How meals become bones

Amylin, a hormone produced along with insulin after food intake, is vital for strengthening bones, according to an article in the Journal of Cell Biology (www.jcb.org) by Gerard Karsenty and colleagues (Baylor College of Medicine, Houston, TX). A lack of amylin production in type I (autoimmune) diabetics may explain the prominent bone loss in these individuals - a problem that amylin replacement therapy may alleviate.

When food is short, strengthening bone may not be the body's top priority. But when the food arrives it is time to build up bone mass. Thus the body churns out amylin, which reduces the number of cells normally devoted to chewing up bone. These cells exist because bones stay strong only through a constant recycling in which cells chew away the old bone and deposit the new. Karsenty shows that the so-called osteoclast cells that do the chewing up can get the upper hand unless amylin is around to reduce their numbers.

Type I diabetics are deficient in amylin because their immune system attacks their own pancreatic cells that make both insulin and amylin. Injection of amylin, or treatment with a drug that turns on the amylin pathway, might help correct the bone loss and osteoporosis seen in these diabetics.

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