Figure 2. Regulation of skeletal muscle protein synthesis by essential amino acids.

This simplified schematic illustrates some of the key known and hypothesized pathways of mTORC1 regulation by leucine and insulin discussed in this review. Although the exact mechanisms behind the age related anabolic resistance to leucine induced skeletal muscle protein synthesis remain unclear, insulin resistance, endothelial dysfunction, and oxidative stress are thought to be among the potential contributors.