Glucose war between brain and brawn—the hidden battle in children that made us human

John Skoyles in MedicalXpress:

The Proceedings of the National Academy of Sciences recently published a paper that showed a close link between the slow growth of children and the high glucose consumption of their brains. The proposed explanation: by saving on energy that would be spent on growth, children could devote more glucose to their brains. This week the Proceedings published a response which suggested an alternative theory: that slow growth is part of a package of adaptations to prevent skeletal muscle competing against the brain for plasma glucose.

Background to this science is that one of the most important biological things about us is nearly impossible to research—the metabolism of the brain in children. The brain of the child can be pictured in exquisite detail with MRI scans, but what is metabolically going on in it? Scientists can take a peak with radioactive tracers but ethics limits that to the very few occasions in which such a look is justified by medical need. The limited research that has been done reveals a brain quite unlike that of the adult or infant. Its energy guzzling—the cerebral cortex using twice the glucose that it did use in its first year after birth or that it will use in its twenties. The explanation is that the young child doubles the component of the brain that burns the most energy—the synapses that connect neurons. That doubling is called exuberance—that excess allows the brain to prune down its connections during development to those that best enable the wiring required for adult cognition. This refinement is a key part of neuromaturation. And it creates a big physiological problem. A five-year-old has nearly the same volume of gray matter as an adult but only a body a third of its size. That results in nearly half of every bit of food going to fuel its energy demanding brain—in adults it is nearer a tenth.

More here.