Pancreatic islet transplantation — a therapy that restores insulin production in the body — was shown to be effective in people with type 1 diabetes who previously had a kidney transplant, as well as in those with no previous transplant, according to a study published in the journal Diabetes Care.
Islet transplantation carries substantial risks, and due to these risks, it’s not a generally recommended treatment for type 1 diabetes. The procedure — which involves transplanting pancreatic islets from a donor pancreas into the portal vein of the liver, where the islets take hold in newly formed blood vessels — requires the recipient to take immunosuppressant drugs to prevent rejection of the transplanted cells. These drugs may increase the risk of infection and cancer, and can have side effects including digestive problems, high blood pressure, and kidney damage. Even when a doctor determines that the benefits of the procedure are likely to outweigh the risks — often due to a person experiencing frequent and severe hypoglycemia (low blood glucose) — access to the procedure is limited by the available supply of donor islets, which must be extracted and purified in a laborious process. One company is developing islet cells derived from stem cells in an effort to overcome the limited supply of donor pancreases, and there have also been studies looking at ways to prevent rejection of transplanted cells without needing to take immunosuppressant drugs.
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Despite the risks and limitations of the procedure, many experts believe that islet cell transplantation is not as widespread as it should be in the United States — especially compared with Europe, where it’s more common. That’s largely because of how the procedure is regulated in the United States. Studies have shown that islet transplantation can have long-term benefits when it comes to improved blood glucose control and needing to take less insulin.
For the latest study, researchers compared outcomes in adults with type 1 diabetes — 48 who underwent only islet cell transplantation, and 24 who underwent the procedure following a kidney transplant. Both groups of participants took standard immunosuppressant drugs, and were followed for up to eight years to find out how well the islet transplant was working. Outcomes of interest to the researchers included survival of transplanted islets, an A1C level (a measure of long-term blood glucose control) below 7.0%, and insulin independence (not needing to take insulin).
During the follow-up period, 15 participants in the islet-only transplant group and seven in the kidney-plus-islet transplant group withdrew from the study at a time when they maintained islet graft function. Another seven participants in the islet-only group and nine in the kidney-plus-islet group experienced islet graft failure, meaning they no longer produced enough insulin to have any relevant effect on blood glucose. That left 26 participants in the islet-only group and eight in the kidney-plus-islet group who completed follow-up and still had islet graft function.
Majority of participants experienced lasting islet graft survival
Overall median islet graft survival during the follow-up period was 84% in the islet-only group and 69% in the kidney-plus-islet group. Islet graft survival at the end of the follow-up period was 56% in the islet-only group and 49% in the kidney-plus-islet group.
When it came to A1C, a median level below 7.0% was seen in 77% of the islet-only group and 57% in the kidney-plus-islet group, and a level below 7.0% at the end of the follow-up period was seen in 49% of the islet-only group and 35% in the kidney-plus-islet group.
Insulin independence was seen, for at least some period of time, in 74% of all study participants, and over half maintained it during the follow-up period. In both the islet-only and kidney-plus-islet groups, over 90% of participants had zero episodes of severe hypoglycemia during the follow-up period. And in both groups, kidney function remained stable.
The researchers concluded that islet transplantation resulted in lasting islet graft survival, leading to improved blood glucose control and freedom from severe hypoglycemia in most recipients — whether or not they previously had a kidney transplant — and that the immunosuppressant drugs appeared to have an “acceptable” safety profile during the follow-up period. These results are likely to renew calls for wider access to islet cell transplants.