[Lipoproteins containing apolipoprotein A-I and reverse transport of cholesterol]

The antiatherogenic HDLs are heterogeneous in terms both of hydrated density and of lipoprotein composition. The LpA-I and LpA-I: A-II particles seem to be different from a metabolic point of view, and LpA-I and LpA-IV are apparently the only ones involved in the antiatherogenic action of HDLs. Alcohol consumption causes an increase in LpA-I: A-II, but not in LpA-I. Specific HDL binding sites have been demonstrated in various tissues, including steroidogenic tissues, liver cells and peripheral cells. Apolipoproteins A-I, A-IV and A-II are possible ligands. After binding to the uptake site, HDLs allow cholesterol supply to the cells, on one hand, and the removal of cholesterol for "reverse cholesterol transport" from peripheral tissues to the liver on the other hand. In addition, the interaction of the various HDL subfractions can cause different metabolic effects: cholesterol efflux from the adipocytes of cholesterol-laden mice is influenced by the uptake of LpA-I and LpA-IV on receptors, while apolipoproteins A-II are antagonists for this effect.