Distal ileal antibiotic infusion affects the expressions of neurotransmitters in the hypothalamus of piglets. Sus scrofa

Purpose: Gut microbiota-brain axis serves as an emerging pathway affecting brain function. Hindgut has a higher proportion of microbes than foregut, however whether alteration in hindgut microbiota is related to brain functional change remains unclear. The present study used antibiotics to modulate the hindgut microbiota, to investigate the changes in the functions of porcine hypothalamus. Methods: Twelve piglets (12.08 ± 0.28 kg) fitted with T-cannula at the distal ileum were fed a standard diet and randomly assigned to two groups (n=6) for ileal infusions of saline (control group) and an antibiotic mix (ampicillin, gentamycin and metronidazole; antibiotic group), respectively. After the 25-day experiment, the microbiota and metabolites in feces, concentrations of amino acids and neurotransmitters in hypothalamus and blood, and transcriptomics profiles of hypothalamus were analyzed. Results: The results showed that the antibiotic infusion resulted in an increase in aromatic amino acids (AAA)-utilizing genera, notably Lactobacillus, and a decrease in the concentrations of AAAs including tryptophan, tyrosine and phenylalanine in feces. Correspondingly, concentrations of AAAs in the blood and hypothalamus also decreased. In the hypothalamus, the concentrations of AAAs related neurotransmitters 5-HT and dopamine decreased. Meanwhile, the compensatory upregulations of neurotransmitter transporter genes such as SERT, DAT and synthesis-related genes TPH2 and AADC were observed (adjusted P < 0.001). Furthermore, the concentrations of 5-HT and dopamine decreased in the blood. Conclusion: In conclusion, the results revealed that the ileal antibiotic infusion could affect the expressions of neurotransmitters in the porcine hypothalamus. The changes of hindgut microbial composition, circulating AAA profile and hypothalamic neurotransmitter expressions indirectly suggested that the hindgut microbiota may affect the brain functions. Overall design: Hypothalamic mRNA profiles of pigs in control and ileal antibiotic infusion groups were generated by deep sequencing, control group with 4 replicates, antibiotic group with 3 replicates, using Illumina HiSeq 2000.

研究背景与目的：肠道菌群-脑轴（Gut microbiota-brain axis）是影响大脑功能的新兴通路。相较于前肠，后肠的微生物占比更高，但后肠菌群的改变是否与大脑功能变化相关仍不明确。本研究通过抗生素调控后肠菌群，探究猪下丘脑的功能变化。方法：选取12只体质量为12.08±0.28 kg的仔猪，其回肠远端安置有T型套管（T-cannula），饲喂基础日粮并随机分为两组（n=6），分别经回肠输注生理盐水（对照组）与抗生素混合液（氨苄青霉素、庆大霉素与甲硝唑；抗生素组）。为期25天的实验结束后，对粪便中的菌群与代谢物、下丘脑及血液中的氨基酸与神经递质浓度，以及下丘脑转录组学特征进行分析。结果：研究发现，抗生素输注可增加利用芳香族氨基酸（aromatic amino acids, AAA）的菌属，尤以乳酸杆菌属（Lactobacillus）最为显著，同时粪便中色氨酸、酪氨酸与苯丙氨酸等芳香族氨基酸的浓度降低。相应地，血液与下丘脑中的芳香族氨基酸浓度也随之下降。在下丘脑中，与芳香族氨基酸相关的神经递质5-羟色胺（5-HT）与多巴胺的浓度降低。同时，观察到神经递质转运体基因（如SERT、DAT）及合成相关基因（如TPH2、AADC）的代偿性上调（校正后P<0.001）。此外，血液中5-羟色胺与多巴胺的浓度也有所下降。结论：综上，本研究结果表明，回肠抗生素输注可影响猪下丘脑神经递质的表达。后肠菌群组成、循环芳香族氨基酸谱及下丘脑神经递质表达的变化，间接提示后肠菌群可能对大脑功能具有调控作用。整体实验设计：采用Illumina HiSeq 2000平台进行深度测序，获取对照组与回肠抗生素输注组仔猪下丘脑的mRNA表达谱，其中对照组设置4个生物学重复，抗生素组设置3个生物学重复。