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Type I Diabetes: When your pancreatic islets die |
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Written by Lev Prasov
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Apr 01, 2006 at 11:45 AM |
Type I diabetes is an autoimmune disease in which the insulin-secreting cells of the pancreas are destroyed. There are many long-term complications, but some promising treatments are on the horizon.
Diabetes mellitus, the term used to describe a disease involving relative insulin deficiency, comes from the Greek words diabaínein ("pour through") and the prefix mel ("sweet"). These words describe one of the major symptoms of diabetes, the excessive urination of a sweet liquid (containing glucose). In the old days, the diagnosis of diabetes was based on just this symptom. When people suffered from frequent urination, they would go to a urine taster to see if their urine was sweet. However, what a urine taster could not tell is the cause of the diabetes. Over the 19th and 20th centuries, we have made great strides in determining the cause of diabetes and developing treatments to curb its debilitating effects. We now know that there are two major types of diabetes, aptly named Type I and Type II diabetes. Most people are familiar with the Type II diabetes, a growing epidemic in the United States, but its cousin Type I diabetes is often overlooked and it is the topic for this week's DOTW.
Figure I: The Pancreatic Islet Cells. The green-stained cells are the insulin-secreting pancreatic islet cells. (Image courtesy of Wikipedia)
Type I diabetes is part of a general class of autoimmune diseases. These diseases occur when a person's immune system begins to attack its own cells. In particular, these diseases are mediated by T cells, whose normal function is to recognize foreign substances (such as bacterial or viral peptides) and to stimulate other immune cells to respond. In Type I diabetes, the insulin-secreting pancreatic islet cells (see Figure I) are the target of the immune response. These cells are literally devoured by immune cells. The result is a lack of insulin, the hormone whose normal role is to suppress blood sugar levels by moving glucose into muscle and liver cells.
As in Type II diabetes, the increase in blood glucose has numerous adverse effects. However, the full progression of diabetes can be very slow. The first signs and symptoms are usually that of frequent urination and the thirst that accompanies it. This results from an inability of the kidneys to take up the high amounts of glucose that are filtered. In turn, glucose is excreted in the urine and it drives water with it by shifting the osmotic gradient. In addition, high blood glucose can cause changes in the shape of the lens of the eye, causing blurred vision. Another more severe symptom of diabetes is ketoacidosis, which can lead to lethargy, shock, and death if untreated. This condition results when the body uses fat as a primary energy source, because glucose cannot enter cells.
There are many long term complications of untreated diabetes. Over time, the kidneys may fail due to the increasing strain put on them by high glucose levels and the other metabolic effects of the disease. In addition, diabetes can cause proliferation of blood vessels in the eye, leading to severe vision loss. Damage to nerves in the limbs and body is another severe complication of diabetes. People with diabetes also have an increased risk of stroke and heart disease.
While the long-term complications of diabetes are devastating, Type I diabetes can be managed to avoid these effects. The most common treatment for Type I diabetes is a combination of insulin injections and changes in dietary habits. Patients must carefully monitor their blood glucose levels and inject appropriate amounts of insulin to offset their high blood glucose levels. While this is an adequate treatment, it is not a cure, but merely a way to reduce the problems associated with diabetes. There is currently no cure for diabetes, but several approaches may be promising for the future. Researchers are trying to devise ways to transplant the pancreas, transplant just the islet cells, engineer an artificial pancreas, or stop the autoimmune reaction in an attempt to cure the disease.
For more information on Type I diabetes, check out the following resources:
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