Characterization Of The Renin-Angiotensin-Aldosterone System In Young Healthy Black Adults: The African Prospective Study On The Early Detection And Identification Of Hypertension And Cardiovascular Disease (African-Predict Study)

This study presents a detailed profile of the renin-angiotensin-aldosterone system (RAAS), electrolytes, volume loading, blood pressure (BP), and total peripheral resistance in healthy young Black and White adults. We also explored longitudinal associations between BP and RAAS. We included normotensive Black (N=543) and White (N=573) adults (20-30 years) and followed N=324 over similar to 4.5 years. We measured clinic (central, brachial) and 24-hour BP, total peripheral resistance and left ventricular dimensions. We determined serum NT-proBNP (N-terminal prohormone B-type natriuretic peptide), RAAS, and 24-hour urinary and serum Na+ and K+. RAAS components, left ventricular internal diameter (diastole), end diastolic volume and NT-proBNP were lower (P<0.001) in Black than White adults, despite similar clinic SBP. However, central systolic BP and total peripheral resistance were higher in Black adults (P<0.001). Plasma renin activity and angiotensin II were comparable between Black and White groups (P>0.05) only in quartile 1 of Na+/K+ values. In both groups, RAAS was lower in the higher quartiles of 24-hour Na+ and NT-proBNP (all P-trend <= 0.014). Over 4.5 years, all BPs increased in the Black (P<0.001) but not White group. The increase in central systolic BP over time was associated with elevated serum aldosterone only in Black adults (beta=0.18, P=0.038). We found that RAAS concentrations in healthy Black adults were half of those of White participants, which may not be explained by volume expansion. Yet, baseline aldosterone predicted BP elevation over time in Black adults. RAAS was similar in Black and White adults only at low Na+/K+ scenarios, suggesting an essential role of potassium.