Sakamoto Rintaro, Kamoda Tatsuki, Ogoh Shigehiko, Sato Kohei, Katayose Masaki, Neki Toru, Iwamoto Erika
Graduate School of Health Science, Sapporo Medical University, Sapporo, Japan.
Japan Society for the Promotion of Science, Tokyo, Japan.
J Appl Physiol (1985). 2025 Feb 1;138(2):397-403. doi: 10.1152/japplphysiol.00774.2024. Epub 2024 Dec 26.
Peripheral endothelial function, which accounts for the variability in shear stimulus, can be assessed using shear-mediated dilation normalized to the increased shear stimulus. Similarly, shear-mediated dilation of the internal carotid artery (ICA), an index of cerebrovascular endothelial function, should be normalized to increased shear stimulus. However, this approach has not yet been validated. Thus, the shear-mediated dilation of the ICA was assessed in 14 young adults during three levels of transient hypercapnia, induced by elevating the partial pressure of end-tidal carbon dioxide for 30 s by 6, 9, and 12 mmHg. The ICA shear rate (SR) was calculated using the ICA diameter and velocity, both measured by Doppler ultrasound. The total vasodilator stimulus was quantified as the SR area under the curve from the onset of hypercapnia to peak dilation, including and excluding baseline values [(SR) and delta SR (SR), respectively]. Shear-mediated dilation was calculated as the percent increase in diameter from baselines. ICA dilation was positively associated with SR [r = 0.47, < 0.01] but not with SR [r = 0.32, = 0.09]. Consequently, ICA dilation normalized to SR did not differ among trials (main effect of rial, = 0.77). Contrarily, the difference in ICA dilation among trials remained significant when normalized to SR (main effect of trial, = 0.02). Therefore, normalized shear-mediated dilation using SR can reduce variability associated with increased shear stimulus during ICA dilation assessment, thereby enhancing the validity of evaluating cerebrovascular endothelial function. This study demonstrated that shear-mediated dilation of the internal carotid artery (ICA), an index of cerebrovascular endothelial function, increased with the increase of shear stimulus induced by different degrees of transient hypercapnia. However, when ICA dilation was normalized to the total increased shear stimulus above baseline, the vasodilation became comparable across different hypercapnia levels. Thus, normalizing ICA dilation to the total shear stimulus increased from baseline may enhance the validity of assessing cerebrovascular endothelial function.
外周内皮功能可通过将剪切介导的扩张标准化为增加的剪切刺激来评估，它解释了剪切刺激的变异性。同样，作为脑血管内皮功能指标的颈内动脉（ICA）的剪切介导扩张，也应标准化为增加的剪切刺激。然而，这种方法尚未得到验证。因此，在14名年轻成年人中，通过将呼气末二氧化碳分压在30秒内分别升高6、9和12 mmHg来诱导三种水平的短暂高碳酸血症，评估ICA的剪切介导扩张。ICA剪切率（SR）使用通过多普勒超声测量的ICA直径和速度来计算。总血管扩张刺激被量化为从高碳酸血症发作到扩张峰值的曲线下SR面积，分别包括和排除基线值[（SR）和δSR（SR）]。剪切介导扩张计算为直径相对于基线的增加百分比。ICA扩张与SR呈正相关[r = 0.47，P < 0.01]，但与δSR不相关[r = 0.32，P = 0.09]。因此，标准化为SR的ICA扩张在各试验之间没有差异（试验的主效应，P = 0.77）。相反，当标准化为δSR时，各试验之间ICA扩张的差异仍然显著（试验的主效应，P = 0.02）。因此，在ICA扩张评估中，使用SR进行标准化的剪切介导扩张可以减少与增加的剪切刺激相关的变异性，从而提高评估脑血管内皮功能的有效性。本研究表明，作为脑血管内皮功能指标的颈内动脉（ICA）的剪切介导扩张，随着不同程度短暂高碳酸血症诱导的剪切刺激增加而增加。然而，当ICA扩张标准化为高于基线的总增加剪切刺激时，不同高碳酸血症水平下的血管扩张变得可比。因此，将ICA扩张标准化为从基线增加的总剪切刺激可能会提高评估脑血管内皮功能的有效性。
