Abstract
Ketones become the major source of energy for brain metabolism during prolonged fasting. The energy-yielding conversion of β-hydroxybutyrate to acetoacetate is catalyzed by the substrate-inducible enzyme, BDH. The capacity of fetal brain for utilization of β-hydroxybutyrate, and effects of maternal starvation on development of BDH activity in immature brain were studied in rat fetuses, and in newborn rats and rabbits. In rats, BDH activity appeared on the 17th day of gestation, and tripled within 2 days. A second rise in BDH began 12 hours after birth, doubling activity by 48 hours. BDH developed more rapidly in fetuses from pregnant animals fasted for 3 days. At 21 days gestation, their activity was 42.5 ± 6.4 units compared with 24.7 ± 4.3 units in fetuses from fed controls. At birth offspring of fasted rats had approximately twice the BDH activity of normal newborns. When the former were nursed by fed animals, BDH activity decreased to normal values within 24 hours. Normal rabbits fasted for 24 hours after birth had 130% higher BDH activity than fed littermates. These results show that fetal and newborn brain can utilize ketones. The development of this capacity is accelerated by maternal or postnatal starvation. Thus, the immature brain appears extremely responsive to qualitative changes in nutrients before and after birth.
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Thaler, M., Chait, M. In utero induction and development of brain β-hydroxybutyrate dehydrogenase (BDH). Pediatr Res 5, 373 (1971). https://doi.org/10.1203/00006450-197108000-00009
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DOI: https://doi.org/10.1203/00006450-197108000-00009