Relation of erythrocyte Na+-K+ ATPase activity and cholesterol and oxidative stress in patients with type 2 diabetes mellitus.
BACKGROUND
Diabetic patients are at high risk of atherosclerotic complications, and factors associated with this include hypercholesterolemia, hemorheologic disturbances in erythrocytes and oxidative stress. We, therefore, carried out a study in type 2 diabetic patients to determine the relationships of erythrocyte Na+-K+ ATPase activity, plasma cholesterol and oxidative stress in this population.


METHODS
Erythrocyte Na+-K+ ATPase activity and its relationship between plasma cholesterol and thiobarbituric acid reactive substance (TBARS, a marker of oxidative stress) were studied in type 2 diabetic patients with (n = 26) or without angiopathy (n = 30). Na+-K+ ATPase activity was measured by a colorimetric enzymatic method. Plasma TBARS levels were determined spectrophotometrically. Diabetic patients were classified according to plasma cholesterol concentrations as normo- or hypercholesterolemic (plasma total cholesterol > 5.18 mmol/L).


RESULTS
Diabetic patients with or without angiopathy had lower erythrocyte Na+-K+ ATPase activity (p < 0.001 and p < 0.001 respectively) and higher plasma TBARS levels than healthy subjects (n = 20) (p < 0.001 and p < 0.001 respectively). Na+-K+ ATPase activity in the diabetic patients with angiopathy was lower than in the diabetic patients without angiopathy (p < 0.001). In the diabetic patients both with and without angiopathy, hypercholesterolemic patients had lower erythrocyte Na+-K+ ATPase activity and higher plasma TBARS levels than normocholesterolemic patients (p < 0.001, p < 0.001 respectively) There was no difference in the plasma TBARS concentrations between diabetic patients with and without angiopathy. There were negative correlations between erythrocyte Na+-K+ ATPase activity and both plasma cholesterol (r = -0.72) and plasma TBARS (r = -0.46) and a positive correlation between plasma cholesterol and TBARS (r = 0.42).


CONCLUSIONS
Elevated plasma cholesterol may be responsible for the inhibition of erythrocyte Na+-K+ ATPase activity. Together with elevated cholesterol, free radical-induced mechanisms may be involved in the inhibition of Na+-K+ ATPase activity.
Konukoglu
Dildar
D
Department of Biochemistry, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey. dkonuk@yahoo.com
Kemerli
Gülhan Demiriz
GD
Sabuncu
Tevfik
T
Hatemi
Hüsrev
H
D000328:Adult; D002784:Cholesterol / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications / Q000201:enzymology / Q000378:metabolism*; D003925:Diabetic Angiopathies / Q000150:complications; D004912:Erythrocytes / Q000201:enzymology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*
D002784:Cholesterol; D000254:Sodium-Potassium-Exchanging ATPase