HDL and LDLs

cholesterol:

  • short lipid molecule

  • uses in the body

    • important in cell membranes ( maintaining fluidity of membranes)

    • used to make some steroid sex hormones and growth hormones

    • used to make some of the components of bile

  • made in liver and obtained in diet

  • concerns that too much is bad for us

its a problem because higher cholesterol level, the greater risk of CHD:

  • 45% of CHD deaths in men due to increased cholesterol

  • 47% of CHD deaths in women due to increased cholesterol

lipoproteins:

  • cholesterol is not water soluble so combines with proteins to be transported around the bloodstream ( lipoproteins)

LDL:

  • triglycerides from saturated fats, cholesterol and protein combine to form LDLs

  • these circulate in blood and should attach to receptors on cell membranes before being absorbed

  • excess LDLs overload receptors = too many LDLs in blood

  • this excess cholesterol starts being deposited on artery walls instead

HDL:

  • same components as LDL but more protein

  • made from triglycerides from unsaturated fats

  • HDLs carry cholesterol from body tissue to liver

  • this lowers blood cholesterol levels

Genetics and CVD:

  • rare to get simple mutations to one gene that affect risk of CHD

  • one example is familial hypercholesterolaemia (HF)

    • mutations to LDLR gene for LDL receptors

    • LDL not removed from blood

    • early onset of CHD

Apolipoprotein gene cluster:

  • protein component of lipoproteins

  • example: apolipoprotein A

    • major protein in HDL helps removal of cholesterol

    • mutation to apoA gene associated with low HDL levels and higher blood cholesterol, therefore reduced removal to liver for excretion leading to increased CHD risk

  • Apolipoprotein B ( APOB)

    • major protein found in LDL cholesterol, mutation results in high LDL levels in blood, therefore increased risk of CHD

  • Apolipoprotein E (APOE)

    • major protein found in HDL ( and VLDLs) cholesterol. three common alleles APOE4 slows removal of cholesterol from the blood and therefore increased risk of CHD