LCT-22018G>A single nucleotide polymorphism is a better predictor of adult-type hypolactasia/lactase persistence in Japanese-Brazilians than LCT-13910C>T

Abstract

Adult type hypolactasia, the genetically programmed down‐regulation of lactase enzyme activity in the intestinal wall after weaning, is a common condition worldwide, except for in northwestern Europe, where the prevalence is less than 10%. Lactose intolerant individuals complain of abdominal cramps, bloating, distention, flatulence and diarrhea after milk or lactose‐containing food ingestion.1 The diagnosis of adult‐type hypolactasia can be achieved by a hydrogen breath test that is cumbersome and provokes symptoms, or more recently, using a genetic approach.2 Lactase persistence and adult‐type hypolactasia have been associated with the LCT‐13910C>T and LCT ‐22018G>A polymorphisms in introns 13 and 9, respectively, of the minichromosome maintenance type 6 gene (MCM6) upstream of the LCT locus in several populations.3 In Brazil, the lactase persistence allele, LCT‐13910T, was found in approximately 43% of both white (European descent) and brown (European and African descent), and 20% of black (African descent) Brazilians, but was absent in all Japanese‐Brazilians studied.4 Recent epidemiological data regarding lactose intolerance/hypolactasia are lacking in Japan. This lack of information may be because of the relative rarity of symptoms; it has been shown that, although 92% of tested subjects were lactase deficient, only 2% were milk intolerant and 13% were lactose intolerant.5 Recent evidence in northern China suggests that LCT‐22018G>A, rather than LCT‐13910C>T, LCT‐13907C>G, LCT‐13915T>G, or LCT‐14010G>C, matched the lactase persistence phenotype.6 Therefore, the purpose of this study was to ascertain whether LCT‐22018G>A would also be a predictor of lactase persistence in Japanese‐Brazilians.