Diabetes

Diabetes mellitus (or simply, diabetes), which often develops in childhood, is a disease caused by the body's failure to produce, or effectively use, adequate amounts of a crucial hormone called insulin. Insulin is normally produced in the pancreas and is necessary for the absorption of glucose into cells for energy needs. Symptoms arise after the body's immune system, for unknown reasons, attacks and destroys most of the insulin-producing islet cells in the pancreas.

Type-l, or juvenile diabetes, is found in children and is the harshest form of the disease; it can kill within a short time if left untreated. In older patients, diabetes may go undetected for a long period. It is a serious chronic illness with complications such as blindness, kidney failure, loss of limbs, heart disease or stroke occurring in patients both young and old.

About 1.8 million Canadians and 11 million Americans are afflicted with diabetes, which is the third leading cause of death by disease. Each year, almost 300,000 people die from diabetes or its complications, and more than 5,000 people become blind from this disease. Until 20 years ago, death of the fetus was not uncommon in pregnant diabetic women.

Insulin

In 1921, Frederick Banting and Charles Best in Canada first isolated a secretion called insulin from the pancreas of dogs, who suffer naturally from diabetes. Best later extracted insulin from cow pancreas, purified it, filtered it, then successfully tested it on diabetic dogs.

A year later, Banting and Best injected each other with insulin to test for side effects. They found no side effects; and the next day, a desperately-ill 14-year-old boy became the first diabetic to receive insulin, a treatment which is still in use nearly eighty years later.

Today, insulin can be manufactured using genetic engineering techniques, in which bacteria (Escherichia coli) are made to produce human insulin. The insulin isolated in this fashion is regarded as 100% pure and produces few allergic reactions.

Insulin is not a cure for diabetes; it is simply a way of controlling the disease. Biomedical researchers are still searching for ways to improve diabetes treatment and to eradicate the disease.

Laboratory animals must still be used to test the safety of new batches of insulin. And animals like the dog, rat and pig still contribute to our expanding knowledge of this disease which inhibits the quality of life for so many people.

Today, approximately 90-95% of all diabetes research focuses on understanding insulin synthesis, storage, secretion, circulation, binding and action. All of these areas of investigation use animal models.

One important development as a result of this research has been recombinant DNA-synthesized human insulin, which is now available for therapeutic use by diabetics.

This new technology not only allows diabetics to benefit from the availability of human insulin, it also saves animal lives by reducing the number of animals that must be used.

Many insulin-requiring diabetic patients appear to have a better degree of control using continuous insulin administration provided by small pumps. Using dog and rabbit models, external and internal (implantable) insulin pumps have been designed which monitor insulin levels and provide continuous appropriate doses. Many of these are now available for human use, but research is still necessary to improve their design.

One promising approach to curing diabetes is transplantation of functioning islet cells into patients. Currently, this advance is being developed further for possible human applications. If successful, this method could have vital implications for other forms of organ transplantation.

Although insulin therapy and other treatments for diabetes now prevent deaths from the direct effects of diabetes, insulin injections unfortunately do not prevent the complications of insulin-dependent diabetes, including blindness, kidney failure and vascular disease. In addition, the origin, physiology and prevention of diabetes are still unsolved problems in biomedical research. With the help of laboratory animal models such as rodents, rabbits and dogs, biomedical researchers will continue to make advances which will one day answer these fundamental questions.