title: Short-term dietary nitrate supplementation augments cutaneous vasodilatation and reduces mean arterial pressure in healthy humans.
abstract: Nitrate supplementation in the form of beetroot juice has been shown to increase nitric oxide (NO) where nitrate can be reduced to nitrite and, subsequently, to NO through both nitric oxide synthase (NOS)-dependent and -independent pathways. We tested the hypothesis that nitrate supplementation would augment the NO component of the cutaneous vasodilatation to local skin heating in young, healthy humans. Participants reported to the lab for pre- and post-supplement local heating protocols. Nitrate supplementation consisted of one shot (70 ml) of beetroot juice (0.45 g nitrate; 5mM) for three days. Six participants were equipped with two microdialysis fibers on the ventral forearm and randomly assigned to lactated Ringer's (control) or continuous infusion of 20mM l-NAME (NOS inhibitor). The control site was subsequently perfused with l-NAME once a plateau in skin blood flow was achieved to quantify NOS-dependent cutaneous vasodilatation. Skin blood flow via laser-Doppler flowmetry (LDF) and mean arterial pressure (MAP) were measured; cutaneous vascular conductance (CVC) was calculated as LDF/MAP and normalized to %CVCmax. Beetroot juice reduced MAP (Pre: 90 ± 1 mmHg vs. Post: 83 ± 1 mmHg) and DBP (Pre: 74 ± 2 mmHg vs. Post: 62 ± 3 mmHg) (P<0.05). The plateau phase of the local heating response at control sites was augmented post-beetroot juice (91 ± 5%CVCmax) compared to pre-beetroot juice (79 ± 2%CVCmax) (P<0.05). There was no difference in the %NOS-dependent vasodilatation from pre- to post-beetroot juice. These data suggest that nitrate supplementation via beetroot juice can reduce MAP and DBP as well as augment NOS-independent vasodilatation to local heating in the cutaneous vasculature of healthy humans.
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, KS, USA.
authors.forename: Jeremy T
authors.initials: JT
authors.lastname: Keen
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, KS, USA.
authors.forename: Erica L
authors.initials: EL
authors.lastname: Levitt
authors.affiliation: Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Hodges
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, KS, USA; Department of Kinesiology & Health, Georgia State University, Atlanta, GA, USA. Electronic address: bwong@gsu.edu.
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Wong
mesh_terms: D000328:Adult; D062186:Arterial Pressure; D027461:Beta vulgaris; D001794:Blood Pressure; D015992:Body Mass Index; D004032:Diet; D019587:Dietary Supplements; D000067030:Fruit and Vegetable Juices; D064368:Healthy Volunteers; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009566:Nitrates / Q000008:administration & dosage* / Q000737:chemistry; D009569:Nitric Oxide; D012867:Skin / Q000098:blood supply; D014664:Vasodilation / Q000187:drug effects*; D055815:Young Adult
chemical_list: D009566:Nitrates; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester
keywords: Beetroot juice; Blood pressure; Microdialysis; Microvasculature; Nitric oxide