Messengers are chains that carry a signal

Messengers covers peptides that carry signals between the gut, brain, skin and immune cells. A few of these signals are mapped in detail and underpin approved drugs. Many others are research names whose evidence comes from cells, rodents or a small number of human studies, and the articles read each one residue by residue before weighing the claims made for it.

Start with how a gut peptide tells your brain you are full and oxytocin and the trouble with nicknames. For research compounds, semax vs selank compares two nasal peptides from the same tradition, MOTS-c, hidden in mitochondrial DNA shows what a mouse result can and cannot say, and follistatin explains why a 344-residue protein is not a short peptide at all.