Development of enzymes of energy metabolism in the neonatal mammalian brain.

The metabolic capability for the complete oxidation of glucose, i.e. aerobic glycolysis, is highly developed in the brains of neurologically mature (precocial) species at birth, whereas this activity is severely limited in the brains of neurologically immature (non-precocial) species such as the rat and human. The latter utilize a mixture of glucose and ketone bodies for synthetic and energetic activities and the advent of neurological competence associated with the capability for complete dependence on and oxidation of glucose must await the development of key enzymes such as the pyruvate dehydrogenase complex (PDHC). A similar relationship appears to exist with respect to the development of neurological maturity of different brain regions in a single species, the rat. The development of the enzymes of energy metabolism of neonatal rat brain will be discussed with respect to the energy fuels available to the neonatal brain. In particular mechanisms by which the PDHC develops in neonatal brain will be evaluated. Evidence suggests that this is due to a specific increase in enzyme protein in contrast to a general increase in mitochondrial activity.