Lipid Testing and Cardiac Risk Assessment

Fatty Acids Glycerol Esters Triglycerides Phospholipids

Short, medium, & long chains linear molecules that are major constituents of triglycerides and phospholipids (Saturated, Monounsaturated, Polyunsaturated) Found in cell membranes Components of hormones and vitamins

Triglycerids: Glycerol ester comprised of glycerol and 3 fatty acid molecules Phosphoglycerides: Glycerol esters/phosphoric acid group and 3 fatty acid molecules - Lecithin: cholin molecule - Cardiolipins

Form oils at room temperature if plant based, solid structure when animal based 95% of fats shored in adipose tissues Transported in body as chylomicrons and very low density lipoproteins (VLDL) Metabolism involves releasing fatty acids to the cells for energy, then recycling the glycerol into triglycerides Lipase, lipprotein lipase, epinephrine, and cortisol breakdown triglycerides

3rd position on the glycerol backbone contains a phospholipid head Phospholipid head group determines the phospholipid type Are a major constituent of cell membranes and outer shells of lipoprotein molecules

Lecithin Most common phospholipid Has a choline head

Found on surface of lipid layers Hydrophilic head faces outward Fatty acid chains face inward

Sphingomyelin Important for normal lung function along with lecithin Keeps alveoli distended

Unsaturated sterol alcohol found exclusively in animals Synthesized from acetyl-CoA in microsomal and cystosolic compartments of cells Amphpathic lipid found on surface of lipid layers along with phospholipids Also exists in highly polar esterified form known as Cholerteryl ester Not readily catabolized by most cells and does not serve as energy source for body Elevations correlate with coronary artery disease from plaque formation

Cell membrane structural component Bile acid precursor Steroid hormone precursor

Exogenous Endogenous - 70% in skin, adipose tissue and muscle cells - 30% is in transport in form of lipoproteins (LDL & HDL)

Lipids packaged in a micelle of cholesterol, triglyceride, phospholipids and protein

High density lipoprotein Prefer to see this in high numbers

Low density lipoprotein Not as good at carrying cholesterol

Intermediate density lipoprotein (VLDL remnants) - Normally short lived form in conversion of VLDL to LDL - In type 3 hyperlipoproteinemia, IDL are detected - Rare inborn error in which abnormal apo E delays clearance

Very low density lipoprotein

Tons of lipids and triglycerides Very little protein

Spherical structure of lipids and proteins (called apolipoproteins) Role is to transport lipids to and from cells to liver and dietary lipids from intestines

On surface as a monolayer

Polar Inside core

Protein component of lipoproteins located on the surface of the lipoprotein particle Protein composition differs from one lipoprotein class to another

Make hydrophobic lipids soluble in blood for transport Activate enzymes involved in lipid metabolism Maintain structural integrity of lipid/protein complex Deliver lipids to cells via recognition of cell surface receptors

Major constituent of HDL Activates lecithin-cholesterol acyltransferase (LCAT) which catalyzes the formation of cholesterol esters Higher A1 = lower plaque formation

Apo B-100 Major component of LDL, VLDL, and chylomicrons Binds to LDL receptors