[Genetics of lactase deficiency in Russia]

The ability to digest lactose in adulthood is caused by a genetic mutation that emerged following the domestication of cattle approximately 10 000 years ago. However, many adults retain primary lactase deficiency - the ancestral phenotype characterized by a decline in lactase enzyme activity after weaning. While the global prevalence of this condition is well-documented, reliable large-scale population data for Russia have been lacking so far. Microarray genotyping of genetic markers now enables high-quality, up-to-date research covering representative samples from diverse ethnic groups across Russia's regions. The purpose of the research was to compare the frequency of GG genotype in rs4988235 (13910 C/T) in the regulatory region (MCM6) of the lactase enzyme gene LCT, which determines the genetic risk of lactase insufficiency manifestation, in populations living in Russia and evaluate the differences between Russian regions. Methods. The largest multi-ethnic genetic study on lactase deficiency in Russia was conducted on a sample of 24,439 individuals in 56 populations. The percentage of an individual belonging to each ethnic group was estimated by calculating the ancestral contribution to an individual's genetic makeup. In addition, we calculated the frequency of the rs4988235 GG genotype in regions of Russia using information on the individual's current location and place of birth. Results. The prevalence of lactase deficiency by GG genotype rs4988235 in the Russian population was 45.2 and 42.8% (95% confidence interval 42.1-43.4) in the East Slavs group. The study revealed a significant variability (22.8-83.2%) in the regional prevalence of lactase deficiency by GG rs4988235 genotype. The dependence of the regional prevalence of lactase deficiency on the current place of residence is supported by the geographical features of the Russian territory and the history of pastoralism in different regions. Conclusion. The findings may be useful for developing regional nutrition recommendations and optimising the Russian market for lactose-free and low-lactose products, and justify the importance of genetic testing for diagnosis, highlighting the interdisciplinary relevance of the study.