Quantitative Estimation of Systemic Glucose Production in Normal and Diabetic Pregnancy

Fasting during pregnancy is accompanied by a decline in plasma glucose and glycogenic amino acid concentration and an early recruitment of alternate fuel by mobilizing fatty acids from adipose tissue stores. Systemic glucose production rates were measured in normal, gestationally diabetic, and juvenile-onset diabetic subjects using (1-¹³C)glucose and (6,6-²H₂)glucose tracers according to the constant-rate infusion technique. Even though the plasma glucose concentration during normal pregnancy had declined after an overnight fast, as compared with the nonpregnant subject (P < 0.0005), the systemic glucose production rate was 16% greater, a rate sufficient to provide the glucose requirement of the fetus at term gestation. The decline in glucose concentration could be the result of an increase in apparent volume of distribution of glucose. Systemic glucose production rates in well-regulated gestationally diabetic and insulin-dependent diabetic subjects were similar to those in normal pregnant subjects. These data suggest that the early disturbance in diabetes is the inability to assimilate exogenously administered glucose and other nutrients. Hormonal-fuel relationship during pregnancy suggests that during fasting, the insulin/glucagon molar ratio is maintained similar to that in nonpregnant subjects. Adrenal catecholamines do not appear to play a significant role in the regulation of hepatic glucose production. However, their role may be important in the early recruitment of alternate fuels.