High-fat foods make the brain go hungry

Saturated fats end up ingesting sugar at the blood-brain barrier

With high-fat food, our brain gets sugar shortage - despite enough calories. © Sebastian Kaulitzki / thinkstock
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Paradoxic Effect: If we eat high in fat for a few days, our brains will remain hungry - although we consume plenty of calories. For the thinking organ gets too little sugar supply, as now prove experiments with mice. The reason: The ingested fat inhibits a transporter protein that normally carries sugar through the blood-brain barrier. As a result, the important energy supply for our brain remains, as the researchers report in the journal "Cell".

Too much fat is unhealthy - studies prove that for some time. Just a few days of high-fat food can affect the metabolism of our muscles and disrupt our inner clock, and in the longer term, eating fat increases the risk of overweight, diabetes and even breast cancer.

Sugar shortage after only three days

But what does a high-fat diet actually do with our brains? To find out, Jens Brüning from the Max Planck Institute for Metabolism Research in Cologne and his colleagues looked at mice in the brain. For their study, they fed mice with a high-fat diet for several days. Before and after, they used positron emission tomography (PET) to study the uptake of glucose into the brain.

Cross-section through the mouse brain: Regions with reduced glucose intake after three days of fat diet (blue: weak, white: strongly reduced) © MPI f. Substances change research

The result: Already after three days with fat food, a supply shortage in the brain was shown. "A high-fat diet lowers the intake of glucose in the brain. The brain is starving, even though the mice consume many calories each day, "says Alexander Jais of the MPI for Metabolism Research. The glucose is thus absent in some important regions of the brain: in the hypothalamus, which controls the metabolism and in the motor and sensory areas of the cerebral cortex.

Saturated fatty acids inhibit transporters

But how is this supply shortage to be explained? To answer this question, the researchers investigated how the blood serum of high-fat fed mice affects cells of the blood-brain barrier - the barrier that engulfs the brain from unauthorized intrusion erer molecule protects. Glucose from the blood can only happen if a certain transporter protein, GLUT-1, passes it through this barrier. display

However, this transport is blocked on high-fat diets, as the researchers observed. Saturated fat acids present in the blood serum inhibit the GLUT-1 transporter and thus prevent the glucose from entering the brain. "Especially the palmitic acid, which is more abundant in the circulation of overweight mice, acutely inhibits glucose uptake, " report Br ning and his colleagues.

Antidotes with fatal consequences

But there is an antidote: If the high-fat diet lasts for several weeks, the sugar intake of the brain normalises again because the brain actively counteracts its lack of energy. As the researchers discovered, the brain then stimulates macrophages of the immune system to produce the growth factor VEGF. This causes at the blood-brain barrier that more of the transporter GLUT-1 is formed.

In the experiment, the mouse brain thus restored its sugar level after four weeks - but at the expense of the rest of the body. "It's called the selfish brain because it gets its sugar by stimulating its appetite for sweet foods and preventing sugar absorption in muscle and fat, " Jais explains.

In the long term, however, this can have fatal consequences for your health. The brain-triggered metabolism leads to the fact that the cells in the muscles gradually become resistant to the body's own hormone insulin. "This can lead to diabetes in the worst case, " says Jais. The mechanism discovered by him and his colleagues also explains why high-fat nutrition can lead to diabetes over time. (Cell, 2016; doi: 10.1016 / j.cell.2016.03.033)

(Max Planck Society, 29.04.2016 - NPO)