Skeletal Muscle Fiber Types in Neuromuscular Diseases

Abstract

In the human body, there are 600 individual skeletal muscles that allow us to perform a variety of functions such as executing locomotive tasks, breathing, and moving our eyes. The ratio of fiber types within the muscle critically contributes to determine the function of these muscles. Significant changes of muscle fiber types occur not only in normal development; changes have also been observed under abnormal conditions in neuromuscular disorders. In this review, we describe how muscle fiber types are specified during embryonic myogenesis, what potential factors are involved in the changes of fiber type composition, and how fiber type variations are influenced by the pathological conditions under specific neuromuscular disorders. Understanding skeletal muscle at the individual fiber level aids in studying the normal physiology and the pathology of disease in human.

Fiber Metabolism, Procollagen and Collagen Type III Immunoreactivity in Broiler Pectoralis Major Affected by Muscle Abnormalities

“…Indeed, in their early stage, dystrophies primarily affect type IIB fibers, whereas those having oxidative metabolism are involved only as the dystrophic condition get worse [24]. Therefore, the conversion from type IIB to type I fibers (as depicted by the increased proportion of fibers positively stained to NADH-TR and by the concurrent reduction in those exhibiting a positive reaction to α-GPD) may be considered as a compensatory mechanism to alleviate the symptoms and slow down the progression of the diseases, as previously hypothesized by Glaser and Masatoshi [25]. In agreement with this, the occurrence of a fiber type switching from type IIB to type I has been hypothesized to take place in WB and WS/WB-affected muscles [26,27] in which an upregulation of genes potentially indicating fiber-type switching following myofiber damage was observed.…”

Hypoxia and Hypoxia-Inducible Factor Signaling in Muscular Dystrophies: Cause and Consequences

“…Fiber types are not affected in the same way in all MDs [139]. In DMD, destruction of type II muscle fibers is an early event while type I muscle fibers are lost at later stages [140].…”

Neuromuscular defects after infection with a beta coronavirus in mice

“…To our knowledge, our study is the first to address systematically the fiber type composition and individual fiber CSA in a COVID-19 mice model. Fiber type switch is present in several neuromuscular diseases ( Glaser and Suzuki 2018 ; Molotsky et al, 2022 ), consisting of a common compensatory muscle response. Improving muscle function plays a significant role in the recovery from critical illness either by increasing muscle mass or strength ( Wolfe, 2006 ).…”