Lipids and Lipoproteins Flashcards Preview

206 Myocardial Infarction > Lipids and Lipoproteins > Flashcards

Flashcards in Lipids and Lipoproteins Deck (21)
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What are the sources of cholesterol?

Diet and synthesised by liver from Acety CoA


How is cholesterol excreted?

Bile acids


How is cholesterol regulated in the body?

Negative feedback - inhibits further synthesis of itself by inhibiting HMG-CoA reductase

Insulin/glucagon control - insulin → increases synthesis; glucagon → decreases synthesis

Long term control - inhibition of HMG-CoA reductase → decrease cholesterol

also: reduced cellular uptake by inhibition of cholesterol receptor expression


What is the basic lipoprotein structure?

Non-polar lipid core - mostly TAGs and cholesterol esters

Polar (hydrophilic) outer coat


What is a chylomicron?

Takes TAGs from small intestine → tissues


What do VLDLs do?

Take TAGs from liver → tissues



What is IDL?

Remnant of VLDL and can form LDLs


What are LDLs?

Take cholesterol esters from IDL → tissues


What is HDL?

Free cholesterol scavenger in periphery → liver


How are long chain FAs transported from the intestine?

Converted to TAGs, packaged into chylomicrons → secreted into lacteals

(Exogenous pathway)


how are short and medium chain FAs transported from the intestine?

Secreted into bloodstream as FFAs

Increase in FFAs in blood → insulin secretion → encourage uptake by liver/muscle/tissue

Decrease FFAs in blood between meals → adipocyte release of FFAs


Diagram for major groups of lipoproteins and their actions


What does the exogenous lipid transport pathway include?

Takes lipids from small intestine → tissues via chylomicrons

  1. Chylomicrons secreted into lymph system by intestinal mucosal cells 
  2. Chylomicrons acquire apolipoproteins from HDL circulating in blood (apoC and apoE)
  3. CMs and TAGs broken down → FFAs by lipoprotein lipase (apoC) for the tissues to absorb
  4. Remnants taken up by liver (apoE)


What is involved in the endogenous pathway?

Takes TAGs and Cholesterol to tissues via VLDL  → IDL → LDL

  1. VLDL synthesised in the liver (TAGs + apolipoproteins/cholesterol)
  2. TAGs removed by lipoprotein lipase in capillaries → IDL
  3. Majority IDL donates apolipoproteins to HDL → becomes LDL
  4. LDL taken up by peripheral tissues (provide cholesterol)



What does reverse cholesterol transport invovle?

Transports free/used cholesterol back to the liver

HDL scavengers: free cholesterol in peripheries → liver

Provides apolipoproteins to CMs, VLDL, IDL


What is the clinical definition of familial hypercholesterolaemia?

Increased total cholesterol or LDL

+ Tendon Xanthoma in patient or close relative


What is xanthelasma?

Yellow flat plaques on upper/lower eyelids - lipid-containing macrophages condensing around the socket

Usually due to high cholesterol/atheromatous disease


What is corneal arcus?

Grey opaque line surrounding margin of cornea

Common in Type II Diabetes


What is the pathophysiology of Familial Hypercholesterolaemia?

Genetic disorder - autosomal dominant, though varying effect with homo/heterozygous

Causes LDL Receptor dysfunction - prevents proper uptake of LDL by cells


What investigations can be used for diagnosis of Familial Hypercholesterolaemia?


Total cholesterol >7.5mmol/l

LDL >4.9mmol/l

Plus tendon xanthoma → diagnosis


What is the treatment for Familial Hypercholesterolaemia?


Treatment of associated conditions

Statins - decrease cholesterol synthesis and increase LDL uptake; increase atherosclerotic plaque stability

Fibrates - decrease hepatic secretion + increase peripheral uptake → decrease serum triglyceride

Increase gallstone risk by increasing choleseterol content of bile