Dietary Fats and Blood Lipids Flashcards
what are lipids?
group of organic substances soluble in organic solvent and virtually insoluble in water
what are the 3 main classes of lipids?
cholesterol
triglycerides
phospholipids
why is it important cholesterol allows the synthesis of bile acids?
allows absorption of fat soluble vitamins (A,D,E,K)
what is the role of cholesterol?
-component of all cell membranes
-synthesis of bile acids
-precursor for endogenous Vit D production
-precursor for steroid hormones
which steroid hormones is cholesterol a precursor for?
-oestrogen and progesterone
-testosterone
-cortisol
-aldosterone
what is the use of triglycerides?
used as an energy source in tissues
used for energy storage in adipose tissue
essential role but too much can increase risk of heart disease
what is a lipoprotein?
-complex spherical structure
-central core of hydrophobic lipids (triglycerides and cholesterol esters)
-surface layer of polar components (phospholipids, free cholesterol, proteins- the apolipoproteins)
what is the lipoprotein system?
evolved to solve the problem of transporting fats in the aqueous environment of plasma
what are the types of lipoprotein found in the body? (least dense to most dense)
-chylomicron
-VLDL
-LDL
-HDL
what is the function of chylomicron?
synthesised in then gut after a meal
main carrier of dietary triglyceride
what Is the function of VLDL?
synthesised in the liver
main carrier of endogenously produced triglyceride
what is the function of LDL?
generated from VLDL in the circulation
main carrier of cholesterol
what is the function of HDL?
returns cholesterol from ectrahepatic tissues to the liver for excretion
what are apolipoproteins?
-amphiphilic compounds
-hydrophobic region interacting with lipid core
-provides structure to the lipoprotein
-hydrophilic region interacting with aqueous environment
what is the role of apolipoproteins?
play a crucial role in lipid metabolism
-guiding the formation of lipoproteins
-acting as ligand for lipoprotein receptors
-sering as activators or inhibitors of enzymes involved in the metabolism of lipoproteins
which apoprotein binds with LDL receptors to allow cholesterol to get inside the cells?
APOB100
what happens during the exogenous cycle?
-food is ingested and dietary lipid is absorbed
-goes into the circulation as chylomicron (big and fluffy)
-acted on by lipoprotein lipase to form chylomicron remnants which are then taken up by the liver
what connects the exogenous and endogenous cycles?
liver
what is cardiovascular disease?
circulation - ischaemic heart disease (angina, myocardial infarction
cerebral circulation - stroke
peripheral circulation - peripheral vascular disease
premature CVD - males onset CVD<55, females onset CVD<65
what happens during the endogenous cycle?
liver produces very LDL particles
-relessed into circulation
-broke into IDL
-broke down further into LDL
-can either circulate back and be taken up by LDL receptors in liver or extra hepatic cells
what happens when there is too much LDL or LDL is oxidised (those who smoke)?
oxidised LDL taken up more readily by scavenger cells or macrophages and result in the laying down of fatty plaques in the arteries
what is the criteria for individuals who are known to be at high risk of CVD?
-those already diagnosed
-chronic kidney disease (stage 3+)
-diabetics >40 or with >20 years with the disease
-evidence of diabetes related organ damage
-those with familial hypercholesterolaemia
what are some diabetes related organ damage examples?
eyes - retinopathy
kidneys - proteinuria
nerves - autonomic neuropathy
what results can we get from a lipid profile?
-cholesterol
-triglycerides
-HDL cholesterol
-LDL cholesterol
-VLDL cholesterol
-Chol/HDL ratio
which cholesterol is lowered by drugs we use?
LDL
how much energy does fat contain?
9kcal
what kinds of food are high in saturated fat?
pastry
coconut oil
hard cheese
soured cream
what kind of foods are high in mono-unsaturated fat?
avocado
olives
rapeseed oil
walnuts
what kind of foods are high in poly-unsaturated fat?
salmon
rapeseed oil
walnuts
what are the 3 main lipids carried in the blood stream?
triglycerides
cholesterol
phospholipids
how are lipids transported in the blood and why?
carried in lipoproteins as they are insoluble in blood and water
where is HDL and VLDL synthesised?
mainly in the liver
where is chylomicron mainly synthesised?
gut after eating
where is LDL synthesised?
generated from VLDL In circulation
what is HDL?
protective- takes cholesterol from tissues to liver for extraction
what is the function of VLDL?
carry triglyceride from liver to skeletal muscle
what is the function of LDL?
carry cholesterol from liver (via VLDL) to tissues
what is the function of chylomicron?
carry dietary fat from gut to adipose tissue and muscle
where is cholesterol absorbed in the GI tract?
small intestine
what enzyme hydrolyses VLDL to form IDL?
lipoprotein lipase
how can LDL be removed from the circulation?
b high affinity LDL receptors into cells or by scavenger routes (when LDL levels are high) into macrophages leading to atheromatous plaques
what happens to the risk of CHD as total cholesterol concentrations increase?
total cholesterol - higher CHD risk is associated with increasing total cholesterol
HDL cholesterol - higher HDL is associated with lower CDH risk
triglycerides - high triglyceride levels are associated with higher CHD risk
what is the mechanism of CHD?
-high conc of LDL, LDL particles more likely to become oxidised and taken up at a fast, uncontrolled rate by scavenger receptors on macrophages
-this leads to formation of foam cells which develop into fatty streaks and subsequently atheromatous plaques leading to narrowing of the coronary arteries
what is the HDL and CHD risk?
HDL is involved in the reverse cholesterol pathway. It carries cholesterol from tissues back to the liver where it is excreted. Thus, there is less cholesterol in the blood to become oxidised, leading to fewer foam cells and atherosclerotic plaques
what is the triglycerides and CHD risk?
High triglyceride levels lead to low HDL concentrations. High triglyceride levels are associated with small, dense LDL particles which are more susceptible to oxidation. The end products of triglyceride-rich lipoproteins can damage the endothelial lining in the arteries, promoting deposition of cholesterol in the artery walls.
a patient has a triglyceride level of 14mmol/L what condition are they at risk of?
pancreatitis
do triglyceride levels increase or decrease after eating?
higher
what is the target cholesterol level after a heart attack?
<3mmol/L
what type of fat can increase blood LDL cholesterol concentrations?
saturated
what risk calculators can be used to help estimate CV risk?
ASSIGN, QRISK3
