LOS ANGELES -- Boston researchers have made a major step toward the development of an artificial pancreas that overcomes the bugaboo of most previous such attempts dangerously low blood sugar caused by injection of too much insulin.
Their new experimental device secretes two hormones normally produced by the pancreas -- insulin and its counterbalancing hormone, called glucagon and has been shown to control blood sugar levels accurately in about a dozen people for at least 24 hours, they reported last week.
The team is now planning longer trials as they gear up for what they hope will be approval by the Food and Drug Administration in as little as seven years.
“This is a very important proof of concept study,” said Dr. Irl B. Hirsch, an endocrinologist at the University of Washington School of Medicine, who was not involved in the research. “It was becoming obvious that if we were ever going to get (an artificial pancreas), we would have to use both hormones. ... The fact that they have been able to do so successfully is very big and very exciting news.”
Most people know that Type 1 diabetes, which affects more than a million Americans, is caused by the loss of insulin-secreting beta-cells in the pancreas. Few realize, however, that the disease also affects alpha-cells of the pancreas, which secrete glucagon to raise the level of sugar in the blood. Together, the two hormones help the body in the delicate balancing act of maintaining blood sugar levels that are neither too high nor too low.
Researchers have made tremendous advances in controlling blood sugar levels with continuous monitors and insulin pumps, “but one of the challenges is that we have an accelerator but not a brake,” which means blood sugar levels can fall too much, said molecular biologist Aaron Kowalski, a vice president of the Juvenile Diabetes Research Foundation, which partially sponsored the new research. The glucagon research, reported in the journal Science Translational Medicine, provides that brake.
What the Boston team has actually invented is a computer algorithm that responds to changes in blood sugar and computes how much insulin or glucagon to inject. Biomedical engineer Edward Damiano of Boston University began developing it a decade ago when his then-11-month-old son David was diagnosed with diabetes. He put the algorithm in a laptop and paired it with off-the-shelf insulin pumps (which could also be used to inject glucagon) and glucose monitors that are implanted under the skin.
After Damiano proved the system would work in diabetic pigs which are remarkably similar to humans physiologically Dr. Steven Russell of Massachusetts General Hospital suggested that they test it in humans. Their first tests were conducted in 11 diabetics who were hospitalized for 27 hours for the tests.
It was “a really rigorous test,” Russell said. “We fed them three very-high-carbohydrate meals, which is the most challenging part of automated control.”
Six of the patients experienced no hypoglycemia, but five had episodes that required they drink orange juice to recover. Subsequent analysis showed that those patients absorbed and metabolized insulin more slowly than normal. When Damiano adjusted the algorithm to account for this slowed absorption, all passed a repeat of the trial with flying colors as did the six who did well the first time around.
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