Association between Type 2 Diabetes and Genetic Variations in Uncoupling Protein 2, beta3-Adrenergic Receptor, and Peroxisome Proliferator-Activated Receptor gamma in Korean

Moon, Min Kyong; Cho, Young Min; Jung, Hye Seung; Kim, Tae Yong; Lee, Yun Yong; Park, Joong Yeol; Lee, Ki Up; Shin, Chan Soo; Park, Kyong Soo; Kim, Seong Yeon; Lee, Hong Kyu; Shin, Hyoung Doo

Abstract

BACKGROUND: Type 2 diabetes mellitus is a multifactorial disease influenced by numerous genetic and environmental factors. The uncoupling proteins, 2 (UCP2), beta3-adrenergic receptor ADRB3, and peroxisome proliferator-activated receptor gamma PPAR gamma, are genes involved in energy expenditure and fatty acid metabolisms, ans are therefore regarded as candidate genes for type 2 diabetes. In this study, we examined whether the known polymorphisms of UCP2, ADRB3 and PPAR gamma are associated with type 2 diabetes in the Korean population.
METHODS
We studied 516 type 2 diabetic patients and 147 control subjects. The enrollment criteria for the control subjects were as follows; age > 60 years, no family history of diabetes in their first-degree relatives, a fasting plasma glucose (FPG) < 6.1 mmol/L, and a HbA1C < 5.8%. Height, weight, waist and hip circumference, FPG, 2 hour-plasma glucose after 75g-glucose load (2h-PG), blood pressure, lipid profile, and fasting insulin level were measured. The Ala55Val polymorphism of the UCP2, Trp64Arg polymorphism of the ADRB3, and Pro12Ala polymorphism of the PPAR gamma were determined by single base extension method.
RESULTS
The allele frequency of the Ala55Val variant of the UCP2 tended to be higher in the control subjects than in the type 2 diabetic patients (0.497 vs. 0.456, p=0.064). The allele frequencies of the Trp64Arg polymorphism of the ADRB3, and the Pro12Ala polymorphism of the PPAR gamma, were comparable between the diabetic patients and the control subjects (0.141 vs. 0.152 and 0.033 vs. 0.041, respectively). In the control subjects, the Ala55Val polymorphism of the UCP2 was associated with a significantly lower 2h-PG compared to the wild type (6.0 +/- 0.8 mmol/L vs. 6.6 +/- 0.7 mmol/L, p=0.002). The female control subjects, with the ADRB3 Trp64Arg variant, had a significantly lower triglyceride level than those without the variant (1.36 +/- 0.53 mmol/L vs. 1.74 +/- 0.82 mmol/L, p=0.020). The type 2 diabetic patients, with the ADRB3 Trp64Arg variant showed a significantly lower body mass index (23.6 +/- 2.6 kg/m2vs. 24.6 +/- 3.0 kg/m2, p=0.001). The PPAR gamma Pro12Ala variant, was not associated with any of the features of insulin resistance. The combined genotype of the Val allele of UCP2, Trp allele of ADRB3 and Ala allele of PPAR gamma was less frequent among the type 2 diabetes patients than the control subjects (0.020 vs. 0.056, p=0.039).
CONCLUSION
The Ala55Val variant of the UCP2, the Trp64Arg variant of the ADRB3 and the Pro12Ala variant of the PPAR gamma, were not associated with type 2 diabetes in the Korean population. However, the Ala55Val variant of the UCP2 was associated with a lower 2h-PG in the control subjects and the Trp64Arg variant of the ADRB3 was associated with a lower triglyceride level in the female control subjects. Further study may be required to elucidate if the combined genotype of Val allele of UCP2, Trp allele of ADRB3 and Ala allele of PPAR gamma would be protective against type 2 diabetes.