Postprandial Glycemic Control Conditions in Relation to Urinary N-Acetyl-[beta]-d-Glucosaminidase in Patients with Type 2 Diabetes Mellitus Without Low Glomerular Filtration Rate

Background: This study assessed the relationship between the serum level of 1,5-anhydroglucitol (1,5-AG), a marker of postprandial hyperglycemia, and the ratio of the urinary activity of N -acetyl-β -d-glucosaminidase (NAG) to creatinine (NAG index) in patients with type 2 diabetes mellitus. Subjects and Methods: This was a cross-sectional study with 153 patients who had an estimated glomerular filtration rate of ≥60 mL/min/1.73 m2 and no proteinuria and who had never been treated with oral hypoglycemic agents or insulin. On the basis of 1,5-AG levels, the patients were divided into a High 1,5-AG group (>14.0 μ g/mL) and a Low 1,5-AG group (≤14.0 μ g/mL). Results: The logarithmically transformed NAG index was significantly higher in the Low 1,5-AG group than in the High 1,5-AG group when all glycated hemoglobin (HbA1c) levels were included. The logarithmically transformed NAG index was lowest in the High 1,5-AG group with an HbA1c level of ≤6.4% and was highest in the Low 1,5-AG group with an HbA1c level of ≥7.5%. Multivariate regression analysis showed that the NAG index had a higher independent association with 1,5-AG than with HbA1c or the fasting plasma glucose level. In all models, multivariate regression analyses showed that the NAG index was correlated with age. Conclusions: These results suggest that postprandial hyperglycemia correlates with early renal tubule injury in type 2 diabetes mellitus.