Zhenkai Zhao, Fiona Elizabeth Smith, Taylor J M Dick, Emma Hodson-Tole
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引用次数: 0
Abstract
Indroduction: Accumulation of intramuscular fat (IMF) is an important marker of skeletal muscle health, typically reported as the mean intramuscular fat fraction (FF) from quantitative magnetic resonance imaging (MRI). However, such a summary measure does not reveal the spatial distribution of the FF through the muscle volume, and currently no methods to quantify intramuscular FF spatial distribution have been reported. This study assessed two- and three-dimensional characteristics of intramuscular FF spatial distribution and investigated age-related differences in intramuscular FF clustering in medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL) muscles.
Methods: A total of 32 physically active young (N = 19, 23.8 ± 2.2 years) and older (N = 13, 70.1 ± 2.2 years) participants were recruited. Intramuscular FF regions were extracted from axial mDixon MRIs using a region-growing method, revealing branch-like clusters, potentially following the vasculature. Three-dimensional intramuscular FF clustering and density were assessed using Delaunay tessellation and Ripley's functions.
Results: Older adults exhibited significantly shorter Delaunay mean edge lengths compared to young (MG: 2.6 ± 0.5 mm vs. 3.2±0.4 mm, p < 0.001; LG: 2.5 ± 0.6 mm vs. 3.3 ± 0.8 mm, p < 0.001; SOL: 2.4 ± 0.4 mm vs. 3.5 ± 0.7 mm, p < 0.001), indicating denser clustering. Ripley's K function confirmed greater clustering in older adults. Two-way ANOVA revealed aging (F statistics = 21, p < 0.001, Hedge's g = 1.8) but not sex (F statistics = 1.5, p = 0.9, Hedge's g = 0.3) as the main effect for variation in intramuscular FF clustering, with no interaction between these two factors (F statistics = 1.3, p = 0.35).
Discussion: This work provides an objective framework for characterizing intramuscular FF spatial distribution, providing a means to track skeletal muscle fatty replacement and provide more robust and sensitive markers of skeletal muscle health.
肌内脂肪积累（IMF）是骨骼肌健康的重要标志，通常以定量磁共振成像（MRI）的平均肌内脂肪分数（FF）报道。然而，这种总结性测量并不能通过肌肉体积揭示FF的空间分布，目前也没有量化肌肉内FF空间分布的方法报道。本研究评估了肌肉内FF空间分布的二维和三维特征，并研究了腓肠肌内侧（MG）、腓肠肌外侧（LG）和比目鱼肌（SOL）肌肉内FF聚类的年龄相关差异。方法：共招募32名身体活跃的年轻人（N = 19, 23.8±2.2岁）和老年人（N = 13, 70.1±2.2岁）。使用区域生长方法从轴向mDixon mri中提取肌内FF区域，显示树枝状簇，可能跟随脉管系统。采用Delaunay镶嵌和Ripley函数评估肌肉内三维FF聚类和密度。结果：老年人的Delaunay平均边缘长度明显短于年轻人(MG: 2.6±0.5 mm比3.2±0.4 mm, p < 0.001；LG: 2.5±0.6 mm vs. 3.3±0.8 mm, p < 0.001；SOL: 2.4±0.4 mm vs. 3.5±0.7 mm, p < 0.001)，表明聚类更密集。里普利的K函数证实了老年人的聚集性更强。双向方差分析显示，年龄（F统计量= 21,p < 0.001, Hedge's g = 1.8）是肌肉内FF聚类变化的主要影响因素，而性别（F统计量= 1.5,p = 0.9, Hedge's g = 0.3）不是主要影响因素，两者之间无交互作用（F统计量= 1.3,p = 0.35）。讨论：这项工作为表征肌肉内FF空间分布提供了一个客观框架，提供了一种跟踪骨骼肌脂肪替代的手段，并提供了骨骼肌健康的更健壮和敏感的标志物。
期刊介绍：
The translation of new discoveries in medicine to clinical routine has never been easy. During the second half of the last century, thanks to the progress in chemistry, biochemistry and pharmacology, we have seen the development and the application of a large number of drugs and devices aimed at the treatment of symptoms, blocking unwanted pathways and, in the case of infectious diseases, fighting the micro-organisms responsible. However, we are facing, today, a dramatic change in the therapeutic approach to pathologies and diseases. Indeed, the challenge of the present and the next decade is to fully restore the physiological status of the diseased organism and to completely regenerate tissue and organs when they are so seriously affected that treatments cannot be limited to the repression of symptoms or to the repair of damage. This is being made possible thanks to the major developments made in basic cell and molecular biology, including stem cell science, growth factor delivery, gene isolation and transfection, the advances in bioengineering and nanotechnology, including development of new biomaterials, biofabrication technologies and use of bioreactors, and the big improvements in diagnostic tools and imaging of cells, tissues and organs.
In today`s world, an enhancement of communication between multidisciplinary experts, together with the promotion of joint projects and close collaborations among scientists, engineers, industry people, regulatory agencies and physicians are absolute requirements for the success of any attempt to develop and clinically apply a new biological therapy or an innovative device involving the collective use of biomaterials, cells and/or bioactive molecules. “Frontiers in Bioengineering and Biotechnology” aspires to be a forum for all people involved in the process by bridging the gap too often existing between a discovery in the basic sciences and its clinical application.
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