Visiting Veterinarian : When diabetes sneaks up on healthy Martha's Vineyard pets
Last September at Wilson's annual visit, I told his owner that this seven-year-old cat was significantly overweight. Okay, maybe I wasn't that tactful. Tipping the scales at 16-plus pounds, Wilson was a fat cat. I recommended a low-carbohydrate prescription diet called M/D. (That stands for Metabolic Diet, but we call it the "Catkins Diet.")
Four months later, Wilson had lost half a pound. It may not sound like much, but it's actually three percent of his original body weight. That's like a 200-pound person dropping six pounds. You might not win The Biggest Loser, but it's definitely progress.
"He's been stealing the dog food," his mom admitted. I advised restricting access to the dog chow and continuing portion-controlled M/D.
Fast forward to this year's visit. I barely recognized the svelte cat slinking out of the carrier. "Wilson sure has slimmed down," I commented while noticing that his owner had not purchased M/D all year. "What diet are you using?"
Well, it seems Wilson hadn't been on a reducing diet at all. With three cats and two dogs in the house it had just been too complicated. Nonetheless, Wilson now weighed a mere 12.5 pounds, though he was still voraciously sneaking dog chow and also drinking more water. "We'd better run tests," I ventured, knowing the most likely diagnosis was either hyperthyroidism or diabetes mellitus.
Diabetes. The incidence is on the rise in cats as well as people. In order to understand diabetes, let's start with a hypothetical normal cat. Let's call him Watson. Watson eats food. The food is digested in his gut. Nutrients are converted into glucose (a form of sugar), then absorbed into his blood. When Watson's blood sugar rises, his pancreas responds by secreting insulin. Insulin is the ferry which transports glucose from the blood into the cells. Without insulin, the sugar stays in the blood, and the cells go hungry.
Now, take Wilson. His blood tests were all fine except his blood glucose, which was four times normal, confirming the diagnosis of diabetes. His pancreas isn't making enough insulin. His cells are hungry. In fact, they are starving. No matter how much Wilson eats, without that insulin ferry, glucose can't get inside the cells. His body burns fat, and eventually muscle, in an attempt to feed itself. Wilson loses weight. The high blood sugar makes him drink and urinate more.
"Wilson's diabetic," I sighed, knowing his owner would have a good idea of what that meant. She already had a diabetic dog at home and had been giving insulin injections for years. I could see her quail at the thought of doing the same with a cat.
"Hold on," I said, reassuringly. "We should start Wilson on insulin, but there's a chance that might be temporary."
Let me explain briefly. Human diabetics are usually classified as Type 1 or 2. Type 1 are insulin-dependent. They must have daily insulin injections to survive. Type 2 can often control their disease with diet and exercise. Doggy diabetics are almost always insulin-dependent, but diabetic cats are often Type 2. Although the majority need lifelong insulin, some are only transiently diabetic and go into remission, especially with proper lifestyle changes.
Research suggests that starting newly diagnosed diabetic cats on low-carbohydrate food and insulin increases the odds of remission, and that a sustained-release insulin called glargine may be most effective in achieving this goal. Isn't all insulin the same? Nope. There are many types, each with its own speed of onset, duration of effect, peak and nadir times, and so on.
Every species, and every individual, responds differently. In our healthy cat, Watson, his pancreas constantly makes minute insulin adjustments in response to fluctuating blood sugar levels. For Wilson, we are trying to mimic this with just two injections daily. Choosing the right insulin for each patient is an art, but the current veterinary thinking is that for newly diagnosed cats, glargine maximizes their chances of remission.
So we've picked our insulin. Now what about diet? Studies have shown as many as 40 percent of newly diagnosed diabetic cats may eventually go into remission if fed a canned low-carbohydrate diet. Note the key words. Canned. It has to be canned. Low-carbohydrate. Some sources say under 12 percent carbs, but many specialists advise under 7 percent. Percent of what? Evaluating canned cat foods for carbohydrate content can be tricky. Many brands don't put this information on the labels. I always start with prescription diet Purina DM, which was one food used in those studies, though later I often switch cats to less expensive over-the-counter options.
Can we start with just dietary change and hold off on insulin? Well, we could, and occasionally that works, but chances for remission are improved by starting both insulin and diet right from the beginning.
Now we've picked our insulin and food. How do we monitor? If Wilson uses a litter box, there are products that can be sprinkled in to measure sugar in his urine. From this we can extrapolate his blood sugar levels. At first, he needs a weekly blood glucose curve. That means testing his blood every three to four hours throughout a 12-hour period. Some owners learn to do this at home with a portable device just as human diabetics do. It's not as hard as it sounds. A tiny blood sample is obtained by pricking the margin of Wilson's ear. The monitor does the rest automatically.
If we are lucky, Wilson's pancreas will respond to the dietary changes by beginning to recover normal function. Then we would slowly wean him off injections and see if his pancreas gradually geared up to the task of producing all the insulin his body needs. He should stay on a low carbohydrate diet forever. If Wilson doesn't go into remission, well, we'll cross that bridge if we come to it.
For now, I'm going with positive thinking and hoping for a sweet ending to Wilson's story.