Cholesterol bound to hemoglobin in normal human erythrocytes: a new form of cholesterol in circulation?

Objective: To study lipid fraction that is occasionally observed in red blood cell (RBC) hemolysate (supernatants from which membranes were separated).

Study Design: Plasma lipid profiles, cholesterol (Ch) and phospholipids (PL) in intact RBCs, RBC membranes and hemolysates were examined in young healthy male population in winter and summer.

Results: The RBC Ch and PL content was significantly higher than in membranes, both in winter and summer. The "excess" of cholesterol (associated with phospholipid) was bound to hemoglobin yielding Hb-lipid adduct (Hb-Ch), the pools in the RBC membrane remaining virtually unaltered. Levels of hemoglobin-lipid complex (Hb-Ch), which were significantly higher in winter than in summer (30% and 19% of the total Hb, respectively), positively correlated with plasma HDL cholesterol levels.

Conclusion: To our knowledge, this is the first demonstration of cholesterol binding to Hb. The results suggest influence of plasma lipoprotein metabolism on the formation of Hb-Ch.