Geographical separation and ethnic origin influence the human gut microbial composition: a meta-analysis from a Malaysian perspective

The impact of intermittent fasting on gut microbiota: a systematic review of human studies

Background

Intermittent fasting (IF) has gained popularity in interventions targeting overweight, obesity and metabolic syndrome. IF may affect the gut microbiome composition and therefore have various effects on gut microbiome mediated functions in humans. Research on the effects of IF on human gut microbiome is limited. Therefore, the objective of this systematic review was to determine how different types of IF affect the human gut microbiome.

Methods

A literature search was conducted for studies investigating the association of different types of IF and gut microbiota richness, alpha and beta diversity, and composition in human subjects. Databases included Cochrane Library (RRID:SCR_013000), PubMed (RRID:SCR_004846), Scopus (RRID:SCR_022559) and Web of Science (RRID:SCR_022706). A total of 1,332 studies were retrieved, of which 940 remained after removing duplicates. Ultimately, a total of 8 studies were included in the review. The included studies were randomized controlled trials, quasi-experimental studies and pilot studies implementing an IF intervention (time-restricted eating, alternate day fasting or 5:2 diet) in healthy subjects or subjects with any disease.

Results

Most studies found an association between IF and gut microbiota richness, diversity and compositional changes. There was heterogeneity in the results, and bacteria which were found to be statistically significantly affected by IF varied widely depending on the study.

Conclusion

The findings in this systematic review suggest that IF influences gut microbiota. It seems possible that IF can improve richness and alpha diversity. Due to the substantial heterogeneity of the results, more research is required to validate these findings and clarify whether the compositional changes might be beneficial to human health.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021241619.

Integrating clinical and cross-cohort metagenomic features: a stable and non-invasive colorectal cancer and adenoma diagnostic model

Background: Dysbiosis is associated with colorectal cancer (CRC) and adenomas (CRA). However, the robustness of diagnostic models based on microbial signatures in multiple cohorts remains unsatisfactory. Materials and Methods: In this study, we used machine learning models to screen metagenomic signatures from the respective cross-cohort datasets of CRC and CRA (selected from CuratedMetagenomicData, each disease included 4 datasets). Then select a CRC and CRA data set from the CuratedMetagenomicData database and meet the requirements of having both metagenomic data and clinical data. This data set will be used to verify the inference that integrating clinical features can improve the performance of microbial disease prediction models. Results: After repeated verification, we selected 20 metagenomic features that performed well and were stably expressed within cross-cohorts to represent the diagnostic role of bacterial communities in CRC/CRA. The performance of the selected cross-cohort metagenomic features was stable for multi-regional and multi-ethnic populations (CRC, AUC: 0.817-0.867; CRA, AUC: 0.766-0.833). After clinical feature combination, AUC of our integrated CRC diagnostic model reached 0.939 (95% CI: 0.932-0.947, NRI=30%), and that of the CRA integrated model reached 0.925 (95%CI: 0.917-0.935, NRI=18%). Conclusion: In conclusion, the integrated model performed significantly better than single microbiome or clinical feature models in all cohorts. Integrating cross-cohort common discriminative microbial features with clinical features could help construct stable diagnostic models for early non-invasive screening for CRC and CRA.

Can prebiotics help tackle the childhood obesity epidemic?

Globally, excess weight during childhood and adolescence has become a public health crisis with limited treatment options. Emerging evidence suggesting the involvement of gut microbial dysbiosis in obesity instills hope that targeting the gut microbiota could help prevent or treat obesity. In pre-clinical models and adults, prebiotic consumption has been shown to reduce adiposity partially via restoring symbiosis. However, there is a dearth of clinical research into its potential metabolic benefits in the pediatric population. Here, we provide a succinct overview of the common characteristics of the gut microbiota in childhood obesity and mechanisms of action of prebiotics conferring metabolic benefits. We then summarize available clinical trials in children with overweight or obesity investigating the effects of prebiotics on weight management. This review highlights several controversial aspects in the microbiota-dependent mechanisms by which prebiotics are thought to affect host metabolism that warrant future investigation in order to design efficacious interventions for pediatric obesity.

Gut Microbiota Composition in the First and Third Trimester of Pregnancy among Malay Women is Associated with Body Mass Index: A Pilot Study

Background

This study has analysed the pattern of gut microbiota during the first and third trimesters among pregnant Malay women.

Methods

This was a pilot prospective observational study involving 12 pregnant Malay women without any endocrine disorders and on neither antibiotics nor probiotics. Demographic details and anthropometric measurements were obtained, and the faecal 16S ribosomal ribonucleic acid (rRNA) metagenome microbiota of the first and third trimesters (T1 and T3) were analysed. Univariate and multivariate statistics, partial least squares discriminant analysis (PLSDA) and Kendall rank correlation testing were used to identify key genera and associations with pregnancy trimester and body mass index (BMI).

Results

The most abundant phyla were Bacteroidetes, Firmicutes, Proteobacteria and Actinobacteria, with significant differences in composition at the genus level demonstrated between T1 and T3. Sequencing showed a statistically significant difference in beta diversity between normal and abnormal BMI at all taxonomic ranks (R ² = 0.60; Q ² = 0.23) and genus levels (R ² = 0.57; Q ² = 0.37). The relative abundances of Akkermansia (P < 0.05; false discovery rate [FDR] < 0.05), Olsenella (P < 0.05; FDR < 0.05) and Oscillospira (P < 0.05; FDR < 0.05) were found to be significantly higher in normal BMI cases by 2.4, 3.4 and 3.1 times, respectively.

Conclusion

Three genera (Akkermansia, Olsenella and Oscillospira) were correlated with normal BMI during pregnancy. All three could be promising biotherapeutic targets in body weight regulation during pregnancy, subsequently reducing complications associated with higher BMI.

The fecal microbiotas of women of Pacific and New Zealand European ethnicities are characterized by distinctive enterotypes that reflect dietary intakes and fecal water content

Obesity is a complex, multifactorial condition that is an important risk factor for noncommunicable diseases including cardiovascular disease and type 2 diabetes. While prevention and management require a healthy and energy balanced diet and adequate physical activity, the taxonomic composition and functional attributes of the colonic microbiota may have a supplementary role in the development of obesity. The taxonomic composition and metabolic capacity of the fecal microbiota of 286 women, resident in Auckland New Zealand, was determined by metagenomic analysis. Associations with BMI (obese, nonobese), body fat composition, and ethnicity (Pacific, n = 125; NZ European women [NZE], n = 161) were assessed using regression analyses. The fecal microbiotas were characterized by the presence of three distinctive enterotypes, with enterotype 1 represented in both Pacific and NZE women (39 and 61%, respectively), enterotype 2 mainly in Pacific women (84 and 16%) and enterotype 3 mainly in NZE women (13 and 87%). Enterotype 1 was characterized mainly by the relative abundances of butyrate producing species, Eubacterium rectale and Faecalibacterium prausnitzii, enterotype 2 by the relative abundances of lactic acid producing species, Bifidobacterium adolescentis, Bifidobacterium bifidum, and Lactobacillus ruminis, and enterotype 3 by the relative abundances of Subdoligranulum sp., Akkermansia muciniphila, Ruminococcus bromii, and Methanobrevibacter smithii. Enterotypes were also associated with BMI, visceral fat %, and blood cholesterol. Habitual food group intake was estimated using a 5 day nonconsecutive estimated food record and a 30 day, 220 item semi-quantitative Food Frequency Questionnaire. Higher intake of 'egg' and 'dairy' products was associated with enterotype 3, whereas 'non-starchy vegetables', 'nuts and seeds' and 'plant-based fats' were positively associated with enterotype 1. In contrast, these same food groups were inversely associated with enterotype 2. Fecal water content, as a proxy for stool consistency/colonic transit time, was associated with microbiota taxonomic composition and gene pools reflective of particular bacterial biochemical pathways. The fecal microbiotas of women of Pacific and New Zealand European ethnicities are characterized by distinctive enterotypes, most likely due to differential dietary intake and fecal consistency/colonic transit time. These parameters need to be considered in future analyses of human fecal microbiotas.

Targeting the gut microbiota for cancer therapy

Growing evidence suggests that the gut microbiota modulates the efficacy and toxicity of cancer therapy, most notably immunotherapy and its immune-related adverse effects. The poor response to immunotherapy in patients treated with antibiotics supports this influential role of the microbiota. Until recently, results pertaining to the identification of the microbial species responsible for these effects were incongruent, and relatively few studies analysed the underlying mechanisms. A better understanding of the taxonomy of the species involved and of the mechanisms of action has since been achieved. Defined bacterial species have been shown to promote an improved response to immune-checkpoint inhibitors by producing different products or metabolites. However, a suppressive effect of Gram-negative bacteria may be dominant in some unresponsive patients. Machine learning approaches trained on the microbiota composition of patients can predict the ability of patients to respond to immunotherapy with some accuracy. Thus, interest in modulating the microbiota composition to improve patient responsiveness to therapy has been mounting. Clinical proof-of-concept studies have demonstrated that faecal microbiota transplantation or dietary interventions might be utilized clinically to improve the success rate of immunotherapy in patients with cancer. Here, we review recent advances and discuss emerging strategies for microbiota-based cancer therapies.

Progress in research on gut microbiota in ethnic minorities in China and consideration of intervention strategies based on ethnic medicine: A review

One of the variables affecting gut microbiota is ethnicity. There are 56 ethnic subgroups in China, and their intestinal flora differs. A wealth of medical resources has also been produced by the presence of numerous ethnic minorities. In this study, we reviewed the pertinent literature on the intestinal flora of ethnic minorities in China and abroad using the CiteSpace visualization software, and we used bibliometric techniques to find the most widely prescribed medications for preventing and treating endemic diseases in ethnic minorities. Based on the gut microbiology of minority populations, we suggest that by comprehensive development involving literature, experimental, and clinical research, the pharmacological action mechanisms for interventions in endemic diseases can be drawn from ethnic medicine. This point of view has not been discussed before and will offer a fresh perspective on the creation and application of ethnic medications as well as a fresh method for the management of prevalent diseases in ethnic communities.

The Functional Biogeography of eDNA Metacommunities in the Post-Fire Landscape of the Angeles National Forest

Wildfires have continued to increase in frequency and severity in Southern California due in part to climate change. To gain a further understanding of microbial soil communities’ response to fire and functions that may enhance post-wildfire resilience, soil fungal and bacterial microbiomes were studied from different wildfire areas in the Gold Creek Preserve within the Angeles National Forest using 16S, FITS, 18S, 12S, PITS, and COI amplicon sequencing. Sequencing datasets from December 2020 and June 2021 samplings were analyzed using QIIME2, ranacapa, stats, vcd, EZBioCloud, and mixomics. Significant differences were found among bacterial and fungal taxa associated with different fire areas in the Gold Creek Preserve. There was evidence of seasonal shifts in the alpha diversity of the bacterial communities. In the sparse partial least squares analysis, there were strong associations (r > 0.8) between longitude, elevation, and a defined cluster of Amplicon Sequence Variants (ASVs). The Chi-square test revealed differences in fungi−bacteria (F:B) proportions between different trails (p = 2 × 10−16). sPLS results focused on a cluster of Green Trail samples with high elevation and longitude. Analysis revealed the cluster included the post-fire pioneer fungi Pyronema and Tremella. Chlorellales algae and possibly pathogenic Fusarium sequences were elevated. Bacterivorous Corallococcus, which secretes antimicrobials, and bacterivorous flagellate Spumella were associated with the cluster. There was functional redundancy in clusters that were differently composed but shared similar ecological functions. These results implied a set of traits for post-fire resiliency. These included photo-autotrophy, mineralization of pyrolyzed organic matter and aromatic/oily compounds, potential pathogenicity and parasitism, antimicrobials, and N-metabolism.

Uterine Fibroid Patients Reveal Alterations in the Gut Microbiome

The gut microbiota is associated with reproductive disorders in multiple ways. This research investigated possible differences in gut microbiome compositions between patients with uterine fibroids (UFs) and healthy control subjects in order to further provide new insight into its etiology. Stool samples were collected from 85 participants, including 42 UF patients (case group) and 43 control subjects (control group). The gut microbiota was examined with 16S rRNA quantitative arrays and bioinformatics analysis. The α-diversity in patients with UFs was significantly lower than that of healthy controls and negatively correlated with the number of tumorigeneses. The microbial composition of the UF patients deviated from the cluster of healthy controls. Stool samples from patients with UFs exhibited significant alterations in terms of multiple bacterial phyla, such as Firmicutes, Proteobacteria, Actinobacteria, and Verrucomicrobia. In differential abundance analysis, some bacteria species were shown to be downregulated (e.g., Bifidobacteria scardovii, Ligilactobacillus saerimneri, and Lactococcus raffinolactis) and upregulated (e.g., Pseudomonas stutzeri and Prevotella amnii). Furthermore, the microbial interactions and networks in UFs exhibited lower connectivity and complexity as well as higher clustering property compared to the controls. Taken together, it is possible that gut microbiota dysbiosis has the potential as a risk factor. This study found that UFs are associated with alterations of the gut microbiome diversity and community network connectivity. It provides a new direction to further explore the host–gut microbiota interplay and to develop management and prevention in UF pathogenesis.

Gut Microbiome Succession in Chinese Mitten Crab Eriocheir sinensis During Seawater-Freshwater Migration

Biological migration is usually associated with disturbances and environmental changes that are key drivers in determining the diversity, community compositions, and function of gut microbiome. However, little is known about how gut microbiome is affected by disturbance such as salinity changes during migration from seawater to freshwater. Here, we tracked the gut microbiome succession of Chinese mitten crabs (Eriocheir sinensis) during their migrations from seawater to freshwater and afterward using 16S rDNA sequencing for 127 days, and explored the temporal patterns in microbial diversity and the underlying environmental factors. The species richness of gut microbiome showed a hump-shaped trend over time during seawater–freshwater migration. The community dissimilarities of gut microbiome increased significantly with day change. The turnover rate of gut microbiome community was higher during seawater–freshwater transition (1–5 days) than that in later freshwater conditions. Salinity was the major factor leading to the alpha diversity and community dissimilarity of gut microbiome during seawater–freshwater transition, while the host selection showed dominant effects during freshwater stage. The transitivity, connectivity, and average clustering coefficient of gut microbial co-occurrence networks showed decreased trends, while modularity increased during seawater–freshwater migration. For metabolic pathways, “Amino Acid Metabolism” and “Lipid Metabolism” were higher during seawater–freshwater transition than in freshwater. This study advances our mechanistic understanding of the assembly and succession of gut microbiota, which provides new insights into the gut ecology of other aquatic animals.