Researchers have long sought ways to treat type 1 diabetes, an autoimmune disease that afflicts about three people in every thousand. Standard therapy for these patients, who are unable to produce insulin on their own, focuses on delivering externally produced insulin to the body via injection or external pump. These treatments, in addition to being inconvenient for patients, are unable to adjust blood glucose levels on a minute-to-minute basis, as beta cells do in a healthy individual. But attempts to cure diabetes through transplant or regeneration of insulin-producing cells have failed. Now a novel type of gene therapy described in the November 23 issue of the journal Nature offers hope. According to the report, diabetic mice and rats went into remission five days after receiving the insulin-encoding gene.
Hyun Chul Lee and Su-Jin Kim of Yonsei University in Seoul, Korea and their colleagues turned to genetic engineering to produce an insulin analogue. They then inserted the DNA encoding this analogue into a virus that had been rendered harmless, incorporated the region of the liver cell that responds to glucose, and injected the modified virus into diabetic mice and rats. The animals were subsequently able to produce the insulin analogue in response to changes in their blood-glucose levels throughout the eight month study period.
Whether this approach will work in humans remains to be determined, Jerrold M. Olefsky of the University of California at San Diego writes in a commentary accompanying the report. "Rodents are quite different from humans with respect to maintaining glucose levels," he notes, "and extending these results to human physiology may prove a challenge." Still, that these researchers were able to create a system in which insulin is delivered in response to changing needs, he concludes "is a definite step forward.