Abstract

Excess carbohydrate in the diet may initiate a chronic state of oxidative stress exacerbating the clinical and biochemical symptoms of diet-induced type 2 diabetes, especially glucose intolerance, lipid abnormalities and cardiovascular complications. This study has tested whether green tea, rich in antioxidants, improves both cardiovascular symptoms and glucose intolerance and also reduces oxidative stress in rats fed a high carbohydrate diet. Male 8 week old Wistar rats were fed a diet including fructose and condensed milk (each 40%) for 16 weeks (112 days); control rats were fed corn starch. Green tea-containing food was started from day 1 for the prevention protocol and from day 56 for the reversal protocol. High carbohydrate diet-fed rats showed glucose intolerance, hypertension, mild left ventricular hypertrophy, approximate doubling of cardiac interstitial and perivascular collagen deposition, increased passive diastolic stiffness and increased plasma malondialdehyde concentrations. Administration of green tea to high carbohydrate diet-fed rats prevented and reversed glucose intolerance and the increased systolic blood pressure, left ventricular wet weight, interstitial collagen and passive diastolic stiffness. Plasma malondialdehyde concentrations were also normalized. In summary, treatment with green tea both prevented and reversed the cardiovascular remodeling and metabolic changes seen in high carbohydrate-fed rats suggesting a chronic state of oxidative stress plays a key role in the symptom initiation and progression. Further, green tea may be a useful complementary therapy in diet-induced type 2 diabetes.

Keywords: Green tea, remodeling, obesity, diabetes, rats, oxidative stress, carbohydrate, antioxidants, cardiovascular, intolerance, hypertension, diastolic stiffness, plasma malondialdehyde, systolic blood pressure, nephropathy, retinopathy, insulin, polyphenolic compounds, epigallocatechins, cardiovascular diseases, insulin resistance, dyslipidemia, glucose transporter, ameliorated hyperglycemia, echocardiography, Zoletil, Xylazil, anesthesia, euthanasia, standard error of mean, SEM, hypertrophy, lipoxygenases, cycloxygenase, xanthine oxidase, metalloproteinases, gluconeogenic enzymes