Lipids Flashcards
What are lipids soluble in?
Organic solvents, relatively insoluble in water
What are the more frequently measured lipids?
Cholesterol and triglycerides
What are the lipids found in mammals?
Sterols Glycerol esters Fatty acids Sphingosines Terpenes
What are examples of sterols?
Cholesterol Cholesterol esters Bile acids Steroid hormones Vitamin D
What are examples of glycerol esters?
Phospholipids
Monoglycerides
Diglycerides
Triglycerides
What are examples of fatty acids?
Short, medium, and long-chain prostaglandins
What are examples of sphingosines?
Shinomyelin
Glycosphingolipids
What are examples of terpenes?
Vitamins A, E, and K
What are the functions of lipids?
Energy
Structural cell membrane
Substrate for hormones
Second messengers
What are most of cholesterol and all TG associated to?
Lipoproteins
What are lipoproteins classified by?
Their electrophoresis mobility or their density in comparison to water
What is the general composition of lipoproteins?
Outside surface contains phospholipids, cholesterol, and apolopoprotein; core is TGs and cholesterol esters
What does the density of lipoprotein increase with?
The increase of [protein]
Do dogs, cats, and horses habe more HDL or LDL?
HDL
What does a predominance of HDL mean?
Less cholesterol transfer between lipoproteins leading to decreased suscetibility to atherogenesis
What is the lipid to protein ratio of dietary TG?
70:1
What is the lipid to protein ratio of phospholipid and cholesterol ester?
1:1
What do disorders of lipoprotein metabolism involve?
Excess synthesis, defective lipolysis, or defective clearance or cellular uptake of lipoproteins
What catalyzes lipolysis?
LPL
What does intravenous heparin do to lipoprotein metabolism?
Promoted release of LPL from endothelial cells and heptaocyte lipase to plasma
What are lipoprotein remnants cleared from the plasma by?
Hepatocytes
What is critical for lipoprotein metabolism?
Apolipoproteins
What is apolipoprotein A?
Intestine, liver
Associated mostly with HDL
What is apolipoprotein B?
Intestine, liver
Synthesis and secretion of chylomicrons and VLDL; endocytosis of lipoprotein particles from VLDL, IDL, LDL, and chylomicrons remnants
What is apolipoprotein C?
Liver
Mostly in VLDL, HDL, chylomicrons
C-II is a cofactor for LPL
What is apolipoprotein D?
LCAT< HDL
What is apolipoprotein E?
Liver, macrophages
All lipoproteins
What are the major lipases?
LPL
Hepatic lipase
Where are hepatic lipases?
Endothelial cells of hepatic sinusoids
What do many extrahepatic cells produce?
LPL
What is the activity of extrahepatic cells enhanced by?
Insulin
Thyroxin
Heparin
Where is most of the circulating cholesterol in fasting?
Lipoproteins
What is most of the circulating cholesterol produced by in fasting?
Hepatocytes
What does cholesterol synthesis start with?
Acetyl CoA
What is the potential toxic effect of free cholesterol prevented by?
Cholesterole esterification
What delivers hepatocyte-made cholesterol to other cells?
LDL
What scavenges excess cholesterol throughout the body and delivers it to hepatocytes?
HDL
How does cholesterol enter cells?
Receptor-mediate endocytosis
What is serum [cholesterol] composed of?
Cholesterol and cholesterol esters
What sample is preferred for cholesterol?
Serum
What causes hypercholesterolemia?
Increased production by hepatocytes and enterocytes
Decreased lupolysis or intravascular processing of lipoproteins
Cholestasis
Diabetes mellitus
What causes increased production of cholesterol by hepatocytes?
Nephrotic syndrome or protein-losing nephropathy
What causes increased production of cholesterol by enterocytes?
Posprandial hyperlipidemia
What causes decreased lipolysis or intravascular processing of lipoproteins associated with hypercholesteremia?
Hypothyroidism
Nephrotic syndrome or protein-losing nephropathy
What causes hypocholsterolemia?
Decreased cholesterol production
Hypoadrenocorticism
What are triglycerides?
3 fatty acids bound to a glycerol backbone
What transports TG from intestine and liver to myocytes and adipocytes?
Lipoprotein
In fasting animals, what are most TGs produced by?
Hepatocytes
What are most TGs associated to in fasting animals?
Lipoproteins
What are most of the TGs produced by in a postprandial state?
Enterocytes
What are most of the TGs associated to in a postprandial state?
Chylomicrons
What does production of TGs start with?
Fatty acids and glycerol is added
What sample is preferred for TGs?
Serum
What can cause sample turbidity with TGs?
Increased concentration of chylomicrons or VLDL
What causes hyppertriglyceridemia?
Increased triglyceride production by hepatocytes and enterocytes
Decreased lipolysis or intravascular processing of lipoproteins
Acute pancreatitis
Diabetes mellitus
What causes increased triglyceride production by hepatocytes?
Equine hyperlipemia or hyperlipidemia
What causes increased triglyceride production by enterocytes?
Postprandial hyperlipidemia
What causes hypotriglyceridemia?
No significant pathological states
What are hyperlipemia and hyperlipidemia?
Increased [lipids] in the blood
What is hyperlipoproteinemia?
Increased [lipoprotein] in the blood
What is lipemia or lipidemia?
Used to describe turbid or opaque appearance of serum or plasma
What are causes of primary (familial) hyperlipoproteinemia?
Congenital defects of lipoprotein metabolism
Uncommon in domestic animals
Increased production of lipoproteins by hepatocytes
Defective intravascular processing of lipoproteins
Defective cellular uptake of lipoprotein remnants
What are causes of secondary hyperlipoproteinemia?
Acquired
Involves damaged cells or abnormal hormone production
What causes physiologic (postprandial) hyperlipidemia in monogastric animals?
Chylomicrons
What are examples of primary hyperlipidemia?
Idiopathic hyperlipidemia of Miniature Schnauzers
Hyperlipidemia in a Brittany dog
Idiopathic hyperlipidemia in other breeds
Congenital LPL deficiency in a mixed-breed puppy
Primary hyperchylomicronemia in cats
Hypercholestrolemia in Briards
What is the pathogenesis of acute pancreatitis?
Likely decreased processing of chylomicrons and VLDL
What do 75% of hypothyroid dogs have?
Fasting hypercholesterolemia
What do 90% of dogs with hyperadrenocorticism have?
Fasting hypercholesteremia
What are causes of nephrotic syndrome and PLN in dogs and cats?
Increased hepatic production of VLDL
Deficiency of lipases and some lipoprotein receptors
Defective conversion of cholesterol to bile acids
What are mechanisms of equine hyperlipemia?
Catecholamines and glucagon stimulate hormone-dependent lipase in hepatocytes releasing fatty acids
Glucocorticoid hormones stimulate hormone-dependent lipase in hepatocytes
Decreased insulin activity inhibits LPL which decreases hydrolysos of TG