Clare E Thorn, Phillip E Gates, Francesco Casanova, Alessandro Ramalli, Piero Tortoli, Carlo Palombo, Angela C Shore, Kunihiko Aizawa
{"title":"Interaction of macro- and microvascular function underlies brachial artery flow-mediated dilation in humans.","authors":"Clare E Thorn, Phillip E Gates, Francesco Casanova, Alessandro Ramalli, Piero Tortoli, Carlo Palombo, Angela C Shore, Kunihiko Aizawa","doi":"10.1152/ajpheart.00158.2024","DOIUrl":null,"url":null,"abstract":"<p><p>Brachial artery flow-mediated dilation (BAFMD) is induced by hyperemic wall shear rate (WSR) following forearm ischemia. In older adults, there appears to be a reduced brachial hyperemic WSR and altered stimulus-response relationship compared with young adults. However, it is unclear if an altered forearm microvascular response to ischemia influences brachial hyperemic WSR in older adults. We determined associations between brachial hyperemic WSR and forearm skeletal muscle oxygen saturation in young and older adults. Healthy young (<i>n</i> = 17, 29 ± 7 yr) and older (<i>n</i> = 32, 65 ± 4 yr) adults participated in the study. BAFMD by a multigate spectral Doppler system and forearm skeletal muscle oxygen saturation by near-infrared spectroscopy were concurrently measured. When compared with the young, older adults showed reduced oxygen extraction kinetics (OE, 0.15 [0.12-0.17] vs. 0.09 [0.05-0.12]%s<sup>-1</sup>) and magnitude (So<sub>2deficit</sub>, 3,810 ± 1,420 vs. 2,723 ± 1,240%s) during ischemia, as well as oxygen resaturation kinetics (So<sub>2slope</sub>, 2.5 ± 0.7 vs. 1.7 ± 0.7%s<sup>-1</sup>) upon reperfusion (all <i>P</i> < 0.05). When OE in the young and So<sub>2slope</sub> in older adults were stratified by their median values, young adults with OE above the median had greater hyperemic WSR parameters compared with those below the median (<i>P</i> < 0.05), but So<sub>2slope</sub> in older adults did not show clear differences in hyperemic WSR parameters between those above/below the median. This study demonstrates that, in addition to a reduced microvascular response to ischemia, there may be a dissociation between microvascular response to ischemia and brachial hyperemic WSR in older adults, which may result in a further impairment of BAFMD in this cohort.<b>NEW & NOTEWORTHY</b> Microvascular response to ischemia and subsequent reperfusion is diminished in older adults compared with the young. Furthermore, there appears to be a dissociation between the microvascular response to ischemia and brachial hyperemic WSR in older adults, which may further disturb the BAFMD process in this cohort. A reduced BAFMD in older adults may be a result of multiple alterations occurring both at macro- and microcirculation.</p>","PeriodicalId":7692,"journal":{"name":"American journal of physiology. Heart and circulatory physiology","volume":null,"pages":null},"PeriodicalIF":4.1000,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11380966/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American journal of physiology. Heart and circulatory physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1152/ajpheart.00158.2024","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2024/5/24 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"CARDIAC & CARDIOVASCULAR SYSTEMS","Score":null,"Total":0}
引用次数: 0
Abstract
Brachial artery flow-mediated dilation (BAFMD) is induced by hyperemic wall shear rate (WSR) following forearm ischemia. In older adults, there appears to be a reduced brachial hyperemic WSR and altered stimulus-response relationship compared with young adults. However, it is unclear if an altered forearm microvascular response to ischemia influences brachial hyperemic WSR in older adults. We determined associations between brachial hyperemic WSR and forearm skeletal muscle oxygen saturation in young and older adults. Healthy young (n = 17, 29 ± 7 yr) and older (n = 32, 65 ± 4 yr) adults participated in the study. BAFMD by a multigate spectral Doppler system and forearm skeletal muscle oxygen saturation by near-infrared spectroscopy were concurrently measured. When compared with the young, older adults showed reduced oxygen extraction kinetics (OE, 0.15 [0.12-0.17] vs. 0.09 [0.05-0.12]%s-1) and magnitude (So2deficit, 3,810 ± 1,420 vs. 2,723 ± 1,240%s) during ischemia, as well as oxygen resaturation kinetics (So2slope, 2.5 ± 0.7 vs. 1.7 ± 0.7%s-1) upon reperfusion (all P < 0.05). When OE in the young and So2slope in older adults were stratified by their median values, young adults with OE above the median had greater hyperemic WSR parameters compared with those below the median (P < 0.05), but So2slope in older adults did not show clear differences in hyperemic WSR parameters between those above/below the median. This study demonstrates that, in addition to a reduced microvascular response to ischemia, there may be a dissociation between microvascular response to ischemia and brachial hyperemic WSR in older adults, which may result in a further impairment of BAFMD in this cohort.NEW & NOTEWORTHY Microvascular response to ischemia and subsequent reperfusion is diminished in older adults compared with the young. Furthermore, there appears to be a dissociation between the microvascular response to ischemia and brachial hyperemic WSR in older adults, which may further disturb the BAFMD process in this cohort. A reduced BAFMD in older adults may be a result of multiple alterations occurring both at macro- and microcirculation.
期刊介绍:
The American Journal of Physiology-Heart and Circulatory Physiology publishes original investigations, reviews and perspectives on the physiology of the heart, vasculature, and lymphatics. These articles include experimental and theoretical studies of cardiovascular function at all levels of organization ranging from the intact and integrative animal and organ function to the cellular, subcellular, and molecular levels. The journal embraces new descriptions of these functions and their control systems, as well as their basis in biochemistry, biophysics, genetics, and cell biology. Preference is given to research that provides significant new mechanistic physiological insights that determine the performance of the normal and abnormal heart and circulation.