Angiotensin-converting enzyme gene polymorphism and its association with essential hypertension in a Tibetan population

There is strong evidence to support the idea that the renin-angiotensin system (RAS) plays an important role in the pathogenesis of essential hypertension (EH) and its complications. However, existing data about the association of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with blood pressure is conflicting, mainly due to racial differences and environmental exposure status. We therefore conducted a case control study to observe the relationship between ACE I/D polymorphism and EH in a Tibetan population who live in relatively isolated areas and are genetically homogeneous. The study was conducted at stable residential communities in the urban district of Lhasa, the capital of the Tibet autonomous region, China, and 106 unrelated EH patients and 135 normotensive subjects were recruited. PCR, PCR/RFLP and PCR-SSCP were carried out to study the association between RAS genes and EH. Frequencies for the DD, ID and II genotypes were 27, 47 and 29 in hypertensive subjects, and 15, 60 and 48 in normotensive subjects, respectively. Derived allele frequencies for the I and D alleles were 0.51 and 0.49 in hypertensive subjects and 0.64 and 0.36 in normotensive subjects. There were significant differences in genotype distribution and derived allele frequency between these two groups. The genotype and allele frequencies of the ACE gene differed significantly between hypertensive and normotensive females (p>0.05), but there were no differences in males. In females, the DBP and MAP level were significantly higher for the DD than for the ID and II genotype, and SBP was significantly higher for the DD than for the II genotype. But in males, there were no significant differences in blood pressure among ACE genotypes. The results showed a significant association between the D allele of the ACE gene and hypertension in Tibetan women but not in Tibetan men.