Glucose induces lipid peroxidation and inactivation of membrane-associated ion-transport enzymes in human erythrocytes in vivo and in vitro.
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-doxy-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 without the formation of lipid-MDA adduct. Kinetic studies show that reductions in Na(+)-K(+)-ATPase and Ca+2-ATPase activities precede the 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 suggest 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.
Rajeswari
P
P
Department of Medicine, University of Southern California, School of Medicine, Los Angeles 90033.
Natarajan
R
R
Nadler
J L
JL
Kumar
D
D
Kalra
V K
VK
D000251:Adenosine Triphosphatases / Q000097:blood*; D001769:Blood; D000252:Calcium-Transporting ATPases / Q000097:blood; D002241:Carbohydrates / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D004909:Erythrocyte Indices; D004912:Erythrocytes / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood; D050356:Lipid Metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008315:Malondialdehyde / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood
D002241:Carbohydrates; D016861:Cyclooxygenase Inhibitors; D006893:Hydroxyeicosatetraenoic Acids; D016859:Lipoxygenase Inhibitors; D008315:Malondialdehyde; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D003847:Deoxyglucose; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose