When young, healthy men who exercise regularly consume leucine, the molecular signals that promote muscle growth are stronger near the outer edges of their muscle fibers than near the center,...
Mechanism
Synthesis from 1 study
Leucine tells muscle cells to move their protein-building machinery to the outer edge, where it works more effectively. This is why the outside of the muscle fiber builds more protein than the inside after eating leucine.
Most probable mechanism
When leucine is consumed, it enters muscle cells and activates a molecular switch that moves a key protein complex to the outer edge of the muscle fiber. There, this complex turns on another protein that helps build muscle proteins, and this activation happens much more strongly at the edge than in the center, leading to more efficient muscle growth where it's needed most.
Leucine is absorbed from the bloodstream into skeletal muscle cells and binds to intracellular sensors that regulate nutrient signaling.
This binding releases inhibition on a regulatory complex that controls the positioning of mTORC1, enabling its recruitment to lysosomal and plasma membrane surfaces.
mTORC1 translocates specifically to the peripheral region of the muscle fiber, near the cell membrane and lysosomes, where upstream activators and downstream substrates are concentrated.
At the periphery, mTORC1 becomes fully activated and phosphorylates RPS6 at Ser240/244, enhancing the efficiency of ribosomal translation initiation.
Phosphorylated RPS6 increases the rate of myofibrillar protein synthesis, with the highest activity occurring in the peripheral region of the muscle fiber.
Evidence from Studies
Supporting (1)
Community contributions welcome
Leucine ingestion promotes mTOR translocation to the periphery and enhances total and peripheral RPS6 phosphorylation in human skeletal muscle
Contradicting (0)
Community contributions welcome
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.