title: Dietary lignins are precursors of mammalian lignans in rats.
abstract: The mammalian lignans enterolactone (ENL) and enterodiol, commonly found in human plasma and urine, are phytoestrogens that may contribute to the prevention of breast cancer and coronary heart disease. They are formed by the conversion of dietary precursors such as secoisolariciresinol and matairesinol lignans by the colonic microflora. The identification of lignins, cell-wall polymers structurally related to lignans, as precursors of mammalian lignans is reported here for the first time. In study 1, rats were fed rye or wheat bran (15% diet) for 5 d. Untreated brans and brans extracted with solvents to remove lignans were compared. ENL was estimated in urine samples collected for 24 h by time-resolved fluoroimmunoassay. ENL urinary excretion was reduced from 18.6 to 5.3 nmol/d (n=8; P<0.001) when lignans were removed from rye bran and from 30.5 to 6.2 nmol/d (P<0.001) when they were removed from wheat bran. These results suggest that lignins, embedded in the cell wall and retained in the bran during solvent extraction, account for 26-32% of the ENL formed from cereal brans. In study 2, rats were fed a deuterated synthetic lignin (0.2% diet) together with wheat bran (15%) for 3 d. The detection of deuterated ENL by LC-tandem MS in urine (20 nmol/d) clearly confirms the conversion of lignin into mammalian lignans. More research is warranted to determine the bioavailability of lignins in the human diet.
authors.affiliation: Unite des Maladies Metaboliques et Micronutrients, INRA Theix, 63122 Saint-Genes-Champanelle, France.
authors.forename: Aynun Nahar
authors.initials: AN
authors.lastname: Begum
authors.forename: Catherine
authors.initials: C
authors.lastname: Nicolle
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mila
authors.forename: Catherine
authors.initials: C
authors.lastname: Lapierre
authors.forename: Kazutane
authors.initials: K
authors.lastname: Nagano
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Fukushima
authors.forename: Satu-Maarit
authors.initials: SM
authors.lastname: Heinonen
authors.forename: Herman
authors.initials: H
authors.lastname: Adlercreutz
authors.forename: Christian
authors.initials: C
authors.lastname: Rémésy
authors.forename: Augustin
authors.initials: A
authors.lastname: Scalbert
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000652:urine; D000818:Animals; D001682:Biological Availability; D002473:Cell Wall / Q000378:metabolism; D044602:Cellulases / Q000378:metabolism; D002853:Chromatography, Liquid; D003903:Deuterium; D004032:Diet; D008401:Gas Chromatography-Mass Spectrometry; D006026:Glycoside Hydrolases / Q000378:metabolism; D007529:Isoflavones / Q000096:biosynthesis; D017705:Lignans / Q000032:analysis / Q000096:biosynthesis* / Q000652:urine; D008031:Lignin / Q000008:administration & dosage* / Q000378:metabolism*; D008297:Male; D048789:Phytoestrogens; D028321:Plant Preparations; D051381:Rats; D017208:Rats, Wistar; D012434:Secale / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D014908:Triticum / Q000737:chemistry
chemical_list: D007529:Isoflavones; D017705:Lignans; D048789:Phytoestrogens; D028321:Plant Preparations; C029498:2,3-bis(3'-hydroxybenzyl)butane-1,4-diol; D008031:Lignin; D003903:Deuterium; D044602:Cellulases; D006026:Glycoside Hydrolases; C023305:hemicellulase; D015107:4-Butyrolactone; C029497:2,3-bis(3'-hydroxybenzyl)butyrolactone