Gut fermentation products of inulin-type fructans modulate the expression of xenobiotic-metabolising enzymes in human colonic tumour cells.

Epidemiological studies suggest that nutrition plays an important role in colonic cancer prevention. A possible mechanism of this prevention may be the modulation of carcinogen metabolism and scavenging of reactive intermediates. In particular, dietary fibres are discussed as potentially protective food ingredients. Therefore, the aim of this study was to analyse if the expression of genes related to biotransformation is modulated by fermentation samples of dietary fibres. HT29 (human colonic carcinoma) and LT97 (human adenoma) cells were incubated with fermentation supernatant (SFS), produced by in vitro fermentation of inulin enriched with oligofructose. Possible mechanisms of de-toxification were investigated by analysing the expression of catalase and glutathione-S-transferase (GST) A4 mRNA and the enzyme activity of catalase and GST. In addition, protection of both cell lines against DNA damage, induced by H(2)O(2) or 4-hydroxynonenal (HNE), was analysed using the comet assay. Incubation with SFS resulted in significantly increased GSTA4 mRNA expression, significantly enhanced catalase activity and a significant reduction in the amount of H(2)O(2)-induced DNA damage in HT29 cells. Our results show that complex fermentation samples of inulin-type fructans favourably modulate expression of genes related to biotransformation in carcinoma cells, which in turn supports the important role of dietary fibres in primary chemoprevention.