HYPERGLYCEMIA COUNTERBALANCES THE ANTIHYPERTENSIVE EFFECT OF GLUTATHIONE IN DIABETIC-PATIENTS - EVIDENCE LINKING HYPERTENSION AND GLYCEMIA THROUGH THE OXIDATIVE STRESS IN DIABETES-MELLITUS

Diabetes mellitus is associated with hypertension. An antihypertensive effect of the antioxidant glutathione has been recently demonstrated. It has been suggested that hyperglycemia may contribute to the pathop hysiology of hypertension in diabetes by generating an oxidative stres s. In this study, three different tests were performed in ten hyperten sive and ten nonhypertensive diabetic subjects: (1) an oral glucose to lerance test, (2) glutathione i.v. administration (1 g/m(2) bolus + 1 g/m(2) in 2 h), and (3) oral glucose tolerance test + glutathione admi nistration. At -15', 0', 30', 60', 90', 120', and 180' systolic and di astolic blood pressure, plasma glucose, and insulin were measured. Var iations in plasma glucose and insulin levels were not different during each test in the two groups of patients and in test (1) compared to ( 3). Glutathione administration reduced systolic and diastolic blood pr essure in both hypertensive and nonhypertensive diabetic subjects from 30' to 120'. This phenomenon was abolished as glycemia increased afte r oral glucose loading. In hypertensive, but not in nonhypertensive di abetic subjects, a significant increase of systolic and diastolic bloo d pressure was observed at 90' and 120' of the oral glucose tolerance test (p < 0.01), These data show that hyperglycemia can counteract the hypothensive effects of the antioxidant glutathione, suggesting that glucose may impair arterial relaxation by producing free radicals. Als o, it. appears that hypertension in diabetic patients is aggravated by high glucose plasma levels. (C) Elsevier Science Inc,, 1997.