Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
Am J Physiol Heart Circ Physiol. 2021 Mar 1;320(3):H991-H998. doi: 10.1152/ajpheart.00843.2020. Epub 2021 Jan 15.
Aging causes deleterious changes in resting conduit artery shear patterns and reduced blood flow during exercise partially attributable to reduced nitric oxide (NO). Inorganic nitrate increases circulating NO bioavailability and may, therefore, improve age-associated changes in shear rate as well as exercise hyperemia. Ten older adults (age: 67 ± 3 yr) consumed 4.03 mmol nitrate and 0.29 mmol nitrite (active) or devoid of both (placebo) daily for 4 wk in a randomized, double-blinded, crossover fashion. Brachial artery diameter (D) and blood velocity (V) were measured via Doppler ultrasound at rest for the characterization of shear profile as well as during two handgrip exercise trials (4 and 8 kg) for calculation of forearm blood flow (V × cross-sectional area, FBF) and conductance [FBF/mean arterial pressure, forearm vascular conductance (FVC)]. Plasma [nitrate] and [nitrite] increased following active ( < 0.05 for both) but not placebo ( = 0.68 and 0.40, respectively) supplementation. Neither mean nor antegrade shear rate changed following either supplement (beverage-by-time = 0.14 and 0.21, respectively). Retrograde (-13.4 ± 7.0 to -9.7 ± 6.8·s) and oscillatory (0.20 ± 0.08 to 0.15 ± 0.09 A.U., < 0.05 for both) shear decreased following active, but not placebo ( = 0.81 and 0.70, respectively), supplementation. The FBF response (Δ from rest) to neither 4-kg nor 8-kg trials changed following either supplement (beverage-by-time = 0.53 and 0.11, respectively). Similarly, no changes were observed in FVC responses to 4-kg or 8-kg trials (beverage-by-time = 0.23 and 0.07, respectively). These data indicate that inorganic nitrate supplementation improves conduit artery shear profiles, but not exercise hyperemia, in older adults. We report for the first time, to our knowledge, that 4 wk of inorganic nitrate supplementation attenuates retrograde and oscillatory shear in the brachial artery of older adults. However, this was not associated with greater hyperemic or vasodilatory responses to exercise. In sum, these data highlight favorable changes in shear patterns with aging, which may reduce the risk of atherosclerotic cardiovascular disease.
衰老导致静息管腔动脉剪切模式发生有害变化，并减少运动期间的血流量，这部分归因于一氧化氮 (NO) 减少。无机硝酸盐增加循环中 NO 的生物利用度，因此可能改善与年龄相关的剪切率变化以及运动性充血。10 名老年人（年龄：67 ± 3 岁）以随机、双盲、交叉方式每天摄入 4.03 mmol 硝酸盐和 0.29 mmol 亚硝酸盐（活性）或两者均不摄入（安慰剂）4 周。通过多普勒超声在休息时测量肱动脉直径 (D) 和血流速度 (V)，以表征剪切轮廓，以及在两次手握力试验（4 和 8 kg）期间计算前臂血流量 (V × 截面积，FBF) 和传导率[FBF/平均动脉压，前臂血管传导率 (FVC)]。活性补充后（两者均 < 0.05），血浆 [硝酸盐] 和 [亚硝酸盐] 增加，但安慰剂补充后无变化（分别为 0.68 和 0.40）。两种补充剂均不改变平均或前向剪切率（饮料-时间分别为 0.14 和 0.21）。主动补充后，反向（-13.4 ± 7.0 至-9.7 ± 6.8·s）和振荡剪切（0.20 ± 0.08 至 0.15 ± 0.09 AU，两者均 < 0.05）下降，但安慰剂补充后没有变化（分别为 0.81 和 0.70）。两种补充剂均不改变 4 公斤或 8 公斤试验的 FBF 反应（与休息相比的Δ）（饮料-时间分别为 0.53 和 0.11）。同样，在 4 公斤或 8 公斤试验中，FVC 反应没有观察到变化（饮料-时间分别为 0.23 和 0.07）。这些数据表明，无机硝酸盐补充剂可改善老年人的导管动脉剪切模式，但不能改善运动性充血。据我们所知，我们首次报告称，4 周的无机硝酸盐补充可减轻老年人肱动脉的反向和振荡剪切。然而，这与运动时更大的充血或血管舒张反应无关。总之，这些数据突出了与衰老相关的剪切模式的有利变化，这可能降低动脉粥样硬化性心血管疾病的风险。
