Distribution of cytotoxic T lymphocyte-associated antigen-4 promoter polymorphisms in Taiwanese patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is associated with chronic inflammation, suggesting the metabolic abnormalities are originated from or exacerbated by cytokine overproduction. Cytokines and counter-regulatory molecules are crucial in keeping the balance of immune responses and, therefore, are potential candidates involved in T2DM etiology, development and complications. Our previous reports identify several significant associations between the genotypes of cytokine genes and T2DM and/or the clinical lipid parameters, which strongly suggest the participation of immune-regulatory molecules in lipid metabolism. The aim of this study is to determine the distribution of gene encoding cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), a T-cell negative regulator, in T2DM patients and health subjects. Genomic DNA was extracted from 287 Taiwanese T2DM patients and 278 ethnic- and agematched healthy subjects, and two CTLA-4 polymorphisms (-318 C/T and +49 A/G) were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Intriguingly, CTLA-4 -318 genotype was associated with circulatory triglycerides in T2DM subjects (P=0.019) although no significant association between CTLA-4 -318 (P=0.119) and +49 (P=0.2) genotypes with T2DM was identified. In addition, CTLA-4 +49 genotype was significantly associated with the ratio between total cholesterol and high-density lipoprotein (P=0.004) in control subjects. Our results suggest that CTLA-4 may be involved in lipid metabolism and affect T2DM disease progression and/or the development of diabetic complications although this gene does not represent a major risk factor for T2DM.