Library · Disease
Muscle atrophy
Make it clearer
Muscle is not a fixed block. It is constantly building new proteins and breaking down old ones, and its size is the result of that balance. That equilibrium is called proteostasis. Muscle atrophy is simply the balance tipping: more is taken apart than is built, and the result is less mass and less strength.
The side that takes things apart has its own name and its own machinery: the ubiquitin-proteasome system. Ubiquitin is a tag that gets attached to a protein to mark it, and the proteasome is the shredder that destroys whatever is tagged. What regulates that breakdown in muscle are enzymes called ligases, and the expression of two of them, MuRF1 and atrogin-1, rises sharply in atrophy.
One observation points straight at them: mice that have one of those two ligases removed resist the atrophy that normally appears when the nerve to the muscle is cut.
There is a separate term for what age brings: sarcopenia, the loss of mass and the atrophy of aging. And even that one is not inevitable: it does not happen to everyone.
In brief
In muscle atrophy, proteostasis breaks down: degradation outpaces synthesis, and muscle mass and strength are lost.
A scale tipping toward the side that takes things apart.
Degradation is carried out by the proteasome on proteins tagged with ubiquitin, and in muscle it is regulated by MuRF1 and atrogin-1.
Their expression rises sharply in atrophy, and mice lacking one of those ligases resist denervation atrophy.
Sarcopenia is the name for the loss of mass and the atrophy of aging, and it is not universal.
Sources (2)
- The Journal of Physiological Sciences, PubMed CentralThe ubiquitin-proteasome system in regulation of the skeletal muscle homeostasis and atrophy: from basic science to disordersPublished
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Muscle, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated