Objective: To examine the distribution of intron 4 polymorphism in endothelial nitric oxide synthase (eNOS) gene in mainland Chinese and Singapore Chinese and its association with diabetic nephropathy (DN).
Methods: Peripheral blood samples were collected from 237 diabetes patients with the diabetic duration longer than 10 years, 87 mainland Chinese who visited the Qilu Hospital, Shandong province, and diabetic duration and blood sugar control-matched 150 Singapore Chinese who visited the Singapore National University Hospital. DNA extraction, PCR, cloning, and sequencing were conducted.
Results: The 27 bp repeat polymorphism in intron 4 was tri allelic (a, b, and c alleles) in the Singapore Chinese while biallelic (a and b alleles) in the mainland Chinese. A third allele-allele c, with six 27 bp repeats was found. Significant difference was identified in the a allele distribution between the mainland and the Singapore Chinese (P < 0.001), but the intron 4 polymorphism didn't show any association with DN.
Conclusion: The intron 4 polymorphism is tri allelic, and the a allele distribution is not significantly associated with DN.