Veterinary Medicine - September 2007 - (Page 588)

CE OPEER-REVIEWED 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. Justin D. Thomason, DVM, DACVIM (internal medicine) Bente Flatland, DVM, DACVIM (internal medicine) Clay A. Calvert, DVM, DACVIM (internal medicine) H yperlipidemia is the increased concentration of triglyceride (hypertriglyceridemia), cholesterol (hypercholesterolemia), or both in the blood.1-3 Hyperlipidemia in dogs and cats can be physiological (postprandial) or pathological. Pathological hyperlipidemia can result from increased lipoprotein synthesis or mobilization or deJustin D. Thomason, DVM, DACVIM (internal medicine)* Department of Small Animal Medicine and Surgery College of Veterinary Medicine University of Georgia Athens, GA 30602 Bente Flatland, DVM, DACVIM (internal medicine) Department of Pathobiology College of Veterinary Medicine The University of Tennessee Knoxville, TN 37996 Clay A. Calvert, DVM, DACVIM (internal medicine) Department of Small Animal Medicine and Surgery College of Veterinary Medicine University of Georgia Athens, GA 30602 *Dr. Thomason’s current address is Department of Veterinary Clinical Sciences, Center for Veterinary Health Scieces, Oklahoma State University, Stillwater, OK 74078. creased lipoprotein clearance.1 It can be primary (genetic or idiopathic) or secondary to other disease processes.1 Veterinarians should be familiar with how to recognize and manage this clinical disorder. NORMAL LIPID METABOLISM Lipids are large, heterogeneous, naturally occurring fatty and related compounds that are insoluble in water but soluble in ether and alcohol.4-6 Lipoproteins, which are lipid and protein complexes, are essential components of cell membranes and are critical in the stabilization and transport of lipids in plasma.4 Once in plasma, lipoproteins deliver lipids to appropriate tissues via specific cell receptors.4,7 That is, cell membrane receptors in different tissues bind to specific lipoproteins. Classification Lipoproteins are classified by size, density, electrophoresis, and apoprotein content. 4 The four classes of lipoproteins are chylomicrons, verylow-density lipoproteins (VLDLs), lowdensity lipoproteins (LDLs), and highdensity lipoproteins (HDLs) (Table 1).4,7 Triglycerides (glycerol and fatty acids) are transported as chylomicrons and VLDLs.4 Cholesterol is transported as LDLs and HDLs.4 Digestion and absorption Lipid digestion is more complex than carbohydrate and protein digestion because fat must be solubilized in the water environment of gastric chyme to allow for enzymatic digestion. 5 Lipid digestion requires pancreatic lipase, pancreatic colipase, and bile from the gallbladder.5 Once in the duodenum, lipid is solubilized, with the assistance of gastric peristalsis, in bile and gastric chyme into lipid droplets.8 Pancreatic colipase then binds to these lipid droplets and anchors pancreatic lipase.5,8 Pancreatic lipase is then activated and degrades triglycerides to monoglycerides and free fatty acids and hydrolyzes dietary cholesterol.8 The monoglycerides, cholesterol, and free fatty acids along with bile acids form mixed micelles, with the more polar substances on the surface and the more hydrophobic substances (fatsoluble vitamins A, D, E, and K) in the core.5,8 The micelles diffuse passively into the enterocytes.5,8 Once absorbed by enterocytes, fatty acids and glycerol are repackaged into triglycerides and are bound to apolipoprotein to form chylomicrons.5,7,8 The absorbed cholesterol is also incorporated into the chylomicrons.8 Chylomicrons transport fat in the aqueous environment of lymph and plasma. They originate exclusively from the diet and are present in the plasma 30 minutes to two hours after a fat-containing meal is consumed. 3 Lipoprotein lipase, which is present in high concentrations near the endothe- 588 September 2007 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - September 2007

Contents Letters Leading Off The Veterinary Medicine Interview: Dr. William J. Kay Idea Exchange Practical Matters Salivary Mucoceles in Cates: A Retropspective Study of Seven Cases Hyperlipidemia in Dogs and Cats Purina Insert The Latest Management Recommendations for Cats and Dogs with Nonketotic Diabetes Mellitus CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - September 2007

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