Visiting Vet: Diabetes in cats

I’m an old dog. There’s no denying it. I like to do things the way I have always done them. But I also like to keep current on the latest practices, and veterinary medicine is always changing. My feline friend Mahatma came to see me recently. Five years ago we discovered that Matty, as I call him for short, was diabetic. His blood glucose was elevated and he was losing weight. In order to understand what happened next, let’s review diabetes mellitus.

Diabetes is a disease that manifests differently in different species. Today we will just talk about cats. Normal feline glucose metabolism goes like this: Matty eats food. His gastrointestinal tract digests it into simpler molecules. Glucose (sugar) gets absorbed into his bloodstream. As his blood sugar rises, Matty’s pancreas responds and secretes insulin. Insulin is like an Uber whose job it is to transport sugar molecules out of the blood into the cells where the glucose fuels metabolism.

In diabetic cats, the pancreas gets tired, and stops producing enough insulin. Blood sugar levels stay higher than they should be. The cells do not get enough glucose transported into their engines. Matty gets extra-hungry, because his cells are underfed. Matty drinks excessive water, because elevated blood sugar makes him thirsty. Because he’s drinking more water, he urinates excessively. Because his body isn’t able to utilize the energy from his food correctly, he loses weight.

At first, Mahatma was one of the lucky cats. We put him on a high-protein, low-carbohydrate food designed especially for diabetic kitties. By improving his diet, we reduced the stress on Matty’s pancreas, which was able to recover and start producing enough insulin. His blood glucose levels dropped to normal. His weight stabilized. This is essentially equivalent to when people with Type II diabetes control their disease with lifestyle changes. Cut out all those sweets, add exercise, lose weight. That may be all a body needs.

But not always. Just like people with Type II diabetes may need a variety of medications, or even insulin injections, the same is true for kitties. After four years of maintaining with just dietary adjustments, Matty’s diabetes got worse. He began losing weight, and his blood sugar was climbing. Left untreated, diabetes is a life-threatening disease. We had to do more.

For most of my 44 years in practice, treating diabetes in cats was fairly straightforward. If it couldn’t be controlled with diet and weight loss, we gave them insulin injections. Usually twice a day. Sure, there have been some tweaks in the protocols. Different types of insulin. Different diets. Different ways of monitoring. But overall, protocols were similar. One nice thing is that, unlike diabetic dogs, who are always insulin-dependent, some kitties actually go into remission. In other words, giving insulin injections sometimes allows the pancreas to heal and recover enough that it starts functioning better. As many as half of all diabetic cats, if treated early with a specific type of insulin called glargine, may eventually be able to discontinue their insulin shots. The remission may be temporary, but in some cases can be permanent.

Insulin therapy is my version of an old dog fetching a tennis ball. It’s a familiar trick I know how to do. But now we have new options. Sodium-glucose cotransporter 2 (SGLT2) inhibitors. That’s a mouthful. If you’ve seen those annoying commercials for Jardiance on television, that’s a human SGLT2 inhibitor medication. There are two SGLT2 inhibitor drugs approved for use in cats, Bexacat, a tablet made by Elanco, and Senvelgo, a liquid made by Boehringer Ingelheim. These drugs prevent the kidneys from reabsorbing glucose. More glucose is excreted in the urine, thus lowering blood sugar levels. Lower blood sugar levels reduces stress on the pancreas, and hopefully allows it to recover and start secreting adequate amounts of insulin again. No injections needed!

Sounds great, right? Except … there are some risks and downsides. First, it assumes Mahatma’s pancreas still has the ability to produce insulin. This is not always true. Some diabetic cats (like all diabetic dogs, and people with Type 1 diabetes) just can’t produce any insulin. They are what we call “insulin-dependent.” Bexacat and Senvelgo will not work for these cats. Unfortunately, there is currently no way to know in advance if Mahatma is one of those cats. Secondly, cats taking SGLT2 inhibitors are at risk for a very serious side effect called diabetic ketoacidosis (DKA). If the pancreas doesn’t rally sufficiently, the body will start to break down fat for energy. This creates ketones, a substance that the body can use as an alternative fuel source, but a process that can also lead to severe imbalances in electrolytes levels and acid-base regulation, in addition to the already elevated blood sugar. Cats with DKA become extremely sick. It is a life-threatening syndrome requiring round-the-clock care and monitoring at an emergency specialty hospital.

Mahatma’s family is hesitant about learning to give insulin injections. I can understand that, but I have never used Bexacat or Senvelgo in a patient. So this week I have been doing a deep dive into learning about these new treatment options for certain cases of feline diabetes. We are not sure yet if Mahatma is a good candidate, but we are starting preliminary testing and discussing all the pros and cons. If he qualifies for SGLT2 inhibitors based on the initial screening results, and his owners decide they want to try one of these oral medications first, we will order the medication. We will also get a special blood ketone monitor, to be used either at my office or at the owners’ home, to monitor for DKA. If we try this new treatment, it will be essential to recheck him frequently at first, assessing glycemic control, monitoring body weight, testing blood ketone levels. And we will hope it works. If not, then this old dog can still fetch a tennis ball, going back to the trick I know well — using insulin.