Lipoproteins, Cardiovascular disease & drugs used to treat hyperlipidaemias Flashcards
What are lipids?
Organic compounds- poorly soluble in water but miscible in organic solvents
Why are lipids important in human physiology?
Steroids- cholesterol/ steroid hormones (testosterone) Fat-soluble vitamins- A, D, E, K Phospholipids Sphingolipids Triglycerides
How are lipids important in cardiovascular disease?
Components of lipoproteins Cholesterol (free/ esterified) Triglycerides- triacylglycerol Phospholipid monolayer apoB-100 protein
What is the purpose of lipoproteins?
Transport cholesterol and triglycerides around the body via the circulation
What are the main types of lipoprotein?
Chylomicrons Very Low Density Lipoprotein (VLDL) Intermediate Density Lipoprotein (IDL) Low Density Lipoprotein (LDL) High Density Lipoprotein (HDL)
How are lipoproteins created?
Small intestine (dietary lipids)
Liver (endogenous lipids)
To peripheral tissues
Returns to liver via reverse cholesterol transport
How can transport and metabolism of lipoproteins be divided up into three main pathways?
-Intestinal absorption (cholesterol and triglycerides)
=exogenous lipid pathways to peripheral tissues
-Hepatic synthesis (cholesterol and triglycerides)
=endogenous lipid pathways to peripheral tissues
Hepatic excretion (cholesterol and bile acids)
=from peripheral tissues via reverse cholesterol transport
Describe the exogenous lipid pathway
Triglycerides- (glycerol)+ NEFA- muscle, adipose tissue
Cholesterol- liver (chylomicron remnants)
NEFA= non-esterified fatty acids
Describe the endogenous lipid pathway
NEFA (albumin- bound)+ glucose, glycerol- liver- LDL- peripheral tissues (receptor)
VLDL- triglycerides= muscle, adipose
LDL- cholesterol= peripheral tissues
Describe the main types of lipoprotein
-Chylomicrons= biggest, mostly triglycerides
-Very Low Density Lipoprotein (VLDL)= quite big, pred. triglycerides
Intermediate Density Lipoprotein (IDL)= medium sized, very short lived
Low Density Lipoprotein (LDL)= small, cholesterol-rich, long-lived
High Density Lipoprotein (HDL)= smallest, cholesterol-rich, long-lived
What are Apolipoproteins and which types belong with each lipoprotein?
Determine lipoprotein behaviour
ApoB48= chylomicrons
ApoB100= VLDL, IDL, LDL
ApoA1= HDL
Describe triglyceride metabolism
Energy
- Chylomicrons, created in the gut, deliver triglycerides to muscle and adipose tissue (converted to NEFA)- post prandial (after eating food)
- VLDLs, synthesised in the liver, also deliver triglycerides to muscle and adipose tissue (NEFA)- fasting state
Describe cholesterol metabolism
Essential building block and precursor (for steroid hormones and Vitamin D)
- Liver is the master organ= synthesis, secretion, uptake, excretion
- Delivered to peripheral tissues via LDL
- Uptake from circulation via remnants, IDL, LDL, HDL
- Returned to liver via HDL
What is the Lipid hypothesis in lipid-driven CV disease?
Elevated non-HDL cholesterol causes atherosclerosis, in particular coronary heart disease
Ancel Keys- Seven Countries Study
What does the large prospective study show in lipid-driven CV disease?
Increased CV mortality as serum total cholesterol increases
Absolute risk varies from country to country
What is the difference between HDL and LDL in studies?
Raised HDL-cholesterol decreased rates of CV disease while LDL-C increased rates of CV disease