An oligosaccharide rich diet increases Akkermansia spp. bacteria in the equine microbiota.

Some oligosaccharides induce growth of anti-inflammatory bacterial species and induce regulatory immunity in humans as well as animals. We have shown that the equine gut microbiota and the immune-microbial homeostasis largely stabilize within the first 50 days of life. Furthermore, we have previously established that certain bacterial species in the equine gut correlated with regulatory immunity. Accordingly, we hypothesized that an oligosaccharide rich diet fed to foals during the first 50 days would increase the abundance of bacterial species associated with regulatory immunity, and that this would influence immune responses in the foals. Eight pregnant mares and their foals were fed an oligosaccharide rich diet from four weeks before expected parturition until 49 days post-partum. Six mares and foals served as control. Fecal microbiota from mares and foals was characterized using 16S rRNA gene amplicon high throughput sequencing. On Day 49 the test foals had significantly higher abundances of Akkermansia muciniphila and an unclassified Akkermansia spp.. Blood sampled from the foals on Day 7, 28 and 49 showed non-significant increases in IgA, and decreases in IgG on Day 49. In BALB/cBomTac mice inoculated with gut microbiota from test and control foals we found increased species richness, increased relative abundance of several species identified as potentially anti-inflammatory in horses, which were unclassified Clostridiales, Ruminococcaceae, Ruminococcus, Oscilospira and Coprococcus. We also found increased il10 expression in the ileum if inoculated with test foal microbiota. We conclude that an oligosaccharide diet fed to foals in the window of opportunity, the first 50 days of life, increases the abundance of anti-inflammatory species in the microbiota with potentially anti-inflammatory effects on regulatory immunity.

部分低聚糖可促进抗炎细菌类群增殖，并在人类与动物体内诱导调节性免疫应答。本研究证实，马属动物的肠道菌群与免疫-微生物稳态在出生后的前50天内基本趋于稳定。此外，本团队此前已明确，马属动物肠道内的特定细菌类群与调节性免疫存在关联。基于此，本研究提出假说：在马驹出生后的前50天内饲喂富含低聚糖的日粮，可提升与调节性免疫相关的细菌类群丰度，并进而影响马驹的免疫应答。
本研究选取8头妊娠母马及其所产马驹，在预计分娩前4周至产后49天期间饲喂富含低聚糖的日粮；另设6组母马-马驹作为对照。采用16S rRNA基因扩增子高通量测序技术，对母马与马驹的粪便菌群进行表征分析。试验组马驹在第49天时，嗜黏蛋白阿克曼氏菌（Akkermansia muciniphila）与未分类阿克曼氏菌属（Akkermansia spp.）的丰度显著升高。分别于第7、28、49天采集马驹血液样本，结果显示其IgA水平呈非显著性升高，且在第49天时IgG水平有所下降。
将试验组与对照组马驹的肠道菌群分别定植于BALB/cBomTac小鼠体内后，观察到小鼠肠道菌群的物种丰富度提升，且多种在马中被鉴定为潜在抗炎的细菌类群相对丰度升高，包括未分类梭菌目（unclassified Clostridiales）、瘤胃球菌科（Ruminococcaceae）、瘤胃球菌属（Ruminococcus）、颤螺菌属（Oscilospira）以及粪球菌属（Coprococcus）。同时，接受试验组马驹菌群定植的小鼠回肠组织中，il10基因的表达量显著升高。
本研究最终证实：在马驹出生后的前50天这一关键窗口期饲喂富含低聚糖的日粮，可提升其肠道菌群中抗炎细菌类群的丰度，进而对调节性免疫产生潜在的抗炎调控效果。