Volume 91, Issue 1, January (2004), pp. 5-9 © The Author 2004
doi:10.1079/BJN20031007

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Short communication

Lack of dose-responsive effect of dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

Alice A. Cotter¹, Kevin D. Cashman^1,2
1Department of Food and Nutritional Sciences and
²Department of Medicine, University College, Cork, Republic of Ireland

 (Received 1 July 2003–Revised 20 August 2003–Accepted 23 August 2003)

Ca absorption has been shown to be unaffected by high luminal concentrations of two commonly consumed soyabean phyto-oestrogens (PO) (genistein and daidzein) in Caco-2 cells grown under oestrogen-depleted conditions. However, these compounds exhibit dose-dependent biphasic effects in some tissues, such as reproductive tissue and bone. Thus, in light of this biphasic activity, the effect of lower concentrations of genistein and daidzein on Ca absorption requires further investigation. Therefore, the aim of the present study was to investigate the effect of a range of concentrations of genistein and daidzein on Ca absorption in the human Caco-2 intestinal-like cell model. Caco-2 cells were seeded onto permeable filter supports and allowed to differentiate into monolayers. On day 21, the Caco-2 monolayers (n 12 per treatment), grown in oestrogen-deplete media, were then exposed to 10 nm-1,25-dihydroxycholecalciferol (1,25 (OH)₂D₃), or 1, 10 and 50 μm-genistein or -daidzein for 24 h. After exposure, transepithelial and transcellular transport of ⁴⁵Ca and fluorescein transport were measured. As expected, 1,25 (OH)₂D₃ stimulated Ca absorption in Caco-2 cells, by up regulating transcellular transport. Ca absorption was unaffected by either PO at luminal concentrations of 1, 10 or 50 μm, typical of intakes by Western and Asian populations as well as supplemental levels, respectively. The results of this model suggest that the proposed beneficial effects of supplemental levels of these PO compounds on bone mass in postmenopausal women more probably arise from direct effects on bone cells, and not by an indirect effect of these compounds on Ca absorption.

Keywords:
Phyto-oestrogens, Dose-response, Calcium absorption, Caco-2 cells

Abbreviations:
>MTT, 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide, Neutral Red, 3-amino-7-dimethylamino-2-methylphenazine hydrochloride, 1,25 (OH)₂D₃, 1,25-dihydroxycholecalciferol, OR, oestrogen receptor, PO, phyto-oestrogen