Abstract
The intestinal flora may act on cholesterol metabolism either, directly by converting the molecule to coprostanol, or indirectly, by influencing upon intestinal bile acid metabolism, mainly by deconjugation. In the present study, sixteen probiotic strains belonging to the genera: Bifidobacterium, Enterococcus, Lactobacillus and Streptococcus were investigated for possible direct action on cholesterol metabolism in vitro and in vivo in ex-germfree mice monoassociated with each probiotic. Additionally, deconjugation of taurodeoxycholic acid (TDC) and of glycodeoxycholic acid (GDC) was investigated in vitro as an indirect effect upon cholesterol metabolism, using the same strains. Gas-liquid chromatography and thin-layer chromatography were used. None of the probiotic strains, was able to transform cholesterol to coprostanol in vitro or in vivo. Of the total probiotics analyzed, B. bifidum B12, L. acidophilus La5, L. acidophilus ATCC4356, L. fermentum ATCC14931, L. plantarum 299v, L. rhamnosus ATCC7469 and E. faecium were able to deconjugate both TDC and GDC in vitro. We conclude that the formation of coprostanol does not account for the supposed cholesterol-lowering effect of the probiotics tested. As some of the probiotics were able to deconjugate TDC and/or GDC in vitro, this microbial function should be studied more extensively in vivo.