[Evaluation of glucose utilization in patients with insulin-independent diabetes mellitus by using breathing test]

Commonly used clinical and biochemical parameters, such as the content of glucose, insulin, somatotropic hormone, triglycerides, lactate, pyruvate, and free fatty acids (FFA) in blood of practically healthy subjects and in patients with insulin-independent diabetes mellitus (IIDM), were compared with the parameters obtained by mass-spectrometric analysis of 13CO2 in expired air after 13C-glucose loading. It was shown that, as opposed to healthy subjects, the content of blood glucose and free fatty acids in patients with IIDM increased, the level of glucose dropped in progression upon short-term fasting, and the concentration of lactate changed both upon fasting and after the administration of small test doses of glucose. The use of the 13C-glucose breathing test (13C-GBT), which presupposes the loading of safe small doses of glucose enriched in 13C-isotope permitted one to reveal a number of novel quantitative diagnostic criteria for the evaluation of glucose metabolism in patients with IIDM: a decrease in the rate of 13C withdrawal as a constituent of expired carbon dioxide after the administration of 13C-glucose; a reduction in the amount of exogenous glucose metabolized to carbon dioxide; and increased oxidation of endogenous substrates participating in carbon dioxide formation. Small glucose loads proposed by the authors in 13C-GBT are safe for patients with diabetes mellitus and have no effect on the level of blood glucose in healthy persons. The parameters determined by noninvasive 13C-GBT are more sensitive for diagnosis than commonly used biochemical characteristics of blood in patients with IIDM. The diagnostic criteria obtained allow the prediction of the maximum prohibited glucose loading for every patient.