Lipids Flashcards
What does a lipoprotein structure consist of
hydrophilic shell - phospholipids and cholesterols
Hydrophobic core - triglyceride and esters
contains specific protein - apolipoprotein
maintains structural integrity
binds to cell receptor, enzyme activators and inhibitors
function and how classification of lipoproteins
main function - fuel delivery
acts as a transport molecule for lipids
made in intestine and liver
classified by density via ultracentrifugation
chylomicrons (highest lipid to protein ratio)
H/LDL
What is a chylomicron
largest and least dense (floats)
-found in intestine
part takes in endogenous pathway - transports DIETARY triglycerides to liver
-hydrolyzed by lipase
-found in blood after a FAT RICH MEAL
What is a VLDL
smaller than chylomircons
low lipid and higher protein - dont float
-most triglycerides
-found in liver
transports dietary and endogenous TRIGR from liver to tissues
-presence can cause turbidity in fasting sample
too much carbohydrates, saturated and trans fats
What are LDLs
smaller than vldl
known an BAD cholesterol can lead to atherosclerosis
even less lipid content - MAJOR cholesterol carrier
found in liver from lipolysis of liver
transports cholesterol from liver to tissues
PROATHEROGENIC
taken up into vessel walls
FOAM CELLS when taken up by macrophages
increases BAD cholesterol
What are HDLs
SMALLEST MOST DENSE
made in liver and intestine
50/50 protein and lipid
reverses cholesterol transport pathway
removes excess cholesterol and returns to liver
LOWERS CHOL - GOOD CHOL
HDL = decreased risk of CVD
Why can you have differences in serum lipid/protein concentrations
Sex - pre/post menopause
Age
Culture/Location
Genetics
Why are lipids analyzed
CVD leading cause of death in Canada
-CVD associated with serum Chol concentration = dyslipidemia
-risk of premature atherosclerosis
➢hypercholesterolemia
➢ hypertriglyceridemia
➢ high levels of LDL cholesterol (hyperbetalipoproteinemia)
➢ low levels of HDL cholesterol (hypoalphalipoproteinemia)
How do we collect sample for cholesterol
person on normal diet fasts 12-14 hrs
serum or heparin plasma
➢ Avoid fluoride/oxalate
➢ Separate ASAP; store at
4˚C or -20˚C
how is cholesterol measured
Conversion of Cholesteryl ester to fatty acid and then to peroxide with esterases and oxidases
use of peroxidase to view color change
➢ Measure absorbance of coloured dye at 540 nm (e.g. AU480)
➢ Absorbance proportional to concentration
RI for total CHOL level that are associated with CVD risk are set by experts
-increased result is associated with increased risk
-needs to be used with other tests to confirm
Health <5.20
High risk >6.20
What is familial hypercholesteromelia
genetic disorder - codominant
-when the exogenous pathway is overwhelmed
-high LDL due to defective LDL receptors = premature CVD
signs : first heart attack as a teenager, tuberous xanthomas (deposits in skin , raised lesions with yellow centers) and corneal arcus (deposits in cornea)
how do you collect triglycerides
fast 12-14 hours
water only
no alcohol 24 hours prior
serum or heparin plasma
store at -4 or -20
use of bacterial lipase, glycerokinase, oxidase and peroxidase for an enzymatic assay sequence where ABs is measured at 520 nm
-abs proportional to concentration
What are the sources of error in triglyceride measurement
endogenous glycerol false increases result can be small in instances of stress or disease but there is an increase nonetheless
➢ glycerol-containing medication
➢ glycerol-coated stoppers
healthy <1.70
high <2-5
how does Hypertriglyceridemia contribute to CVD
not an independent factor for CHD but increased TRIGR, LDL, HDL contribute to CVD risk
Familial Hypertriglyceridemia:
increases in VLDL lipoprotein
complication from pancreatitis
increased dietary triglycerides like chylomicrons can block pancreatic capillaries and can cause ischemia which exposes TRIGR to pancreatic lipase and causes inflammation and pancreatitis
how to treat Hypertriglyceridemia
moderate and severe
moderate hypertriglyceridemia
➢ modify diet
➢ control blood glucose
➢ exercise
➢ weight loss
➢ abstain from alcohol
✓for severe primary hypertriglyceridemia
➢ very-low-fat diet
➢ drug therapy: fibric acid derivatives
