Soy isoflavone supplementation alleviates oxidative stress and improves systolic blood pressure in male spontaneously hypertensive rats

The aim of this study was to investigate the protective effect of isoflavone against hypertension, via the mitigation of oxidative stress and prevention of nitric oxide (NO, a potent vasodilator) reduction, in spontaneously hypertensive rats (SHR). The 8 wk-old male SHR were divided into two groups, and fed a casein-based high fat diet (120 g fat, 1 g cholesterol/kg diet) for 30 d, either with or without 10 g of soy powder (containing 31.2% of isoflavones)/kg. During the 30-d study period, tail systolic blood pressures (BP) in the control SHR group increased, from 162.4 +/- 4-2.3 to 177.9 +/- 5.4 mmHg (p < 0.05), while the isoflavone-supplemented group benefited from a clear antihypertensive effect (160.1 +/- 1.8 to 160.2 +/- 4.9 mmHg). The serum NO and total radical trapping antioxidant potential (TRAP) were elevated in the isoflavone group. The isoflavone group also experienced a significant decrease in oxidative DNA damage in leukocytes, using comet assay. DNA damage correlated positively with incremental BP during the study, and systolic BP at the end of the study (p < 0.01). Our results indicate that soy isoflavone has an antihypertensive effect, possibly through the amelioration of oxidative stress, and the augmentation of NO production, in SHR.