Managing type 1 diabetes is a feat of organization and control. The better a diabetic can keep blood sugar in check, the less likely are long-term health complications. But even with devices like automated insulin pumps, which release a continuous dose of insulin, diabetics still need to remember to add an extra dose of insulin at meals, and many spend a significant amount of time each day with blood-sugar levels either higher or lower than normal.
Scientists have been working to develop an “artificial pancreas” system that would monitor blood-sugar levels and normalize them automatically, without any human input. A preliminary clinical trial detailed this month in Science Translational Medicine marks a significant advance in creating a fully automated system. The system was able to control blood sugar in a small group of diabetic patients, even when patients ate high-carbohydrate meals, which is one of the major challenges for artificial-pancreas systems.
Most artificial-pancreas systems under development pair a blood-sugar monitor with an insulin pump. The device in this study adds another component that monitors the hormone glucagon, which counteracts insulin. Glucagon helps prevent blood-sugar levels from dropping too low if too much insulin is given. Although diabetics still produce glucagon, it doesn’t always function properly.
“Our feeling is that glucagon is an important extra measure of safety,” says Steven Russell, an endocrinologist at Massachusetts General Hospital, who co-led the research. Russell explains that hypoglycemia can be a major problem for diabetics–paradoxically, the better diabetics control their blood sugar, the more they are at risk. Hypoglycemia, which occurs when blood sugar drops too low, can lead to sweating, trembling, dizziness, and confusion, and in some cases it can be life-threatening.
The new study was primarily designed to test an algorithm the team developed to predict the amount of insulin and glucagon needed to keep blood-sugar levels normal. Edward Damiano, a bioengineer at Boston University and co-leader of the study, says that because insulin is absorbed and cleared from the body slowly, the algorithm can’t simply respond to the current blood-sugar level but must also anticipate where it is headed. “At each dose, it keeps track of the rising insulin it’s given, as well as the decay of previous doses,” he says.
The system was tested in 11 adults with type 1 diabetes for a period of 27 hours, during which the subjects ate three high-carbohydrate meals. Rather than relying on a glucose monitor under the skin, the researchers took direct blood-sugar readings from the blood every five minutes. Software then calculated the amount of insulin and glucagon needed. Doses were administered by nurses.