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J Appl Physiol (1985). 2018 Sep 1;125(3):862-869. doi: 10.1152/japplphysiol.01081.2017. Epub 2018 Jun 1.

Dietary nitrate supplementation reduces low frequency blood pressure fluctuations in rats following distal middle cerebral artery occlusion.

Author information

1
Department of Surgery and Anaesthesia, Centre for Translational Physiology, University of Otago , Wellington , New Zealand.
2
Wellington Medical Technology Group, Department of Surgery & Anaesthesia, University of Otago , Wellington , New Zealand.
3
Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago , Dunedin , New Zealand.
4
Faculty of Pharmacy, The University of Sydney, New South Wales, Australia.

Abstract

It is known that high blood pressure variability (BPV) in acute ischemic stroke is associated with adverse outcomes, yet there are no therapeutic treatments to reduce BPV. Studies have found increasing nitric oxide (NO) bioavailability improves neurological function following stroke, but whether dietary nitrate supplementation could reduce BPV remains unknown. We investigated the effects of dietary nitrate supplementation on heart rate (HR), blood pressure (BP), and beat-to-beat BPV using wireless telemetry in a rat model of distal middle cerebral artery occlusion. Blood pressure variability was characterized by spectral power analysis in the low frequency (LF; 0.2-0.6 Hz) range prestroke and during the 7 days poststroke in a control group ( n = 8) and a treatment group ( n = 8, 183 mg/l sodium nitrate in drinking water). Dietary nitrate supplementation moderately reduced systolic BPV in the LF range by ~11% compared with the control group ( P = 0.03), while resting BP and HR were not different between the two groups ( P = 0.28 and 0.33, respectively). Despite systolic BPV being reduced with dietary nitrate, we found no difference in infarct volumes between the treatment and the control groups (1.59 vs. 1.62 mm3, P = 0.86). These findings indicate that dietary nitrate supplementation is effective in reducing systolic BPV following stroke without affecting absolute BP. In light of mounting evidence linking increased BPV with poor stroke patient outcome, our data support the role of dietary nitrate as an adjunct treatment following ischemic stroke. NEW & NOTEWORTHY Using a rat model of stroke, we found that dietary nitrate supplementation reduced low frequency blood pressure fluctuations following stroke without affecting absolute blood pressure values. Since blood pressure fluctuations are associated with poor clinical outcome in stroke patients, our findings indicate that dietary nitrate could be an effective strategy for reducing blood pressure fluctuations, which could help reduce stroke severity and improve patient recovery.

KEYWORDS:

blood pressure; ischemic stroke; nitric oxide

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