A prevalent amino acid polymorphism at codon 98 (Ala98Val) of the hepatocyte nuclear factor-1a is associated with maturity-onset diabetes of the young and younger age at onset of type 2 diabetes in Asian Indians

Abstract

Objective - Among Europeans, mutations in the hepatocyte nuclear factor-1α (HNF1α) gene are associated with the most common form of maturity-onset diabetes of the young (MODY)₃. In Asian Indians, type 2 diabetes occurs earlier and often overlaps with MODY, but the genetics of the latter are unknown. The aim of this study was to estimate the prevalence of Ala98Val polymorphism of the HNF1α gene in different types of diabetes in Asian Indians. Research design and methods-Genotyping of Ala98Val was done by the PCR-restriction fragment-length polymorphism method in the following groups: 1) MODY, defined as non-insulin-dependent diabetes (age at onset <25 years) and vertical transmission of diabetes through at least three generations (n = 122); 2) very-early-onset type 2 diabetes (age at onset <25 years) without family history (n = 23); 3) early-onset type 2 diabetes (age at onset between 26 and 40 years, n = 171); 4) late-onset type 2 diabetes (age at onset >40 years, n = 133); 5) type 1 diabetes (n = 150); and 6) normal glucose tolerance (n = 130). The frequency of the Val genotypes was compared in the diabetic and control groups. Results-The frequency of the Val allele was significantly higher in MODY patients (P = 0.0013) compared with control groups. Furthermore, in the total group of patients with type 2-like diabetes (groups 1-4), the Val allele was associated with an earlier diagnosis of diabetes (P = 0.0002). Conclusions-Among Asian Indians, the Ala98Val polymorphism of HNF1α gene is associated with MODY and with earlier age at onset of type 2 diabetes.