Diabetes mellitus is an absolute or relative deficiency of the hormone insulin. Insulin is synthesized and released from beta cells in the pancreatic islets. Insulin assists with cellular uptake of glucose from the bloodstream into the cells of the body for energy. This causes a hypoglycemic effect. Within cells, insulin promotes anabolism, such as the production of glycogen, fatty acids, and proteins, and counters catabolic events to reduce gluconeogenesis and inhibit fat and glycogen breakdown.
Insulin lowers blood glucose, whereas opposing hormones including glucagon, cortisol, progesterone, adrenaline, thyroid hormone, and growth hormone increase blood glucose. It’s important to consider these counterregulatory hormones, because changes in their blood concentrations interfere with insulin actions. Changes in these hormones result from natural physiological conditions, disease states, or drug administration.
As the blood glucose concentration increases due to insufficient insulin, the kidneys become overwhelmed by the blood glucose concentration and glucose spills into the urine. The osmotic action of glucose leads to polyuria and, through loss of fluid, to polydipsia.
In the absence of sufficient insulin, diabetic cats will switch from glucose to fat metabolism for cellular energy. While this is initially beneficial, fat metabolism in unrecognized or untreated diabetics typically causes a deteriorated general condition and progresses to ketoacidosis and ultimately to death.
Diabetes mellitus is not related to diabetes insipidus, an extremely rare condition in cats that occurs when the kidneys are unable to regulate fluids in the body. Diabetes insipidus is characterized by a deficiency or inadequate response to a hormone called vasopressin.
Disease prevalence and risk factors
Estimates of the prevalence of diabetes mellitus in cats ranges from to 1 in 50 to 1 in 500.9 The diagnosis is often preceded or accompanied by obesity. Diabetes is also more common in middle- to older-aged cats. Neutered male cats are at greater risk than female cats.
Determining an effective treatment regimen for diabetic cats can be challenging. Factors that affect the type and success of treatment include:
- The severity of pancreatic beta cell loss
- The responsiveness of tissues to insulin
- The presence or absence of glucose toxicity
- Problems with absorption and duration of effect of exogenously administered insulin
- Presence of concurrent disease
Most forms of diabetes can be successfully treated with insulin—the cornerstone of successful management—but dietary adjustments and a regular lifestyle are also important.
In general, the prognosis for diabetic cats is very good, especially with early diagnosis and proper therapy. Additional factors that affect the prognosis for diabetic cats include:
- Owner commitment to disease management
- Presence and nature of concurrent disorders (eg, pancreatitis, acromegaly)
- Avoidance of chronic complications
The most common chronic complication of diabetes in cats is the development of peripheral neuropathy, which is exhibited by weakness in the hind legs. Diligent control of hyperglycemia can potentially reverse the clinical signs of neuropathy, but it can take several months. Also, recurrent infections commonly affect both canine and feline diabetics.
Open communication between you and your client is an extremely important factor. Encouraging your clients helps ensure their motivation and compliance with management. Clients need to fully understand the disease to help achieve and maintain good diabetic stability and be highly motivated and committed to the management of their cats. Your clinical staff also has an important role in providing detailed client education, instruction, and encouragement.