Diabetes Control

In 2007, the Juvenile Diabetes Research Foundation (JDRF) provided approximately $6 million to fund two studies that tested the viability of both components of a closed-loop system, a glucose sensor and an insulin pump. One is the Continuous Glucose Sensor Human Clinical Trial, and the other is the Artificial Pancreas Consortium. We spoke to Aaron Kowalski, research director for the JDRF Artificial Pancreas Project, about the two studies and what they hope to achieve.

Continuous glucose sensors are glucose monitors worn on the outside of the body. The sensors have a small-needle access site, which is usually positioned in the abdominal region. This allows the device to continually monitor glucose levels. The data that it collects is displayed on a small device about the size of a pager. A continuous glucose sensor enables a person to see glucose trends - whether glucose is headed up or down before they go too far in either direction. This lets the person avoid bad lows or excessive highs by having a snack or adjusting insulin levels.

The hypothesis is that continuous sensing is going to help people with diabetes achieve better glucose control than they would using only finger sticks, and several studies have shown promising results. By helping people achieve better glucose control, these devices will help reduce diabetes-related complications in the long term. And they will be an essential part of the closed-loop system, or artificial pancreas.

Currently two companies have FDA-approved continuous glucose monitors? DexCom and Medtronic and a third (Abbott) has a device currently under FDA review. The JDRF does not favor one brand of device over another; the Continuous Glucose Sensor Human Clinical Trial uses all of them.

Half of the patients will get their normal standard of care, which is intensive management with finger sticks using glucose monitors. The other half will use continuous sensors. That will go on for six months in a randomized fashion. Then the people who are on finger sticks will switch to the continuous sensors. The people on continuous sensors will stay with them. We call that a limited crossover. It will go on for another six months. We expect to enroll about 500 patients total at sites across the country.

In the first six months, we will see whether the people using continuous sensing have better glucose control. We’ll be looking at A1Cs, but we’ll also be trying to get a good picture of how the sensor affects the incidence of hypoglycemia and glycemic variability (the swings up and down of blood glucose) and other diabetes outcomes, such as severe lows, days out of work or school due to diabetes, etc. In the second six months, we will see if people can sustain any positive outcomes from using the sensor over the longer period of time.

The clinical trials operate separately, but they are linked conceptually. You can’t have a closed-loop system without a reliable continuous glucose monitor. You need a continuous monitor that talks to an insulin pump, and that insulin pump has to be able to take the sensor’s readings, then automatically dispense insulin through the inserted port as the body needs it. Like the pancreas, the closed loop would automatically dispense the right amount of insulin at the right time.