Diabetic dog's pancreas (right) had a sharp loss ofinsulin-producing beta cells compared to non-diabetic dogs.

Little is understood about the underlying cause of diabetes in dogs. But a new study, conducted by researchers from the University of Pennsylvania and Baylor College of Medicine, has begun to fill in some of the details.

Using advanced imaging technology, researchers precisely quantified the dramatic loss of insulin-producing beta cells in dogs with the disease and compared it to the loss observed in people with Type 1 diabetes.

Despite important differences between the disease in dogs and humans, the study also identified key similarities that suggest investigating diabetes in dogs may yield valuable insights into treating humans.

The study was published June 9 in PLOS ONE.

Canine diabetes can be managed with insulin, similar to Type 1 diabetes in humans. But unlike the human version of the disease, dogs typically develop diabetes in middle or old age, while people with Type 1 diabetes are typically diagnosed during childhood. In addition, while Type 1 diabetes is known to be an autoimmune condition, researchers haven’t found conclusive evidence that the same is true in dogs.

To learn more about the factors contributing to canine diabetes, the researchers made use of a repository of donated tissue samples from dogs—23 with diabetes and 17 without—who had been treated at the University of Pennsylvania School of Veterinary Medicine’s Ryan Hospital. 

The team used robotic microscopes that can rapidly move around a slide taking images of pancreas tissue samples. The samples were analyzed by computer to determine the contents.

“In a larger view we could look at the entire cross-section of pancreas to determine how many islets there were and how big they were,” said Emily Shields, lead researcher for the study. “Then we could zoom in to differentiate beta cells, which produce insulin, from alpha cells, which produce glucagon.”

They found that beta cells dropped off 13-fold in diabetic dogs compared to non-diabetic animals. They also found that non-diabetic canine islets contained a large percentage of beta cells, comprising about 80% of endocrine cells. In contrast, beta cells comprise slightly more than 50% of endocrine cells in non-diabetic human islets.

The researchers noted this may mean that dogs need to lose more beta cells before experiencing symptoms of diabetes. The observation could explain why dogs develop a form of diabetes that is similar to Type 1 diabetes, but do so later in life, compared to humans.

They also identified features of the islets and pancreatic structures that were different in dogs than in humans.

“In sharp contrast to human diabetes, in which there are a lot of islets still present but none contains insulin, we found in dogs that only a few beta cells were present and the islets were incredibly small,” said Jake A. Kushner, MD, and senior author of the study.  

Photo courtesy of University of Pennsylvania School of Veterinary Medicine