The impact of daily spermidine application on arterial blood pressure and other secondary parameters will be evaluated in a double-blind single center 46 patients cross-over study.

Arterial hypertension is a central risk factor for cardiovascular disease, major cardiovascular events and mortality. Treatment of arterial hypertension necessitates lifestyle modifications, but often also requires medical intervention. In most cases, a combination of two or more anti-hypertensive drugs is recommended and necessary for reaching the target blood pressure levels.

Hypotheses / research questions/objectives Spermidine potentiates the blood pressure lowering effect of standard anti-hypertensive medications, particularly when a combination of at least two first-line drugs (as recommended by the European Society of Cardiology guidelines) has not resulted in sufficient and adequate blood pressure control.

Approach/methods Spermidine Anti-Hypertension Study (SMARTEST) is a prospective, randomized and double-blind placebo-controlled single-centre trial with a balanced 2x2 crossover design, where 46 medically pre-treated hypertensive patients will be subsequently treated with spermidine and placebo (each for eight weeks) in two arms of opposite treatment sequence. A washout period of four weeks will separate the two intervention periods in both arms.

Patients will undergo physical examination, ECG (electrocardiogram), echocardiography, and blood draws at four time points coinciding with the baseline and termination of each treatment at: 0, 8, 12, and 20 weeks of/after recruitment at the Department of Cardiology, Medical University of Graz. In addition, 24-hour ambulatory blood pressure (24-h BP) monitoring (BPM; Mobil-O-Graph®) and on-site blood pressure will be obtained (the device will be sent back to the hospital the following day) at these time points. A 6-minute walk test (6MWT) will be performed at every visit.

Spermidine will be administered orally as an approved dietary supplement (spermidine-rich wheat germ extract) at a dose of 4 mg spermidine per day for eight weeks. The primary outcome will be arterial systolic blood pressure at 24h BPM. Further secondary outcomes/safety outcomes will be:

24-h BP: analysis of systolic, diastolic and mean arterial blood pressures and pulse wave analysis; on site ambulatory blood pressure; 6 minute walk test distance (difference in meters); laboratory analysis; ECG - standard parameters; Echocardiography: standard parameters as well as strain analysis

Inclusion Criteria:

• Able to provide signed and dated informed consent form
• Persistant arterial hypertension with systolic blood pressure above 150 mmHg during hospitalisation and the day of randomisation
• Stable anti-hypertensive medication with at least two guideline-recommended anti-hypertensive drugs

Exclusion Criteria:

• Systolic blood pressure ≥180mmHg on the day of randomisation
• Spermidine intolerance
• Significant renal impairment defined as glomerular filtration rate < 45ml/min
• Insulin-dependent diabetes mellitus (IDDM)
• Wheat allergy or gluten intolerance
• Life expectancy of less than 12 months
• Participation in another clinical trial

individual data will only be shared after approval of the local EC