For years, the transplantation of insulin-producing pancreatic islet cells has held promise as a potential cure for Type 1 diabetes. Now, a new study has shown that while transplantation can help recipients improve their blood glucose control, the transplanted cells tend to lose function progressively, requiring most recipients to resume insulin injections within two years.
The study, which was published in the September 28 issue of The New England Journal of Medicine, enrolled 36 adults with Type 1 diabetes and hypoglycemia unawareness (a condition in which a person no longer experiences warning signs of low blood glucose levels). At nine transplant centers throughout North American and Europe, participants in the study received up to three infusions of donated islet cells. The centers used a standardized transplantation technique called the Edmonton protocol, which was developed at the University of Alberta, Edmonton, in Canada and showed promise in a smaller study published in 2000.
All participants had to go on a regimen of immunosuppressive drugs to keep their bodies from rejecting the transplanted cells.
One year after the final infusion, 44% of the study participants did not need insulin injections, and another 28% had partial islet cell function and needed less insulin than they had before their transplants. The transplants failed in the final 28%.
After two years, however, only 14% of participants did not need insulin injections, and by the third year only one participant out of the original 36 was still injection-free. In addition, side effects from the immunosuppressive drugs led 25% of subjects to change their therapy or withdraw from the study.
The study’s outcome was disappointing in that the transplants did not succeed in providing people with Type 1 diabetes with long-term freedom from insulin injections. However, the islet cell transplants did provide protection from severe hypoglycemia and improved HbA1c levels (a measure of blood glucose control over the long term) in participants who achieved even just partial islet cell function.
With further innovations in transplantation techniques and the development of new immunosuppressive drugs, researchers hope to see improved islet cell transplantation outcomes in the near future. What’s more, some small studies have recently shown that the injectable Type 2 diabetes drug exenatide (brand name Byetta) may actually help improve cell survival after islet cell transplantation in people with Type 1 diabetes.