Postnatal probiotic supplementation can prevent and optimize treatment of childhood asthma and atopic disorders: A systematic review of randomized controlled trials

Influence of the gut and airway microbiome on asthma development and disease

There are ample data to suggest that early-life dysbiosis of both the gut and/or airway microbiome can predispose a child to develop along a trajectory toward asthma. Although individual studies show clear associations between dysbiosis and asthma development, it is less clear what (collection of) bacterial species is mechanistically responsible for the observed effects. This is partly due to issues related to the asthma diagnosis and the broad spectrum of anatomical sites, sample techniques, and analysis protocols that are used in different studies. Moreover, there is limited attention for potential differences in the genetics of individuals that would affect the outcome of the interaction between the environment and that individual. Despite these challenges, the first bacterial components were identified that are able to affect the transcriptional state of human cells, ergo the immune system. Such molecules could in the future be the basis for intervention studies that are now (necessarily) restricted to a limited number of bacterial species. For this transition, it might be prudent to develop an ex vivo human model of a local mucosal immune system to better and safer explore the impact of such molecules. With this approach, we might move beyond association toward understanding of causality.

The efficacy and safety of oral microecological agents as add-on therapy for atopic dermatitis: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Atopic dermatitis (AD) is a common skin disease that is hard to completely cure in a short time. Guidelines recommend the use of topical corticosteroids (TCS) as first-line anti-inflammatory therapy for AD, but long-term use has significant side effects. Microecological agents (MA), including probiotics, prebiotics and synbiotics, have been widely reported as a potential adjunctive therapy of AD, but whether MA can contribute to AD treatment is currently controversial. Therefore, we conducted a systematic review and meta-analysis to investigate whether MA as an add-on therapy for AD has synergistic and attenuated effects and to further understand the role of MA in clinical interventions for AD.

METHODS

We systematically searched Medline, Embase, Web of Science, Cochrane Library and PsycINFO databases up to Apr 11, 2023, and bibliographies were also manually searched, for potentially relevant studies regarding MA as additional therapy of AD. The Cochrane Risk of Bias Tool for assessing risk of bias was used to assess the quality of randomized controlled trials (RCTs). Two reviewers screened studies, extracted data, and evaluated the risk of bias independently. The primary outcomes (SCORAD scores and the number of adverse events) and the secondary outcomes (pruritus scores, the quality of life and the frequency of TCS) were extracted from each article. The data were combined and analyzed to quantify the safety and efficacy of the treatment. R (V4.4.3) software was used for data synthesis. The certainty of the evidence was evaluated with the Grade of Recommendation, Assessment, Development and Evaluation (GRADE) system. We also performed a trial sequential analysis to assess the reliability of the evidence.

RESULTS

A total of 21 studies, including 1230 individuals, were identified, 20 of which met the eligibility criteria for the meta-analysis. Our pooled meta-analyses showed that compared with controls, oral MA as an add-on therapy was associated with significantly lower SCORAD scores (MD = -5.30, 95% CI -8.50, -1.55, p < 0.01, I2  = 81%). However, adverse events, pruritus scores, quality of life, and frequency of TCS use showed no significant difference in this meta-analysis study (p > 0.05).

CONCLUSIONS

This meta-analysis showed that MA plus TCS could be an effective and safe treatment for patients with AD to relieve relevant symptoms, which might be used as an add-on therapy in the treatment of AD. However, due to the limited number of studies, results should be interpreted with caution. Further studies with a larger sample size are needed to explore the optimal protocol of MA plus TCS.

Bacterial Metabolites: A Link between Gut Microbiota and Dermatological Diseases

Dysbiosis has been identified in many dermatological conditions (e.g., psoriasis, atopic dermatitis, systemic lupus erythematosus). One of the ways by which the microbiota affect homeostasis is through microbiota-derived molecules (metabolites). There are three main groups of metabolites: short-chain fatty acids (SCFAs), tryptophan metabolites, and amine derivatives including trimethylamine N-oxide (TMAO). Each group has its own uptake and specific receptors through which these metabolites can exert their systemic function. This review provides up-to-date knowledge about the impact that these groups of gut microbiota metabolites may have in dermatological conditions. Special attention is paid to the effect of microbial metabolites on the immune system, including changes in the profile of the immune cells and cytokine disbalance, which are characteristic of several dermatological diseases, especially psoriasis and atopic dermatitis. Targeting the production of microbiota metabolites may serve as a novel therapeutic approach in several immune-mediated dermatological diseases.

Intestinal epithelial cell-derived components regulate transcriptome of Lactobacillus rhamnosus GG

Introduction

Intestinal epithelial cells (IECs) provide the frontline responses to the gut microbiota for maintaining intestinal homeostasis. Our previous work revealed that IEC-derived components promote the beneficial effects of a commensal and probiotic bacterium, Lactobacillus rhamnosus GG (LGG). This study aimed to elucidate the regulatory effects of IEC-derived components on LGG at the molecular level.

Methods

Differential gene expression in LGG cultured with IEC-derived components at the timepoint between the exponential and stationary phase was studied by RNA sequencing and functional analysis.

Results

The transcriptomic profile of LGG cultured with IEC-derived components was significantly different from that of control LGG, with 231 genes were significantly upregulated and 235 genes significantly down regulated (FDR <0.05). The Clusters of Orthologous Groups (COGs) and Gene Ontology (GO) analysis demonstrated that the predominant genes enriched by IEC-derived components are involved in nutrient acquisition, including transporters for amino acids, metals, and sugars, biosynthesis of amino acids, and in the biosynthesis of cell membrane and cell wall, including biosynthesis of fatty acid and lipoteichoic acid. In addition, genes associated with cell division and translation are upregulated by IEC-derived components. The outcome of the increased transcription of these genes is supported by the result that IEC-derived components significantly promoted LGG growth. The main repressed genes are associated with the metabolism of amino acids, purines, carbohydrates, glycerophospholipid, and transcription, which may reflect regulation of metabolic mechanisms in response to the availability of nutrients in bacteria.

Discussion

These results provide mechanistic insight into the interactions between the gut microbiota and the host.