Brain uses glucose for acquiring energy / ATP. Is it that brain cannot use any other source- protein or lipid? Or is it that brain (neurons) ‘prefer’ glucose and use other sources as well but in relatively small proportion? Is it that the enzymes required for metabolizing protein and lipids are not expressed in neurons?
Aajkal outsourcing ka jamana hai. Neurons have outsourced fatty acid metabolism (beta oxidation) to glial cells astrocytes. This decision was taken in high level meeting considering all pros and cons. Few of the cons of beta oxidation in neurons may cause: Lower transport of fatty acids across Blood-brain barrier; accumulation of some intermediate products, leading to apoptosis in neurons; consumption of more oxygen-means hypoxic brain; slower rate of ATP production than from glucose etc.
After 3 days of starvation: At this time, the brain begins to consume appreciable amounts of acetoacetate in place of glucose. After 3 days of starvation, about a third of the energy needs of the brain are met by ketone bodies. The heart also uses ketone bodies as fuel.
Thanks to Dr Shanker Jha