Effect Of GABA-enriched White Tea On Blood Pressure And Baroreflex Sensitivity In Spontaneously Hypertensive Rats

Hypertension is an independent chronic disease and also an important risk factor forstroke, heart failure and chronic kidney disease. Fifty to sixty percent incidence of strokeand forty to fifty percent of myocardial infarction connect with elevated hypertension.According to the survey results of the2002national prevalence of hypertension and thenumber and structure of our population, China has about200million hypertensionpatients at present, that two patients with hypertension in10adults, accounting for aboutone-fifth of global hypertension. There is an average increased of3.2million newpatients per year in the past decade. As China gradually entering aging society, theincidence of hypertension, as well as various diseases caused by hypertension is boundto a significantly increasing trend.Notably, it is important to prevent and control blood pressure. Research have foundthat it was unable to control the complications of hypertension if only improve bloodpressure, because blood pressure variability(BPV) and arterial baroreflex(ABR) haveinfluence on it in varying degrees.Abnormal blood pressure variability is very common in hypertensive patients,resulting in target organ damage and increased incidence of complications, and is animportant independent risk factor of blood pressure.ABR is one of the most important mechanisms in the regulation of cardiovascularactivities and its main function is to maintain the stability of blood pressure.Baroreflexfunction, expressed as baroreflex sensitivity (BRS).There are varying degrees of ABRdysfunction whether in hypertensive animals or patients with hypertension. There is aclose correlation between ABR functional status and organ damage, and it does notdepend on the level of blood pressure or BPV, which is another independent risk factor.γ-aminobutyric acid (GABA)is a widely present non-protein amino acids in animaland plant, and it has a variety of biological functions, such as improving blood pressureand anti-fatigue. The fresh tea leaves has biosynthesis basis for GABA, but the content inregular tea is not high so that its function can not be prominent. It has found many waysto get high content of GABA in tea through research of its processing tachnic, whichmakes the study of GABA-enriched tea entering a new stage. The researches onGABA-enriched tea by animal experiments and clinical trials found that it can improveblood pressure. Studies also found that the GABA content in regular white tea is higher than other tea, which indicate a potential for producing GABA-enriched white tea.So we suppose that if white tea is more easily to prepare high GABA tea and if theGABA-enriched white tea can improve blood pressure and the BPV and ABR function atthe same time. Therefore, this project intends to further study about successfuldevelopment of GABA-enriched white tea and its function through the following twoparts.Part Ⅰ Determination of GABA in white tea after optimization processing.Water extracts for preliminary treatment and the automatic amino acid analyzer wereused to determine GABA in GABA-enriched white tea and regular white tea. The mainobjectives are:1. to confirm the success of GABA-enriched tea after optimizationprocessing through different GABA content in two kinds of tea.2. to provide a basis fordetermining the dose in following animal experiments.Results:1.The peak area and concentration of GABA showed a good linear relationshipwithin concentration between0.004mg/ml to0.1mg/ml, the correlation coefficient R2=0.9996;The recoveries rate of GABA-enriched white tea and regular white tea were94.81%and90.42%respectively;2.GABA content in GABA-enriched white tea andregular white tea were482mg/100g and59.3mg/100g respectively.Part Ⅱ Experiments of the GABA-enriched white tea on the hemodynamic indexes inspontaneously hypertension rat (SHR) and Wistar-Kyoto (WKY).Monitoring hemodynamic indexes in conscious freely moving rats and improvedSmyth method were used to verify the effect of GABA-enriched white tea on SHR andWKY，including blood pressure, blood pressure variability, heart rate and arterialbaroreflex function, to determine if GABA will affect normal blood pressure and theeffective dose of the pharmacological effects of GABA, providing a reference for thefollowing clinical trial.A total of nine groups were settled: high(5.0g tea/kg.bw), middle(2.5g tea/kg.bw),low (1.25g tea/kg.bw)dose groups, standard control group, negative control group andblank control group for SHR, and high-dose group, negative control group and blankcontrol group for WKY.Results:1.It was found that high，medium-dose and standard group significantlyimprove blood pressure(P<0.05), while other groups had no effect on blood pressure; Inhigh-dose group of SHR,systolic blood pressure decreased an average of17mmHg,whilean average of8mmHg in middle dose group and the standard control group;2.Baroreflex sensitivity level were significantly increased by an average of0.17,0.29and0.16ms/mmHg in the high-dose, middle-dose and standard control group for SHRrespectively;3.Each experimental group have no significant effect on blood pressurevariability;4.Each experimental group had no significant effect on heart rate.Conclusion:1.GABA content in GABA-enriched white tea was significantly higherthan regular white tea, reached the accepted standards of GABA-enriched tea, whichGABA content is greater than150mg/100g,and the optimization processing is succesful;2.No effect were found in normotensive rats on blood pressure, blood pressurevariability,BRS and heart rate.3.Blood pressure and BRS on hypertensive rats wereimproved by GABA-enriched white tea, and the effective dose is above1.2mg/100g BW;No effect were found on blood pressure variability and heart rate.