How Close Are We To An Artificial Pancreas?
- Published on Monday, 11 October 2010 11:14
By Lee Lefton
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Dealing with type 1 diabetes is a 24/7/365 job. I know that firsthand since I’ve lived with the disease for the past 44 years. As a result, I’ve always tried to stay on top of emerging technologies that can potentially help diabetics manage their disease while decreasing the risks of devastating, short and long term complications. Now, there’s an exciting tool in the prototype stage that holds the promise of doing exactly that. Known as the Artificial Pancreas System, this combination of diabetes and computer technologies will ideally free type 1 diabetics from constantly having to test their blood sugar levels and adjust how much insulin they need, based on their food and exercise. And, it will eliminate the need for daily insulin injections. In a recent clinical trial, the system enabled all of the study participants to achieve near-normal blood sugar levels for more than 24 hours. |
A Global Partnership Effort
The Juvenile Diabetes Research Foundation, in its ongoing quest for finding a cure for type 1 diabetes, launched the Artificial Pancreas Project in 2006 under the direction of Aaron Kowalski, Ph.D. This recent study and others stem from progress that has been made possible by the JDRF-funded Artificial Pancreas Consortium that has multiple teams in multiple countries working to develop the automatic systems and computer programs needed for an artificial pancreas, and to establish their scientific feasibility.
The first device, developed through a collaboration of experts from Boston University, Massachusetts General Hospital and Harvard Medical School, delivers two hormones that are deficient in type 1 diabetes — insulin, which keeps blood sugar levels from going too high after a meal, and glucagon, a naturally occurring hormone that prevents blood sugar levels from dropping too low. The researchers added glucagon to the system to more closely mimic the physiology of a person without diabetes.
Because the artificial pancreas doesn't rely on human input, it's called a "closed-loop" system.
"A bi-hormonal closed-loop system is feasible and it can give you good average blood sugar readings,” explained one of the device's designers, Edward Damiano, Ph.D., an associate professor of biomedical engineering at Boston University and the father of a son with type 1 diabetes. "What we've developed is automated decision-making software that uses a mathematical formulation to infuse varying amounts of insulin and glucagon when needed," he added.
How The System Works
The artificial pancreas takes existing diabetes technology a step further. A computer program continuously takes in data from a continuous glucose monitoring system (CGMS) inserted into the patient’s vein, and calculates the amount of insulin or glucagon that needs to be infused through an insulin pump.
"We're bringing to people with type 1 diabetes not only the proper amount of insulin dosed correctly, but also the ability to provide a little bit of glucagon after meals, if the insulin dosing turned out to be a little excessive,“ said Dr. Damiano. “That typically is enough to prevent people from becoming hypoglycemic. So it really prevents you from going low, and that's its main function."
“Although we run it on a laptop so that we can monitor its operation, the algorithm itself doesn't require a lot of computer power and could easily be run from a chip that has the capabilities of one that's already in insulin pumps or cell phones,” he added.
The Study’s Main Findings
In the recent trial designed primarily to test the software controlling the artificial pancreas, 11 adults with type 1 diabetes wore the system for 27 hours. Each ate three high-carbohydrate meals and stayed overnight at the hospital. The system kept the glucose level of six of the participants close to 140 mg/dl — substantially below the American Diabetes Association’s recommended target level of less than or equal to 154 mg/dl. The five others experienced some degree of hypoglycemia requiring them to drink some orange juice. This was attributed to individual variation in insulin metabolism. By adjusting the software and lowering the insulin absorption rate, none of the participants experienced significant hypoglycemia in a repeat study.
“This is the first study to test an artificial pancreas using both insulin and glucagon in people with type 1 diabetes,” said co-lead researcher Dr. Steven Russell, of the MGH Diabetes Center and instructor in medicine at Harvard Medical School.
A follow up, 48-hour study involving both adults and children is planned for the future. It will use the revised settings and an FDA-approved continuous glucose monitor, and will include a comparison of the two-hormone system with one that uses insulin only.
The Prognosis for the Future
Dr. Russell envisions a future system to be a wearable device incorporating a glucose sensor that fits under the skin and communicates wirelessly with a pump about the size of a cell phone.
"The pump would administer insulin and probably glucagon, and would contain a microchip that runs the control software," he said.
One of the first questions people are asking is when will the system be available commercially.
“We’ve targeted a four year time horizon,” said Dr. Kowalski. “There are going to be more major studies which I predict will be very successful. Our next step will be to work our way through the FDA, which is probably going to be our biggest wild card. This is a pretty novel technology and it’s going to take some discussion with them about how to do the right studies. But the pieces of the puzzle do exist. Right now, it’s a matter of putting them together and proving we can do this. I’m very, very confident.”
The other overriding question is one of cost.
“The cost should be pretty much what we deal with pumps and sensors now,” Kowalski said.
Damiano estimates the system will cost up to $7,000 for the glucose monitor and pump, plus another $100 a week for insulin, glucagon, and sensors that must be replaced every few days.
“The really important thing to consider is cost-effectiveness,”
Kowalski said. “The costs associated with diabetes complications are enormous. When someone ends up in the hospital a couple times a year, it can run into the tens of thousand of dollars.”
“When we combine the pump with the sensor and layer in automation, you’ll see significant improvements in glucose control, which will greatly minimize the risk for long term complications as well as acute incidents of ketoacidosis and hypoglycemia,” he added.
Challenges and Hurdles
While diabetes specialists are calling the study a positive step forward, there are still some challenges.
Dr. Howard Wolpert of the Joslin Diabetes Center in Boston said that because continuous glucose monitoring systems measure sugar in the fluid between the cells instead of the bloodstream, they’re not as accurate, and don’t do what a normal pancreas does.
“The system can’t turn on and off rapidly enough to respond to changes in the glucose level,” he said.
Dr. David Harlan, Director of Diabetes at UMass Memorial Medical Center and former Diabetes Branch Chief at the National Institute of Diabetes and Digestive and Kidney Diseases sees issues as well.
“The new system’s advance is that it can respond by infusing glucagon to overcome low blood sugars, but it doesn’t control doses of insulin or glucagon finely enough. Imagine driving a car where the accelerator was all the way down or not. You could control the speed of the car by taking your foot completely off it or flooring it and then putting your foot on the brake. It works, but it’s not ideal.”
While acknowledging the challenges, Dr. Kowalski remains continually optimistic.
“One of the hardest parts of living with diabetes is the constant battle to calculate what’s going on and to try to maintain a healthy balance,” he said. “How much did I eat? Should I have a bedtime snack? Why is my blood sugar high or low now? How many carbs, etc? This device can alleviate some or most of the mental burden of diabetes, which I think would be huge from a quality-of-life standpoint.”
“Finally, we believe that an artificial pancreas will help us get to our ultimate goal sooner: a biological cure that will enable us to walk completely away from diabetes.”
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| The Lancet |
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