Relationship between C-peptide, Metabolic Control and Chronic Complications in Type 2 Diabetes

Kang, Jeung Mook; Lee, Won Young; Kim, Ji Youn; Yun, Jung Won; Kim, Sun Woo

Abstract

BACKGROUND: Type 2 diabetes mellitus is a heterogeneous disease characterized by variable degrees of insulin resistance, impaired insulin secretion and increased glucose production. As the decline of beta-cell function in type 2 diabetes is very slow, the relationship between the insulin secretory capacity, the degree of metabolic control and chronic complications is still unclear. The determination of plasma C-peptide allows for the assessment of the endogenous insulin production, even in the presence of exogenous insulin administration. The aim of this study was to evaluate the relationship between the serum C-peptide level and metabolic parameters, and the complications in type 2 diabetes. METHOD: The clinical characteristics and laboratory findings, such as lipid profile, fasting plasma glucose, HbA1C and uric acid, were evaluated, and their relationships with chronic complications analyzed. We measured the serum C-peptide level by radioimmunoassay (RIA) in 384 type 2 diabetes mellitus patients. The patients were divided into quartile groups according to their fasting C-peptide levels (quartile 1: <1.73 ng/mL, n=95; quartile 2:>or=1.73 ng/mL and <2.38 ng/mL, n=95; quartile 3:>or=2.38 ng/mL and <3.18 ng/mL, n=98; quartile 4:>or=3.18 ng/mL, n=96).
RESULTS
Patients in the lowest C-peptide quartile showed significantly higher durations of diabetes, HbA1C and postprandial plasma glucose values, and HDL-cholesterol. Conversely, the BMI, systolic blood pressure, total cholesterol and triglyceride were significantly higher in the highest C-peptide quartile. The prevalence of diabetic retinopathy and urinary protein excretion were higher in lowest quartile, and the diastolic blood pressure was highest in the upper quartile, but these were not statistically significant. The associations between C-peptide, and the duration of diabetes, BMI, total cholesterol, triglyceride, HDL cholesterol, postprandial 2 plasma glucose and systolic blood pressure remained significant, even after multiple adjustments.
CONCLUSION
In type 2 diabetes, higher C-peptide levels are associated with a component of metabolic syndrome and lower C-peptide levels due to decreased cell reserves, associated with hyperglycemia and microvascular complications