肠道微生物及其宏基因组影响母猪杀婴行为的机制

Maternal infanticide is an extreme symptom of failure of maternal behaviour, which is defined as an active attack to piglets by sows using the jaws, resulting in dead or serious bite wounds within 24h after starting of parturition. It is very difficult to early discover and prevent the maternal infanticide behavior because the sows will not show any obvious symptoms indicating the occurring of maternal infanticide behavior before parturition. Similar to human puerperal psychosis, maternal infanticide is a complex behavior trait. The previous studies have been indicated that gut microbiota and its metabolites can significantly affect the functions of host nervous system and induce the behaviors of anxiety, depression and stress response. A collaborative cross population has been constructed by our laboratory and the incidence of maternal infanticide behavior achieved 10% in the F5 and F6 sows. Therefore, in this project, we will use the F5 and F6 sows as the experimental animals. We already collected the feces and serum samples from 50 sows observed maternal infanticide behavior and 50 counterparts showing normal maternal behavior at the two time points, including one week before parturition and two hours after giving birth. We will use metagenome-wide association study to identify gut microbes and metagenomic function markers associated with maternal infanticide. The causality between the isolated bacterial species or strains and maternal infanticide will be confirmed by using germ-line free mice or specific-pathogen free (SPF) sows. Furthermore, in this project, metabolites, reproduction hormones and neurotransmitters in serum will be measured and their concentrations will be compared between maternal infanticidal sows and normal sows. The concentrations of neurotransmitters and the expression levels of related genes will be determined and compared in hypothalamus between maternal infanticidal sows and normal sows. By integrative analysis of multiple omics data, the mechanism how gut microbiome affects sow maternal infanticide through brain-gut-microbiota axis will be elucidated.

母猪杀婴行为是指母猪在分娩开始后24小时之内咬死或咬伤自身所产仔猪的一种异常行为。由于母猪分娩前没有明显的产生该行为的征兆，所以很难早期发现和预防，与人类产后抑郁症类似，是个复杂的行为性状。许多已有研究表明肠道菌群及其代谢产物能通过影响宿主神经系统，导致抑郁症、焦虑症和压力反应等行为的显著改变。因此，本项目将使用实验室已创建的杀婴行为发生频率高达10%的嵌合群体F5、F6母猪作为研究材料，收集50头杀婴行为母猪和50头正常母猪分娩前一周和分娩开始后两小时内的粪便和血清样品，利用宏基因组关联分析分离与母猪杀婴行为相关的肠道菌群种类和宏基因组标记，并通过无菌小鼠或特定菌群缺失（SPF）猪给予验证。测定和比较杀婴行为及正常行为母猪分娩时血液中代谢组、激素和各种神经递质的含量，比较下丘脑神经递质分泌和基因表达差异，采用多组学手段阐明肠道微生物通过细菌-肠-脑轴影响杀婴行为的机理。

本项目在两个母猪群体72头杀婴行为母猪和67头正常母猪中采集了分娩前5天和分娩后24小时内的粪便和血清样品，研究了肠道菌群对母猪杀婴行为的影响机理。采用16S rRNA基因V3-V4区测序和宏基因组测序，比较了分娩前后杀婴行为母猪和正常母猪肠道微生物组成差异并分离鉴定了与杀婴行为密切相关的肠道微生物种类。发现杀婴母猪产前肠道中富集了Turicibacter sanguinis、Coprococcus cutus以及Lachnospiraceae、Ruminococcaceae、Lactobacillus、Clostridium内的多个菌种，Lactobacillus、Clostridium、Lachnospiraceae和Ruminococcaceae均已报道与肠道中五羟色胺浓度和转运以及抗抑郁药使用相关，因此是导致杀婴行为的重要菌种。杀婴行为母猪产后肠道中富集了Ruminococcus torques和5个Lactobacillus内菌种。利用宏基因组测序数据，发现磷酸转移酶系统（PTS）、金黄色葡萄球菌感染和阿米巴病通路在杀婴母猪产前肠道中富集，而硫辛酸代谢、矿物质吸收、四环素生物合成等功能通路在正常母猪产前肠道菌群宏基因组中富集。PTS、金黄色葡萄球菌感染、脂多糖合成、花生四烯酸代谢等KEGG通路在杀婴行为母猪产后肠道中富集，而四环素生物合成、O-糖苷生物合成通路和动物线粒体自噬通路等在正常母猪产后肠道中富集。血清代谢组、生殖激素和神经递质分析发现甲状腺素、牛磺酸、多巴胺、去加肾上腺素、催产素、雌二醇、L-谷氨酸、7α-脱氢表雄酮和PGE2 1-甘油酯等代谢物质在杀婴母猪产前血清中富集。四氢皮质酮、西酞普兰和PGE2在正常母猪血清中富集。杀婴母猪和正常母猪间的粪便代谢组也存在显著差异，L-甲状腺素、组胺和睾酮均在杀婴母猪粪便中富集，而雄甾酮、脱氧皮质酮、四氢皮质酮、西酞普兰醛和泛酸在正常组富集。杀婴和正常母猪间差异的血清和粪便代谢物与差异菌种的丰度间存在显著相关性。结合16S rRNA基因测序，宏基因组测序，血清、粪便代谢组，血清相关生殖激素、神经递质等数据，采用多组学手段初步阐释菌群影响母猪杀婴行为的可能机理。项目执行期间发表第一标注论文8篇，培养硕、博士研究生6人，做学术报告3次。

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