Dietary Flaxseed Reduces Central Aortic Blood Pressure Without Cardiac Involvement but Through Changes in Plasma Oxylipins.

Key Findings

In the FlaxPAD trial (Flaxseed for Peripheral Artery Disease), dietary flaxseed was a powerful nutritional intervention that reduced brachial systolic blood pressure and diastolic blood pressure in patients with hypertension and peripheral artery disease (PAD). This previous work was done through conventional measurements of brachial blood pressure (BP) in patients. One of the aims of the present study was to investigate the capacity of flaxseed to influence central blood pressure (cBP) which is a better predictor of cardiovascular events and all-cause mortality. Another aim was to define the capacity of flaxseed to influence cardiac functional capacity and augmentation index (vascular stiffness) using pulse wave analysis (PWA). Dietary flaxseed induced decreases in cSBP and cDBP. The reduction in cSBP (10 mm Hg) and cDBP (6 mm Hg) was similar to the average decrease in brachial systolic blood pressure (15 mm Hg) and diastolic blood pressure (7 mm Hg) reported in the FlaxPAD study. The data support the involvement of ALA and oxylipins in the antihypertensive action of flaxseed. Several oxylipins can regulate vascular tone. The data supports the use of dietary flaxseed for the management of hypertension in patients living with PAD who currently take antihypertensive medications yet remain to have uncontrolled blood pressure.

Abstract

In the year-long FlaxPAD clinical trial (Flaxseed for Peripheral Artery Disease), dietary flaxseed generated a powerful reduction in brachial systolic and diastolic blood pressure in patients with peripheral artery disease. Oxylipins were implicated as potential mechanistic mediators. However, the ability of flaxseed to impact central aortic hypertension, arterial stiffness, or cardiac performance was not investigated. Additionally, the relationship between central blood pressure (cBP) and oxylipins was not elucidated. Therefore, radial tonometry and pulse wave analysis were used to measure cBP and cardiac function in the FlaxPAD population (n=62). Plasma oxylipins were analyzed with high-performance liquid chromatography mass spectrometry. In patients with high blood pressure at baseline, the average decrease in central systolic and diastolic blood pressures versus placebo was 10 and 6 mm Hg, respectively. Flaxseed did not significantly impact augmentation index or other cardiac function indices. Alternatively, the data support several specific oxylipins as potential mediators in the antihypertensive properties of flaxseed. For example, every 1 nmol/L increase in plasma 16-hydroxyeicosatetraenoic acid increased the odds of higher central systolic and diastolic blood pressures by 12- and 9-fold, respectively. Every 1 nmol/L increase in plasma thromboxane B₂ and 5,6-dihydroxyeicosatrienoic acid increased the odds of higher cBP by 33- and 9-fold, respectively. Flaxseed induced a decrease in many oxylipins, which corresponded with a reduced risk of elevated cBP. These data extend the antihypertensive properties of flaxseed to cBP without cardiac involvement but rather through oxylipins. This study provides further support for oxylipins as therapeutic targets in hypertension.