Cardiovascular effects after chronic administration of green tea in diabetic rats

      Green tea (Camellia sinensis) is being widely studied for its beneficial effect in the treatment and prevention of human diseases. Several epidemiological studies and clinical trials showed that green tea may reduce the risk of many chronic diseases, including cardiovascular disease. The aim of this work was to evaluate the effects of C. sinensis tea on cardiovascular parameters in streptozotocin (STZ) induced diabetic animals. Experiments were performed on male Wistar rats weighing 260–300 g. The animals were randomly divided in four experimental groups: control water group (CWG), n=6; Green tea treated group (CTG), n=8; Diabetic water group (DWG), n=6; Diabetic green tea treated group (DTG), n=5. Diabetes was induced by a single injection of STZ (50 mg/kg, iv) and the animals were monitored for 21 days, CTG and the DTG the tea was administered by the same period. We observed increase of blood pressure in CTG (128±3 mmHg) compared to CWG (106±2 mmHg), decrease in DWG (99±1.5 mmHg) and DTG showed similar results to control group (111±4 mmHg). In heart rate CWG (360±7 bpm), CTG (341±8 bpm), DTG (328±4 bpm) and decreasing in DWG (295±11 bpm). The total power of the heart rate variability was reduced in DWG (8.8±0.7 ms2) in comparison with all groups (CWG 18±1.3 ms2; CTG 16±1.1 ms2; DTG 15±1.6 ms2). The blood pressure variability decrease in DWG (7.5±0.2 mmHg2) compared to CWG (23±3.2 mmHg2) and recovery in DTG (15±4.4 mmHg2). Sympathetic modulation of the blood pressure variability (LF) decreased in DWG (0.8±0.2 mmHg2) compared with other groups (CWG 2.5±0.4 mmHg2; CTG 3.7±0.6 mmHg2; DTG 3.1±0.8 mmHg2). We suggest that green tea treatment can influence the autonomic control, and in some cases, as in diabetes, an improvement of these parameters, although the blood pressure in the CTG increased.
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