Osteoporosis, obesity genes reported found

Discoveries could lead to tests, drugs for earlier treatment, researchers say

November 04, 2003|By Peter Gorner | Peter Gorner,CHICAGO TRIBUNE

CHICAGO - Researchers in Iceland and France say they have discovered genes that play key roles in the development of the bone-loss disorder osteoporosis and extreme obesity, common diseases that affect millions of people.

Emphasizing that the genes are not the whole story and that other genes, plus environmental and lifestyle factors will prove important, the discoveries nonetheless could lead to new drugs and screening tests to inform people of their susceptibility years - perhaps even decades - before trouble develops, the scientists said.

The gene responsible for bone loss was found by a leading commercial gene discovery company, Decode Genetics based in Reykjavik.

Using blood samples from more than 1,000 volunteers and Decode's nationwide genealogical database of Icelanders stretching back to the Vikings 1,100 years ago, a team led by Unnur Styrkarsdottir screened hundreds of families for genes shared by family members afflicted by low bone mineral density and osteoporotic fractures.

More than a million such fractures - primarily of the hip and spine - occur each year in the United States with a direct medical cost exceeding $10 billion.

The researchers isolated on the short arm of the 20th Chromosome a DNA sequence known as the Bone Morphogenetic Protein 2, or BMP2, gene.

Particular versions of the gene can triple a woman's risk of developing osteoporosis.

"This gene makes a growth factor that stimulates the formation of bone," said Dr. Kari Stefansson, the founder and chief executive officer of Decode Genetics. "When there's something wrong with it, the peak bone mass you develop before menopause is limited. We could do the test in young women, and they might be influenced to change their lifestyles."

The new discovery is exciting, said osteoporosis researcher Dr. Craig B. Langman, head of kidney diseases at Northwestern University Medical School and Children's Memorial Hospital.

"The science seems very solid and narrows down the possibility of identifying women who might benefit from early intervention of diet and lifestyle," Langman said.

To check results, the Icelandic researchers went outside their country. They studied postmenopausal Danish women - one group with low mineral bone density and the other with osteoporotic fractures. Variations in the BMP2 gene were verified as major risk factors.

The gene associated with obesity was discovered by researchers from the Institut Pasteur de Lille in France who used genome-wide scans of a region on the 10th chromosome linked to susceptibility for obesity.

They pinpointed a gene, GAD2, that has a role in stimulating the appetite. One form of the gene is strongly linked to obese people, making it one of the first to be promoted as a candidate for "the obesity gene."

Both studies were published yesterday in PLoS Biology, a new science journal that is available for free on the Internet.

The Chicago Tribune is a Tribune Publishing newspaper.

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