Abstract: OBJECTIVE：Genomics was used to explore the structure and functional expression of gut microbiota in rats under high temperature and humidity environments，as well as their correlation with serum brain-gut peptide indicators. METHODS：Sixteen adult male SD rats were randomly divided into two groups：the normal temperature and humidity group and the high temperature and humidity group. The normal temperature and humidity group were placed in a constant temperature and humidity box with a temperature of (25±2) ℃ and a humidity of (50±5)%，while the high temperature and humidity group with a temperature of (40±2) ℃ and a humidity of (70±5)% for 7 days. During this period，the rats were fed and watered normally. The fecal samples of the two groups were collected in a 1.5 mL centrifuge tube，and serum samples were collected through the abdominal aorta. 16S rDNA and metagenomic sequencing methods were used to analyze fecal samples of rats in the two groups. Changes in bacterial community structure and function under high temperature and humidity environments were identified. Enzyme linked immunosorbent assay (ELISA) was used to measure serum cholecystokinin (CCK) levels in rats. Spearman correlation analysis was applied to investigate the correlation between differential microbiota and brain gut peptides. RESULTS：Animal behavioral observations indicated that rats in the high temperature and humidity group were restless，with their front paws scratching their faces and poor mental state over time，and their activity was gradually decreased. The 16S rDNA and metagenomic sequencing results showed that the high temperature and humidity environment significantly reduced the alpha and beta diversity of the intestinal microbiota compared with the normal temperature and humidity group，leading to an increase in the ratio of Firmicutes to Bacteroidetes. The core differential microbiota was obtained through species difference analysis，the up-regulated microbiota were Corynebacterium and Streptomyces，and the down-regulated microbiota were Prevotella，Corynebacterium，Helicobacter pilosum，and Ruminococcus. Functional analysis results indicated that high temperature and humidity mainly affect metabolic processes such as arginine and proline metabolism，porphyrin metabolism，retinol metabolism，and biosynthesis，as well as glycolysis/glycogenesis，ABC transporters，ribosomes，etc. The ELISA test results showed that the serum CCK content of SD rats in the high-temperature and high humidity group was significantly reduced. CONCLUSION：High temperature and humidity environments caused abnormalities in the structure and function of microbial communities significantly，which in turn affected the changes in CCK levels through core differential microbial communities，thereby affecting emotional regulation. Functional enrichment analysis showed that there was a correlation between gut microbiota and emotional changes in high temperature and humidity environments，which in turn had an important relationship with neurological diseases. This study enriches the understanding of the impact of the environment on gut microbiota and provides support for clinical diagnosis and research.

Key words: high temperature and humidity, intestinal microbiota, metagenomic, brain gut peptide