By Patricia Reaney 5/12/05
Two teams of scientists identified the hormone insulin on Wednesday as the trigger that causes the more severe form of diabetes.
Researchers have been mystified about what makes the body’s immune system turn against itself to attack cells in the pancreas that produce insulin, the hormone that regulates blood sugar levels.
Now they believe insulin itself is the key.
People with Type 1 diabetes, which accounts for 10-25 percent of cases, do not produce any insulin which helps glucose, or sugar, from food get into cells.
Type 2 diabetes, the more common form of the disease, is caused by an inability to make enough, or to properly use insulin. About 90 percent of sufferers have type 2 diabetes, which is linked to being overweight or obese.
“We are excited to be part of a growing body of evidence that points to insulin as the trigger for type 1 diabetes,” said David Hafler of Harvard Medical School in Boston, Massachusetts who headed one of the teams.
George Eisenbarth and scientists at the University of Colorado Health Sciences Center in Denver came to the same conclusion after studying mice.
Both research reports are published in the science journal Nature.
“If (the results) are reproduced and if it is true, then we have a way of stopping type 1 diabetes by turning off the immune response to insulin,” Hafler said in an interview.
BIG PIECE OF THE PUZZLE
Diabetes already affects 194 million people worldwide and the number could rise to 333 million by 2025.
Hafler and his team identified insulin as the culprit by isolating and cloning immune cells from people with type 1 diabetes and healthy controls and testing them in the laboratory.
They discovered that the cells from the diabetics reacted to insulin but cells from the healthy controls didn’t.
Eisenbarth and his team took a different approach but came up with the same answer.
They genetically engineered mice so they lacked normal insulin but still had a form of the insulin hormone that is not recognized by immune system cells. None of the mice with the modified insulin developed type 1 diabetes.
Hafler believes that if insulin is the driving force behind the disease, the next step is to test the hormone to see if it can be manipulated to prevent the disease.
“If we and others can confirm this (the results), it will be the best in vitro evidence possible that insulin is the antigen,” said Hafler.
An antigen is a compound which causes the body to form antibodies.
Sufferers of type 1 diabetes need daily injections of insulin. Patients with the milder type 2 can be treated with diet, exercise or drugs to stimulate the secretion of insulin.
Diabetes is the fourth main cause of death in most developed countries, according to the International Diabetes Federation. It also raises the risk of heart disease, stroke, blindness, kidney damage and nerve disorders that can lead to foot ulceration and amputations.
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