11 January 2022

Sugar and the psyche

It's all about balance

"First-hand science"

The brain is one of the most energy–consuming organs of the human body, and glucose is practically the only "fuel" for it. However, excess sugar in the diet, especially at a young age, can negatively affect mental health, which was confirmed by experiments on laboratory mice.


In modern society, people have the opportunity to consume a lot of sweets, and they take full advantage of it. The consequence of such a hobby may be not only obesity, diabetes mellitus or kidney disease. It is known that people with mental disorders consume twice as much sugar on average as healthy people of the same age, and patients with schizophrenia who eat more sweets have more serious symptoms.

Increased consumption of sweets is also characteristic of adolescents, and mental pathology often starts at a young age. But the causal relationship between excessive sugar consumption and the development of mental disorders, including in young people, has not been scientifically proven.

Recently, Japanese scientists have modeled the effect of sweets on the psyche at an early age in experiments on laboratory mice in which one of the two genes determining predisposition to mental disorders was "disabled".

The first of them, DISC1 (Disrupted–in-Schizophrenia-1, i.e. "disturbed in schizophrenia-1"), plays an important role in the development of the nervous system. The second encodes glyoxalase I, an enzyme that protects cells from toxic products of the glycation process (interactions of proteins, lipids and nucleic acids with carbohydrates).

The formation and accumulation of such products is associated not only with tissue damage in diabetes mellitus, as previously thought, but a whole range of pathological conditions. In particular, they contribute to the development of inflammation and oxidative stress, which is often noted in patients with mental disorders, as well as a reduced level of glyoxalase I.

4 groups of mice were used in the experiment. The control "normal" mice received food where starch was the main carbohydrate; another group received food with sucrose, which modeled the "sweet overeating" factor. The third group included mice with one "off" allele of the glyoxalase I gene (or Disc1) on a diet with starch, the fourth group included the same mutant animals, only on a diet with sucrose. These latter were influenced by genetic and environmental provoking factors at the same time.

Mice ate special food from the "teenage" age of three weeks, and behavioral tests were carried out from the "adult" age of 2.5 months.

As the tests showed, the largest changes in behavior were demonstrated by animals from the 4th group, which had the corresponding mutations and overeated sweets. Hyperactivity, memory and sensory processing disorders, as well as other pathological effects were noted in them. At the same time, morphological and pathophysiological changes were detected in the tissues and vessels of the brain of these mice.

As the researchers found out, food with a high sucrose content causes the accumulation of glycation products in the cells of the neuroglia (auxiliary tissue) and endothelium (inner lining) of the vessels of the brain. Normally, these cells are protected by glyoxalase I, but with its deficiency, inflammation and damage to the vascular network of the brain occurs – angiopathy. This makes it difficult for nutrients to enter the brain, which leads to neuron dysfunction and behavioral disorders.

Scientists confirmed their findings by finding similar signs of vascular damage in postmortem brain samples of patients with schizophrenia and bipolar disorder. Perhaps it is brain angiopathy that has developed under the influence of various factors that can trigger the development of psychiatric diseases. And the love of sweets could play an important role in this scenario.

In this case, scientists also managed to find an "antidote" that prevented the formation of pathological behavior in mice with a glyoxalase I gene mutation that ate a lot of sweets. It turned out to be an ordinary, well–known drug - aspirin. Already small doses of this popular medicine suppress inflammation and oxidative stress, protecting the brain from the development of angiopathy.

Article by Hirai et al. High-sucrose diets contribute to brain angiopathy with impacted glucose uptake and psychosis-related higher brain dysfunctions in mice published in the journal Science Advances.

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