Hyperlipidaemia Flashcards
Where is cholestrol synthesised?
Synthesised in body, with contribution from diet
- Liver
- Adrenal glands
- Sex organs
List some functions of cholestrol
Which type of cholestrol is most susceptible to oxidation via ROS?
- Membrane integrity
- Steroid hormone precursor
- Bile acids
- Vitamin D
LDL cholestrol (70% of cholestrol)
Why is the HDL carrier considered ‘good cholestrol’?
Carries cholestrol away from the circulation to liver for recycling
Briefly describe the pathophysiology of atherosclerosis
- Oxidation of LDL at damaged endothelium by necrotic tissue + ROS
- Adheres to proteoglycans
- Lipid laiden core with fibrous external cap
- Fibrous cap rupture
- Platelet aggregation
- Thrombus formation, MI, stroke
Are high triglycerides treated as a modifiable risk factor?
No
High triglycerides not good, but limited data to suggest that it should be targeted as a modifiable risk factor
Why do we treat high cholestrol?
To reduce CVD risk
What type of cholestrol is targeted for CVD prevention?
LDL cholestrol lowering is target for CVD prevention
What sort of factors does the aggressiveness of treatment depend on?
- Total CVD risk
- Age
- Familial hypercholestrolaemia (genetic); disorder of LDL receptor
Briefly describe the processes leading to atheroma formation and atherosclerosis
- Accumulation of LDL
- Oxidation by local endothelial cells - oxidised LDL
- Formation of foam cells in intima/endothelial space
- Smooth muscle cell proliferation
- Development of fatty streaks
- Chronic inflammation + accumulation of disrupted endothelium/vascular smooth muscle
Development of fatty streaks due to oxidation of LDL cholestrol
What is a common site for the development of fatty streaks?
Descending aorta
Describe the mechanism of action of statins
- Competitive inhibition of HMG-CoA reductase (rate limiting enzyme in mevalonate pathway)
- Upregulation of hepatic LDL receptors
- Increased clearance of circulating LDL
Give some examples of statins
- Atrovastatin; 1st line
- Simvastatin
- Fluvastatin
- Pravastatin
- Rosuvastatin
- Lovastatin
Give some additional benefits of statin therapy which reduce CVD risk
- Improved vascular endothelial function; increased NO and decreased endothelin signalling
- Stabilisation of atherosclerotic plaque; reduced smooth muscle cell proliferation, increased collagen
- Improved haemostasis; reduced fibrinogen, reduced platelet aggregation, increased fibrinolysis
- Anti-inflammatory; reduced proliferation of inflammatory cells into plaque, reduced adhesion molecules + cytokines
- Anti-oxidant; reduced superoxide production (ROS)
Thus, reduced risk of atheroma + atherosclerosis
What type of drugs are simvastatin and atorvastatin?
Pro-drugs; activated by 1st pass metabolism (into active derivatives)
Which has a longer half life; simvastatin or atorvastatin?
Atorvastatin (>30 hrs)
*Dose equity considerations
Give some warnings/contraindications for statins
- GI disruption, nausea
- Headache
- Myalgia (diffuse muscle pain); raised CPK >10x normal limit)
- Rhabdomyolysis (due to organic anion transporter/genetic differences?)
- Muscle breakdown, pain, renal failure
Give some important interactions/considerations for statins
- Renal impairment
- Pregnancy, breast feeding
- CYP 3A4; amiodarone, diltiazem, macrolides
- Amlodipine; increase dose of statin
- Withhold statin short term (eg if taking antibiotics)
- Grapefruit juice (CYP 3A4)
Concurrent use of amlodipine and simvastatin causes a significant increase in blood levels of simvastatin such that, in practice, the effect is double that compared to uninhibited simvastatin. Therefore, in patients on amlodipine 10mg plus simvastatin 20mg, the effect is similar to receiving simvastatin 40mg alone.