Fasting Plasma C-Peptide and Micro- and Macrovascular Complications in a Large Clinic-Based Cohort of Type 1 Diabetic Patients

OBJECTIVE - A protective effect of residual P-cell function on microvascular complications of type 1 diabetes has been suggested. Our aim was to retrospectively evaluate the association of fasting plasma C-peptide values with micro- and macrovascular complications. RESEARCH DESIGN AND METHODS - We recruited a clinic-based cohort of 471 type 1. diabetic Patients born after 1945 and cared for in the period 1994-2004. Centralized measurements and standardized procedures of ascertainment of micro- and macrovascular complications were employed. Individual cumulative averages of A1C up to 2007 were calculated. RESULTS - Residual beta-cell secretion was detected even many years after diabetes diagnosis. In multivariate linear regression analysis, fasting plasma C-peptide values were positively associated with age at diagnosis (P = 0.02 P < 0.0001) and triglycerides (P = 0.20; P = 0.05) and inversely associated with diabetes duration (P = -0.03; P < 0.0001.) and HDL cholesterol (P = -0.006; P = 0.03). The final model explained 21% of fasting C-peptide variability. With respect to fasting C-peptide values in the lowest tertiel (<0.06 nmol/l), higher values were associated with lower prevalence of microvascular complications (odds ratio [OR] 0,59 [95% CI 0.37-0.94]) independently of age, sex, diabetes duration, individual cumulative A1C average during the Study period, hypertension, and cardiovascular diseases. No association was evident with macrovascular complications (0.77 [0.38-1.58]). CONCLUSIONS - Our study shows an independent protective effect of residual P-cell function on the development of microvascular complications in type 1 diabetes, Suggesting the potential beneficial effect of treatment that allows the preservation of even modest P-cell function over time.