How Similar Are Canine and Human Diabetes?

Both dogs and humans are susceptible to developing diabetes. Diabetes in dogs presents itself similarly to type 1 diabetes in humans. While the disease appears similar on the surface there are some key differences between canine and human diabetes.

Researchers have been examining pancreatic tissue from 23 diabetic dogs and 17 unaffected dogs. The pancreas contains islet cells which contain beta cells. Beta cells produce insulin which turns sugar into useable energy for the body. Diabetic dogs and humans with type 1 diabetes all show a loss in beta cells and therefore their bodies cannot produce enough insulin. The diseases still appear quite similar however Dr. Jake Kushner (Chief of Pediatric Diabetes and Endocrinology at Baylor College of Medicine) said "There were some real surprises. Dogs had very few islets. In man and mouse, there are often residual islets, but these dogs had very little left. It suggests some sort of really aggressive process destroying those cells."

The method in which these islets are destroyed are not yet known. The researchers did not see evidence of inflammation or autoimmune problems. Type 1 diabetes in humans is caused by the immune system attacking islet cells. Kushner believes that the dogs included in the study may have been in such an advanced state of disease that an autoimmune attack was no longer occurring.

Dr. Kushner found that the composition of islet cells is different in dogs than in humans. In healthy humans islet cells consist of approximately 50% of beta cells compared to 80% in dogs. It is possible that this is why diabetic dogs are typically older since they have more cells to die. Dr. Kushner said, "Dogs get diabetes at a pretty significant rate, about the same rate that humans get type 1 diabetes. But, they get it later in life." Chief of Internal Medicine at the University of Pennsylvania School of Veterinary Medicine, Dr. Rebecca Hess said, "If they're starting with a larger supply of beta cells, it may give them a longer time before they develop the disease."

Montefiore Medical Center’s Director of Clinical Diabetes, Dr. Joel Zonszein said, "Although diabetes in the dog resembles type 1 in humans, they don't have the same inflammatory process we see in type 1 in humans. In dogs, we don't understand what triggers it yet. And, the anatomy of the islets is completely different in dogs. This is a nice study, but we still have to learn more."

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Have We Found the Fountain of Youth?

Researchers at the University of Washington Medical Center are searching for a way to increase canine lifespans. The dogs will ideally live 1 to 4 years longer. The drug, Rapamycin, is being tested on 32 elderly dogs in a clinical trial. Rapamycin has already been shown to extend the lifespan of worms, fruit flies, yeast, and mice with few side effects. Rapamycin interacts with a protein that is involved in cell growth. It is unknown how the drug increases lifespan. It is possible that Rapamycin slows the ageing process or that it prevents age-related diseases. It is also possible that the drug can prevent cancer.

Rapamycin is now being tested on dogs. To discover if the drug has an effect on humans would take decades whereas it would only take several years to see a difference in dogs. The dogs are monitored to determine if the progression of old age diseases is delayed.

Professor of Pathology, Dr. Matt Kaeberlein said, "We're not turning back time, what we're really trying to do is slow the aging process. Dogs also get a lot of the same diseases as people do when they get older, dogs get cancer, they get heart disease, they get dementia. What we'll learn from this study will be important in applying these discoveries to human aging, but the primary goal for me personally is to improve the quality of life for pet dogs.”

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