Variations of fresh meat quality exist because the quality traits are affected by various intrinsic and extrinsic factors. Because the meat quality is basically dependent on muscle fiber ...characteristics, numerous studies have reported the relationship between quality traits and fiber characteristics. Despite intensive research, the relationship is yet to be fully established, however, the present knowledge suggests several potential ways to manipulate muscle fiber characteristics to improve meat quality. The present paper reviews the definition of fresh meat quality, meat quality traits and variations of meat quality. Also, this review presents recent knowledge underlying the relationship between fresh meat quality traits and muscle fiber characteristics. Finally, the present work proposes several potential factors including breed, genotype, sex, hormone, growth performance, diet, muscle location, exercise and ambient temperature that can be used to manipulate muscle fiber characteristics and subsequently meat quality in animals.
•Fresh meat qualities are affected by various intrinsic and extrinsic factors.•The meat quality is basically dependent on muscle fiber characteristics.•The meat quality can be improved by manipulation of muscle fiber characteristics.•Muscle fiber characteristics can be controlled by various potential factors.
Muscle wasting occurs in a variety of conditions, including both genetic diseases, such as muscular dystrophies, and acquired disorders, ranging from muscle disuse to cancer cachexia, from heart ...failure to aging sarcopenia. In most of these conditions, the loss of muscle tissue is not homogeneous, but involves specific muscle groups, for example Duchenne muscular dystrophy affects most body muscles but spares extraocular muscles, and other dystrophies affect selectively proximal or distal limb muscles. In addition, muscle atrophy can affect specific fiber types, involving predominantly slow type 1 or fast type 2 muscle fibers, and is frequently accompanied by a slow-to-fast or fast-to-slow fiber type shift. For example, muscle disuse, such as spinal cord injury, causes type 1 fiber atrophy with a slow-to-fast fiber type shift, whereas cancer cachexia leads to preferential atrophy of type 2 fibers with a fast-to-slow fiber type shift. The identification of the signaling pathways responsible for the differential response of muscles types and fiber types can lead to a better understanding of the pathogenesis of muscle wasting and to the design of therapeutic interventions appropriate for the specific disorders.
This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.
Peroxisome proliferator‐activated receptor gamma (PPARγ) is a master regulator of adipogenesis and lipogenesis. To understand its roles in fiber formation and fat deposition in skeletal muscle, we ...successfully generated muscle‐specific overexpression of PPARγ in two pig models by random insertion and CRISPR/Cas9 transgenic cloning procedures. The content of intramuscular fat was significantly increased in PPARγ pigs while had no changes on lean meat ratio. PPARγ could promote adipocyte differentiation by activating adipocyte differentiating regulators such as FABP4 and CCAAT/enhancer‐binding protein (C/EBP), along with enhanced expression of LPL, FABP4, and PLIN1 to proceed fat deposition. Proteomics analyses demonstrated that oxidative metabolism of fatty acids and respiratory chain were activated in PPARγ pigs, thus, gathered more Ca2+ in PPARγ pigs. Raising of Ca2+ could result in increased phosphorylation of CAMKII and p38 MAPK in PPARγ pigs, which can stimulate MEF2 and PGC1α to affect fiber type and oxidative capacity. These results support that skeletal muscle‐specific overexpression of PPARγ can promote oxidative fiber formation and intramuscular fat deposition in pigs.
Different forms of myosin heavy chains (MyHCs), coded by a large family of sarcomeric MYH genes, are expressed in striated muscles. The generation of specific anti‐MyHC antibodies has provided a ...powerful tool to define the fiber types present in skeletal muscles, their functional properties, their response to conditions that affect muscle plasticity and their changes in muscle disorders. Cardiomyocyte heterogeneity has been revealed by the serendipitous observation that different MyHCs are present in atrial and ventricular myocardium and in heart conduction tissue. Developmental MyHCs present in embryonic and fetal/neonatal skeletal muscle are re‐expressed during muscle regeneration and can be used to identify regenerating fibers in muscle diseases. MyHC isoforms provide cell type‐specific markers to identify the signaling pathways that control muscle cell identity and are an essential reference to interpret the results of single‐cell transcriptomics and proteomics.
Skeletal muscles consist of different fiber types that can be identified by immunohistochemistry using antibodies that recognize distinct myosin isoforms. In human skeletal muscle antimyosin staining reveals three major fiber types, type 1, 2A, and 2X, and a number of hybrid fibers with mixed myosin composition.
Case-controlled animal study.
To investigate whether multifidus muscle fibre type distribution changes in models of interverbal disc (IVD) degeneration and whether this is resolved by physical ...activity.
The loss of slow type I muscle fibres in the multifidus muscle in people with low back pain is contentious. Data from animal models of IVD degeneration suggest some discrepancies in human studies might be explained by the dependence of slow muscle fibre changes and their underlying mechanisms, on the time since injury and progression of IVD degeneration. It is not yet resolved what changes are apparent once the chronic phase is established. It is also not known whether muscle fibre changes can be resolved by whole body physical activity. This study aimed to examine slow fibre distribution in the multifidus muscle in models of IVD injury or spontaneous degeneration in animals with or without exposure to physical activity.
Two models of IVD degeneration were used. The first used a genetically modified mouse (SPARC-null) that spontaneously develops IVD degeneration. The second model involved a surgically induced IVD lesion to induce degeneration. Mice in each study were allocated to housing with or without a running wheel for physical activity. At 12 months of age, the multifidus muscle was harvested. Slow muscle fibre distribution and the mRNA expression of genes associated with muscle fibre type transformation were examined.
The proportion and cross-sectional area of slow muscle fibres were reduced in both models of IVD degeneration compared to controls, without evidence of ongoing fibre transformation. Whole-body physical activity did not attenuate these alterations.
Results confirmed slow muscle fibre loss in the multifidus in the chronic phase of IVD degeneration induced spontaneously and by injury. Whole-body physical activity did not attenuate changes to muscle fibre distribution. More specific approaches to muscle activation might be required to achieve more complete reversal of muscle fibre changes, with potential implications for therapy in humans.Level of Evidence: N/A.
El estudio de las fibras musculares permite comprender con mejor detalle la composición de los músculos y sus características funcionales. Además, facilita la aplicación de programas de ...entrenamiento y rehabilitación basados en las vías energéticas que regulan la contracción muscular. Su estudio generalmente va unido al análisis de las cadenas pesadas de miosina (MHC), las que informan sobre las características y propiedades funcionales del músculo. El objetivo de este trabajo fue sintetizar la evidencia científica disponible sobre la distribución de fibras musculares y de isoformas de cadenas pesadas de miosina de los músculos intrínsecos de la laringe de seres humanos. Se realizó una revisión sistemática de la literatura mediante el análisis de artículos encontrados en las bases de datos PubMed, EBSCOHost y SciELO. Los hallazgos informan sobre la existencia de fibras tónicas lentas y tipo I, II, IIA y IIX/IIB. Además, se reconoce la presencia de las isoformas MHC-I, MHC-IIA, MHC- IIX, MHC-Fetal, MHC-L y MHC-IIB. En conclusión, los músculos intrínsecos de la laringe presentan una mezcla de fibras y de isoformas de MHC lentas y rápidas, la que obedece a adaptaciones y cambios evolutivos que han permitido, por ejemplo, las características fonatorias que presenta la voz del ser humano.
Human skeletal muscle is composed of three major fiber types, referred to as type 1, 2A, and 2X fibers. This heterogeneous cellular composition complicates the interpretation of studies based on ...whole skeletal muscle lysate. A single-fiber proteomics approach is required to obtain a fiber-type resolved quantitative information on skeletal muscle pathophysiology.
Single fibers were dissected from vastus lateralis muscle biopsies of young adult males and processed for mass spectrometry-based single-fiber proteomics. We provide and analyze a resource dataset based on relatively pure fibers, containing at least 80% of either MYH7 (marker of slow type 1 fibers), MYH2 (marker of fast 2A fibers), or MYH1 (marker of fast 2X fibers).
In a dataset of more than 3800 proteins detected by single-fiber proteomics, we selected 404 proteins showing a statistically significant difference among fiber types. We identified numerous type 1 or 2X fiber type-specific protein markers, defined as proteins present at 3-fold or higher levels in these compared to other fiber types. In contrast, we could detect only two 2A-specific protein markers in addition to MYH2. We observed three other major patterns: proteins showing a differential distribution according to the sequence 1 > 2A > 2X or 2X > 2A > 1 and type 2-specific proteins expressed in 2A and 2X fibers at levels 3 times greater than in type 1 fibers. In addition to precisely quantifying known fiber type-specific protein patterns, our study revealed several novel features of fiber type specificity, including the selective enrichment of components of the dystrophin and integrin complexes, as well as microtubular proteins, in type 2X fibers. The fiber type-specific distribution of some selected proteins revealed by proteomics was validated by immunofluorescence analyses with specific antibodies.
We here show that numerous muscle proteins, including proteins whose function is unknown, are selectively enriched in specific fiber types, pointing to potential implications in muscle pathophysiology. This reinforces the notion that single-fiber proteomics, together with recently developed approaches to single-cell proteomics, will be instrumental to explore and quantify muscle cell heterogeneity.
The surgical redirection of efferent neural input to a denervated muscle via a nerve transfer can reestablish neuromuscular control after nerve injuries. The role of autonomic nerve fibers during the ...process of muscular reinnervation remains largely unknown. Here, we investigated the neurobiological mechanisms behind the spontaneous functional recovery of denervated facial muscles in male rodents. Recovered facial muscles demonstrated an abundance of cholinergic axonal endings establishing functional neuromuscular junctions. The parasympathetic source of the neuronal input was confirmed to be in the pterygopalatine ganglion. Furthermore, the autonomically reinnervated facial muscles underwent a muscle fiber change to a purely intermediate muscle fiber population myosin heavy chain type IIa. Finally, electrophysiological tests revealed that the postganglionic parasympathetic fibers travel to the facial muscles via the sensory infraorbital nerve. Our findings demonstrated expanded neuromuscular plasticity of denervated striated muscles enabling functional recovery via alien autonomic fibers. These findings may further explain the underlying mechanisms of sensory protection implemented to prevent atrophy of a denervated muscle.
Nerve injuries represent significant morbidity and disability for patients. Rewiring motor nerve fibers to other target muscles has shown to be a successful approach in the restoration of motor function. This demonstrates the remarkable capacity of the CNS to adapt to the needs of the neuromuscular system. Yet, the capability of skeletal muscles being reinnervated by nonmotor axons remains largely unknown. Here, we show that under deprivation of original efferent input, the neuromuscular system can undergo functional and morphologic remodeling via autonomic nerve fibers. This may explain neurobiological mechanisms of the sensory protection phenomenon, which is because of parasympathetic reinnervation.
PDF
