G-6A Polymorphism of Angiotensinogen Gene Modulates the Effect of Blood Pressure on Carotid Intima-Media Thickness: The Bogalusa Heart Study

Background The adverse association between blood pressure and carotid artery intima-media thickness (IMT), a surrogate measure of subclinical atherosclerosis, is well-known. However, whether the G-6A polymorphism of the angiotensinogen (AGT) gene, a candidate gene of hypertension and vascular remodeling, modulates this relationship is unknown. Methods In 662 white and black subjects aged 25 to 43 years (73.4% white, 39.7% male), common carotid IMT was measured by B-mode ultrasonography. Results The variant A-6 allele frequency was higher in blacks than in whites (0.850 v 0.448, P< .0001). In a bivariate analysis, there were no differences in mean arterial blood pressure and common carotid IMT between carriers and noncarriers of the G allele in whites, blacks, or the total sample, after adjusting for gender, age, and race. In a multivariable regression analysis that included the status of the G allele (carriers versus noncarriers) along with gender, age, mean arterial blood pressure, body mass index, LDL cholesterol, triglycerides:HDL cholesterol ratio, homeostasis model assessment of insulin resistance, smoking, and race (in the total sample), mean arterial blood pressure was significantly and adversely associated with common carotid IMT in whites, blacks, and the total sample. This adverse positive relationship between mean arterial blood pressure and common carotid IMT was noted among noncarriers but not carriers of the G allele (comparison of slopes, P = .02) in the total sample. Although the interaction was not significant (P = .2 and P = .05 in whites and blacks, respectively), a trend similar to that in the total sample was found in both races. Conclusions In a recessive manner, the genetic variant (G-6A) of the AGT gene modulates the association between blood pressure and carotid IMT in young adults.