Polymorphism of the genetic determinants of bone mineral metabolism in various groups of the Komi people

Abstract

The subject of the study is autochthonous population of the Northern and Middle Cis-Urals: Komi-Permyaks, Komi (Zyryans), and Komi-Izhems. The aim of the study is to compare the population frequencies of the LCT (rs4988235) and VDR (FokI rs2228570 and BsmI rs1544410) genes and to consider the contribution of environ-mental and cultural factors to the formation of differences in the genetic determinants of bone tissue metabolism. In total, 181 Komi-Permyak, 223 Komi, and 200 Komi-Izhem subjects were tested clinically and genetically. The evaluation consisted of the determination of polymorphic loci of VDR and LCT genes variants and assessment of clinical and laboratory lactase activity. The information on traditional diet and food composition was obtained from ethnographic materials. The study group of Komi-Izhems differs by a high proportion of C*LCT carriers (0.85) from the other two groups (p < 0.05). The prevalence of hypolactasia, i.e., limited lactase production, is also higher (p < 0.05) in Komi-Izhems (0.64) than in Komi-Permyaks (0.47) and Zyryans (0.41). The T*BsmI allele frequency is higher in Komi-Izems (0.493) in hetero- CT* (0.463) and homozygote TT* (0.261) genotypes, as compared to Zyryans (p < 0.05, where the frequencies are 0.377, 0.329 and 0.212, respectively). The values of BsmI allele and genotype frequencies in Komi-Permyaks are intermediate and do not differ significantly from those in Komi-Izhems and Zyryans. The concentration of T*FokI is highest in Komi-Permyaks (0.528). They are followed by Zyryans (the difference is insignificant, p > 0.05). Komi-Izhems have the smallest proportion of T*FokI allele carriers (0.400) and significantly differ from Komi-Permyaks (p = 0.01). The genotype distributions in FokI locus of VDR in the groups of Komi-Permyaks and Zyryans do not differ, but both show higher CT*FokI genotype frequencies than Komi-Izhems (0.549 and 0.569 against 0.288; p < 0.001). Poor livestock production and a lack of milk in the traditional subsistence economy of the Komi-Permyaks weakened the selection in favor of T*LCT allele and lactase persistence. The low intake of calcium with milk was compensated by an increase in the sensitivity of the target organs to calciferol, the regulator of mineral metabolism, by maintaining the high frequency of carriers of T*BsmI and T*FokI alleles of VDR gene in the population. The more productive dairy farming of Zyryans stimulated selection in favor of lactase persistence. The possibility of continuous consumption of calcium from milk eased the selection pressure on VDR loci. The regulation by T*FokI produced a physiologically sufficient effect and T*BsmI carriership remained low. The diet of the Komi-Izhems, who were accustomed to high-latitude regions, comprised low-lactose dairy products. The population preserved a high carriage of C*LCT and the phenotype of hypolactasia. Moderately intensive selection for vitamin D receptor sensitivity showed up in the increase of VDR T*BsmI frequency only. The high D-vitamin status of the Izhem people was leveraged by the traditional diet with a considerable intake of ergocalciferol-rich venison and fish. The Komi-Permyaks, Komi (Zyryans) and Komi-Izhems occupied different ecological niches and the groups found different ways to adapt to the unfavorable bone-homeorhesis conditions. The flexible responses to the pressure of the environmental factors were imple-mented by the selection of variants of LCT, VDR FokI and VDR BsmI genes, which are located in different chro-mosomes and determine different stages of mineral metabolism. We contend that modern interpopulation differences in distribution of the genotypes and alleles are the manifestations of different strategies of ecological adaptation of anthropologically related groups.