Cheng Jem L, Au Jason S, MacDonald Maureen J
Department of Kinesiology, McMaster University, Hamilton, ON, Canada.
Exp Physiol. 2019 Jul;104(7):1126-1135. doi: 10.1113/EP087597. Epub 2019 May 6.
What is the central question of this study? What is the effect of altered shear stress pattern, with or without concurrent neurohumoral and metabolic activation, on the acute endothelial function response assessed via brachial artery flow-mediated dilatation? What is the main finding and its importance? Despite generating distinctive shear stress patterns (i.e. increases in anterograde only, anterograde only with neurohumoral and metabolic activation, and both anterograde and retrograde), similar acute improvements were observed in the brachial artery flow-mediated dilatation response in all conditions, indicating that anterograde and/or turbulent shear stress might be the essential element to induce acute increases in endothelial function.
Endothelial function is influenced by both the direction and the magnitude of shear stress. Acute improvements in endothelial function have mostly been attributed to increased anterograde shear, whereas results from many interventional models in humans suggest that enhancing shear stress in an oscillatory manner (anterograde and retrograde) might be optimal. Here, we determined the acute brachial artery shear stress (SS) and flow-mediated dilatation (FMD) responses to three shear-altering interventions [passive heat stress (HEAT), mechanical forearm compression (CUFF) and handgrip exercise (HGEX)] and examined the relationship between changes in oscillatory shear index (OSI) and changes in FMD. During separate visits, 10 young healthy men (22 ± 3 years old) underwent 10 min of HEAT, CUFF or HGEX in their left forearm. Anterograde and retrograde SS, Reynolds number, OSI and FMD were assessed at rest and during/after each intervention. Anterograde SS increased during all interventions in a stepwise manner (P < 0.05 between interventions), with the change in HGEX (∆37.7 ± 12.2 dyn cm , P < 0.05) > CUFF (∆25.1 ± 11.9 dyn cm , P < 0.05) > HEAT (∆14.5 ± 7.9 dyn cm , P < 0.05). Retrograde SS increased during CUFF (∆-19.6 ± 4.3 dyn cm , P < 0.05). Anterograde blood flow was turbulent (i.e. Reynolds number ≥ |2000|) during all interventions (P < 0.05). The relative FMD improved after all interventions (P = 0.01), and there was no relationship between ∆OSI and ∆FMD. We elicited changes in SS profiles including increased anterograde SS (HEAT and HGEX) and both increased anterograde and retrograde SS (CUFF); regardless of the SS pattern, FMD improved to the same extent. These findings suggest that the presence of anterograde and/or turbulent SS might be the key to optimizing endothelial function in acute assessment protocols.
本研究的核心问题是什么？改变的剪切应力模式（无论是否伴有神经体液和代谢激活）对通过肱动脉血流介导的扩张评估的急性内皮功能反应有何影响？主要发现及其重要性是什么？尽管产生了独特的剪切应力模式（即仅顺行增加、伴有神经体液和代谢激活的仅顺行增加以及顺行和逆行均增加），但在所有情况下肱动脉血流介导的扩张反应中均观察到类似的急性改善，这表明顺行和/或湍流剪切应力可能是诱导内皮功能急性增加的关键因素。
内皮功能受剪切应力的方向和大小影响。内皮功能的急性改善大多归因于顺行剪切增加，而许多人体干预模型的结果表明，以振荡方式（顺行和逆行）增强剪切应力可能是最佳的。在此，我们确定了对三种改变剪切应力的干预措施[被动热应激（HEAT）、机械性前臂压迫（CUFF）和握力运动（HGEX）]的急性肱动脉剪切应力（SS）和血流介导的扩张（FMD）反应，并研究了振荡剪切指数（OSI）变化与FMD变化之间的关系。在单独的访视期间，10名年轻健康男性（22±3岁）对其左前臂进行10分钟的HEAT、CUFF或HGEX。在静息状态以及每次干预期间/之后评估顺行和逆行SS、雷诺数、OSI和FMD。在所有干预过程中，顺行SS均呈逐步增加（干预之间P<0.05），HGEX的变化（∆37.7±12.2dyn/cm，P<0.05）>CUFF（∆25.1±11.9dyn/cm，P<0.05）>HEAT（∆14.5±7.9dyn/cm，P<0.05）。在CUFF期间逆行SS增加（∆-19.6±4.3dyn/cm，P<0.05）。在所有干预过程中顺行血流均为湍流（即雷诺数≥|2000|）（P<0.05）。所有干预后相对FMD均有所改善（P=0.01），且∆OSI与∆FMD之间无相关性。我们引发了SS分布的变化，包括顺行SS增加（HEAT和HGEX）以及顺行和逆行SS均增加（CUFF）；无论SS模式如何，FMD均有相同程度的改善。这些发现表明，顺行和/或湍流SS的存在可能是在急性评估方案中优化内皮功能的关键。
