Lipoprotein Metabolism in Dogs and Cats

Abstract

High-density lipoproteins (HDL) are the predominant lipoproteins in plasma of dogs and cats and are the major cholesterol-carrying particles. Two HDL subfractions are identifiable in dog: small, dense particles (equivalent to human HDL3) and large, buoyant particles called HDL1, which overlap in hydrated density with low-density lipoproteins (LDL). The HDL1 are enriched in cholesterol and apolipoprotein (apo) E, and are prevalent in dogs fed high amounts of cholesterol and, or, saturated fat, when they are also referred to as HDLc. Lipoproteins similar to human HDL2 and HDL3 are identifiable in feline plasma, along with trace HDL1. Lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyl transferase (LCAT) activities are present in dogs and cats. Both species lack significant cholesteryl ester transfer protein activity, and reverse cholesterol transport is probably accomplished by receptor-mediated hepatic uptake of HDL1. Methods for the measurement of canine and feline plasma lipoprotein-cholesterol concentrations, apolipoprotein concentrations, and the activities of LPL, HL and LCAT have been developed. Together with oral and intravenous fat tolerance tests, these methods provide the basis for studying lipoprotein metabolism in cats and dogs.