Geraniol alleviates diabetic cardiac complications: Effect on cardiac ischemia and oxidative stress

The present study was planned to assess the possible protective effect of geraniol on cardiovascular complications in an animal model with diabetes. Diabetes was induced in rats by a single streptozotocin injection. In the treated group, geraniol (150mgkg^-1day^-1) was administered orally starting from the 15th day after induction of diabetes, and ending after 7 weeks; diabetic control rats were given vehicle for the same period. At the end of the study, cardiac contractility was assessed by using a Millar microtip catheter in anesthetised rats, and cardiac conductivity determined by a surface ECG. Serum levels of glucose, cholesterol, triglyceride and adiponectin as well as urine 8-isoprostane were determined. In addition, cardiac superoxide dismutase (SOD) and catalase activity were measured. Geraniol administration significantly alleviated the attenuated cardiac systolic function associated with diabetes as indicated by inhibiting the decrease in the rate of rise (dP/dt_max) in ventricular pressure and the increase in systolic duration observed in diabetic rats. In addition, geraniol alleviated impaired diastolic function as shown by inhibiting the decrease in the rate of fall (dP/dt_min) in ventricular pressure and increased isovolumic relaxation constant (Tau) observed in diabetic rats. ECG recordings showed that geraniol prevented any increase in QTc and T-peak-T-end intervals, and markers of LV ischemia and arrhythmogenesis, seen in diabetic animals. Geraniol suppressed the exaggerated oxidative stress as evidenced by preventing the increase in 8-isoprotane. In diabetic heart tissue, geraniol prevented the inhibition in catalase activity but did not affect the heart SOD. Geraniol partially reduced hyperglycemia, prevented the hypercholesterolemia, but did not affect the serum level of adiponectin in diabetic animals. Results obtained in this study suggest that geraniol provides a potent protective effect against cardiac dysfunction induced by diabetes. This ameliorative effect could be attributed to its suppression of oxidative stress.