title: Effects of genistein and equol on human and rat testicular 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase 3 activities.
abstract: The objective of the present study was to investigate the effects of genistein and equol on 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase 3 (17beta-HSD3) in human and rat testis microsomes. These enzymes (3beta-HSD and 17beta-HSD3), along with two others (cytochrome P450 side-chain cleavage enzyme and cytochrome P450 17alpha-hydroxylase/17-20 lyase), catalyze the reactions that convert the steroid cholesterol into the sex hormone testosterone. Genistein inhibited 3beta-HSD activity (0.2 micromol L(-1) pregnenolone) with half-maximal inhibition or a half-maximal inhibitory concentration (IC(50)) of 87 +/- 15 (human) and 636 +/- 155 nmol L(-1) (rat). Genistein's mode of action on 3beta-HSD activity was competitive for the substrate pregnenolonrge and noncompetitive for the cofactor NAD(+). There was no difference in genistein's potency of 3beta-HSD inhibition between intact rat Leydig cells and testis microsomes. In contrast to its potent inhibition of 3beta-HSD, genistein had lesser effects on human and rat 17beta-HSD3 (0.1 micromol L(-1) androstenedione), with an IC(50) >or= 100 micromol L(-1). On the other hand, equol only inhibited human 3beta-HSD by 42%, and had no effect on 3beta-HSD and 17beta-HSD3 in rat tissues. These observations imply that the ability of soy isoflavones to regulate androgen biosynthesis in Leydig cells is due in part to action on Leydig cell 3beta-HSD activity. Given the increasing intake of soy-based food products and their potential effect on blood androgen levels, these findings are greatly relevant to public health.
authors.affiliation: Population Council, New York, NY 10065, USA.
authors.forename: Guo-Xin
authors.initials: GX
authors.lastname: Hu
authors.forename: Bing-Hai
authors.initials: BH
authors.lastname: Zhao
authors.forename: Yan-Hui
authors.initials: YH
authors.lastname: Chu
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Zhou
authors.forename: Benson T
authors.initials: BT
authors.lastname: Akingbemi
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Zheng
authors.forename: Ren-Shan
authors.initials: RS
authors.lastname: Ge
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000187:drug effects / Q000378:metabolism*; D015096:3-Hydroxysteroid Dehydrogenases / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D060754:Equol; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D007700:Kinetics; D007985:Leydig Cells / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013737:Testis / Q000187:drug effects* / Q000201:enzymology
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D007529:Isoflavones; D060754:Equol; D019833:Genistein; D015067:17-Hydroxysteroid Dehydrogenases; D015096:3-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase
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