The gut microbiota plays a key role in host metabolic thermogenesis by activating UCP1 and increasing the browning process of white adipose tissue (WAT), especially in cold environments. However, the crosstalk between the gut microbiota and the host, which lacks functional UCP1, making them susceptible to cold stress, has rarely been illustrated. We used male piglets as a model to evaluate the host response to cold stress via the gut microbiota (four groups: room temperature group, n = 5; cold stress group, n = 5; cold stress group with antibiotics, n = 5; room temperature group with antibiotics, n = 3). We found that host thermogenesis and insulin resistance increased the levels of serum metabolites such as glycocholic acid (GCA) and glycochenodeoxycholate acid (GCDCA) and altered the compositions and functions of the cecal microbiota under cold stress. The gut microbiota was characterized by increased levels of Ruminococcaceae, Prevotellaceae, and Muribaculaceae under cold stress. We found that piglets subjected to cold stress had increased expression of genes related to bile acid and short-chain fatty acid (SCFA) metabolism in their liver and fat lipolysis genes in their fat. In addition, the fat lipolysis genes CLPS, PNLIPRP1, CPT1B, and UCP3 were significantly increased in the fat of piglets under cold stress. However, the use of antibiotics showed a weakened or strengthened cold tolerance phenotype, indicating that the gut microbiota plays important role in host thermogenesis. Our results demonstrate that the gut microbiota-blood-liver and fat axis may regulate thermogenesis during cold acclimation in piglets.

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The gut microbiota in sows is important for the health of the host, and potential benefits may also be transferred to piglets during pregnancy. Therefore, systematic studies investigating the changes in the gut microbiota of sows are needed to elucidate the microbial compositions and functions. This study was conducted at 12 time points to investigate the temporal variations in gut microbiota on Days 27, 46, 64, 81, 100, and 113 during gestation (G) and Days 3, 5, 7, 10, 14, and 21 during lactation (L). Results suggested that the gut microbiota changed across the perinatal period with microbial function and abundance varying between the prenatal and postnatal periods. The alpha diversity was higher in the postnatal period than in the prenatal period. Thirty-eight genera were distributed between the two periods with Methanobrevibacter, Desulfovibrio, Akkermansia, and Turicibacter being enriched in the prenatal period while Eubacterium, Actinobacillus, Paludibacter, Butyricimonas, Megasphaera, Succiniclasticum, Acidaminococcus, and Rummeliibacillus were enriched in the postnatal period. Analysis done at the different time points of the prenatal period suggested that Days 27 and 113 had more microbial biomarkers than other days. Bacteroidales, Bacteroidia, and Prevotella were enriched on the 27th day, while bacteria belonging to the Clostridium and Ruminococcaceae were enriched on the 113th day. On the other hand, Clostridiales, Ruminococcaceae, Clostridia, and unclassified Christensenellaceae were enriched three days after delivery. Predicted microbial KO functions were also more enriched on Day 27 of the gestation period and Day 3 of the lactation period. Random forest, a machine learning method, was used to identify the top five important genera of Megasphaera, Stenotrophomonas, Phyllobacterium, Catenibacterium, and Turicibacter, while the most important function was arginine and proline metabolism. These systematic results provide important information for the gut microbiota of sows.

The circadian rhythm of gut microbiota is an important biological rhythm that plays a crucial role in host health. However, few studies have determined the associations between the circadian rhythm and gut microbiota in laying hens. The present experiment investigated the circadian rhythm of fecal microbiota in laying hens. Feces samples were collected from 10 laying hens at nine different time points (06:00–12:00–18:00–00:00–06:00–12:00–18:00–00:00–06:00) to demonstrate the circadian rhythm of fecal microbiota. The results showed that the α and β diversity of the fecal microbiota fluctuated significantly at different time points. Beta nearest taxon index analysis suggested that assembly strategies of the abundant and rare amplicon sequence variant (ASV) sub-communities were different. Abundant ASVs preferred dispersal limitation (weak selection), and rare ASVs were randomly formed due to the “non-dominant” fractions. Highly robust fluctuations of fecal microbiota at the phylum level were found. For example, Firmicutes and Proteobacteria fluctuated inversely to each other, but the total ratio remained in a dynamic balance over 48 h. We identified that temporal dynamic changes had a significant effect on the relative abundance of the important bacteria in the feces microbial community using the random forest algorithm. Eight bacteria, Ruminococcus gnavus, Faecalibacterium, Ruminococcaceae, Enterococcus cecorum, Lachnospiraceae, Clostridium, Clostridiales, and Megamonas, showed significant changes over time. One unexpected finding was the fact that these eight bacteria belong to Firmicutes. The pathways showed significant fluctuation, including xenobiotic biodegradation and metabolism, carbohydrate metabolism, and amino acid metabolism, which were consistent with the metabolic functions of amino acids and carbohydrates from the feed. This study showed that the defecation time may be an important factor in the diversity, proportion, and functions of the feces microbial community. However, there was no circadian rhythm of microbial community assembly confirmed by JTK_Cycle analysis. These results might suggest there was no obvious circadian rhythm of fecal microbiota in laying hens under common light.

BackgroundThe gut microbiota plays a key role in the host metabolic thermogenesis by activating uncoupling protein 1 (UCP1) and increasing the browning process of white adipose tissue, especially in a cold environment. However, the crosstalk between gut microbiota and pigs, which lack functional UCP1 making them susceptible to cold, has rarely been illustrated. We used male piglets as a model to evaluate the host response to cold stress via the gut microbiota. ResultsWe found that host thermogenesis and insulin resistance with increased serum metabolites, such as glycocholic acid (GCA), glycochenodeoxycholate (GCDCA), and chenodeoxycholate (CDCA), and altered cecal microbiota compositions and functions under cold stress. Using transcriptomics technology, we found that cytochrome P450, family 8, subfamily b, polypeptide 1 (CYP8B1), FXR, FFAR2, and FFAR3, which are related to bile acid and short-chain fatty acid metabolism, increased in the liver under cold stress. In addition, the fat lipolysis genes CLPS, PNLIPRP1, carnitine palmitoyltransferase 1B (CPT1B), and uncoupling protein 3 (UCP3) were significantly increased in the fat of piglets under cold stress. However, microbiota depletion via treatment with mixed antibiotics weakened the effect on the genes CYP8B1, FFAR2, FFAR3, and CPT1B genes, indicating that the gut microbiota plays important roles in the host thermogenesis. ConclusionsOur results demonstrate that the gut microbiota-blood-liver and fat axis may regulate thermogenesis during cold acclimation in piglets.