Brain Plays Key Role In Regulating Bone Density

The results of this research, involving a study of theactivity of the protein interleukin 1 in the brain, comprise not only abreakthrough in understanding the regulation of bone density by thebrain but also hold promise for the development of future treatment forosteoporosis, say the researchers. An article about their work appearsin the current edition of the prestigious American journal, Proceedings of the National Academy of Sciences.

The Hebrew University research project is headed by Prof. ItaiBab of the Bone Laboratory, working in cooperation with Prof. RazYirmiya of the Department of Psychology, Prof. Esther Shahami of the ofthe Laboratory for the Study of Brain Trauma, Ph.D. students Alon Baginand Inbal Goshen and master's degree student Sharon Feldman.

Osteoporosis is the most widespread, degenerative disease inthe Western world. It is characterized by loss of bone density andconsequent structural weakening of the skeleton. Osteoporosis sufferersare highly susceptible to fractures, in some cases leading to severephysical disability and complications that can even end in death.

In humans and other vertebrates, one-tenth of the bone tissueis involved in an "exchange" process of continuous bone loss andgeneration. In adult humans and other mammals, this process isbalanced; that is, the amount of bone tissue that is generated is equalto that which is lost, thus preserving bone density. With age, thisbalance is disrupted, and the amount of bone tissue that is lost isgreater than that which is created, with the result that bone densitydeclines and bone structure is impaired.

The interleukin 1 protein has been known for many years as astimulator of the immune system. In the skeleton the protein causes anincrease in the number and activity of osteoclastic cells -- the cellswhich break down bone tissue and which develop from the same cells asthose of the immune system.

By experimenting with genetically engineered laboratory micewhose ability to react to interleukin 1 was controlled, the HebrewUniversity researchers were able to demonstrate that the properloss/generation balance in bone tissue is regulated by the level ofactivity of interleukin 1 in the brain. A normal, optimal level ofinterleukin 1 activity in the brain is required to protect bone densityby impeding bone tissue breakdown, say the scientists.

"The connection between the brain and the bone structure is a new areaof research about which very little is known," said Prof Bab. "Thesenew findings from our laboratories at the Hebrew University regardingthe action of interleukin 1 on the breakdown of bone tissue indicate acomplex neural system controlling bone structure and point the waytowards new revelations in the near future in this area."

The research was conducted within the framework of a projectdirected at clarifying the connection between the brain, behavior andchanges in skeletal structure. The research was funded by the Bikura[First] Program of the Israel Science Foundation, which supportspioneering, innovative, interdisciplinary initiatives.