CLINICAL CHEMISTRY LIPIDS Flashcards
Lipids are composed of mostly
C-H bonds
Lipids are commonly reffered to as
fats
Lipids are source of
Fuel
Lipids are insoluble to
blood or plasma
Lipids are soluble to
organic solvents
Classifications of Lipids:
Fatty acids, Triglycerides, Cholesterol, Phospholipids, Fat-soluble vitamins (A,D,E,K)
Lipids are transported by:
Lipoproteins (VLDL, LDL, HDL)
Linear chains of C-H bonds that terminates with -COOH
Fatty Acids
constituents of phospholipids or triglycerides
Fatty Acids
derived from the hydrolysis of triglycerides in the adipose tissue
Fatty Acids
substance for the conversion of glucose for gluconeogenesis
Fatty Acids
Fatty acids bound to albumin are ____
unesterified
Fatty acids constituent of triglycerides or phospholipids __
esterified
short fatty acids chain number:
4-6
medium fatty acids chain:
8-12
long chain of fatty acids:
> 12
fatty acids with no double bonds
saturated
fatty acids with one double bond
monosaturated
fatty acids with greater than or equal to double bond
polyunsaturated
Classification of fatty acids: butyric acid
saturated
Classification of fatty acids: oleic acid
monosaturated
Classification of fatty acids: linoleic acid
polyunsaturated
Classification of fatty acids: glycerol
saturated
Also known as neutral fat
triglyceride
triglyceride contains —– fatty acids attached to one molecule of glycerol
three fatty acids
Contains saturated fatty acids or unsaturated fatty acids; veryhydrophobic
triglycerides
No charged groups, water insoluble, neutral lipid
triglyceride
Main storage of lipid in man
triglycerides
triglycerides are mainly found in
adipose tissues
triglycerides percentage of stored fat in body
95%
Predominant form of triglyceride in plasma
glyceryl ester
Provides insulation
Lipid - Triglycerides
Enzyme for breaking down lipids
Lipoprotein Lipase (LPL)
hormone for lipid breakdown
epinephrine and cortisol
Also known as conjugated lipids
phospholipids
Phospholipids contains
two fatty acids attached to one molecule of glycerol
phospholipid head group location
third position (phosphorylated end)
Hydrophilic end of phospholipid location
outer part
Hydrophobic end of phospholipid location
Inner
Most abundant lipid in the body
phospholipids
Phospholipids are derived from
phosphatidic acid
Origin of phospholipids
liver and intestines
Not part of the lipid profile; not routinely measured
phospholipids
Phospholipids are only measured in
Fetal Lung Maturity
Fetal lung maturity collection
amniotic fluid and phospholipids
Surfactants of phospholipids
Sphingomyelin and lecithin ratio
Three forms of phospholipids: Major form of phospholipids (70%)
Lecithin or Phosphatidyl Choline
Three forms of phospholipids: constitutes about 20%
Sphingomyelin
Three forms of phospholipids: Constitutes about 10%
Cephalin
Also known as 3-hydroxy-5, 6 Cholestene
Cholesterol
Unsaturated steroid alcohol contains four rings, component of steroids
Cholesterol
amphiphatic lipids
Cholesterol and Phospholipids
Important constituent in the assembly of cell membrane
and bile acid (as precursor)
Cholesterol
contributes to the metabolism or digestion
of fats in the intestine
Bile acid
Lipid that does not serve as fuel of energy of the cells
Cholesterol
Unesterified cholesterol: amphiphatic; 30% of the total cholesterol in the body; Present in the plasma or serum, and RBCs; Polar type
Free cholesterol
Esterified cholesterol: neutral lipid; 70% of the total cholesterol in the body; also present in plasma or serum; hydrophobic form
Cholesterol ester
Important enzyme for esterified cholesterol
LCAT: Lecithin-Cholesterol Acyl Transferase
catalyzes the esterification of cholesterol by promoting the transfer of fatty acids from lecithin to cholesterol
LCAT: Lecithin-Cholesterol Acyl Transferase
activator for LCAT
APO A-I
Promotes fat absorption in the intestine
bile salts
cholesterol converted to steroid hormones:
glucocorticoids, mineralocorticoid; estrogen
Cholesterol converted to vitamin (absorption of calcium)
Vitamin D
Lipid profile test involves:
TAG,Lipoproteins (HD:, LDL, VLDL), Total cholesterol
Directly measured with reagent in Lipid profile test
TAG (triglycerides); cholesterol
Directly measured with reagent and machine in lipid profile test
HDL
Not directly measured with reagent, these are calculated/computed in Lipid Profile
LDL and VLDL
essential or important in the diagnosis of lipoprotein diseases and management of lipoprotein disorders and lipid abnormalities
Cholesterol
Components of Lipoprotein structure
both lipids and proteins (apolipoproteins)
Composition of Lipoprotein structure on the surface (hydrophilic)
Free cholesterol, phospholipids
Composition of Lipoprotein structure found in the core regions (hydrophobic)
Triglycerides and cholesteryl esters
Characteristics Functions of Apolipoproteins
Highly stable
Ligands for cell receptor
activators and inhibitors of enzymes
amphipathic
Apolipoprotein: Apo A-I and A-II
Major LPP location
HDL
Function: LCAT activator, ABCA1, lipid acceptor
Apolipoprotein:
APO A-I
Function: Inactivates LCAT ; Apolipoprotein:
Apo A-II
Apolipoprotein: Apo B-100 ; Major LPP location
LDL, VLDL
Apolipoprotein: Apo B-48 ; Major LPP location
Chylos
Apolipoprotein: Apo- IV, C-I, C-II, C-III ; Major LPP location
Chylos, VLDL, HDL
Apolipoprotein: Apo E ; Major LPP location
VLDL, HDL
Apolipoprotein: Apo(a) ; Major LPP location
Lp(a)
Function: LDL receptor ligand ; Apolipoprotein:
Apo B-100, Apo E
Function: remnant receptor ligand ; Apolipoprotein:
Apo B-48
Function: LPL cofactor ; Apolipoprotein:
Apo C-II
Function: LPL inhibitor ; Apolipoprotein:
Apo C-III
Function: Plasminogen inhibitor ; Apolipoprotein:
Apo(a)
Major types of lipoproteins
Chylomicrons, VLDL, LDL, HDL
Heaviest lipoprotein
HDL
Major protein of chylomicrons
Apo B-48
Major protein of VLDL and LDL
Apo B-100
Major protein of HDL
Apo A-I
Total lipid (% by weight) 98%
Chylomicrons
Total lipid (% by weight) 89-96
VLDL
Total lipid (% by weight) 77%
LDL
Total lipid (% by weight) 50%
HDL
Triglyceride (% by weight) 84%
Chylomicrons
Triglyceride (% by weight) 44-60%
VLDL
Triglyceride (% by weight) 11%
LDL
Triglyceride (% by weight) 3%
HDL
Largest and least dense lipoprotein
chylomicrons
Major transporter of exogenous triglycerides
chylomicrons
Chylomicrons are produced in
intestines
Exogenous triglyceride transports
dietary lipids to hepatic and peripheral cells
Chylomicrons are completely cleared from plasma or circulation within
6-9 hours post-prandial
Fasting required for lipid profile testing
12 hours
Chylos present in blood causes —- in lipid profile
false increased
Lipid profile is done to determine
normal metabolism
Lipid and Glucose Tests fasting hours:
10 hours
Also known as pre-beta lipoprotein
very low density lipoproteins
Electrophoresis location of VLDL
pre-beta region
VLDL is produced in
liver and intestines
Endogenous pathway:
Transfer triglycerides from the liver to peripheral tissues
Also known as beta lipoprotein or bad cholesterol
Low density lipoprotein
Electrophoresis location of LDL
beta region
Most cholesterol rich; most atherogenic lipoprotein
LDL
atherogenic: contribute to the formation of Insoluble fatty
plaque of blood flow (obstruction in blood vessel)
LDL
Formed from lipolysis of VLDL to IDL (intermediate density lipoprotein
LDL
LDL pathway
Exogenous (dietary chole to peripheral)
Also known as: Alpha lipoprotein or good cholesterol
High density lipoprotein
Electrophoresis location of HDL
Alpha region
HDL is produced in the
liver and intestines
HDL pathway
reverse cholesterol transport mechanism
HDL transfers excess cholesterol back to —
Liver
High HDL relationship to coronary heart disease
lower risk for CHD
High LDL relationship to coronary heart disease
increases the risk for CHD
CARDIOPROTECTIVE LIPOPROTEIN
HDL
Only minor type of lipoprotein; LDL lipoprotein like particle
Lipoprotein(a)
has a variable migration when subjected to electrophoresis; pre-beta region or between LDL and Albumin region
Lipoprotein(a)
Confers increased risk for: premature coronary heart disease and stroke
Lipoprotein(a)
Lipoprotein (a) competes with plasminogen for
fibrin
Important for fibrinolysis
plasminogen
Also known as the SINKING PRE-β LIPOPROTEIN
Lipoprotein(a)
density of lipoprotein(a) is the same as
LDL
Product of VLDL catabolism
INTERMEDIATE DENSITY LIPOPROTEIN (IDL)
IDL migration to electrophoresis
pre-B or Beta region
Abnormal lipoprotein: found in obstructive jaundice
and LCAT deficiency
Lipoprotein X (Lpp X)
Lipoprotein X (Lpp X) is specific and sensitive indicator for
cholestasis
lipid content is mostly phospholipid and free cholesterol (90%)
Lipoprotein X (Lpp X)
Lipoprotein X contains
Apo C and albumin
Abnormal lipoprotein: known as “abnormally migrating β-VLDL”
B-VLDL
also known as floating beta lipoprotein
B-VLDL
has the density of VLDL by ultracentrifugation but
migrates with LDL in the β region during electrophoresis
B-VLDL
B-VLDL is found in what disease
type 3 hyperlipoproteinemia or dysbetalipoproteinemia
Rich in cholesterol content than VLDL
B-VLDL
Adult reference range for lipids: Total cholesterol
140-200 mg/dl
Adult reference range for lipids: HDL cholesterol
40-75 mg/dL
Adult reference range for lipids: LDL cholesterol
50-130 mg/dL
Adult reference range for lipids: triglyceride
60-150 mg/dL
Conversion factor for total cholesterol
0.026 mmol/L
Conversion factor for triglyceride
0.011 mmol/L
Conversion of dietary lipids into more polar (amphipathic) compounds by Pancreatic Lipase
Lipid absorption
can also be linked to infection, no absorption, problem in lipid absorption (too much fat globules in feces)
Steatorrhea
Lipid absorption: conversion of triglyceride
monoglycerides
Lipid absorption: conversion of cholesterol esters
free cholesterol
Lipid absorption: conversion of phospholipids
lysophospholipids
Pathway: Chylomicrons: synthesized in the intestine, carrying dietary lipids to the circulation
Exogenous pathway
Pathway: Triglycerides in the liver: packaged into VLDL, carrying lipids to the circulation
Endogenous pathway
Pathway: Chylomicrons → chylomicron remnant particles
Exogenous pathway
Pathway: VLDL is converted into (IDL) by action of LPL and taken up by liver; Half of VLDL is transformed into: LDL for delivery of exogenous cholesterol to peripheral cells
Endogenous pathway
Pathway: HDL remove excess cholesterol transport pathway deliver cholesterol back to the liver o To recycle unused and excess cholesterol
reverse cholesterol transport mechanism
Lipid disorders: Deposition of esterified cholesterol in artery wall
Arteriosclerosis
Lipid disorder: Increased smooth muscle cells, extracellular lipid, calcification, fibrous tissue, macrophages, lymphocytes, fibrin clots, and platelets (plaque)
Arteriosclerosis
Coronary Artery disease affects
heart (angina and MI)
Peripheral vascular disease (PVD) affects:
arteries in the arms or legs
Cerebrovascular disease (CVD) affects
vessels of the brain (stroke)
Increased cholesterol
Increased LDL, Decreased receptors
Amphipathic, Clear appearance but with high level
Hypercholesterolemia
Increased Triglycerides; Decreased LPL or Apo C-II VLDL -/→ VLDL remnants; Chylos -/→ Chylos remnants; Highly hydrophobic
Hypertriglyceridemia
Increased Triglycerides, Cholestero; Increased VLDL and Chylos remnants; Presence of Apo E2/2
Combined Hyperlipoproteinemia
Other Lipid Disorder: Also known as Type 2-a
Familial Hypercholesterolemia
Other Lipid Disorder: Also known as Type 3 Hyperlipoproteinemia
Familial Dysbetalipoproteinemia
Other lipid disorder: Basses-Kornzweig Syndrome
Abetalipoproteinemia
Other lipid disorder: Lipid Storage Disease
Niemann-Pick disease
Lipid measurement principle for cholesterol measurement
Dehydration and Oxidation of cholesterol to form a colored compound
Preparation for cholesterol measurement:
2 weeks usual diet; fasting is not strictly implemented
Hemolyzed serum causes __ in cholesterol
false increased
Water contamination effect in cholesterol
less accurate
Color developer for cholesterol measurement
Glacial Acetic acid, acetic anhydride, conc. sulfuric acid
Lipid measurement triglyceride requirement
12 hours fasting
Lipoprotein Measurement tube for research studies
EDTA (plasma)
Non enzymatic method for cholesterol measurement
Abell Kendall
Abell Kendall: Cholesteryl esters: hydrolyzed with
Alcoholic KOH
Abell Kendall: Unesterified cholesterol: extracted with
Hexane
Non enzymatic method for cholesterol is measured with
Liebermann - Buchard reaction
Salowski Reaction
Liebermann - Buchard reaction: Cholesterol + sulfuric acid + acetic anhydride -> produces:
Green solution (Cholestadienyl Monosulfonic Acid)
Salowski reaction for cholesterol produces
Red solution (Cholestadienyl Disulfonic Acid)
Involves colorimetry - mix, incubate, and measure for Abell Kendall (Non-enzymatic)
1-step method
involves colorimetry and extraction for Abell Kendall
2- step method
3 step method for Abell Kendall
Colorimetry, Extraction, Saponification
4 step method for Abell Kendall
Colorimetry, Extraction, Saponification, and precipitation
Enzymatic Method for Cholesterol measurement uses
Cholesterol oxidase
CDC reference method for cholesterol measurement
Abell, Levy and Brodie Method
1st enzyme for enzymatic method (cholesterol)
Cholesteryl esterase
2nd enzyme for enzymatic method (cholesterol)
Cholesterol oxidase
Enzymatic method 3rd enzyme for cholesterol
Peroxidase
Color produced in cholesterol oxidase method
quinoneimine dye
TRIGLYCERIDE MEASUREMENT: non-enzymatic method measures
glycerol
Product of Glycerol + Periodic acid (triglyceride measurement)
Formaldehyde
Colorimetric measurement for triglyceride
Van Handel and Zilversmith
Van handel and Zilversmith: Formaldehyde + Chromotropic acid product
Blue solution
Principle of Hantzch Condensation
Fluometric
Hantzch Condensation: Formaldehyde + Diacetyl acetone + NH3 → produces ___
Yellow solution
Enzymatic Method for triglyceride
Glycerol kinase
Product of glycerol + ATP – glycerokinase–>
Glycerophosphate + ADP
Pyruvate kinase for triglyceride: ADP + PEP (phosphoenolpyruvate) –Pyruvate kinase → product
ATP + Pyruvate
Triglyceride measurement: Pyruvate + NADH + H+ - LD → product
Lactate + NAD (measured at 340 nm)
Triglyceride measurement: Glycerol-Phosphate Oxidase measures
color of end product
CDC reference method for Triglyceride
Modified Van Handel and Zilversmith
Lipoprotein measurement general methods:
Ultracentrifugation and Electrophoresis
Reference method for the quantitation of lipoproteins
Ultracentrifugation
Lipoprotein measurement: Ultracentrifugation of plasma is done for
24 hours
Lipoprotein measurement by ultracentrifugation is measured by
molecular density
Principle of ultracentrifugation: The density of the lipoprotein is compared with the density of the
Potassium bromide
Density of potassium bromide
1.063
Order from lightest to heaviest lipoprotein in ultracentrifugation
Chylomicrons
VLDL
LDL
HDL
Lipid stains for Electrophoresis of lipoproteins
Oil red O, Fat Red 7B and Sudan
black
Electrophoresis: 4 bands with fat stains: fastest
alpha lipoprotein (HDL)
Electrophoresis: 4 bands with fat stains: Pre-beta
VLDL, LP(a)
Electrophoresis: 4 bands with fat stains: Beta
LDL
Electrophoresis: 4 bands with fat stains: stationary at origin
chylomicrons
Most sensitive supporting medium for lipoprotein electrophoresis:
agarose gel
High-Density Lipoprotein (HDL) Methods: precipitated with polyanions (e.g. Heparin, dextran sulfate or Na phosphotungstate) in the presence of divalent cations (e.g. Mg or Mn), which are sediment by centrifugation (10-30 min. for 10,000g or 3 min. for 15,000g
Polyanion precipitation
HDL is quantified in the supernate by:
Abell kendall (total cholesterol assay)
Low-Density Lipoprotein (LDL) Methods: Friedwald formula for VLDL mg/dL
VLDL= Triglyceride / 5 = mg/dL
Low-Density Lipoprotein (LDL) Methods: Friedwald formula for VLDL mmol/L
VLDL= Triglyceride / 2.175 = mmol/L
Ultracentrifugation of serum at native density gradient of ____ to float VLDL
1.006 g
LDL formula
Total cholesterol - (HDL + VLDL)
Apolipoprotein methods for testing
✓ Immunonephelometry
✓ Immunoturbidimetric Assay
✓ Immunochemical Method
apolipoprotein for determination of LDL and VLDL conc.
Apo B
Apolipoprotein for determination of HDL conc.
Apo A-I
Positive risk factor age for men (CHD)
> or = to 45
Positive risk factor age for women (CHD)
> or = to 55 (premature menopause)
Hypertension BP measurement
BP > or = to 140/90 mmHg
Lipoprotein effect to CHD: HIGH LDL; LOW HDL
Increased risk
LDL cholesterol concentration: > or = 160mg/dL
= or <1 RF
LDL cholesterol concentration: > or = 130mg/dL
= or >2RF
LDL cholesterol concentration: >= 100 mg/dL
with CHD or equivalent
Diabetes mellitus = CHD risk equivalent due to
active lipolysis that is not converted to glucose
Negative risk factor for CHD: HDL cholesterol concentration
> or = to 60mg/dL
Negative risk factor for CHD: LDL cholesterol concentration
<100mg/dL: LOW
Healthy fats to prevent CHD
Omega-3 or Omega- 6
