A team of researchers from HSE University, the RAS Research Centre for Medical Genetics, and the Moscow State University Institute of Anthropology have examined the impact of the human genotype on the production of trehalase, an enzyme responsible for metabolising 'mushroom sugar'. The researchers examined 1,068 DNA samples collected from inhabitants of northern and Arctic regions of Russia and found that the overall risk of trehalase deficiency in certain indigenous northern populations can be as high as 60–70%. According to the authors of the paper, this discovery holds significant implications for the diagnosis and treatment of eating disorders and obesity, particularly in children from these indigenous communities. The paper has been published in Problems of Nutrition.
Trehalose, often referred to as 'mushroom sugar,' is a natural carbohydrate present in fungi, lichens, algae, certain plants, and yeast. Its primary role is to protect cells from damage caused by factors such as dehydration, cold, oxidation, and more. An individual may come in contact with trehalose while consuming mushrooms and certain foods where it serves as a sweetener or thickening agent.
Trehalose consists of two D-glucose molecules linked by a glycoside chemical bond. Trehalose can be absorbed through the intestinal wall only after being acted upon by the enzyme trehalase, which breaks down the complex sugar into two glucose molecules that can be readily digested.
For absorption to occur normally, an adequate amount of the trehalase enzyme must be produced. If this doesn't occur, trehalose remains undigested, potentially leading to discomfort, bloating, diarrhoea, and overall malaise. A reduction in the chemical activity of the enzyme is referred to as a trehalase deficiency, and this condition is genetically inherited. Depending on the combinations of alleles in the gene, the trehalase enzyme’s activity varies. Individuals with the AA*TREH genotype exhibit nearly three times lower enzyme activity compared to GG*TREH carriers, while those with the GA genotype have intermediate and moderately reduced trehalase activity.
A team including HSE researchers uncovered the geographical distribution of genotypic frequencies responsible for trehalase production within the populations of Siberia and the Russian Far East. In total, the researchers collected and analysed 1,068 DNA samples from members of ethnic groups such as Ob Ugrians (Khanty and Mansi) of the Northern Ob region, Yamal Nenets, Evens and Evenks of Eastern Siberia, Nanais and Nivkhs of the Amur, as well as Itelmen, Koryaks and Chukchi of Northern Kamchatka. Additionally, two reference groups were included: one comprising ethnic Russians from the temperate climatic zones in European Russia and Siberia, and the other consisting of Yakuts.
The study revealed that among the examined indigenous Northerners, the GA*TREH genotype, which is associated with a 1.5-fold decrease in trehalase activity, was present in a range of 19.8% to 53.7%. Individuals carrying this genotype may experience feelings of malaise and discomfort when consuming mushrooms. Furthermore, up to 20% of Northerners who carry the AA*TREH genotype may experience severe intestinal pain after consuming mushrooms. The prevalence of the 'risky' AA*TREH genotype increases from 1% in Ob Ugrians to 18–20% in Evens, Evenks, and Nanais, and ranges between 10% and 19% in the indigenous populations of the Lower Amur, Kamchatka, and Chukotka. The overall risk of trehalase enzymopathy among indigenous Northerners in the Asian part of the Russian Federation is exceptionally high, reaching 60–70%.
It is essential to note that the studied populations live in remote regions and had, until the first quarter of the 20th century, maintained their traditional ways of life and dietary habits. In cold environments with limited access to carbohydrate-rich foods, the indigenous northern peoples evolved a diet centred around reindeer husbandry, hunting, and fishing. Considering the minimal presence of dietary sugars in the traditional diets of Northerners, saccharidase enzymes played a secondary role, potentially reducing genetic regulation over the maintenance of enzyme activity responsible for breaking down di- and polysaccharides, including trehalase.
According to the authors of the paper, trehalase deficiency is a concern that warrants the attention of specialists in the fields of nutrition, gastroenterology, public health, and medical genetics, particularly those practicing in high-latitude regions.