Anti-Hypertensive Effect Of Thermolys-Indigested Rice Bran On High Normal Blood Pressure And Mild Hypertension

Objectives: We previously showed that enzyme treatment of rice bran, a byproduct of white rice processing, provided it with a functional blood pressure-lowering effect after oral treatment to spontaneously hypertensive rats. We also revealed that the angiotensin-converting enzyme inhibitory activity of novel tripeptide Leu-Arg-Ala (LRA) functioned as the hypotensive mechanism of thermolysin-digested rice bran (TRB) [Shobako S., MNFR, 2018]. In this study, we carried out to evaluate the hypotensive effect of TRB for patients with high normal blood pressure and mild hypertension in randomized, double-blind, placebo-controlled experiment. Methods: TRB (1000 mg; LRA 124 ppm; n = 44) and placebo control (n = 43) were supplemented in pill form for 12 weeks to subjects (45–65 years; BMI < 30.0 kg/m2) judged to have high normal blood pressure and mild hypertension at both 6 and 2 weeks before starting supplementation. Blood pressure measurements and blood biochemical examinations were performed at − 6, − 2, 0, 4, 8, 10 and 12 weeks. Results: Significant reductions in systolic blood pressure in patients receiving TRB compared with placebo were observed at 8 (−6.19 ± 9.30 mmHg vs. − 1.63 ± 9.18 mmHg, p < 0.05), 10 (−6.95 ± 9.96 mmHg vs. − 2.09 ± 10.21 mmHg, p < 0.05), and 12 (−6.95 ± 9.14 mmHg vs. − 2.85 ± 9.34 mmHg, p < 0.05) weeks. Conclusion: We clearly showed that TRB containing novel peptide LRA lowered blood pressure in subjects with high normal blood pressure and mild hypertension. This is the first study to demonstrate that enzyme digestion of otherwise useless rice bran is practically effective for improvement of lifestyle diseases. In conclusion, we propose that supplementation of TRB containing LRA could be a promising treatment to control blood pressure especially for patients with high normal blood pressure and mild hypertension.