Fats are essential for normal growth and metabolism, but the negative effects of eating fatty foods are much better known. Researchers at the Institute of Bioorganic Chemistry of the Russian Academy of Sciences, along with colleagues from the Moscow State University School of Biology, studied the effect of a high-fat diet on the brains of young mice.
The work examined in detail the changes that primarily affect astrocytes and the neuroplasticity that depends on them. Astrocytes play an extremely important role in the metabolism of lipids in the brain: they are actively involved in the synthesis of styrene lipids that are necessary for the normal functioning of neurons and can deposit fats in lipid droplets in the cytoplasm. Astrocytes perform many other functions aimed at maintaining homeostasis in the brain and providing conditions for neuronal function, so it is reasonable to assume that changes in diet will affect them first.
The authors of the study showed that after a month on a diet rich in fat, in young (2-3 months old) mice, the spatial structure of astrocytic processes became more complex, which allowed them to interact better with synapses and capture more effectively glutamate, preventing leakage and inhibiting activation, neighboring synapses. At the same time, the amount of lipids in the astrocytes increased and the redox status of the mitochondria changed, while no significant metabolic changes occurred in the neurons.
Such an increase in the presence of astrocytes in the active environment of the brain and increased efficiency of their work (reactive astrogliosis) accompanies a number of pathological processes. Previous studies have described an association between reactive astrogliosis and increased expression of GFAP (glial fibrous acid protein, glial fibrous acid protein is one of the cytoskeletal proteins most characteristic of certain subpopulations). However, no such trend was observed in mice on a high-fat diet. The authors attribute changes in the structure of astrocytes to another structural protein, ezrin, whose expression levels were elevated in the astrocytes of animals fed a fatty diet.
Changes in the metabolic characteristics of astrocytes and the structure of their processes were accompanied by complex changes in the behavior of mice, which was demonstrated in a series of experiments. For example, in the Open Field test (a mouse is placed in an arena where there are no shelters), animals kept on a high-fat diet spent more time in the center of the field compared to the control group. this shows more curiosity and less stress.
“There are many different diets high in fat,” said Alexei Semyananov, Ph.D. For example, there is a ketogenic diet that is considered beneficial at different times of life and there are diets that are considered harmful – these are diets rich in fat and sugar, which lead to obesity and generally adversely affect the whole body. This notion has created the idea that fat is bad in general, although this contradicts the knowledge of the brain metabolism in general, as fat is an important metabolic component used both for energy and as a building block.
As Semyananov noted, the innovation of the obtained results lies mainly in the description of the positive effect of increased fat intake on the brain and the cognitive abilities of animals in the early stages of development. Over a month on a fatty diet, the mice gained weight faster than the control group without becoming obese and performed better on a behavioral test. However, for animals of different ages or animals that are kept on the same diet for a longer period of time, the result may be different. The team plans to compare the effect of high fat content on the condition of animals of different ages.
“Now this is a key moment for us: one stage is when the brain develops and needs additional building materials and energy, another is when the brain is already formed and the third is when any processes related to the aging of the brain begin. In all these cases, the way of physical activity and diet can affect in different ways, explains Alexei Semyananov. “This is one of the fundamental questions, because some nutritionists suggest that a diet can be unquestionably good or bad, although in reality it all depends a lot on the biological context: age, lifestyle and other factors.”