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I have always had trouble grasping the physiology of lipoprotein cholesterol transport. The "standard" description found in the literature is that liver synthesizes cholesterol which is carried in "forward" transport to peripheral organs by VLDL (and LDL?), while "reverse" transport is mediated by HDL. Most tissues can synthesize their own cholesterol as well (which makes one wonder what cholesterol transport is needed for in the first place). The figure below sums it up (shamelessly taken from this review).

Figure from Fielding and Fielding, 1995

My question: what are the net rates of transport (fluxes) in this system?

Does the liver actually provide net cholesterol to pheripheral tissues, or is it the other way around? Or is the net close to zero? I can imagine this differs between peripheral tissues, some might be net producers and others may be net consumers, but reviews typically lump everything except the liver together as "the periphery". Perhaps some tissues become net cholesterol producers in certain situations, and consumers in others?

I can't find any data on this in the literature (reviews tend to focus on molecular details of lipoproteins, receptors etc.) but this is not my field and I'm sure the data is out there somewhere. I imagine people have done isotope tracing studies to quantify the rates of transport.

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  • $\begingroup$ fantastic question! (I think) cholesterol flux is inherently difficulty to study... really depends on the state of the person - fasting or fed. Not sure if anyone has good tracer methods... in my dissertation we did some work with VLDL secretion from the liver (but that was just to look at triglyceride-VLDL secretion rates from the liver)... you give tyloxapol (detergent) which inhibits all peripheral lipoprotein lipase and then increase in VLDL/Triglyceride over time is estimate of liver VLDL secretion see ncbi.nlm.nih.gov/pubmed/20494946 for that technique $\endgroup$ – Vance L Albaugh Dec 30 '15 at 17:26
  • $\begingroup$ Wolf & Chinkes book - Isotope Tracers in Metabolic Research would probably have the techniques if they exist books.google.com/books/about/… $\endgroup$ – Vance L Albaugh Dec 30 '15 at 17:28
  • $\begingroup$ @VanceLAlbaugh Thanks, will check out the book! $\endgroup$ – Roland Dec 31 '15 at 7:53
  • $\begingroup$ If I'm not mistaken, shouldn't the CE exchange occur between HDL and VLDL? as opposed to HDL and LDL as shown here.. I mean the CETP thing. $\endgroup$ – Polisetty Mar 7 '16 at 16:51

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