Molecular analysis of LCT gene in association with primary hypolactasia in the random population of Mashhad, Iran

Introduction: Primary hypolactasia or lactose intolerance is the most common enzyme deficiency in the world with a high prevalence in Asia and Far East. It results from a genetically programmed decline of lactase enzyme in the intestine after weaning. This could reduce the consumption of the dairy products and subsequent problems such as calcium deficiency. Hypolactasia has an autosomal recessive pattern of inheritance. Functional and family studies indicated that a DNA variant, CT-13910, is strongly associated with hypolactasia. This polymorphism is located on chromosome 2q2, 13910 base pairs upstream from the lactase or LCT gene in intron 13 of MCM6. CC genotype is associated with hypolactasia. Symptoms of lactose intolerance are varying greatly in severity and depend on the amount of lactose ingested and on individual sensitivity. Aim of this study was to estimate the prevalence of primary hypolactasia by the analysis of CT-13910 polymorphism. Methods: Number of 150 individuals was selected randomly. These individuals asked to give a blood sample for genotyping of the C/T-13910 variant of hypolactasia. DNA was extracted from leukocytes; LCT-13910 C>T polymorphism was analyzed by PCR-restriction fragment length polymorphism (PCR-RFLP). Results: 126 (84%) of the samples have CC genotype, 22 (15%) of samples have CT genotype and 2 (1%) of samples have TT genotype. Frequency of C allele was 91% and frequency of T allele was 9%. Conclusion: In this study the frequency of the C allele was high, probably due to high consanguinity in Iranian population. According to CC genotype frequency (84%), we could predict that the prevalence of hypolactasia is high in our population. We suggested that the age of onset of hypoalactasia should be determined and genetic test could be used as a screening and diagnostic test for adult type hypolactasia.