The explanation lies in the genes. Scientists at the Department of Clinical Sciences at Lund University in Malmo, Sweden , have identified a gene that exists in a special variant in most overweight people, a variant that makes fatty acids leak into the blood stream, where they don ™t belong.

Fat is constantly being metabolized by the body­-being produced, broken down, and rebuilt. Adiponutrin is a protein that takes part in this process. But overweight people often have a variant of the adiponutrin gene that causes the amounts of this protein to be lower than normal.

Adiponutrin is supposed to constitute a kind of corset ™ that keeps fat in its place in fatty tissue. If the protein doesn ™t do its job after a sugar-rich meal, fatty acids leak into the blood instead. The high content of fat in the blood then affects the cardiovascular system, the liver, muscles, and pancreas, explains Associate Professor Martin Ridderstrale.

The difference between obese people who are healthy and those who develop diabetes and cardiovascular disorders may be the result of their having different variants of the adiponutrin gene and some other genes, he believes. The research team in Malmo is therefore busy developing a map of genes that can show what variants of key genes function as protection and as risk factors, respectively, in connection with these diseases.

In the future this kind of mapping of an obese patient may be of significance in treatment. Certain medications, for example, might be more appropriate for people with certain gene variants. This opens the possibility of tailoring treatment to each individual, says Martin Ridderstrale.

The research team ™s findings on the adiponutrin gene are described in an article in the latest issue of the internationally recognized journal Diabetes.

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"Sequencing is expensive, so the shorter the section you can sequence and still get useful information, the better," van der Lelie said. "In fact, because these tags are so short, we 'glue' 10 to 30 of them together to sequence all at one time, making this a highly efficient, cost-effective technique."

For tag sequences that can't be matched to an already sequenced bacterial genome (of which there are only a couple hundred), the scientists can use the tag as a primer to sequence the entire attached ribosomal gene. This gene is about 1400 genetic-code-letters long, so this is a more time-consuming and expensive task. But since ribosomal genes have been sequenced and cataloged from more than 100,000 bacterial species, this "ribotyping" technique makes use of a vast database for comparison.

"If there's still no match," said van der Lelie, "then the tag probably identifies a brand new species, which is also very interesting!"

In another test with possible applications for identifying agents used in bioterror attacks, the technique also clearly discriminated between closely related strains of Bacillus cereus, a pathogenic soil microbe, and Bacillus anthracis, the bacterial cause of anthrax.

This technique could also help assess how microbial community composition responds to changes in the environment. Such information might help identify which combinations of species would be best suited to, say, sequestering carbon or cleaning up radiological contamination.

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