Abstract
Glucose is the primary substrate used by the infant brain either as a source of energy or for lipid and amino acid synthesis. The in vivo conversion of glucose U-14C, 2.5 μCi/60 g of body weight injected intraperitoneally, to lipids and amino acids was measured in the brains and livers of poorly nourished and control infant rat pups at ages 6, 10, 17, and 24 days, and in adult animals fed a control or 8% protein diet for 3 months. Brain lipid formation was decreased 50 to 75% from ages 6 to 17 days, and brain amino acid formation was reduced 60% in 10-day-old rat pups. Reduced in vivo hepatic conversion of glucose U-14C to lipids and amino acids was found only at ages 6 and 10 days. In vitro production of 14CO2 from glucose U-14C incubated with brain slices was not altered in 10- or 20-day-old malnourished animals (1.58 ± .26 vs. 1.14 ± .07). Brain ATP, phosphocreatine, and glycogen levels were not reduced at either age 10 or 20 days. Mitochondrial glutamate dehydrogenase activity catalyzes the formation of amino acids from α ketoglutarate in Krebs cycle, and was reduced 21 to 30% in the brains of malnourished animals, and 49 to 81% in the livers. Supernatant NADP-isocitric dehydrogenase activity, believed to produce TPNH for lipid synthesis, was not reduced in the brains, but was reduced in the livers of malnourished infant rats. Pyruvate kinase, one of the rate limiting enzymes of glycolysis, showed reduced activity in liver and muscle of malnourished animals, but not in brain. Decreased glucose utilization in the brains of malnourished animals may explain the previously described alterations in lipid and protein synthesis resulting in permanent brain structural deficits.
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Chase, H., Kumar, V., Rodgerson, D. et al. Brain glucose metabolism in undernourished rats. Pediatr Res 5, 372–373 (1971). https://doi.org/10.1203/00006450-197108000-00008
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DOI: https://doi.org/10.1203/00006450-197108000-00008