Stool Microbiome and Metabolome Differences between Colorectal Cancer Patients and Healthy Adults

Abstract

In this study we used stool profiling to identify intestinal bacteria and metabolites that are differentially represented in humans with colorectal cancer (CRC) compared to healthy controls to identify how microbial functions may influence CRC development. Stool samples were collected from healthy adults (n = 10) and colorectal cancer patients (n = 11) prior to colon resection surgery at the University of Colorado Health-Poudre Valley Hospital in Fort Collins, CO. The V4 region of the 16s rRNA gene was pyrosequenced and both short chain fatty acids and global stool metabolites were extracted and analyzed utilizing Gas Chromatography-Mass Spectrometry (GC-MS). There were no significant differences in the overall microbial community structure associated with the disease state, but several bacterial genera, particularly butyrate-producing species, were under-represented in the CRC samples, while a mucin-degrading species, Akkermansia muciniphila, was about 4-fold higher in CRC (p<0.01). Proportionately higher amounts of butyrate were seen in stool of healthy individuals while relative concentrations of acetate were higher in stools of CRC patients. GC-MS profiling revealed higher concentrations of amino acids in stool samples from CRC patients and higher poly and monounsaturated fatty acids and ursodeoxycholic acid, a conjugated bile acid in stool samples from healthy adults (p<0.01). Correlative analysis between the combined datasets revealed some potential relationships between stool metabolites and certain bacterial species. These associations could provide insight into microbial functions occurring in a cancer environment and will help direct future mechanistic studies. Using integrated “omics” approaches may prove a useful tool in identifying functional groups of gastrointestinal bacteria and their associated metabolites as novel therapeutic and chemopreventive targets.

Gut microbiome development along the colorectal adenoma–carcinoma sequence

“…Akkermansia, a mucin-degrading bacterium in the phylum of Verrucomicrobia, has been reported to correlate with CRC in humans and in a mouse model 37,38 . We observed no difference in the abundance of Akkermansia among healthy controls, advanced adenoma and carcinoma samples (Supplementary Fig.…”

Clostridium difficile heterogeneously impacts intestinal community architecture but drives stable metabolome responses

“…This could explain why age or different antibiotic uptakes may not promote measurable metabolic differences in patients with pathogen-caused diarrhoea and that the differences within patients in each of the three Functional robustness associated with C. difficile D Rojo et al groups investigated were small regardless of patient characteristics and medical history. The effects of various pathophysiologies in the human gut metabolome have been previously examined (Saric et al, 2008;Le Gall et al, 2011;Marcobal et al, 2013;Weir et al, 2013;Bondia-Pons et al, 2014). However, no clear associations between faecal fluid metabolome patterns and individual pathophysiologies (for example, weight gain or the presence of a disease) have been previously observed; this was mainly due to large inter-individual variation.…”

“…One of the major differences between our study and previous studies examining total faecal material is that herein we focused on isolating metabolites from microbes isolated from stool material followed by metabolic profiling of gut microbiota rather than on examining total faecal fluids, which are known to contain a complex mixture of metabolites provided from the diet, the host and intestinal bacteria. Such complex mixtures are commonly investigated in metabolomics studies (Saric et al, 2008;Le Gall et al, 2011;Marcobal et al, 2013;Weir et al, 2013;Walker et al, 2014). Metabolites from intestinal bacteria (rather than dietary or host metabolites) are required to maintain and repair the large intestine and to support human health (Kibe et al, 2014).…”

“…It is notable, however, that no report to date has described the metabolomic profiling either of bacterial faecal extracts or of faecal fluids from patients with CDAD; therefore, little is known about whether the observed differences among the groups of samples are within a common range. In the case of other pathophysiologies, when using metabolite profiling of faecal fluids, it was found that: (i) only 18 faecal metabolites allowed discrimination between ulcerative colitis or IBS and healthy control patients (Le Gall et al, 2011); (ii) 99 metabolites allowed discrimination of humanised and gnotobiotic mice, although they possess quite distinct microbiota (85% of the microbial genera and species are different) (Marcobal et al, 2013); (iii) 43 metabolites were found to differ when comparing the human, mouse and rat faecal metabolomes (Saric et al, 2008); and (iv) 22 metabolites allow the discrimination of patients with colorectal cancer from healthy adults (Weir et al, 2013). In a different context, in the case of subjects that are discordant for weight, few examples exist in the literature that have examined faecal fluid metabolomes.…”

Taurocholic acid metabolism by gut microbes and colon cancer

“…4,5 Several studies have attempted to apply high-throughput sequencing followed by network correlation analysis to identify gut bacteria associated with colorectal tumors. [6][7][8][9][10][11] While each study concluded that CRC is associated with gut dysbiosis, a significant shift in the gut microbiome community structure relative to healthy control populations, there has been a lack of consistently observed dysbiotic microbiota patterns.…”