class of lipoproteins that promote transport of cholesterol from extrahepatic tissue to the liver for excretion in the bile; synthesized by the liver as particles lacking a lipid core, they accumulate a core of cholesterol esters during reverse cholesterol transport and transfer them to the liver directly or indirectly via other lipoprotein; HDL also shuttle apolipoproteins C-II and E to and from triglyceride-rich lipoproteins during catabolism of the lipoproteins; serum HDL cholesterol has been negatively correlated with premature coronary heart disease.