Flow-mediated dilation stimulated by sustained increases in shear stress: A useful tool for assessing endothelial function in humans?

Investigations of human conduit artery endothelial function via flow-mediated vasodilation (FMD) have largely been restricted to the reactive hyperemia (RH) technique, wherein a transient increase in shear stress following the release of limb occlusion stimulates upstream conduit artery vasodilation (RH-FMD). FMD can also be assessed in response to sustained increases in shear stress (sustained stimulus (SS)-FMD), most often created with limb heating or exercise. Exercise in particular creates a physiologically-relevant stimulus because shear stress increases, and FMD occurs, during typical day-to-day activity. Several studies have identified that various conditions and acute interventions have a disparate impact on RH- versus SS-FMD, sometimes with only the latter demonstrating impairment. Indeed, evidence suggests that transient (RH) and sustained (SS) shear stress stimuli may be transduced via different signaling pathways, and as such, SS-FMD and RH-FMD appear to offer unique insight regarding endothelial function. The present review describes the techniques used to assess SS-FMD and summarizes the evidence regarding i) SS-FMD as an index of endothelial function in humans, highlighting comparisons with RH-FMD, and ii) potential differences in shear stress transduction and vasodilator production stimulated by transient versus sustained shear stress stimuli. The evidence suggests that SS-FMD is a useful tool to assess endothelial function and further research is required to characterize the mechanisms involved and its association with long-term cardiovascular outcomes. Copyright © 2017, American Journal of Physiology-Heart and Circulatory Physiology.

Citation

Joshua C Tremblay, Kyra Ellen Pyke. Flow-mediated dilation stimulated by sustained increases in shear stress: A useful tool for assessing endothelial function in humans? American journal of physiology. Heart and circulatory physiology. 2017 Nov 22:ajpheart.00534.2017

PMID: 29167121

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