Feline Diabetes, Part 1

Anyone who has read this blog for any length of time knows that nothing annoys me more than the conflating of feline and canine diabetes — sometimes by medical professionals. I’ve posted about canine diabetes, which is akin to Type 1  in humans, several times because it’s an important part of my life with Frankie. But — surprise — I’ve also written about the feline version of the disease for Catnip, the newsletter put out by the Cummings School of Veterinary Medicine at Tufts University.

I even got to interview one of my favorite fellow bloggers for the story: Melissa Freer, better known as Mel of No Dog About It. She talked to me about Sebastian, her secret binger of a cat. You didn’t know we were both so multi-species savvy, did you?

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Diabetes mellitus is on the rise among cats in the United States according to a study of clinics nationwide, an increase that has been correlated with a rise in obesity. Although it’s hard to draw definitive conclusions from the results of the survey, there’s no question that feline weight control is a key to preventing the onset of this chronic disease.

Orla Mahony, ACVIM, ECVIM, a specialist in small animal endocrinology at Cummings School of Veterinary Medicine at Tufts University, says,  “I have concerns about overinterpreting the results of any survey without having sufficient data to explore. We don’t know that the incidence [of diabetes mellitus] has actually increased, or if there is simply better recording and monitoring, or more testing.” But, she cautions, “There’s no question that you want to prevent your cat from getting fat to avoid the disease.”

What is Diabetes Mellitus?

Diabetes mellitus is characterized by the body’s inability to produce or to utilize insulin, a hormone that allows glucose (sugar) to enter cells and be converted to energy. When the disease isn’t controlled, glucose and fats remain in the blood, eventually damaging vital organs. As in most non-technical articles, the term “diabetes” here refers to diabetes mellitus.

There are two main categories of diabetes in humans. Type 1 is, in essence, an autoimmune disease that causes the body to attack and destroy insulin-producing beta cells in the pancreas. It’s manageable with injections of insulin, but it’s not reversible.

In the much more common type 2, typically seen in overweight adults and, increasingly, among obese children, the pancreas still produces insulin, but either does not produce enough or the body is resistant to the insulin it does produce. If it hasn’t progressed to a dangerous stage, type 2 diabetes can often be controlled by diet and oral medications.

Type 2 is the variety to which cats are usually subject but, according to Dr. Mahony, by the time most cats are diagnosed, the disease is fairly far advanced, which means that they are likely to be insulin dependent for the rest of their lives.

Common Causes for Feline Diabetes

Many of the same factors that come into play in human diabetes cause feline diabetes too: obesity, inappropriate diet, and insufficient exercise.

Melissa Freer of Eagan, Minnesota, first noticed signs of diabetes in her cat, Sebastian, after he had put on weight. “I started traveling on business more and I let my two cats eat from a cat feeder while I was away,” she says. One of her cats, Nick, just ate until he was full but Sebastian loved his food. Freer says, “I didn’t realize until he was already overweight that he would just sit in front of the feeder and binge.”

But just as recent research points to the possibility of a genetic basis for a predisposition towards obesity and diabetes in humans, a small-scale study in the United Kingdom suggested that this may also be the case for cats.

According to Dr. Mahoney, the researchers identified a genetic mutation that was more likely to turn up in domestic short-haired cats with diabetes than in those that didn’t have the disease. “Up until now, we were more interested in a cat’s lifestyle issues, that the cat was obese,” she says. “This was the first time the role of genetics was studied.”

An extended use of steroids or cortisone-type drugs can also cause insulin resistance in cats. Dr. Mahony says, “We warn owners of any cat that we have on long-term steroids that diabetes is a risk, and we try to test carefully to make sure that doesn’t happen.”

Chronic pancreatitis and other endocrine diseases such as hyperthyroidism and Cushing’s disease are considered to be contributing factors to diabetes too.

But it’s difficult to know which came first, the other endocrine disorders or the diabetes, and obesity is still primarily responsible, according to Dr. Mahoney. “I tell clients, the moment they neuter their animal, the diet begins right there,” she says. Although she recommends neutering for other reasons, including population control, Dr. Mahoney adds, “It is a double whammy. You have a lower metabolic rate and an increased appetite.”

Typical Symptoms of Feline Diabetes

The most prominent early signs of feline diabetes are an increase in drinking and urination. Some cats may also experience vomiting.

Since animals with diabetes lose weight and muscle mass  — the body is breaking down stores of fat and protein in an attempt to create glucose — a cat suffering from this condition may become weak. Cats are particularly prone to a disorder known as neuropathy, which causes weakness in the back legs. In fact, it’s this symptom that often alerts owners to the fact that there is a problem.

Other warning signs that may be exhibited by a diabetic cat include lethargy, depression, and an unkempt coat. This last is not well known as a sign, but it was the sole indicator for Freer that something was wrong with her cat, Sebastian.

“He started getting clumped fur near the base of his tail,” Freer says, “and getting kind of dandruffy. I couldn’t figure out what was wrong.” She told a friend who had a diabetic cat about Sebastian’s mysterious symptoms, and the friend said her cat had manifested the same ones before being diagnosed with the disease. Freer’s vet confirmed that this was Sebastian’s problem. “Sebastian never displayed any other signs of diabetes, no increased urination or weight loss, for the rest of his life,” Freer says.

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Stay tuned for part 2 to learn how cats — including Sebastian — are stabilized and treated for diabetes.