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Ottawa researcher links diet, childhood diabetes: Wheat protein pinpointed in pioneering study
By Tom Spears
For years the medical textbooks all agreed on one thing: Type 1 diabetes, the kind that strikes in childhood, is not caused by a person's diet.
This didn't make life easier for Fraser Scott, an Ottawa medical researcher looking for things in our diet that do cause the disease. How do you ask for funding to investigate a connection that doesn't exist?
This makes his team's discovery a little sweeter. They have just published findings in the Journal of Biological Chemistry that show a protein in wheat appears to cause some children's immune systems to attack the wrong target, damaging their body's own cells and causing diabetes.
Dr. Scott first got the idea when he worked at Health Canada in the early 1980s. He was experimenting with a strain of lab mice bred to develop diabetes easily. But when he put the mice on a restricted diet, he noticed something odd: Mouse after mouse stayed healthy, showing no signs of diabetes.
At first he suspected someone had sold him a batch of dud mice. But he tried again with more mice and got the same result.
Maybe diet is important after all, he concluded. Wheat seemed a possible candidate: Children with Type 1 diabetes (once called juvenile diabetes) often have celiac disease, an inability to digest wheat. He decided to have a closer look at wheat.
Dr. Scott, Amanda MacFarlane and Karolina Burghardt at the Ottawa Hospital Research Institute and colleagues at the University of Ottawa and in Finland have isolated one protein in wheat that appears to cause the trouble. They scanned through one million candidate proteins from wheat, narrowing the field first to three that caused reactions in the immune system, and finally to one that is linked to damage in the islets. These are cells in the pancreas that produce insulin, which breaks down sugar. Diabetes occurs when the pancreas loses the ability to produce insulin.
"To put it in the simplest terms, some individuals have an abnormal immune system," he says. A proper immune system should attack germs in our food, but not the proteins, of which we eat untold thousands every day.
But when the immune system goes off course and starts attacking the proteins in wheat, he suspects that it keeps going on its destructive course and starts attacking the insulin-producing cells in the pancreas as well. Somehow, he believes, wheat has mobilized these disease-fighting cells into full-scale attack mode -- but against the wrong target.
These destructive cells in the immune system "are just sitting there until something stimulates them," Dr. Scott says. "Then they expand, migrate to the pancreas, and cause a long period of inflammation that ultimately kills the beta cell," the cell that makes insulin. Other infections may also play a role, possibly making this immune attack worse.
In his lab, one wheat protein called Glb-1 caused blood from people and rats with diabetes to "light up" in an immune reaction. That appears to clinch the link with diabetes.
If his findings hold up, this will be the first protein in food shown to cause at least some diabetes. (The disease also has genetic causes but isn't purely genetic: If one identical twin has it, chances are only about 30 per cent that the other twin will have it, despite have the all same genes.)
The team hasn't made the type of discovery that will create new drugs. But they do see some uses for the findings.
It's possible, they believe, that exposing babies to the wheat protein at an early age, when the immune system is still learning what's an enemy, can "teach" the immune system not to react to wheat later in life. Another possibility is that people with family histories of diabetes may want to avoid wheat, "but that's a really grim diet," Dr. Scott says.
His co-author Illimar Altosaar, who teaches food biochemistry in the medical school at the University of Ottawa, has started making "knockout" varieties of the wheat they used, removing just the one protein linked to diabetes. He wants to see whether rats fed the knockout variety will still develop diabetes.
Wheat blends thousands of proteins, he said, "to make all the magical things we know in baking: the dough, the aroma, the mystique of bread, the baguette in a bicycle pannier. It's a very, very complex matrix." Looking for wheat varieties that don't have the problem protein "is the first thing we have to do," he added. Food scientists may also decide to engineer or breed a wheat variety without that protein.
(Reprinted with permission from The Ottawa Citizen)