was positively correlated with serum Cys-C level (β = 0.001, 95% CI = 0.000-0.002, P < 0.05), with serum Cys-C levels increasing by 0.001 mg/L for every 1 cm² increase in VFA. Using a VFA ≥ 100 cm² as the criterion for visceral obesity, ROC analysis revealed that the Cys-C level was a better predictor of visceral obesity, with an area under the ROC curve (AUC) of 0.701 (95% CI = 0.631-0.771, P < 0.05), an optimal cut-off of 0.905 mg/L, and a sensitivity and specificity of 58.3% and 75.2%, respectively. The results suggested that the serum Cys-C level was correlated with the VFA in patients with T2DM and that Cys-C may play a vital role in T2DM patients with visceral obesity.