Single nucleotide polymorphism (D68D, T to C) in the syntaxin 1A gene correlates to age at onset and insulin requirement in Type II diabetic patients

Aim/hypothesis. Syntaxin 1A is a candidate gene for Type II (non-insulin-dependent) diabetes mellitus, because it plays an important role in insulin secretion from the islet beta cells. We aimed to scan this gene for mutations or genetic markers that correlate with Type II diabetes. Methods. We identified and characterized coding exons of the syntaxin 1A gene and scanned the newly identified 10 exons using direct sequencing. Results. In the single nucleotide polymorphism (SNP) of exon 3 (D68D, T to C) among three newly identified SNPs, genotype frequency of the homozygote of C allele (CC) occurred more frequently in a Type II diabetic group than in a non-diabetic group (16.48%, n = 182, vs 11.05%, n = 181. p = 0.0499). Among the diabetic patients, age of onset in patients with CC genotype was lower than that in patients with the TT and TC genotypes [40.10 +/- 1.50 years old (means SEM) vs 44.20 +/- 0.58, p = 0.005]. Patients with the CC genotype had a higher frequency of insulin treatment (78.30% vs 46.80%, p = 0.006) with a duration equal to, or longer than, 10 years. Multiple regression analysis confirmed that the genotype was significantly and independently associated with age at onset and mode of treatment, respectively. Conclusion/interpretation. These data indicate that the SNP in the syntaxin 1A gene (D68D, T to C) correlates to the age of onset and insulin requirements of Type II diabetic Japanese patients.