High sodium intake strengthens the association between angiotensinogen T174M polymorphism and blood pressure levels among lean men and women: a community-based study.

Evidence on the effect of salt intake on the interaction between angiotensinogen (AGT) T174M polymorphism and high blood pressure is sparse. We therefore conducted a large population-based cross-sectional study of 2,823 men and women aged 30-74 in a Japanese farming community to examine associations between AGT polymorphism and blood pressure levels stratified by age (30-64 and 65-74), body mass index (BMI; median), and salt intake (median) estimated by 24-h urine collection and dietary questionnaire. Our a priori hypothesis is that individuals, particularly younger and non-overweight individuals, with the 174M allele have elevated blood pressure levels in response to higher sodium intake, and thus the association between T174M polymorphism and blood pressure is more evident among individuals with higher sodium intake than those with lower sodium intake. There were no differences in systolic or diastolic blood pressure levels (SBP or DBP) between the TT and TM+MM genotype groups overall. However, the mean difference in DBP between the TM+MM and TT groups was +1.0 mmHg in subjects of younger age (p=0.06), +1.7 mmHg in non-overweight subjects (BMI<23.5 kg/m2, p=0.01), and +2.3 mmHg in younger and non-overweight subjects (p = 0.002). Furthermore, among younger and non-overweight subjects, blood pressure differences were larger for those with higher urinary sodium excretion (+3.1 mmHg, p = 0.03), those with a higher sodium/potassium excretion ratio (+4.1 mmHg, p=0.007), those with higher present sodium intake score (+3.0 mmHg, p=0.003), and those with higher past sodium intake score (+3.4 mmHg, p<0.001). In conclusion, AGT T174M polymorphism was associated with higher DBP levels in younger and non-overweight Japanese. This association was more evident among subjects with higher sodium intake.