Lipids Flashcards
Three hepatic receptors to which LDL may bind to return cholesterol esters back to the liver in reverse cholesterol transfer pathway
- LDL receptor
- HDL receptor
- Remnant receptor
Electrophoretic pattern of Type V
Type I + Type IV; increased chylomicron band and pre-beta band
(At least) two risk factors of the metabolic syndrome
- BMI > 25
- Family history of diabetes mellitus
- History of gestational diabetes
- Polycystic ovary syndrome
Plasma apperance of Type III
Slightly cloudy to cloudy plasma
Mechanism to maintain cholesterol balance; LDL receptors deliver intact particles to lysosomes where cholesterol esters are hydrolyzed by lysosomal aicd lipase; associated apolipoproteins are degraded to small peptide and amino acid
Purpose of intraceullular-cholesterol transport pathway of lipid metabolism
List 5 analytes used to predict risk for development of CAD
- Apo B-100 (on LDL)
- Apo E
- Homocysteine
- High sensitivity CRP (hsCRP)
- Lipoprotein
Electrophoretic pattern of Type IIb
LARGE beta band
Three intracellular uses of cholesterol esterase
Membrane biogenesis, stored in intracellular lipid drops after re-esterification by ACAT catalysis
Major carrier of endogenous (hepatic origin) lipids
VLDL
Secretion of triglycerides from intestine
B-48
The importance of LPL and apo C-II in the formation of the VLDL remnant in the endogenous pathway
C-II activates LPL on the surface of endothelial cells, leading to TGL hydrolysis and free fatty acids release to peripheral cells
Elevated VLDL and chylomicrons, cholesterol increased, moderately increased TGL, LDL and HDL normal to low
Mixed Hyperlipoproteinemia/Type V
Elevated TGL w/o significantly increased cholesterol would cause increases in which two lipoproteins?
VLDL and chylomicrons
The formation of LDL in the endogenous pathway
IDL transfers apo E, C, free cholesterol, and phospholipids to HDL in the circulation making LDL
Three signs and symptoms of the metabolic syndrome
- Central obesity
- Hypertension
- High blood glucose
- High TGL
- Low HDL
Explain the process of dietary triglyceride metabolism
- Digested in the duodenum and absorbed in proximal ileum
- Pancreatic and intestinal lipase and bile acids hydrolyze triglycerides to glycerol, monoglycerides, and fatty acids
Specific concentrations of TGL
- Desirable
< 150 mg/dL
Electrophoretic pattern of Type IIa
Increased beta band on electrophoresis
The effect of excess intracellular cholesterol on the cell
Downgrades HMG-CoA reductase activity, inhibits expression of LDL receptor, induces the synthesis of proteins involved in reverse cholesterol transport
HDL cholesterol precipitation methods
- Precipitate apo B-containing lipoproteins
- Centrifuge and analyze supernatant (HDL)
- Use direct assay to mask non-HDL fractions so they don’t react w/ enzymes used to measure cholesterol
The importance of apolipoprotein C-II and LPL for TGL hydrolysis in exogenous pathway
C-II activates LPL causing rapid hydrolysis of TGL into free fatty acids to be taken up by adipose or muscle cells
Lack proper forms of apo E to allow liver to identify chylomicron remnants and IDL, diagnosed at age 20 or higher, increased total cholesterol and TGL, normal to decreased LDL, increased IDL
Dysbetalipoproteinemia/ Type III
Electrophoretic pattern of Type I
Intense band at point of application or at chylomicrons
The specific site in the intestine where chylomicrons are assembled in the exogenous pathway
Intestinal epithelial cells
Four detrimental effects of oxidized LDL
- Macrophages are transformed into foam cells
- Cytotoxic effects are exerted on endothelial cells
- Platelet activation is increased
- Migration and proliferation of smooth muscle cells stimulated
How the chylomicron remnant is formed in the exogenous pathway
What remains of free fatty acids to enter the liver (Cholesterol esters) (B-48 and Apo E)
VLDL
- % TGL
- % Phospholipids
- % Cholesterol
- % Protein
- Apolipoproteins
- 55% TGL
- 18% phospholipid
- 19% cholesterol
- 8 % protein
- apo B-100, C-I, C-II, C-III, E
Genetic disorder in which there is a defect in synthesis or secretion of lipoproteins containing apo B; LDL is absent in homozygotes; total cholesterol usually < 30 mg/dL
Abetalipoproteinemia
Specific concentrations of LDL
- High
160-189 mg/dL
Fat absorption problems causing failure to thrive in infancy, mental and physical retardation, blindness, and acanthocytes on PBS
Abetalipoproteinemia
(At least) five modifiable risk factors for coronary artery disease
- Hypertension
- Smoking
- Obesity
- Diet
- Alcohol
- Stress
- High lipids
Basic structure of cholesterol
A steroid alcohol w/ 27 carbon atoms arranged in a tetracyclical sterane ring system
Total cholesterol 40-125 mg/dL, normal to elevated TGL, familial severe HDL and apo A-I deficiency, hyperplastic orange-yellow tonsils and adenoids plus hepatosplenomegaly
Hypoalphalipoproteinemia (Tangier disease)
Specific concentrations of TGL
- Very high risk
> =500 mg/dL
Transports dietary lipids that are absorbed by the intestine to the liver and peripheral tissues; TGL digested in duodenum and proximal ileum through action of pancreatic and intestinal lipases and in the presence of bile acids
Purpose of the exogenous pathway for dietary lipids
Empirical formula and three sources of fatty acids
R-COOH
- Diet (largest source)
- Adipose tissue
- Biosynthesis of all but the “essential fatty acids”
Discuss progression from fatty streaks to fibrous plaques to complicated lesions in atherosclerosis
Plaque deposited in blood vessels, inflammation allows lipids to come in and start consuming fat (foam cells), lumen decreases, accumulation of fibrous cap, then platelet thrombosis and fibrin deposits creating a necrotic core w/ debris
Three uses of intracellular cholesterol hepatocytes
Repackaged and secreted on lipoproteins converted to bile salts; directly secreted into bile
Specific appearance of serm/plasma w/ expected CHOL or TGL concentrations
- Normal TGL
Clear
Electrophoretic mobilities of LDL
Beta region
Specific appearance of serm/plasma w/ expected CHOL or TGL concentrations
- TGL > 500 mg/dL
Opaque/milky
Core of nonpolar, neutral lipids surrounded by more polar amphipathic lipids on the surface, contains one or more specific proteins; DIAGRAM IN LECTURE
Structure of lipoproteins
Common disorder, elevated VLDL, elevated LDL, increased total cholesterol, increased TGL
Combined hyperlipoproteinemia/Type IIb
Facilitates uptake of chylomicron remnant and IDL
Apo E
Specific concentrations of TGL
- Borderline
150-199 mg/dL
Macrophages accumulate excess cholesterol and become these (atherogenic)
Foam cells
The importance of apo E for hepatic uptake of the chylomicron remnant in the exogenous pathway
Required for hepatic endocytosis (entrance into the liver)
Describe the catabolic process of beta-oxidation
Shortens fatty acid chain from carboxyl end of molecule to form acetyl-CoA; condensed w/ oxaloacetate to form citrate to enter the Kreb’s cycle (yields more energy than catabolism at glucose)