Hyperlipidemia is a condition characterized by increased levels of triglyceride, cholesterol, or both in the blood. It can be physiological, occurring after a meal, or pathological, resulting from abnormal lipoprotein synthesis or clearance. Veterinarians should be knowledgeable about recognizing and managing this disorder in dogs and cats.
Normal Lipid Metabolism
Lipids are fatty compounds that are insoluble in water but soluble in ether and alcohol. Lipoproteins, which are complexes of lipids and proteins, play a crucial role in stabilizing and transporting lipids in the blood. They deliver lipids to various tissues through specific cell receptors.
Classification of Lipoproteins
Lipoproteins are classified based on size, density, electrophoresis, and apoprotein content. The four classes of lipoproteins are chylomicrons, very-low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs). Triglycerides are transported as chylomicrons and VLDLs, while cholesterol is transported as LDLs and HDLs.
Digestion and Absorption
Lipid digestion is more complex than carbohydrate and protein digestion because fats need to be solubilized in the water environment of the stomach for enzymatic digestion. This process requires pancreatic lipase, pancreatic colipase, and bile from the gallbladder. Once absorbed by enterocytes, fatty acids and glycerol are repackaged into triglycerides and transported as chylomicrons.
Pathophysiology of Hyperlipidemia
Hyperlipidemia can be caused by dietary intake of lipids, excessive production or mobilization of lipids, or ineffective clearance of lipids from the blood. The underlying cause can be either familial or acquired. Patients with hyperlipidemia may experience a variety of symptoms, depending on the affected systems, such as gastrointestinal, neurological, and ocular.
Diagnosis of Hyperlipidemia
Hyperlipidemia should be considered in dogs or cats with clinical signs compatible with the condition or fasting lipemia (lactescent serum). Diagnostic tests, including gross appearance of plasma, chylomicron test, and measurement of triglyceride and cholesterol concentrations, can confirm the presence of hyperlipidemia.
The treatment of hyperlipidemia involves addressing the underlying cause, modifying the diet, and potentially using pharmacologic intervention. Diet modification, such as switching to a low-fat diet, is often the first step. For patients that do not respond adequately to dietary changes, lipid-reducing medications can be considered.
Secondary hyperlipidemia can be resolved or improved with effective treatment of the underlying disorder. Patients with primary hyperlipidemia require long-term commitment from both the owner and the veterinarian. Most patients respond well to diet modification or a combination of diet and medication.
For more information about hyperlipidemia in dogs and cats, visit Katten TrimSalon.
Article based on “Hyperlipidemia in dogs and cats” by Justin D. Thomason, DVM, Bente Flatland, DVM, and Clay A. Calvert, DVM