Published online Sep 28, 2017. doi: 10.3748/wjg.v23.i36.6665
Peer-review started: June 12, 2017
First decision: July 27, 2017
Revised: August 27, 2017
Accepted: September 5, 2017
Article in press: September 5, 2017
Published online: September 28, 2017
To investigate the intestinal luminal microbiota (LM) and mucosa-associated microbiota (MAM) in Chinese patients with functional gastrointestinal disorders (FGIDs) and examine the association between these communities and the expression of toll-like receptor (TLR) 2 and TLR4.
Thirty-two Chinese subjects who suffered from symptoms of FGIDs, as confirmed by gastroenterologists, were enrolled in this study. Fresh faecal samples and descending colonic mucosal biopsies were collected from the subjects before (faecal) and during (mucosal) flexible colonoscopy. For analysis of the samples, we performed high-throughput sequencing of the V3-V4 region of the 16S rRNA gene and reverse transcription (RT)-PCR to detect the expression of colonic TLR2 and TLR4. Differences in the stool and mucosal microbiota were examined and a correlation network analysis was performed.
The microbiota of faecal samples was significantly more diverse and richer than that of the mucosal samples, and the LM and MAM populations differed significantly. TLR2 expression showed a significant positive correlation with TLR4 expression. In the MAM samples, the genera Faecalibacterium and Ruminococcus, which belong to the family Ruminococcaceae, were inversely correlated with TLR4 expression (r = -0.45817, P = 0.0083 and r = -0.5306, P = 0.0018, respectively). Granulicatella, which belongs to Carnobacteriaceae, and Streptococcus, which belongs to Streptococcaceae, were inversely correlated with TLR2 expression (r = -0.5573, P = 0.0010 and r = -0.5435, P = 0.0013, respectively). In the LM samples, examination at phylum, class, or order level revealed no correlation with TLR4 expression. Faecalibacterium, which belongs to Ruminococcaceae, and Streptococcus, which belongs to Streptococcaceae, were inversely correlated with TLR2 expression (r = -0.5743, P = 0.0058 and r = -0.3905, P = 0.0271, respectively).
Microbial compositions of LM and MAM in Chinese patients with FGIDs are different. Expression of TLRs may be affected by the type of bacteria that are present in the gut.
Core tip: To explore which bacteria regulate the expression of toll-like receptors (TLRs) and thereby affect intestinal functions, we performed high-throughput pyrosequencing of the bacterial 16S rRNA gene, compared the microbial communities in the faeces and mucosa of Chinese patients with functional gastrointestinal disorders, and studied their association with the expression of colonic mucosal TLR2 and TLR4. Samples of luminal microbiota were different from those of mucosa-associated microbiota (MAM), and MAM samples were closely associated with TLR2/4 expression. The abundance of Faecallibacterium and Ruminococcus was lower in patients with gut disease, while the expression of TLRs is higher than in healthy controls. The presence of Faecallibacterium and Ruminococcus was significantly and negatively correlated with TLR4 expression, suggesting that these two bacteria, which colonize on the colonic mucosa, play a key role in gut diseases by regulating mucosal TLR4 expression. Granulicatella, which belongs to Carnobacteriaceae, and Streptococcus, which belongs to Streptococcaceae, were inversely correlated with TLR2 expression. Because the two genera contained not only pathogenic species but also probiotic species, it will be important to establish a better understanding of the relationship between TLRs and bacterial strains in future studies.