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 -cell function on microvascular complications of type 1 diabetes has been suggested. Our aim was to retrospectively evaluate the association between fasting plasma C-peptide values and micro- and macrovascular complications. Research design and methods: We recruited a clinic-based cohort of 471 type 1 diabetic persons, born after 1945 and cared for in period 1994-2004. Centralized measurements and standardized procedures of ascertainment of micro- and macrovascular complications were employed. Individual cumulative average of HbA1c up to 2007 was calculated. Results: a residual -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 (β=0.02, p<0.0001) and triglycerides (β =0.20, p=0.05), and inversely associated with diabetes duration (β=-0.03, p<0.0001), and HDL-cholesterol (β =-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 tertile (< 0.06 nmol/l), higher values were associated with lower prevalence of microvascular complications (OR=0.59, 95% CI 0.37-0.94), independently of age, sex, diabetes duration, individual cumulative HbA1c average during the study period, hypertension, and cardiovascular diseases. No association was evident with macrovascular complications (OR=0.77, 95% CI 0.38-1.58). Conclusions: Our study shows an independent protective effect of residual -cell function on the development of microvascular complications in type 1 diabetes, suggesting the potential beneficial effect of treatment allowing the preservation of even modest β-cell function over time.