Cerebral glucose transport and metabolism in preterm human infants

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.