1.
The Gut Microbiome in Early Life Stress: A Systematic Review.
Agusti, A, Lamers, F, Tamayo, M, Benito-Amat, C, Molina-Mendoza, GV, Penninx, BWJH, Sanz, Y
Nutrients. 2023;15(11)
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Children exposed to early life stress (ELS) show alterations in brain development and are at increased risk of developing mental illness. This study aims to clarify whether ELS influences the gut microbiome and whether this can be a predictor for the development of mental disorders. 13 articles were included in this systemic review. 4 looked at pre-natal stress and 9 at post-natal stress. Prenatal stress (via maternal stress) may be associated with an increase in Proteobacteria phylum and with a lower abundance of Bifidobacterium and lactic acid bacteria. In the postnatal group, greater microbiome diversity was related to lower depression and anxiety. In boys scores for adaptive skills were higher in those with good levels of Bifidobacterium. A positive association was found between EA (early adversity) experiences and gastrointestinal symptoms and anxiety. This review demonstrates links between ELS and gut microbiome changes. Further research will be necessary to draw more robust conclusions.
Expert Review
Conflicts of interest:
None
Take Home Message:
- This systematic review consolidated and discussed existing evidence on the link between early life stress (ELS) and changes to the human microbiome
- Exposure to ELS, prenatal or postnatal during childhood and adolescence, may impact mental and physical health.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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X
B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction
A systematic review was conducted to consolidate clinical evidence examining the impact of early life stress (ELS) on the human intestinal microbiome.
Method
Thirteen observational studies were included in the review, sourced from Pubmed, Scopus, Web of Science, and EMBASE. Methodological quality was assessed using the Newcastle-Ottawa Assessment Scale (NOS), with most studies scoring seven or eight out of nine stars.
Study designs varied, including prospective prenatal studies, postnatal longitudinal studies, case-control studies, and cross-sectional studies. Four prenatal studies were prospective in design. The other nine postnatal studies included one longitudinal study, five case-control studies, and three cross-sectional studies. All 13 studies were published between 2015 and 2022. Because study designs and outcome assessments varied, the results were presented in a narrative form. Data was extracted by 2 independent authors.
Results
The primary findings from the review were as follows:
- Four longitudinal stress studies indicated that pregnant mothers experiencing psychological stress, increased cortisol levels, HIV, and lack of social support exhibited a lower abundance of beneficial Bifidobacterium and an increased abundance of Enterobacter genus.
- One postnatal stress longitudinal study (n=260) demonstrated lower depression and anxiety and improved internalising behaviour in patients with high microbiome diversity.
- . One postnatal stress case-control study (n=344) showed changes in the microbiome and an abundance of several bacterial taxa in stressed groups, including genera Prevotella, Bacteroides (Bacteroidetes), Coprococcus, Streptococcus, and Escherichia.
- One cross-sectional study of 128 adults without psychiatric conditions revealed that higher stress correlated with increased levels of Bacteroides, Parabacteroides, Rhodococcus, Methanobrevibacter, and Roseburia at the genus level, as well as lower Phascolarcto bacterium and Firmicutes at the phylum level.
- One large prospective study (n=446) found infants exposed to higher cumulative stress exhibited an increased relative abundance of Proteobacteria groups and lower Bifidobacterium.
Conclusion:
Due to the inconsistency of study designs and their results this review failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both.
Clinical practice applications:
- Early life stress, and alterations in the gut microbiome, have been linked to mental health conditions
- Maternal prenatal stress may be linked to emotional, behavioural, and cognitive outcomes in infants.
Considerations for future research:
- Future research should standardise questionnaires, to ensure consistency and comparability across studies
- Additionally, future studies should consider using standard procedures and specific species and strain resolution shotgun metagenomics sequencing
- Consideration should be given to the influence of environmental variables (diet, physical activity, etc.) and sex in gut microbiome analysis.
Abstract
Exposure to early life stress (ELS), prenatal or postnatal during childhood and adolescence, can significantly impact mental and physical health. The role of the intestinal microbiome in human health, and particularly mental health, is becoming increasingly evident. This systematic review aims to summarize the clinical data evaluating the effect of ELS on the human intestinal microbiome. The systematic review (CRD42022351092) was performed following PRISMA guidelines, with ELS considered as exposure to psychological stressors prenatally and during early life (childhood and adolescence). Thirteen articles met all inclusion criteria, and all studies reviewed found a link between ELS and the gut microbiome in both prenatal and postnatal periods. However, we failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both. The inconsistency of results is likely attributed to various factors such as different experimental designs, ages examined, questionnaires, timing of sample collection and analysis methods, small population sizes, and the type of stressors. Additional studies using similar stressors and validated stress measures, as well as higher-resolution microbiome analytical approaches, are needed to draw definitive conclusions about the links between stress and the human gut microbiome.
2.
Effects of probiotics on preventing caries in preschool children: a systematic review and meta-analysis.
Meng, N, Liu, Q, Dong, Q, Gu, J, Yang, Y
The Journal of clinical pediatric dentistry. 2023;47(2):85-100
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Caries are caused by cariogenic microorganisms in plaque biofilms that ferment dietary carbohydrates to produce acids, resulting in the loss of minerals from the hard tissue of teeth and the formation of cavities. This study's aim was to evaluate the potential of probiotics in preventing caries in preschool children. This study was a systematic review and meta-analysis of seventeen studies with a total of 3781 preschool children (divided into an experimental group (n = 2047) and a control group (n = 1734)). Results showed that probiotics could effectively prevent dental caries, of which Lactobacillus rhamnosus was more effective than other bacteria in preventing dental caries. Probiotics reduced the high concentration of Streptococcus mutans in saliva but could not reduce the number of lactic acid bacteria in saliva and dental plaques. Authors concluded that since there is still a lack of relevant research on the dose, route of administration, and frequency of probiotic use, further randomised controlled studies are needed to standardise the use of probiotics and achieve more beneficial effects before they are generally used in clinical practice.
Abstract
This paper systematically evaluate the effects of probiotics on preventing caries in preschool children. The present systematic review was conducted following the Transparent Reporting of Systematic Reviews and Meta-Analyses (PRISMA) guidelines and recorded in the International prospective register of systematic reviews (PROSPERO) database (registration no: CRD42022325286). Literature were screened from PubMed, Embase, Web of Sciences, China National Knowledge Infrastructure (CNKI), Wanfang and other databases from inception to April 2022 to identify randomized controlled trials on the clinical efficacies of probiotics in preventing dental caries in preschool children and extract relevant data. The meta-analysis was performed using the RevMan5.4 software and the Stata16. Cochrane handbook was used to assess the risk of bias. The Grading of Recommendations Assessment, Development and Evaluation (GRADEprofiler 3.6) was used to determine the evidence quality. A total of 17 randomized controlled trials were eligible, of which two trials had certain levels of bias and 15 had a low risk of bias. Evidence quality assessment showed that the included trials were of medium quality. The meta-analysis results showed that Lactobacillus rhamnosus was associated with a reduced incidence (p = 0.005) and progression (p < 0.001) of caries in preschool children. Probiotics could reduce the number of high-level Streptococcus mutans in saliva (p < 0.00001) but could not reduce the number of Streptococcus mutans in dental plaque nor the amount of Lactobacillus in the saliva and dental plaque. Current evidence shows that probiotics could prevent caries in preschool children, but Lactobacillus rhamnosus was more effective in preventing caries than others. Although probiotics could reduce high levels of Streptococcus mutans in saliva, they could not reduce the amount of Lactobacillus in saliva and dental plaque.
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Characterization of the Oral and Gut Microbiota in Patients with Psoriatic Diseases: A Systematic Review.
Todberg, T, Kaiser, H, Zachariae, C, Egeberg, A, Halling, AS, Skov, L
Acta dermato-venereologica. 2021;101(7):adv00512
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Psoriasis is a common inflammatory skin disease that results in patches of dry, scaly skin that can be itchy or sore. Psoriatic arthritis is an inflammatory arthritis that affects up to 30% of psoriasis patients. There is growing interest in the association between the microbiome and inflammatory conditions. This systematic review examined the role of the oral and gut microbiota and the effect of probiotics in patients with psoriasis and/or psoriatic arthritis. 23 studies were included in the analysis. Studies examined the microbiota using culture or 16S ribosomal RNA gene sequencing analysis. The results showed an increased presence of Candida in the mouth, and an altered gut microbiota in patients with psoriatic disease compared with healthy controls. Probiotics were associated with a significant decrease in psoriasis severity, but the microbiota was unchanged. The study authors concluded that further research is required into the role of the microbiome in patients with psoriasis.
Abstract
Advances in technology have led to an increased number of studies investigating the microbiome in patients with psoriasis. This systematic review examined data regarding the oral and gut microbiota in patients with psoriasis and/or psoriatic arthritis and the effect of probiotics on the microbiota and severity of psoriasis. Of 1,643 studies, 23 were included (22 observational, 1 interventional). Studies examined the microbiota using culture or 16S rRNA gene sequencing analysis. All culture-based studies identified an increased presence of oral Candida in patients with psoriasis, whereas small variations in the oral microbiota were found in a 16S rRNA gene-based study. All 16S rRNA gene sequencing based studies agreed that the gut microbiota of patients with psoriatic disease differed from that of healthy controls, but the results were heterogeneous. Probiotics were associated with a significant improvement in the severity of psoriasis, but did not change microbiota. Overall, studies lacked relevant inclusion criteria and baseline information. In conclusion, the role of the microbiota in patients with psoriasis requires further investigation using more robust methods.