FUEL OXIDATION BY INSULIN-DEPENDENT DIABETICS DURING LATE PREGNANCY IN RESPONSE TO AN ORAL GLUCOSE-LOAD

1. To determine the oxidative response to a 50-g oral glucose challeng e by diabetic women during late pregnancy under a more intensive thera peutic regimen than is conventionally employed, six normal pregnant wo men and ten insulin-dependent pregnant diabetic women were studied dur ing the third trimester. Fuel (carbohydrate and lipid) oxidation rates were determined by indirect calorimetry, blood levels of substrates a nd C-peptide were measured directly, and glucose metabolism data (oxid ation and nonoxidative metabolism) were estimated for both groups at t he postabsorptive state and for the 2-h period following glucose inges tion. 2. The increases in the non-protein respiratory quotient (npRQ) and carbohydrate oxidation rates in response to glucose ingestion in t he diabetic pregnant group were significantly smaller than in the norm al pregnant individuals. The total amount of glucose oxidized by the d iabetic pregnant group during the 2-h tests (6.1 +/- 0.6 g/m2) was sig nificantly smaller than that oxidized by the normal pregnant group (8. 3 +/- 0.4 g/m2), whereas there was more but not statistically signific ant lipid oxidation in the diabetic group (3.0 +/- 0.3 vs 2.6 +/- 0.1 g/m2). 3. The diabetic pregnant group not only oxidized less glucose ( 10.9 +/- 1.1 vs 14.1 +/- 0.8 g, P < 0.05) but more of this hexose rema ined in their glucose space (9.1 +/- 1.6 vs 3.2 +/- 1.1, P < 0.05) and they excreted 2.8 +/- 1.0 g into the urine. 4. The diabetic pregnant subjects had significantly lower blood levels of lactate, pyruvate and C-peptide than the normal pregnant subjects, but significantly higher blood levels of glucose, beta-hydroxybutyrate and acetoacetate. 5. Th e present data show that an intensive conventional therapeutic regimen during late pregnancy was not sufficient to completely normalize the glucose-processing capability of insulin-dependent diabetic patients.