| Probiotics are living microorganisms that can improve the intestinal microecological environment and complement healthy intestinal microbes to improve host health.Probiotics have been used to treat a variety of human illnesses,including diarrhea brought on by antibiotics and irritable bowel syndrome.The incidence rate of Autism spectrum disorder(ASD),a severe condition of nervous system development,has reached 1/44 in 2020,which has sparked considerable alarm from all spheres of society.Children with ASD frequently experience gastrointestinal symptoms such constipation,diarrhea,and alternating constipation and diarrhea.According to research,intestinal flora is crucial for brain growth and maturation and is directly linked to the occurrence of brain illnesses,suggesting that intestinal flora may specifically connect to ASD.Intestinal flora metabolism includes short-chain fatty acids(SCFAs),which are crucial for numerous physiological and pathological functions.In this investigation,the intestinal flora composition of kids with autism spectrum disorder was thoroughly measured and meta-analyzed.Then,using animal research,the ameliorative effects of several probiotic strains on ASD were examined.Finally,the potential benefits of probiotics for autism were further investigated with an emphasis on intestinal flora and SCFAs.The goal is to strengthen the theoretical foundation for using probiotics to treat ASD symptoms and intestinal dysfunction.The following are the primary research findings:(1)The keywords were searched through eight databases,and the relevant literature was obtained for screening and bias risk analysis.Finally,31 studies with high quality ratings were collected,including 1344 children with autism spectrum disorders around the world.The intestinal flora of normal children and children with autism spectrum disorders were systematically evaluated and analyzed by Meta-analysis.Four kinds of bacteria were selected for subgroup analysis.The results showed that the relative abundance of Bacteroides,Bacteroides and Clostridium in children with autism spectrum disorders was higher than that in normal children,while Bifidobacterium was lower than that in normal children.The results show that the main problems of intestinal flora in children with autism spectrum disorder are the increase of harmful bacteria and the decrease of beneficial bacteria.This ecological imbalance is likely to affect the development and severity of autism spectrum disorder symptoms.(2)The offspring of Wistar rats exposed to valproate(VPA)in early prenatal period to induce the behavior of ASD were used as the experimental subjects.Firstly,the offspring rats were initially determined whether they had ASD-like behavior by growth and developmental assay,and then three different types of complex probiotics,Bacillus spp.(KLB)complex probiotic,Lactobacillus spp.(LAB)complex probiotic and Saccharomyces boulardii(SB)probiotic,were investigated for their effects on The effects of probiotics on behavior,intestinal function,intestinal permeability,HE staining of colonic tissues and cellular inflammatory factors TNF-α,IL-6 and IFN-γ in rats,a model of autism spectrum disorder.In the behavioral experiments,it was found that both KLB and LAB groups could effectively improve the behavioral symptoms such as stereotyped behavior,social impairment and low exploratory ability in the model rats with autism spectrum disorder;the results of intestinal function evaluation showed that KLB,LAB and SB groups could effectively improve the intestinal function of ASD rats;The results of HE staining showed that the colons of the KLB and LAB groups were significantly protected,while the colons of the SB group still had some degree of damage.Immediately afterwards,ELISA was performed on three inflammatory factors,TNF-α,IL-6 and IFN-γ.The results showed that KLB showed a stronger advantage than LAB in reducing the level of TNF-α inflammatory cytokines;SB probiotics could also significantly reduce the level of TNF-α;IL-6 and IFN-γcellular inflammatory factors were detected,and KLB and LAB were able to significantly reduce their levels.(3)Since there are some associations between intestinal function and symptoms in rats with autism spectrum disorders,we based on intestinal flora and its metabolite short-chain fatty acids to gain insight into whether intestinal flora and short-chain fatty acids play a key role in ASD.The intestinal flora,its metabolite short-chain fatty acids,and severity of ASD rats were all examined and compared using the CARS scale,and a Spearman correlation analysis was conducted to determine the relationship between them.The results showed that the relative abundance of Clostridium,Prevotella,Clostridium faecalis,Trichosporon,and Rhodococcus spp.in the ASD model rats was significantly lower than that in the normal group,and these spp.were negatively correlated with the severity of ASD;the relative abundance of Clostridium,Desulfovibrio,and Rumenococcus spp.were significantly higher than that in the normal group,and these spp.were positively correlated with the severity of ASD.The KLB probiotic group significantly increased the relative abundance of beneficial bacteria and decreased the relative abundance of harmful bacteria.The quantitative results of short-chain fatty acids showed that the content of acetic acid and valeric acid increased and the content of butyric acid decreased in the ASD model rats,and the content of acetic acid and valeric acid was positively correlated with the severity of ASD,while the content of butyric acid was negatively correlated with the severity of ASD,so KLB probiotics could reduce the content of acetic acid and valeric acid and increase the content of butyric acid in ASD rats.In conclusion,KLB complex probiotics can effectively regulate the balance of intestinal flora and short-chain fatty acid content,thus reducing the severity of ASD symptoms.Probiotics can improve the symptoms of ASD by reconstructing the intestinal environment and balancing the content of short-chain fatty acids,providing a new idea for the treatment of ASD.Based on the above experimental results,the therapeutic mechanism of Bacillus probiotics on ASD can be further investigated in future studies to broaden the therapeutic pathway of ASD. |
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