EXCESS ALDOSTERONE RELATIVE TO PLASMA RENIN AND ANGIOTENSIN II ASSOCIATES POSITIVELY WITH CENTRAL SYSTOLIC BLOOD PRESSURE IN YOUNG BLACK AFRICANS

Abstract

Objective: Populations of African ancestry usually present with a suppressed renin-angiotensin-aldosterone system (RAAS) attributed to excessive sodium retention and subsequently experience early and severe forms of hypertension-mediated organ damage. Central systolic blood pressure (cSBP) was previously found to be higher in young black adults as compared to their white counterparts. In the current study, we investigated associations of cSBP with a detailed RAAS profile in a healthy young population stratified according to ethnicity and sex. Design and method: This study included apparently healthy black men (N = 285) and women (N = 304), white men (N = 278) and women (N = 305) aged 20–30 years old. The SphygmoCor XCEL was used to derive cSBP. Aldosterone and equilibrium angiotensin levels were measured by LC-MS/MS and used for calculating angiotensin derived markers for plasma renin activity (PRA-S, Angiotensin I + Angiotensin II), angiotensin-converting enzyme (ACE-S, Angiotensin II/Angiotensin I), and two markers for adrenal effects of angiotensin II, the aldosterone-to-renin ratio (ARR-S, Aldosterone/PRA-S) and the aldosterone-to-angiotensin II-ratio (AA2-R, Aldosterone/Angiotensin II). Sodium and potassium were determined from 24-hour urine and then used to calculate sodium-to-potassium ratio. Results: Young black men and women presented with lower RAAS components and higher cSBP and urinary sodium-to-potassium ratio as compared to their white counterparts (all P < = 0.001). In forward stepwise multiple regression analyses, we observed the following associations: In black women, cSBP associated positively with ARR-S (β=0.269; P = 0.001) and AA2-R (β=0.263; P = 0.001), and negatively with PRA-S (β=-0.311; P < 0.001) and angiotensin II (β=-0.311; P < 0.001). In black men we observed a negative association between cSBP and PRA-S (β=-0.181; P = 0.047). None of the associations were present in white men and women. Conclusions: Positive associations of cSBP with the ratio of aldosterone to both PRA-S and angiotensin II in healthy young black women suggest that excess aldosterone may have deleterious effects on central blood pressure in this population group, which may lead to early target organ damage. The absence of any association between cSBP and RAAS components in white adults indicates an ethnic disparity in central pressure regulation.