Postnatal profiles of glycogenolysis and gluconeogenesis are modified in rat pups by maternal dietary glucose restriction.

Because glucose is an important metabolic fuel during perinatal development, the effect of restriction of maternal dietary glucose on the developmental profile of neonatal glucoregulatory pathways was investigated. Pregnant rats were fed isoenergetic diets (0, 12, 24 or 60% glucose) and offspring were killed at seven postpartum time periods: 0-2, 4-6, 12-16 and 24 h, and 3, 6 and 15 d. Failure of the most restricted pups (0%) to survive 24 h was explained by persistent hypoglycemia resulting from the following: 1) insufficient tissue glycogen reserves at birth; 2) lower liver glycogen mobilization; 3) delayed phosphorylase a induction; and 4) low phosphoenolpyruvate carboxykinase (PEPCK) gene expression, all of which occurred despite the lower insulin:glucagon ratio. Differences in liver glycogen stores, which had been exhausted in all dietary groups by 16 h, could not account for the high d 1 pup mortality in the moderately restricted (12 and 24% glucose) groups. However, a certain metabolic distress was suggested because these moderately restricted neonates had significantly higher liver PEPCK gene expression at 12-16 h but significantly lower plasma glucose at 24 h. The high d 3 mortality, confirmed by analysis of deviance, was not supported by significant differences in any of the measured glucoregulatory indices. We conclude that dietary glucose during pregnancy is required for neonatal survival; its restriction not only lowers tissue glycogen reserves, but can disrupt the normal gene expression of liver PEPCK and the neonatal profile of phosphorylase a activity. Importantly, these observations show that the development of neonatal glucoregulatory mechanisms is modified by the availability of maternal dietary glucose.