Synbiotic mediated metabolism of bile salts implications for serum cholesterol levels

 

School of Health and Bioscience, University of East London, Romford Road, Stratford, London, E15 4LZ. ⁺Dr. Ronald R. Cutler, School of Biological and Chemical Sciences Queen Mary, University of London, 327 Mile End Road, London, E1 4NS, United Kingdom

*Corresponding author: E-mail o.o.adebola@uel.ac.uk

 

Introduction: One of the putative benefits of synbiotic application of probiotics and prebiotics is the management of serum cholesterol levels. Probiotics are live microbial supplements and in use are various species of lactobacilli and bifidobacteria. Bile salt hydrolase enzymes (BSH) secreted by a range of probiotic cultures catalyse the deconjugation of bile salts; the resulting free bile acids are less likely to enter enterohepatic circulation thus affecting the balance and consequently serum cholesterol levels. The present study examines the impact of some widely used synbiotic combinations on bile salt metabolism.

 

Methods: Following growth of Lactobacillus acidophilus NCTC 1723in De man Rogosa medium supplemented with bile salts (taurocholic acid) and prebiotics (inulin, lactulose or lactobionic acid) the release of free bile acid was qualitatively assessed using thin layer chromatography (TLC) and quantitatively using a colorimetric assay as described by Walker and Gilliland 1993.

 

Results: L. acidophilus NCTC 1723 a widely used probiotic deconjugated sodium salts of taurocholic acid. The rate of free cholic acid released in the absence of a prebiotic was 2.5 x 10^-2nmol/min. Inulin at 1% and 2% significantly increased BSH activity with 3.2 x 10^-2 nmol/min and 2.83 x 10^-2 nmol/min cholic acid released respectively. By contrast both lactulose and lactobionic acid resulted in a decrease in BSH deconjugation activity with 1.02 x 10^-2 nmol and 0.66 x 10^-2 nmol/min cholic acid released respectively following growth in 0.5% lactobionic acid and 2% lactulose the greatest inhibition caused by 1% lactobionic acid was probably due to low pH (Figure 1).

 

Conclusion: These results suggest that probiotic deconjugation of bile salts may be compromised by the presence of certain prebiotics. If reproduced in vivo these observations suggest that only a few of the widely used synbiotic combinations may have beneficial impact on the serum cholesterol through the alteration of bile salt metabolism.

 

Acknowledgements

The authors thank University of East London for providing the funds necessary for this research.

 

Reference

Reynier, M.O., Montet, J.C., Gerolami, A., Marteau, C., Crotte, C., Montet, A.M., Mathieu, S., 1981. Journal of Lipid Research. 22, pp 467-473.

Walker, D. K., Gilliland, S.E., 1993. J Dairy Sci. 76, 956-961.