Session 2- Lipid Transport Flashcards
how are lipids carried around the body
2% carried bound to albumin but this a limited capacity
98% carried are lipoprotein particles consisting of phospholipids, cholesterol, cholesterol esters, proteins and TAG
typical lipid range in blood
4000 - 8500 mg/L
what are the 2 types phospholipids
choline- phosphatidylcholine
inositol- phosphatidylinositol
what steriod hormones is cholesterol the precursor of
cortisol
aldosterone
testosterone
oestrogen
what does the lipoprotein cargo consist of
triacylglycerol
cholesterol ester
fat soluble vitamins
what the 5 lipoproteins
chylomicrons VLDL IDL LDL HDL
what are the main carriers of fat
chylomicrons
VLDL
what are the main carriers of cholesterol esters
LDL
IDL
HDL
Order the lipoproteins in order of most dense to least
HDL
LDL
IDL
VLDL
What are the roles of apolipoproteins
structural: packaging water insoluble lipids
functional: co-factor for enzymes
ligands for cell surface receptors
function of LDL
provide cholesterol from liver to peripheral tissues
peripheral cells express LDL receptor and take up LDL via receptor mediated endocytosis
transport of cholesterol synthesised in liver to tissues
why is LDL more susceptible to oxidative damage
it has a longer half life than VLDL or IDL
how does LDL enter cells
LDL receptors/ LDL complex taken into cell by endocytosis into endosomes
fuse with lysosomes for digestion to release cholesterol and fatty acids
LDL-R expression controlled by cholesterol concentration in cell
how is HDL synthesised
nascent HDL synthesised by liver and intestine
HDL particles can also bud off from chylomicrons and VLDL as they are digested by LDL
Free apoA-I can also acquire cholesterol and phospholipid from other lipoproteins and cell membranes to form nascent-like HDL
chylomicrons function
transport dietary TAG from intestine to tissues such as adipose tossue
VLDL function
transport of triacylglycerol synthesised in liver to adipose tissue for storage
IDL function
short-lived precursor of LDL. Transport of cholesterol synthesised in the liver to tissues
HDL function
transport of excess cholesterol from cells to liver for disposal as bile salts and to cells requiring additional cholesterol
what is hyperlipoproteinaemia
raised plasma level of one or more lipoprotein class
caused by
-over production
-under removal
defects in
- enzymes
- receptors
- apoproteins
clinical signs of hypercholeserolaemia
high levels of cholesterol in blood cholesterol depositions in various areas of body Xanthelasma-yellow patches tendon xanthoma- nodules corneal arcus- white circle around eye
how is raised serum levels associated with artheroscelrosis
oxidised LDL
recognised and engulfed by macrophages
macrophages turn into foam cells
foam cells accumulate in intima of blood vessels
fatty streak can evolve into artherosclerotic plaque
grows and enroaches the lumen of the artery causing angina
the blood vessels could rupture and trigger acute thrombosis causing an MI or stroke
how do you treat hyoerlipoproteinaemia
diet- reduce cholesterol and saturated lipids and increase fibre intake
lifestyle- exercise and stop smoking
statins- reduce cholesterol synthesis by inhibiting HMG-CoA reductase
bile salt sequestrants- bind bile salts in GI tract. Forces liver to produce more bile acids using more cholesterol
statins mechanism if action
they inhibit HMG-CoA reductase which usually converts HMG-CoA formed from acetyl-CoA to mevalonate which forms cholesterol
what is PKU
phenylketonuria- deficiency in phenylalanine hydroxylase causes phenylalanaine to be converted into phenylpyruvate which is converted into phenylacetate and phenyllactate (phenylketones)
autosomal recessive
accumulation of phenylalanine in tissues, plasma and urine]
phenylketones in urine
musty smell
