Four compounds, four completely different mechanisms, one shared question: what actually goes wrong inside a cell as it ages?
Grouping them under one heading is a convention rather than a claim that they work alike.
NAD+
Approaches the question through metabolism. NAD+ is consumed by the enzymes that repair DNA and regulate gene expression, which turns a cell’s supply of it into a shared budget rather than simply an energy currency.
Epitalon
Four amino acids, out of Soviet-era pineal research. The question behind it was whether the pineal gland’s peptide output relates to how the body tracks time.
SS-31
Targets the mitochondrial inner membrane directly, binding cardiolipin. A rare thing in a small peptide: a specific structural target inside a specific organelle.
MOTS-c
Encoded in mitochondrial DNA rather than the nucleus, which was a genuine surprise when it was found. It suggests the mitochondrion signals outward rather than only taking instructions.
What links them
Mitochondria, mostly. Three of the four touch mitochondrial function from completely different angles, which is less a coincidence than a reflection of where the ageing field currently has its attention.