Usefulness of urinary glucose excretion after oral glucose tolerance testing to detect insulin secretion failure before the onset of diabetes mellitus

: Sodium-glucose cotransporter 2 inhibitors are commonly used to promote urinary glucose excretion (UGE). However, it remains unclear how UGE reflects glucose metabolism in the natural history of diabetes. Thus, we retrospectively reviewed the prediabetes medical records of 64 patients who had undergone 75-g oral glucose tolerance testing (OGTT) with measurements of UGE at 0 min, 60 min, and 120 min. The mean age and glycated hemoglobin levels were 46 ± 10 years and 5.6 ± 0.3%, respectively. The median UGE (60 min + 120 min) value was 16.8 mg ([interquartile range]: [10.5-150.0 mg]). Thus, we categorized 16 patients as having high UGE (≥150.0 mg) and 48 patients as having low UGE (<150.0 mg). As compared with the low UGE group, the high UGE group exhibited a significantly lower median insulinogenic index (0.23 [0.12-0.35] vs. 0.56 [0.31-1.06], p = 0.001) and homeostasis model assessment of β-cell function value (46 [26-67] vs. 66 [41-85], p = 0.028). The log-transformed insulinogenic index exhibited a significant inverse association with log-transformed UGE (60 min + 120 min) (r = -0.50, p < 0.001). The association between higher UGE and lower insulinogenic index was also observed in a subgroup analysis of patients with plasma glucose levels of ≥160 mg/dL during the OGTT. Therefore, UGE measurements after OGTT may provide a useful clinical marker for detecting insulin secretion failure and advancing preventive and therapeutic interventions among populations with a high risk of developing diabetes.