Islet-cell Transplants: The End of Insulin Shots?
Diabetes is a leading cause of blindness, end-stage
kidney failure, and leg amputations. It also increases the risk for
heart disease. Diabetes mellitus results from high blood sugar levels because of the body's inability to produce or effectively use insulin. Insulin is a hormone secreted by the pancreas that aids in storing or converting glucose from food into energy.
Diabetes is not curable, but it can be managed with lifestyle changes and medications.
There are two main types of diabetes. People with
type 1 diabetes
produce little or no insulin. The main treatment regimen for type 1 diabetes is insulin injections throughout the day, measuring blood sugar levels, watching one's diet, and planning structured meals and activities. People with
type 2 diabetes
either do not produce enough insulin or their bodies have difficulty putting the available insulin to work. Some people with type 2 diabetes require insulin injections.
One hope for cure of type 1 diabetes lies in transplanting the islet cells that are in the pancreas. Islet cells produce and secret insulin into the bloodstream.
A Possible Treatment
Doctors have attempted to transplant insulin-producing islet cells from donated pancreases into people with severe, unstable diabetes. The results were that these recipients were able to maintain normal blood sugar levels without taking insulin shots. Does this mean that islet-cell transplants could mean the end of daily insulin injections for people with diabetes? At this point in time, no.
One type of islet-cell transplant method follows a procedure called the Edmonton protocol. This includes transplanting cells immediately after removal from the donated pancreas after removing foreign proteins from the cells. Removing foreign proteins from the cells reduces the risk of transplant rejection. In most cases, islet cells from a second donor pancreas are needed for improved blood glucose control. Doctors infuse the cells into the liver during a simple procedure, and the process carries less risk than an organ transplant.
Does Transplant Work?
Several small studies have looked at islet-cell transplantation in those with type 1 diabetes. The studies overall showed mixed support for transplantation. A study of 36 people that used the Edmonton protocol found that transplantation did restore insulin production in the body, as well as keep blood sugar levels stable. However, the transplant did not make it able for most people to be free from their insulin regimen over time. But another small study using the Edmonton protocol was able to report its people as achieving insulin independence. Overall, the transplanted cells allow people to avoid life-threatening episodes of hypogycemia. Hypoglycemia is abnormally low blood sugar. People who take insulin are at risk of experiencing these dangerous blood sugar crashes. Over the course of several years even people achieving insulin independence may still end up taking insulin.
Doctors also note that islet-cell transplant is not the end of all treatment. Even if insulin is not needed after surgery, antirejection medications are required so the body does not reject the new pancreatic cells. There are side effects to antirejection medications which suppress the immune system. Immune suppression increases the risk of cancer and potentially serious infections. People who have the islet transplant need to see their doctors for regular check-ups. They are necessary to monitor for rejection, and any new changes in insulin regimens.
Lack of donated pancreases will limit the number of people who can receive islet-cell transplants. With limited available organs, scientists are still searching 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.
Juvenile Diabetes Foundation
Organ Donor—US Department of Health and Human Services
Public Health Agency of Canada
The College of Family Physicians of Canada
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