In the first two parts of this series, we’ve covered Type 1 diabetes and Type 2 diabetes. This week, we look at three topics in diabetes research. First, we examine how biomedical research helps diabetic animals, then we discuss a new category of diabetes identified with the help of animal models, and finally we look at how research with animals has led to life-changing implantable medical devices for people living with diabetes.
As with diabetes in people, diabetes in animals used to be a death sentence. Today, thanks to many years of research with animal models, many species – from dogs to cats to people – are benefitting from insulin, which was discovered with the help of dogs. The benefits of research with animals extend to the animals, too. Gene therapy has cured Type 1 diabetes in dogs and researchers are working to solve diabetes-related conditions. Much like humans, animals experience side effects from their diabetes, such as obesity, and researchers are working on drugs to treat these conditions.
Not only are scientists are studying animal models of diabetes to develop new therapies, but they are also making discoveries that are changing our fundamental understanding of the disease. Recently, a new type of diabetes was discovered with the help of mice. Among the elderly there exists a type of diabetes that has long gone undiagnosed. Otherwise healthy older people are at risk of developing diabetes, seemingly without cause. Researchers at the Salk Gene Expression Laboratory have identified the cause – abnormally high levels of immune cells, called T regulatory cells. This newly-recognized form of the disease was found by studying several variants of mouse models – healthy mice, mice with obesity-related diabetes, and mice with age-related diabetes. The Salk team discovered more than the existence of this new type, they found a potential cure. When they blocked T regulatory cells from accumulating, the mice no longer developed diabetes in old age. They are now expanding their work to see if the same treatment will work in people.
Animal research is also changing the way that the 29 million Americans living with diabetes manage their condition on a daily basis. A number of companies have recently introduced implantable devices that do everything from replacing insulin injections to monitoring blood sugar levels to putting insulin-producing cells under the skin. Several research groups have unveiled implantable continuous glucose monitoring systems. These devices replace the several-times-a-day blood test that diabetics have relied on for years, taking the constant monitoring of blood sugar levels out of the equation. This is especially beneficial for children living with type 1 diabetes who can’t administer their own insulin. The technology for these implants was developed with the help of dogs, cats and pigs.
Researchers have been working on the ‘artificial pancreas’ since the 1980s, and this work has recently resulted in several groundbreaking implantable devices. An artificial pancreas works by replacing the insulin-producing function that diabetics lose when their immune system destroys their own pancreas. One approach combines blood sugar sensors with an insulin pump, constantly monitoring blood sugar levels and administering insulin automatically when needed. Development of a prototype device is followed by testing with animals before clinical trials in humans begin. In 2015, UCSB Professor Frank Doyle, of the University of California, Santa Barbara, participated in the popular Reddit ‘Ask Me Anything’ series, where he discussed his team’s 20 years of work developing an artificial pancreas. This approach builds on animal research going back to 1983, when rats were implanted with insulin minipumps.
Another form of artificial pancreas packages insulin-producing cells into an implantable capsule, which is surgically inserted under the patient’s skin. The insulin-producing cells are derived from embryonic stem cells, which are coaxed to develop into beta cells, the same pancreatic cells diabetics lack. The cells are packaged in a small capsule that protects them from the body’s immune system. The capsule is implanted beneath the skin where the new cells multiply and produce enough insulin that recipients no longer need to inject insulin or monitor their blood sugar levels. Earlier tests on mice confirmed the viability of the implant, which produced insulin over the entire lifespan of the mouse – about one year.
An implantable device (Courtesy MIT)
The discoveries discussed in this article are only a fraction of the advances that are being made possible by scientists working with animals. The advent of CRISPR means that researchers will have more precise animal models that will better mirror human diabetes, leading to faster and more amazing research that will have an effect for patients with diabetes today. If you know of any other interesting diabetes work being done with the help of animals, please mention it in the comments section and we will include it in an article update.