Investigation and risk factors for ischaemic heart disease and myocardial infarction (2) Flashcards
What are lipids?
Lipids are organic biomolecules which are soluble in NON-POLAR
solvents and much less soluble in water
What are major lipids in the plasma?
Fatty acids (FA)
Triacylglycerols (triglycerides) (TG or TAG)
Cholesterol
Phospholipids
What is a more efficient storage of energy: triacylglycerols or glycogen
triacylglycerols
Where is triacylglycerols formed?
Liver
Adipose tissue
Where do triacylglycerols come from?
Metabolites from glycolysis (DHAP — dihydroxyacetone phosphate) form TAGs in the FED state
How are triacylglycerols broken down- into what?
Breakdown of TAGs is the first stage in fatty acid metabolism, resulting in release of FFA (free fatty acids)
How is ATP derived from triacylglycerols
Resultant fatty acids then undergo B-oxidation and ATP production
What keeps the metabolism of triacylglycerols regulated?
triglyceride lipase
How is cholesterol synthesised?
Acetyl CoA -> HMG CoA (Intermediate)- Mevalonate
Where is cholesterol synthesised?
Liver
How is the synthesis of cholesterol regulated
HMG CoA Synthase
HMG CoA Reductase
How do statins affect synthesis of cholesterol
statin is an HMG-CoA reductase inhibitor
stops the liver from synthesizing cholesterol
How do lipids travel around the body?
Lipoproteins
What is the lipoprotein made of structurally?
Surface coat
Lipid core
What is contained in the surface coat of the lipoprotein
unesterified cholesterol
phospholipids
apolipoproteins
What is contained in the lipid core of the lipoprotein
cholesteryl esters
triglycerides
What is the role of apolipoproteins
Signals which lipoproteins it is
What are the types of lipoproteins?
Chylomicrons VLDL IDL LDL HDL
What is Chylomicrons mostly made of? least made of?
Triglyceride- H
Protein-L
What is HDL mostly made of? least made of?
Triglyceride- L
Protein-H
What is LDL mostly made of? least made of?
Cholesterol- H
Triglyceride-L
What is chylomicrons a major transport form of?
Dietary fat being absorbed from the gut
What is the chylomicrons transport pathway also known as?
Exogenous pathway
What percentage of triglycerides is in chylomicrons?
90%
How is triglyceride removed from chylomicrons?
Lipoprotein lipase
What does chylomicrons transport?
cholesterol and fat-soluble vitamins Dietary fat
What is chylomicron metabolism(exogenous pathway)?
Fat broken down into triglycerides so forms chylomicron
triglyceride released from it by lipoprotein lipase
Gets smaller becomes a chylomicron remnant and cholesteryl esters is added
Cleared by liver from circulation and excreted into the bile
In the chylomicron metabolism where does the cholesteryl ester come from?
HDL
What is the VLDL metabolism known as?
Endogenous pathway
What is VLDL a major transport form of?
Endogenous triglyceride
Where is VLDL formed?
Liver
How is triglyceride removed from VLDL?
Lipoprotein lipase
VLDL metabolism?
Triglyceride removed by Lipoprotein lipase to make IDL
More triglyceride removed with hepatic triglyceride lipase to form LDL
LDL taken up by liver through LDL receptors or can be transported to peripheral tissues
How is LDL made?
From VLD via IDL
How does LDL contribute to atherosclerosis?
Binds to LDL receptors on cell membranes — then are broken down releasing cholesterol
Uptake of LDL in the arterial wall contributes to ATHEROSCLEROSIS
Where is HDL synthesised?
Liver
What is HDL initially synthesised as?
Nascent HDL
What is HDL metabolism also known as?
Reverse cholesterol transport
HDL metabolism?
Nascent HDL delivered with cholesterol from peripheral tissues to form HDL
Cholesterol esterified by Lecithin cholesterol acyl transferase
Cholesterol esters are then delivered from HDL into the chylomicron remnants
HDL returned to circulation
What does Nascent HDL look like?
flat cylinder
What are the lipid disorders that we need to know?
Familial hypercholesterolaemia
Type III hyperlipidaemia
Hypertriglyceridemia
