Toward a hybrid artificial pancreas.

Management of insulinopenic diabetic individuals centers on administration of insulin by means of multiple injections, a wearable or implantable insulin-infusion pump, or a whole-organ or segmental-pancreas transplant. Preliminary trials indicate that surgical implantation of a hybrid device containing living insulin-secreting tissue may function as a combined glucose sensor and insulin-infusion pump. By means of a chamber composed of a semipermeable membrane shaped into hollow fibers or a box surrounding endocrine tissue, pilot studies have shown that isolated islets of Langerhans, fragments of insulinoma, or a fetal pancreas retains function for days to weeks, as judged by the ability to sustain euglycemic conditions in chemically induced diabetic rats. Lacking clear proof that normalizing blood glucose levels will prevent vascular complications of diabetes in humans, the case for further development of a hybrid (tissue plus fabricated components) device rests mainly on optimistic extrapolation of results attained in the chemically induced diabetic rat and dog. For the minority of diabetic patients who have insulin-dependent diabetes, the benefit afforded by a bionic device establishing internal insulin release regulated by silently sensed blood glucose level is more than enough payoff for the discomfort and surgery involved in its implantation. Further trials of a hybrid artificial pancreas in the dog appear warranted as a logical extension of preliminary studies with this species.