[Relationship between serum cystatin-C levels and vibrating perception threshold in patients with 
Type 2 diabetes...

To explore the relationship between serum cystatin-C (Cys-c) levels and vibrating perception threshold (VPT) in patients with Type 2 diabetes mellitus (T2DM).

According to the symptoms, signs and results of lab examination, a total of 352 patients with T2DM were divided into a diabetic peripheral neuropathy group (DPN group, n=107) and a non-diabetic peripheral neuropathy group (NDPN group, n=245). Serum Cys-c levels were measured by radioimmunoassay method. The relationship between serum Cys-c levels and VPT, estimated glomerular filtration rate (eGFR), urinary albumin-to-creatinine ratio (ACR), glucose and blood pressure and other parameters were also analyzed by correlation and multiple regression analysis. All T2DM patients were divided into a high Cys-c levels group (n=89) and a low Cys-c levels group (n=263) according to the upper quartile of Cys-c, and the incidence of DPN and VPT levels in each group were compared. Risk factors of DPN in T2DM patients were analyzed by binary logistic regression analysis and receiver operating characteristic (ROC) curve was used to identify the optimal cutoff of serum Cys-c levels for predicting DPN in patients with T2DM.

Serum Cys-c levels were significantly higher in the DPN group than that in the NDPN group [(1.04±0.43) vs (0.80±0.25) mg/L, P<0.01]. Correlation analysis showed that serum Cys-c levels were positively correlated with age, body mass index (BMI), serum creatinine (SCr), blood urea nitrogen (BUN), ACR, VPT, pulse pressure (PP), white blood cell( WBC) , red cell distribution width (RDW), hemoglobin A1c (HbA1c) and fasting blood glucose (FBG) (r=0.410, 0.115, 0.613, 0.433, 0.291, 0.300, 0.156, 0.129, 0.282, 0.314, 0.236, respectively, P<0.05 or P<0.01); and negatively correlated with diastolic blood pressure (DBP), eGFR and indirect bilirubin (IBIL) (r=-0.135, -0.647, -0.114, respectively, P<0.05 or P<0.01). Serum Cys-c levels in T2DM patients were positively correlated with VPT after adjusting for gender, age, BMI, ACR and eGFR (r=0.235, P<0.01). Multiple regression analysis revealed that VPT, age, SCr, eGFR, PP, ACR and HbA1C were independent related factors affecting serum Cys-c levels in T2DM patients. Compared with those in the low Cys-c levels group, the prevalence rate and VPT value was increased in the high Cys-c levels group (all P<0.01). Binary logistic regression analysis found that age, Cys-c and HbA1C were independent risk factors for predicting DPN in T2DM patients (all P<0.01). ROC curve analysis revealed that the optimal cutoff of Cys-c to predict DPN in T2DM patients was 0.996 mg/L, the sensitivity was 43.9%, the specificity was 83.7%, and the area under curve was 0.663.

Serum Cys-c levels are well correlated with VPT in patients with T2DM. When the serum Cys-c levels>0.996 mg/L, the predicts have high risk of DPN in T2DM patients, which might be related to diabetic nephropathy, oxidative stress and inflammatory reaction induced by advanced age, hyperglycemia and hypertension.