Topical Area: Dietary Bioactive Components
To examine whether diet supplementation with blackberry or raspberry attenuate angiotensin (Ang) II-induced increase in blood pressure (BP) and decrease oxidative stress in the kidneys of mice.
Methods : Twelve-week male C57BL/6J mice were fed AIN-93M diets alone (control and Ang II groups) or supplemented with 10% w/w freeze-dried blackberry (BL + Ang II) or raspberry (RB + Ang II) powder for eight weeks. At week 4, mice were implanted with subcutaneous osmotic minipumps that delivered 0.9% saline (Control) or Ang II (1 µg/kg body weight/day) for another four weeks. BP was measured weekly by tail-cuff plethysmography and validated by direct measurement at endpoint using a BP catheter. Kidney expression of pro-oxidant enzymes such as NADPH oxidases (Nox) and antioxidant enzymes such as superoxide dismutates (SOD) were also measured. Results were analyzed using ANOVA followed by Tukey-Kramer post-hoc test.
Results : As expected, Ang II significantly increased systolic BP (SBP; 185 ± 4, n=6, vs 132 ± 2 mmHg, n= 5, P < 0.001) and diastolic BP (124 ± 4, n=6, vs 96 ± 2 mmHg, n= 4, P < 0.001) compared to control. Supplementation with BL and RB significantly attenuated this increase in SBP (143 ± 7 mmHg, n=5, P < 0.0001 and 137 ± 4 mmHg, n=5, P < 0.0001, respectively) and DBP (100 ± 6 mmHg, n=5, P < 0.003 and 90 ± 3 mmHg, n=5, P < 0.0001, respectively). Regarding the expression of NADPH oxidases in the kidney, Nox2 was significantly decreased by supplementation with BL (0.68 ± 0.07-fold, n=5, P = 0.0005) and RB (0.70 ± 0.03-fold, n=5, P = 0.0008) compared to Ang II (1.15 ± 0.12-fold, n=5). Nox1 expression was up-regulated by Ang II compared to control (2.03 ± 0.16 vs 1.00 ± 0.00-fold, n=5, P = 0.0001), but this was not prevented by supplementation with either berry. Nox4 expression was not affected by any of the treatments. Lastly, Ang II did not change the expression of SOD1 and SOD2 in the kidney, however, supplementation with RB significantly increased SOD1 (P = 0.02) and SOD2 (P = 0.005) expression compared to the other groups.
Our findings indicate that supplementation with BL and RB decrease BP in mice which may be related to a decrease in oxidative stress in the kidney. Studies are underway to further elucidate the mechanism by which BL and RB exert their antihypertensive effects.
Funding Sources : Arkansas Biosciences Institute and Lewis Foundation Grant Program