In an elderly patient experiencing significant muscle loss (sarcopenia) despite adequate caloric intake, what distinguishes the underlying metabolic mechanism from simple protein malnutrition?

💡 Explanation

Sarcopenia involves resistance to anabolic signals, such as those from amino acids. Impaired mTORC1 pathway activation diminishes the muscle's ability to respond to these signals, because the protein synthesis is not effectively stimulated, therefore muscle protein synthesis decreases rather than simply being limited by substrate availability as in simple protein malnutrition.

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