Modifications and degradation of high density lipoproteins

It is evident that lipoprotein modifications, degradation and clearance from plasma and interstitial compartments involves both cellular and extracellular processing. Cellular uptake of the intact particle as a whole and/or selective removal of constituent apoproteins and lipids by various parenchymal cells goes on continuously. Regulation of these processes undoubtedly varies tissue to tissue and much remains to be clarified in human tissues in vivo. The metabolic effects of chemical, proteolytic, and lipolytic modification of lipoproteins secondary to transient cellular encounters (e.g. during transit through endothelial barriers, or reversible binding to cells) on apolipoprotein clearance remains to be defined. It is likely that multiple post-secretory modifications occur and together represent subtle regulatory events that modulate lipid shuttle functions and cellular targetting properties of HDL particles.