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Artificial Pancreas May Improve Overnight Control of Diabetes in Adults

Posted: Saturday, April 23, 2011

The "artificial pancreas" can improve overnight blood sugar control while keeping hypoglycemia at bay, even after a big meal and a glass of wine.

Roman Hovorka, MD, of the University of Cambridge, and colleagues reported that, the closed-loop system performed better than standard pump therapy after both a big meal with alcohol, and a normal-sized meal, meant to represent a "dine-out" and an "eat-in" situation.

"The closed-loop system has the potential to improve safety and efficacy of insulin delivery and may in the future allow more flexible lifestyles in conjunction with improved glycemic control for people with Type 1 diabetes," they wrote.

Hovorka's group has long been studying the overnight efficacy of a closed-loop insulin delivery system. Last year in The Lancet they reported that the device -- which is comprised of an insulin pump, a continuous glucose monitor, and a control algorithm -- improved nighttime blood sugar control in pediatric patients.

For the present study, Hovorka and colleagues conducted two open-label, randomized, controlled crossover studies involving 24 patients with Type 1 diabetes, ages 18 to 65.

Half of the patients were given a large meal (100 grams of carbohydrate) plus a glass of wine at 8:30 pm and tested overnight using the closed-loop system, and then crossed over to the open-loop system using an insulin pump.

The other half was tested in the same crossover manner, but after consuming a normal-sized meal (60 grams of carbohydrates) earlier in the evening, at 7 pm.

Meal sizes were meant to represent either a "dine-out" or "eat-in" situation. The primary outcome was the time plasma glucose levels were in the target range of 70 mg/dL to 144 mg/dL (3.91 to 8.0 mmol/L).

Overall, the researchers said the average doses of insulin delivered via either system were comparable. For the eat-in situation, the researchers found that the closed-loop system increased the time that plasma glucose levels were in the target range by a median 15% (P=0.002). It also decreased glucose variability overnight and lessened the time spent in hyperglycemia and hypoglycemia, the researchers said.

For the dine-out situation, the closed-loop system increased the time spent in range by a median 22% (P=0.01) compared with standard pump therapy. They noted that alcohol didn't affect the performance of closed-loop delivery.

The pooled analysis showed that the overall time plasma glucose was in the target range increased by a median 22% with the "artificial pancreas" (P<0.001). It also reduced overnight time spent in hypoglycemia by a median 3% (P=0.04).

Hovorka and colleagues noted that the study was limited by a small patient population, and by a potential lack of generalizability: the majority of patients were white and compliant, so the findings may not apply to non-white or non-compliant populations.

The investigators also cautioned that in the closed-loop system, a nurse manually entered sensor glucose values into the control algorithm and manually adjusted the insulin pump. However, the researchers said that "presumably the lack of automation did not affect the performance of the closed-loop system, but will need to be dealt with before proceeding to home testing."

The researchers added that closed-loop systems may be a bridge until Type 1 diabetes is "cured, for example, by stem cell therapy or islet transplantation."

Source: http://www.diabetesincontrol.com/index.php?option=com_content&view=article&id=10803&catid=53&Itemid=8, Hovorka R, et al "Overnight closed loop insulin delivery (artificial pancreas) in adults with Type 1 diabetes: crossover randomized controlled studies" BMJ 2011; DOI: 10.1136/bmj.d1855.