To investigate the association between serum C-peptide level and cardiovascular autonomic neuropathy (CAN) in individuals with type 2 diabetes mellitus (DM) according to estimated glomerular filtration rate (eGFR) METHODS: In a cross-sectional study, we examined 939 individuals with type 2 DM. We measured fasting C-peptide, 2-hour postprandial C-peptide, and ΔC-peptide (postprandial C-peptide minus fasting C-peptide) levels. The individuals were classified into 2 groups based on eGFR: individuals without impaired renal function (eGFR ≥60 ml∙min^-1 1.73m^-2) and those with impaired renal function (eGFR <60 ml∙min^-1 1.73m^-2).

Individuals with CAN had lower fasting C-peptide, postprandial C-peptide, and ΔC-peptide levels in patients both with and without impaired renal function. Multivariate logistic regression analyses adjusted for gender, age, and other confounders, including eGFR, showed that serum C-peptide level was significantly associated with CAN (odds ratio [OR] per standard deviation increase in the log-transformed value, 0.67; 95% confidence interval [CI], 0.52-0.87 for fasting C-peptide, P < 0.01; OR, 0.62; 95% CI, 0.47-0.83 for postprandial C-peptide, P < 0.01; OR, 0.71; 95% CI, 0.54-0.93 for ΔC-peptide, P < 0.05).Serum C-peptide level was negatively associated with CAN in individuals with type 2 DM independent of eGFR.