Hyperlipidemia in dogs and cats - Veterinary Medicine
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Hyperlipidemia in dogs and cats
Increased triglyceride or cholesterol concentrations will often normalize if they are caused by a secondary disease that is successfully treated. If the hyperlipidemia is primary, dietary modification and pharmacologic intervention may be required.


VETERINARY MEDICINE


Lipoprotein lipase is necessary for removing VLDL and chylomicron fatty acids from the blood.4,7 Lipoprotein lipase activity is increased by heparin, insulin, and thyroid hormone.3,9 So patients with diabetes mellitus, pancreatitis, or hypothyroidism tend to have hyperlipidemia.9 In addition, familial lipoprotein lipase deficiency in cats and dogs is reported.1 Increased VLDL concentrations caused by increased serum triglycerides results in increased production of LDLs when the fatty acids are removed.7 Because of the cholesterol in LDLs, lipoprotein lipase deficiency can result in a mild to moderate increase in total serum cholesterol (500 to 750 mg/dl). Severe hypercholesterolemia may occur in association with cholestasis because excretion in the bile is the major route for removal of excess cholesterol from the body.1 In our experience, severe hypercholesterolemia can also occur secondary to hypothyroidism.

Familial hyperlipidemia occurs most often in miniature schnauzers and beagles.10,11 In cats, familial hyperlipidemia is associated with lipoprotein lipase deficiency and hyperchylomicronemia.1,11,12

CLINICAL SIGNS

The clinical manifestations of hyperlipidemia in dogs are associated with dysfunction in the gastrointestinal, neurologic, and ocular systems. The primary clinical findings include vomiting, diarrhea, abdominal pain, abdominal distention, anorexia, seizure activity, lipemia retinalis, and lipemic aqueous humor.1-3 Although clinical signs and history may be consistent with pancreatitis, laboratory data and imaging studies may fail to support a diagnosis of pancreatitis. Because of the large size of chylomicrons, severe hyperchylomicronemia (> 1,000 mg/dl) can result in the occlusion of organ blood vessels.1 If the pancreatic vessels are occluded, subsequent pancreatic ischemia results in a vicious cycle of lipase leakage, fatty acid degeneration, free radical production, and tissue damage with secondary pancreatitis.1 In people and animals, sustained hyperlipidemia is a principal risk factor for developing pancreatitis, and patients that present with pancreatitis should be evaluated for hyperlipidemia.1,2

In cats, hyperlipidemia can cause cutaneous lesions and peripheral neuropathies. The most common clinical finding is cutaneous xanthoma, a painless raised lesion caused by an accumulation of lipid-laden macrophages or foam cells in the skin.1-3,13,14 Although sites of nerve involvement vary, Horner's syndrome, tibial nerve paralysis, and radial nerve paralysis are common.2

Increased LDL and VLDL cholesterol are risk factors for atherosclerosis in people.8,15 Dogs and cats are considered resistant to atherosclerosis associated with hypercholesterolemia for two reasons: First, unlike in people, the preponderant circulating lipoprotein in dogs and cats is HDL.9,11 Second, most dogs and cats maintain relatively low LDL concentrations because of unique hepatic metabolism that promotes increased HDL and decreased LDL production.9 Nonetheless, when the cholesterol concentration exceeds 750 mg/dl in dogs and 650 mg/dl in cats, there is a relative increase in the LDL particles that predisposes the animals to atherosclerosis.9

DIAGNOSIS


Table 3: Diagnostic Tests and Expected Results for Patients with Hyperlipidemia*
Consider hyperlipidemia in dogs or cats that present for evaluation of clinical signs compatible with hyperlipidemia or with fasting lipemia (lactescent serum). A variety of diagnostic tests are available. See Table 3 for an overview of the test results that indicate hyperlipidemia.


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Source: VETERINARY MEDICINE,
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