360 - Lipids & Cardiac Markers Flashcards
these transport lipids in the plasma
lipoproteins
typical lipoprotein structure
core of triglycerides and cholesteryl ester and a shell composed of apolipoprotein, unesterified cholesterol, and phospholipid
linear hydrocarbon chains that terminate in a carboxyl group
fatty acids
beta oxidation of free fatty acids
forms acetyl-CoA which enters the Kreb’s cycle to produce energy
triglycerides
many types
- composed of 3 fatty acid molecules and one molecule of glycerol; they are classified as neutral lipids
describe cholesterol
- amphipathic molecule
- esterified form of cholesterol = cholesteryl ester, is conjugated to fatty acids and is classed as a neutral lipid
- used to synthesize many hormones, including mineral corticoids, and sex hormones
amphipathic molecules composed of two esterified fatty acids, glycerol, and a phospholipid group
phospholipids
- found in cell membranes
T or F. Apolipoproteins are amphipathic.
T!
how are lipoproteins classified
- by their densities
- 6 categories: chylomicrons, very low-density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low-density lipoproteins (LDL), high-density lipoproteins (HDL) and lipoprotein (a)
T or F. As the density of lipoproteins increases the proportion of triglycerides decreases and the proportion of cholesteryl ester increases
T
how are lipoproteins measured?
immunoturbidimetry and immunonephelometry
these transport dietary lipid to the liver and peripheral cells
chylomicrons
the largest lipoprotein and the least dense
chylomicrons
- form the creamy layer that settles on serum; Apolipoprotein B-48 is only found in chylomicrons
where is VLDL primarily produced?
liver
this carries endogenous triglycerides from the liver to peripheral cells
VLDL
these are used for energy during fasting periods
triglycerides
the primary component of VLDL apolipoprotein
Apolipoprotein B-100
formed by the lipolysis of VLDL
LDL
- contains apolipoprotein B-100
T or F. LDL is readily taken up by the liver and peripheral cells
T
- LDL can move into the extracellular space of blood vessel walls
- LDL is oxidized and ingested by macrophages
- laden with lipid evolve into foam cells
- foam cells are components of fatty streaks, which can develop into atherosclerotic plaques
the densest lipoprotein
HDL
where is HDL synthesized?
in the liver and intestine
what does HDL do?
transports cholesterol away from the peripheral cells, back to the liver
Its anti-atherogenic properties are attributed to its ability to remove cholesterol
HDL
this component may be measured to determine anti-atherogenic status of HDL
apolipoprotein A-1
Coronary heart disease is characterized by …
narrowing of the small vessels that carry oxygenated blood to the heart
Atherosclerosis
a pathologic process characterized by cholesterol deposits on vessel walls, macrophage invasion, and plaque formation
interferences in triglycerides enzymatic assay
- Endogenous free glycerol can participate in the reaction, reagent blank may correct this interference
- Bilirubin and vitamin C may interfere, but enzymes may be added to eliminate this interference
- Hemolysis may cause positive interference
specimen used for triglycerides enzymatic assay
- 12hr fasting (triglyc incr after meals)
- aviod alc for 24 hrs before test (transient increase in trigly)
- smoking increases trigly
- increase when go from lying down to standing
total cholesterol enzymatic assay interferences
- Bilirubin and vitamin C can cause false DECREASES because they react with H2O2
- Hemolysis may cause positive interference
total cholesterol enzymatic assay specimen collection
- 12hr fasting specimen (IF part of lipid panel)
- chol DECREASEs w exercise
- smoking increases chol
- prolonged toueniquet = increases chol
- chol increases from lying to standing
HDL methodology
- direct HDL cholesterol = homogenous assay
- does not require pretreatment/centrifugation
- depends on a unique detergent which solubilizes only HDL lipoprotein particles & releases HDL cholesterol to react with chol esterase and chol oxidase in presence of chromogens
- the detergent also inhibits the reaction of the cholesterol enzymes with LDL, VLDL, and chylomicron lipoproteins by adsorbing to their surfaces
HDL methodology:
A ____________ contained in the reagent enhances the selectivity for HDL cholesterol assay by complexing ____, _____, and _____________ lipoproteins
polyanion; LDL, VLDL, chylomicrons
T or F. In HDL direct method, the change in absorbance at 560 nm is directly proportional to the concentration of cholesterol in the sample
T, (Beckman Coulter LX 20 manual).
Friedewald formula for calculating LDL cholesterol
Total cholesterol - [Triglyceride÷2.2] - [HDL cholesterol]
the result of an obstruction in the circulatory pathway of the heart resulting in necrosis of the heart muscle
myocardial infarction
cardiac markers of choice for MI
troponins
this occurs when the heart is unable to pump blood to maintain oxygenation of the tissues
congestive heart failure
congestive heart failure is characterized by …
edema, due to sodium and water retention, and breathlessness
congestive heart failure cardiac markers of choice
B-type natriuretic peptide (BNP) and a catabolic product of pro-BNP: NT-pro-BNP
a protein molecule composed of three subunits, TnC, TnT, and TnI and is a part of the actin-myosin contractile unit of muscle
troponin
where are cardiac troponins found?
found only in the heart and are released into the blood during cell death
Troponin I (cTnI) and Troponin T (cTnT) rise approximately _-_hours after the onset of symptoms.
2-6 hrs
T or F. cTnI is more specific than cTnT for myocardial infarction
T!!
Troponin remains elevated in the blood ______ to ____days after an MI.
four to ten days
these may interfere with troponin I performance
heparin, heterophilic antibodies, autoantibodies, fibrin/hemolysis, and rheumatoid factors
NOTE: Barricor tubes may reduce interference
AHS recommends the collection of a Troponin I sample at __ hours and again ___ hours later to rule out an MI
0; 6
a hormone secreted by the ventricles of the heart
B-type natriuretic peptide (BNP)
BNP synthesis
- synthesized as a preprohormone (preproBNP)
- preprohormone is cleaved into proBNP, which is further cleaved into two parts: the N-terminal portion (NT-proBNP) and the C terminal, the active portion (BNP)
- NT-proBNP and BNP are found in the circulation
an excellent measure of cardiac stretch
BNP
used for identifying individuals with moderate to severe congestive heart failure and for risk assessment
BNP
the only acceptable sample for BNP
EDTA in a PLASTIC tube
NT-proBNP acceptable sample
Serum or heparin plasma in a glass or plastic tube
high sensitivity C reactive protein
values above normal but below those seen in infection can be detected by the hsCRP assay and are indicative for atherosclerosis, a risk factor for heart disease
