Enhanced Cerebral Substrate Pools in the Fetus and Neonate of the Diabetic Canine Mother

Energy stores and intermediates of carbohydrate metabolism were investigated in the freeze-clamped cerebral cortex of the fetus and fasted neonate born to a diabetic canine mother. Prior studies in these same pups demonstrated circulating hyperinsulinemia, depressed free fatty acid levels, and attenuated gluconeogenesis. Hepatic and muscle tissue also demonstrated augmented levels of glycogen, triglycerides, and amino acids. In the present investigation, cerebral tissue from these same pups of diabetic mothers also demonstrated enhanced fetal cerebral glucose and glycogen content. After 24 h of neonatal fasting, cerebral glycogen content declined to values lower than in control pups. Cerebral cortical levels of glucoses-phosphate, fructose-6-phosphate, lactate, citrate, α-ketoglutarate, and malate were not altered, while oxaloacetate as higher at 3 and 9 h and fructose-1,6-diphosphate was higher at 9 and 24 h in the IDM pups. Adenine nucleotide levels and the energy charge were equivalent to those in control pups at each time interval. In contrast, cerebral cortical amino acids of the glutamate group were enhanced in the fetus or neonate of the diabetic mother. Cerebral cortical alanine was increased from 3 to 24 h while aspartate and glutamate were augmented in the fetus and fasted IDM newborn pup. Glutamine was increased at 6 and 24 h, while 7-aminobutyrate was elevated in the fetus. Cerebral ammonia concentration was not altered. The augmented stores of cerebral carbohydrate and amino acid pools in the fetus and neonate after maternal canine diabetes may serve as oxidizable substrates for the brain during periods of attenuated systemic fuel availability. This may explain, in part, the paucity of neurodevelopmental sequelae in the hypoglycemic human infant of a diabetic mother.