Abstract 025: Urine Angiotensinogen and Salt-Sensitivity of Blood Pressure: The GenSalt Study
Urine excretion of angiotensinogen (AGT) has been proposed as a biomarker of intrarenal renin-angiotensin system activity, and therefore as a proxy for blood pressure regulation and sodium homeostasis. The association between urine levels of AGT and blood pressure response to dietary sodium intake has not been previously examined in the general population. We assessed the hypothesis that there is a direct relationship between urine levels of AGT and salt-sensitivity of blood pressure among participants of the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) replication study. A 7-day low-sodium intervention, followed by a 7-day high-sodium intervention was carried out among 698 GenSalt-replication study participants from rural areas of north China. Absolute urine AGT excretion (μg/24 hours) and AGT-to-creatinine ratio (AGT/Cr, μg/g) were estimated at baseline for a random sample of 100 study participants. Nine blood pressure measurements were obtained at baseline and on the last three days of each intervention period. The absolute and percent changes in mean blood pressure from low-sodium to high-sodium intervention were used to assess salt-sensitivity. Median AGT and AGT/Cr were significantly (both p=0.01) reduced during the low-sodium intervention (AGT: 7.16 μg/24 hours, AGT/Cr: 8.36 μg/g) and increased during the high-sodium intervention (AGT: 8.84 μg/24 hours, AGT/Cr: 10.92 μg/g) compared to baseline (AGT: 8.28 μg/24 hours, AGT/Cr: 9.40 μg/g). Log-transformed AGT and AGT/Cr ratio at baseline was significantly and positively associated with blood pressure at baseline and at the end of each intervention. For example, one standard deviation higher log-transformed AGT/Cr ratio (1.2 μg/g) was associated with a 4.0 mm Hg (95% confidence interval: 1.3, 6.7) higher systolic blood pressure level at the end of the high-sodium intervention (p=0.004). One standard deviation higher log-transformed AGT/Cr ratio was associated with 1.58-times increased odds of high salt-sensitivity (≥5% change) of blood pressure (95% confidence interval: 1.00, 2.50; p=0.049). Log-transformed AGT/Cr ratio at baseline was positively associated with absolute and percent systolic blood pressure change from low- to high-sodium interventions (absolute: r=0.23, p=0.02; percent: r=0.20, p=0.047). In conclusion, elevated levels of urine AGT are associated with sodium-sensitivity of blood pressure. Augmentation of renal-angiotensin system activity may play an important role in the development of salt-sensitive hypertension.
- © 2013 by American Heart Association, Inc.