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. 10 older adults (67±3yrs) consumed 4.03mmol nitrate and 0.29mmol nitrite (active) or devoid of both (placebo) daily for 4wks in randomized, double-blinded, crossover fashion. Brachial artery diameter (D) and blood velocity (V_mean) were measured via Doppler ultrasound at rest for the characterization of shear profile as well as during two handgrip exercise trials (4 and 8kg) for calculation of forearm blood flow (V_mean*cross-sectional area, FBF) and conductance (FBF/mean arterial pressure, FVC). Plasma [nitrate] and [nitrite] increased following active (P<0.05 for both) but not placebo (P=0.68 and 0.40, respectively) supplementation. Neither mean nor antegrade shear rate changed following either supplement (beverage-by-time P=0.14 and 0.21, respectively). Retrograde (-13.4±7.0 to -9.7±6.8s^-1) and oscillatory (0.20±0.08 to 0.15±0.09A.U., P<0.05 for both) shear decreased following active, but not placebo (P=0.81 and 0.70, respectively), supplementation. The FBF response (Δ from rest) to neither 4kg nor 8kg trials changed following either supplement (beverage-by-time P=0.53 and 0.11, respectively). Similarly, no changes were observed in FVC responses to 4kg or 8kg trials (beverage-by-time P=0.23 and 0.07, respectively). These data indicate inorganic nitrate supplementation improves conduit artery shear profiles, but not exercise hyperemia, in older adults.

中文翻译：

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补充无机硝酸盐可减轻老年人的导管动脉逆行和振荡剪切

衰老会导致静止的导管动脉剪切模式发生有害变化，并且在运动过程中血液流量减少，部分原因是一氧化氮（NO）减少。无机硝酸盐可增加循环NO的生物利用度，因此可改善与年龄相关的剪切速率变化以及运动性充血。10名老年人（67±3岁）每天以随机，双盲，交叉的方式服用4周，每天消耗4.03mmol硝酸盐和0.29mmol亚硝酸盐（活性物质）或不含两者（安慰剂）。静息时通过多普勒超声测量肱动脉直径（D）和血流速度（V _mean）来表征剪切曲线，并在两次手握运动试验（4和8kg）中测量前臂血流量（V _mean）*横截面积FBF）和电导率（FBF /平均动脉压FVC）。活性补充后血浆[硝酸盐]和[亚硝酸盐]增加（两者均P <0.05），但安慰剂未增加（分别为P = 0.68和0.40）。两种补充剂之后，平均剪切剪切速率和前向剪切剪切率均未改变（时间饮料P分别为0.14和0.21）。逆行（-13.4±7.0至-9.7±6.8s ^-1）和补充后，振荡性（0.20±0.08至0.15±0.09AU，两者均P <0.05）剪切降低，但安慰剂却未降低（分别为P = 0.81和0.70）。补充食品后，对4kg和8kg试验的FBF反应（静止时的Δ）均未改变（每次饮料的P分别为0.53和0.11）。同样，在FVC对4kg或8kg试验的反应中也没有观察到变化（按时间点的饮料P = 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曲线，但不能改善运动性充血。