The genetic basis of lactase persistence and lactose digestion in Iran and Afghanistan

Backgrounds: Milk, a major source of calcium, is required for bone and tooth health. The maincarbohydrate in milk is lactose which, in mammals, is digested by an enzyme called lactase.Lactase is highly expressed in all human infants but its expression persists in only ۳۲% of adults;a phenotype called lactase persistence. In some lactase nonpersistent individuals, milkconsumption is associated with gastrointestinal symptoms and causes lactose intolerance. Milkavoidance places lactose intolerant individuals at a higher risk of bone fracture and osteoporosis.In addition to the physiological tests, genetic tests have also been very useful for lactasenonpersistent detection in some ethnic groups.Materials and Methods: In this study, we have explored the genetic basis of lactase persistencyin two ethnic groups in Iran and Afghanistan. We determined the phenotype of lactasepersistency and the genotype of five single nucleotide polymorphisms responsible for lactasepersistence.Results: Our results show that lactase persistency phenotype is higher in Hezareh (۱۰%)compared to a Mazani ethnicity from Shahmirzad (۲.۳%). Our study reveals a new geneticvariant at the regulatory region of the lactase gene but failed to find a direct genotype-phenotypecorrelation. This suggests that other genetic variants and/or epigenetic effects are responsible forlactase persistency in these two ethnicities.Conclusion: The identification of lactase expression status in lactose-intolerant individuals anddistinguishing lactase persistent and nonpersistent individuals in a group of subjects with lactoseintolerance is an important first step in devising nutritional recommendations to optimize healthand manage diseases; goals of personalized nutrition.

کلیدواژه ها:

human genetic diversity ، single nucleotide polymorphism ، Lactase persistence ، lactose intolerance ، personalized nutrition