Selection scan in Native Americans of Mexico identifies FADS2 rs174616: Evidence of gene-diet interactions affecting lipid levels and Delta-6-desaturase activity.

Searching for positive selection signals across genomes has identified functional genetic variants responding to environmental change. In Native Americans of Mexico, we used the fixation index (Fst) and population branch statistic (PBS) to identify SNPs suggesting positive selection. The 103 most differentiated SNPs were tested for associations with metabolic traits, the most significant association was FADS2/rs174616 with body mass index (BMI). This variant lies within a linkage disequilibrium (LD) block independent of previously reported FADS selection signals and has not been clearly associated with metabolic phenotypes. We tested this variant in two independent cohorts with cardiometabolic data. In the Genetics of Atherosclerotic Disease (GEA) cohort, the derived allele (T) was associated with increased BMI, lower LDL-C levels and a decreased risk of subclinical atherosclerosis in women. Significant gene-diet interactions affected lipid, apolipoprotein and adiponectin levels with differences according to sex, involving mainly total and complex dietary carbohydrate%. In the Genotype-related Effects of PUFA trial, the derived allele was associated with lower Δ-6 desaturase activity and erythrocyte membrane dihomo-gamma-linolenic acid (DGLA) levels, and with increased Δ-5 desaturase activity and eicosapentaenoic acid levels. This variant interacted with dietary carbohydrate% affecting Δ-6 desaturase activity. Notably, the relationship of DGLA and other erythrocyte membrane LC-PUFA indices with HOMA-IR differed according to rs174616 genotype, which has implications regarding how these indices should be interpreted. In conclusion, this observational study identified rs174616 as a signal suggesting selection in an independent linkage disequilibrium block, was associated with cardiometabolic and erythrocyte measurements of LC-PUFA in two independent Mexican cohorts and showed significant gene-diet interactions.

Human leukocyte antigen-DRB1 class II genes in Mexican Amerindian Mazahuas: genes and languages do not correlate.

BACKGROUND: The major histocompatibility complex genes are located on the short arm of the human sixth chromosome; they are highly polymorphic and therefore have been very advantageous in population genetic studies. METHODS: A Mazahua group established in North Mexico State and also in nearby Michoacan state in the rainy mountain highlands (Mexico) was studied for their human leukocyte antigen (HLA)-DRB1 alleles. The relationship with other Amerindians and worldwide populations was studied by using 14,996 chromosomes from 75 different populations and calculating neighbor-joining dendrograms and correspondence multidimensional values. RESULTS: Five principal HLA allele frequencies were found in our group: DRB1*0802 (the most frequent one in this population), DRB1*0407, DRB1*0403, DRB1*0101, and DRB1*1406. Both genetic distances and correspondence analyses clearly show that our Mazahua group is genetically close to some of the most ancient groups living in Mexico (Mayos, Zapotecans, Tennek) and South American Amerindians. Amerindians remain as a group apart from the rest of the world. CONCLUSIONS: The results analyzing the HLA-DR locus suggest that Mazahua language (Otomangue) does not correlate with those of the most closely HLA-correlated ethnic groups. The present data may be useful for future transplantation programs, HLA and disease diagnosis, and pharmacogenetic studies.

Comparación de los métodos DELFIA y RIA en la medición de las hormonas luteinizante y folículo estimulante en suero / Method comparizon of DELFIA and RIA for serum LH and FSH

Las mediciones de hormonas tuvieron un desarrollo importante desde que Yalow y Berson crearon en 1959 el primer radioinmunoanálisis (RIA) para insulina; desde entonces se han realizado múltiples investigaciones tendientes a encontrar métodos no radioisotópicos que ofrezcan mayor sensibilidad, especificidad y precisión. Una nueva alternativa es el DELFIA (dissociation enhancement lanthanide fluoroinmmunoassay) que es un tipo particular fue fluorinmunoanálisis de resolución temporal (TR-FIA), que conjuga antígenos altamente purificados y anticuerpos monoclonales de sistema de sandwich, con trazadores fluorescentes de vida media larga, como los quelatos de europio, samario y terbio, y un fluorómetro específico para mediciones en nanosegundos. Como parte del proceso de validación e introducción de nueva metodología, se realizó la evaluación comparativa entre DELFIA y RIA en la cuantificación de las hormonas luteinizante (LH) y folículo estimulante (FSH) en suero. Los resultados muestran ventajas del DELFIA en términos de sensibilidad, especificidad, volumen de muestra y vida media de reactivos, así como eliminación de trazadores radiactivos