1,5-Anhydroglucitol reflects postprandial hyperglycemia and a decreased insulinogenic index, even in subjects with prediabetes and well-controlled type 2 diabetes

To examine the serum 1,5-anhydroglucitol (AG) levels as a surrogate measure of postprandial hyperglycemia (PPH) and insulin secretion in a wide range of hyperglycemia, we compared the relationship between the glycemic index during a 75 g oral glucose tolerance test (OGTT) and the insulinogenic index and 1,5-AG according the overall glycemic state. Fasting serum 1,5-AG levels were lower in the type 2 diabetic group (18.0 ± 7.0 μg/mL) than in the normal glucose tolerance (NGT, 25.4 ± 4.0 μg/mL), impaired fasting glucose (IFG, 24.6 ± 6.2 μg/mL), and impaired glucose tolerance (IGT, 22.1 ± 6.2 μg/mL) groups and were clearly correlated with glycemic values from the OGTT. 120-min post-challenge plasma glucose (PPG120) emerged as an independent predictor for 1,5-AG levels after multiple linear regression analysis (β = −0.554, P < 0.001). Additionally, 1,5-AG levels were significantly correlated with PPG120 in each quartile of A1C, and the coefficients increased with higher A1C quartiles. Subjects with low 1,5-AG levels had both increased insulin resistance and decreased insulin secretion. Decreased 1,5-AG levels are closely correlated with PPH and decreased insulin secretion capacity across a wide range of glycemia, even in relatively well-controlled diabetes.