Severe hypoglycemia can lead to fatal cardiac arrhythmias. Our studies have shown that diabetes, per se, increases the risk of hypoglycemia-induced mortality in rats. It was hypothesized that excess oxidative stress, associated with diabetes, increases the heart’s susceptibility to hypoglycemia-induced fatal arrhythmias. To test this hypothesis, Sprague Dawley rats were made diabetic (streptozotocin 65 mg/kg) and randomized to two treatment groups: 1) antioxidant Vitamin E (400 mg/kg/day; n=18) or 2) control (vehicle, n=16) injected subcutaneously over 8 days. Then, rats underwent hyperinsulinemic (0.4 units/kg/min) severe hypoglycemic (10-15 mg/dl) clamps for 3 hours with continuous electrocardiogram recording. Confirming its antioxidant properties, Vitamin E treatment significantly reduced oxidative stress in the heart 3.3-fold versus controls (Figure). As compared to hypoglycemia-induced mortality of 38% in controls, Vitamin E treatment significantly reduced mortality to 6% (p<0.05; Figure). Additionally, Vitamin E treatment reduced 3rd degree heart block (6%) vs. control (46%; Figure). Overall, these results suggest that 1) oxidative stress in diabetes increases the heart’s susceptibility to hypoglycemia-induced arrhythmias, and 2) Vitamin E treatment reduces oxidative stress and reduces both cardiac arrhythmias and mortality to insulin-induced severe hypoglycemia.
C.M. Reno: None. M.B. Oxspring: None. J. Bayles: None. I. Holiday: None. Y. Huang: None. S.J. Fisher: None.
National Institutes of Health (5T32DK091317, R01NS070235); JDRF (3-APF-2017-407-A-N)
