Exercise activates irisin, a hormone that helps to burn fat and supports the production of cells that helps in bone formation.
Highlights
- Irisin hormone released during exercise and cold weather helps in fat burning.
- The hormone can directly increase the production of osteoblasts, -cells that synthesize bone.
- Recombinant irisin has also been shown to suppress sclerostin, a protein that is involved in bone loss .
Irisin has been linked to improved glucose tolerance and weight loss in obese, prediabetic mice. While most studies have focused on irisin produced by muscle tissue, some research has suggested that irisin increases bone mass in addition to its metabolic benefits. However, it was unknown whether irisin is secreted by bone upon exercise or whether it regulates bone metabolism.
About the Study
Chen and his colleagues tested a group of five-week-old mice, with two weeks of voluntary wheel running. Compared to a control group without access to a running wheel, mice that had exercised expressed six-fold higher FNDC5 and irisin expression in bone tissue.
Irisin expression was observed in several different bone regions, including the growth plate, trabecular bone, cortical bone, articular cartilage and muscle-bone interface.
The team evaluated the effects of recombinant irisin in bone cell lines, and found that irisin can directly increase the production of osteoblasts--cells that synthesize bone--and mineralization, while inhibiting the production of osteoclasts--cells that break down bone.
Irisin Helps Regulate Bone Metabolism
The team’s findings demonstrate that irisin produced by bone could have a role in bone metabolism through both direct mechanisms and indirect mechanisms, as the transition from white fat to brown fat has been shown to lead to increased bone formation by previous studies.
In addition, recombinant irisin has also been shown to suppress sclerostin, a protein that is involved in bone loss during prolonged lack of mechanical load, such as in bed-ridden patients.
"Exercise-induced irisin may not only act as an endocrine factor capable of promoting the browning of white adipose tissue, but could also regulate bone metabolism by autocrine mechanisms," said Chen, who also serves as faculty in the Cell, Molecular & Developmental Biology program at the Sackler School of Graduate Biomedical Sciences at Tufts.
"Our results suggest that irisin may have a therapeutic potential in strengthening bone in bone-loss-associated diseases, and additional studies are needed to evaluate the underlying mechanisms by which irisin functions."
Reference
- Jake Chen et al., Exercise-induced irisin in bone and systemic irisin administration reveal new regulatory mechanisms of bone metabolism, Bone research (2017) http://dx.doi.org/10.1038/boneres.2016.56.
Source-Medindia