Sarcopenia, the age-related loss of muscle mass and strength, has many possible contributing causes. There is fair evidence for most of them, from a failure to process amino acids needed for construction of new muscle mass to damaged neuromuscular junctions to loss of stem cell function. The most compelling evidence I’ve seem points to that stem cell dysfunction as the most significant contribution. It is certainly the case that stem cell populations decline in size and activity with age, reducing the supply of daughter cells needed to maintain tissues in good condition. Muscle stem cells are among the most studied in aging research.
The paper noted here picks through the major themes in sarcopenia, and makes the argument for linking at least some of them to age-related issues in mitochondrial function. The mitochondria are the power plants of the cell, and muscle is an energy-hungry tissue. Mitochondria can suffer forms of damage that make them harmful to their cells and the surrounding tissue; this is a significant issue in aging. More generally, all mitochondria change for the worse in old tissues, possibly in reaction to other
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