| ObjectiveBy establishing a model of cognitive impairment in premature rats,the feces of each group of rats were extracted for 16 S r RNA sequencing,and the structural characteristics of the intestinal flora of each group were analyzed and compared.Collect rat blood,serum levels of 5-hydroxytryptamine(5-HT)、 γ-aminobutyric acid(GABA)、corticotropin releasing hormone(CRH)、glucocorticoid receptor(GR)、interleukin 6(IL-6)、 tumor necrosis factor alpha(TNF-а)and brain derived neurotrophic factor(BDNF)were detected in each group.To explore the possible mechanism of cognitive impairment in premature rats from the perspective of intestinal microbiota-gut brain axis(MGBA).MethodsSprague-Dawley rats at 16-17 days of gestation were intraperitoneally injected with lipopolysaccharide for two consecutive days to establish a model of cognitive impairment,and the rats treated with intraperitoneally injected phosphate-buffered saline(PBS)were established as the control group.Cesarean section was performed on day 21 of gestation,and preterm rats were randomly assigned to healthy maternal rats for feeding.The place navigation test in the Morris water maze was used to evaluate cognition on day 30 after birth.According to the result,the preterm rats were divided into cognitive impairment group with 21 rats and normal control group with 10 rats.Hematoxylin and eosin staining was used to observe pathological changes of the hippocampus,Extract the feces of each group of rats for 16 S r RNA sequencing and analyze the structural characteristics of intestinal flora.A principal component analysis(PCA)was performed for intestinal flora.The serum of two groups of rats was collected and the levels of 5-HT,GABA,CRH,GR,IL-6,TNF-а and BDNF were detected by ELISA.ResultsIn the positioning navigation experiment of Morris water maze test,the average time to find the platform for premature cognitive impairment rats was(40±5)s,which was significantly longer than rats of the normal control group(18±4)s.In the HE staining of the hippocampus,the hippocampal neurons of the normal control group had clear structures and normal sizes.The nuclei were light blue stained and arranged in a round or oval shape.Neatly,a large number of neurons degeneration and necrosis can be seen.The 16 S r RNA intestinal flora test results showed that the intestinal flora richness index Chao 1 index and Ace index were significantly reduced in the preterm cognitive impairment group(P <0.05);while the Shannon index,which represents the diversity of the bacterial flora,was in preterm cognitive impairment The group was also significantly lower than that of the normal control group(P <0.05),suggesting that the intestinal flora richness and diversity of the premature cognitive impairment group decreased.At the phylum level,all the sample flora is mainly composed of Bacteroidetes,Pachyphyte,Proteobacteria,and Spirobacteria.Among them,Bacteroidetes and Pachyphyta are the predominance of intestinal flora of two groups of rats.There was no statistically significant difference in the abundance of Bacteroides phylum,Pachymycota and Spirobacteria in the premature cognitive impairment group compared with the normal control group(P> 0.05),while the abundance of Proteobacteria was more normal The control group increased significantly(P <0.05).At the order,family,and genus levels,compared with the normal control group,the premature cognitive impairment group had significantly lower abundances of Prutella,Bacteroides,Prevotella and Lactobacillus(P <0.05)The abundance of Staphylococcus,Crytobacterium and Oligobacterium increased significantly(P <0.05).PCA showed that the two groups of rats had significant differences in the composition of intestinal flora.The serum ELISA results of the two rats suggest that the levels of serum 5-HT,GABA,and BDNF in the premature cognitive impairment group were lower than those in the normal control group(P <0.05),while the levels of CRH,GR,IL-6,and TNF-а were higher than normal Control group(P <0.05).Conclusion(1)In the rat model of premature cognitive impairment,the hippocampus has lesions,its intestinal flora diversity and abundance are reduced,and the probiotic flora such as Pregnancy,Bacteroides,Prevotella and Lactobacillus are reduced The number of harmful bacteria such as Staphylococcus,Crytobacterium,and Oligobacteria increased.(2)Serum neurotransmitters(5-HT,GABA)in premature cognitive impairment rats decreased,brain-derived growth factor BDNF decreased,endocrine hormones(CRH,GR)and inflammatory mediators(IL-6,TNFα)increased.(3)Cognitive impairment associated with preterm birth may be related to changes in intestinal flora,and intestinal brain-axis related factors such as 5-HT,GABA,BDNF,CRH,GR,IL-6 and TNF-α may be involved in this process. |
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