Where it comes from
- Made in
- Skeletal muscle, after exercise; also fat tissue
- Sent out by
- Exercise, through the regulator PGC-1alpha; shivering
- Acts on
- White fat (browning)
- Bone (osteocytes and osteoblasts)
- Brain (BDNF in the hippocampus)
What it does
- Turns white fat cells toward heat-making brown fat in mice 1
- Reported to protect bone and to carry some of exercise’s benefit to the brain
- In people, levels are low and the human gene starts with an unusual codon, which fed a dispute over whether it exists at all 2; mass spectrometry found it at about 4 ng/mL in 2015 3
In medicine
- No medicine copies it or blocks it, and no measurement of it guides any decision
- The commercial antibody kits were shown to pick up unrelated proteins, so published human levels differ by orders of magnitude between studies and cannot be compared with each other 2
Beyond the body’s own use
- In mice, restoring it reversed memory loss in models of Alzheimer’s disease and blocking it removed the benefit of exercise; that is the strongest claim made for it and it is entirely animal work 4
- It protects bone and improves glucose handling in mice too. No trial has given irisin to a person, and the browning of fat that made its name was shown in mice, not in people 1
- Supplements and devices said to raise it have nothing behind them in humans, and the honest state of the field is that the assays have to be fixed before the claims can be tested 23
Sources
- Boström et al., A PGC1-alpha-dependent myokine that browns white fat, Nature 2012
- Albrecht et al., Irisin, a myth rather than an exercise-inducible myokine, Scientific Reports 2015
- Jedrychowski et al., Detection and quantitation of circulating human irisin, Cell Metabolism 2015
- Lourenco et al., Exercise-linked FNDC5/irisin rescues memory in Alzheimer’s models, Nature Medicine 2019
This card describes what a medicine is for and what the evidence says; it recommends nothing. Talk to your clinician about anything you read here.