Ameliorative Effects of Beetroot Juice Supplementation on Monocrotaline-Induced Pulmonary Hypertension in Rats

Beetroot is a nitrate-rich vegetable with cardiovascular benefits. This study examined whether ingestion of beetroot juice (BRJ) protects against pulmonary hypertension (PH). Rats were injected subcutaneously with 60 mg/kg monocrotaline (MCT) and randomized to receive either drinking water, low-dose BRJ (BRJ-L, nitrate content: 1.4 mmol/L), or high-dose BRJ (BRJ-H, nitrate content: 3.5 mmol/L), which was started 1 week after MCT injection and continued until the end of the experiment. Four weeks after MCT injection, right ventricle (RV) hypertrophy, right ventricular systolic pressure (RVSP) elevation, and pulmonary vascular remodeling were observed. These PH symptoms were less severe in rats supplemented with BRJ-L (Fulton index, p = 0.07; RVSP, p = 0.09, pulmonary arterial medial thickening, p < 0.05), and the beneficial effects were more pronounced than those of BRJ-H supplementation. Plasma and RV nitrite and nitrate levels did not change significantly, even when BRJ-L and BRJ-H were administered. There were no differences in plasma thiobarbituric acid reactive substances (TBARS), a biomarker of oxidative stress, among the groups. BRJ-L supplementation significantly decreased RV TBARS levels compared to MCT alone (p < 0.05), whereas BRJ-H supplementation did not. These findings suggest that starting BRJ supplementation from an early stage of PH ameliorates disease severity, at least partly through the inhibition of local oxidative stress. Habitual ingestion of BRJ may be useful for the management of PH.