Association between promoter polymorphisms of the GRP78 gene and risk of type 2 diabetes in a Chinese Han population.

There are large amounts of unfolding or misfolding protein accumulation in the endoplasmic reticulum in patients with type 2 diabetes (T2D), which in turn induces the expression of the glucose-regulated protein 78 (GRP78) that plays a key role in influencing insulin secretion and maintaining glucose homeostasis in pancreatic beta cells. The aim in the study is to analyze the potential association between single-nucleotide polymorphisms (SNPs) of GRP78 and the risk of T2D. To assess the association between GRP78 polymorphisms and T2D, a case-control study was conducted among 1058 consecutive unrelated subjects. Of the 1058 subjects, 523 of them were diagnosed with T2D and 535 of them were healthy controls. Four SNPs with R(2)>0.8 and the minor allele frequency>0.05 (rs391957, rs17840761, rs17840762, and rs11355458) in the GRP78 gene promoter were analyzed. Overall, no associations of GRP78 polymorphisms with T2D were observed in genotypic analyses. In addition, haplotypes combining those SNPs in the promoter in high linkage disequilibrium were also not associated with a T2D risk. However, the levels of fasting plasma glucose and HbA1c in patients with the -415AA/-180GG genotype were significantly lower than those of the patients with -415GG/-180deldel and -415AG/-180Gdel genotypes, and the level of fasting insulin in patients with the -415AA/-180GG genotype was significantly lower than that of the patients with -415GG/-180deldel. The study does not support a role for promoter polymorphisms of GRP78 in T2D in a Chinese Han population, but it does provide a clue for association between low levels of fasting plasma glucose, HbA1c and fasting insulin, and the -415AA/-180GG model.