Polymorphic analysis of MC4R gene in ethnic Kashmiri population with type 2 diabetes

Abstract

Activation of MC4R gene has been shown to inhibit appetite and increase basal metabolic rate while deficiency leads to obesity, hyperphagia, severe hyperinsulinemia, increased linear growth and decrease in metabolic activity, facts that drew strong attention as a possible cause of obesity and diabetes. In this study, we aimed to investigate the sequence variations of MC4R gene in a diabetic population of the Kashmir region and work out association of such variations (if any) with the disease phenotype. No such study has ever been taken up in the Jammu and Kashmir State, despite the existence of a significant population of type 2 diabetic patients. A total of 420 samples (200 with type 2 diabetes and 220 controls) were taken. Genomic DNA was extracted from whole blood samples using standard protocols like salting out and proteinase k. The specific fragments of DNA were amplified and hence then purified. Purified amplicons were subjected to heteroduplex assay to screen for SNPs/mutations. Samples which showed heteroduplex bands were sent for sequencing. The genotype and allele frequencies were evaluated using the χ 2 tests or the Fisher exact tests. We here report one novel heterozygous mutation, i.e. C to T at codon 7 in diabetic patients. The results showed significant differences in the 7C/ T genotype (p < 0.001) and allele (p < 0.0001) frequencies between type 2 diabetes mellitus and control subjects. The fasting blood sugar (FBS), postprandial blood sugar (PPBS) and random blood sugar (RBS) levels were higher with CT genotype in type 2 diabetes mellitus patients but difference was not found statistically significant. C to T substituting arginine with cysteine appeared to associate with type 2 diabetes in the Kashmiri population. Insilico predictions show that substitutions likely have an impact on structure and functional properties of protein making it imperative to understand their functional consequences in relation with diabetes and obesity.