EGCG调控db/db小鼠血压生物节律的效应及生理与分子机制

More than 170 million people worldwide have diabetes, and china alone accounts for one third of diabetic population. Hypertension occurs more frequently in these diabetic patients than in those without diabetes. Recent years, duo to change of diets and lifestyle, hypertensive patients were getting younger and younger in China. EGCG is a most abundant tea polyphone. The recent years’ research indicated that EGCG can reduce blood pressure in animal models. More importantly, human population studies found out that consumption of green tea or EGCG significantly reduced systolic and diatonic blood pressure. However, the molecular mechanism of EGCG regulating blood pressure is still unknown. There is no report of EGCG regulating blood pressure circadian rhythm..Blood pressure exists 24 hours circadian rhythm. Approximate 75% human diabetic patients have disrupted blood pressure circadian rhythm with a reduced nocturnal blood pressure dip. Such blood pressure no dipping, independent from the average blood pressure value itself, is associated with increased vascular complication and worsened cardiovascular outcomes in diabetic patients. The molecular mechanism which linking diabetes and disrupted blood pressure circadian rhythm is unclear. Recent research indicated that time-restricted feeding not only affect peripheral circadian clock, but also prevent to develop metabolic syndrome in animal models. Our researches indicated that db/db mouse is a unique model for investigating diabetic associated hypertension and disruption of blood pressure circadian rhythm. The present studies will investigate: 1) feeding of 0.1% EGCG diet prevents db/db mice to develop hypertension and disruption of blood pressure circadian rhythm; 2) feeding of 0.1% EGCG diet restores mornal blood pressure and blood pressure circadian rhythm of db/db mice; 3) measurement of the time-of-day variation of energy metabolism, locomotor activity, micro-vascular contraction, concentration of insulin, rennin, angiotensin II, aldosterone, glucocorticoid, epinephrine and norepinephrine to dissect physiological mechanism of EGCG regulating blood pressure circadian rhythm in db/db mice，4) using mesenteric arteries and vascular smooth muscle cells investigate EGCG regulating the ROCK2 through Bmal1to set up a new molecular mechanism of EGCG regulating blood pressure circadian rhythm in db/db mice. Our previous researches revealed that Bmal1 and ROCK2 are critical molecules for control blood pressure circadian rhythm in mesenteric arteries. 5) potential novel molecule(s) and signaling pathways by RNA sequencing data from mesenteric arteries isolated from db/db mice treated by feeding of 0.1% EGCG diet and control mice . The results of present studies will have significant impact on our better understanding of EGCG regulating blood pressure circadian rhythm, and will provide useful information for developing specific tea production for type 2 diabetic patients.

EGCG是茶叶中茶多酚的主要组成成分，具有降低动物和人群血压的功能。血压具有生物钟节律。我们前期的实验表明EGCG具有预防db/db小鼠血压生物节律丧失的效应。但EGCG调节血压生物节律的分子机制还不清楚。本项目研究进食含EGCG的饲料调控db/db小鼠血压生物节律的效应；在能量代谢、与血压相关的激素和神经递质及微血管收縮力等的变化节律上，研究EGCG调控db/db小鼠血压生物节律的生理机制；在微血管和平滑肌细胞中，研究EGCG对维持血压生物节律起重要作用的分子Bmal1和ROCK2的调控，探讨EGCG调节db/db小鼠血压生物节律的分子机制。在微血管的转录组水平上探索EGCG调节db/db小鼠血压生物节律潜在的分子和信号通路。从而揭示进食EGCG调控db/db小鼠血压生物节律的效应及生理与分子机制，为二型糖尿病的预防及保健茶的开发提供理论依据。

茶多酚是茶叶的重要功能成分，具有降低实验动物血压的功能。但其调控血压的分子机制还不清楚，调节血压昼夜节律知之甚少。丧失血压昼夜节律能导致心、脑、肾等靶器官的损害。重新恢复血压的昼夜节律能显著降低心血管疾病的发病率和死亡率。因此，研究茶叶特有次生代谢产物茶多酚（EGCG）和茶氨酸调节高血压模型小鼠的血压及血压昼夜节律的效应及分子机制具有重要的理论和临床意义。.研究结果表明茶多酚干预显著降低了血管紧张素转化酶加盐诱导C57BL/6高血压小鼠白天和夜间的收缩压和舒张压；减轻了高血压小鼠微血管的收缩性和炎症反应；阻止了血管RhoA/ROCK 和PKCα信号通路的激活；抑制了肾脏ENaCα的表达，减少肾脏对Na的吸收。在细胞水平上，EGCG显著降低主基因Bmal1和钟控基因Per2、Cry1、Rev-erbα基因节律的振幅，并且延长节律周期和延后相位。转录组测序结果显示EGCG降低了血管平滑肌细胞生物钟主基因和一些钟控基因的表达，显著增强了Dec1和Dec2基因的表达。腺病毒介导的Dec1基因高表达负调控BMAL1-CLOCK异二聚体的转录激活，从而降低其他生物钟基因的节律。本研究揭示了Dec1负调控BMAL1-CLOCK异二聚体维持血管平滑肌细胞稳态的重要作用。揭示了茶氨酸显著提高主基因Bmal1，Npas2和钟控基因Per2, Cry1和Rorα的振幅，对表达的周期和相位没有影响。同时降低了平滑肌收缩基因CPI-17, ROCK2的振幅。在一些病理情况下（如糖尿病和高血压）血管平滑肌节律基因的表达振幅下降。因此茶氨酸增强平滑肌细胞节律基因的振幅具有潜在的预防和治疗价值。这些研究结果加深了人们对茶叶预防高血压和血压节律失调的认识。同时为研发调节血压昼夜生物节律的新药提供了新的靶向分子。