Causes of Type 1 Diabetes

Oxygen Free Radicals
Oxygen free radicals, formed as a by-product of many chemical reactions in the body,  wreak havoc wherever they go.

Normally, the body has ways of quenching free radicals. But smoke, air pollution, diet, and even genetics can contribute to the formation of excessive amounts of free radicals, which the body cannot always handle. Uncontrolled, the reactive molecules can destroy the body’s own cells as well as bacteria.

Oxygen free radicals contribute significantly to the aging process and to the development of several other diseases.

Researchers have implicated free radicals in the development of amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, a degenerative neuromuscular disease.

Some researchers believe that oxygen free radicals may also contribute to type 1 diabetes. Islet cells have very low levels of the enzymes that break down free radicals. Thus, agents that increase free radical production could result in destruction of pancreatic cells. If this is true, then researchers may be able to develop drugs that block the formation of free radicals in the islet cells.

Chemicals and Drugs
Several chemicals have been shown to trigger diabetes.
Pyriminil (Vacor), a poison used to kill rats, can trigger type 1 diabetes. Two prescription drugs, pentamidine, used to treat pneumonia, and L-asparaginase, an anticancer drug, can also cause type 1 diabetes. Other chemicals have been shown to cause diabetes in animals, but scientists don’t know for sure whether they have the same effect in humans.

In summary, it is unlikely that either genetics or environmental factors alone cause diabetes. But it does appear that a person could start with a genetic susceptibility-the inheritance of a particular set of genes. If this person is then exposed to some environmental “triggering” factor, such as a virus or a chemical, then diabetes may develop. Although no one is destined to develop diabetes with certainty, a person’s heredity may increase the odds.

Prevention of Type 1 Diabetes
By testing relatives of people with type 1 diabetes for autoantibodies, researchers can often predict who is likely to develop the disease. This could be especially useful as new therapies emerge, because they can be started before damage to the pancreas is too extensive. For example, it was thought that by identifying people who are likely to develop type 1 diabetes at an early stage, researchers might be able to treat them with insulin or drugs that suppress the immune system (anti-rejection medications) and thus prevent the T cells from destroying the beta cells in the pancreas. Recent studies do not support that this is possible at this time.

Some people with a high risk of getting type 1 diabetes have participated in studies to see whether immunosuppressants such as azathioprine or cyclosporine delay or prevent the onset of the disease.  These studies suggest that azathioprine or cyclosporine can reduce the dose of insulin needed in people who have already developed type 1 diabetes,  if the drug is started at the time the disease is diagnosed. Researchers have also been studying whether insulin can prevent type 1 diabetes.

In the Diabetes Prevention Trial (DPT), researchers found that giving insulin by injection or orally does not prevent type 1 diabetes in people at high risk.

Other therapies may also be tested as researchers learn more about the causes of type 1 diabetes. For example, if autoimmunity to GAD turns out to be a primary trigger of type 1 diabetes, it might be possible to develop a vaccine that would protect people from developing the disease.

Martha M. Funnell, MS, RN, CDE
Michigan Diabetes Research and Training Center
University of Michigan Medical School
Ann Arbor, Michigan

Robert M. Anderson, EdD
Michigan Diabetes Research and Training Center
University of Michigan Medical School
Ann Arbor, Michigan

Shereen Arent, JD
National Director of Legal Advocacy
American Diabetes Association

American Diabetes Association Complete Guide to Diabetes


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