Although glucose-dependent insulinotropic polypeptide (GIP) levels have been characterized previously, GLP-1 levels in Asians remain unclear. Here, we investigate total and intact levels of GLP-1, as well as GIP during oral glucose and meal tolerance tests (OGTT and MTT) in Japanese patients with or without type 2 diabetes (T2DM). Seventeen Japanese healthy controls and 18 age-matched and untreated patients with T2DM of short duration participated in the present study. Fasting levels of total GPL-1 were similar between the two groups (approximately 15 pM), and intact GLP-1 levels were considerably low in both groups (less than 1 pM). In both groups, total GLP-1 reached a peak 30 min after glucose ingestion (30-40 pM), whereas intact GLP-1 levels remained low with no significant peak. In MTT, total and intact GLP-1 showed no obvious peak. The current data indicate that intact GLP-1 levels are considerably low in the Japanese and that meal-induced enhancement of GLP-1 secretion is negligible in the Japanese. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00010.x, 2010).
Keywords: DPP‐4; GIP; GLP‐1.