Islet-cell Transplants: The End of Insulin Shots?
Islet-cell transplants could offer millions of people with diabetes the chance for life without daily insulin injections.
Listen carefully and you might hear the faint whisper of the word "cure" echoing through the minds of people with diabetes. That's because promising results from a small study at the University of Alberta in Edmonton, Canada, have sparked international interest.
Physicians at the University of Alberta have transplanted insulin-producing islet cells from donated pancreases into patients with severe, unstable diabetes. The recipients have maintained normal blood sugar levels without taking insulin shots.
"The patients who have had the transplant are cured of diabetes, but they do have to take antirejection drugs," says James Shapiro, MD, director of the university's Clinical Islet Transplant Program. "But," he cautions, "there are still a number of challenging steps forward before we're ready to take this treatment to the 130 million people around the world with diabetes."
Conquering the Incurable
Considered incurable, diabetes mellitus causes high blood sugar levels due to the body's inability to produce or effectively use insulin, a hormone secreted by the pancreas that aids in storing or converting glucose from food into energy. Almost 16 million Americans have this disease, and about five million of them don't even realize they have it.
People with type 1 diabetes produce little or no insulin and require multiple daily injections of the hormone. People with type 2 diabetes either don't produce enough insulin or their bodies have difficulty putting the available insulin to work; about 40% of them require insulin injections. Age, obesity , and sedentary lifestyles contribute to type 2 diabetes.
Diabetes is the leading cause of blindness, end-stage kidney failure , and leg amputations, and it also increases the risk for heart disease , which is the number one killer of men and women in America. Until now, people with type 1 diabetes had no choice but to inject themselves with insulin throughout the day, measure their blood sugar levels, watch their diet, and plan structured meals and activities.
The Edmonton Protocol includes transplanting cells immediately after removal from the donated pancreas, removing foreign proteins from the cells, and adding islets from a second pancreas if blood sugars start to rise. Doctors infuse the cells into the patient's liver during a simple procedure, and the process carries less risk than an organ transplant.
Though this technique is revolutionary in the treatment of diabetes, only some 10% of study patients remained insulin-free after five years. However, the transplanted cells did allow many of the patients to avoid life-threatening blood-sugar crashes.
Potential Side Effects
The antirejection medications, however, suppress the immune system and increase the patient's chances of developing cancer and infections.
The National Institutes of Health and the Juvenile Diabetes Research Foundation International, with the sponsorship of the Immune Tolerance Network, are funding additional trials at 10 research centers in hopes of duplicating the Canadian results.
Lack of donated pancreases will limit the number of people who can receive islet-cell transplants. With limited available organs, other scientists search for new sources of islet cells. Some researchers are cultivating human islet cells in the laboratory, while others are developing cell lines that produce insulin. Until these or other new methods prove to be expedient, safe and effective, transplants will rely on donated organs.
American Diabetes Association
Immune Tolerance Network
Juvenile Diabetes Foundation
National Institute of Diabetes and Digestive and Kidney Diseases
Organ and Tissue Donation Initiative
Shapiro AMJ, Ricordi C, Hering BJ, et al. International Trial of the Edmonton Protocol for Islet Transplantation. NEJM. 2006;355:1318-1330.
Bromberg JS, LeRoith, D. Diabetes cure—is the glass half full? NEJM. 2006;355:1372-1374.
Last reviewed February 2007 by Jill D. Landis, MD
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