Formation of 14CO 2 and 3HOH from glucose-1- 14C, -1- 3H during oral cortisone glucose tolerance tests in obese patients

Abstract

Glucose-1- 14C was given to 10 nonobese and 19 obese adult female subjects in the oral load of a cortisone glucose tolerance test (CGTT); the extent of reduction of expiration of 14CO 2 in the obese was compared with the abnormality of the blood glucose concentration curve of CGTT and the k value of an intravenous glucose tolerance test (IGTT) in the same patients. In some patients glucose-1- 3H was also included in the oral load and the rate of formation of tritiated body water ( 3HOH) taken as a general measure of glucose utilization. Obese patients excreted only about half as much 14CO 2 as nonobese subjects during the first 90 min after ingestion and about two thirds as much after 3 hr. Calculation of total formed breath and body 14CO 2 indicated similar differences. At a time (2 hr) of maximum difference in blood glucose concentration in the CGTT that of the obese group was 25 per cent higher than that of the nonobese, with much less significance of difference than for the 14CO 2. The mean k value of the IGTT for the obese group was 60 per cent of that for the nonobese group. Within the obese group the reduction in total formed 14CO 2 was highly correlated with the nonisotopic parameters of glucose tolerance and was correlated to a lesser extent with parameters of obesity. Since formation of 3HOH from glucose-1- 3H was not significantly reduced in the obese group, the abnormality of metabolism of glucose-1- 14C in the obese patients appears to be a diversion of 14C to some organic products with concomitant decrease in formation of 14CO 2. The tritium data suggest no decrease in the absorption or overall initial utilization of glucose.