Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial.
The polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were measured; urine and blood samples were collected; and endothelial function was measured by EndoPAT technology. In the total group, quercetin did not significantly affect 24 h ABP parameters and office BP. In the subgroup of hypertensives, quercetin decreased 24 h systolic BP by -3·6 mmHg (P=0·022) when compared with placebo (mean treatment difference, -3·9 mmHg; P=0·049). In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison. In the total group and also in the subgroup of hypertensives, vasoactive biomarkers including endothelin-1, soluble endothelial-derived adhesion molecules, asymmetric dimethylarginine, angiotensin-converting enzyme activity, endothelial function, parameters of oxidation, inflammation, lipid and glucose metabolism were not affected by quercetin. In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin. The mechanisms responsible for the BP-lowering effect remain unclear.
1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.
Verena
V
Brüll
1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.
Constanze
C
Burak
2Institute of Clinical Chemistry and Clinical Pharmacology,University Hospital Bonn,53127 Bonn,Germany.
Birgit
B
Stoffel-Wagner
3Institute of Animal Nutrition and Physiology,Christian-Albrechts-University Kiel,24118 Kiel,Germany.
Siegfried
S
Wolffram
4Department of Cardiology,Angiology and Pneumology,University Hospital Bonn,53127 Bonn,Germany.
Georg
G
Nickenig
4Department of Cardiology,Angiology and Pneumology,University Hospital Bonn,53127 Bonn,Germany.
Cornelius
C
Müller
5Department of Biopharmaceutics and Pharmaceutical Technology,Institute of Pharmacy and Biochemistry,Johannes Gutenberg University Mainz,55099 Mainz,Germany.
Peter
P
Langguth
1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.
Birgit
B
Alteheld
6Institute of Medical Biometry,Informatics and Epidemiology,University Hospital Bonn,53127 Bonn,Germany.
Rolf
R
Fimmers
7Institut Prof. Dr. Georg Kurz GmbH,50933 Köln,Germany.
Stefanie
S
Naaf
7Institut Prof. Dr. Georg Kurz GmbH,50933 Köln,Germany.
Benno F
BF
Zimmermann
1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.
Peter
P
Stehle
1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.
Sarah
S
Egert
D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000008:administration & dosage; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002097:C-Reactive Protein / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D002149:Energy Intake; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*; D019697:Onions / Q000737:chemistry; D050177:Overweight / Q000503:physiopathology*; D010349:Patient Compliance; D010936:Plant Extracts / Q000008:administration & dosage*; D058246:Prehypertension / Q000188:drug therapy* / Q000503:physiopathology; D011794:Quercetin / Q000008:administration & dosage*; D016896:Treatment Outcome; D014280:Triglycerides / Q000097:blood; D055105:Waist Circumference
D000959:Antihypertensive Agents; D015415:Biomarkers; D007328:Insulin; D010936:Plant Extracts; D014280:Triglycerides; D002097:C-Reactive Protein; D002784:Cholesterol; D011794:Quercetin
ABP ambulatory blood pressure; ACE angiotensin-converting enzyme; ADMA asymmetric dimethylarginine; BP blood pressure; Blood pressure; Cardiovascular diseases; DBP diastolic blood pressure; Endothelial function; Hypertension; IsoP isoprostanes; MAP mean arterial pressure; PAT peripheral arterial tonometry; Quercetin; RHI reactive hyperaemia index; SBP systolic blood pressure; oxLDL oxidised LDL; sICAM-1 soluble intercellular adhesion molecule 1; sVCAM-1 soluble vascular cell adhesion molecule 1