Keeping Insulin Hanging Around

12 July 2010 3:00 pm

NEW DELHI—Scientists have cooked up a novel formulation of insulin that slowly releases the hormone into the blood. The preparation, described today in the Proceedings of the National Academy of Sciences, has only been tested so far in animals. If it pans out in people, it could reduce the frequency of insulin injections that diabetes patients must take to stabilize their blood sugar levels. That could be a boon in developing countries, where many people cannot afford insulin pumps that gradually release insulin.

At least 22 million people worldwide are believed to suffer from type 1 diabetes, in which the body destroys insulin-producing cells in the pancreas that help regulate glucose levels. (In type 2 diabetes, which is much more common, the body doesn't respond properly to its own insulin.) People with type 1 diabetes generally need to take insulin for life.

Scientists have tried for years to make life easier for diabetes patients by reducing how often they need to dose themselves with insulin, or giving the hormone in noninjectable forms—but it's been difficult to do this successfully. The new formulation follows a simple recipe. A team led by biophysicist Avadhesha Surolia, director of the National Institute of Immunology here, stirred a warm solution of human insulin for 7 days. The insulin clumped together into complexes called oligomers. These were injected into rats, mice, and rabbits with chemically induced diabetes. A single injection maintained basal glucose levels for up to 3 months, whereas other diabetic mice needed daily injections. Ailing mice not given insulin died within 40 days. According to Surolia, the oligomers act like "an insulin depot" at the injection site, releasing a steady, low insulin dose.

The results are a technical achievement, says Ambrish Mithal, a practicing diabetologist and president of the Endocrine Society of India here who is not affiliated with the research. Others, however, are skeptical that the formulation will pass muster in humans. "The major problem with type 1 diabetes is not provision of basal insulin but rather the ability to decrease and increase [the amount of] insulin available," depending on what the body needs, says endocrinologist George Eisenbarth, director of the Barbara Davis Center for Childhood Diabetes at the University of Colorado, Denver. Furthermore, long-lasting insulin has risks, too, says Eisenbarth: You might end up with more insulin than you need at a given time, and that can cause sudden drops in blood sugar that can lead to fainting and other health problems.

Surolia counters that his group observed no side effects in the animal studies. The team, in collaboration with Life Science Pharmaceuticals in Darien, Connecticut, plans to launch clinical trials later this year.

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