Correlations between Glucagon Stimulated C-peptide Levels and Microvascular Complications in Type 2 Diabetes Patients

Background: This study aimed to investigate whether stimulated C-peptide is associated with microvascular complications in type 2 diabetes mellitus (DM). Methods: A cross-sectional study was conducted in 192 type 2 diabetic patients. Plasma basal C-peptide and stimulated C-peptide were measured before and 6 minutes after intravenous injection of 1 mg glucagon. The relationship between C-peptide and microvascular complications was statistically analyzed. Results: In patients with retinopathy, basal C-peptide was 1.9 +/- 1.2 ng/mL, and stimulated C-peptide was 2.7 +/- 1.6 ng/mL; values were significantly lower compared with patients without retinopathy (P = 0.031 and P = 0.002, respectively). In patients with nephropathy, basal C-peptide was 1.6 +/- 0.9 ng/mL, and stimulated C-peptide was 2.8 +/- 1.6 ng/mL; values were significantly lower than those recorded in patients without nephropathy (P = 0.020 and P = 0.026, respectively). Stimulated C-peptide level was associated with increased prevalence of microvascular complications. Age-, DM duration-, and hemoglobin A1c-adjusted odds ratios for retinopathy in stimulated C-peptide value were 4.18 (95% confidence interval [ CI], 1.40 to 12.51) and 3.35 (95% CI, 1.09 to 10.25), respectively. The multiple regression analysis between nephropathy and C-peptide showed that stimulated C-peptide was statistically correlated with nephropathy (P = 0.03). Conclusion: In patients with type 2 diabetes, the glucagon stimulation test was a relatively simple method of short duration for stimulating C-peptide response. Stimulated C-peptide values were associated with microvascular complications to a greater extent than basal C-peptides.