Islet Cell Transplants Aid Type 1 Diabetics
FRIDAY May 16, 2008 -- Transplanted islet cells help people with type 1 diabetes live insulin-free for at least a year or two, and appear to provide longer-term improved metabolic control even after people have to begin using insulin again, researchers report.
Using continuous glucose monitoring systems, researchers from the University of Miami Miller School of Medicine found that diabetics who received islet cell transplants had fewer episodes of low blood sugar (hypoglycemia) and spent more time with normal blood sugar than did people with diabetes who hadn't undergone a transplant.
"Islet cell transplantation can be a good option. Patients can regain hypoglycemia unawareness and improve metabolic control," said the study's lead author, Dr. Lisa Gorn, a third-year endocrinology fellow at the medical school.
However, Gorn pointed out that because islet cell transplantation still requires lifelong immunosuppressant medications, the procedure is reserved for those with difficult to control diabetes and people who have severe, recurrent episodes of hypoglycemia. She said newer immune-suppressing medications are currently being tested in clinical trials, and the hope is that they'll have fewer side effects.
Islet cells -- also called beta cells -- are cells in the pancreas that produce insulin, a hormone necessary for the body to metabolize glucose, or blood sugar. In type 1 diabetes, the rarer form of the disease, antibodies in the body mistakenly attack the islet cells and destroy them. People with type 1 diabetes don't produce insulin on their own, and must take repeated insulin injections daily, or use an insulin pump to replace the missing insulin.
Islet cell transplantation requires a donor pancreas, and then the cells are purified and surgically transplanted into the liver where they begin making insulin. Because the islet cells come from a donor pancreas, transplant recipients must take immune-suppressing drugs to keep their bodies from rejecting the new cells.
The new study included 25 people with type 1 diabetes. Twelve had islet cell transplants and 13 acted as controls. All used continuous glucose monitoring systems, which constantly monitor blood glucose levels.
On average, Gorn said, the study participants were able to remain insulin-free for about a year and a half. Forty percent were still insulin-independent at two years, she said.
And whether or not the transplant volunteers were back on insulin or not, they had significantly fewer episodes of hypoglycemia than did the controls. Also, they spent more time with normal blood sugar levels than did the controls. Additionally, when they had to start using insulin again, they were using significantly less than they did prior to the transplant, the study found.
Hemoglobin A1C levels -- a reading of long-term glucose control -- were much improved after transplant. A normal A1C level is about 5 percent for someone without diabetes, according to the American Diabetes Association. The average for transplant recipients was 7.6 percent before the transplant and 5.5 percent after three months, according to the study.
"Compared to the group of controls, those who had the transplant had much less hypoglycemia and had more time in normoglycemia, whether or not they were back on insulin," said Gorn, who added that the researchers also found that "continuous glucose monitoring was useful and was a good indicator of [transplant] dysfunction."
Gorn was expected to present her findings Friday at the American Association of Clinical Endocrinologists' annual meeting, in Orlando, Fla.
Dr. Joel Zonszein is director of the clinical diabetes center at Montefiore Medical Center in New York City. He said "the topic [of islet cell transplantation] is very exciting, and it's very important, but this study doesn't provide a lot of new information.
"Islet cell transplantation works, and it works very well for about a year, but the complications of the agents used to prevent rejection are still there. And, they're also causing a decrease in the survival of the new beta cells," he added.
To learn more about islet cell transplantation, visit the National Institute of Diabetes and Digestive and Kidney Diseases.
Posted: May 2008