Diabetes Mellitus

Diabetes Mellitus is a disease manifesting as excessive production of urine and inability to move sugar from the blood stream into body cells.  A hormone called insulin transports sugar from an animal's blood stream into cells for use in the production of energy.  Normally the sugar and fats from meals are transported to the liver cells where it is used for cell energy or stored for future use. The absence of insulin means the sugar stays in the blood stream and is filtered through the kidneys pulling excess water with it and causing excessive urination and thirst. 
 People can experience type I and type II diabetes. Type I diabetes occurs when the cells that make insulin are damaged or destroyed- this more often occurs in younger people.  Type II diabetes is an “exhaustion” of the insulin producing cells and often is secondary to inadequate exercise and excessive carbohydrate consumption.  Type II diabetes can often be reversed by lifestyle changes and helping decrease the carb burden. Normal human blood sugar runs from about 80 to 100 mg/dL and diabetics may have blood sugars up into the 250 to 400-mg/dL range and higher. 

Veterinary medicine sees both type I and type II diabetes with the majority of dogs experiencing the former and cats the latter.  Often cats have either a breed predisposition toward reduced glucose tolerance or a history of obesity and relatively high carbohydrate diets.  Luckily with cats we can often reverse the diabetes using a high protein diet, insulin therapy and evaluating medication history.  This should be done carefully with the guidance of a veterinarian.  Insulin therapy allows the exhausted pancreatic cells to have a rest and bring the toxic levels of sugar down. However a concern that injected insulin may bring the blood sugar too low exists, so blood sugar should be closely monitored.  Many cats who will eat high protein diets and bring their sugars consistently under 180 mg/dl can reverse the syndrome.  In people newer medications called GLP-1 (glucagon like peptide 1) agonists are helping type II diabetics live without insulin and maintain healthier weights.  Early studies in cats are promising but not yet clinically available. 

Dogs generally get type I diabetes with destruction of their insulin secreting (islet) cells in their pancreas and they are insulin dependent.  Human insulin types such as NPH, glargine or levemir are used in dogs currently. The insulin in these is a human recombinant protein hormone.  Historically diabetes was treated with insulin harvested from pigs or cows.  There are veterinary insulin types such as PZI or Vetsulin, which can work for dogs but become expensive for larger dogs.  Some dogs may develop diabetes after an insult to their pancreatic cells such as cancer or inflammation (pancreatitis). Because of a particular enzyme present in the ocular lenses of dogs, they may develop cataracts secondary to diabetes mellitus.  Originally we thought control of the diabetes would help slow or prevent cataracts, but it has become evident that some dogs develop them rapidly and others may not develop them for years.  Dogs who have a quality of life compromise resulting from cataracts can go through surgery to remove them.   I usually recommend consultation with a veterinary ophthalmologist after the diagnosis to help guide owners on the expected progress of the cataracts.  Some feel the administration of grape seed extract, as an anti-oxidant will slow the progression of cataracts so this is often prescribed.
If owners are willing to administer injections and carefully monitor diet, urination and energy level, most pets with diabetes mellitus can maintain a good quality of life. In cats that have a reversible version of the disease, monitoring diet by maximizing protein content, lowering carbs and increasing fats helps maintain their sugar balance.  Because high protein diet is a little more challenging for the kidneys (particularly in aging animals) these cats should have kidney values monitored closely.  Dogs do well as long as their overall pancreatic function is not compromised and their diet requirements are monitored. Higher protein and fiber with lower fat are the recommendations for canine diabetic patients. 

If you have a diabetic pet – there are many Internet chat sites where people share ideas and experiences about their pets, as well as means to track blood sugar levels for those owners who wish to learn how to measure blood sugars at home.  I find being able to measure blood sugar at home provides peace of mind and helpful information for both pet owners and veterinarians. It is very important though to always consult with your veterinarian before changing insulin dosage. Insulin is a powerful drug that may cause a dangerous drop in blood sugar, possibly leading to seizures or coma.