To date, it has been established that the patient's genotype plays a significant role in the formation of trehalase enzymopathy: the level of enzyme activity decreases when the G→A allele replacement occurs in the rs2276064 locus of the TREH gene. To assess the prevalence of trehalase deficiency, extensive population-based studies are needed. Clinical observations show that the reduced activity of bowel trehalase is more common in the Arctic than in European populations. The aim of this research was to analyze the frequency of the alleles and variants of trehalase gene (rs2276064 TREH) in the indigenous small-numbered populations of Siberia and the Russian Far East. Using the Infinium iSelect HD Custom BeadChip biochip (Illumina, United States) on the iScan platform and real-time polymerase chain reaction on a Bio-Rad CFX96 Touch amplifier, genotyping of 1068 DNA samples was carried out, of which 667 represent 10 ethnic groups of the indigenous people of the North of Siberia and the Far East of the Russian Federation. Two reference groups (357 samples) of Russians (n = 311) and Yakuts (n = 46) represent the "Caucasoid" and "Mongoloid" poles of the Russian population. The reduced trehalase activity that the heterozygous GA*TREH genotype determines can manifest itself in 19.8-53.7% of indigenous northerners. An additional 1.0 to 19.7% of the population are carriers of the AA*TREH genotype, which is associated with apparent trehalose malabsorption. The carriers may experience nausea, abdominal pain, and other dyspeptic symptoms after eating trehalose containing foods. The total risk of trehalase enzymopathy among the indigenous northerners in the Asian part of the Russian Federation is very high and can reach 60-70%. There is a gradient in the A*TREH allele frequencies in the small-numbered indigenous northern groups of Russia from the west (Khanty, Mansi, Nenets) to the east (peoples of the Far East). The results are consistent with previously reported data on the higher carriage of the A*TREH mutant allele in Mongoloid populations compared to Caucasoid groups. It was hypothesized that, while the initial A*TREH allele prevalence in Mongoloid groups was moderately high, an adaptation to a low-sugar protein-lipid "high-latitude" diet led to a weaker control over the maintenance of the carriage of the ancestral G* allele. Trehalose malabsorption requires special attention of specialists in the field of nutrition, gastroenterology, public health, and medical genetics working in high-latitude regions.

To date, it has been established that the patient's genotype plays a significant role in the formation of trehalase enzymopathy: the level of enzyme activity decreases when the G→A allele replacement occurs in the rs2276064 locus of the TREH gene. To assess the prevalence of trehalase deficiency, extensive population-based studies are needed. Clinical observations show that the reduced activity of bowel trehalase is more common in the Arctic than in European populations. The aim of this research was to analyze the frequency of the alleles and variants of trehalase gene (rs2276064 TREH) in the indigenous small-numbered populations of Siberia and the Russian Far East. Material and methods. Using the Infinium iSelect HD Custom BeadChip biochip on the iScan platform and real-time polymerase chain reaction on a Bio-Rad CFX96 Touch amplifier, genotyping of 1068 DNA samples was carried out, of which 711 represent 10 ethnic groups of the indigenous people of the North of Siberia and the Far East of the Russian Federation. Two reference groups of Russians (n=311) and Yakuts (n=46) represented the "Caucasoid" and "Mongoloid" poles of the Russian population. Results. The reduced trehalase activity that the heterozygous GA*TREH genotype determines can manifest itself in 19.8-53.7% of indigenous northerners. An additional 1.0 to 19.7% of the population are carriers of the AA*TREH genotype, which is associated with apparent trehalose malabsorption. The carriers may experience nausea, abdominal pain, and other dyspeptic symptoms after eating trehalose containing foods. The total risk of trehalase enzymopathy among the indigenous northerners in the Asian part of the Russian Federation is very high and can reach 60-70%. There is a gradient in the A*TREH allele frequencies in the small-numbered indigenous northern groups of Russia from the west (Khanty, Mansi, Nenets) to the east (peoples of the Far East). Conclusion. The results are consistent with previously reported data on the higher carriage of the A*TREH mutant allele in Mongoloid populations compared to Caucasoid groups. It was hypothesized that, while the initial A*TREH allele prevalence in Mongoloid groups was moderately high, an adaptation to a low-sugar protein-lipid "high-latitude" diet led to a weaker control over the maintenance of the carriage of the ancestral G allele. Trehalose malabsorption requires special attention of specialists in the field of nutrition, gastroenterology, public health, and medical genetics working in high-latitude regions.

In order to be digested, the disaccharide trehalose needs to be cleaved by the trehalase enzyme. There were reports suggesting that trehalase deficiency was more common in high-latitude than in the temperate climate populations. New horizons were opened for the epidemiologic research of trehalase enzymopathy when it became clear that reduced trehalase activity is determined by the A allele of tTREH gene (rs2276064). The aim of this study was to analyze the frequencies of the trehalase gene alleles and genotypes among the indigenous peoples of Siberia and the Russian Far East. We genotyped 567 samples representing the indigenous peoples of Siberia and the Russian Far East and 146 samples representing Eastern Slavs as the reference dataset. We found that the frequencies of the A*TREH alleles increased to the east. The A*TREH allele frequency was 0.03 in the reference group, 0.13-0.26 in the North-West Siberian indigenous populations, 0.29-0.30 in the South Siberia, 0.43 in West Siberia, and 0.46 in the low Amur populations. The highest frequency of the A allele (0.63) was observed in the Chukchi and Koryak populations. From 1 to 5% of European origin individuals are at risk of trehalase enzymopathy. In the indigenous populations, the frequency of the A*TREH allele varies 13% to 63%, whereas the frequency of the AA*TREH genotype from 3% to 39%. Thus, the total risk of trehalase enzymopathy among the homo- and heterozygous carriers of the A*TREH allele in the studied indigenous populations may be as high as 24% to 86%.

There are currently three known congenital disaccharidase deficiencies: congenital lactase deficiency (CLD), congenital sucrase-isomaltase deficiency (CSD), and congenital trehalase deficiency (CTD). No congenital deficiency has been described for maltase-glucoamylase (MGAM). A literature search was performed in PubMed for the pathogenic variants CLD, CSD, and CTD and the articles retrieved were analyzed to estimate the prevalence of congenital disaccharidase deficiencies. Based on reported variants, the estimated prevalence was 1.3 per 106 births (95% CI: 1.1-1.7) for CLD, and 31.4 per 106 births (95% CI: 28.3-34.8) for CSD. Using data on previously reported variants and variants predicted to be loss-of-function in gnomAD, the overall estimated prevalence was 2.3 per 106 births (95% CI: 1.9-2.9) for CLD, 57.6 per 106 births (95% CI:52.5-63.2) for CSD, and 9.2 per 106 births (95% CI: 2.5-3.7) for CTD. The prevalence of CSD was found to be relatively high, while for other congenital disaccharidase deficiencies, the estimated prevalence was very low.

Due to the low specificity and sensitivity of non-invasive clinical tests trehalose malabsorption remained out of sight of gastroenterologists. Therefore, the specialists regard this disorder as rare. Trehalose became widely used in the food industry as a harmless sucrose substitute, sweetener and stabilizer. After the discovery of the trehalase gene (rs2276064 TREH), it was found that the A*TREH allele is the determinant of the disaccharide absorption disorders, and the allele's carriership may be high in some groups. There is not enough information on the A*TREH frequency in the population of Russia. The aim of the study was to analyze the allele and genotype frequencies of the trehalase gene (rs2276064 TREH) in the main population groups of the Russian Federation and neighboring countries. Methods. DNA samples from 1146 unrelated subjects belonging to 21 population groups of Russia, Azerbaijan, Tajikistan and Mongolia were genotyped by the two following methods: 1) using the Infinium iSelect HD Custom Genotyping BeadChip (Illumina, USA) on the iScan platform; 2) by the real time polymer-chain reaction (PCR) method on the Bio-Rad CFX96 Touch amplifier. Results. It has been found that on the territory of the Russian Federation the frequency of the A*TREH allele increases from the west to the east. The frequencies are lowest in the groups of Russians and Finns of the Northwest (0.01-0.03), up to 0.07 in the populations of Central Russia and the Volga region, and even higher toward the Southern Urals (Bashkirs 0.15), in the Transurals and Southern Siberia (0.19 in the Altai people, 0.30 in the Tuvinians and Mongols). Up to 1% of the population of the European part of the Russian Federation have the AA*TREH genotype (i.e. trehalose intolerance in phenotype), and up to 15% (GA*TREH genotype) have a reduced ability to absorb the disaccharide. In the Asian part of the country (Siberia, Altai, Baikal) the genotypes carriers constitute up to 12 and 46% respectively. Conclusion. Trehalose malabsorbtion is an underappreciated problem of particular practical importance for regions with high concentrations of indigenous population (Yakutia-Sakha, Buryatia, Tyva, etc.). It would be feasible to consider food labelling of trehalose.