Lipoprotein Metabolism Flashcards
What is the composition of a chlyomicron?
90% TAG, 2% protein, 3% Phospholipids, 5% cholesterol
What is the composition of VLDL?
60% TAG, 5% protein, 15% Phospholipids, 20% cholesterol
What is teh composition of LDL?
8% TAG, 20% protein, 22% Phospholipids, 50% cholesterol
What is the composition of HDL?
5% TAG, 40% protein, 30% Phospholipids, 25% cholesterol
Where is ApoA-1 synthesized and found?
synthesized in the liver and intestine and found on almost all HDL particles.
What is the major structural protein of chylomicrons, VLDLs, IDLs, and LDs?
ApoB
(1) autosomal recessive
(2) loss of function mutation in gene encoding microsomal triacylglycerol transfer protein (MTP)
(3) chylomicrons, VLDLs, LDLs and apoB are undetectable in plasma leading to lipid malabsorption
(4) extremely low plasma levels of cholesterol and TAG
(5) Symptoms: early childhood, diarrhea, failure to thrive, deficient of fat soluble vitamins, spinocerebellar degeneration, pigmented retinopathy, acanthocytosis
Abetalipoproteinemia
(1) Deficiency of LPL, abnormal LPL, or apo C-II deficiency
(2) slow clearance of chylomicrons and VLDL
(3) fasting plasma is turbid and develops creamy supernatant at 4*C
(4) Symptoms: manifests in childhood, recurrent episodes of severe abdominal pain due to acute pancreatitis, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly
Familial Lipoprotein Lipase (LPL) Deficiency
(1) autosomal recessive
(2) mutation in ATP-binding cassette (ABC) transporter family [ABCG5 and ABCG8]
(3) due to increased absorption of plant sterols in intestine and reduced transport of sterols into bile by liver
(4) impaired cholesterol trafficking
(5) elevated levels of LDL cholesterol
(6) Symptoms: tendon xanthomas, premature atherosclerosis
(7) episodes of hemolysis due to incorporation of plant sterols in RBC membranes
Sitosterolemia
(1) autosomal codominant
(2) mutations in LDL receptor gene, mostly in ligand binding region on exon 4
(3) high LDL-C levels (200-400 mg/dL in heterozygotes, > 500 mg/dL in homozygotes)
(4) Syqmptoms: cutaneous xanthomas, accelerated atherosclerosis, corneal arcus, tendon xanthomas
(5) High incidence in Afrikaners, Christian Lebanese, and French Canadians
Familial Hypercholesterolemia (FH)
(1) autosomal codominant
(2) due to mutation in gene encoding ABCA1
(3) HDL is rapidly cleared from circulation
(4) Low plasma HDL-C levels (
Tangier Disease (ABCA1 Deficiency)
(1) autosomal recessive
(2) mutation in gene encoding plasma enzyme LCAT
(3) increased level of free cholesterol in lipoproteins (from 25% to 70% of total plasma C)
(4) lack of normal cholesterol esterification
(5) impairs formation of mature HDL
(6) low plasma concentraions of CE and lysolecithin, abnormal LDL and VLDL in circulation
(7) Symptom: progressive corneal opacification, variable hypertriglyceridemia
Familial Lecithin Cholesterol Acyltransferase (LCAT) Deficiency
decreased thyroid function does what to LDL particles and LDL oxidation?
it increases the number of LDL particiles and promotes LDL oxidation
what does decreased activity of LPL lead to?
hypertracyllycerolemia
thyroid hormones do what:
activate LDL receptors
stimulate CETP
stimulate LPL, HL
decreases oxidation of LDL
Are lipids hydrophobic or hydrophillic? soluble or insoluble in blood?
hydrophobic and insoluble in blood
how are lipids transported in the bloodstream?
packaged as lipoproteins
what determines the density of a lipoprotein?
the amount of protein per particle
What is the major apolipoprotein for chylomicrons?
ApoB-48
What is the major apolipoprotein for chylomicron remnants?
ApoB-48
What is the major apolipoprotein for VLDL?
ApoB-100
What is the major apolipoprotein for IDL?
ApoB-100
What is the major apolipoprotein for LDL?
ApoB-100
What is the major apolipoprotein for HDL?
ApoA-1
