Glucose induces lipid peroxidation and inactivation of membrane‐associated ion‐transport enzymes in human erythrocytes in vivo and in vitro

Abstract

Erythrocytes of diabetic subjects (non‐insulin dependent) were found to have eight‐ to ten‐fold higher levels of endogenously formed thiobarbituric acid reactive malonyldialdehyde (MDA), thirteen‐fold higher levels of phospholipid‐MDA adduct, 15–20% reduced Na⁺‐K⁺‐ATPase activity with unchanged Ca⁺²‐ATPase activity, as compared with the erythrocytes from normal healthy individuals. Incubation of normal erythrocytes with elevated concentrations (15–35 mM) of glucose, similar to that present in diabetic plasma, led to the increased lipid peroxidation, phospholipid‐MDA adduct formation, reduction of Na⁺‐K⁺‐ATPase (25–50%) and Ca⁺²‐ATPase (50%) activities. 2‐deoxy‐glucose was 80% as effective as glucose in the lipid peroxidation and lipid adduct formation. However, other sugars, such as fructose, galactose, mannose, fucose, glucosamine and 3‐O‐methylmannoside, and sucrose, tested at a concentration of 35 mM, resulted in reduced (20–30%) lipid peroxidation as the enzyme inactivation occur within 30 min of incubation of erythrocytes with high concentration (15–35 mM) of glucose, while lipid peroxidation product, MDA appears at 4 hr and lipid‐MDA adducts at 8 hr. The lipoxygenase pathway inhibitors, 5, 8, 11‐eicosatriynoic acid and Baicalein (5,6,7‐trihydroxyflavone), reduced the glucose‐induced lipid peroxidation by 30% and MDA‐lipid adduct formation by 26%. Indomethacin, a cyclooxygenase pathway inhibitor, had no discernible effect on the lipid peroxidation in erythrocytes. However, the inhibitors of lipid peroxidation, 3‐phenylpyrazolidone, metyrapone, and the inhibitors of lipoxygenase pathways did not ablate the glucose‐induced reduction of Na⁺‐K⁺‐ATPase and Ca⁺²‐ATPase activities in erythrocytes. Erythrocytes produce 15‐HETE (15‐hydroxy‐eicosatetraenoic acid), which is augmented by glucose. These results suggtest that the formation of lipoxygenase metabolites potentiate the glucose‐induced lipid peroxidation and that the inactivation of Na⁺‐K⁺−ATPase and Ca⁺²‐ATPase occurs as a result of non‐covalent interaction of glucose with these enzymes.