skeletal muscle hypertrophy

Definition

Target type: biologicalprocess

The enlargement or overgrowth of all or part of an organ due to an increase in size (not length) of individual muscle fibers without cell division. In the case of skeletal muscle cells this happens due to the additional synthesis of sarcomeric proteins and assembly of myofibrils. [GOC:mtg_muscle]

Skeletal muscle hypertrophy is the increase in the size of existing muscle fibers. It is a complex process that involves a variety of signaling pathways and cellular events. The process begins with mechanical stress, such as resistance training, which triggers a cascade of molecular events in the muscle fiber. This includes the activation of mechanosensitive ion channels that depolarize the muscle fiber membrane. This depolarization activates a signaling cascade, including the activation of calcineurin, a calcium-dependent phosphatase. Calcineurin then activates the transcription factor NFATc, which triggers the expression of genes involved in muscle growth, such as myostatin and IGF-1. The increased production of these growth factors leads to the activation of the mTOR pathway, which is a key regulator of protein synthesis. mTOR activates downstream effectors, such as the ribosomal protein S6 kinase (S6K1) and the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). These effectors promote the translation of mRNA into proteins, leading to increased protein synthesis and muscle growth. In addition to increased protein synthesis, skeletal muscle hypertrophy also involves a decrease in protein degradation. The increased expression of growth factors and the activation of mTOR also suppress the activity of the ubiquitin-proteasome system, a major pathway for protein degradation in skeletal muscle. This leads to a net increase in muscle protein content and ultimately an increase in muscle size. The process of skeletal muscle hypertrophy is highly regulated and involves a complex interplay of signaling pathways and cellular events. The specific response to mechanical stress is influenced by factors such as age, sex, training history, and nutritional status.'
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Proteins (1)

Compounds (5)