Glucose‐derived breath CO ₂ kinetics in IGT and NGT subjects following an oral glucose load

Impaired glucose tolerance (IGT) is a risk-factor for future development of T2DM. Diagnosis of IGT in the pre-diabetes phase of T2DM primarily occurs by means of an oral glucose tolerance test (OGTT). The aim of this study was to characterize the kinetics of glucose-derived breath CO2 between drug naïve IGT and NGT (normal glucose tolerance) individuals following an oral glucose load. Blood and breath samples were collected at baseline and every 30 minutes for a 10 h period following ingestion of 75 g of glucose isotopically labeled with 150 mg of U-13C6-Glucose. Age (47 ± 3 vs. 48 ± 5 y) and BMI (30 ± 2 vs. 34 ± 3) were similar between IGT and NGT, respectively. Blood glucose concentrations were significantly higher in IGT compared to NGT from baseline to 4.5 h post-glucose ingestion (P≤0.05). Glucose-derived breath 13CO2 was significantly lower in IGT as compared to NGT from 0.5 to 3.5 h post-glucose (P≤0.05). Peak breath 13CO2 abundance occurred at 4.5 and 3.5 h in IGT and NGT, respectively (33.93 ± 4.81 vs. 41.36 ± 1.97 ‰ delta over baseline). No differences were measured between IGT and NGT in 13CO2 abundance from 4 to 10 h. These results suggest that glucose-derived breath CO2 kinetics measured during the immediate post-glucose ingestion period (0.5 to 3.5 h) may assist in recognition of undiagnosed IGT in at-risk individuals during the pre-diabetes stage of T2DM. This study was supported by NIH grant R43 DK072637 awarded to BioChemAnalysis Corporation (M.J. and M.S-M).