Colorectal cancer in inflammatory bowel disease: a review of the role of gut microbiota and bacterial biofilms in disease pathogenesis

The risk of colorectal cancer (CRC) is increased in patients with inflammatory bowel disease (IBD), particularly in extensive ulcerative colitis (UC) and Crohn's colitis. Gut microbiota have been implicated in the pathogenesis of CRC via multiple mechanisms, including the release of reactive oxygen species and genotoxins, and induction of inflammation as well as activation of the immune response. Gut microbiota can enhance their carcinogenic and pro-inflammatory properties by organizing into biofilms, potentially making them more resistant to the host's immune system and to antibiotics. Colonic biofilms have the capacity to invade colonic tissue and accelerate tumorigenesis in tumor-prone models of mice. In the context of IBD, the prevalence of biofilms has been estimated to be up to 95%. Although the relationship between chronic inflammation and molecular mediators that contribute to IBD-associated CRC is well established, the role of gut microbiota and biofilms in this sequence is not fully understood. Because CRC can still arise in the absence of histologic inflammation, there is a growing interest in identifying chemopreventive agents against IBD-associated CRC. 5-aminosalicylates, commonly used in the treatment of UC, have antimicrobial and anti-carcinogenic properties that might have a role in the chemoprevention of CRC via the inhibition or modulation of carcinogenic gut microbiota and potentially biofilm formation. Whether biologics and other IBD-targeted therapies can decrease the progression towards dysplasia and CRC via mechanisms independent of inflammation is still unknown. Further research is warranted to identify potential new microbial targets of therapy for chemoprevention of dysplasia and CRC in IBD.

An Increased Abundance of Clostridiaceae Characterizes Arthritis in Inflammatory Bowel Disease and Rheumatoid Arthritis: A Cross-sectional Study

BACKGROUND

Inflammatory bowel diseases (IBDs) are a group of heterogeneous inflammatory conditions affecting the gastrointestinal tract. Although there is considerable evidence linking the gut microbiota to intestinal inflammation, there is limited knowledge on its potential role in the development of extraintestinal manifestations of IBD.

METHODS

Four groups of patients were included: IBD-associated arthropathy (IBD-A); IBD without arthropathy (IBD-N); rheumatoid arthritis (RA); and non-IBD, nonarthritis controls. DNA from stool samples was isolated and sequenced using the Illumina platform. Paired-end reads were quality-controlled using SHI7 and processed with SHOGUN. Abundance and diversity analyses were performed using QIIME, and compositional biomarker identification was performed using LEfSe.

RESULTS

One hundred eighty patients were included in the analysis. IBD-A was associated with an increased abundance of microbial tyrosine degradation pathways when compared with IBD-N (P = 0.02), whereas IBD-A and RA patients both shared an increased abundance of Clostridiaceae when compared with controls (P = 0.045). We found that history of bowel surgery was a significant source of variability (P = 0.001) among all IBD patients and was associated with decreased alpha diversity and increased abundance of Enterobacteriaceae (P = 0.004).

CONCLUSIONS

An increased abundance of gut microbial tyrosine degradation pathways was associated with IBD-A. An increased abundance of Clostridiaceae was shared by both IBD-A and RA patients and suggests a potentially common microbial link for inflammatory arthritis. The increased abundance of Enterobacteriaceae, previously reported in IBD, may be due to the effects of previous bowel surgery and highlights the importance of controlling for this variable in future studies.

Gut Microbial Carbohydrate Metabolism Hinders Weight Loss in Overweight Adults Undergoing Lifestyle Intervention With a Volumetric Diet

The rising incidence of obesity requires the reevaluation of our current therapeutic strategies to optimize patient outcomes. The objective of this study was to determine whether compositional and functional characteristics of the gut microbiota in adults predict responses to a comprehensive lifestyle intervention program in overweight and obese adults. We recruited 26 participants from the Mayo Clinic Obesity Treatment Research Program between August 6, 2013, and September 12, 2013, to participate in a lifestyle intervention program for weight loss. Adults aged 18 to 65 years with a body mass index of 27 to 39.9 kg/m² and able to provide informed consent were included in the study. Fecal stool samples were obtained at baseline and after 3 months. Loss of at least 5% of baseline weight after 3 months was defined as success. Clinical characteristics and gut microbial composition and function were compared between those who achieved at least 5% and those who achieved less than 5% weight loss. After 3 months, 9 of 26 participants lost at least 5% of their weight. The mean weight loss was 7.89 kg (95% CI, 6.46-9.32 kg) in the success group and 1.51 kg (95% CI, 0.52-2.49 kg) in the less than 5% weight loss group. An increased abundance of Phascolarctobacterium was associated with success. In contrast, an increased abundance of Dialister and of genes encoding gut microbial carbohydrate-active enzymes was associated with failure to lose 5% body weight. A gut microbiota with increased capability for carbohydrate metabolism appears to be associated with decreased weight loss in overweight and obese patients undergoing a lifestyle intervention program.