Altered Renin Angiotensin Aldosterone System Activity in South Asians

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 723-757-Renin-Angiotensin-Aldosterone System/Endocrine Hypertension
Bench to Bedside
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-748
Subbulaxmi Trikudanathan*1, Ellen Wells Seely2, Gordon H Williams3, Donald Craig Simonson2 and Bindu Chamarthi4
1University of Washington Medical Center, Seattle, WA, 2Brigham & Women's Hosp, Boston, MA, 3Brigham and Women's Hosp, Boston, MA, 4Brigham and Wmn's Hosp, Boston, MA
Background

South Asians have an increased risk of cardiovascular disease and insulin resistance compared to Caucasians. The underlying mechanisms for this increased risk are not fully understood. Activation of the renin-angiotensin-aldosterone system (RAAS) is known to be associated with increased cardiovascular morbidity. It has been shown that aldosterone levels are elevated in obesity and insulin resistant states. The aim of this study was to evaluate whether there are differences in RAAS activity between young healthy South Asians and Caucasians.

Methods

21 South Asians (mean age ± SD, 27.3±7.5 yrs.) and 65 Caucasians (33.4±7.9 yrs.) with similar BMI (23.9±3.1 vs. 24.3±2.6 kg/m²) underwent low salt (LS - 10mmol Na/day) and high salt (HS - 200 mmol/day) diets for 5-7 days. When participants were in sodium balance (urinary Na < 30 mmol/24h on LS and >200 mmol/24h on HS), they were admitted to the Clinical Research Center for an Angiotensin II (AngII) infusion (3ng/kg/min for 60 minutes) after staying supine and fasting overnight. Blood pressure (BP), plasma renin activity (PRA) and aldosterone were measured before and after AngII infusion. Participants also underwent an oral glucose tolerance test on HS diet.

Results

Aldosterone levels were similar at baseline in both groups on HS diet but significantly higher following AngII infusion in South Asians compared to Caucasians (21.7±8.1 vs. 15.9±6.4 ng/dL, p=0.006). The change in aldosterone (difference between baseline and AngII-stimulated levels) was also significantly greater in South Asians than Caucasian (15.8±6.4 vs. 11.0±6.7 ng/dL, p=0.01) on HS diet. Similar trends were seen on LS diet but were not significant. South Asians, compared to Caucasians, had significantly greater rise in systolic (SBP) and diastolic BP (DBP) in response to AngII on HS diet (SBP: 17±7 vs. 10±7 mmHg; DBP: 13±7 vs. 7±5 mmHg, p <0.0001). Similar significant BP changes were also seen on LS diet. PRA was not significantly different on both diets. Fasting glucose was higher in South Asians (90±5 vs. 81±12 mg/dl, p=0.002) and insulin sensitivity, determined by Matsuda index and adjusted for age, gender and BMI, was significantly lower in South Asians compared to Caucasians (p=0.038).

Conclusions

Young healthy South Asians display higher aldosterone and vascular responses to AngII and are more insulin resistant than Caucasians of similar BMI. These findings suggest that RAAS activity is dysregulated even in young healthy South Asians. This may be an important factor associated with increased insulin resistance and contributing to the increased cardiovascular risk in this population.

Nothing to Disclose: ST, EWS, GHW, DCS, BC

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm