Diabetes in dogs is usually a multifactor medical condition, characterized by high blood sugar levels (hyperglycemia) resulting from inadequate or totally absent secretion of insulin, the hormone produced and secreted by the beta cells of the pancreas which is responsible for the control of blood glucose levels, as well as for sugar uptake and use by body cells.
Hyperglycemia in dogs occurs when blood sugar (glucose) levels are higher than 130 mg/dl, although symptoms and signs appear only when a critical level of 180-220 mg/dl is reached. These are characterized by glycosuria (presence of glucose in the urine, which is normally glucose-free), polyuria (excessive production and passage of urine), polydipsia (excessive thirst) and polyfagia (excessive appetite), as well as by a number of serious metabolic alterations caused by the inability of body cells to take up and use blood glucose, which is the main fuel for the body in normal conditions. Among these metabolic complications, diabetic ketoacidosis is by far the most serious and life-threatening. This condition is characterized by a severe lowering of blood pH due to the excessive production of acids, the so called ketonic bodies, which are by-product of fat metabolism (in fact, body fat degradation in diabetic dogs increases in order to generate molecules that can replace glucose as the primary energy source for body cells).
The most frequent form of diabetes in dogs is the insulin-dependent diabetes. This means that affected dogs need to take exogenous insulin for the rest of their life to control their blood glucose levels after the irreversible destruction and functional loss of pancreas beta cells has occurred. The factors involved in the development of diabetes in dogs are many and unfortunately not all of them are clearly understood. Breed and sex predisposition, infections, drugs and diseases that antagonize the action of insulin, intestinal autoimmune diseases and pancreatitis are considered as triggering factors. At the diagnosis, most dogs are between 4-14 years of age, with a peak of prevalence at 7-9 years of age. Female dogs are affected about twice as frequently as male dogs. As regards breed predisposition, it has been observed that Pulik, Cairn Terrier and miniature Pinsher are the breeds at most risk for diabetes. Poodles, Basset Hounds, miniature Schnauzers and Beagles are frequently affected, too. On the contrary, the risk of diabetes seems to be relatively low in many common breeds of dog, such as Cocker Spaniel, German Shepherd, Collie, Pekinese, Rottweiler and Boxer.
Diagnosing Diabetes in Dogs
The diagnosis of diabetes needs to be made by a veterinarian. Dog owners may suspect diabetes if their pet shows increased urination, increased appetite and thirst, and sometimes weight loss (despite of increased appetite). However it should be underlined that these signs are not necessarily due to diabetes, since they are common to many other diseases. The definitive diagnosis is based on the demonstration of persistent fasting hyperglycemia combined with glycosuria.
The primary therapeutic goal in the management of diabetes is the removal of symptoms secondary to hyperglycemia and glycosuria. The persistence of clinical signs (increased urination, appetite and thirst) as well as the development of chronic complications (such as ketoacidosis, fatty liver, pancreatitis, cataract, bacterial infections) are directly related to the severity and duration of hyperglycemia. That is why treating diabetes in dogs is based on a tight control of hyperglycemia, which can help reduce clinical signs and prevent complications. This can be carry out by administering proper amounts of insulin, feeding the dog with the correct diet, getting the dog to do an adequate amount of exercise, and, when necessary, treating any concomitant conditions (inflammatory, infective and hormonal disorders). Which therapeutic regimen to choose depends partly on the number of functionally active beta cells in the pancreas and, of course, on the response of individual dogs to treatment.
Regardless of the type and severity of diabetes, affected dogs should receive a proper dietetic therapy in order to correct obesity (when present), maintain constant frequency and caloric content of meals and provide a diet which reduces blood glucose fluctuations occurring shortly after eating. A high-fiber diet can meet all these requirements. The current high-fiber diets available on the market for dogs contain mainly insoluble fiber (e.g., lignin, cellulose). However the actual content of fiber varies among different products and brands, ranging from 3 to 25 percent of the dry matter. In general, the products that most likely reduce body weight and improve blood glucose control are those with a higher fiber content. It is important to remember that high-fiber diets are not without complications. The most common include increased defecation or constipation and a refusal to eat these diets by the dog. If constipation is a problem, it is possible to add some soluble fiber to the diet, for example psyllium powder. To avoid that dogs refuse to eat these dietetic products, it may be recommended to gradually introduce the new diet and, whenever possible, try to alternate different types of high-fiber diets.
Diabetic dogs who are underweight should not be feed with high-fiber diets, due to their low caloric content. In these cases it is preferable to use insulin therapy in order to restore normal blood glucose levels, while administering a maintenance diet with a higher caloric density and a lower fiber content. Once a normal body weight is achieved, it will be possible to gradually replace the previous diet with a diet with a higher fiber content.
Treating diabetes in dogs involves exercise, as well. Exercise plays an important role in maintaining blood glucose control: it helps dogs lose weight and has a blood glucose lowering effect. The latter is likely due to the increased mobilization of administered insulin from its injection site to general circulation and then muscles. In presence of insulin, muscles can take up more glucose from the blood to fuel their work during exercise, thereby helping lower blood glucose levels. However it is important not to overexercise diabetic dogs, since the development of hypoglycemia is a risk. In case of dogs undergoing occasional intense exercise (such as hunting dogs during hunting season), the dose of insulin should be reduced in the days of increased physical activity. In all other cases, diabetic dogs should do daily slight-moderate exercise, preferably always at the same time of the day.
A final mention should be made of insulin therapy, which is the cornerstone for treating diabetes in dogs. Although the dose and dosing frequency of insulin is determined by the veterinarian, dog owners play a crucial role in the success of insulin therapy in their dog. Insulin is in fact a lifelong therapy and the drug has to be administered at home once or twice each day by the owner himself. Therefore it is important that owners strictly follow the instruction received by the veterinarian about dose, dose interval, as well as frequency and time of dosing. In general, the initial therapy is based on the administration of insulin once a day (preferably in the morning), through an injection under the skin. The therapeutic protocol is then adjusted depending on the response of the dog to the initial therapy. In general, it takes about a month before the veterinarian establishes the proper definitive protocol. During this time, the dog should be taken to the veterinarian at least once a week in order to assess his response to the treatment and make the appropriate changes to protocol, if needed. The cooperation of the owner in this process is crucial, since his subjective impressions about symptoms shown by his own dog (polyuria, polydipsia and polyfagia) are essential to make a proper assessment of the dog’s response to treatment.
By following the therapeutic regimen summarized above, it will be possible to reach a good control of blood glucose levels, which is the goal of diabetes therapy, with resulting resolution of diabetes clinical symptoms and prevention of chronic life-threatening complications.