(P13-021-23) Prune Consumption Does Not Reduce Colon Tumor Development but Alters the Microbiome and Increases Short Chain Fatty Acid Production

Objectives: To investigate the chemopreventive activity of prunes, we conducted a cancer endpoint study on the ability of prunes to reduce tumorigenicity, alter the gut microbiome, and reduce inflammation status.

Methods: 78 male Wistar rats were evenly distributed into 5% prune diet or 10% prune diet or prune free control diet for 32 weeks. Prune puree was incorporated into the diets at 5% or 10% of energy. Rats were given a weekly injection of a colon-specific carcinogen for 15 weeks. Microbiome analysis of cecal content and colonic pellets was conducted by 16s rRNA sequencing and whole metagenome sequencing. Cecal short-chain fatty acids (SCFAs) were analyze by GC. Microbial metabolites p-cresol and indole in
feces were measured by HPLC. Serum calprotectin and inflammatory cytokines IL-18, IL-1β were measured by ELISA assay and multiplexed ELISA assay respectively.

Results: No difference in colonic tumor number was observed among groups. Prune groups had a greater empty cecum weight (p=0.01), cecum contents weight (p=0.04), and cecal SCFAs amount (p < 0.0001) than the basal group, indicating greater fermentation. The α-diversity and β-diversity microbial analysis indicated that prune feeding increased the taxonomic richness and altered the
bacterial species composition (p < 0.001). At the genus level, the abundances of Prevotella and Paraprevotella were elevated in the prune groups. Fecal metabolite concentrations of p-cresol and indole did not differ among groups. Serum calprotectin and IL-18 were not different among groups, but IL-1β tended to be elevated in the 10% prune relative to the basal group (p < 0.1).

Conclusions: Prune feeding had no effect on colonic tumor number and inflammation in carcinogen-treated rats, but increased large intestinal fermentation and SCFA production and altered microbial abundance, increasing microbial richness. These microbiome changes may have implications for other health benefits of prune consumption.

Funding Sources: Californian Prune Board