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Cardiovascular > Pharmacology- Cholesterol > Flashcards

Pharmacology- Cholesterol Flashcards

1
Q

are lipids soluble in water

A

insoluble or sparing soluble in water

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2
Q

what are lipids essential for

A

membrane biogenesis and membrane integrity, energy sources, precursors for hormones and signalling molecules

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3
Q

what are two examples of non polar lipids

A

cholesterol esters and triglycerides

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4
Q

how are non polar lipids transported within the blood

A

within lipoproteins (e.g. HDL and LDL (high/low density)

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5
Q

what ratio of HDL and LDL is cardiovascular disease associated with (atherosclerosis)

A

elevated LDL and decreased HDL

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6
Q

what are the causes of a high LDL to HDL ratio

A

diet and lifestyle (western), genetic factors

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7
Q

what does the synthesis of all steroid hormones start with

A

cholesterol

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8
Q

describe the structure of lipoproteins

A

7-1000 nM in diameter, hydrophobic core and hydrophilic core

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9
Q

what does the hydrophobic core of lipoproteins contain

A

esterified cholesterol and triglycerides

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10
Q

what does the hydrophilic coat of lipoproteins contain

A

monolayer of amphipathic cholesterol, phospholipids and one/more apoproteins

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11
Q

what are the 4 major lipoproteins

A

HDL, LDL, VLDL (very low density), chylomicrons

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12
Q

what apoproteins do HDL particles contain

A

apoA1 and apoA2

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13
Q

what apoproteins do LDL particles contain

A

apoB-100

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14
Q

what apoproteins do VLDL particles contain

A

apoB-100

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15
Q

what apoproteins do chylomicrons particles contain

A

apoB-48

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16
Q

where do ApoB-containing lipoproteins deliver triglycerides to (2)

A

1- muscle for ATP biogenesis

2- adipocytes (fat cells) for storage

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17
Q

describe the exogenous pathway

A

Chylomicrons are formed in intestinal cells and transport dietary triglycerides

involves the absorption, distribution and delivery of lipids from diet to the periphery tissues

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18
Q

describe the endogenous pathway

A

VLDL particles are formed in liver cells and transport triglycerides synthesised in the liver

involves lipid synthesis by liver and delivery to peripheral tissue via VLD lipoproteins

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19
Q

describe the life cycle of apoB-containing liposomes

A

1- assembly; apoB100 (liver) and apoB48 (intestine)

2- intravascular metabolism; (ivloves hydrolyses of triglyceride core)

3- receptor mediated clearance

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20
Q

(assembly of chylomicrons)

what breaks down dietary fat first and where

A

lipases in the intestine (formed in the pancreas)

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21
Q

(assembly of chylomicrons)

what is dietary fat broken down into to enter the cells lining gut lumen (via diffusion)

A

monoglyceride and free fatty acid (long chain)

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22
Q

(assembly of chylomicrons)

what happens when the monoglyceride and free fatty acid chain are within the cell

A

triglyceride synthesis

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23
Q

(assembly of chylomicrons)

how is cholesterol transported into the cell

A

via Niemann-Pick C1-like 1 protein

NPC1L1

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24
Q

(assembly of chylomicrons)

what happens to cholesterol once it is inside the cell

A

esterification to make cholesteryl ester

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25
Q

what is an enterocyte

A

cell of the intestine lining

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26
Q

(assembly of chylomicrons)

what does cholesteryl ester eventually form

A

apoB48

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27
Q

(assembly of chylomicrons)

what is the apoB48 produced in enterocytes added to

A

triglyceride droplets within cell

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28
Q

what is lipidation

A

the addition of hydrophobic molecules to a protein or chemical compound

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29
Q

(assembly of chylomicrons)

how what are the final stages of chylomicron formation

A

lipidation (assisted with MTP), and addition of cholesteryl ester and apoA1

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30
Q

(assembly of chylomicrons)

how does the chylomicron exit the cell and where does it go

A

exits via exocytosis and enters the lymphatics where it is carried in lymph to systemic circulation (subclavian vein) via the thoracic duct

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31
Q

where are VLDL particles assembeled

A

in liner hepatocytes

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32
Q

what are VLDL particles synthesised from

A

from free fatty acids from adipose tissue and de novo synthesis

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33
Q

what is the role of MTP in the assembly of VLDL particles

A

MTP lipidates apoB100 forming nascent VLDL that coalesces with triglyceride droplets

34
Q

how are chylomicrons and VLDL particles activated (to deliver adipose and muscle tissue

A

the transfer of apoCII from HDL particles into the shell of VLDL and chylomicron particles

35
Q

what is the role of HDL

A

mops up excess cholesterol in the blood and carry it to the liver where it is secreted in bile

36
Q

what does the transfer of apoCII facilitate

A

facilitates binding of chylomicrons and VLDL particles to LPL

37
Q

what is LPL

A

Lipoprotein lipase (LPL) – lipolytic enzyme associated with the endothelium of capillaries in adipose and muscle tissue

38
Q

how does LPL act on VLDL and LPL

A

LPL hydrolyses core triglycerides to free fatty acids and glycerol which enter tissues

39
Q

what are chylomicron and VLDL remnants

A

Particles depleted of triglycerides (but still containing cholesteryl esters)

40
Q

what happens to apoCII after VLDL and chylomicrons dissociate from LPL

A

ApoCII is transferred to HDL particles in exchange for apoE. particles are now remnants

41
Q

what is apoE

A

a high affinity ligand for receptor mediated clearance

42
Q

where do the VLDL anf chylomicrons return to and what happens

A

return to liver and are further metabolised by hepatic lipase

43
Q

what are all apoB48 containing remnants and 50% of all apo100 containing remnants cleared by

A

receptor-mediated endocytosis into hepatocytes

44
Q

what happens to the remaining 50% of apoB100 containing lipoproteins not cleared by receptor mediated endocytosis

A

remnants loose further triglyceride through hepatic lipase, become smaller and enriched in cholesteryl ester and via intermediate density lipoproteins (IDL) become LDL particles lacking apoE and retaining solely apoB100

45
Q

what is clearance of LDL dependant on

A

LDL receptor expression by the liver and other tissues (liver most important)

46
Q

how does cellular uptake of LDL occur via

A

via receptor-mediated endocytosis

47
Q

what is endocytosis

A

process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell.

48
Q

whats a lysosome

A

little enzyme package (organelle)

49
Q

describe the release of cholesterol within the cell

A

released from cholesteryl ester (CE) at the lysosome via hydrolysis

50
Q

what does released cholesterol cause

A

inhibition of HMG-CoA reductase which is the rate limiting enzyme in de novo cholesterol synthesis

down regulation of LDL receptor expression

storage of cholesterol as cholesterol ester

51
Q

what do statins do

A

block the synthesis of cholesterol in the liver cell and thus increase surface expression of LDL receptors, therefore LDL cells more readily cleared form the plasma

52
Q

what happens to LDL after it is taken into the endothelium of the artery from the blood

A

LDL is oxidised to atherogenic oxidised (OXLDL)

53
Q

what initiates atherosclerosis

A

dysfunction and injury of the lining of blood vessels

54
Q

describe the formation of fatty streaks in endothelium

A

monocytes migrate to across the endothelium into the intima where they become macrophages and uptake OXLDL and convert them to cholesterol-laden foam cells that form a fatty streak

55
Q

what is a fatty streak a sign of

A

early event in atherosclerosis

56
Q

describe the formation of an atheromatous plaque

A

release of inflammatory substances from various cell types causing division and proliferation (rapid increase in number) of smooth muscle cells in the intima and the deposition of collagen

57
Q

describe the composition of an atheromatous plaque

A

a lipid core (product of dead foam cells) and a fibrous cap (smooth muscle cells and connective tissue)

58
Q

why is HDL the good cholesterol

A

has a key role in removing excess cholesterol from cells by transporting it in plasma to the liver (reverse cholesterol transport)

59
Q

where is HDL mainly formed

A

in the liver

60
Q

in the plasma what mediates the transfer of cholesteryl esters indirectly returning cholesterol to the liver

A

cholesterol ester transfer protein (CETP)

61
Q

what causes primary dyslipidaemia

A

combination of diet and genetic factors

62
Q

what causes secondary dyslipidaemia

A

is a consequence of other diseases

63
Q

what is dyslipidaemia

A

abnormal amount of lipids

64
Q

what is the drugs of choice to reduce LDL

A

statins

65
Q

give 2 example of statins

A

simvastatin and atorvastatin

66
Q

what do statins act on and how

A

Act as competitive inhibitors of HMG-CoA reductase (limiting step in cholesterol synthesis in hepatocytes

67
Q

how do statins reduce LDL levels

A

as decrease in hepatocyte cholesterol synthesis causes a compensatory increase in LDL receptor expression and enhanced clearance of LDL

68
Q

what are other beneficial effects of statins

A

Decreased inflammation

Reversal of endothelial dysfunction

Decreased thrombosis

Stabilization of atherosclerotic plaques

69
Q

how are statins administered

A

orally at night

70
Q

what do fibrates do

A

caused pronounced decrease in triglycerides and modest decreases in LDL and HDL

71
Q

what are two examples of fibrates

A

bezafibrate and gemfibrozil

72
Q

what are fibrates used to treat

A

very high triglyceride levels

73
Q

how do fibrates act

A

as agonists of a nuclear receptor (PPARalpha) to enhance the transcription of several genes, including that encoding LPL

74
Q

what adverse effect can statins and fibrates cause

A

myositis

75
Q

give three examples of drugs that inhibit cholesterol absorption

A

colestyramine, colestipol, colsevelam

76
Q

describe how bile acid binding resins work to inhibit cholesterol absorption

A

) cause the excretion of bile salts resulting in more cholesterol to be converted to bile salts by interrupting enterohepatic recycling

77
Q

what do binding resins cause

A

decreased absorption of triglycerides

increased LDL receptor function

78
Q

what is ezetimibe

A

acts to inhibit NPC1L1 transport protein in enterocytes of the duodenum, reducing the absorption of cholesterol

79
Q

what types of cholesterol does ezetimibe affect

A

decreases LDL but doesn’t really affect HDL

80
Q

describe the administration of ezetimibe

A

used in combo with statins when statins not enough. Not in breastfeeding females

Cardiovascular (34 decks)

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