Background
Noise has multiple negative effects on the organism, and gut microbes are influenced by the environment and are closely associated with the development of diseases. Currently, the effects of chronic noise exposure on intestinal microbiota are poorly understood.
Objective
To investigate the effects of noise exposure on the structure of rat gut microbiota and to make predictions of gut microbiota function.
Methods
Male Wistar rats (6 weeks old, 160-180 g) were randomly divided into control, NE_95dB, and NE_105dB groups, 10 rats in each group. Rats in the NE_95dB and the NE_105dB groups were exposed to noise at 95 dB sound pressure level (SPL) and 105 dB SPL, respectively, 4 h per day for consecutive 30 d, while the control group was exposed to background noise. Feces were collected after the last noise exposure for intestinal microbiota detection. Based on the 16S ribosomal RNA (rRNA) gene sequencing method, the diversity and structure of microbiota in rat intestinal contents were analyzed and compared. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was applied to predict functions of the identified intestinal microbiota genes.
Results
Significant differences were found in the microbial structure of the rat gut after the designed noise exposure. In the α diversity results, there was a statistically significant difference in the Chao1 index between the NE_95dB group and the NE_105dB group (P=0.02), while there were no statistically significant differences in the Shannon and Simpson indexes between the noise exposure groups and the control group (P>0.05). The β diversity analysis results showed significant differences in species abundance between the control group and the noise exposure groups (P=0.001). Further species analysis results showed that the relative abundances of the Ruminococcaceae_NK4A214_group (P<0.05) and Peptococcaceae_unclassified (P<0.01) at the genus level were significantly higher in the NE_105dB group, and the relative abundance of Parasutterella (P<0.05) was significantly higher in the NE_95dB group compared to the control group. In addition, the Ruminococcaceae_NK4A214_group (P<0.05) was also significantly higher in the NE_105dB group compared to the NE_95dB group. The PICRUSt functional prediction analysis results showed that there were eight differential pathways between the control group and the NE_95dB group, in which D-arginine and D-ornithine metabolism, ascorbate and aldarate metabolism, carotenoid biosynthesis, glycerophospholipid metabolism, mineral absorption, NOD-like receptor signaling pathway and non-homologous end-joining were significantly down-regulated, and nucleotide metabolism was significantly up-regulated. There were 38 differential pathways between the control group and the NE_105dB group. Among them, D-arginine and D-ornithine metabolism, and mineral absorption were the differential metabolic pathways in both noise exposure groups, and both were down-regulated relative to the control group.
Conclusion
Chronic noise exposure could alter structure of rat gut microbiota and may affect metabolic functions of multiple microbiota genes.
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