Your Bones Affect Your Appetite-And Your Metabolism

Source: University of Montreal

Summary: A new study has found that our skeleton not only acts as supporting structure for the muscles and tissues but also affects our appetite and metabolism.

Human skeleton serves as an internal structural framework which not only supports the body for attachment of muscles and tissues but also produces a hormone called Osteocalcin (a protein hormone found in bone and dentin). It is well known that hormones can affect bones – think about women are more prone to osteoporosis when they reach menopause, this happens because their estrogen levels drop. But bone itself affecting other tissues took its root only a few years ago after the discovery of osteocalcin. The recent study done by Mathieu Ferron and his team at the Montreal Clinical Research Institute (IRCM) unveiled a puzzle which explains how osteocalcin works. The findings of the study were published in the Journal of Clinical Investigation.

Absence of furin affects appetite

Immunofluorescence analyses of primary osteoblasts transfected with FLAG–pro-OCN or the R46A/R48A/R49A FLAG–pro-OCN mutant (FLAG–pro-OCNAAA) expressed from the p3xFLAG-Myc-CMV-23 vector. Furin is shown in green, FLAG (i.e., pro-OCN) in red, and DNA (DAPI) in blue. Credit: University of Montreal

Osteocalcin is produced by osteoblasts and it builds up in bone and through a chain of chemical reactions, is released into the blood. One of the functions of osteocalcin is to decrease blood glucose levels by increasing insulin production. It also increases energy expenditure and protect us from obesity. Osteocalcin is produced in an inactive form initially. What interested the researchers was how osteocalcin becomes active and play its role when released into the blood. IRCM lab described that an enzyme (acts like molecular scissors) is required to convert inactive osteocalcin to active osteocalcin. Ferron’s team were successful in identifying the enzyme and it is called furin which snips inactive osteocalcin to convert it into active osteocalcin.

Deleting the enzyme furin had an unexpected effect in mice – it reduced the mice’s appetite and the researchers were confident that absence of furin was the cause. This discovery someday may open a new door in preventing Type 2 diabetes and Obesity.

Prof. Mathieu Ferron said, “We demonstrated that when there was no furin in bone cells, inactive osteocalcin built up and was still released, but this led to an increase in blood glucose levels and a reduction in energy expenditure and insulin production”, “Our results suggest the existence of a new bone hormone that controls food intake” and further added “In future work, we hope to determine whether furin interacts with another protein involved in appetite regulation.”

More Information: Omar Al Rifai et al, “Proprotein convertase furin regulates osteocalcin and bone endocrine function”, Journal of Clinical Investigation (2017). DOI: 10.1172/JCI93437

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