a1 Department of Nutritional Toxicology, Institute for Nutrition, Friedrich-Schiller-University Jena, Dornburger Strasse 24, 07743 Jena, Germany
Epidemiological evidence suggests that the intake of prebiotic dietary fibres, for example, inulin, protects against colorectal cancer. However, little is known about cellular responses to complex fermentation samples. Therefore, we prepared a fermentation supernatant fraction of inulin and studied biological properties in human colon cell lines, LT97 and HT29 (representing early and late stages of colon cancer). Inulin enriched with oligofructose (Synergy 1) was incubated under anaerobic conditions with faecal inocula and the supernatant fraction was characterised for content of SCFA and secondary bile acid deoxycholic acid (DCA). A Synergy fermentation supernatant fraction (SFS) and a synthetic fermentation mixture (SFM) mimicking the SFS in SCFA and DCA content were used in the concentration range of 1·25–20 % (v/v) for 24–72 h. The effects on cell growth were determined by quantifying DNA. Effects on apoptosis were analysed by measuring poly(ADP-ribose) polymerase (PARP) cleavage using Western blotting. Compared with the faecal blank, produced without the addition of inulin, the SFS resulted in an almost 2·5-fold increase of SCFA and 3·4-fold decrease of DCA. In comparison with HT29 cells, LT97 cells responded more sensitively to the growth-inhibitory activities. Additionally, a significant increase in PARP cleavage was observed in LT97 cells after incubation with the SFS, demonstrating induction of apoptosis. The present results indicate growth-inhibiting and apoptosis-inducing effects of fermentation supernatant fractions of inulin. Moreover, since early adenoma cells were found to be more sensitive, this may have important implications for chemoprevention when translated to the in vivo situation, because survival of early transformed cells could be reduced.
(Received August 20 2008)
(Revised December 09 2008)
(Accepted January 09 2009)
(Online publication February 27 2009)
Abbreviations: ACF, aberrant crypt foci; DCA, deoxycholic acid; FB, faecal blank; PARP, poly(ADP-ribose) polymerase; SFM, synthetic fermentation mixture; SFS, Synergy fermentation supernatant fraction