Lecture 40.txt

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Lecture 40.txt
2010-10-23 15:33:26

Lecture 40 Disorders of lipoprotein metabolism
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  1. What is dyslipidemia?
    Any abnormal concentration of lipid (C, CE, or TAG) in the blood
  2. What is hyperlipidemia?
    • elevated levels of lipids in the blood
    • =hyperlipoproteinemia
  3. What is hypolipidemia?
    • reduced levels of lipids in the blood
    • =hypolipoproteinemia
  4. What is primary dyslipidemia?
    dyslipidemia caused by an inherent defect in lipoprotein metabolism
  5. What is secondary dyslipidemia?
    dyslipidemia caused by another disease (ex. obesity, diabetes mellitus, hypothyroidism)
  6. What is the most common serum profile of dyslipidemia?
    hypertriacylglycerolemia and reduced levels of HDL cholesterol
  7. Why is a blood sample taken after a 12 hour fast?
    to make sure there are no CM from the previous meal
  8. What is the Friedwald Equation?
    LDL-C = Total-C - VLDL-TAG/5 - HDL-C
  9. What is type IIa hyperlipidemia?
    Lipid panel?
    • Elevated LDL, familial hypercholesteremia
    • Deficiency of LDL receptor expression
    • Increase of LDL, elevated C, normal TAG
    • Heterozygous common, homozygous rare
    • Xanthomata (accumulation of lipids) on extremities, corneal arcus, atherosclerosis; risk of cardiovascular disease
    • Diet; reduce intake of cholesterol and fat, combination therapy (HMG-CoA reductase inhibitor = statin and absorption inhibitor, also in combination with niacin
  10. What is type I hyperlipidemia?
    Lipid panel?
    • Familial chylomicronemia (elevated CM)
    • Deficiency in lipoprotein lipase and/or Apo C-II synthesis or function
    • Elevated fasting CM, TAG elevated (fasting plasma turbid with milky CM forming creamy top layer, C normal
    • Rare
    • Eruptive xanthomata, hepatosplenomegaly, pancreatitis
    • No drug therapy, only dietary fat restriction, fat soluble vitamin supplements, diet with medium and short chain TAG (tropical oils) avoid CM production
  11. What is type IV hyperlipidemia?
    Cause? Primary? Secondary?
    Lipid panel?
    • Elevated VLDL, familial hypertriglyceridemia
    • Primary-VLDL overproduction and/or decreased VLDL removal, Secondary-obesity, ethanol intake, estrogen use, insulin resistance
    • Common (1 in 300)
    • Serum opaque, few clinical manifestations, if C elevated=elevated risk of cardio-vascular disease
    • Correct secondary causes by diet/life style changes, combination therapy
  12. What is type IIb hyperlipidemia?
    Causes? Primary? Secondary?
    Lipid Panel?
    • Elevated LDL and VLDL, familial combined hyperlipidemia
    • Primary-overproduction of Apo B-100, Secondary-cluster of precipitating factors; obesity, glucose intolerance, insulin resistance, hypertension
    • Elevated VLDL, TAG elevated, LDL elevated, C elevated, HDL usually decreased
    • Common (1 in 200)
    • No xanthomata, high risk of premature CVD
    • Aggressive treatment, diet, life style, weight loss, combination therapy
  13. What is type III hyperlipidemia?
    Lipid panel?
    • Elevated IDL, familial dysbetalipoproteinemia
    • Polymorphism of Apo E gene(ligand for hepatic Apo E receptor)
    • VLDL remnants (=IDL) and CM remnants elevated, TAG and C elevated
    • Rare
    • Tuberoeruptive and/or striate palmar xanthomata, premature coronary and peripheral vascular diseases
    • Diet, combination therapy
  14. What are scavenger receptors (type A)?
    Receptors on macrophages for damaged LDL (insensitive to cholesterol levels=continuos uptake of damaged LDL
  15. What do macrophages (foam cells) release that leads to an atherosclerosic plaque?
    Cytokines (stimulate inflammation, immune response, collagen synthesis, proliferation of smooth muscle cells, accumulation of calcium)
  16. What are the two best treatments for reducing LDL-C?
    Statins (HMG CoA reductase inhibitors) and Resins
  17. What are two of the best ways to increase HDL-C levels?
    • Fibrates (increase expression of Apo A-I)
    • Niacin (decrease catabolism of Apo A-I)
  18. What is abetalipoproteinemia (CM retention disease)?
    • Loss of function, mutation in gene encoding MTP (microsomal transfer protein)
    • MTP: transfers lipids to nascent CM and VLDL before they are released from enterocytes and hepatocytes
  19. What is Tangier disease (alphalipoprotein deficiency)?
    Defect in ATP binding cassette protein A1 (ABC-A1)
  20. What does ATP binding cassette protein A1 (ABC-A1) do?
    Transfers C from peripheral cells to HDL