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Mechanotransduction Mechanisms of Hypertrophy and Performance with Resistance Exercise
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Andrew C. Fry, Justin X. Nicoll, Luke A. Olsen
The ability of a single muscle fibre to produce force is largely dependent upon many of the structural proteins previously discussed. As mentioned earlier, the force-generating unit of the skeletal muscle is the sarcomere. The sarcomere can transmit force in two directions, laterally (perpendicular to the length of the muscle fibre, i.e., toward the plasma membrane) and longitudinally (parallel to the length of the muscle fibre toward the myotendinous junction). It has been demonstrated that ∼80% of force produced from a muscle fibre is transmitted in a lateral direction (142). This lateral force transmission is propagated from the sarcomere, through the cytoskeleton, across the costamere (i.e., integrins and other transmembrane proteins), to the ECM, and ultimately to the tendon to initiate movement. Consequently, modes of exercise which reinforce proteins within these lateral pathways, namely those most active during eccentric muscle actions, are proposed to improve muscle force production, transmission, and structural integrity.
Defining ambulation status in patients with Duchenne muscular dystrophy using the 10-metre walk test and the motor function measure scale
Published in Disability and Rehabilitation, 2023
Danila Cristina Petian-Alonso, Ani Caroline de Castro, Gabriela Barroso de Queiroz Davoli, Edson Zangiacomi Martinez, Ana Claudia Mattiello-Sverzut
Duchenne muscular dystrophy (DMD) affects children at a rate of 1:5,000 births [1]. It is an inherited disease associated with a mutation in the gene located in the Xp21 locus, which is responsible for encoding the dystrophin protein [2]. This mutation can be a deletion, duplication, or other rearrangement that interrupts RNA reading. Dystrophin is a costamere protein linked to the dystrophin-glycoprotein complex that longitudinally stabilizes intracellular elements during muscle contractions [2,3]. The absence of dystrophin favours skeletal and cardiac muscle damage due to the destabilization of the sarcolemma and consequent greater susceptibility to injury and fibre necrosis [4]. Therefore, patients with DMD have a diffuse and recurrent condition of muscle fibre injury that culminates in the replacement of muscle by fibroadipose tissue [5].
The potential of utrophin modulators for the treatment of Duchenne muscular dystrophy
Published in Expert Opinion on Orphan Drugs, 2018
Simon Guiraud, David Roblin, Davies. E. Kay
The gene for Duchenne muscular dystrophy (DMD, MIM no. 310200), an X-linked progressive muscle wasting disorder affecting 1:5000 boys [1,2], was identified 30 years ago [3]. Patients have progressive muscle weakness from late childhood and lose the ability to walk around the age of 12 and die in their late 20s [4]. The gene is the largest in the human genome (2.3 megabases) and the disease shows one of the highest new mutation rates which results predominantly in deletions of the gene. The 14-kb RNA transcript is encoded by 79 exons and is expressed predominantly in muscle and at lower levels in brain. The corresponding protein, dystrophin, is a 427-kDa cytoplasmic protein which provides an essential structural link between the dystrophin-associated protein complex at the sarcolemma and the costameric actin which maintains the biomechanical properties of fiber strength, flexibility, and stability in skeletal muscle (Figure 1(a)) [5,6]. Absence in DMD or reduction of dystrophin in the milder Becker Muscular dystrophy (BMD, MIM no. 300376) [7] leads to costamere perturbation, sarcolemma fragility, and subsequent chronic inflammation associated with a failed regeneration process leading to necrotic and fibrotic events and ultimately loss of muscle fibers and reduction in muscle mass and function muscle (Figure 1(c)) [8,9].