The purpose of this study is to determine the effect of remote ischemic preconditioning (RIPC) on blood pressure and its vascular protection effect among Chinese young healthy adults and primary hypertensive patients stage I.

Hypertension is one of the most common world-wide chronic diseases, and it is one of major independent risk factors of atherosclerotic cardiovascular diseases (ASCVD) especially among middle-aged and elderly. Recently, a study indicates that in a normotensive elderly without cardiovascular diseases history, continuous RIPC for 30 days lowers systolic blood pressure for 6 mmHg and diastolic blood pressure for 3 mmHg. Another study shows a 7-day RIPC intervention improves endothelium-dependent flow mediated dilation(FDM) and cutaneous vascular conductivity(CVC) in 13 healthy young males. In addition, studies demonstrate that microRNA-126 and microRNA-34a are endothelial specific microRNAs which are expressed in human PBMCs. MicroRNA-126 is responsible for keeping the integrity of vascular endothelial, promoting the proliferation, mobilization, and migration of endothelial progenitor cells(EPCs), reducing arterial intimal hyperplasia, and reduce adhesion of neutrophils to vascular endothelial. In contrast, microRNA-34a is related to the aging of endothelial cells, which is found over-expressed in senile endothelial cells. Together the investigators use microRNA-126 and microRNA-34a to explore whether RIPC produces vascular endothelial protection effect. In summary, the investigators propose a hypothesis that RIPC might have a blood pressure lowing effect and protect vascular function both in Chinese healthy young adults and primary hypertensive patients. The term "primary hypertension stage I" indicates those with blood pressures ranging from 140 to 159 mmHg systolic and/or 90 to 99 mmHg diastolic. Accumulating evidences suggest that subjects with primary hypertension stage I are associated with higher incidence of ASCVD. However, there is no available data to investigate a nonpharmacologic therapy for primary hypertension stage I until now, and there is no prospective, randomized, controlled, single-blind clinic trial to investigate the effect of RIPC on blood pressure and its vascular protection effect. The investigators hypothesize that RIPC may lower both SBP and DBP, and it improves vascular function in Chinese healthy young adults and subjects with primary hypertension stage I. To address these assumptions, the present study is designed to study the effect of RIPC on blood pressure and its vascular protection effect, using FMD, PWV, central arterial pressure, RHI(EndoPAT) and the quantification of microRNA-126 and microRNA-34a in peripheral blood monocyte(PBMC) as indicators among Chinese healthy young adults and primary hypertensive patients stage I over a 1-month follow-up period.

Inclusion Criteria:

• Subjects range from 18 to 80 years old.
• Blood pressure is normal or primary hypertension stage I(systolic blood pressure 140 to 159 mmHg and/or diastolic blood pressure 90 to 99 mmHg).
• No history of smoking( smoking can eliminate the effect of RIPC) or quit smoking for at least 1 years.
• No intake of caffeine or caffeine-containing substances during the process of this trial(caffeine can eliminate the effect of RIPC).
• Provide informed consent and willingness to cooperate with the study protocol.

Exclusion Criteria:

• Less than 18 years old or above 80 years old.
• Secondary hypertension.
• Pregnant or lactating females.
• Systemic diseases such as diabetes, HIV/AIDS, liver disease, chronic renal failure, tuberculosis, and autoimmune diseases.
• Medical history of cardiovascular disease: acute myocardial infarct, stable angina, unstable angina, heart failure, atrial fibrillation, atrioventricular blockade, peripheral vascular disease or cerebrovascular accident.
• Patients who are unfavorable of long-term follow-up or poor compliance.
• Patients who are considered unfavorable to take part in this trial by investigators.