Characteristics of Gut Microbiota and Fecal Metabolites in Patients with Colorectal Cancer-Associated Iron Deficiency Anemia

Patients with colorectal cancer (CRC) have a high prevalence of iron deficiency anemia (IDA), and the gut microbiota is closely related to iron metabolism. We performed metagenomic and metabolomic analyses of stool samples from 558 eligible samples, including IDA CRC patients (IDA, n = 69), non-anemia CRC patients (Non-Anemia, n = 245), and healthy controls (CTRL, n = 244), to explore the dynamically altered gut microbes and their metabolites. Compared with the CTRL group, fecal bacteria in both the IDA group and the Non-Anemia group showed a decrease in alpha diversity and changes in microbial communities. Flavonifractor plautii (F. plautii) increases progressively from CTRL to Non-Anemia to IDA, accompanied by decreased trimethoxyflavanone and a downregulated KO gene, megDIII. In the Non-Anemia group, Parabacteroides showed a specifically elevated abundance positively correlated with enriched 1,25-dihydroxyvitamin D3. The intricate correlations among gut microbiota, metabolites, and KO genes were uncovered and highlighted, implicating an aberrant iron metabolism vulnerable to chronic inflammation during the deterioration of the anemic condition. Furthermore, the amount of F. plautii in feces achieved independent and effective prediction performance for the poor outcome of CRC. Perturbed host-microbe interplays represent a novel prospect for explaining the pathogenesis of CRC-associated IDA. The fecal microbial features also reflect the associations between IDA and elevated CRC recurrence risk.