title: Isoflavonoids do not inhibit in vivo lipid peroxidation in subjects with high-normal blood pressure.
abstract: The isoflavonoids genistein and daidzein have been shown to have antioxidant activity in vitro, but their effects on in vivo oxidation have not been assessed. The newly described F2-isoprostanes are believed to currently represent the best available marker of in vivo lipid peroxidation. Therefore we have assessed the effects of a 55 mg daily isoflavonoid supplement on urinary F2-isoprostane concentrations in subjects with high-normal blood pressure (BP). A total of 59 subjects completed an 8-week parallel design, randomized, double blind, and placebo-controlled study. F2-isoprostanes, isoflavonoids and creatinine were measured in 24-h urine samples taken at baseline and at the end of the intervention. There were significant increases in urinary excretion of genistein (5.22+/-0.75 mg/day, P < 0.0001) and daidzein (2.53+/-0.43 mg/day, P < 0.0001) in the group taking the isoflavonoid supplement. Creatinine excretion was significantly correlated with F2-isoprostanes at baseline (r = 0.45, P < 0.01). After adjustment for baseline values, there was no significant difference between groups in creatinine adjusted post-intervention F2-isoprostane concentrations (P = 0.74). In addition, changes in genistein and daidzein excretion were not significantly correlated with changes in F2-isoprostanes in the isoflavonoid treatment group. These results are not consistent with the suggestion that the two soy derived isoflavonoids have in vivo antioxidant activity at a level of intake achievable by dietary means and in subjects with high-normal BP.
authors.affiliation: University of Western Australia Department of Medicine and the Western Australian Heart Research Institute, Royal Perth Hospital, Australia. jonathan@cyllene.uwa.edu.au
authors.forename: J M
authors.initials: JM
authors.lastname: Hodgson
authors.forename: I B
authors.initials: IB
authors.lastname: Puddey
authors.forename: K D
authors.initials: KD
authors.lastname: Croft
authors.forename: T A
authors.initials: TA
authors.lastname: Mori
authors.forename: J
authors.initials: J
authors.lastname: Rivera
authors.forename: L J
authors.initials: LJ
authors.lastname: Beilin
mesh_terms: D000328:Adult; D000368:Aged; D000975:Antioxidants / Q000493:pharmacokinetics / Q000494:pharmacology*; D001794:Blood Pressure; D003404:Creatinine / Q000652:urine; D015237:Dinoprost / Q000652:urine; D004311:Double-Blind Method; D005260:Female; D019833:Genistein / Q000494:pharmacology* / Q000652:urine; D006801:Humans; D006973:Hypertension / Q000378:metabolism*; D007529:Isoflavones / Q000494:pharmacology* / Q000652:urine; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D008875:Middle Aged
chemical_list: D000975:Antioxidants; D007529:Isoflavones; C004742:daidzein; D003404:Creatinine; D015237:Dinoprost; D019833:Genistein