The core mechanism: AICAR and AMPK

How a mitochondrial peptide flips the cell’s energy switch

The dominant model for MOTS-c is metabolic. Rather than docking onto one receptor, MOTS-c is proposed to nudge one-carbon metabolism (the folate and purine pathways), causing the intermediate AICAR to build up. AICAR is a natural activator of AMPK, the cell’s master low-energy sensor, so MOTS-c ends up switching AMPK on indirectly.

Once AMPK is active, the textbook expectation is a shift from storing to burning: more glucose uptake and a brake on expensive building work. Be careful about what was actually measured for MOTS-c itself, though. In the one transgenic-mouse study that looked, the peptide improved intrinsic mitochondrial efficiency with no change in mitochondrial protein content, and the fuel measurements do not agree with each other: in high-fat-diet mice the respiratory exchange ratio went up, a shift toward carbohydrate, while in late-life treated old mice the same measurement showed increased fat utilization alongside a significant reduction in fat mass. This unit walks the chain step by step and stays honest about a key nuance: the link is metabolic rewiring upstream of AMPK, not a direct handshake, and almost all of it is mouse and cell data.