Folate deficiency enhances the <i>in vitro</i> genotoxicity of bile acids in human colon and liver cells

Obese subjects have a high baseline of genotoxic stress, but the underlying mechanism is poorly understood. Given that obesity is associated with high bile acids (BA) and low folate, we aimed to determine the interactive effect of folate deficient or supplementation to the genotoxicity and cytotoxicity of BA in human colon and liver cells. NCM460 and L-02 cells were cultured in folate-deficient (22.6 nM) and replete (2260 nM) Roswell Park Memorial Institute (RPMI)-1640 medium with or without 50 μM deoxycholic acid (DCA) or lithocholic acid (LCA) for 7 days. Moreover, these cells were cultured in folate supplemented (5.65, 11.3 and 22.6 μM) and standard (2.26 μM) medium with 200 μM DCA or LCA for 7 days. Genotoxicity and cytotoxicity were measured using the cytokinesis-block micronucleus cytome assay. Our results showed that under folate-replete condition, 50 μM DCA or LCA significantly increased the rate of micronuclei (MN) in NCM460 and L-02 cells. Significantly, the MN-inducing effect of 50 μM DCA or LCA was further enhanced by folate deficiency. Interestingly, folate supplementation exerted a dose-dependent manner to significantly decrease the rates of MN, nucleoplasmic bridges, nuclear buds, apoptosis, and necrosis induced by 200 μM DCA or LCA in NCM460 and L-02 cells. In conclusion, the genotoxicity of moderate BA (50 μM) was exacerbated by folate deficiency and folate supplementation could efficiently protect cells against the genotoxicity and cytotoxicity of high BA (200 μM).