A Loaf of Bread, A Jug of Wine, and Tight Glucose Control With Artificial Pancreas

Neil Osterweil

July 02, 2010

July 2, 2010 (Orlando, Florida) — Adults with type 1 diabetes can eat, drink, and still be in control of glucose overnight, suggest results of a pilot study testing a closed-loop artificial pancreas, reported here during the American Diabetes Association 70th Scientific Sessions.

In a test designed to mimic real-life conditions, 12 adults with type 1 diabetes were fed a large meal accompanied by as much as three fourths of a bottle of white wine and then monitored for overnight hypoglycemia. Patients on the closed-loop artificial pancreas system remained within glucose targets longer and had fewer glucose excursions than when they were on standard continuous subcutaneous insulin infusion (CSII), reported Kavita Kumareswaran, MD, a clinical fellow in the research group led by Roman Hovorka, PhD, from the University of Cambridge, United Kingdom.

"Overnight closed-loop [systems] can provide superior glucose control, even after a few [alcoholic drinks] and a large evening meal, and may improve the efficacy and safety of currently available insulin regimens," said Dr. Kumareswaran.

The artificial pancreas system consists of a CSII, or insulin pump, linked via a control algorithm to a continuous glucose sensor. The Cambridge researchers had previously published data on the closed-loop artificial pancreas showing that it could reduce the risk for overnight hypoglycemia in children and adolescents (Lancet. 2010;375:743-751).

In the current study, they attempted to replicate in the hospital several aspects of daily life, such as the effects on plasma glucose levels of a good meal and a few glasses of wine. Alcohol consumption is associated with delayed hypoglycemia in people with type 1 diabetes. A 2001 study showed that young men with type 1 diabetes had significant hypoglycemia the morning after drinking alcohol (Diabetes Care. 2001;24:1888-1893).

The investigators enrolled 12 adults with type 1 diabetes (7 women, 5 men), all of whom were on CSII. The mean patient age was 37.2 ± 2.9 years, and the mean time since diabetes diagnosis was 19.7 ± 9.7 years. Mean body mass index was 26.8 ± 4.2 kg/m2, and the mean glycosylated hemoglobin was 7.8% ± 0.7%.

The patients were randomly assigned on separate nights to receive either overnight closed-loop control or conventional CSII.

Each night, patients were fed a mixed meal containing 100 g of carbohydrate between 8:30 and 10:00 pm. The meal was accompanied by white wine (a South African chardonnay) with 13% alcohol content, which translates into 0.75 g/kg ethanol. The mean volume of wine drunk was 564 ± 133 mL, or approximately three fourths of a standard 750-mL bottle. The patients were given a prandial insulin bolus concurrently with their meals.

The closed-loop system was started at 10:00 pm and was continued until noon the following day.

Glucose levels were monitored every 15 minutes with subcutaneous continuous glucose monitoring. The values were fed into a model predictive control algorithm, which calculated the insulin infusion rate, which was then manually adjusted for delivery through the subcutaneous insulin pump. On the nights that patients underwent CSII control, their usual insulin pump settings were used.

Results

Patients spent significantly more time within the target glucose range of 70 to 145 mg/dL while on the closed-loop system than they did while on CSII: 70% vs 47%, respectively (P = .01). Although patients on the closed-loop system spent less time either under or over target than they did on CSII, the differences were not statistically significant. There were also no significant differences between groups in mean overnight glucose, standard deviation overnight glucose, or low blood glucose index, although these measures all tipped in favor of the closed-loop system.

There were 4 incidents of hypoglycemia, defined as glucose levels lower than 55 mg/dL. Two occurred when the participants were on the closed-loop system, and both were related to the prandial insulin bolus. The other 2 incidents occurred in patients on CSII. Both occurred after 1:00 am, and 1 was severe (<35 mg/dL).

A diabetes specialist involved in artificial pancreas research, but not in this study, tells Medscape Medical News that the closed-loop system shows considerable promise.

"This particular study was of very short duration, but Roman [Hovorka's] data is quite good, and his group is the closest to demonstrating the technology outside the hospital, so we're very excited to see what's coming. They need to reproduce this, however, with more frequent nights," commented Stuart A. Weinzimer, MD, associate professor of pediatrics at Yale University in New Haven, Connecticut. Dr. Weinzimer comoderated the session at which the data were presented.

Richard Bergenstal, MD, president of medicine and science of the American Diabetes Association, and executive director of the International Diabetes Center at Park Nicollet in Minneapolis, Minnesota, who was not involved in the study, applauded the investigators' slow-but-steady approach.

"They say let's keep moving and do it safely, but let's test if we can build the brains into the pump so that it can respond to the glucose data, and I think they were smart to start with overnight, do it in the hospital in a controlled way, and put a program in that says if the glucose data coming to the sensor from the pump says you're getting low, then slow down or shut off the insulin. Dr. Hovorka has been able to show that in controlled settings that really works, so this is the first step toward closing the loop," Dr. Bergenstal said in an interview with Medscape Medical News.

American Diabetes Association 70th Scientific Sessions: Abstract 0358-OR. Presented June 28, 2010.

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