Exploring the Antihypertensive and Vascular-Protective Effects of Blueberries in Middle-Aged/Older Men: Study Protocol

Abstract

Abstract Objectives Previous research has demonstrated the antihypertensive and vascular-protective effects of blueberries in postmenopausal women with elevated blood pressure (BP) or stage 1-hypertension (HTN). However, this has not been explored in men with elevated BP or HTN. The objective of the present study is to examine effects of blueberry (BB) on BP, endothelial function, and arterial stiffness in men with elevated BP or stage 1-HTN, and baseline endothelial dysfunction, as well as to investigate possible mechanisms involved with BB on vascular health. Methods In a randomized, double-blind, placebo-controlled, parallel-arm trial, men with elevated BP or stage 1-HTN (systolic BP of 120–139 mmHg, and a diastolic BP < 90 mmHg), and endothelial dysfunction (reactive hyperemia index, RHI) <1.67, but otherwise healthy, will be randomized to receive either 22 g/day of freeze-dried wild BB powder or 22 g/day of placebo powder for 12 weeks. Primary outcomes for this study are BP and RHI, which is a measure of vascular endothelial function assessed using peripheral arterial tonometry. Secondary outcomes include analysis of arterial stiffness, measured by pulse wave velocity (PWV), as well as blood biomarkers of cardiovascular and metabolic health that include blood lipids, hemoglobin A1c, oxidized LDL, nitric oxide, and adhesion molecules. Furthermore, endothelial cells will be biopsied to provide mechanistic insight on how BB consumption might affect the vascular system by utilizing quantitative immunofluorescence. Results We hypothesize that 22 g/day of BB consumption (∼1 cup) for 12 weeks will improve endothelial function, arterial stiffness, and BP in men with elevated BP and/or stage 1-HTN. We also hypothesize that these improvements will be mediated by reductions in vascular oxidative stress and inflammation, and increased nitric oxide bioavailability. Conclusions This study has potential to provide unique in vivo (functional) and ex vivo (molecular) support for the hypothesis that BB consumption may attenuate endothelial dysfunction, arterial stiffness, and high BP that occurs with aging. Funding Sources Wild Blueberry Association of North America.