The coronavirus disease 2019 (COVID-19) pandemic has caused health issues worldwide. Studies have suggested that modulation of the gut microbiota could attenuate the severity of COVID-19 symptoms. In light of this, we explored the effects of the prebiotic dietary fibre partially hydrolyzed guar gum (PHGG) on SARS-CoV-2 infection in a Syrian hamster model, hypothesizing that modulation of the gut microbiome and intestinal metabolites through PHGG administration would improve COVID-19 disease outcomes. Eight hamsters each were assigned to the PHGG administration and control groups. The PHGG group was given a diet supplemented with 5% PHGG for two weeks. Consequently, PHGG improved the host survival rate to 100% compared to 25% of the control group (P = 0.003) and attenuated morbid weight loss. Another non-infected set of hamsters was used for the analysis of the gut microbiome composition with 16S rRNA amplicon sequencing, serum, and faecal metabolites with GC–MS and LC–MS. PHGG altered the gut microbiome composition and increased the relative abundances of Ileibacterium, Bifidobacterium, and Prevotella. Furthermore, it elevated the concentrations of faecal valeric acid, propionic acid, ursodeoxycholic acid, and serum deoxycholic acid. Taken together, our data suggest that the prebiotic PHGG modulates gut metabolites and has the potential to reduce COVID-19 morbidity.

Oral supplementation with probiotics, prebiotics, and synbiotics is a novel potential complementary therapy for addressing overweight and obesity through gut microbiota modulation. This systematic review provides a comprehensive summary of the existing evidence to guide future research. Literature searches were conducted in four databases to identify human trials published until May 2024 that examined the impact of probiotic, prebiotic, or synbiotic interventions on faecal microbiota composition changes in overweight and obese participants from Latin American and Caribbean populations (LACPs). Of the 13,090 identified records, five randomised controlled trials (RCTs) from Brazil, Mexico, and Chile met the inclusion criteria for this review. The included RCTs evaluated different forms of therapies over short-term interventions (6 or 8 weeks), with sample sizes ranging from 21 to 39 participants across the studies. Variations in the reported outcomes were observed due to differences in supplement formulation, dosage, population characteristics, and methodological heterogeneity. The findings indicate that the available data are inadequate to establish definitive conclusions regarding the impact of biotic treatments on gut microbiota profiles in LACP. Further research with larger sample sizes and precise microbiota analysis is required to elucidate the implications of dietary interventions on gut microbiota in obesity and related disorders.

There has been a growing recognition of the significant role played by the human gut microbiota in altering the bioavailability as well as the pharmacokinetic and pharmacodynamic aspects of orally ingested xenobiotic and biotic molecules. The determination of species-specific contributions to the metabolism of biotic and xenobiotic molecules has the potential to aid in the development of new therapeutic and nutraceutical molecules that can modulate human gut microbiota. Here we present “GutBugDB,” an open-access digital repository that provides information on potential gut microbiome-mediated biotransformation of biotic and xenobiotic molecules using the predictions from the GutBug tool. This database is constructed using metabolic proteins from 690 gut bacterial genomes and 363,872 protein enzymes assigned with their EC numbers (with representative Expasy ID and domains present). It provides information on gut microbiome enzyme-mediated metabolic biotransformation for 1439 FDA-approved drugs and nutraceuticals. GutBugDB is publicly available at https://metabiosys.iiserb.ac.in/gutbugdb/.

This study explored the effects of different human milk oligosaccharides (HMOs), solely and in combination, on gut microbiota composition and metabolic activity (organic acid production), using anaerobic in vitro batch culture fermenters. The aim was to compare prebiotic effects of HMOs (2’FL, 3’FL, 3’SL, 6’SL, LNT, LNnT, and 1:1 ratio mixes of 2’FL/3’SL and 3’SL/LNT) in faecal samples from irritable bowel syndrome (IBS) donors and healthy controls, and to determine the best-performing HMO in IBS. Fluorescent in situ hybridisation coupled with flow cytometry was utilised to study microbiota changes in major colonic genera, and organic acid production was assessed by gas chromatography. IBS donors had different starting microbial profiles compared to healthy controls and lower levels of organic acids. In response to HMOs, there were alterations in both the control and IBS faecal microbiomes. In IBS donor fermenters, Bifidobacterium, Faecalibacterium, total bacterial numbers, and organic acid production significantly increased post-HMO intervention. When comparing the effect of HMO interventions on the microbiota and organic acid production, a mix of 3’SL/LNT HMOs may be the most promising intervention for IBS patients.

Intestinal transit time has been recognized as an important factor in shaping the gut microbiota, although causality remains to be firmly demonstrated. The aim of this study was to evaluate the effect of different loperamide doses on the mouse intestinal transit time and to investigate the effects of increasing transit time on the gut microbial community. Loperamide significantly increased the transit time in a dose-dependent manner. Additionally, we observed a significant difference between the control group and the loperamide-treated groups in the abundance of the bacterial families Bacteroidaceae, Erysipelotrichaceae, Porphyromonadaceae, and Akkermansiaceae after 7 days of loperamide treatment, with the bacterial families responding to the increased transit time at different rates. Fermentation of faeces obtained from the same mice, with or without loperamide, demonstrated that the observed effects on gut microbiota in vivo were not a result of direct interactions between loperamide and the gut microbiota but rather a consequence of loperamide-induced increased intestinal transit time. In the cecum of the mice, we found higher levels of propionate in the high-dose group compared to the control and low-dose groups. Collectively, our findings establish that an altered transit time is causal to changes in the composition and activity of the microbiome.

The use of antibiotics in fish and shrimp aquaculture all over the world was found to be only partially successful in preventing infectious diseases. However, their overuse has resulted in the contamination of closed aquatic ecosystems, reduced antibiotic resistance in organisms that fight infectious diseases, and compromised the effectiveness of various antibiotic medications in controlling diseases. Excessive use of antibiotics damages aquaculture species and impacts human health, also rendering the most potent antibiotics increasingly ineffective, with limited alternatives. Therefore, intensive research efforts have been made to replace antibiotics with other protocols and methods like vaccines, phage therapy, quorum quenching technology, probiotics, prebiotics, chicken egg yolk antibody (IgY), and plant therapy,” etc. Though all these methods have great potential, many of them are still in the experimental stage, except for fish vaccines. All these alternative technologies need to be carefully standardized and evaluated before implementation. In recent times, after realizing the importance of the gut microbiome community in maintaining the health of animals, efforts have been made to use the microbiome strains for the prevention of pathogenic bacterial and viral infections. Now it has been experimentally proven that animals should possess a healthy microbiome community in their gut tract to strengthen the immune system and prevent the entry of harmful pathogens. Investigations are now being carried out on the derivation of various bioactive compounds from the gut microbiome strains and their structural profile and functionality using the molecular tools of metagenomics and bioinformatics. Such newly discovered compounds from microbiomes can be used as potential alternatives to replace antibiotic drugs in the aquaculture industry. These alternatives are likely to emerge as breakthroughs in animal health management and farming, with effects on cost efficiency, species health, productivity, and yield enhancement. Therefore, introducing new micro-innovative technologies into an overall health management plan will be highly beneficial.

The Simulator of the Human Intestinal Microbial Ecosystem (SHIME) system was provided with baby feed for one week to stabilise the microbial community, followed by a 10-day period with baby feed and another 10-day period with adult feed. The study was conducted using sterilised and standardised feed formulations, which model dietary conditions in vitro. Following the transition from baby to adult feed, a significant reduction in the proportion of butyrate in comparison to total SCFA was found after transitioning to adult feed in both the transverse colon and distal colon bioreactors. Our findings suggest that abrupt early-life dietary changes from simple to complex carbohydrates as well as the exclusion of bovine milk proteins can transiently lower the ability of the microbiota to produce butyrate. The lack of additional microbial input leads to a delay or impairment of the adaptation to the modified feed composition. However, given the short treatment duration and sterilised feed composition, these findings should be interpreted within the limitations of this in vitro model. A reduction in butyrate concentration following the transition to adult feed may reflect a temporary shift in microbial metabolic activity rather than a long-term impact on energy extraction efficiency in vivo.

There is considerable data suggesting that the gut microbiota (GM) contributes to health and regulates host immunity and influences brain function, findings with implications for neurodegenerative diseases, such as Alzheimer’s Disease (AD).

In the present study, using three non-fat diets with different ratios of unsaturated ω-6/ω-3 fatty acids (FAs)(high or low), we analyzed how minor differences in diet can affect the microbiota of amyloid precursor protein/Presenilin 1 transgenic (APP/PS1 [TG]) mice, a mice model of AD, next, we studied how the levels of sex hormones may affect the GM. The data obtained show that sex hormones in males fed our standard diet (S) modified alpha and beta diversity, whereas no differences were observed in TG mice compared with wild-type mice. Moreover, there were significant differences in both alpha or beta diversity in mice fed with an H or L diet compared with an S diet.

In conclusion, our data indicate that the levels of sex hormones or differences in the ω-6/ω-3 FA ratio alter the GM more than expected. Thus, it is tantalizing to propose that low levels of ω-3 FAs in APP/PS1 mice fed an “H” diet may be responsible for modifying some bacterial genera, exacerbating the basal neuropathology in this AD model.

Dietary patterns enriched in fermentable fibre (such as inulin) and inorganic nitrate are linked to cardiovascular benefits, possibly mediated by gut microbiota-derived bioactive compounds including short-chain fatty acids (SCFAs) and nitric oxide (NO). However, the potential synergistic effects remain unclear. We conducted a randomised, double-blind, crossover study to investigate the acute effects of inulin (15 g; INU), nitrate (400 mg; NO3−), and their combination (INU + NO3−) on plasma nitrate and nitrite levels, SCFAs, and blood pressure (BP) in 20 adults. Plasma nitrate and nitrite were significantly elevated following INU + NO3− and NO3− compared to INU (p < 0.001). Plasma SCFAs were increased after INU + NO3− and INU, but the incremental AUC was not statistically significant, likely due to large inter-individual variability. No significant main effects were observed on BP; however, inverse correlations were identified between peak plasma nitrite and diastolic BP (rs = −0.61, p = 0.004) and mean arterial pressure (MAP) (rs = −0.59, p = 0.005) following INU + NO3−. Peak nitrate concentrations were inversely correlated with diastolic BP following NO3− (rs = −0.47, p = 0.004). Co-supplementation with inulin and nitrate did not enhance plasma nitrate/nitrite or BP beyond nitrate alone but modulated SCFA profiles, suggesting potential interactions between fibre fermentation and nitrate metabolism for cardiovascular health.

The endocannabinoidome (eCBome) and the gut microbiota have been implicated in diet-induced obesity and impaired metabolism. While the eCBome and the gut microbiome are known to respond to diet macronutrient composition, interaction with micronutrient intake has been relatively unexplored. Iron (Fe) is an essential micronutrient for the function of enzymes involved in energy and lipid metabolism. Here, we evaluated how 28 days of Fe depletion and enrichment, in interaction with Low Fat-Low Sucrose (LFLS) or High Fat-High Sucrose (HFHS) diets, affect the host via the eCBome, and modulate intestinal gut microbial communities. Circulating levels of N-oleoyl-ethanolamine (OEA) showed an elevation associated with Fe-enriched LFLS diet, while the Fe-depleted HFHS diet showed an elevation of N-arachidonoyl-ethanolamine (anandamide, AEA) and a decrease of circulating linoleic acid. In parallel, the response of intestinal inflammatory mediators to Fe in the diet showed decreased levels of prostaglandins PGE1, PGE3, and 1a,1b-dihomo PGF2α in the caecum. Individual differences in microbial taxa were less pronounced in the ileum than in the caecum, where Eubacterium coprostanoligenes group showed an increase in relative abundance associated with Fe-depleted LFLS diets. In conclusion, our study shows that Fe intake modulates the response to the macronutrient composition of the diet in mice.

Microbial dysbiosis has been linked to environmental enteropathy (EE) and alterations in nutrient absorption; however, compositional modifications following exposure to supplementary nutrients are poorly understood. Here, we report the effect of amino acid and micronutrient supplementation on the gut microbiome of adults with EE.

In the AMAZE trial, adults with EE were randomized to amino acids (AA) and/or micronutrients (MM) for 16 weeks in a 2 × 2 factorial design against placebo. Endoscopy was performed before and after intervention, during which duodenal aspirates were collected as well as fecal samples. 16S rRNA amplicon sequencing was performed on both these samples, and differences in bacterial community composition before and after interventions were investigated using differential abundance analysis, corrected using false discovery rate, plus alpha and beta diversity measurements.

HIV seropositive participants exhibited lower alpha and beta diversity at baseline. AA and/or MM supplementation did not show significant changes in abundance or diversity of genera post-intervention compared to placebo. Micronutrient supplementation resulted in an increase in the pyruvate fermentation to acetone MetaCyc pathways compared to the placebo arm.

This study provides insights into the responsiveness of the gut microbiome to micronutrient and amino acid supplementation in adults with EE.

Decreased gut microbial diversity is associated with greater depression symptoms in adults. Findings on the relationship between the gut microbiome and depression or anxiety in children and adolescents are mixed, and evidence syntheses are needed. Seven databases were searched for peer-reviewed studies on the gut microbiome and internalizing symptoms, depression, or anxiety, in children and adolescents (<19 years). Random-effects meta-analyses of alpha diversity indices were performed. Youth advisors validated the research findings’ relevance to their experiences and contributed to dissemination planning. Eight studies were included, representing 2,865 participants (mean age = 11.4 years, SD = 4.3). Study designs were cross-sectional (n = 5), longitudinal (n = 2), and interventional (n = 1). No association was found between alpha or beta diversity and internalizing problems, depression, or anxiety. Increased abundance of genera within phyla Bacillota (e.g., Fusicatenibacter) and Pseudomonadota (e.g., Escherichia), along with decreased abundance of other Bacillota genera (e.g., Faecalibacterium), were associated with depression and anxiety symptoms. This review identified preliminary associations between specific bacterial taxa and depression and anxiety in children and adolescents. Larger studies using comprehensive analytical approaches are needed to explore the role of the gut microbiome in the genesis and treatment of internalizing disorders.

Non-nutritive sweeteners (NNSs) are popular sugar substitutes, valued for their potential to reduce caloric intake and associated health risks. However, their long-term effects on the human gut microbiome remain debatable. This study investigates the impact of tagatose, allulose, Rebaudioside-A (Reb-A), and saccharin on quorum-sensing (QS)-regulated phenotypes and gene expression in QS biosensor model bacteria. It sheds light on their potential influence on the gut microbiome. Our study revealed diverse effects among the NNSs. Tagatose and allulose demonstrated QS phenotypic inhibition in Chromobacterium violaceum (≈50%) and Pseudomonas aeruginosa (20–50%) in a concentration-dependent manner. Additionally, tagatose and allulose decreased the P. aeruginosa lasI gene expression. Reb-A and saccharin presented a significant, however less prominent, phenotypic inhibition on C. violaceum (25–30%) and P. aeruginosa swarming motility (≈20%). Both NNSs decreased the expression of the lasI gene of P. aeruginosa. Molecular docking of QS regulatory proteins showed that saccharin and Reb-A have significantly higher binding affinity compared to allulose and tagatose, relative to native inducers. These results suggest the complex interactions mediated by NNSs in QS regulatory pathways. These findings provide valuable insights into the varied, species and dose-dependent effects of NNS on microbial communication, suggesting potential implications for the gut microbiome.

Lacticaseibacillus rhamnosus may modulate stress-induced anxiety, yet animal evidence has not been systematically evaluated. Following PRISMA guidelines, PubMed, Embase, and Scopus were searched (2011–2024) for animal studies evaluating the role of L. rhamnosus in stress-induced anxiety. Primary outcomes were behavioural anxiety measures; secondary outcomes included neuroendocrine, immune, epithelial, and microbiota changes. Fifteen studies met the inclusion criteria. Species included mice (n=7), rats (n=5), and hens (n=3). Stress models comprised chronic unpredictable mild stress (n=8), social defeat (n=2), maternal separation (n=1), restraint stress (n=1), and severe feather-pecking (n=3). Common strains were JB-1 (n=8), HN001 (n=2), LGG (n=2), LR-32 (n=1), 4B15 (n=1), and LR3201 (n=1). Of the 15 studies, 12 reported significant anxiolytic effects, most frequently in the elevated plus maze (7/10) and open-field test (6/9). JB-1 showed the most consistent behavioural improvement (7/8 studies). Mechanistic findings were reported in subsets of studies: HPA axis modulation in 4/15, monoamine changes in 4/15, GABAergic effects in 4/15, immune/anti-inflammatory changes in 4/15, tight junction restoration in 2/15, and gut microbiota or SCFA-related changes in 7/15. L. rhamnosus, particularly strain JB-1, shows consistent anxiolytic effects and multiple putative mechanistic pathways, though more rigorous and standardised preclinical designs are needed.