Associations among dietary nitrosamines intake, fecal N-nitroso compounds and intestinal microbiota in adults according to intestinal mucosa damage

Abstract

Dietary intake of N-nitroso compounds (NOCs) has been proposed as one of the mechanisms explaining the association of red and processed meat consumption with the increased risk of colorectal cancer (CRC). Endogenous NOCs can also be formed along the intestine, being finally excreted in feces. The intestinal microbiota could play a role in the formation of endogenous NOCs and on their impact on health. In this work, the median fecal total and heme NOC concentrations of 46 volunteers were used to split the sample and analyze discriminant differences in the relative abundance of intestinal microbiota members and fecal short-chain fatty acids (SCFAs). The association of intestinal microbiota with fecal NOCs in relation to the degree of mucosa damage was evaluated. PERMANOVA analysis investigated associations between dietary factors and fecal NOCs with the microbiota. Shifts in the relative abundance of Roseburia, Prevotella or Escherichia_Shigella according to fecal NOC concentrations were detected in stool samples. The genera Escherichia_Shigella, Ruminococcus_torques group, Subdoligranulum or Intestinibacter were found as predictors of fecal NOC concentrations depending on intestinal mucosa lesions. Furthermore, some of these genera were positively correlated with the intake of nitrate, nitrite and nitrosamines (NAs), precursor compounds of endogenous NOCs. PERMANOVA analysis showed that these dietary precursors could also be related with the intestinal microbiota profile of volunteers and suggested that specific intestinal bacterial genera rather than general microbial changes were associated with fecal NOCs. Our study supports a link among specific intestinal microorganisms, fecal NOCs, and intestinal mucosal damage.