Analysis of clinical factors contributing to the postglucagon increment in C-peptide levels in Japanese patients with type 2 diabetes: comparison with basal C-peptide levels and 24-h urinary C-peptide excretion

• Published in: Diabetology international Vol. 4; no. 1; pp. 60 - 65
• Main Authors: Kanazawa, Akio, Tokoro, Masako, Ikeda, Fuki, Ohmura, Chie, Sato, Fumihiko, Fujitani, Yoshio, Kawamori, Ryuzo, Watada, Hirotaka
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.03.2013
• Subjects: Diabetes; Endocrinology; Medicine; Medicine & Public Health; Metabolic Diseases; Original Article; eGFR; Glucagon; β-cell; C-peptide
• ISSN: 2190-1678; 2190-1686
• DOI: 10.1007/s13340-012-0097-4

We investigated the clinical factors that affected routine laboratory tests of C-peptide levels (CPR) used for the evaluation of β-cell function in Japanese patients with type 2 diabetes. The study subjects were 215 Japanese patients with type 2 diabetes admitted to Juntendo University Hospital just for glycemic control. β-cell function was evaluated by ΔCPR (6-min postglucagon increment in CPR), CPR index (100 × fasting CPR divided by fasting glucose), and 24-h urinary CPR excretion (U-CPR). Stepwise multiple regression analyses of relationships between clinical parameters and these laboratory tests were carried out. The analysis identified BMI and treatment with insulin before admission, but not glycosylated hemoglobin at admission, as independent determinants of all β-cell function tests [BMI: Stdβ (standard regression coefficient) = 0.337, P  < 0.01 for ΔCPR, Stdβ = 0.365, P  < 0.01 for CPR index, and Stdβ = 0.207, P  < 0.01 for U-CPR, and treatment with insulin before admission: Stdβ = −0.141, P  = 0.023 for ΔCPR, Stdβ = −0.285, P  < 0.01 for CPR index, and Stdβ = −0.258, P  < 0.01 for U-CPR]. The estimated glomerular filtration rate (eGFR) was an independent determinant of U-CPR (Stdβ = 0.145, P  = 0.023), but not ΔCPR. In conclusion, ΔCPR evaluates β-cell function without being affected by eGFR and glycemic control over the preceding 2–3 months.