RESUMO
AIM: This study aimed to investigate the acute effects of dietary nitrate ingestion through L-arginine supplementation or dehydrated beet consumption on endothelial function in chronic obstructive pulmonary disease (COPD) patients. The secondary outcome was to analyze arterial stiffness, plasma nitrate, and nitrate/protein concentration. METHODS: In this randomized crossover study, subjects with COPD underwent three series of supplementation: (1) L-arginine, (2) dehydrated beetroot, and (3) a placebo that appeared like the other supplements. Each intervention lasted 14 days, with a 7-day washout period between series. Participants underwent endothelial function assessment using flow-mediated dilatation (FMD), and plasma nitrate levels were measured at the end of each supplementation series. RESULTS: Seventeen subjects (twelve male) completed the study protocol. Only five subjects presented endothelial dysfunction (RHI ≤ 0.51) at baseline. The mean baseline characteristics included age 66.5 ± 9.4 years, BMI 27.5 ± 4.5 kg/m2, FEV1, 0.79 (0.67 - 1.06) L. There were no differences (p > 0.05) between the groups or from pre- to post-interventions for RHI and arterial stiffness index (AIx) values, as well as parameters of endothelium-dependent vasodilation, such as blood flow velocity (BFV), shear stress, shear rate, FMD (mm), and FMD%. There was also no differences (p > 0.05) between the groups or from pre- to post-interventions plasma nitrate levels. CONCLUSIONS: Acute dietary supplementation with nitrates, at the doses provided, did not show a significant improvement in endothelial function assessed by FMD, EndoPAT, or plasma nitrate levels in COPD. These findings suggest that a higher dose or prolonged supplementation might be required to achieve a therapeutic effect.
RESUMO
OBJECTIVES: Cardiovascular disease is a major cause of mortality in chronic obstructive pulmonary disease (COPD) and endothelial dysfunction may enhance the mortality risk. Exercise training has shown to be beneficial for improvement of endothelial function in patients with cardiovascular disease, but this remains unclear in COPD. Thus, this study aimed to assess the effect of exercise-based pulmonary rehabilitation (PR) on endothelium function, arterial stiffness and plasma nitrite levels in patients with COPD. METHODS: Patients with COPD engaged a 48-session PR program. Reactive hyperaemia index (RHI), augmentation index (AIx), and heart rate (HR) assed by peripheral arterial tonometry (PAT), plasma nitrite levels, systemic blood pressure, functional capacity (six-minute walk test) and the BODE index were assessed at baseline and after 24 and 48 sessions of PR. Plasma nitrite levels were also assessed before and after the first session of PR. RESULTS: Twenty-one subjects were included and completed 24 PR sessions, and 16 subjects completed 48 sessions. It was observed that a poorer AIx adjusted for HR in frequent COPD exacerbators (4.67 ± 16.5 vs. 20.9 ± 12.9; p = .02). PR improved functional capacity (380 ± 107 m vs. 442 ± 115 m; p < .001) and the BODE index (6 [2.8] vs. 4 [3]; p = .001), but did not change HR, systemic arterial pressure, RHI, AIx, and plasma nitrite levels during the follow-up. Plasma nitrite levels reduced after the first session of PR (0.074 [0.079] µM vs. 0.061 [0.04] µM; p = .027). The acute change in plasma nitrite levels correlated with RHI in patients with preserved endothelial function (r = 0.71; p = .01). CONCLUSIONS: Although exercise-based PR improved functional capacity and the BODE index, it did not change endothelial function and arterial stiffness in patients with COPD.
