High-fat diets decrease the glucose uptake in brain cells, says a study published in Cell.
High-fat foods are known to be generally unhealthy to the human body. A new study provides further data about the extent of the harm: this type of diet disrupts the sugar uptake in the brain, the restoration of which comes with a heavy price to pay.
The researchers, led by Jens Brüning, the Director at the Max Planck Institute for Metabolism Research in Cologne, fed mice with foods rich in fat for three days with the aim of gaining more insight into the development of obesity and diabetes. This led to a decrease in the glucose level reaching the brain.
The effects of the high-fat diet was felt in only 3 days’ time, points out Alexander Jais, one of the authors. It decreases the uptake of blood glucose in the brain such that the latter is left starving in spite of the fact that the mice have been consuming a great quantity of calories. Looking deeper into the matter shows that the most important protein carrier of glucose, the GLUT-1, was reduced in number; since the channels allowing the passage of glucose into the brain cells were fewer, the brain did not receive its normal amount of the nutrient. The decrease in GLUT-1 might possibly be promoted by saturated fatty acids roaming free in the blood.
The researchers were also able to point out the specific brain areas that lacked glucose, namely the hypothalamus, and the cerebral cortex. The former is known to monitor metabolism while the latter is associated with memory, and learning processes.
Now, what does the brain do when undergoing this stress situation? It calls for macrophages from the immune system to produce growth factor VEGF which, in turn, enhances the synthesis of GLUT-1, and boosts the carrier’s function. The GLUT-1 is then placed directly at the endothelial cells of the blood-brain barrier. It takes 4 weeks for the glucose levels in the brain to be back to normal. However, if the mice do not have the VEGF, the brain has to stay starved of glucose, which leads to memory and learning impairment, explains Jais.
How does this contribute to the development of diabetes? According to Jais, it is because of the “selfishness of the brain”. When glucose-deprived, the brain enhances appetite for sweet foods so that it obtains glucose, and at the same time, the glucose uptake in muscles is inhibited. This causes muscle cells to become insulin-resistant which can pave the way for diabetes.