Role of tea polyphenols in the prevention and treatment of LVH induced by high levels of fat, salt and fructose and the related mechanisms

Abstract

Objective To establish a rat model of left ventricular hypertrophy ( LVH ) by feeding the rats with high levels of fat,salt,and fructose and to investigate the possible mechanism of action of tea polyphenols ( TP ) in inhibition of LVH.Methods 50 SD rats were divided into normal group and model group.The rats in the model group were fed with high levels of fat,salt,and fructose for 8 weeks.According to blood pressure level ( ＞ 130 mm Hg ),the rats were randomly divided into model control group,captopril group ( 25 mg·kg-1 ),high-dose TP group ( 200 mg·kg-1 ),and low-dose group TP ( 50 mg·kg-1 ) and then were administrated the medications for 4 weeks with the same previous feeding.Blood pressure was examined at an interval of 2 weeks.At the end of medicine administration, the rats was detected by cardiac ultrasound imaging.Serum levels of Ang Ⅱ and TGF-β were determined by enzymelinked immunosorbent assay, and TNF-α level was determined by radioimmunoassay.Obesity index ( OI ),myocardium proliferation index ( MPI ),and cardiac weight index ( CWI ) were measured and calculated.Results As compared with the normal rats,blood pressure was elevated significantly in model rats (P＜0.01);levels of Ang Ⅱ,TNF-α,and TGF-β1 were higher (P＜0.01);OI and MPI were significantly increased (P＜0.05 and P＜0.01）；heart ejection fraction (EF) and left ventricular posterior wall thickness (LVPWT) were increased and left ventricular shortening fraction (FS)was decreased significantly(P＜0.01);E/A value was less than 1 in some model rats.After treatment with TP(200mg·kg-1 or 50mg·kg-1)or captopril,the elevated blood in the model rats markedly declined；and OI and MPI decreased,LVPW and EF were declined significantly (P＜0.01 and P＞0.05),and FS was elevated significantly (P＜0.01 or P＜0.05);no E/A value of ＜1 occurred;levels of Ang Ⅱ,TNF-α,and TGF-β1 were decreased significantly (P＜0.01).Conclusions For this rat model,TP can reduce blood pressure and plays a role in the inhibition of LVH,which may be associated with a decrease in levels of Ang Ⅱ,TNF-α,and TGF-β1. Key words: Tea polyphenols; Left ventricular hypertrophy; Cardiac ultrasound; Ang Ⅱ; TNF-α