| Insulin May Trigger Diabetes |
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11 May 2005, for ScienceNOW Sufferers of type 1 diabetes require regular doses of insulin to keep their blood sugar levels steady. Now two studies provide strong evidence that insulin itself may trigger the disease. In type 1 diabetes, also known as juvenile-onset diabetes, the immune system's T cells proliferate wildly in the pancreatic lymph nodes and invade the pancreas itself. This causes inflammation that kills the highly sensitive, insulin-producing cells in the pancreas, called beta cells. Many proteins have been implicated in triggering this inflammation, but scientists weren't sure which ones were the ringleaders. Now a study in mice and another in humans bolster the idea that insulin is critical to the development of type 1 diabetes and perhaps is the most important trigger. George Eisenbarth, an endocrinologist at the University of Colorado Health Sciences Center in Denver, and his colleagues took a mouse strain prone to developing type 1 diabetes and inactivated its genes for insulin. They then added a mutated insulin gene that makes a version of the protein that still regulates blood sugar but which differs in a region recognized by T cells. With this masked insulin, the mice did not develop diabetes, strongly suggesting that T cells must recognize insulin for the disease to start.Another study, also published in the 12 May issue of Nature, hints that insulin triggers T cells' deadly response in humans too. Immunologist David Hafler of Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, and his colleagues isolated T cells from the pancreatic lymph nodes of diabetic and nondiabetic patients--something that hadn't been done before. The researchers found that when insulin was added to the diabetic cells in culture, they began to multiply. The same response was not seen in the nondiabetic cells. The researchers believe the findings suggest that insulin is a call to arms for these T cells, triggering them to multiply in the body when mounting an attack. "These studies suggest that recognition of insulin by T cells is a major--perhaps essential--pathway in the development of type 1 diabetes," says Harald Von Boehmer, an immunologist at Harvard Medical School. The findings could be used to develop therapies for the disease, he says, by indicating, for example, which T cells should be targeted and destroyed to prevent damage to the pancreas. |