What is Diabetes?

Diabetes is a disorder that impacts the way the body uses energy (glucose). In a normal body, sugars in the foods your pet eats are broken down into glucose. That glucose is then circulated throughout the body where it is readily available as fuel to cells for all types of activities. Insulin is a hormone that is produced by the beta cells of the pancreas that helps break-down those sugars so that they can enter the cells and be used for energy. In a healthy body, the pancrease will automatically adjust insulin levels to the blood glucose level. In a diabetic, this process does not function as it should and blood sugar levels become elevated (a condition called hyperglycemia), leading to a variety of other health problems and therefore, must be regulated.

Although the blood glucose levels become elevated, the cells in the body literally starve due to their inability to utlize the glucose that has not been broken-down by the release of insulin. Because of the body's lack of energy, the brain tells the animal to eat while other cells are demanding the body to start breaking down muscle and fat proteins. These muscle and fat proteins can be converted by the liver, into glucose. This begins a viscious cycle where more glucose is being created yet the body cannot create enough insulin to transfer the glucose into cells throughout the body.

The textbook definition of diabetes is¹: a general term referring to a variety of disorders characterized by polyuria and poly dipsia, as in diabetes mellitus and diabetes insipidus.

Diabetes Mellitus is a broadly applied term used to denote a complex group of syndromes that have in common a disturbance in the oxiation and ultilization of glucose. This is secondary to a malfunction of the beta cells of the pancreas whose function is the production and release of insulin. Because insulin is involved in the metabolism of carbohydrates, proteins and fats; diabetes is not limited to a disturbance of glucose homeostasis alone.

Diabetes mellitus has been recorded in all species, but is most commonly seen in middle-aged, obese, female dogs. A familial predisposition has been suggested. It may be possible to identify three types of diabetes, corresponding to the disease in humans, depending on the response to an intravenious glucose tolerance test.

Type I is comparable to the inherited juvenile form of the disease in children in which there is an absolute deficiency of insulin - there is a very low initial blood insulin level and a low response to the injected glucose.

Type II is similar to the maturity onset of diabetes in humans due to pancreatic damage -there is a high or normal initial blood insulin level and no increase in insulin levels as a result of the glucose load.

Type III is similar to chemical diabetes in humans and is clinically inapparent and most likely to be rsponsive to oral or dietary therapy - blood insulin levels prior to the injection of glucose are normal, there is a normal to delayed response to glucose injection and a delayed return to normal of blood insulin levels at 60 minutes.

Most dogs are diagnosed with Type I diabetes.


Clinical symptoms of Diabetes Mellitus

• Polyuria: increased volume of urine due to glucose being present - causes an osmotric diuresis
• Polydipsia: increased consumption plus amount of water, elevated blood glucose stimulates water intake by animal
• polyphagia - increased appetite by the animal in response to stimulation of the hypothalmus by fat and protein metabolism.
• Cataracts: stellate or star-like in nature - in the hyperglycemic state - glucose diffuses into the lens and is metabolized sorbitol and then fructose - unable to diffuse back out - osmotric pressure draws water into lens and disrupts the nature of lens fibers
• Urinary tract infections: glucose within the urinary tract can promote the growth of bacteria
• Ketoacidosis: caused by the excessive breakdown of fat for energy. Animals in severe ketoacidosis present with vomiting, diarrhea, anorexia, dehydration and neurological deficits.

Diabetes Mellitus (DM) Type I is caused by the destruction of beta cells within the islets of Langerhans resulting in a decreased amount to eventual complete loss of insulin secretion
IDDM (insulin dependent DM) - require insulin from the time of Dx
NIDDM (non-insulin dependent DM) - may not require insulin on the early stages of the disease but as time progresses. Most, if not all, will become IDDM patients.


Causes of Diabetes Mellitus (DM) Type I

• pancreatitis - inflammation or infection of the pancreas destroys tissues including those that secrete insulin
• Animals immune system targets the cells that make insulin and destroy them.
• Certain breeds are predisposed to the development of DM early in life.
• Amyloidosis in cats

Diabetes Mellitus (DM) Type II is characterized by insulin resistance at the cellular level and/or dysfunctional beta cells within the pancreas. Insulin secretion can be elevated, normal or decreased but it my be in insufficient quantities to overcome the resistance at the cellular level.Type II patients may be IDDM or NIDDM depending on the severity of resistance at the cell level or the degree of cell dysfunction present.


1. D.C Blood, OBE, and Virginia P. Studdert, BS DVM, Bailliere's Comprehensive Veterinary Dictionary, pg. 271