Advances in the Treatment
of Diabetes in Cats
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The majority of cats (50-60%) develop diabetes similar to non-insulin dependent diabetes mellitus (NIDDM) in humans.   In this type of diabetes, there is both impaired insulin secretion from the pancreas as well as resistance to the effects of insulin.  Obesity plays a significant role in the insulin resistance seen in feline diabetics.

Approximately 1 in 100 cats develop feline diabetes mellitus (DM). Neutered male cats are 1.5 times more likely to develop DM as female cats.   Increased body weight (>6.8 kg or >15 lbs), age (>10 years) and neutering are other risk factors.   The most common physical findings of feline DM include lethargy, irritability, depression, dehydration, unkempt haircoat (poor grooming and dandruff), and muscle wasting.    Only about 12% of diabetic cats exhibit polyphagia (excessive hunger).  Chronic gastrointestinal symptoms as well as gait abnormalities are seen.   The incidence of subclinical (not yet displaying symptoms) diabetic neuropathy (nerve dysfunction) is very high based on EMG and nerve conduction studies.

Cats are easily stressed by blood draws, transportation to the veterinarian, separation from their caretaker, and other actions. Stress-induced hyperglycemia may cause serum glucose elevations of up to 300-400mg/dl and result in falsely elevated blood glucose level tests.   Renal glycosuria (glucose in the urine) may be found in felines with renal tubular disease and occasionally with stress-induced hyperglycemia.   Therefore, diagnosis of DM cannot be simply based on a blood glucose test. Diagnosis is based on three criteria: clinical signs, fasting hyperglycemia and glycosuria.   Normal fructosamine concentrations (<350 mg/dl) may also help distinguish stress-induced hyperglycemia from DM.  

In a study of high fiber diets in cats, 9 out of 13 diabetic cats showed a significant improvement in glycemic control with consumption of a high fiber diet. These diets include prescription foods such as Hill’s W/D.  Increased fiber slows the rate of glucose absorption from the intestine and minimizes the postprandial (after eating) fluctuations in blood glucose.   More recent research indicates that diabetic cats that are not obese will do better on a low carbohydrate, high-protein diet than a high fiber diet.   Purina DM is one such high-protein diet. Other recent developments in diet research are resulting in more veterinarians recommending wet food rather than dry food for all cats, especially those with diabetes.

Although similar to human DM, feline diabetes has some important differences. Arginine, an amino acid, is the signal for cats to produce insulin in their pancreas.   Glucose is the signal to produce insulin in people.   If blood glucose levels in research cats are maintained at >540 mg/dl, the cats become diabetic.   This finding has led to a hypothesis that high carbohydrate diets produce diabetic cats. The choice of food is difficult because of all the new research and you will need to work with your veterinarian and your cat to find out the best diet.

Treatment of NIDDM is aimed at decreasing hepatic (liver) glucose output and glucose absorption from the intestines, increasing peripheral insulin sensitivity, and increasing insulin secretion from the pancreas.   Reversal of glucose toxicity using a short course (30 days) of insulin therapy prior to or in combination with oral hypoglycemic agents may improve the response to oral hypoglycemic agents. Oral hypoglycemic medicines such as glipizide initially seemed to have no affect in cats, perhaps due to the glucose toxicity. Your veterinarian will most likely start your newly diagnosed cat on insulin and then may consider switching to an oral agent.  

The oral antidiabetic medications (sulfonylurea) work to increase insulin secretion and decrease insulin resistance so that the insulin works on the cells much better.. Some of these agents also cause a decrease in hepatic glucose output.  Side effects of the sulfonylureas include gastrointestinal side effects such as diarrhea, constipation, and flatulence. These are usually non-existent or minimal if the drug is given with food.  One serious side effect is that they may promote progression of pancreatic amyloidosis by increasing insulin release.     If either glipizide (2.5-5mg BID) or glimiperide (1-2 mg SID) fail to decrease glucose below 200 mg/dl and the cat is still symptomatic after 2-3 months of therapy, the drug should be discontinued.  

Vanadium and chromium have been shown to affect blood glucose and insulin when given to mice and rats suffering from DM.   A recent human study found that giving 1,000 ug of chromium picolinate once a day to 180 NIDDM patients improved the signs of DM and normalized blood levels of hemoglobin A1c.   Vanadium and chromium do not lower blood glucose concentrations in normal animals but research has shown they can be effective in cats.    Studies indicate that low doses of oral vanadium (commercially available as Vanadyl Fuel; 1 or 2 capsules per day on food) will decrease blood glucose and serum fructosamine concentrations and alleviate DM clinical signs in cats with early NIDDM.   Chromium at 200 ug/cat once a day may also be tried.   Bacon is high in chromium.

Human recombinant insulin is usually recommended as the initial insulin preparation used in cats mainly because many animal-source insulins have been discontinued.   However, beef insulin is most similar to cat insulin, differing by only one amino acid in the A chain.   Beef-pork insulin is 90% beef and 10% pork insulin.   Long-acting insulin (ultralente or U) is dosed at the higher end of the range (up to 2 U/kg) as it is absorbed more slowly and tends to be less potent.   Initial insulin dosages range from 0.2-0.5 U/kg in cats and should be given twice daily because of the rapid metabolism of insulin.   Some commonly used insulins in cats are BID lente (L) or NPH (N), or SID Beef  PZI (U-40 Blue Ridge Pharmacies: 1-3 U/cat) insulin in cats.   Lantis is another long-acting insulin that is now being used some in cats. Often the response to ultralente (U) and Lantis insulin is disappointing in the cat but each animal is individual and some do well on these long-acting insulin preparations.

Well-regulated DM cats should be monitored every 6 months, and poorly regulated diabetics every 3 months, with either a fructosamine or an A1c test.   Serum fructosamine is available as an automated test kit and may be used to assess long-term (>3 weeks) control. Serum fructosamine concentrations <450 mg/dl (<400 umol/L) indicate good glycemic control.   Glycosolated hemoglobin, or A1c, at normal levels for cats <3.0 or <0.8% reflects glycemic control over the previous 70 days.  

Cats are particularly susceptible to hypoglycemia and can have quite severe episodes with few preceding warning signs.    One possible reason for this “hypoglycemic unawareness” is autonomic neuropathy.   Often, reasonable glycemic control can be achieved with blood glucose nadirs (low points) of 150 mg/dl and glucose differentials (the difference between the highest and lowest levels) of 200 mg/dl.  Experience indicates that the nadir of blood glucose levels is certainly best kept above 100 mg/dl to minimize the chance of hypoglycemic episodes.   Also, combining other agents (oral antidiabetic agents or nutritional supplements, for example) with insulin therapy in the cat should be undertaken very cautiously due to the danger of severe hypoglycemia.

The site of insulin injection in the cat is important.   Absorption of insulin from the abdomen is more rapid than from the thigh.   Injection of insulin into an extremity may result in inconsistent insulin absorption depending on exercise and limb movement.   The neck is often the injection site due to increased ease for the caretaker and decreased sensitivity for the cat; however, this area is prone to fibrosis (often noted as lumps under the skin) and lack of blood flow, both of which interfere with absorption. Some veterinarians recommend administration of insulin at sites along the lateral abdomen and thorax (chest) to improve insulin absorption.

Glucometers are altitude sensitive.   Venous blood strips can be requested from the manufacturers that give glucose values closer to lab values.   Whole blood glucoses are lower than serum glucoses.   High hematocrits decrease glucose values.  

REFERENCES:

American Association of Feline Practitioners, http://www.aafponline.org

Animal Medical Center of New York, http://www.amcny.org

Cornell Feline Health Center, http://www.vet.cornell.edu/Public/FHC/diabetes.html

Feline Diabetes Dictionary, 2004, http://www.felinediabetes.com/dictionary/index.html

Updated February 2012

2004

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