Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 314, Issue 1, Pages H45-H51Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00389.2017
Keywords
inorganic nitrate; nitric oxide; peripheral chemoreflex sensitivity; cardiovagal baroreflex sensitivity
Funding
- HumanN, Incorporated
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [K99HL130339, R00HL130339] Funding Source: NIH RePORTER
Ask authors/readers for more resources
Aging is associated with increased peripheral chemoreceptor activity, reduced nitric oxide (NO) bioavailability, and attenuation of cardiovagal baroreflex sensitivity (BRS), collectively increasing the risk of cardiovascular disease. Evidence suggests that NO may attenuate peripheral chemoreflex sensitivity and increase BRS. Exogenous inorganic nitrate (NO3-) increases NO bioavailability via the NO3--NO2--NO pathway. Our hypothesis was that inorganic NO3- supplementation would attenuate peripheral chemoreflex sensitivity and enhance spontaneous cardiovagal BRS in older adults. We used a randomized, placebo-controlled crossover design in which 13 older (67 +/- 3 yr old) adults ingested beetroot powder containing (BRA) or devoid of (BRP) NO3- and NO2- daily over 4 wk. Spontaneous cardiovagal BRS was assessed over 15 min of rest and was quantified using the sequence method. Chemoreflex sensitivity was assessed via -5 min of hypoxia (10% fraction of inspired O-2) and reported as the slope of the relationship between O-2 saturation (% S-Po2) and minute ventilation (in l/min) or heart rate (in beats/min). Ventilatory responsiveness to hypoxia was reduced after BRA (from -0.14 +/- 0.04 to -0.05 +/- 0.02 l.min(-1).% S-Po2(-1), P = 0.01) versus BRP (from -0.10 +/- 0.05 to -0.11 +/- 0.05 l.min(-1).% S-Po2(-1), P = 0.80), with no differences in heart rate responsiveness (BRA: from -0.47 +/- 0.06 to -0.33 +/- 0.04 beats.min(-1).% S-Po2(-1), BRP: from -0.48 +/- 0.07 to -0.42 +/- 0.06 beats.min(-1).% S-Po2(-1)) between conditions (interaction effect, P = 0.41). Spontaneous cardiovagal BRS was unchanged after BRA and BRP (interaction effects, P = 0.69, 0.94, and 0.39 for all, up, and down sequences, respectively), despite a reduction in resting systolic and mean arterial blood pressure in the experimental (BRA) group (P < 0.01 for both). These findings illustrate that inorganic NO3- supplementation attenuates peripheral chemoreflex sensitivity without concomitant change in spontaneous cardiovagal BRS in older adults. NEW & NOTEWORTHY Exogenous inorganic nitrate supplementation attenuates ventilatory, but not heart rate, responsiveness to abbreviated hypoxic exposure in older adults. Additionally, inorganic nitrate reduces systolic and mean arterial blood pressure without affecting spontaneous cardiovagal baroreflex sensitivity. These findings suggest that inorganic nitrate may attenuate sympathetically oriented pathologies associated with aging.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available