Two Novel Functional Single Nucleotide Polymorphisms of ADRB3 Are Associated With Type 2 Diabetes in the Chinese Population

Aims: The purpose of this study was to investigate the association of two novel beta(3)-adrenergic receptor (ADRB3) gene polymorphisms (Ser165Pro and Ser257Pro) with type 2 diabetes (T2DM) in the Chinese population. Methods: A total of 650 patients with T2DM and 1337 health volunteers were enrolled to conduct the association study. Two candidate polymorphisms were recreated by site-directed mutagenesis and tested for their effect on ADRB3 expression and function in stable transfected human embryonic kidney 293 and Chinese hamster ovary-K1 cells. Real-time PCR, Western blot, confocal microscopy, and cAMP assay were used to determine mRNA, protein expression, trafficking, and ADRB3 function, respectively. Results: We found that both polymorphisms were significantly associated with T2DM (odds ratio = 2.060 and 95% confidence interval = 1.303-3.258 for Ser165Pro and odds ratio = 7.588, 95% confidence interval = 1.639-35.138 for Ser257Pro). Patients with T2DM with the Ser165Pro C allele had higher hemoglobin A(1c), fasting plasma glucose and postprandial plasma glucose values than those in TT genotypes. We also found that patients with T2DM with the Ser257Pro C allele had lower fasting serum insulin, postprandial serum insulin, and homeostasis model assessment for insulin resistance levels than TT genotype carriers. Further in vitro study indicated that cell lines stably expressing Ser165Pro and Ser257Pro mutants of the ADRB3 gene showed impaired cAMP accumulation activity. However, both polymorphisms had no effect on ADRB3 expression and trafficking. Conclusions: Ser165Pro and Ser257Pro polymorphisms affected ADRB3 function and were significantly associated with susceptibility to and development of T2DM.