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Nutrition and Metabolism > Cholesterol > Flashcards

Cholesterol Flashcards

1
Q

How many carbons are in cholesterol?

A

26

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2
Q

In whose cells, is cholesterol not needed?

A

in plants and yeast

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3
Q

What do plants and yeast have, in ‘replacement’ for cholesterol?

A

sterols

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4
Q

Is cholesterol an energy source?

A

No

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5
Q

Why are there barely changes to its structure?

A

has extra double bond due to enzyme gene mutation (can be pathological)

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6
Q

What is the gene mutation for the extra double bond in cholesterol called?

A

Smith-Lemli-Opitx syndrome

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7
Q

How much of cholesterol comes from diet?

A

20-30%

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8
Q

Which organ in the body is the most cholesterol rich?

A

brain

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9
Q

Why is the brain rich in cholesterol?

A
  • makes and recycles all its own cholesterol

- BBB cant take up circulating (dietary) cholesterol

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10
Q

Examples of cholesterol in the body

A
  • steroid hormones (progesterone)
  • bile acids (cholic acid)
  • covalent addition to proteins (hedgehog)
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11
Q

What are cholesteryl esters for?

A

cholesterol storage

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12
Q

Where is cellular cholesterol from?

A
  • via endogenous synthesis
  • in endoplasmic reticulum
  • from acetyl-coA
  • regulated at HMG-CoA reductase step
  • delivery from circulation in cholesteryl ester form, in complex with LDL (then internalised and released)
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13
Q

How much cholesterol is synthesised in the liver?

A

1g/day

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14
Q

What are the main steps in cholesterol synthesis?

A
  1. 3-acetyl-coA
  2. HMG-CoA
  3. Mevalonate
  4. Isopentyl Pyrophosphate
  5. Squalene
  6. Cholesterol
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15
Q

How many pathways are there from squalene to cholesterol and what are they called?

A

Two.

  1. Bloch pathway
  2. Kandutsh-Russell pathway
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16
Q

Which pathway, bloch or kandutsh is more dominant?

A

Bloch pathway

17
Q

How is cellular cholesterol levels regulated?

A
  • synthesis OR

- LDL delivery

18
Q

What inhibits HMG-CoA reductase enzyme?

A

statins

19
Q

What is not produced when statins inhibit the HMG-CoA reductase?

A

mevalonic acid

20
Q

What is a lipoprotein?

A

protein and lipid containing particle, whose function isto shuttle lipid and lipid soluble antioxidants in the bloodstream to tissues where needed

21
Q

What are the features of a lipoprotein?

A
  • integral apoprotein
  • hydrophilic surface of phospholipids + free cholesterol
  • peripheral apoprotein
  • hydrophobic core of triacylglycerols, cholesterol esters + lipid soluble vitamins
22
Q

Where can lipoproteins be made?

A
  • liver
  • intestines
  • tissues outside
  • precursors in liver and gut
23
Q

What are the lipoproteins in circulation called? (and where were they from)

A
  • chylomicrons (gut)
  • VLDL (liver)
  • LDL/IDL (periphery)
  • HDL (precursors in liver, formed in periphery)
24
Q

What happens to most of the LDL?

A

absorbed by liver to lower serum LDL levels and reduce atherosclerosis

25
Q

What happens as a result of high dietary cholesterol?

A
  • high cytosolic cholesterol in liver cells
  • HMG-coA inhibited
  • LDL-R’s not produced, LDL not picked up
  • LDL in circulation = elevated serum LDL + atherosclerosis
26
Q

What happens in familial hypercholesterolemia?

A
  • no working LDL receptors in liver (defect)
  • LDL created stays in circulation (high levels + atherosclerosis)
  • liver produces cholesterol
27
Q

What are the protective roles of HDL?

A
  1. Stimulates macrophage cholesterol efflux
  2. Antiapoptotic
  3. Decrease expression of adhesion molecules (anti-inflammatory)
  4. Decrease LDL oxidation (antioxidative)
  5. Ameliorates endothelial function
28
Q

How does HDL remove cholesterol from cholesterol-loaded macrophages?

A

by binding to ABCA1 and stimulating process of reverse cholesterol transport

29
Q

What is the recommended UK NICE dietary intake of cholesterol?

A

less than 300mg/day

30
Q

What is the total % fat intake recommended?

A

less than 30%

31
Q

what is the recommended % saturated fats?

A

less than 7% total energy intake

32
Q

What are saturated fats recommended to be replaced by?

A

mono-unsaturated fats and polyunsaturated fats

33
Q

What is ezutimide?

A
  • blocks intestinal absorption of cholesterol
  • LDL decreases by 17-19%
  • given in combination with statin
  • but not proven so not approved by all yet
34
Q

What are the benefits of phytosterols?

A
  • reduce LDL 10% in 2 weeks
  • taken 2g/day
  • inhibits absorption of cholesterol and reabsorption of bile acids in gut
  • more cholesterol taken from circulation in liver to replace bile acids

Nutrition and Metabolism (14 decks)

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