Cerebral Glucose Transport and Metabolism in Preterm Human Infants

Abstract

Few data regarding early developmental changes in cerebral (blood-to-brain) glucose transport (CTX_glc) and CMR_glc are available for humans. We measured CBF, CTX_glc, and CMR_glc with positron emission tomography at 4 to 7 days of life in six preterm human infants whose estimated gestational age was 25 to 34 weeks. The Michaelis-Menten constants K_t and T_max were estimated from CTX_glc and the calculated cerebral capillary plasma glucose concentration. Mean CMR_glc was 8.8 μmol 100 g⁻¹ min⁻¹. The CMR_glc did not correlate with plasma glucose concentration (r = .315, P = .543), whereas CTX_glc showed a significant correlation with plasma glucose concentration (r = .836, P = .038). Estimation of the Michaelis-Menten constants from the best fit to the measured data produced values of K_t = 6.0 μmol mL⁻¹ and T_max = 32.6 μmol 100 g⁻¹ min⁻¹. These values for K_t in the developing human brain are similar to those that have been reported for the mature brain of adolescent and adult humans and adult nonhuman primates, indicating the affinity of the glucose transport protein for d-glucose is similar. However, T_max is approximately one third to one half of the comparable values for mature brain, indicating a reduced number of available luminal transporters.