Gut microbiota was found to play a causal role in the pathogenesis of hypertension. Probiotics were shown to have a potential anti-hypertensive effect in human/rodent studies. This study aims to explore the effect, safety, and underlying mechanisms of the combination of probiotics, containing 10 strains from Lactobacillus and Bifidobacterium, on hypertension, compared with placebo.

Background: Primary hypertension is the leading risk factor of cardiovascular diseases and all-cause mortality, and contributes to severe global health burden. Emerging evidence has shown a close association between gut microbiota and hypertension. Fecal transplantation from hypertensive patients/animals to germ-free mice caused elevation of blood pressure, indicating a causal role of gut dysbiosis in hypertension. Probiotics were found to have a potential anti-hypertensive effect in both human and rodent studies. Based on the investigators' previous findings of metagenomics analysis of hypertensive, prehypertensive patients and healthy control, hypertensive and prehypertensive patients were lack of probiotics. Therefore, the investigators developed this study to explore the effect, safety, and underlying mechanisms of the combination of probiotics, containing 10 strains from Lactobacillus and Bifidobacterium, on hypertension, compared with placebo.

Objective: To explore the effect, safety, and underlying mechanisms of the combination of probiotics on grade 1 primary hypertension and prehypertension.

Study Design: A multicenter, randomized, double-blinded, placebo-controlled pilot study.

Data quality control and statistical analysis: The investigators have invited professional statistic analysts to assist in analyzing data and a third party to supervise data quality.

Ethics: The Ethics Committee of Fuwai Hospital approved this study. Informed consent before patient enrollment is required.

Inclusion Criteria:

1. Age 18~60 years.
2. Grade 1 hypertension and part of prehypertension (initial diagnosis or free from antihypertensive drugs within 2 weeks): 130 mmHg ≤ Average office SBP < 160 mmHg, and/or 85 mmHg ≤ Average office DBP < 100 mmHg, according to the "2018 Chinese Guidelines for Prevention and Treatment of Hypertension" and "National guideline for hypertension management in China (2019)".
3. Patients with informed consent after thorough explanation.

Exclusion Criteria:

1. Antibiotics or probiotics usage within the last 2 weeks.
2. Participants of other clinical trials currently or within last 3 months.
3. Antihypertensive medications usage currently or within last 2 weeks.
4. Diagnosed secondary hypertension
5. History of diabetes mellitus.
6. History of peripheral atherosclerosis.
7. Severe hepatic or renal diseases (ALT >3 times the upper limit of normal value, or end-stage renal disease on dialysis or eGFR <30 mL/min/1.73 m2, or serum creatinine >2.5 mg/dl [>221 μmol/L]).
8. History of stroke (not including lacunar infarction and transient ischemic attack [TIA]).
9. History of coronary heart disease.
10. Sustained atrial fibrillation or arrhythmias at recruitment disturbing the electronic BP measurement.
11. NYHA class III-IV heart failure; Hospitalization for chronic heart failure exacerbation within last 6 months.
12. Severe valvular diseases; Potential for surgery or percutaneous valve replacement within the study period.
13. Dilated cardiomyopathy; Hypertrophic cardiomyopathy; Rheumatic heart disease; Congenital heart disease.
14. Other severe diseases influencing the entry or survival of participants, such as malignant tumor or acquired immune deficiency syndrome.
15. Cognitive impairment or severe neuropsychiatric comorbidities who are incapable of providing their own informed consent.
16. Participants preparing for or under pregnancy and/or lactation.
17. With special diet habits, such as vegetarians.
18. Active gastritis or enteritis; gastrointestinal ulcers or bleeding; post-gastrointestinal surgery, such as intestinal excision.
19. Other conditions inappropriate for recruitment according to the investigators.