Physiological Role of a Novel Hormone FNDC5/irisin Revealed in Humans

New findings reported in journal Metabolism

Oxford, October 1, 2012 - A research team led by Dr. Christos Mantzoros, MD, PhD, at Beth Israel Deaconess Medical Center, Harvard Medical School, has published new findings elucidating the molecular and clinical role of FNDC5/irisin in humans.

Irisin is a recently identified hormone secreted from muscle cells that has been found to serve as a chemical messenger providing key exercise-induced health benefits in mice. In these earlier studies, irisin showed direct effects on ‘browning’ of white fat which would lead to burning of excess calories. Discovery of irisin therefore raised expectations of potential for developing new therapies for metabolic diseases.

In their study, Dr. Mantzoros and his team of researchers went one step further by uncovering the role of irisin in humans. They reported that whereas the cleaved soluble part of the FNDC5 molecule (irisin) is readily detectable in human plasma, the uncleaved and unprocessed molecule FNDC5 is only rarely detectable.

They studied possible predictors of circulating irisin concentrations by performing cross-sectional and interventional studies in humans. They found that irisin levels reflect muscle mass primarily and are higher in younger male athletes than in older women. Also, muscle mRNA expression of FNDC5 was strongly and positively correlated with PGC1-α mRNA levels which confirms irisin as a myokine, a hormone secreted by muscle.

The Mantzoros group addressed the controversy of whether irisin levels change in humans during exercise by comparing levels in young healthy males who performed acute sprint runs and chronic sprint training for eight weeks. The results showed that irisin levels increase in response to acute exercise and irisin levels are closely and negatively associated with muscle ATP levels, pointing to a need for a prompt secretion of irisin after acute exercise to meet the needs for ATP and metabolite synthesis in muscle. Also reported were associations of irisin with growth factors, which increase muscle mass and metabolic outcomes in normal humans; a finding which will require confirmation by future studies.

Although this clinical study has revealed a significant amount of novel information regarding the physiological role of irisin in humans, much remains unknown regarding its function as a hormone and the regulation of FNDC5 synthesis and irisin secretion.

This article is “FNDC5 and irisin in humans: I. Predictors of circulating concentrations in serum and plasma and II. mRNA expression and circulating concentrations in response to weight loss and exercise” by Huh JY, Panagiotou G, Mougiosb V, et al. (DOI10.1016/j.metabol.2012.09.002). The article will appear in Metabolism, Volume 61, Issue 12 (December, 2012), published by Elsevier.
 

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Notes for editors
Full text of the article is available upon request; contact Andrew Miller at +44 1865 843823 or andrew.miller@elsevier.com. Journalists wishing to interview the authors may contact Christos S Mantzoros, MD, PhD, Beth Israel Deaconess Medical Center, Boston at +1 617 667 8630.

About Metabolism–Clinical and Experimental
Metabolism promotes excellence in research by publishing high-quality original research papers, fast-tracking cutting-edge papers, research brief reports, mini-reviews, and other special articles related to all aspects of human metabolism. Work considered for publication in Metabolism includes studies in humans, animal and cellular models. Work with strong translational potential is prioritized. Metabolism will consider papers for publication in any aspect of translational and clinical metabolic research, including (but not limited to): Energy Expenditure and Obesity; Metabolic Syndrome and Diabetes; Nutrition, Exercise, and the Environment; Genetics, Proteomics, and Metabolomics; Carbohydrate, Lipid, and Protein Metabolism; Endocrinology and Hypertension ;Mineral and Bone Metabolism; Cardiovascular Diseases and Malignancies.  www.metabolismjournal.com 

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About Elsevier

Elsevier is a world-leading provider of information solutions that enhance the performance of science, health, and technology professionals, empowering them to make better decisions, deliver better care, and sometimes make groundbreaking discoveries that advance the boundaries of knowledge and human progress. Elsevier provides web-based, digital solutions — among them ScienceDirect, Scopus, Elsevier Research Intelligence, and ClinicalKey — and publishes nearly 2,200 journals, including The Lancet and Cell, and over 25,000 book titles, including a number of iconic reference works.

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andrew.miller@elsevier.com