Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

Chapter 4
Lipids and Ketones
Michael L. Bruss
Department of Anatomy, Physiology, and Cell Biology
School of Veterinary Medicine
University of California, Davis
Davis, California
I. INTRODUCTION
II. LONG CHAIN FATTY ACIDS
A. Structure, Properties, and Assay of Long Chain
Fatty Acids
B. Synthesis of Long Chain Fatty Acids
C. Catabolism of Long Chain Fatty Acids
III. TRIACYLGLYCEROL
A. Structure, Properties, and Assay of Triacylglycerol
B. Synthesis of Triacylglycerol
C. Catabolism of Triacylglycerol
IV. PHOSPHOLIPIDS
A. Structure and Properties of Phospholipids
B. Synthesis of Phospholipids
C. Catabolism of Phospholipids
V. CHOLESTEROL
A. Structure, Properties, and Assay of Cholesterol
B. Metabolism of Cholesterol
VI. LIPOPROTEINS
A. Structure, Properties, and Assay of Lipoproteins
B. Apolipoproteins
C. Digestion of Fat and Formation of Chylomicrons
D. Very Low Density Lipoprotein: Synthesis, Export,
and Metabolism
E. Metabolism of High-Density Lipoproteins
VII. HYPERLIPIDEMIA
A. Introduction
B. Canine Fasting Hyperlipidemias
C. Feline Fasting Hyperlipidemias
D. Equine Fasting Hyperlipidemia
VIII. KETOGENESIS AND KETOSIS
A. Introduction
B. Chemistry of Ketones
C. Synthesis of Ketones
D. Catabolism of Ketones
E. Pathophysiology of Ketonemia
F. Fasting Ketosis
G. Diabetic Ketosis
H. Ketosis Associated with Pregnancy and Lactation
I. Postexercise Ketosis
REFERENCES
I. INTRODUCTION
This chapter covers the biochemistry and clinical chemistry
of long chain fatty acids, triacylglycerols, phospholipids,
cholesterol, and ketones, a list that includes the
majority of lipids found in vertebrates. The only remaining
major classes are sphingolipids and waxes, which are
not discussed here. Although lipids have many functions,
two of the most important are energy storage and membrane
structure. Triacylglycerols are by far the most important
lipid with regard to energy storage, and phospholipids
and cholesterol are the most important lipid membrane
constituents. Lipids serve other functions, including being
precursors for steroids and bile acids (cholesterol), thermal
insulation (triacylglycerols), and electrical insulation (various
lipids). Virtually all lipids are insoluble in water, which
greatly complicates their handling in the body. Because of
their insolubility, lipids must rely on proteins for transport
for any significant distance in the body, and various proteins
have evolved to provide this function. The insolubility
of lipids is an asset as well as a liability. Because of
their insolubility, lipids generate no osmotic force, so large
amounts of triacylglycerol can be stored in adipose without
the weight gain from water that would accompany it if
it were soluble. The insolubility of lipids is vital to many
of their functions in membranes.
II. LONG CHAIN FATTY ACIDS
A. Structure, Properties, and Assay of Long
Chain Fatty Acids
Long chain fatty acids (LCFA), frequently called free fatty
acids or nonesterified fatty acids, are straight chain fatty
acids containing twelve or more carbon atoms. Because
LCFA are usually synthesized in animals or plants from
acetyl-CoA and are then degraded two carbons at a time via
β-oxidation in animals, the LCFA found most commonly in
animals have an even number of carbon atoms. LCFA having
Clinical Biochemistry of Domestic Animals, 6th Edition 81
Copyright © 2008, Elsevier Inc.
All rights reserved.