Diabetes risks — and treatment — in pets
By Sarah Netherton/University of Illinois College of Veterinary Medicine
Diabetes affects 347 million people worldwide, according to the World Health Organization. Unfortunately, it also is a common health problem for pets.
Margarethe Hoenig, a veterinarian at the UI College of Veterinary Medicine in Urbana, is one of the foremost researchers in diabetes and obesity in dogs and cats.
Animals with diabetes have high levels of blood sugar because their bodies are not able to produce or to properly use insulin, a hormone produced in the pancreas. The cells in the body need insulin to acquire sugar (glucose) from the bloodstream and use it for energy.
"Insulin is the hormone that enables the cell to access glucose for energy. Without insulin, the cell breaks down stored glycogen, fat and protein for energy," Hoenig said. "As a result, glucose is unavailable for use by the body and is excreted in urine, and the animal rapidly loses weight."
The clinical signs of diabetes include increased drinking and urination and weight loss despite an increased food intake.
Dog breeds that appear predisposed to diabetes include samoyeds, miniature schnauzers, miniature poodles, pugs and toy poodles. Breeds at low risk to develop the disease include German shepherds, boxers and American pit bulls. In cats, males are at greater risk of diabetes than are females.
Hoenig said that while the classifications used to characterize diabetes in human medicine have similarities to the disease in dogs and cats, many aspects are different.
"Type 1 diabetes mellitus in humans is marked by autoimmune destruction of beta cells, the cells that store and release insulin," she said. "This is common in dogs as well. However, while Type 1 diabetes has also been called 'juvenile diabetes' because it arises early in life in people, this form of the disease occurs mostly in older dogs. Similar to Type 1 human diabetics, dogs with diabetes require daily insulin injections to survive.
"Diabetes in cats, which also arises in older animals, is characterized by the presence of amyloid, an insoluble fibrous protein that is the hallmark of Type 2 diabetes."
Whereas people with Type 2 diabetes are treated with non-insulin oral drugs, these medications are not used for cats. Metformin, for example, has not been shown effective in cats, and glipizide and glyburide have been shown to help only a small percentage of cats. Pioglitazone has not been tested in diabetic cats. Therefore, most cats are treated with insulin.
"Our research has recently shown that many of the newly diagnosed diabetic cats, unlike most Type 2 diabetic people, actually have very low blood insulin concentrations. Therefore, daily insulin injections would indeed be the best treatment," Hoenig said.
There are different kinds of insulin on the market for use in dogs and cats. Veterinarians determine which preparation and injection regimen works best for a particular patient.
"The prevalence of diabetes mellitus is increasing in both dogs and cats, probably due to an increase in obesity," Hoenig said. "However, only in cats has obesity been clearly identified as a major risk factor for diabetes. It is important to note that weight loss reverses obesity-induced insulin resistance."
While it has long been thought that obesity is not a risk factor for diabetes in dogs, recent data show an increase in canine obesity of 37 percent between 2007 and 2012 and a 32 percent increase in canine diabetes over the same period. This strongly suggests that obesity also needs to be considered a risk factor in dogs.
Hoenig said the most important way to lower the incidence of diabetes in cats is to educate owners about controlling caloric intake in their pets. Most owners — even those with overweight, obese or diabetic cats — make food available to their cats at all times, which contributes to overeating and overweight.
"I think a healthy lifestyle is important not only for humans but also for pets. Exercise, a balanced nutritional intake and maintaining normal body weight are important aspects of a healthy lifestyle. Veterinarians have a huge task to educate their clients that ad libitum, or 'free,' feeding is not good for dogs or cats," she said.
An archive of pet columns from the UI College of Veterinary Medicine is available at http://vetmed.illinois.edu/petcolumns/. Requests for reprints of this article may be directed to Chris Beuoy, firstname.lastname@example.org.