Volume 89, Issue 6, June (2003), pp. 755-765 © The Author 2003
doi:10.1079/BJN2003848

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The effect of oestrogen and dietary phyto-oestrogens on transepithelial calcium transport in human intestinal-like Caco-2 cells

Alice A. Cotter¹, Christopher Jewell¹ and Kevin D. Cashman^1,2,*
1Department of Food and Nutritional Sciences and
²Department of Medicine, University College, Cork, Ireland

 (Received 28 January 2002–Revised 16 December 2002–Accepted 16 January 2003)

Recently, dietary phyto-oestrogens (PO) have been suggested as possible alternatives to oestrogen therapy (hormone replacement therapy) as a means of preventing bone loss associated with ovarian hormone deficiency. While PO, which exhibit oestrogen-like activity, act directly on bone cells, their protective effect on bone may be partly due to their ability to enhance Ca absorption. Therefore, the aim of the present study was to investigate the effect of 17b-oestradiol and two commonly consumed soyabean PO (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 8–18 per treatment), grown in oestrogen-replete or -deplete media, were then exposed to 10 nM-17b-oestradiol, 1 nM-1,25-dihydroxycholecalciferol, or 50mM-genistein or -daidzein for 24h. After exposure, transepithelial and transcellular transport of ⁴⁵Ca and fluorescein transport (a marker of paracellular diffusion) were measured. As expected, 1,25-dihydroxycholecalciferol stimulated Ca absorption in Caco-2 cells, by up-regulating transcellular transport, whereas 17b-oestradiol had no effect on Ca absorption. Unexpectedly, both PO decreased Ca absorption (by about 17–19% compared with control, P<0·05), by reducing transcellular Ca transport in Caco-2 cells grown in oestrogen-replete media. This inhibitory effect disappeared when monolayers were grown in oestrogen-deplete media. In conclusion, PO at high luminal concentrations either had no effect or reduced Ca absorption in Caco-2 cells, dependent on oestrogen status. The effect of lower concentrations of these compounds needs to be investigated.

Abbreviations: FBS; fetal bovine serum; LDH; lactate dehydrogenase; MTT; 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide; Neutral Red; 3-amino-7-dimethylamino-2-methylphenazine hydrochloride; OR; oestrogen receptor; PO; phyto-oestrogen; TEER; transepithelial electrical resistance; 1,25(OH)₂D₃; 1,25-dihydroxycholecalciferol

Keywords:
Oestrogen, Phyto-oestrogens, Calcium absorption, Caco-2 cells