MEDICINE

New weapons in the war on diabetes

MALCOLM GRAY May 30 1988
MEDICINE

New weapons in the war on diabetes

MALCOLM GRAY May 30 1988

New weapons in the war on diabetes

MEDICINE

In 1921 four Toronto researchers— Frederick Banting, Charles Best, J. B. Collip and J. J. R. Macleod — found that a hormone extracted from pig pancreases effectively controlled diabetes. Since that breakthrough, the discovery of insulin has prolonged the lives of millions of diabetes sufferers. Indeed, Canadian scientists remain in the vanguard of research on diabetes, a disease that is the third-ranking killer in North America, after heart disease and cancer. Recently, in fact, researchers at University Hospital in London, Ont., disclosed that they were preparing to implant live, insulinsecreting cells from pigs in volunteer diabetics. That would mark the world’s first animal-to-human transplant of that type. According to Dr.

Calvin Stiller, chief of the hospital’s multiorgan transplant service, that experiment could occur as early as next fall.

But Stiller and other scientists in the field stress that they still have not found a cure for Type 1, or insulin-dependent, diabetes— the most severe form of the disease. About 4,000 Canadians develop Type 1 diabetes each year—joining 120,000 other sufferers in the country who require daily injections of insulin to replace a hormone that their bodies can no longer produce or assimilate naturally. Still, many researchers say that work performed within the past two years alone has led to a greater understanding of diabetes—and increased their hopes of eventually conquering it. At the University of Calgary, microbiologist Ji-Won Yoon is developing vaccines to combat viruses that he said he believes initiate Type 1 diabetes. According to one theory, those viruses cause the body’s immune system to attack the pancreatic cells producing the insulin that regulates blood sugar levels. And in conjunction with European scientists, Stiller says that he has obtained promising results in clinical trials of cyclosporine, a powerful drug that is frequently used in transplant operations to prevent the body from rejecting foreign tissue.

Researchers have found that small, daily doses of cyclosporine frequently prevent the immune system from at-

tacking insulin-producing cells. Indeed, recent European and Canadian tests of more than 200 newly diagnosed diabetics have shown that the drug caused a remission in diabetes in 40 per cent of the participants—allowing them to forgo as many as four painful injections of insulin daily. But cyclosporine’s extreme toxicity is a drawback: even the small doses that are routinely administered in diabetes-control tests

cause unwanted growth of hair and gum tissue in most patients.

Still, such specialists as Dr. John Dupré, a professor of medicine at London’s University of Western Ontario, say that cyclosporine—or a similar, less toxic substance—could represent the best chance of an injection-free future for newly diagnosed diabetics. And he and others note that diabetes specialists in France now are quick to begin cyclosporine treatments of new rrype 1 patients in an attempt to prevent the destruction of insulin-producing cells called the islets of Langerhans.

Meanwhile, researchers at Torontobased Connaught Laboratories Ltd., University of Toronto physiologist Dr. Anthony Sun and Stiller’s team say that they hope to determine if transplanted animal cells can supply insuliq for diabetics—duplicating a feat that the scientists have accomplished in trials with laboratory rats. The initial goal of the experiments involving diabetic volunteers, however, is simply to determine

whether clusters of pancreatic cells from pigs are capable of surviving in the human body. To that end, Sun has developed a prototype, a gelatin-like capsule that encloses one or two clusters, each one containing about 5,000 insulin-producing cells. The porous membrane of that capsule will have two functions: to govern blood sugar levels by allowing an immediate release of insulin and, at the same time, shield the cells from attack by the body’s immune system. Many researchers and diabetics alike say that they are hopeful of reaching the experiment’s ultimate objective—providing diabetics with a supply of insulin from animal cells. If successful, that technique would offer sufferers greater protection from such complications of diabetes as blindness and heart disease. But Sun stressed that isolating insulin-producing cells in pig pancreases remains a difficult, time-consuming procedure. Declared Sun: “We have done a lot of work in this area at Connaught but we are not that confident about the process yet.” In their quest for a new diabetes treatment—a goal that could take several years to reach, Canadian researchers plan to inject the encapsulated

pig cells into an abdominal cavity membrane near the liver. That technique will allow the organ to absorb the insulin secretions before releasing them into the bloodstream. Meanwhile, daily injections remain a necessary survival routine for insulin-dependent diabetics. But the promising results of cyclosporine trials and the pending animal-cell transplants indicate that there are growing hopes for eventual victory over the disease.

MALCOLM GRAY

MAXINE McDOWALL

in Toronto