Abstract
Dietary sodium reduction affects blood pressure (BP), the renin-angiotensin-aldosterone system (RAAS) and natriuretic peptides. Whether baseline levels of these hormones impact BP response to sodium reduction remains unknown. Aldosterone dysregulation relates to higher cardiovascular risk, but the relation to sodium reduction has not been uncovered. We conducted a randomized clinical trial of 72 patients with hypertension, who were randomised 2:1 to four weeks of dietary sodium reduction or a control group. 24-h BP and 24-h urine collection were performed and blood samples (renin, aldosterone, pro-ANP, BNP) were drawn before and after. Antihypertensive medication was continued throughout the study. We found a significant increase in plasma levels of renin and aldosterone in the low-salt group compared to the control group. We performed a post-hoc separation of the low-salt group based on the change in aldosterone after sodium reduction into aldosterone responders and non-responders, and found significantly higher baseline aldosterone levels in the non-responders (p = 0.01). Systolic 24-h BP did not change in the aldosterone non-responders, but decreased 9 mmHg among the aldosterone responders (p = 0.01 for difference). Pro-ANP and BNP decreased in the aldosterone responders, however, increases were found in the non-responders. There was a tendency towards a larger decrease in body weight in the aldosterone responders (p = 0.054). In conclusion, sodium reduction revealed a group of aldosterone non-responders with impaired RAAS activation, higher aldosterone levels and no BP response. This group showed opposite responses in natriuretic peptides and less decrease of body weight than aldosterone responders.