Fasting plasma levels of glucose, acetoacetate, d-β-hydroxybutyrate, glycerol, and lactate in the baboon infant: Correlation with cerebral uptake of substrates and oxygen

Abstract

The energy-rich substrates available to the fasting stressed baboon neonate tnd infant are quantitatively similar to the metabolic fuels presented to the stressed low birth weight human newborn. Within a few hours after birth, fasting arterial plasma glucose levels in the baboon neonate approximate those of 4-6- week-old baboon infants after a 20-hr fast. Lactate levels are high and comparable for both age groups. In contrast, β-hydrox- ybutyrate is quite low in the immediate neonatal period, but rises to significantly higher levels (P < 0.001) after a fast at 4-6 weeks. In addition, glycerol levels are higher (P < 0.02) in the fasted older infant compared with the fasting neonate. Computation of mean cerebral blood arteriovenous differ-ences and oxygen equivalents for animals studied in the first 50 hr of life demonstrates that glucose uptake can account for 50% or less of cerebral oxygen consumption in the newborn period. In confirmation, the respiratory quotient in these animals is 0.52 ± 0.06. Cerebral oxygen consumption in the immediate neonate is greater than can be explained by utilization of glucose and the small quantities of acetoacetate and β-hydroxybutyrate available at this time. At birth, cerebral uptake of lactate is noted, but this phenomenon is not observed at 6 and 12 weeks of age. Speculation: The baboon model for dynamic studies of neonatal energy metabolism may permit investigations of greater clinical relevance than those in lower mammalian model systems. It is suggested that lactate may be a significant cerebral energy source in the immediate neonatal period. © 1977 International Pediatric Research Foundation, Inc.