Effects of subchronic oral toxic metal exposure on the intestinal microbiota of mice

Oral exposure to toxic metals such as cadmium (Cd), lead (Pb), copper (Cu) and aluminum (Al) can induce various adverse health effects in humans and animals. However, the effects of these metals on the gut microbiota have received limited attention. The present study demonstrated that long-term toxic metal exposure altered the intestinal microbiota of mice in a metal-specific and time-dependent manner. Subchronic oral Cu exposure for eight weeks caused a profound decline in gut microbial diversity in mice, whereas no significant changes were observed in groups treated with other metals. Cd exposure significantly increased the relative abundances of organisms from the genera Alistipes and Odoribacter and caused marked decreases in Mollicutes and unclassified Ruminococcaceae. Pb exposure significantly decreased the abundances of eight genera: unclassified and uncultured Ruminococcaceae, unclassified Lachnospiraceae, Ruminiclostridium_9, Rikenellaceae_RC9_gut_group, Oscillibacter, Anaerotruncus and Lachnoclostridium. Cu exposure affected abundances of the genera Alistipes, Bacteroides, Ruminococcaceae_UCG-014, Allobaculum, Mollicutes_RF9_norank, Rikenellaceae_RC9_gut_group, Ruminococcaceae_unclassified and Turicibacter. Al exposure increased the abundance of Odoribacter and decreased that of Anaerotruncus. Exposure to any metal for eight weeks significantly decreased the abundance of Akkermansia. These results provide a new understanding regarding the role of toxic metals in the pathogenesis of intestinal and systemic disorders in the host within the gut microbiota framework.