DNA polymorphisms associated with lactase persistence, self-perceived symptoms of lactose intolerance, milk and dairy consumption, and ancestry, in the Uruguayan population.

Uruguay has one of the highest per capita milk intakes worldwide, even with a limited supply of lactose-free products; furthermore, the admixed nature of its population is well known, and various frequencies of lactase persistence (LP) are observed in the source populations. We aimed to contribute to the understanding of the relation between allelic variants associated with LP, milk consumption, digestive symptoms, and genetic ancestry in the Uruguayan population. Samples of saliva or peripheral blood were collected from 190 unrelated individuals from two regions of Uruguay, genotypes for polymorphic sites in a fragment within the LCT enhancer were determined and allelic frequencies calculated in all of them. Data were collected on frequency of milk and dairy consumption and self-reported symptoms in a subsample of 153 individuals. Biparental and maternal ancestry was determined by analyzing individual ancestry markers and mitochondrial DNA. Twenty-nine percentage of individuals reported symptoms attributed to the ingestion of fresh milk, with abdominal pain, bloating and flatulence being the most frequent. European LP-associated allele T-13910 showed a frequency of 33%, while other LP-associated alleles like G-13915 and T-14011 were observed in very low frequencies. Associations between self-reported symptoms, fresh milk intake, and C/T-13910 genotype were statistically significant. No evidence of association between genetic ancestry and C/T-13910 was found, although individuals carrying one T-13910 allele appeared to have more European ancestry. In conclusion, the main polymorphism capable of predicting lactose intolerance in Uruguayans is C/T-13910, although more studies are required to unravel the relation between genotype and lactase activity, especially in heterozygotes.

Genetic Admixture Analysis in the Population of Tacuarembó-Uruguay Using Alu Insertions.

Tacuarembó is a department located in northeastern Uruguay, whose population is the result of several migration waves from Europe and Near East, as well as Africans and Afro-descents mostly from Brazil; these waves settled with the territory's various Native ethnic groups (Charrúa, Minuán, and Guaraní). In the past, this population has been the focus of genetic studies showing this trihybrid origin, with greater contributions of Natives and Africans than in other Uruguayan regions. In this study we analyzed eight Alu insertions (A25, ACE, APOA1, B65, D1, F13B, PV92, TPA25) to provide valuable information for ancestrality and genetic differentiation and to compare with both previous studies on the Tacuarembó population and Alu frequencies in other Uruguayan populations. The European contribution to Alu and classical markers was almost equal to that of a previous study using 22 classical markers (63% vs. 65%), while African contribution was higher (30% vs. 15%), and Native American contribution shows an important difference in Alu: 7% versus 20%. We found no significant differences in genetic differentiation between Tacuarembó and Montevideo but significant differences between Tacuarembó and Basque descendants from Trinidad. Our results support previous findings obtained with classical markers that demonstrate the trihybrid composition of the Tacuarembó population, correlated with historical records. Thus, Alu insertions provide interesting information in light of the admixture process in the Uruguayan population.