In North America, one of the up and coming disease “epidemics” to be noted in people is diabetes (diabetes mellitus). This is a disease that most often affects obese, middle-aged patients. Coincidently, the same phenomenon can be found in our domestic cats, with the number of diabetic cats being diagnosed increasing every year. Why the sudden increase in diabetic cats? It’s likely in part due to the North American lifestyle – more is better.
Insulin is a hormone that is secreted by specialized cells in the pancreas. Insulin plays many roles in the body, where one of its main tasks is to facilitate the uptake of glucose (sugar), which is needed for energy, into cells.
Think of the cells in the body as the penthouse suite in a building, and insulin is the doorman that operates the elevator.
Glucose is the person that needs to get to the penthouse, and the only way to do it is if the doorman will press the button on the elevator. If the doorman is on holidays, there is no one to operate the elevator, and no one can get to the penthouse.
Diabetes mellitus in animals is divided into three categories, known simply as Type 1, Type 2, and Type 3. Each varies in cause and as a result, the treatment for each is different. Type 1 diabetes mellitus is often referred to as insulin-dependent diabetes mellitus (IDDM), it is most often observed in dogs. These animals do not produce enough insulin to assist glucose into the cells. They are also unable to prevent the liver from utilizing other sources of energy and producing harmful by-products known as ketones. This type of diabetes can be managed by giving insulin injections at regular intervals.
Type 2 diabetes mellitus is often referred to as non-insulin-dependent diabetes mellitus (NIDDM), and is most often observed in cats. In this case, the amount of insulin being secreted by the pancreas is sufficient to prevent the liver from producing ketones, but not enough to prevent an increase in blood sugar. Often, the tissues in the body that need glucose for energy become “resistant” to insulin, meaning that even increased levels of insulin do not encourage the cells to take up glucose. Obesity, a problem affecting many of our domestic animals, contributes to tissue insulin resistance, which is why overweight cats are more likely to develop diabetes. In Type 2 diabetes, there can also be a component of impaired insulin secretion due to the deposition of a hard, waxy protein breakdown product, known as “amyloid” in the pancreas. Although most cats suffer from this type of diabetes, by the time they are diagnosed with the disease, they may have progressed to becoming insulin-dependent and require treatment.
Type 3 diabetes mellitus is also known as secondary diabetes, and is usually a consequence of another disease that produces insulin resistance. For example, many diseases affecting the body’s hormonal system can cause secondary diabetes, such as hyperthyroidism and pancreatitis.
The most classic sign of diabetes mellitus in the cat is an increase in water intake and urine output. The overload of glucose in the blood stream is relieved somewhat by loss into the urine, and the large amount of glucose in the urine draws water out of the body with it by osmosis. The loss of water in the body leads to dehydration, and animals compensate for this by drinking much more.
Another sign of diabetes mellitus is weight loss in spite of an increased appetite. The body needs glucose for energy and with insulin resistance it can’t seem to get enough, especially into the brain. At the same time, calories in the form of glucose are being lost into the urine. The brain feels that the body is hungry and so the cat’s appetite increases, but because the calories are being lost and not utilized, there is weight loss. Furthermore, insulin promotes the building of proteins from amino acids in the body. When there is not enough insulin, proteins break down (especially in muscle), and this also contributes to weight loss.
Cats are unique in that they do not form cataracts when affected with diabetes mellitus. However, they may have an abnormal posture where they are standing on their hocks instead of their toes (known as a plantigrade stance) or they may have chronic vomiting and diarrhea.
In theory, it should be easy to diagnosis diabetes mellitus by simply testing for increased blood sugar levels. Cats, however, are again unique in that when they are stressed, they can increase their blood sugar levels dramatically in a very short period of time (such as the time it would take your veterinarian to collect blood)! Testing for glucose in the urine is a more sensitive test for diabetes, although cats with renal disease can also have glucose leaking into their urine.
Ideally, your veterinarian will use a combination of tests to confirm whether or not your cat has diabetes mellitus. In addition to checking for increased glucose in the blood and urine, a test called serum fructosamine can be performed. Fructosamine is the product of the combination of glucose with amino acid residues of proteins in the blood. Since these proteins spend 2-3 weeks in circulation, they can provide information on the level of blood sugar over this period of time and definitively differentiating between diabetes mellitus and stress-related blood sugar elevation.
The treatment for diabetes mellitus can be unique for every cat. The first consideration is diet, where the goal is to bring the cat to an ideal body weight and to keep the blood glucose levels consistent. An obese cat should be fed 60-70% of its calculated caloric requirement to reduce its body weight over 2-4 months. An emaciated cat should be fed a high calorie diet until it reaches optimum weight. When an ideal body weight is reached, a high fibre diet is recommended because fibre slows glucose absorption from the gastrointestinal tract.
Exercise is an important part of weight control and reduces insulin resistance. Although it seems like a trivial task for an indoor cat, activity can be greatly increased by adding toys such as food dispensers that make your cat work for his meal.
Insulin treatment may be required for cats that have decreased insulin production and have become insulin-dependent. There are many different types of insulin products available and your veterinarian will prescribe an appropriate formulation for your cat. Insulin administration should be timed with meals so that maximum glucose uptake into the cells, is possible.
Monitoring your cat’s blood sugar at home is an important task that should be done regularly. Changes in appetite, weight, drinking, urinating, and overall attitude should be brought to the attention of your veterinarian. Regular blood glucose checks should be done by your veterinarian to ensure that the dose of insulin is ideal for your cat.
Complications – Diabetic Ketoacidosis
Occasionally, a cat with diabetes mellitus may progress to a disease known as diabetic ketoacidosis. In these animals, the decreased amount of insulin causes the liver to use other compounds as a source of energy instead of glucose. By-products of this energy production are compounds known as ketones, which when in large quantities in the blood can make a cat very ill. Signs of diabetic keotacidosis include depression, recumbency or a comatose state, vomiting, anorexia, dehydration, and/or yellow mucous membranes. If you notice any of these signs, it is important to bring your cat to your veterinarian or an emergency clinic immediately.
Life with a diabetic cat
Diabetes mellitus, with some patience and perseverance, is a manageable disease. It is important to continually communicate with your veterinarian to ensure that your cat’s treatment plan is appropriate, as insulin doses often need to be adjusted over time. With proper treatment and a long-term commitment, most cats can look forward to many wonderful years!
By Beverly Wong – Pets.ca writer