Relationship of residual beta-cell function, metabolic control and chronic complications in type 2 diabetes mellitus.

As the relationships between C-peptide levels and metabolic control and chronic complications are poorly known in type 2 diabetes, due to the slow decline of beta-cell function, we evaluated these associations in a cohort of type 2 diabetic patients. After excluding insulin-treated subjects, 1,533 patients were divided according to their C-peptide fasting levels in quartiles. Patients within the lowest C-peptide quartile showed significantly higher duration of diabetes, prevalence of retinopathy and values of HDL-cholesterol, albumin excretion rate and HbA1c, while BMI, diastolic blood pressure, percentages of hypertension and metabolic syndrome, and values of triglycerides and uric acid were significantly higher in the highest C-peptide quartile. The associations between C-peptide and duration of diabetes, AER, HbA1c, retinopathy and the components of the metabolic syndrome remained significant, after multiple adjustments. In conclusion, these data support the hypothesis that a reduced insulin secretion is associated with a longer duration of diabetes and a greater prevalence of microvascular complications, while higher insulin levels are associated with the components of the metabolic syndrome.