Hyperlipidemia - Sinal 3

Question 1

Chylomicrons

Answer 1

Least dense
Mostly triglycerides
Important in energy storage and transport
Produced in intestine form dietary lipids
Fatty acids are released using lipoprotein lipase mediated lipolysis
Remnant is taken up by liver by receptor mediated endocytosis

Question 2

LDL

Answer 2

Low density lipoproteins
Mainly cholesterol
Retain most of cholesterol originally presented in VLDL
Majority of circulating cholesterol
Primary means of delivery of cholesterol to peripheral tissues
Uptake achieved by LDL receptor mediated endocytosis
Bad cholesterol

Question 3

HDL

Answer 3

High density lipoprotein
Almost half protein
Secreted by liver as immature
Mature by requiring lipid (primarily cholesterol) from VLDL and chylomicrons and acquiring cholesterol from peripheral tissues
Can transport cholesterol back to the liver via scavenger receptor BI mediated uptake
Good cholesterol

Question 4

Lipoprotein lipase

Answer 4

Enzyme that converts parts of chylomicrons into FAs

Question 5

Cholesterol biosynthesis

Answer 5

Multiple steps
HMG-CoA reductase is rate limiting 
Major site is liver
Cholesterol is precursor for the biosynthesis of several essential commands
Acetyl CoA -> HMG-CoA -> Cholesterol

Question 6

Cholesterol catabolism

Answer 6

End product are bile acids
Major site is liver
Bile acid biosynthesis is important means of cholesterol removal from the liver and body
Emulsifies chylomicrons and bile is reabsorbed and retired to the liver

Question 7

VLDL

Answer 7

Very low density lipoproteins
Triglyceride rich
Second lower density lipoprotein
Secreted by liver to transport lipids to other tissues
Hydrolyzed by LPL on capillary surface of peripheral tissues to release fatty acids
Remnant can be converted to LDL in blood by removal of some apolipoproteins and lipolysis of the remaining triglyceride

Question 8

Type IIa hyperlipoproteinemias

Answer 8

LDL
Increased cholesterol
Familial, polygenic or sporadic
Decreased LDL receptor expression/function

Question 9

Type IIb hyperlipopoetinemias

Answer 9

LDL and VLDL
Increased cholesterol and triglycerides
Familial, combined and sporadic
Decreased LDL receptor expression/function and/or increased VLDL secretion

Question 10

Athersclerosis

Answer 10

Reduction in blood flow leading to increased risk for CVD, stroke, kidney failure and other clinical events
Consequent of aging
Risk factors: hypertension, elevated blood lipids, smoking, hyperglycaemia, obesity, infection and inflammation

Question 11

Macrophage foam cell formation

Answer 11

Critical early event in pathology of atherosclerosis
Initiated by injury to vessel endothelial layer
Allows LDL penetration to vessel anima, where it is oxidized
Inflammatory cells are recruited to site of injury, macrophages take up the oxidized LDL
Cholesterol from the LDL is stored inside the macrophage as cholesterol esters, which can be removed by efflux to HDL (ABCA1 transporter mediated)
Excessive cholesterol ester accumulation in macrophages can lead to foam cell formation

Question 12

Foam cell death

Answer 12

Release of cholesterol esters into intimate
Release of pro-inflammatory cytokines
Propagation and amplification of inflammatory response
Formation of necrotic core, fibrosis, plaque formation and obstruction of blood vessel (advanced)

Question 13

Risk of atherosclerosis

Answer 13

Positive with LDL, total cholesterol, and LDL:HDL

Negative with HDL

Question 14

Therapeutic lifestyle changes

Answer 14

TLCs

Diet, exercise, stop smoking, stop alcohol

Question 15

Statins

Answer 15

Drug of choice for patients with LDL
Competitive inhibitors of HMG CoA reductase
Increases hepatocyte LDL receptor levels, increasing uptake of LDL in liver (indirect effect of inhibiting cholesterol biosynthesis)
Anti-inflammatory, anti-coagulant
Reduce risk of death
Limited benefit for Type IIa familial (due to LDL receptor mutation)

Question 16

Adverse effects of statins

Answer 16

Reversible liver toxicity
Cardiomyopathy
Drug interactions

Question 17

Niacin

Answer 17

Water soluble vitamin, B3
Inhibits lipolysis in adipose tissue causing reduction of circulating FA-reduced hepatic triglyceride biosynthesis, reduced hepatic VLDL synthesis/secretion, reduced serum LDL
Reduced plasma LDL cholesterol, and total plasma, effective in combination with other drugs
Clinical use is limited by requirement for high doses and adverse effects

Question 18

Adverse effects of niacin

Answer 18

Flushing, hot flashes, GIT irritation, hepatotoxicity

Question 19

Bile-acid binding resins

Answer 19

Anion exchange resins that bind bile acids in the small intestine
Complex is excreted in the feces
Reduced bile acid reabsorption from intestine/return to liver, intracellular bile acid levels leading to increased bile acid synthesis and reduction of cholesterol stores
Increased expression of LDL receptors, hepatic LDL uptake
Lower LDL blood levels
Safe and effective
Do not interfere with absorption of dietary lipids/lipid soluble vitamins with moderate doses
Combination therapy with statins is common

Question 20

Cholesterol absorption inhibitors

Answer 20

Ezetimibe
Newest class
Inhibit cholesterol absorption from small intestine (exogenous and endogenous)
Deplete hepatic cholesterol (increase LDLR expression)
Used with other drugs, as limited benefit with mono therapy
Common with statin
No clinical trials yet prove evidence for decrease in CVD

Question 21

Fibrates

Answer 21

First choice for patients with elevated serum triglycerides and/or reduced HDL
PPARalpha agonists
Reduce plasma triglycerides
Increasing chylomicron and VLDL clearance, reduced hepatic VLDL synthesis/secretion, promotes reverse cholesterol transport, anti-inflammatory
Generally well tolerated
(GIT irritation, liver toxicity, rash, cardiomyopathy)

Question 22

PPARalpha

Answer 22

Ligand-activated TF that increases the expression of genes involved in lipid metabolism
Endothelial lipoprotein lipase
Hepatic fatty acid oxidation enzymes
Hepatic apo A1 and A2 (principle protein compartments of HDL)

Question 23

Type IIa clinical approach

Answer 23

TLC, statins, resins, ezetimide

Alone or combination

Question 24

Type IIb clinical approach

Answer 24

TLC, statins, resins, exetimide, niacin, vibrates

Alone, combination

Question 25

Familial Type IIa

Answer 25

Gene defects in the LDL receptor gene
Elevated total cholesterol and LDL
Heterozygotes some response to statins or bile acid binding resins, combination are more effective
Homozygotes appear from childhood
Minimal effect of statins, resins and combinations
TLC and niacin are most effective