Diabetes mellitus

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A 9-year old neutered male Siamese cat with obesity
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Diabetic neuropathy in a cat resulting in plantigrade stance

Diabetes mellitus (DM) is a common disorder of insulin regulation in mature, often obese cats that results in hyperglycaemia. It is clinically distinct from diabetes insipidus, a more rare disease that affects young cats.

Diabetes in cats is caused either by insufficient insulin secretion by Islet of Langerhans beta-cells within the feline pancreas due to pancreatic amyloidosis, or by insulin resistance (as is seen in obesity and acromegaly). Nutrition plays a pivotal role in prevention and treatment of this disease[1].

Cause

Until the 1970s, diabetes mellitus was a relatively rare disease in cats. The relationship between commercial high-carbohydrate diet and the onset of diabetes mellitus cannot be ignored.

The pancreatic hormones amylin, insulin and glucagon appear to have an intimate relationship in regulation of blood glucose in cats and deposition of amylin within the pancreatic Islets of Langerhans leads to pancreatic amyloidosis, seen in a large proportion of cats with diabetes mellitus and obesity[2][3]. Oxidative stress, thought to be a key component in the pathophysiology of diabetes mellitus in humans, may be responsible for amylin fibril deposition in cats. The use of high protein-low carbohydrate diets in diabetic cats may lead to a significant reduction in oxidative stress (Webb & Falkowsji, 2009). Oxidative stress may affect neutrophil lifespan, and phagocytic cell function may be negatively impacted by oxidative stress in patients with DM, resulting in a decrease in their ability to prevent or eliminate infection within the Islets of Langerhans.

Secondary causes include obesity, pancreatitis, and neoplasia (e.g. acromegaly, pheochromocytoma, Cushing's syndrome). Certain medications (e.g. megestrol acetate, methylprednisolone acetate) have been incriminated[4][5].

Clinical signs

Diabetes mellitus most often occurs in older, obese individuals; males are more commonly afflicted than females. Burmese appear more at risk than other breeds.

Early clinical signs are associated with hyperglycaemia, such as polyuria and polydipsia. As the disease progresses, weight loss, vomiting, anorexia, weakness, and dehydration occur. Urinary tract infections develop in about 15% of diabetic patients[6]. Microalbuminuria is a common finding in cats with diabetes mellitus[7].

Advanced secondary neurological signs occur in a significant number of untreated cases such as diabetic neuropathy, diabetic retinopathy, cataracts and metabolic epidermal necrosis due to sorbitol accumulation associated with unregulated hyperglycaemia. Life-threatening diabetic ketoacidosis (DKA), hyperosmolar hyperglycaemic state (HHS) and insulin-induced hypoglycaemia may develop in some diabetic cats. Without proper and prompt treatment, this condition ultimately proves fatal.

Unlike humans, cats do not normally have hypertension associated with diabetes[8].

Diagnosis

Diabetes mellitus is diagnosed based on the cat's clinical signs, physical examination findings, laboratory results, and the persistent presence of abnormally high amounts of sugar in the blood and urine. In stressed patients, adrenalin release causes hyperglycaemia and glucosuria. It is essential to differentiate between stress response and diabetes[9].

  • Urinalysis - the presence of glucose in the urine (glucosuria) is associated with a blood glucose level greater than 15 mmol/L. any glucose in the urine is abnormal and often is an indicator of diabetes. Other conditions such as fanconi syndrome can also cause glucosuria.
  • Blood sugar - glucose levels below 10 mmol/L are considered normal. Levels of glucose >10mmol/L may be seen in severe physiological stress but may be an indicator of diabetes.
  • Fructosamine assay[10].

Treatment

  • Diet - management with low carbohydrate/low fat diets
  • Oral hypoglycaemic drugs - rarely used in cats, and shown to be poorly effective at regulating hyperglycaemic states
- Acarbose - the alpha-glucosidase inhibitors (eg, acarbose) reduce intestinal glucose absorption (Greco 1999) and are generally not effective in the treatment of feline diabetes alone, but can be used in conjunction with insulin and/or other oral agents to gain better glycemic control . Cats given acarbose and fed a low carbohydrate diet had a reduced insulin requirement and improved glycaemic control, but similar results were achieved feeding the low carbohydrate diet alone[11].

A diabetic cat may live many healthy years with owners who are willing to put forth the effort of monitoring the cat's condition daily. Cats tend to be difficult to maintain on the same regimen for long periods of time, and increases or decreases may need to be made in drug dosages.

See also

References

  1. Miller E (1995) Long-term monitoring of the diabetic dog and cat. Clinical signs, serial blood glucose determinations, urine glucose, and glycated blood proteins. Vet Clin N Am Small Anim Pract 24:571-585
  2. O'Brien TD (2001) Pathogenesis of feline diabetes mellitus. Mol Cell Endocrinol 197(1-2):213-219
  3. Furrer D et al (2010) Amylin reduces plasma glucagon concentration in cats. Vet J 184(2):236-240
  4. Nelson R (2000) Diabetes Mellitus. In: Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine. Diseases of the Dog and Cat, 5th ed. Philadelphia, W.B. Saunders Co. p. 1443
  5. Scherk, M (2007) Focus on feline medicine, PGFVSc Conference proceedings, University of Sydney, NSW, Australia
  6. Bailiff, NL et al (2006) Frequency and risk factors for urinary tract infection in cats with diabetes mellitus. J Vet Intern Med 20:850
  7. Al-Ghazlat SA et al (2011) The prevalence of microalbuminuria and proteinuria in cats with diabetes mellitus. Top Companion Anim Med 26(3):154-157
  8. Hess, RS (2010) Diabetic emergencies. In August, JR (Ed): Consultations in feline internal medicine. Vol 6. Elsevier Saunders, Philadelphia. pp:297
  9. Webb, CB & Falkowski, L (2009) Oxidative stress and innate immunity in feline patients with diabetes mellitus: the role of nutrition. JFMS 11:271-276
  10. Graham PA, Mooney CT, Murray M (1999) Serum fructosamine concentrations in hyperthyroid cats. Res Vet Sci 67:171-175
  11. Mazzaferro EM et al (2003) Treatment of feline diabetes mellitus using an alpha-glucosidase inhibitor and a low-carbohydrate diet. J Feline Med Surg 5(3):183-189
  12. Rand, JS (2010) Use of long-acting insulin in the treatment of diabetes mellitus. In August, JR (Ed): COnsultations in feline internal medicine. Vol 6. Elsevier Saunders, Philadelphia. pp:286