To evaluate the effects of gestational hyperglycemia on glucose metabolism and its regulation in the fasted rat during the early postnatal period, unrestrained rats were continuously infused with glucose during the last week of pregnancy. Control rats were infused with distilled water. Newborns were studied during the first six postnatal hours.
At birth, newborns from glucose-infused rats, compared with controls, showed higher plasma glucose levels, increased plasma insulin, and lower plasma glucagon and catecholamine concentrations.
Between birth and 2 h postpartum, newborn rats from both groups exhibited a marked hypoglycemia, which was, however, more severe in newborns from glucose-infused rats (15 mg/dl) than in controls (26 mg/dl). During the first four postnatal hours, plasma insulin concentration remained higher, while plasma glucagon and catecholamine concentrations remained lower in newborns from hyperglycemic rats. At 6 h, the glycemia reached normal values and the concentrations of the different hormones were similar in controls and newborns from glucose-infused mothers.
Concurrently, in the newborns from glucose-infused rats, hepatic glucose production was altered, as they were unable to mobilize liver glycogen stores during the six postnatal hours. Despite slightly delayed phosphoenolpyruvate carboxykinase induction, the rate of gluconeogenesis from 10 mmol/L lactate estimated on isolated hepatocytes was higher in newborns from hyperglycemic mothers than in controls.
These results show that gestational hyperglycemia compromises the metabolic and hormonal adaptation of the newborn rat to early extrauterine life; the striking feature of these neonates is the absence of mobilization of liver glycogen stores, which can probably be explained by fetal and neonatal hyperinsulinism associated with the defect of counterregulatory hormones.
