A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis.
Level 5 - mechanism / opinion, no new human data
Preclinical laboratory study using cell cultures, mouse models, and descriptive human samples
PubMed 22237023 · doi:10.1038/nature10777
What was done
Researchers investigated how muscle expression of the transcriptional co-activator PGC1-α drives metabolic adaptations. They examined the cleavage and secretion of the membrane protein FNDC5 into a novel hormone named irisin, evaluated its effects on white adipocytes in culture and in vivo in mice, measured irisin induction following exercise in mice and humans, and assessed the metabolic consequences of elevated circulating irisin in mice.
What was found
The abstract reports no numerical values, effect sizes, or participant numbers. Qualitatively, muscle PGC1-α expression stimulated FNDC5 expression and secretion of irisin. Irisin stimulated UCP1 expression and a brown-fat-like gene program in white adipose cells both in culture and in vivo. Exercise induced irisin in mice and humans. Mildly elevated circulating irisin in mice increased energy expenditure without altering food intake or movement, which improved obesity and glucose homeostasis.
Why it matters
This study identifies irisin as an exercise-induced myokine that drives adipose tissue browning and thermogenesis, proposing a novel endocrine link between muscle activity and systemic metabolic regulation.
Limits
The abstract provides no sample sizes, quantitative effect sizes, variance estimates, or p-values. Most functional findings are derived from cell cultures and rodent models, limiting direct translation to human physiology. Exercise protocols and human participant characteristics are not described.
Cited by
- supports Irisin stimulates the conversion of white adipose tissue to brown adipose tissue by promoting mitochondrial biogenesis.