Gut Microbial Metabolites and Biochemical Pathways Involved in Irritable Bowel Syndrome: Effects of Diet and Nutrition on the Microbiome

The food we consume and its interactions with the host and their gut microbiota affect normal gut function and health. Functional gut disorders (FGDs), including irritable bowel syndrome (IBS), can result from negative effects of these interactions, leading to a reduced quality of life. Certain foods exacerbate or reduce the severity and prevalence of FGD symptoms. IBS can be used as a model of perturbation from normal gut function with which to study the impact of foods and diets on the severity and symptoms of FGDs and understand how critical processes and biochemical mechanisms contribute to this impact. Analyzing the complex interactions between food, host, and microbial metabolites gives insights into the pathways and processes occurring in the gut which contribute to FGDs. The following review is a critical discussion of the literature regarding metabolic pathways and dietary interventions relevant to FGDs. Many metabolites, for example bile acids, SCFAs, vitamins, amino acids, and neurotransmitters, can be altered by dietary intake, and could be valuable for identifying perturbations in metabolic pathways that distinguish a "normal, healthy" gut from a "dysfunctional, unhealthy" gut. Dietary interventions for reducing symptoms of FGDs are becoming more prevalent, but studies investigating the underlying mechanisms linked to host, microbiome, and metabolite interactions are less common. Therefore, we aim to evaluate the recent literature to assist with further progression of research in this field.

Morning versus afternoon adenoma detection rate: a systematic review and meta-analysis

Adenoma detection rate (ADR) is a quality marker of colonoscopy and operator performance. Prior studies evaluating the effect of an extended workday on the ADR reported variable outcomes that remain controversial. Given the variable results of prior studies and the potential legal implications of reduced ADR in the afternoon, we aimed to further evaluate this parameter and its effect on ADR. We performed a systematic review of the PubMed, CINAHL and Scopus electronic databases. Studies were included if they reported ADR in patients undergoing colonoscopy in the morning session and the afternoon session. Afternoon sessions included both sessions following a morning shift and half-day block shifts. Subgroup analyses were performed for ADR comparing morning and afternoon colonoscopies in a continuous workday, advanced ADRs (AADRs) and polyp detection rates (PDRs) were also compared. Thirteen articles with 17 341 (61.2%) performed in the morning session and 10 994 (38.8%) performed in the afternoon session were included in this study. There was no statistical significance in the ADR or AADR between morning and afternoon sessions, respectively [relative risk (RR) 1.06, 95% confidence interval (CI) 0.99-1.14] and (RR 1.19, 95% CI 0.95-1.5). Afternoon procedures had a significantly higher PDR than morning procedures (RR 0.93, 95% CI 0.88-0.98). ADR was not significantly influenced in the afternoon session when operators continued to perform procedures throughout the day or on a half-day block schedule.

The Relationship Between the Serotonin Metabolism, Gut-Microbiota and the Gut-Brain Axis

BACKGROUND

Serotonin (5-HT) has a pleiotropic function in gastrointestinal, neurological/psychiatric and liver diseases. The aim of this review was to elucidate whether the gut-microbiota played a critical role in regulating peripheral serotonin levels.

METHODS

We searched for relevant studies published in English using the PubMed database from 1993 to the present.

RESULTS

Several studies suggested that alterations in the gut-microbiota may contribute to a modulation of serotonin signalling. The first indication regarded the changes in the composition of the commensal bacteria and the intestinal transit time caused by antibiotic treatment. The second indication regarded the changes in serotonin levels correlated to specific bacteria. The third indication regarded the fact that decreased serotonin transporter expression was associated with a shift in gut-microbiota from homeostasis to inflammatory type microbiota. Serotonin plays a key role in the regulation of visceral pain, secretion, and initiation of the peristaltic reflex; however, its altered levels are also detected in many different psychiatric disorders. Symptoms of some gastrointestinal functional disorders may be due to deregulation in central nervous system activity, dysregulation at the peripheral level (intestine), or a combination of both (brain-gut axis) by means of neuro-endocrine-immune stimuli. Moreover, several studies have demonstrated the profibrogenic role of 5-HT in the liver, showing that it works synergistically with platelet-derived growth factor in stimulating hepatic stellate cell proliferation.

CONCLUSION

Although the specific interaction mechanisms are still unclear, some studies have suggested that there is a correlation between the gut-microbiota, some gastrointestinal and liver diseases and the serotonin metabolism.

Impact of adenoma detection rate on detection of advanced adenomas and endoscopic adverse events in a study of over 200,000 screening colonoscopies

BACKGROUND AND AIMS

Adenoma detection rate (ADR) is the best established quality parameter for screening colonoscopy. Guidelines recommend a target ADR >25% because previous studies have shown that patients of endoscopists with higher ADRs have a lower risk of postcolonoscopy interval cancers. However, studies have shown that improvement in ADR mainly results in increased detection of clinically irrelevant nonadvanced adenomas (NAAs). The impact of ADR on the detection of advanced adenomas (AAs) as well as adverse event rates has yet to be determined.

METHODS

A total of 218,193 screening colonoscopies performed between 2007 and 2010 by 262 endoscopists within the Austrian quality assurance program were analyzed. We divided endoscopists into quintiles based on ADRs and calculated mean advanced ADRs (AADRs), NAA detection rates (NAADRs), and adverse event rates for each quintile. Spearman rank-order was used to calculate overall correlations between ADRs and AADRs as well as adverse event rates. Endoscopists with an ADR <25% were compared with those with an ADR >25%.

RESULTS

Fifty-one percent of patients were women. Mean ADR was 23.03% (95% confidence interval [CI], 21.93-24.13), AADRs 7.72% (95% CI, 7.19-8.25), and NAADRs 15.31% (95% CI, 14.36-16.27). Overall, there was a significant correlation between ADR and AADR (rho = .51; P < .001). When ADR was divided into quintiles, mean AADR increased with increasing ADR. Even in the highest ADR group (ADR, 31.36%-52.27%) there was a further increase in AADR with a mean of 10.75% (95% CI, 9.31-12.19). Importantly, NAADRs increased continuously with improvement in ADRs but never dissociated from a simultaneous improvement in AADRs. However, there was also a significant correlation of ADRs and endoscopic adverse events (rho = .26, P < .001), even if the perforation rate of .028% (95% CI, .004-.052) in the highest ADR group still remained within the accepted limits based on guidelines.

CONCLUSIONS

Increasing ADR is associated with improved detection of AAs and therefore is likely to prevent more cases of colorectal cancer. However, higher ADR was also associated with a higher rate of adverse events, although the adverse event rate was low.

Colonoscopic withdrawal time and adenoma detection in the right colon

Shorter colonoscopic withdrawal time (CWT) has been associated with lower adenoma detection rate (ADR), which can increase the risk of interval colorectal cancer (ICC) that commonly arises in the right colon (RC). Therefore, a better ADR in the RC could decrease the incidence of ICC. We analyzed the relationship between CWT and ADR in the RC and entire colon.We retrospectively reviewed the patients who had undergone screening colonoscopy at Chungnam National University Hospital between March 2015 and February 2016. We enrolled 5370 patients in whom colonoscopies were performed by 7 gastroenterologists. We categorized patients into 4 groups in the RC and 6 groups in the entire colon by CWT. Multivariable analysis was used for detection of adenoma in the RC and entire colon.In the RC, the odds ratio (OR) of CWT longer than 3 minutes was 3.70, compared to CWT of <2 minutes [3.06-4.85, 95% confidence interval (CI), P < .001]. In the entire colon, the OR of CWT between 9 to 10 minutes and longer than 10 minutes was 3.34 [2.61-4.27, 95% CI, P < .001] and 3.49 [2.80-4.33, 95% CI, P < .001] compared to CWT of <6 minutes.Based on our result, we suggest that the optimum CWT in the RC should exceed 3 minutes, and considering the "ceiling effect," the optimum CWT in the entire colon should exceed 9 minutes.

Correlation between adenoma detection rate and novel quality indicators for screening colonoscopy. A proposal for quality measures tool kit

BACKGROUND AND AIMS

Adenoma detection rate (ADR) is the most validated quality indicator for colonoscopy. Calculating ADR may not yield information in regards to advanced adenoma detection rate (advanced ADR). In addition, calculating ADR for individual endoscopists cannot distinguish between those who find only one versus more than one adenoma per colonoscopy. Several novel quality indictors were recently proposed to ensure adequate assessment of quality during colonoscopy. Our study aims to determine the correlation between ADR and novel quality indicators.

METHODS

A retrospective cohort study of patients undergoing screening colonoscopy in a university hospital setting. Patient characteristics and colonoscopy findings were combined and analyzed to calculate the correlation of ADR with novel quality indicators using Spearman's rank-order correlation were used.

RESULTS

A total of 1433 patients out of 2116 patients met the inclusion criteria. There was a significant positive correlation between ADR correlated with [advanced-ADR-2, nonadvanced-ADR, adenoma per colonoscopy, Multiplicity detection rate and ADR-Plus] r = (0.82, 0.99, 0.99, 0.07 and 0.85), respectively. However, ADR did not correlate with advanced-ADR and adenomas per positive participant.

CONCLUSION

Adding advanced-ADR and adenomas per positive participant to ADR may create a more comprehensive quality indicators tool kit, which is sensitive and difficult to game. Future studies are needed to investigate the impact of the tool kit on the interval cancers and adenoma missing rate.

Cap-Assisted Colonoscopy Increases Detection of Advanced Adenomas and Polyps

BACKGROUND

Cap-assisted colonoscopy (CAC) has been reported to increase the adenoma detection rate (ADR) in Asian population. However, CAC trials in non-Asian population have had conflicting results. Studies in North America have shown an improvement in ADRs with the use of CAC, but it mainly included white and African American patients. Given the lack of prospective studies of CAC in Hispanics, we conducted this randomized controlled trial.

MATERIALS AND METHODS

This is a randomized controlled trial comparing CAC with standard colonoscopy (SC) in patients undergoing screening or surveillance colonoscopy. Our primary outcome was the ADR. Secondary outcomes were polyp detection rate, mean polyp and ADR, advanced ADR (AADR) and detection rates based on polyp morphology and location.

RESULTS

A total of 440 patients were included in the study (88.5% Hispanic). Cecal and terminal ileum intubation rates were similar in both groups (CAC: 97% and 86% versus SC: 99% and 81%, respectively). CAC did not improve ADR in comparison with SC (0.65 versus 0.52; P = 0.079); however, CAC had a higher AADR in comparison with SC (9.9% versus 4.6%; P = 0.049). CAC detected significantly more pedunculated polyps as compared with flat and sessile polyps (P = 0.011). Complication rates were similar in the CAC and SC groups (0.9% versus 0%).

CONCLUSIONS

In a predominantly Hispanic population, no difference was seen in the mean ADR with the use of CAC. However, CAC, when compared with SC, resulted in an increased AADR and mean polyp detection rate.