Gender differences in microvascular function across muscles in the lower leg using blood-oxygen level dependent MR Imaging
Author
Molbo, Lars
Term
4. semester
Education
Publication year
2019
Submitted on
2019-06-06
Pages
15
Abstract
Kønsskelleforskelle i makrokarfunktion er velbeskrevet, men mindre vides om mikrokar. Dette studie undersøgte, om køn påvirker mikrokarresponser i fire underbensmuskler ved hjælp af blod-oxygen-niveaurelateret (BOLD) MR under reaktiv hyperæmi. Tredive raske, unge voksne (18 mænd, 12 kvinder) gennemgik 5 minutters lårmanchetalklusion efterfulgt af 2 minutters reperfusion i en 3T MR-scanner. Tibialis anterior, peroneergruppen, soleus og mediale gastrocnemius blev manuelt segmenteret på T2-vægtede billeder og overført til BOLD-MR ved multimodal billedregistrering. Tidsserier i signalintensitet blev normaliseret, og time-to-peak (TTP), time-to-half-peak (TTHP) og hyperemic peak value (HPV) blev beregnet og sammenlignet med tovejs gentagne målinger ANOVA (køn, muskel). Kvinder havde signifikant kortere TTP og TTHP end mænd på tværs af alle muskler, mens der ikke sås kønsforskel i HPV. På tværs af muskler var TTP og TTHP kortere i tibialis anterior end i peroneergruppen, soleus og mediale gastrocnemius, og HPV var større i soleus end i tibialis anterior og mediale gastrocnemius. Resultaterne tyder på hurtigere mikrokarresponser hos kvinder, men tilsvarende topvasodilationsstørrelse hos sunde unge mænd og kvinder. Selvom mekanismerne ikke blev undersøgt, kan lavere sympatikusaktivitet hos kvinder være en mulig forklaring. TTP og TTHP gav ens konklusioner, og TTHP foreslås som et mere robust, operatøruafhængigt mål. Fundene bidrager med ny viden om kønseffekter på mikrokarfunktion i underbenets muskler.
Sex differences in macrovascular function are well documented, but much less is known about the microvasculature. This study examined whether sex influences microvascular responses in four lower-leg muscles using blood-oxygen-level-dependent (BOLD) MRI during reactive hyperemia. Thirty healthy, young adults (18 men, 12 women) underwent 5 minutes of thigh cuff occlusion followed by 2 minutes of reperfusion in a 3T MRI scanner. Tibialis anterior, the peroneal group, soleus, and medial gastrocnemius were manually segmented on T2-weighted images and transferred to BOLD-MRI via multimodal image registration. Signal intensity time courses were normalized, and time-to-peak (TTP), time-to-half-peak (TTHP), and hyperemic peak value (HPV) were computed and compared using mixed-design two-way repeated measures ANOVA (sex, muscle). Women had significantly shorter TTP and TTHP than men across all muscles, whereas HPV did not differ by sex. Across muscles, TTP and TTHP were shorter in tibialis anterior than in the peroneal group, soleus, and medial gastrocnemius, and HPV was higher in soleus than in tibialis anterior and medial gastrocnemius. These findings indicate faster microvascular responses in women but similar peak vasodilatory magnitude in healthy young men and women. Although mechanisms were not assessed, lower sympathetic nerve activity in women is a possible explanation. TTP and TTHP yielded similar conclusions, with TTHP suggested as a more robust, operator-independent metric. The results add new insight into sex effects on microvascular function in lower-leg muscles.
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