Lipids - Cholesterol and Cardiovascular Markers Flashcards
Cholesterol
Cholesterol is an important compound for cell structure and function. Beneficial properties are often overlooked because of negative perceptions around cardiovascular disease risk.
* Cholesterol is essential for the synthesis or action of:
o Vitamin D and calcium metabolism.
o Cortisol and related hormones.
o Aldosterone for mineral and fluid balance.
o Sex hormones —oestrogen, progesterone and testosterone.
o Bile salts and acids needed for digestion.
o Membrane integrity, especially in the brain.
o Lipoproteins, needed for triglyceride transport.
Cholesterol synthesis
A diet rich in triglycerides stimulates cholesterol synthesis in the liver and small intestine.
* It is excreted in the stool intact, mostly as bile products.
* The excretion is increased by absorption onto non-digestible carbohydrates (fibre).
* Gut bacteria from healthy microbiomes metabolise cholesterol = less reabsorption.
* Dietary cholesterol does not significantly affect plasma cholesterol levels in most people as they are primarily influenced by genetic and nutritional factors.
Lipoproteins
Doctors and other health officials often refer to cholesterol as ‘good’ and ‘bad’, especially in reference to heart health.
* LDL and HDL cholesterol are in fact carriers. Cholesterol sits within these lipoproteins to be transported to wherever needed.
* A lot of other substances are carried within them including CoQ10, beta-carotene and vitamin E.
* LDL (low density) —takes cholesterol from the liver to cells.
* VLDL (very low density) —takes triglycerides to cells.
* HDL (high density) —collects cholesterol from cells to transport back to the liver.
Cholesterol and health industry
Governments have led us to believe that saturated fat and cholesterol simply clog up arteries and cause heart attacks.
* This led to a global cholesterol-lowering industry, with around 200 million people taking statins.
* In 2009, a study found that ‘bad’ cholesterol was lower in people with heart disease.
* Over a period of 10 years the percentage of men aged 65–74 with high cholesterol dropped from 87 to 54, whereas CHD remained at 20%.
* In 2004, the definition of low plasma cholesterol dropped from below 6.5 mmol / L to below 5 mmol / L.
BHF advert ‘fat arteries’: https://www.youtube.com/watch?v=cDAN7Oi62e0
Increased cholesterol in health conditions and atherosclerosis
Increases in cholesterol may indicate an increased demand for cholesterol’s anti-inflammatory function or an increased need for cholesterol to repair membranes, make hormones, etc.
* Atherosclerosis requires LDL cholesterol to deposit in the arterial wall and become oxidised.
* Atherosclerosis is an inflammatory disease. In the absence of inflammation or injury to the endothelium, cholesterol does not deposit.
* There are varying sizes of LDL cholesterol. Measuring particle size rather than total cholesterol is a better health indicator.
Cardiovascular Markers:
LDL particle size
LDL particle size —people whose LDL particles are predominantly small and dense have a threefold greater risk of coronary artery disease, whereas the large and fluffy type may be protective.
Cardiovascular Markers:
HDL particle size
HDL particle size —larger HDL particles are more effective at removing cholesterol from the blood. Larger particles better exert anti-inflammatory and anti-thrombotic effects, as well as promoting nitric oxide production in endothelial cells.
CVD Markers: Lipoprotein (a)
Lipoprotein (a) is a blood clotting agent. It appears to be a key genetic factor in coronary artery disease. Higher levels are associated with greater risk.
CVD Markers:
Lp-PLA2
Lp-PLA2—an enzyme that plays a role in endothelial inflammation and atherosclerosis
CVD Markers:
Fibrinogen
Fibrinogen —raised levels are a risk factor for clot formation
CVD Markers:
C-reactive protein
C-reactive protein —inflammatory marker associated with CVD.
CVD Markers:
Lipid peroxides
Lipid peroxides —raised levels reflect oxidative damage to membranes.
Cardiovascular Markers: GP test
A GP cholesterol test what does this tell us?
* Serum cholesterol above 5 mmol / L —GP prescribed a statin.
* Triglycerides (TGs) are high, but this is a non-fasting sample. The optimal range is 0.79–1.24 mmol / L.
See Diagram
Cardiovascular Markers: Functional test
A functional test tells us much more about CV health:
↑LDL-P and normal or ↓HDL-C levels = higher CV risk.
LDL-P correlates with carotid atherosclerosis and is more closely associated with obesity, diabetes and insulin resistance than LDL-C.
See Diagram
