title: Acute dietary nitrate supplementation enhances compensatory vasodilation during hypoxic exercise in older adults.
abstract: We have previously demonstrated that aging reduces the compensatory vasodilator response during hypoxic exercise due to blunted nitric oxide (NO) signaling. Recent evidence suggests that NO bioavailability can be augmented by dietary nitrate through the nitrate-nitrite pathway. Thus we tested the hypothesis that acute dietary nitrate supplementation increases the compensatory vasodilator response to hypoxic exercise, particularly in older adults. Thirteen young (25 ± 1 yr) and 12 older (64 ± 2 yr) adults performed rhythmic forearm exercise at 20% of maximum voluntary contraction during normoxia and hypoxia (∼80% O2 saturation); both before (control) and 3 h after beetroot juice (BR) consumption. Forearm vascular conductance (FVC; ml·min(-1)·100 mmHg(-1)) was calculated from forearm blood flow (ml/min) and blood pressure (mmHg). Compensatory vasodilation was defined as the relative increase in FVC due to hypoxic exercise (i.e., % increase compared with respective normoxic exercise trial). Plasma nitrite was determined from venous blood samples obtained before the control trials and each of the exercise trials (normoxia and hypoxia) after BR. Consumption of BR increased plasma nitrite in both young and older adults (P < 0.001). During the control condition, the compensatory vasodilator response to hypoxic exercise was attenuated in older compared with young adults (3.8 ± 1.7% vs. 14.2 ± 1.2%, P < 0.001). Following BR consumption, compensatory vasodilation did not change in young (13.7 ± 3.3%, P = 0.81) adults but was substantially augmented in older adults (11.4 ± 2.1%, P < 0.01). Our data suggest that acute dietary nitrate supplementation increases the compensatory vasodilator response to hypoxic exercise in older but not young adults.
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa; and darren-casey@uiowa.edu.
authors.forename: Darren P
authors.initials: DP
authors.lastname: Casey
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa; and.
authors.forename: David P
authors.initials: DP
authors.lastname: Treichler
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa; and.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Ganger
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa; and.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Schneider
authors.affiliation: Department of Anesthesia, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Ueda
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000187:drug effects; D027461:Beta vulgaris; D019587:Dietary Supplements; D015444:Exercise; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply; D009566:Nitrates / Q000097:blood / Q000494:pharmacology* / Q000627:therapeutic use; D008517:Phytotherapy; D010936:Plant Extracts; D014664:Vasodilation / Q000187:drug effects*; D055815:Young Adult
chemical_list: D009566:Nitrates; D010936:Plant Extracts
keywords: aging; dietary nitrate; exercise; hypoxia; vasodilation