Evaluation of a novel model of skeletal muscle fatigue

骨骼肌疲劳新模型的评估

• 批准号: RGPIN-2015-05113
• 负责人: Macintosh, Brian
• 金额: $ 2.04万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=682338
• 关键词: Evaluation; novel; model; skeletal; muscle

Skeletal muscle fatigue, is a common experience that has fascinated scientists for centuries, yet the cellular processes impacting contractile properties during and following repeated activations are not understood. Most theories of fatigue considered build-up of products of metabolism and inhibition of the contractile response. This is not consistent with the known primary mechanism of fatigue: inhibition of excitation-contraction coupling (E-CC). It is time to study how E-CC is impaired. An innovative explanation for muscle fatigue is proposed: fatigue is a consequence of cellular regulation of E-CC to preserve energy charge in the muscle. Experiments are proposed to test this theory as well as alternative theories. Experiments are proposed using: single fibre, fibre bundles and whole muscle at physiological temperature. It has been demonstrated that fatigue mechanisms at room temperature are not relevant at physiological temperature. A second innovative and practical aspect of the proposed studies is contractions under consideration will be sub maximal, like natural contractions in common movements. ****If the theory is correct, then changing cellular energy charge should result in altered E-CC, on a contraction-to-contraction basis and in steady state. For example, stretching a muscle to increase active force and ATP turnover, without changing cross-membrane ion exchange associated with activation will result in attenuation of subsequent Ca2+ release.  Free [Ca2+] will be measured in single fibre experiments to detect any changes in Ca2+ transients. Measuring average free [Ca2+] during contractions over a range of frequencies reveals the force-pCa2+ relationship. Regulation of the ryanodine receptor is thought to occur by increases in Ca2+-calmodulin binding and/or binding of Mg2+. The potential impact of Ca2+-calmodulin may be limited once RyR inhibition is achieved. Decreased free [Ca2+] will result in less Ca2+-calmodulin. This will be assessed in whole muscle with a bioassay by looking at myosin light chain phosphorylation, permitting the first assessment of Ca2+ transients in whole muscle. The possibility that decreases in light chain phosphorylation contributes to impaired Ca2+ sensitivity will also be considered.  ***The proposed experiments will provide evidence for how the regulation of E-CC can result in fatigue, advancing our knowledge in a field of study that requires some novel thinking. The proposed work represents a new direction for the study of muscle fatigue and should be remarkably revealing in support of a new model of this common yet intriguing property of skeletal muscle.

骨骼肌疲劳是一种常见的经历，几个世纪以来一直让科学家们着迷，但在重复激活期间和之后影响收缩特性的细胞过程尚不清楚。大多数疲劳理论都考虑了代谢产物的积累和收缩反应的抑制。这与已知的疲劳主要机制不一致：抑制兴奋-收缩耦合（E-CC）。现在是研究 E-CC 如何受损的时候了。对肌肉疲劳提出了一种创新的解释：疲劳是 E-CC 细胞调节以保存肌肉能量的结果。提出了实验来检验该理论以及替代理论。实验建议使用：生理温度下的单纤维、纤维束和整个肌肉。已经证明，室温下的疲劳机制与生理温度无关。拟议研究的第二个创新和实用方面是所考虑的收缩将是次最大的，就像常见运动中的自然收缩一样。 ****如果这个理论是正确的，那么在收缩到收缩的基础上并且在稳定状态下，改变细胞能量电荷应该会导致 E-CC 的改变。例如，拉伸肌肉以增加主动力和 ATP 周转，而不改变与激活相关的跨膜离子交换，将导致随后的 Ca2+ 释放减弱。  将在单纤维实验中测量游离 [Ca2+]，以检测 Ca2+ 瞬变的任何变化。在一定频率范围内测量收缩期间的平均游离 [Ca2+] 揭示了力与 pCa2+ 的关系。人们认为兰尼碱受体的调节是通过增加 Ca2+-钙调蛋白结合和/或 Mg2+ 结合来实现的。一旦实现 RyR 抑制，Ca2+-钙调蛋白的潜在影响可能会受到限制。游离 [Ca2+] 减少将导致 Ca2+-钙调蛋白减少。 这将通过观察肌球蛋白轻链磷酸化的生物测定在整个肌肉中进行评估，从而允许首次评估整个肌肉中的 Ca2+ 瞬变。还将考虑轻链磷酸化减少导致 Ca2+ 敏感性受损的可能性。  ***拟议的实验将为 E-CC 的调节如何导致疲劳提供证据，从而提高我们在需要一些新颖思维的研究领域的知识。拟议的工作代表了肌肉疲劳研究的新方向，并且应该具有显着的启示意义，以支持骨骼肌这种常见但有趣的特性的新模型。