Diets containing blueberry extract lower blood pressure in spontaneously hypertensive stroke-prone rats

Oxidative stress in the vasculature and kidneys contributes to hypertension, a major risk factor for cardiovascular disease. Blueberries (BB) are rich in antioxidants, and so we hypothesized that feeding diets enriched with BB would slow the development of hypertension in spontaneously hypertensive stroke-prone rats (SHRSP). Eight-week-old normotensive rats and SHRSP were fed either a control diet (Con) or a diet enriched with 3% freeze-dried BB for 8 weeks. Systolic blood pressure (SBP) was measured at weeks 2, 4, 6, 7, and 8 by the tail cuff method, and urine was collected at weeks 4 and 8. The SBP was elevated in SHRSP relative to normotensive rats over the entire 8-week feeding period. In SHRSP consuming BB, SBP was 19% lower at week 4 and 30% lower at week 6, relative to SHRSP on Con. Maximum SBP was 216 +/- 11 mm Hg in SHRSP consuming Con vs 178 +/- 15 mm Hg in the BB-fed group (P = .036). Spontaneously hypertensive stroke-prone rats had elevated levels of urine F2-isoprostanes/creatinine relative to normotensive rats, indicating systemic oxidative stress in this strain. Blueberry feeding had no effect on urinary excretion of F2-isoprostanes; therefore, it is unlikely that a systemic antioxidant effect of BB is responsible for the antihypertensive effects at weeks 4 and 6. Blueberry-fed rats had reduced markers of renal oxidative stress, such as proteinuria and kidney nitrites. Thus, a 3% BB diet may be capable of protecting the kidneys from oxidative damage in SHRSP, thereby reducing the magnitude of hypertension.