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How Colorectal Cancer Affects Gut Microbiome According to Experts

According to the findings of a new study conducted in Singapore, patients who have colorectal cancer (CRC) have a significantly changed gut microbiome, which is defined by changes in the bacterial composition. It is important to remember that these changes remain even after surgery has been performed.

How Colorectal Cancer Affects Gut Microbiome According to Experts
Image: Colorectal Cancer | InStyleHealth


According to the findings of chronic microbial dysbiosis after surgery, "the changes in gut microbiota of pre- and postoperation patients may reflect probable field alteration in the 'nondiseased' colon that predisposed them to CRC in the first place," the researchers noted. The results of this study shed light on changes that occur in the gut microbiota of postoperative colorectal cancer patients.

 

Using 16S rRNA gene sequencing analysis, the microbial composition of 49 fecal samples collected from 12 CRC patients (mean age 63.8 years, 58.3 percent men) and 25 noncancer controls (mean age 61.6 years, 56.0 percent men), both before and 6 months after surgery, was evaluated. 


The CRC patients' ages ranged from 63.8 to 63.8 years, and 58.3 percent of them were men. The evaluation of species diversity and richness required the collection of a total of 2,559,498 sequences that had been filtered.

 

The global microbial alpha diversity was shown to be considerably reduced in postoperative CRC patients, although beta-diversity analysis indicated that there was considerable segregation between CRC patients and noncancer controls. 


In addition, the analysis of microbial composition discovered that postoperative colorectal cancer patients had a gut microbiota that was more dispersed than preoperative CRC patients and controls. This finding provides additional confirmation that the microbial composition was significantly altered in this patient population in comparison to preoperative patients and controls. [Sci Rep 2022;12:9829]

 

Overall, the data revealed that the richness of bacterial species in the feces and the variety of those species were dramatically reduced in CRC patients.

 

In terms of particular taxonomic groups, the researchers discovered that the Actinobacteria and Firmicutes phyla were enriched in postoperative CRC patients, while some Bacteroidetes groups were reduced, in comparison to preoperative comparators. This was the case in both preoperative and postoperative CRC patients.

 

Even though the levels returned to normal following surgery, precarcinogenic bacteria such Bacteroides fragilis and Odoribacter splanchnicus were found to be high in preoperative CRC patients. Despite this, bacterial taxa linked to CRC advancement remained increased in the postoperative CRC group, which suggests that dysbiosis continues to exist even after curative resection has been performed. In the meantime, probiotic bacteria appeared to be present in greater numbers following CRC surgery.

 

These kinds of variations in the composition of the gut microbiota lead to differences in route. Patients who had surgery for colorectal cancer showed an increase in bacteria involved in the transfer of glutathione and glucose/mannose, among other metabolic pathways. On the other hand, it seemed like certain metabolic pathways had been turned off in this patient group.

 

In addition, the researchers noted that they showed that the incapacity to metabolize sulfate in the colonic environment was greatly decreased in preoperative CRC patients compared to noncancer controls. "In addition, a connection between increased pathogenic microorganisms and infectious disease-associated pathways may be symptomatic of an unfavorable postsurgical response,"

 

The researchers noted that future studies should entail a bigger sample size with shotgun microbiome sequencing data obtained at many time points following surgery to investigate whether or not these dysbiotic patterns genuinely persist and also correlate with illness outcomes.

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