Department of Physical Therapy, University of Florida, Gainesville, Florida.
Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida.
J Appl Physiol (1985). 2021 Jul 1;131(1):83-94. doi: 10.1152/japplphysiol.00634.2020. Epub 2021 May 20.
Duchenne muscular dystrophy (DMD) is characterized by a progressive replacement of muscle by fat and fibrous tissue, muscle weakness, and loss of functional abilities. Impaired vasodilatory and blood flow responses to muscle activation have also been observed in DMD and associated with mislocalization of neuronal nitric oxide synthase mu (nNOSμ) from the sarcolemma. The objective of this study was to determine whether the postcontractile blood oxygen level-dependent (BOLD) MRI response is impaired in DMD and correlated with established markers of disease severity in DMD, including MRI muscle fat fraction (FF) and clinical functional measures. Young boys with DMD ( = 16, 5-14 yr) and unaffected controls ( = 16, 5-14 yr) were evaluated using postcontractile BOLD, FF, and functional assessments. The BOLD response was measured following five brief (2 s) maximal voluntary dorsiflexion contractions, each separated by 1 min of rest. FFs from the anterior compartment lower leg muscles were quantified via chemical shift-encoded imaging. Functional abilities were assessed using the 10 m walk/run and the 6-min walk distance (6MWD). The peak BOLD responses in the tibialis anterior and extensor digitorum longus were reduced ( < 0.001) in DMD compared with controls. Furthermore, the anterior compartment peak BOLD response correlated with function (6MWD ρ = 0.87, < 0.0001; 10 m walk/run time ρ = -0.78, < 0.001) and FF (ρ = -0.52, = 0.05). The reduced postcontractile BOLD response in DMD may reflect impaired microvascular function. The relationship observed between the postcontractile peak BOLD response and functional measures and FF suggests that the BOLD response is altered with disease severity in DMD. This study examined the postcontractile blood oxygen level-dependent (BOLD) response in boys with Duchenne muscular dystrophy (DMD) and unaffected controls, and correlated this measure to markers of disease severity. Our findings indicate that the postcontractile BOLD response is impaired in DMD after brief muscle contractions, is correlated to disease severity, and may be valuable to implement in future studies to evaluate treatments targeting microvascular function in DMD.
杜氏肌营养不良症（DMD）的特征是肌肉逐渐被脂肪和纤维组织取代，肌肉无力，功能丧失。在 DMD 中还观察到肌肉活动引起的血管舒张和血流反应受损，并且与神经元型一氧化氮合酶 μ（nNOSμ）从肌膜的定位错误有关。本研究的目的是确定 DMD 患者的收缩后血氧水平依赖（BOLD）MRI 反应是否受损，并与 DMD 中已建立的疾病严重程度标志物相关，包括 MRI 肌肉脂肪分数（FF）和临床功能测量。使用收缩后 BOLD、FF 和功能评估来评估患有 DMD 的年轻男孩（n = 16，5-14 岁）和未受影响的对照组（n = 16，5-14 岁）。BOLD 反应是在五次短暂（2s）最大自愿背屈收缩后测量的，每次收缩之间休息 1 分钟。通过化学位移编码成像量化前小腿肌肉的 FF。通过 10m 步行/跑和 6min 步行距离（6MWD）评估功能能力。与对照组相比，DMD 患者的胫骨前肌和趾长伸肌的峰值 BOLD 反应降低（<0.001）。此外，前室峰值 BOLD 反应与功能（6MWD ρ=0.87，<0.0001；10m 步行/跑时间 ρ=-0.78，<0.001）和 FF（ρ=-0.52，=0.05）相关。DMD 中收缩后 BOLD 反应降低可能反映了微血管功能受损。观察到收缩后峰值 BOLD 反应与功能测量和 FF 之间的关系表明，BOLD 反应随着 DMD 疾病严重程度而改变。本研究检查了患有杜氏肌营养不良症（DMD）的男孩和未受影响的对照组的收缩后血氧水平依赖（BOLD）反应，并将该测量值与疾病严重程度的标志物相关联。我们的研究结果表明，在短暂的肌肉收缩后，DMD 中的收缩后 BOLD 反应受损，与疾病严重程度相关，并且可能对未来评估针对 DMD 中微血管功能的治疗方法的研究有价值。
