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NEW ORLEANS -- A automated insulin delivery system was as safe and effecting as a version that administered both insulin and glucagon for type 1 diabetic patients, researchers reported here.

The insulin-only "bionic pancreas" -- a closed-loop system that dispenses automatically based on need -- was compared at slightly higher glucose targets (130 mg/dl and 145 mg/dl) with three bihormonal versions of the device with lower glucose targets (100 mg/dl, 115 mg/dL, and 130 mg/dl), reported , of Massachusetts General Hospital in Boston, and colleagues.

There was a significant reduction in mean glucose levels when comparing the bi-hormonal bionic pancreas with a target of 100 mg/dl to a patient's usual care (P<0.028), and a significant increase in mean glucose levels when comparing the insulin-only bionic pancreas with the highest glucose target of 145 mg/dl with patient's usual care (P<0.034), they said in a presentation at the American Diabetes Association (ADA) annual meeting.

"This is the to use an insulin-only version of the bionic pancreas," said Ekhlaspour at an ADA press conference. "For that reason, we chose significantly higher blood glucose targets to make sure we can keep the level of low blood sugars low in this study."

In a second, separate study, evaluated the home use of a bihormonal bionic pancreas compared with conventional insulin pump therapy, also in adults with type 1 diabetes.

Insulin-Only Bionic Pancreas

The study examined 20 adults with type 1 diabetes (ages 20 to 77) for a total of 72 hours. Patients were allowed to perform normal daily activities with no diet or exercise restrictions.

Prior studies had shown that the average person with type 1 diabetes is hypoglycemic for about an hour a day. In this study, patients were hypoglycemic, on average, for about 20 minutes per day, and with both the 130 mg/dl target insulin-only and bihormonal bionic pancreas, average hypoglycemia was 11 minutes per day.

However, Ekhlaspour noted that the difference between the latter two time-frames was not significant, which was likely due to the study's short duration, as well as the relatively small patient population.

In addition, there was no significant difference between either of these bionic pancreas types and a patient's usual care (158, P>0.28 for all comparisons).

There also was no significant difference in the mean glucose in patients who used either the insulin-only or bihormonal bionic pancreas with a glucose target of 130 mg/dl (161 versus 156, P>0.28). There was also no significant difference in hypoglycemia between these two groups (0.8 versus 0.6, P>0.28).

Ehklaspour said that her group would like to see whether they can safely achieve a lower mean glucose with an insulin-only system, while still maintaining low levels of hypoglycemia.

"With this in mind, we are now investigating an insulin-only bionic pancreas with a glucose target [of] 110 mg/dl in order to find the glucose target that will provide the best balance between mean glucose and hypoglycemia in the insulin-only configuration," she said in a statement.

Bihormonal Pancreas

For the bihormonal bionic pancreas, the researchers found that patients use of was and hypoglycemia versus usual care (an insulin pump).

This multicenter cohort of adults has been studied before, but this time, the patients were their own controls, explained , of Boston University, and colleagues.

They either received the bihormonal bionic pancreas system or their usual care on randomized days. "During the bionic pancreas arm, data from a continuous glucose monitor was used by an autonomously adaptive algorithm to control subcutaneous delivery of insulin and glucagon. During the comparator arm, participants managed their own conventional insulin pump therapy," the authors noted.

When using the bionic pancreas system, there was a statistically significant reduction of around 20 mg/dl in mean glucose levels (141 versus 162 mg/dl, P<0.001) compared with usual care with an insulin pump.

The bionic pancreas system was also linked to a significant reduction in hypoglycemia (<60 mg/dl) for patients compared with the usual care regimen (0.6% versus 1.9%, P<0.001).

On days that patients used the bionic pancreas system, researchers also found a significant reduction in the mean number of symptomatic hypoglycemic events versus usual care (0.59 versus 0.90 events per day, P=0.023). Compared with usual care, the bionic pancreas system was also associated with less intersubject variability in daily glucose levels (±10 mg/dl versus ±30 mg/dl).

At the ADA presentation, co-author and and creator of the bionic pancreas , also of Boston University, was asked if his group was going to examine the effects of chronic use of glucagon in a bihormonal system including the potential risk of long-term use.

"In terms of chronic use, the promising thing is we are using glucagon in very small doses," at 0.5 mg/day, he replied. "Ultimately, the clinical trials we're going to conduct next year is 12 months of exposure, so we'll need to monitor that."