Fibronectin type III domain-containing protein 5 (FNDC5)-like immunoreactivity and mRNA abundance in domestic animal tissues.
Authors: Lai E, Sands J, Unniappan S
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Irisin—a peptide hormone released from muscle tissue during exercise—has demonstrated promising effects on bone health, cardiac function, and neuroprotection in research models, yet remains poorly characterised in domestic animals. Lai and colleagues investigated whether the irisin precursor protein (FNDC5) and processed irisin are present in equine, porcine, and anatine tissues by conducting RT-PCR analysis of skeletal muscle, immunohistochemistry on stomach samples, and multispecies ELISA on serum from all three species. The team confirmed FNDC5 mRNA and the ~25 kDa FNDC5 protein in pig and duck muscle, identified FNDC5/irisin-like immunoreactivity in pig stomach and serum from all three species (with horses showing 15.4 ng/mL average irisin-like immunoreactivity), though notably failed to detect processed, cleaved irisin in any tissue tested. The findings suggest that whilst the molecular machinery for irisin production exists across domestic species, methodological challenges—and possibly genuine biological differences—currently prevent reliable detection of the active hormone, highlighting the need for standardised assay development before irisin can be practically evaluated as a biomarker for exercise response or muscle adaptation in equine and other veterinary medicine contexts.
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Practical Takeaways
- •Irisin precursor (FNDC5) is present in domestic animal tissues including horses, but processing to mature irisin may differ from humans; current detection methods may be unreliable for equine applications
- •Further validated assays are needed before irisin can be meaningfully measured or its effects studied in equine athletes or rehabilitation contexts
- •Exercise-related benefits in horses cannot yet be attributed to irisin metabolism based on current evidence
Key Findings
- •FNDC5 mRNA was identified in skeletal muscle samples from pigs and ducks using RT-PCR analysis
- •An approximately 25 kDa band representing FNDC5 protein was detected in both pig and duck skeletal muscle tissue
- •FNDC5/irisin-like immunoreactivity was detected in serum samples from horses (15.4 ng/mL), pigs (7.0 ng/mL), and ducks (13.7 ng/mL) using multispecies ELISA
- •Processed irisin was not detectable in any domestic animal tissue samples examined, despite presence of FNDC5 precursor