Abstract
Edible legume seeds, such as lentils, have been shown to modulate the structural and functional properties of hypertensive blood vessels, however, the effects of dried beans have not been similarly evaluated. To determine whether beans could attenuate hypertension-induced vascular changes (remodeling and stiffness) in relation to their phytochemical content, spontaneously hypertensive rats (SHR) were fed diets containing black beans (BB; high phytochemical content as indicated by their dark seed coat colour) or navy (white) beans (NB; low phytochemical content) for eight weeks. An additional follow-up phase was included to determine how long the alterations in vascular properties are maintained after bean consumption is halted. Assessments included blood pressure (BP), pulse wave velocity (PWV), vessel compliance (small-artery) and morphology (large-artery), and body composition. Neither BBs nor NBs altered BP or PWV in SHR. SHR-BB demonstrated greater medial strain (which is indicative of greater elasticity) at higher intraluminal pressures (80 and 140 mmHg) compared to SHR-NB. BB consumption for 8 weeks enhanced vascular compliance compared to SHR-NB, as demonstrated by a rightward shift in the stress–strain curve, but this improvement was lost within 2 weeks after halting bean consumption. BB and NB increased lean mass after 8 weeks, but halting BB consumption increased fat mass. In conclusion, regular consumption of BBs may be appropriate as a dietary anti-hypertensive strategy via their positive actions on vascular remodeling and compliance.
Highlights
Hypertension occurs in more than one in five Canadian adults with 95% of cases having an unknown etiology, making treatment difficult [1,2].Current prescription drug therapy for hypertension focuses on controlling high blood pressure (BP).Nutrients 2020, 12, 685; doi:10.3390/nu12030685 www.mdpi.com/journal/nutrientsfor approximately 30% of individuals taking these medications, hypertension remains uncontrolled [2]
In Phase 1, the rats were randomized into four groups (n = 10/group) which received one of the specified diets for 8 weeks: (i) normotensive control WKY rats fed bean-free control diet (WKY-CTRL); (ii) spontaneously hypertensive rats (SHR) fed bean-free control diet (SHR-CTRL); (iii) SHR fed a black bean diet (SHR-black beans (BB)); and (iv) SHR fed a navy bean diet (SHR-navy (white) beans (NB))
The WKY rats had the greatest increase in fat mass and lean mass over 8 weeks, and this slope was significantly different from the slope of the SHR consuming the navy bean diet (Figure 1b)
Summary
For approximately 30% of individuals taking these medications, hypertension remains uncontrolled [2]. This gap in treatment efficacy suggests that it may be beneficial to pursue therapeutic strategies that target the underlying vascular structural changes responsible for hypertension (i.e. vascular remodeling [3]), rather than the clinical symptoms such as elevated systolic blood pressure (SBP) and/or diastolic blood pressure (DBP). A meta-analysis has shown that various pulses (beans, peas, chickpeas, lentils) exert a BP-lowering effect in hypertensive individuals [5]. Given the similar nutrient contents across the many types of pulse seeds [9], variations in phytochemical composition of these seeds could be responsible for the different therapeutic effects related to vascular function. With their dark seed coat color, typically have a greater total phenolic content and antioxidant activity than other bean types [13], but to-date they have yet to be examined for their effects on vascular remodeling and compliance
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