Dietary nitrate load lowers blood pressure and renal resistive index in patients with chronic kidney disease: A pilot study

Beetroot has a high concentration of inorganic nitrate, which can serially reduced to form nitrite and nitric oxide (NO) after oral ingestion. Increased renal resistive index (RRI) measured by Doppler ultrasonography is associated with higher cardiovascular mortality in hypertensive patients with reduced renal function over time defined as chronic kidney disease (CKD). Our aim was to investigate whether the supplementation of dietary nitrate by administration of beetroot juice is able to reduce blood pressure and renal resistive index (RRI) as prognostic markers for cardiovascular mortality in CKD patients. In a cross-over study design, 17 CKD patients were randomized to either a dietary nitrate load (300 mg) by highly concentrated beetroot juice (BJ) or placebo (water). Hemodynamic parameters as well as plasma nitrate concentration and RRI were measured before and 4 h after treatment. In this cohort, CKD was mainly caused by hypertensive or diabetic nephropathy. The mean eGFR was 41.6 ± 12.0 ml/min/m². Plasma nitrate concentrations were significantly increased after ingestion of BJ compared to control. Peripheral systolic and diastolic blood pressure as well as mean arterial pressure (MAP) were significantly reduced secondary to the dietary nitrate load compared to control (e.g. ΔMAP_BJ = -8.2 ± 7.6 mmHg vs. ΔMAP_control = -2.2 ± 6.0 mmHg, p = 0.012). BJ also led to significantly reduced RRI values (ΔRRI_BJ = -0.03 ± 0.04 versus ΔRRI_control = 0.01 ± 0.04; p = 0.017). Serum potassium levels were not altered secondary to the treatment. In this study, administration of the nitrate donor BJ led to significantly reduced RRI values and peripheral blood pressure which might be explained by release of the vasodilatator NO after oral intake. Whether supplementation of dietary nitrate in addition to routine pharmacologic therapy is able to decelerate progression of cardiovascular and renal disease in CKD, remains to be investigated.