Stockham & Scott Chapter 16 Lipids AKG

Question 1

What are the measured lipid components in blood:

Answer 1

Cholesterol and Triglycerides, which are transported in serum via lipoproteins

Question 2

List examples of sterols:

Answer 2

Cholesterol

Bile acids

Steroid hormones

Vitamin D

Question 3

Fatty acids can circulate outside of lipoproteins, bound to albumin. T/F

Answer 3

True

Question 4

Prostaglandins are what type of lipid?

Answer 4

Fatty acids

Question 5

Give examples of terpenes (type of lipid):

Answer 5

Vitamins A, E, and K

Question 6

List lipoproteins from lowest to highest protein content (and from highest to lowest triglyceride content)

Answer 6

1. Chylomicrons
2. VLDL
3. IDL
4. LDL
5. HDL

Question 7

Which lipoprotein has the highest cholesterol content and is the main lipoprotein in dogs:

Answer 7

HDL (considered the ‘good’ cholesterol in humans)

Question 8

_____ are specific components of lipoproteins that influence their structure, serve as cofactors for enzymes, and act as ligands.

Answer 8

Apolipoproteins

Question 9

HDL express which class of apolipoproteins?

Answer 9

A, C, E, D (all except B)

Question 10

Chylomicrons express which class of apolipoproteins?

Answer 10

A, B, C, E (all except D)

Question 11

VLDL & IDL express which class of apolipoproteins?

Answer 11

B, C, E (all except for A & D)

Question 12

What makes lipoproteins containing apolipoprotein C-II special?

Answer 12

It allows them to bind to LPL on endothelial cells, and cleave fatty acids from triglyceride molecules. FAs then enter the cells (e.g., adipocytes, myocytes). This process repeats until TG is depleted.

Question 13

This lipoprotein delivers cholesterol produced in the liver to other cells/tissues.

Answer 13

LDL

Question 14

This lipoprotein scavenges excess cholesterol from cells and delivers it to the liver.

Answer 14

HDL

Question 15

This lipoprotein is rich in triglycerides, transports TG from GIT to tissues, and is produced by enterocytes.

Answer 15

chylomicrons

Question 16

This lipoprotein is rich in triglycerides, produced in the liver from NEFAs liberated by fat breakdown, and transports TGs from liver to tissues.

Answer 16

VLDL

Question 17

This lipoprotein is rich in cholesterol, is produced from VLDL, transports cholesterol to tissues, and is taken up by LDL receptors.

Answer 17

LDL

Question 18

This lipoprotein is rich in cholesterol, produced in the liver, and transports cholesterol from tissue to the liver.

Answer 18

HDL

Question 19

This apoplipoprotein is a co-factor for LPL.

Answer 19

C-II

Question 20

_____ is found on the luminal surface of endothelial cells, mediates removal of TGs from chylomicrons, VLDL, and IDL into tissues, and promotes binding of LDL to its receptor a.

Answer 20

Lipoprotein lipase

Question 21

Lipoprotein lipase needs _____ to travel from inner- to outer- membrane leaflet on endothelial cells so they can come into contact with plasma lipoproteins.

Answer 21

Insulin

Question 22

Increased LPL activity leads to _____ plasma TG and choelsterol.

Answer 22

decreased

Question 23

IV ____ promotes release of LPL from endothelial cells and is aka “lipemia clearing factor”

Answer 23

heparin

Question 24

LPL activity is enhanced by…

Answer 24

Insulin Thyroxine Heparin

Question 25

What is the rate limiting enzyme in cholesterol production?

Answer 25

3-hydroxy-3-methylgluatryl-coenzyme A reductase

Question 26

Free cholesterol is toxic, so there are two enzymes that esterify it:

Answer 26

1. Plasma LCAT 2. Cellular acylcholesterol acyltransferase

Question 27

LDL expresses what class of apolipoproteins?

Answer 27

B

Question 28

How do cholesterol esters enter cells?

Answer 28

Receptor-mediated endocytosis of lipoprotein fragments

Question 29

Ddx for hypercholesterolemia

Answer 29

1. Increased production in liver
   
   1. Nephrotic syndrome
   2. PLN
2. Incrased production in enterocytes
   
   1. Post-prandial hyperlipidemia
3. Decreased lipolysis or intravascular processing of lipoproteins
   
   1. Hypothyroidism
   2. Nephrotic syndrome or PLN
4. Lipoprotein lipase deficiency
5. Other unknown mechnisms:
   
   1. Acute pancreatitis
   2. Obstructive cholestasis
   3. DM
   4. Excess GCs
   5. Hypercholesterolemia in briards
   6. Idiopathic hyperlipidemia in miniature schnauzers

Question 30

Ddx for high HDL

Answer 30

1. Decrease or absent cholesterol ester transfer activity (transfers cholesterol from HDL to LDL

Question 31

High HDL ___ susceptibility to athrogenesis.

Answer 31

decreases

Question 32

Chylomicron formation peaks ____ after eating, and is cleared ____ after eating.

Answer 32

2-6 hours

8-16 hours

Question 33

Postprandial hyperlipidemia increases TG and cholesterol. T/F

Answer 33

True - but not always cholesterol

Question 34

List ddx for primary or familial hyperlipoproteinemia (congenital defects in lipoprotein metabolism )

Answer 34

1. Idiopathic hyperlipidemia of miniature schnauzers
   
   1. Increase in both TG and cholesterol
2. Hyperlipidemia in a Brittany dog
   
   1. increase in TG, but NOT cholesterol
3. Primary hyperchylomicronemia in cats: type III LPL deficiency
   
   1. Increase in TG but NOT cholesterol
4. Hypercholesterolemia in briards
   
   1. Normal TG, but HIGH cholesterol

Question 35

List ddx for secondary hyperlipoproteinemia (acquired disorder from damaged cells or abnormal hormonal activity)

Answer 35

1. Acute pancreatitis
2. Obstructive cholestasis
3. Diabetes mellitus
4. Hypothyroidism
5. Hyperadrenocorticism in dogs
6. Nephrotic syndrome and PLN
7. Equine hyperlipemia

Question 36

Pancreatitis can cause obstructive cholestasis. T/F

Answer 36

True

Question 37

Obstructive cholestasis can cause increases in cholesterol and triglycerides. T/F

Answer 37

False - it may cause hypercholesterolemia but should NOT increase plasma triglyceride content

Question 38

Mechanisms for hypercholesterolemia d/t obstructive cholestasis

Answer 38

1. Decreaed biliary excretion
2. In mice, increased bile acid synthesis induces increased synthesis of cholesterol
3. Defective uptake of LDL (found increased LDL levels in dogs experimentally)

Question 39

This disease process is associated with unique lipoproteins that have cathodal electrophoretic migrations (lipoprotein X1, X2, X3).

Answer 39

Obstructive choelstasis

Unclear why they form, but may be due to interaction between plasma lipids and bile acids, or due to decrease in LCAT activity

Question 40

Lipoproteins X1, X2, X3 are found in patients with obstructive cholestasis. Their lipid content is mostly of ____ and non-esterified ____. Their protein content is mostly of ____ within the core apoplipoprotein ___ on the surface.

Answer 40

phospholipids

cholesterol

albumin

apoplipoprotein C

Question 41

Mechanisms of hyperlipoproteinemia due to diabetes mellitus

Answer 41

1. Decrease in insulin –> defective LPL activity –> decreased clearance of circulating lipoproteins
2. Increase in hormone sensitivite lipase activity in adipocytes (due to the fact that cells can’t utilize circulating glucose) –> mobilization of bod lipids –> influx of free FAs into liver –> FA oxidation leads to excess acetyl-coA –> promotes TG, cholesterol, and ketone production
3. Increased synthesis of HDL in intestinal mucosa

Question 42

Approximately 90% of dogs with Cushing’s disease have fasting hypercholesterolemia +/- hypertriglyceridiemia. T/F

Answer 42

True

Question 43

Mechanisms of hyperlipoproteinemia d/t hyperadrenocorticism in dogs

Answer 43

1. Indirect effect: increased GC activity can lead to DM or steroid hepatopathy
2. Direct effects:
   
   1. GC stimulates VLDL synthesis
   2. GC liberates FAs from adipose tissue –> influx of FFAs into liver –> acetylcoA –> stimulates production of TG and cholesterol –> increase in VLDL
   3. GCs antgonize actions of insulin –> decreased LPL activity –> decreased clearance of circulating lipoproteins

Question 44

Mechanisms for hypercholesterolemia d/t nephrotic syndrome and PLN

Answer 44

1. Exact mech. unknown, but many are at play
2. Thought that there is loss of a protein needed for LPL binding to endothelial cells or for normal LPL activity; or loss of proteins/enzymes needed in lipid metabolism
3. Good evidence to support defective lipolysis of lipoproteins that contain lipoprotein B (chylomicrons, VLDL, IDL, and LDL - all liporpoteins except HDL)

Question 45

Equine hyperlipemia is a primary disorder due to congenital defects. T/F

Answer 45

False - it is a secondary disroder (NOT familial) and thought to be secondary to metabolic disorders that alter lipoprotein metabolism:

• Anorexia (physiologic or pathologic mobilization of FAs from adipocytes –> stimulates VLDL synthesis)
• Obesity
• Lactation –> increase in progesterone –> stimualtes GH –> insulin receptor and post-receptor defects –> insuline resistance
• Renal failure
• Endotoxemia
• Other states creating neg. energy balance

Question 46

Ddx for hypocholesterolemia:

Answer 46

1. Decreased production: PSS, PLE
2. Hypoadrenocorticism
   
   1. Cortisol influences lipoprotein metabolism, complete mechanisms unknown

Question 47

What are the interferences when measuring cholesterol? Are they negative or positive?

Answer 47

Negative interferences include: high bilirubin and high ascorbic acid

*can add ascorbic oxidase to mitigate effects hypercholesterolemia on other measurands

Question 48

In a ____ sample, majority of TGs are within lipoproteins that were produced in the liver.

In a _____ sample, majority of the TGs are within chylomicrons assembled in enterocytes.

Answer 48

Fasting

Post-prandial

Question 49

More correct name for triglyceride:

Answer 49

Triacylglycerol

(three fatty acids “triacyl” and “glycerol” backbone)

Question 50

Method of TG measurement

Answer 50

Lipase liberates glycerol –> measure glycerol with coupled rxns via spectrophotometry

Question 51

Please label the different bands and their associated lipoproteins, starting from origin and moving towards the anode.

Answer 51

1. Chylomicron
2. Beta-lipoprotein –> LDL
3. Pre beta-lipoprotein –> VLDL
4. alpha lipoprotein –> HDL

*alpha - a for being closest to anode

Question 52

Lipoprotein electrophoresis is a qualitative method that can be used to detect dyslipoproteinemic patterns.

Increases in alpha-bands in dogs indicates ______

Increases in beta-bands in dogs indicates _____

Answer 52

Hypercholesterolemia (alpha bands)

Hypertriglyceridemia (beta bands)

Question 53

Lipoprotein electrophoresis is a reliable method for measuring lipoproteins. T/F

Answer 53

False - recommended to use in combination with density fractionation or to simply monitor response to therapy becuase it doesn’t correctly label bands - not all lipoproteins of the same class have the same density)

Question 54

NEFAs and glycerol from hydrolysis of _______ in adipose tissue, liver, and mammary tissue.

Hydrolysis is mediated by lipase. Lipase is stimualted by _____ and ____ and inhibited by _____.

Answer 54

triacylglycerol

Epinephrine and glucagon

Insulin

Question 55

NEFAs are measured via enzymatic colorimetric assay, which detects ________, but does NOT detect _______.

Answer 55

Detects medium and long-chain fatty acids

Does not detect volatile FAs (e.g., propionic acid, butyric acid)

Question 56

Increased NEFAs are a sign of ______ in cattle.

Answer 56

negative energy balance

Question 57

Ddx for increased NEFAs:

Answer 57

1. DM
2. Hepatic lipidosis
3. Over-feeding
4. Obesity
5. Food deprivation
6. Post-exercise

Question 58

NEFAs are measured mostly in ruminants before feeding and ____ days before calving.

Answer 58

2-14 days

Question 59

Pre-parturient cows with increased _____ correlate with post-parturient Ketosis, displaced abomasums, and fatty liver.

Answer 59

NEFAs

Question 60

Standing plasma test for chylomicrons is a test that puts a sample of plasma in the fridge for 16 hours, and confirms presence of chylomicrons is there is a cream top, but this is an unreliable test. What other tools are better to measure chylomicrons?

Answer 60

Ultracentrifugation and lipoprotein electrophoresis