title: No effects of quercetin from onion skin extract on serum leptin and adiponectin concentrations in overweight-to-obese patients with (pre-)hypertension: a randomized double-blinded, placebo-controlled crossover trial.
abstract: OBJECTIVE
  Chronic low-level systemic and adipose tissue inflammation has been identified as a major etiologic factor in many chronic diseases, including hypertension and cardiovascular diseases. Evidence from experimental studies suggests anti-inflammatory effects of dietary flavonols such as quercetin.
  
  
  METHODS
  We investigated the effects of regular intake of quercetin on leptin, adiponectin, biomarkers of inflammation, glucose and insulin in overweight-to-obese patients with pre- and stage 1 hypertension. Another objective was to assess the safety of daily quercetin supplementation measured by parameters of liver and kidney function and of hematology. Subjects (n = 70) were randomized to receive a supra-nutritional dose of 162 mg/d quercetin or placebo in a double-blinded, placebo-controlled crossover trial with 6-week treatment periods separated by a 6-week washout period. Two subjects dropped out for personal reasons. Only data from the remaining 68 subjects were included in the analysis.
  
  
  RESULTS
  Compared to placebo, quercetin did not significantly affect serum concentrations of leptin and adiponectin, HOMA-AD or the ratios of leptin/adiponectin and adiponectin/leptin. Neither quercetin nor placebo significantly changed serum C-reactive protein and plasma tumor necrosis factor alpha. Compared to placebo, quercetin did not significantly affect glucose, insulin, HOMA-IR, blood biomarkers of liver and renal function, hematology and serum electrolytes.
  
  
  CONCLUSIONS
  A supra-nutritional dose of 162 mg/d quercetin from onion skin extract for 6 weeks is safe but without significant effects on parameters of systemic and adipose tissue inflammation as well as glucose and insulin in overweight-to-obese subjects with (pre-)hypertension. This trial was registered at www.germanctr.de/ and http://apps.who.int/trialsearch/ as DRKS00000555.
authors.affiliation: Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Brüll
authors.affiliation: Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Burak
authors.affiliation: Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Stoffel-Wagner
authors.affiliation: Institute of Animal Nutrition and Physiology, Christian-Albrechts-University Kiel, Kiel, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Wolffram
authors.affiliation: Department of Cardiology, Angiology and Pneumology, University Hospital Bonn, Bonn, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Nickenig
authors.affiliation: Department of Cardiology, Angiology and Pneumology, University Hospital Bonn, Bonn, Germany.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Müller
authors.affiliation: Institute of Pharmacy and Biochemistry, Department of Biopharmaceutics and Pharmaceutical Technology, Johannes Gutenberg University Mainz, Mainz, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Langguth
authors.affiliation: Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Alteheld
authors.affiliation: Institute of Medical Biometry, Informatics and Epidemiology, University Hospital Bonn, Bonn, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Fimmers
authors.affiliation: Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Stehle
authors.affiliation: Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany. s.egert@uni-bonn.de.
authors.forename: Sarah
authors.initials: S
authors.lastname: Egert
mesh_terms: D052242:Adiponectin / Q000097:blood*; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000150:complications; D019697:Onions / Q000737:chemistry; D050177:Overweight / Q000097:blood* / Q000150:complications; D010936:Plant Extracts / Q000008:administration & dosage; D058246:Prehypertension / Q000097:blood* / Q000150:complications; D011794:Quercetin / Q000008:administration & dosage*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
chemical_list: D052242:Adiponectin; D015415:Biomarkers; D001786:Blood Glucose; D002097:C-Reactive Protein; D002784:Cholesterol; D006442:Glycated Hemoglobin; D007328:Insulin; D020738:Leptin; D010936:Plant Extracts; D011794:Quercetin; D014409:Tumor Necrosis Factor-alpha
keywords: Adipocytokines; Human study; Metabolic syndrome; Quercetin