Elashry Mohamed I, Matsakas Antonios, Wenisch Sabine, Arnhold Stefan, Patel Ketan
Anatomy and Embryology Department, Faculty of Veterinary Medicine, University of Mansoura, 35516, Egypt; Institute of Veterinary Anatomy, Histology and Embryology, Justus Liebig University of Giessen, 35392, Germany.
Hull York Medical School, University of Hull, United Kingdom.
Acta Histochem. 2017 Jun;119(5):582-591. doi: 10.1016/j.acthis.2017.06.002. Epub 2017 Jun 15.
Skeletal muscle mass loss has a broad impact on body performance and physical activity. Muscle wasting occurs due to genetic mutation as in muscular dystrophy, age-related muscle loss (sarcopenia) as well as in chronic wasting disorders as in cancer cachexia. Food restriction reduces muscle mass underpinned by increased muscle protein break down. However the influence of dietary restriction on the morphometry and phenotype of forelimb muscles in a genetically modified myostatin null mice are not fully characterized. The effect of a five week dietary limitation on five anatomically and structurally different forelimb muscles was examined. C57/BL6 wild type (Mstn) and myostatin null (Mstn) mice were either given a standard rodent normal daily diet ad libitum (ND) or 60% food restriction (FR) for a 5 week period. M. triceps brachii Caput laterale (T.lateral), M. triceps brachii Caput longum (T.long), M. triceps brachii Caput mediale (T.medial), M. extensor carpi ulnaris (ECU) and M. flexor carpi ulnaris (FCU) were dissected, weighted and processed for immunohistochemistry. Muscle mass, fibers cross sectional areas (CSA) and myosin heavy chain types IIB, IIX, IIA and type I were analyzed. We provide evidence that caloric restriction results in muscle specific weight reduction with the fast myofibers being more prone to atrophy. We show that slow fibers are less liable to dietary restriction induced muscle atrophy. The effect of dietary restriction was more pronounced in Mstn muscles to implicate the oxidative fibers compared to Mstn. Furthermore, peripherally located myofibers are more susceptible to dietary induced reduction compared to deep fibers. We additionally report that dietary restriction alters the glycolytic phenotype of the Mstn into the oxidative form in a muscle dependent manner. In summary our study shows that calorie restriction alters muscle fiber profile of forelimb muscles of Myostatin null mice.
骨骼肌质量损失对身体机能和体力活动有着广泛影响。肌肉萎缩可由基因突变引起，如在肌肉萎缩症中；也可因年龄相关的肌肉流失（肌肉减少症）以及慢性消耗性疾病导致，如癌症恶病质。食物限制会因肌肉蛋白分解增加而导致肌肉质量下降。然而，饮食限制对基因改造的肌肉生长抑制素基因敲除小鼠前肢肌肉形态测量和表型的影响尚未完全明确。本研究检测了为期五周的饮食限制对五种解剖结构和结构不同的前肢肌肉的影响。将C57/BL6野生型（Mstn）和肌肉生长抑制素基因敲除（Mstn）小鼠随机分为两组，一组给予标准啮齿动物正常每日饮食（ND），另一组给予60%食物限制（FR），持续5周。解剖肱三头肌外侧头（T.lateral）、肱三头肌长头（T.long）、肱三头肌内侧头（T.medial）、尺侧腕伸肌（ECU）和尺侧腕屈肌（FCU），称重并进行免疫组织化学处理。分析肌肉质量、纤维横截面积（CSA）以及肌球蛋白重链IIB、IIX、IIA和I型。我们提供的证据表明，热量限制会导致肌肉特异性重量减轻，其中快肌纤维更容易萎缩。我们发现慢肌纤维对饮食限制诱导的肌肉萎缩不太敏感。与Mstn相比，饮食限制对Mstn肌肉中氧化纤维的影响更为明显。此外，与深层纤维相比，位于外周的肌纤维对饮食诱导的减少更为敏感。我们还报告称，饮食限制会以肌肉依赖的方式将Mstn的糖酵解表型转变为氧化形式。总之，我们的研究表明，热量限制会改变肌肉生长抑制素基因敲除小鼠前肢肌肉的纤维分布。
