(13)C-glucose breath tests: a non-invasive method for detecting early clinical manifestations of exogenous glucose metabolism in type 2 diabetic patients

AIMS: (13)C-glucose breath tests are reported as an alternative non-invasive method to evaluate glucose metabolism. However, the metabolic results differ based on the site of the carbon atom in the glucose. The aim of this study was to evaluate changes in the metabolism of carbon atoms contained in glucose in patients with diabetes using [1, 2, 3-(13)C]glucose breath tests. METHODS: Sixteen healthy participants and 20 diabetic patients were enrolled in the study. Three types of breath tests, [1-(13)C], [2-(13)C], and [3-(13)C]glucose breath tests, were performed after an overnight fast. Breath samples were taken at baseline and at 10-min intervals over 150 min, and (13)CO(2) excretion curves were expressed using non-dispersive infrared isotope spectrometry. RESULTS: (13)CO(2) levels increased more rapidly, and the peak value of (13)CO(2) (C(max)) was highest after the administration of [3-(13)C]glucose followed by [2-(13)C] and [1-(13)C]glucose in controls. Delayed (13)CO(2) excretion and a low area under the curve through 150 min (AUC(150)) were obtained in diabetic patients. The group with severe diabetes had a significantly lower C(max) and AUC(150) in the [1-(13)C]glucose breath test. CONCLUSIONS: The [1-(13)C]glucose breath test, which has been used to evaluate glucose metabolism, is suitable for patients with late-stage diabetes, whereas the [2-(13)C]glucose breath test is ideal in the early stages. Although the [3-(13)C]glucose breath test is theoretically useful for evaluating the uptake of glucose and the anaerobic glycolysis system, it can be used in practice to distinguish reduced uptake from impaired oxidation of glucose in combination with the other two tests.