No one is sure exactly why it happens, but in some people, and at an early age, the immune system attacks and destroys the pancreatic beta cells until the body no longer can produce insulin. But not knowing exactly why it happens did not stop one group of scientists from stopping type 1 diabetes in mice.
Can we stop type 1 diabetes?
Type 1 diabetes, previously called juvenile diabetes because it first appears during childhood or in young adults, is an autoimmune disease in which the pancreas stops making insulin. About 5 percent of the nearly 26 million children and adults with diabetes in the United States have type 1 disease, which is equivalent to about 1 in every 400 children and adolescents.
Finding a way to put the brakes on the development of type 1 diabetes in humans would be a monumental breakthrough, and this new study from Karolinska Institute in Sweden is a significant start. The brakes were applied to genetically susceptible mice by injecting them with specially prepared cells.
Scientists have known that immune system cells called macrophages are involved in the destruction of beta cells. However, macrophages don't always attack beta cells: they can be instructed to protect rather than destroy. So the scientists looked for the cells that give the instructions, and those are immune cells called cytokines.
According to the lead researcher, Robert Harris, he and his team discovered which cytokines send signals to macrophages to protect rather than to destroy. "We managed to achieve this aim, defining a novel combination of cytokines that confer on macrophages the ability to protect mice from developing Type 1 diabetes."
The mice used in the study were genetically susceptible to develop the autoimmune disease within 12 to 30 weeks after birth. At age 16 weeks, the mice were placed into one of three groups:
- Mice that received macrophages treated with a specific set of cytokines
- Mice that received untreated macrophages
- Mice that did not receive any macrophages
The mice in all three groups were observed for three months to see what would happen to the beta cells. In the mice that received macrophages treated with cytokines, only 25 percent developed type 1 diabetes compared with 83 percent of the mice in the other two groups.
Harris noted that even though they introduced the cytokine-treated macrophages just two weeks before the mice developed type 1 diabetes, a point when there are only a few beta cells remaining that can produce insulin, "we were able to protect these so that the mice never developed diabetes."
What causes type 1 diabetes?
Experts believe both genetic and environmental factors have a role in triggering the events that lead to the destruction of the beta cells in the pancreas and the resulting type 1 diabetes. Viral infections, including enteric viruses that attack the intestinal tract, are among the possible environmental factors behind type 1 diabetes.
Other environmental factors include a vitamin D deficiency, which has been proposed as a possible cause of development of type 1 diabetes in children. At least one study has also suggested that women who eat more vegetables during pregnancy may help protect against development of the disease in their children.
At least 18 genetics locations have been identified as being related to type 1 diabetes, and others may be found. Genetics does not appear to have a large role, however. Most individuals who develop type 1 diabetes have no family history of the disease. In fact, the chances of inheriting the disease are only 10 percent if someone has a first-degree relative with diabetes.
The new Swedish study is significant in that "such a successful late-stage intervention has never previously been reported." Scientists were able to stop type 1 diabetes at a stage when "most human individuals have already lost most of their insulin-producing beta cells."
American Diabetes Association
Holick MF. The D-lightful vitamin D for child health. J Parenter Enteral Nutrition 2012 Jan; 36(1 Suppl): 9S-19S
Parsa R et al. Adoptive transfer of immunomodulatory M2 macrophages prevents type 1 diabetes in NOD mice. Diabetes 2012 Jun 28; DOI:10.2337/db11-1635
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