Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 21, 2018; 24(3): 338-350
Published online Jan 21, 2018. doi: 10.3748/wjg.v24.i3.338
Effect of Lactobacillus rhamnosus GG supernatant on serotonin transporter expression in rats with post-infectious irritable bowel syndrome
Ya-Nan Cao, Li-Juan Feng, Yuan-Yuan Liu, Kui Jiang, Mao-Jun Zhang, Yi-Xin Gu, Bang-Mao Wang, Jia Gao, Ze-Lan Wang, Yu-Ming Wang
Ya-Nan Cao, Yuan-Yuan Liu, Kui Jiang, Bang-Mao Wang, Jia Gao, Ze-Lan Wang, Yu-Ming Wang, Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
Li-Juan Feng, Department of Functional Division, Xingtai People’s Hospital, Xingtai 054031, Hebei Province, China
Mao-Jun Zhang, Yi-Xin Gu, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China
Author contributions: Cao YN and Feng LJ contributed to essential research and statistical analysis; Wang YM, Jiang K, and Wang BM designed the study; Zhang MJ, Gu YX and Liu YY were mainly responsible for cultivation of bacteria, Gao J, Liu YY and Wang ZL contributed to raising animals; Cao YN and Feng LJ edited the article; Wang YM supported the financial arrangement.
Supported by the National Natural Science Foundation of China, No. 81570489.
Institutional review board statement: This study was approved by the Tianjin Medical University General Hospital.
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Animal Ethics and Welfare Committee of Tianjin Medical University.
Conflict-of-interest statement: The authors declare that they have no competing interests.
Data sharing statement: Readers can get the data of this paper by contacting us via E-mail:
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Yu-Ming Wang, MD, PhD, Attending Physician, Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, No. 154, Anshan Road, Heping District, Tianjin 300052, China.
Telephone: +86-22-60362608 Fax: +86-22-60363768
Received: November 9, 2017
Peer-review started: November 9, 2017
First decision: November 30, 2017
Revised: December 6, 2017
Accepted: December 12, 2017
Article in press: December 12, 2017
Published online: January 21, 2018
Research background

Probiotics have been approved to be used to relieve irritable bowel syndrome (IBS), and Lactobacillus rhamnosus GG (LGG) is the best studied member of lactic acid bacteria and has supportive therapeutic efficacy in IBS. However, the mechanism remains a significant challenge to researchers. This study developed a PI-IBS model to evaluate the effect of LGG supernatant on serotonin transporter expression.

Research motivation

This study is a part of a National Natural Science Foundation of China project. On the basis of developing an experimental model of PI-IBS, this research explored the effect of LGG-s on SERT levels in intestinal and brain tissues.

Research objectives

This study detected the expression levels of SERT mRNA and SERT-P to evaluate the effect of LGG-s in PI-IBS rats, which were infected with C. jejuni. LGG-s could up-regulate SERT mRNA and SERT-P levels in rat intestinal tissues but had no influence in rat brain tissues. The more detailed research on LGG-s will contribute to more accurate treatment of IBS.

Research methods

The model group of PI-IBS (n = 85) was given C. jejuni (1010 CFU/mL, 2 mL/d per rat) for 7 d, then the body weight of the rats and the relative content of stool water were measured to evaluate the phase of infection, and the fresh stool specimens were cultured for the presence of C. jejuni on Campylobacter selective agar plates. After the model evaluation, the rats were regrouped, and each group was gavaged with different concentrations of LGG-s. The treatments were maintained for 1.0, 2.0, 3.0 or 4.0 wk during the experiment. Then, SERT expression was detected by RT-PCR and Western blot to evaluate the effect of LGG-s.

Research results

The levels of SERT mRNA and SERT-P in intestinal tissues were up-regulated by treatment with LGG-s of different concentrations. Triple-diluted LGG-s showed a more significant difference within a short term, while, in the long run, undiluted and double-diluted LGG-s proved better. However, there were no significant differences in SERT mRNA and SERT-P in the brain tissues between each group, with or without treatment with LGG-s. Some factors and differences in the contents of various substances (proteins, fatty acids, inorganic salts, etc.) in the supernatant may induce a different increase in SERT levels. More detailed research about LGG-s is needed.

Research conclusions

This study demonstrates that LGG-s up-regulates SERT expression in intestinal tissues, but has no statistical effect in brain tissues in PI-IBS rats. The previous study has proved that LGG-s could up-regulate the SERT levels in intestinal tissues in healthy mice. Moreover, LGG-s led to dose-dependent expression of SERT. The contents of substances in the supernatant, combined with their different concentrations, molecular mass, and previous C. jejuni infection, may result in this phenomenon. Therefore, more detailed research about LGG-s and relief of clinical symptoms with the treatment of LGG-s would be done in our next work.

Research perspectives

The infection with C. jejuni could help to build a PI-IBS model with lower expression of SERT. For the future accurate treatment of IBS, proteomics analysis of LGG-s is important and urgent.