Effects of Hydrogen Sulfide on the Microbiome: From Toxicity to Therapy

Exploring gut microbial metabolites as key players in inhibition of cancer progression: Mechanisms and therapeutic implications

The gut microbiota plays a critical role in numerous biochemical processes essential for human health, such as metabolic regulation and immune system modulation. An increasing number of research suggests a strong association between the gut microbiota and carcinogenesis. The diverse metabolites produced by gut microbiota can modulate cellular gene expression, cell cycle dynamics, apoptosis, and immune system functions, thereby exerting a profound influence on cancer development and progression. A healthy gut microbiota promotes substance metabolism, stimulates immune responses, and thereby maintains the long-term homeostasis of the intestinal microenvironment. When the gut microbiota becomes imbalanced and disrupts the homeostasis of the intestinal microenvironment, the risk of various diseases increases. This review aims to elucidate the impact of gut microbial metabolites on cancer initiation and progression, focusing on short-chain fatty acids (SCFAs), polyamines (PAs), hydrogen sulfide (H2S), secondary bile acids (SBAs), and microbial tryptophan catabolites (MTCs). By detailing the roles and molecular mechanisms of these metabolites in cancer pathogenesis and therapy, this article sheds light on dual effects on the host at different concentrations of metabolites and offers new insights into cancer research.

An exploratory study investigating the impact of the bladder tumor microbiome on Bacillus Calmette Guerin (BCG) response in non-muscle invasive bladder cancer

PURPOSE

Intravesical Bacillus Calmette-Guerin (BCG) is standard of care for intermediate- and high-risk non-muscle invasive bladder cancer (NMIBC). The effect of the bladder microbiome on response to BCG is unclear. We sought to characterize the microbiome of bladder tumors in BCG-responders and non-responders and identify potential mechanisms that drive treatment response.

MATERIALS AND METHODS

Patients with archival pre-treatment biopsy samples (2012-2018) were identified retrospectively. Prospectively, urine and fresh tumor samples were collected from individuals with high-risk NMIBC (2020-2023). BCG response was defined as tumor-free 2 years from induction therapy. Extracted DNA was sequenced for 16S rRNA and shotgun metagenomics. Primary outcomes were species richness (α-diversity) and microbial composition (β-diversity). Paired t-tests were performed for α-diversity (Observed species/Margalef). Statistical analysis for β-diversity (weighted and unweighted UniFrac distances, weighted Bray-Curtis dissimilarity) were conducted through Permanova, with 999 permutations.

RESULTS

Microbial species richness (P < 0.001) and composition (P = 0.001) differed between BCG responders and non-responders. Lactobacillus spp. were significantly enriched in BCG-responders. Shotgun metagenomics identified possible mechanistic pathways such as assimilatory sulfate reduction.

CONCLUSION

A compositional difference exists in the tumor microbiome of BCG responders and non-responders with Lactobacillus having increased abundance in BCG responders.

Gulf War Illness Is Associated with Host Gut Microbiome Dysbiosis and Is Linked to Altered Species Abundance in Veterans from the BBRAIN Cohort

Gulf War Illness (GWI) is a debilitating condition marked by chronic fatigue, cognitive problems, pain, and gastrointestinal (GI) complaints in veterans who were deployed to the 1990-1991 Gulf War. Fatigue, GI complaints, and other chronic symptoms continue to persist more than 30 years post-deployment. Several potential mechanisms for the persistent illness have been identified and our prior pilot study linked an altered gut microbiome with the disorder. This study further validates and builds on our prior preliminary findings of host gut microbiome dysbiosis in veterans with GWI. Using stool samples and Multidimensional Fatigue Inventory (MFI) data from 89 GW veteran participants (63 GWI cases and 26 controls) from the Boston biorepository, recruitment, and integrative network (BBRAIN) for Gulf War Illness, we found that the host gut bacterial signature of veterans with GWI showed significantly different Bray-Curtis beta diversity than control veterans. Specifically, a higher Firmicutes to Bacteroidetes ratio, decrease in Akkermansia sp., Bacteroides thetaiotamicron, Bacteroides fragilis, and Lachnospiraceae genera and increase in Blautia, Streptococcus, Klebsiella, and Clostridium genera, that are associated with gut, immune, and brain health, were shown. Further, using MaAsLin and Boruta algorithms, Coprococcus and Eisenbergiella were identified as important predictors of GWI with an area under the curve ROC predictive value of 74.8%. Higher self-reported MFI scores in veterans with GWI were also significantly associated with an altered gut bacterial diversity and species abundance of Lachnospiraceae and Blautia. These results suggest potential therapeutic targets for veterans with GWI that target the gut microbiome and specific symptoms of the illness.

The role of fiber in modulating plant protein-induced metabolic responses

The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

Gas Therapy: Generating, Delivery, and Biomedical Applications

Oxygen (O2), nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S), and hydrogen (H2) with direct effects, and carbon dioxide (CO2) with complementary effects on the condition of various diseases are known as therapeutic gases. The targeted delivery and in situ generation of these therapeutic gases with controllable release at the site of disease has attracted attention to avoid the risk of gas poisoning and improve their performance in treating various diseases such as cancer therapy, cardiovascular therapy, bone tissue engineering, and wound healing. Stimuli-responsive gas-generating sources and delivery systems based on biomaterials that enable on-demand and controllable release are promising approaches for precise gas therapy. This work highlights current advances in the design and development of new approaches and systems to generate and deliver therapeutic gases at the site of disease with on-demand release behavior. The performance of the delivered gases in various biomedical applications is then discussed.

Magnesium Oxide Reduces Anxiety-like Behavior in Mice by Inhibiting Sulfate-Reducing Bacteria

The gut microbiota-brain axis allows for bidirectional communication between the microbes in our gastrointestinal (GI) tract and the central nervous system. Psychological stress has been known to disrupt the gut microbiome (dysbiosis) leading to anxiety-like behavior. Pathogens administered into the gut have been reported to cause anxiety. Whether commensal bacteria affect the gut-brain axis is not well understood. In this study, we examined the impact of a commensal sulfate-reducing bacteria (SRB) and its metabolite, hydrogen sulfide (H2S), on anxiety-like behavior. We found that mice gavaged with SRB had increased anxiety-like behavior as measured by the open field test. We also tested the effects of magnesium oxide (MgO) on SRB growth both in vitro and in vivo using a water avoidance stress (WAS) model. We found that MgO inhibited SRB growth and H2S production in a dose-dependent fashion. Mice that underwent psychological stress using the WAS model were observed to have an overgrowth (bloom) of SRB (Deferribacterota) and increased anxiety-like behavior. However, WAS-induced overgrowth of SRB and anxiety-like behavioral effects were attenuated in animals fed a MgO-enriched diet. These findings supported a potential MgO-reversible relationship between WAS-induced SRB blooms and anxiety-like behavior.

Gut microbiota from patients with Parkinson's disease causes motor deficits in honeybees

Objective

Parkinson's disease (PD) is possibly caused by genetic factors, environmental factors, and gut microbiota dysbiosis. This study aims to explore whether the microbiota contributes to the behavior abnormalities of PD.

Methods

We transplanted gut microbiota from patients with PD or healthy controls (HC) into microbiota-free honeybees. We also established two more groups, namely the rotenone (ROT) group, in which PD-like symptoms of honeybees were induced by rotenone, and the conventional (CV) group, in which honeybees were colonized with conventional gut microbiota. The climbing assay was performed to assess the motor capabilities of honeybees. Histopathological examination was conducted to evaluate the integrity of gut mucosa. Tyrosine hydroxylase (TH) gene expression levels and dopamine (DA) concentrations in the brain were also examined. Additionally, metagenomics and full-length 16S rRNA analyses were performed to identify alterations in gut microbiota profiles, both in PD patients and honeybees.

Results

Honeybees in the PD and ROT groups exhibited slower climbing speeds, downregulated TH gene expression, and impaired gut barriers. Both the HC and PD groups of honeybees successfully harbored a portion of gut microbiota from corresponding human donors, and differences in microbial composition were identified. Morganella morganii and Erysipelatoclostridium ramosum exhibited significantly increased relative abundance in the HC group, while Dorea longicatena, Collinsella aerofaciens, Lactococcus garvieae, Holdemanella biformis, Gemmiger formicilis, and Blautia obeum showed significantly increased relative abundance in the PD group. Functional predictions of microbial communities in the PD group indicated an increased synthesis of hydrogen sulfide and methane.

Conclusion

A novel PD model was induced in honeybees with rotenone and gut microbiota from PD patients. This study linked PD-related behaviors to altered gut microbiota, highlighting a potential gut microbiota-brain axis involvement in PD pathogenesis. We identify previously unrecognized associations of Dorea longicatena, Collinsella aerofaciens, Lactococcus garvieae, Holdemanella biformis, Gemmiger formicilis, and Blautia obeum with PD. Additionally, pathways related to hydrogen sulfide and methane synthesis have been previously suggested as potential contributors to the development of PD, and our research further supports this hypothesis.

Effect of Probiotic Bacteria on the Gut Microbiome of Mice with Lipopolysaccharide-Induced Inflammation

The role of lipopolysaccharide (LPS) in the development of diseases is clear, but the specific mechanisms remain poorly understood. This study aimed to investigate the microbiome aberrations in the guts of mice against the background of LPS, as well as the anti-inflammatory effect of probiotic supplementation with Lactobacillus plantarum from the gut, a mix of commercial probiotic lactic acid bacteria, and Weissella confusa isolated from milk using next-generation sequencing. LPS injections were found to induce inflammatory changes in the intestinal mucosa. These morphological changes were accompanied by a shift in the microbiota. We found no significant changes in the microbiome with probiotic supplementation compared to the LPS group. However, when Lactobacillus plantarum and a mix of commercial probiotic lactic acid bacteria were used, the intestinal mucosa was restored. Weissella confusa did not contribute to the morphological changes of the intestinal wall or the microbiome. Changes in the microbiome were observed with probiotic supplementation of Lactobacillus plantarum and a mix of commercial probiotic lactic acid bacteria compared to the control group. In addition, when Lactobacillus plantarum was used, we observed a decrease in the enrichment of the homocysteine and cysteine interconversion pathways with an increase in the L-histidine degradation pathway.

Exploring the Relationship Between Diet, Lifestyle and Gut Microbiome in Colorectal Cancer Development: A Recent Update

Colorectal cancer (CRC) is one of the major causes of cancer-related mortality worldwide. Despite advances in treatment modalities, its prevalence continues to rise, notably among younger populations. Unhealthy dietary habits, sedentary routines, and obesity have been identified as one of the key contributors to the development of colorectal cancer, apart from genetic and epigenetic modifications. Recognizing the profound impact of diet and lifestyle on the intricate gut microbiota ecosystem offers a promising avenue for understanding CRC development and its treatment. Gut dysbiosis, characterized by imbalances favoring harmful microbes over beneficial ones, has emerged as a defining feature of CRC. Changes in diet and lifestyle can profoundly alter the composition of gut microbes and the metabolites they produce, potentially contributing to CRC onset. Focusing on recent evidence, this review discussed various dietary factors, such as high consumption of red and processed meats and low fiber intake, and lifestyle factors, including obesity, lack of physical activity, smoking, and excessive alcohol consumption, that influence the gut microbiome composition and elevate CRC risk.

Fluorescent small molecule donors

Small molecule donors (SMDs) play subtle roles in the signaling mechanism and disease treatments. While many excellent SMDs have been developed, dosage control, targeted delivery, spatiotemporal feedback, as well as the efficiency evaluation of small molecules are still key challenges. Accordingly, fluorescent small molecule donors (FSMDs) have emerged to meet these challenges. FSMDs enable controllable release and non-invasive real-time monitoring, providing significant advantages for drug development and clinical diagnosis. Integration of FSMDs with chemotherapeutic, photodynamic or photothermal properties can take full advantage of each mode to enhance therapeutic efficacy. Given the remarkable properties and the thriving development of FSMDs, we believe a review is needed to summarize the design, triggering strategies and tracking mechanisms of FSMDs. With this review, we compiled FSMDs for most small molecules (nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, reactive oxygen species and formaldehyde), and discuss recent progress concerning their molecular design, structural classification, mechanisms of generation, triggered release, structure-activity relationships, and the fluorescence response mechanism. Firstly, from the large number of fluorescent small molecular donors available, we have organized the common structures for producing different types of small molecules, providing a general strategy for the development of FSMDs. Secondly, we have classified FSMDs in terms of the respective donor types and fluorophore structures. Thirdly, we discuss the mechanisms and factors associated with the controlled release of small molecules and the regulation of the fluorescence responses, from which universal guidelines for optical properties and structure rearrangement were established, mainly involving light-controlled, enzyme-activated, reactive oxygen species-triggered, biothiol-triggered, single-electron reduction, click chemistry, and other triggering mechanisms. Fourthly, representative applications of FSMDs for trackable release, and evaluation monitoring, as well as for visible in vivo treatment are outlined, to illustrate the potential of FSMDs in drug screening and precision medicine. Finally, we discuss the opportunities and remaining challenges for the development of FSMDs for practical and clinical applications, which we anticipate will stimulate the attention of researchers in the diverse fields of chemistry, pharmacology, chemical biology and clinical chemistry. With this review, we hope to impart new understanding thereby enabling the rapid development of the next generation of FSMDs.

The influence of the gut-brain axis on anxiety and depression: A review of the literature on the use of probiotics

This review aims to argue how using probiotics can improve anxiety and depressive behaviour without adverse effects, also exploring the impact of postbiotics on it. Specifically, probiotics have drawn more attention as effective alternative treatments, considering the rising cost of antidepressant and anti-anxiety drugs and the high risk of side effects. Depression and anxiety disorders are among the most common mental illnesses in the world's population, characterised by low mood, poor general interest, and cognitive or motor dysfunction. Thus, this study analysed published literature on anxiety, depression, and probiotic supplementation from PubMed and Scopus, focusing on the last twenty years. This study focused on the effect of probiotics on mental health as they have drawn more attention because of their extensive clinical applications and positive impact on various diseases. Numerous studies have demonstrated how the gut microbiota might be critical for mood regulation and how probiotics can affect host health by regulating the gut-brain axis. By comparing the different works analysed, it was possible to identify a strategy by which they are selected and employed and, at the same time, to assess how the effect of probiotics can be optimised using postbiotics, an innovation to improve mental well-being in humans.

Impact of Reactive Sulfur Species on Entamoeba histolytica: Modulating Viability, Motility, and Biofilm Degradation Capacity

Reactive sulfur species (RSS) like hydrogen sulfide (H2S) and cysteine persulfide (Cys-SSH) emerged as key signaling molecules with diverse physiological roles in the body, depending on their concentration and the cellular environment. While it is known that H2S and Cys-SSH are produced by both colonocytes and by the gut microbiota through sulfur metabolism, it remains unknown how these RSS affect amebiasis caused by Entamoeba histolytica, a parasitic protozoan that can be present in the human gastrointestinal tract. This study investigates H2S and Cys-SSH's impact on E. histolytica physiology and explores potential therapeutic implications. Exposing trophozoites to the H2S donor, sodium sulfide (Na2S), or to Cys-SSH led to rapid cytotoxicity. A proteomic analysis of Cys-SSH-challenged trophozoites resulted in the identification of >500 S-sulfurated proteins, which are involved in diverse cellular processes. Functional assessments revealed inhibited protein synthesis, altered cytoskeletal dynamics, and reduced motility in trophozoites treated with Cys-SSH. Notably, cysteine proteases (CPs) were significantly inhibited by S-sulfuration, affecting their bacterial biofilm degradation capacity. Immunofluorescence microscopy confirmed alterations in actin dynamics, corroborating the proteomic findings. Thus, our study reveals how RSS perturbs critical cellular functions in E. histolytica, potentially influencing its pathogenicity and interactions within the gut microbiota. Understanding these molecular mechanisms offers novel insights into amebiasis pathogenesis and unveils potential therapeutic avenues targeting RSS-mediated modifications in parasitic infections.

Solobacterium moorei promotes the progression of adenomatous polyps by causing inflammation and disrupting the intestinal barrier

BACKGROUND

Adenomatous polyps (APs) with inflammation are risk factors for colorectal cancer. However, the role of inflammation-related gut microbiota in promoting the progression of APs is unknown.

METHODS

Sequencing of the 16S rRNA gene was conducted to identify characteristic bacteria in AP tissues and normal mucosa. Then, the roles of inflammation-related bacteria were clarified by Spearman correlation analysis. Furthermore, colorectal HT-29 cells, normal colon NCM460 cells, and azoxymethane-treated mice were used to investigate the effects of the characteristic bacteria on progression of APs.

RESULTS

The expression levels of inflammation-related markers (diamine oxidase, D-lactate, C-reactive protein, tumor necrosis factor-α, interleukin-6 and interleukin-1β) were increased, whereas the expression levels of anti-inflammatory factors (interleukin-4 and interleukin-10) were significantly decreased in AP patients as compared to healthy controls. Solobacterium moorei (S. moorei) was enriched in AP tissues and fecal samples, and significantly positively correlated with serum inflammation-related markers. In vitro, S. moorei preferentially attached to HT-29 cells and stimulated cell proliferation and production of pro-inflammatory factors. In vivo, the incidence of intestinal dysplasia was significantly increased in the S. moorei group. Gavage of mice with S. moorei upregulated production of pro-inflammatory factors, suppressed proliferation of CD4+ and CD8+cells, and disrupted the integrity of the intestinal barrier, thereby accelerating progression of APs.

CONCLUSIONS

S. moorei accelerated the progression of AP in mice via activation of the NF-κB signaling pathway, chronic low-grade inflammation, and intestinal barrier disruption. Targeted reduction of S. moorei presents a potential strategy to prevent the progression of APs.

Solobacterium moorei promotes the progression of adenomatous polyps by causing inflammation and disrupting the intestinal barrier

BACKGROUND

Adenomatous polyps (APs) with inflammation are risk factors for colorectal cancer. However, the role of inflammation-related gut microbiota in promoting the progression of APs is unknown.

METHODS

Sequencing of the 16S rRNA gene was conducted to identify characteristic bacteria in AP tissues and normal mucosa. Then, the roles of inflammation-related bacteria were clarified by Spearman correlation analysis. Furthermore, colorectal HT-29 cells, normal colon NCM460 cells, and azoxymethane-treated mice were used to investigate the effects of the characteristic bacteria on progression of APs.

RESULTS

The expression levels of inflammation-related markers (diamine oxidase, D-lactate, C-reactive protein, tumor necrosis factor-α, interleukin-6 and interleukin-1β) were increased, whereas the expression levels of anti-inflammatory factors (interleukin-4 and interleukin-10) were significantly decreased in AP patients as compared to healthy controls. Solobacterium moorei (S. moorei) was enriched in AP tissues and fecal samples, and significantly positively correlated with serum inflammation-related markers. In vitro, S. moorei preferentially attached to HT-29 cells and stimulated cell proliferation and production of pro-inflammatory factors. In vivo, the incidence of intestinal dysplasia was significantly increased in the S. moorei group. Gavage of mice with S. moorei upregulated production of pro-inflammatory factors, suppressed proliferation of CD4+ and CD8+cells, and disrupted the integrity of the intestinal barrier, thereby accelerating progression of APs.

CONCLUSIONS

S. moorei accelerated the progression of AP in mice via activation of the NF-κB signaling pathway, chronic low-grade inflammation, and intestinal barrier disruption. Targeted reduction of S. moorei presents a potential strategy to prevent the progression of APs.

Miniaturized Capsule System Toward Real-Time Electrochemical Detection of H2 S in the Gastrointestinal Tract

Hydrogen sulfide (H2 S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H2 S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H2 S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas-sensing ingestible capsule is developed to enable real-time, wireless amperometric measurement of H2 S in GI conditions. A gold (Au) three-electrode sensor is modified with a Nafion solid-polymer electrolyte (Nafion-Au) to enhance selectivity toward H2 S in humid environments. The Nafion-Au sensor-integrated capsule shows a linear current response in H2 S concentration ranging from 0.21 to 4.5 ppm (R2 = 0.954) with a normalized sensitivity of 12.4% ppm-1 when evaluated in a benchtop setting. The sensor proves highly selective toward H2 S in the presence of known interferent gases, such as hydrogen (H2 ), with a selectivity ratio of H2 S:H2 = 1340, as well as toward methane (CH4 ) and carbon dioxide (CO2 ). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold-based notification is investigated, showing potential for in vivo application. Thus, the developed H2 S capsule platform provides an analytical tool to uncover the complex biology-modulating effects of intraluminal H2 S.

Diallyl trisulfide inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung cancer via modulating gut microbiota and the PPARγ/NF-κB pathway

Smoking is the primary risk factor for developing lung cancer. Chemoprevention could be a promising strategy to reduce the incidence and mortality rates of lung cancer. Recently, we reported that A/J mice exposed to tobacco smoke carcinogens displayed the reshaping of gut microbiota. Additionally, garlic oil was found to effectively inhibit the carcinogenic effects of tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in lung tumorigenesis. Diallyl trisulfide (DATS), which is the predominant compound in garlic oil, exhibits various biological activities. To further explore the chemopreventive action and potential mechanism of DATS on lung tumorigenesis, we established a lung adenocarcinoma model in A/J mice stimulated by NNK. Subsequently, we employed multi-omics combined molecular biology technologies to clarify the mechanism. The results indicated that DATS significantly decreased the number of lung tumors in NNK induced A/J mice. Interestingly, we discovered that DATS could modulate gut microbiota, particularly increasing the abundance of F. rodentium, which has inhibitory effects on tumor growth. Mechanistically, DATS could activate the PPARγ pathway, leading to the negative regulation of the NF-κB signaling pathway and subsequent suppression of NF-κB-mediated inflammatory factors. Collectively, these findings provide support for DATS as a potential novel chemopreventive agent for tobacco carcinogen-induced lung cancer.

Engineered bacteria titrate hydrogen sulfide and induce concentration-dependent effects on the host in a gut microphysiological system

Hydrogen sulfide (H2S) is a gaseous microbial metabolite whose role in gut diseases is debated, with contradictory results stemming from experimental difficulties associated with accurate dosing and measuring H2S and the use of model systems that do not accurately represent the human gut environment. Here, we engineer Escherichia coli to titrate H2S across the physiological range in a gut microphysiological system (chip) supportive of the co-culture of microbes and host cells. The chip is engineered to maintain H2S gas tension and enables visualization of co-culture in real time with confocal microscopy. Engineered strains colonize the chip and are metabolically active for 2 days, during which they produce H2S across a 16-fold range and induce changes in host gene expression and metabolism in an H2S-concentration-dependent manner. These results validate a platform for studying the mechanisms underlying microbe-host interactions by enabling experiments that are infeasible with current animal and in vitro models.

Evolution of E. coli in a mouse model of inflammatory bowel disease leads to a disease-specific bacterial genotype and trade-offs with clinical relevance

Inflammatory bowel disease (IBD) is a persistent inflammatory condition that affects the gastrointestinal tract and presents significant challenges in its management and treatment. Despite the knowledge that within-host bacterial evolution occurs in the intestine, the disease has rarely been studied from an evolutionary perspective. In this study, we aimed to investigate the evolution of resident bacteria during intestinal inflammation and whether- and how disease-related bacterial genetic changes may present trade-offs with potential therapeutic importance. Here, we perform an in vivo evolution experiment of E. coli in a gnotobiotic mouse model of IBD, followed by multiomic analyses to identify disease-specific genetic and phenotypic changes in bacteria that evolved in an inflamed versus a non-inflamed control environment. Our results demonstrate distinct evolutionary changes in E. coli specific to inflammation, including a single nucleotide variant that independently reached high frequency in all inflamed mice. Using ex vivo fitness assays, we find that these changes are associated with a higher fitness in an inflamed environment compared to isolates derived from non-inflamed mice. Further, using large-scale phenotypic assays, we show that bacterial adaptation to inflammation results in clinically relevant phenotypes, which intriguingly include collateral sensitivity to antibiotics. Bacterial evolution in an inflamed gut yields specific genetic and phenotypic signatures. These results may serve as a basis for developing novel evolution-informed treatment approaches for patients with intestinal inflammation.

Adverse childhood experiences and reoccurrence of illness impact the gut microbiome, which affects suicidal behaviours and the phenome of major depression: towards enterotypic phenotypes

The first publication demonstrating that major depressive disorder (MDD) is associated with alterations in the gut microbiota appeared in 2008 (Maes et al., 2008). The purpose of the present study is to delineate a) the microbiome signature of the phenome of depression, including suicidal behaviours (SB) and cognitive deficits; the effects of adverse childhood experiences (ACEs) and recurrence of illness index (ROI) on the microbiome; and the microbiome signature of lowered high-density lipoprotein cholesterol (HDLc). We determined isometric log-ratio abundances or prevalences of gut microbiome phyla, genera, and species by analysing stool samples from 37 healthy Thai controls and 32 MDD patients using 16S rDNA sequencing. Six microbiome taxa accounted for 36% of the variance in the depression phenome, namely Hungatella and Fusicatenibacter (positive associations) and Butyricicoccus, Clostridium, Parabacteroides merdae, and Desulfovibrio piger (inverse association). This profile (labelled enterotype 1) indicates compositional dysbiosis, is strongly predicted by ACE and ROI, and is linked to SB. A second enterotype was developed that predicted a decrease in HDLc and an increase in the atherogenic index of plasma (Bifidobacterium, P. merdae, and Romboutsia were positively associated, while Proteobacteria and Clostridium sensu stricto were negatively associated). Together, enterotypes 1 and 2 explained 40.4% of the variance in the depression phenome, and enterotype 1 in conjunction with HDLc explained 39.9% of the variance in current SB. In conclusion, the microimmuneoxysome is a potential new drug target for the treatment of severe depression and SB and possibly for the prevention of future episodes.

Healthy Human Fecal Microbiota Transplantation into Mice Attenuates MPTP-Induced Neurotoxicity via AMPK/SOD2 Pathway

Increasing evidence has shown that gut dysbacteriosis may play a crucial role in neuroinflammation in Parkinson's disease (PD). However, the specific mechanisms that link gut microbiota to PD remain unexplored. Given the critical roles of blood-brain barrier (BBB) dysfunction and mitochondrial dysfunction in the development of PD, we aimed to evaluate the interactions among the gut microbiota, BBB, and mitochondrial resistance to oxidation and inflammation in PD. We investigated the effects of fecal microbiota transplantation (FMT) on the physiopathology of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. The aim was to explore the role of fecal microbiota from PD patients and healthy human controls in neuroinflammation, BBB components, and mitochondrial antioxidative capacity via the AMPK/SOD2 pathway. Compared to control mice, MPTP-treated mice exhibited elevated levels of Desulfovibrio, whereas mice given FMT from PD patients exhibited enriched levels of Akkermansia and mice given FMT from healthy humans showed no significant alterations in gut microbiota. Strikingly, FMT from PD patients to MPTP-treated mice significantly aggravated motor impairments, dopaminergic neurodegeneration, nigrostriatal glial activation and colonic inflammation, and inhibited the AMPK/SOD2 signaling pathway. However, FMT from healthy human controls greatly improved the aforementioned MPTP-caused effects. Surprisingly, the MPTP-treated mice displayed a significant loss in nigrostriatal pericytes, which was restored by FMT from healthy human controls. Our findings demonstrate that FMT from healthy human controls can correct gut dysbacteriosis and ameliorate neurodegeneration in the MPTP-induced PD mouse model by suppressing microgliosis and astrogliosis, ameliorating mitochondrial impairments via the AMPK/SOD2 pathway, and restoring the loss of nigrostriatal pericytes and BBB integrity. These findings raise the possibility that the alteration in the human gut microbiota may be a risk factor for PD and provide evidence for potential application of FMT in PD preclinical treatment.

Determination of sulfide in complex biofilm matrices using silver-coated, 4-mercaptobenzonitrile-modified gold nanoparticles, encapsulated in ZIF-8 as surface-enhanced Raman scattering nanoprobe

A surface-enhanced Raman scattering nanoprobe has been developed for sulfide detection and applied to  complex bacterial biofilms. The nanoprobe, Au@4-MBN@Ag@ZIF-8, comprised a gold core modified with 4-mercaptobenzonitrile (4-MBN) as signaling source, a layer of silver shell as the sulfide sensitization material, and a zeolitic imidazolate framework-8 (ZIF-8) as surface barrier. ZIF-8, with its high surface area and mesoporous structure, was applied to preconcentrate sulfide around the nanoprobe with its excellent adsorption capacity. Besides, the external wrapping of ZIF-8 can not only prevent the interference of biomolecules, such as proteins, with the Au@4-MBN@Ag assay but also enhance the detection specificity through the sulfide cleavage function towards ZIF-8. These properties are critical for the application of this nanoprobe to complex environmental scenarios. In the presence of sulfide, it was first enriched through adsorption by the outer ZIF-8 layer, then destroyed the barrier layer, and subsequently reacted with the Ag shell, leading to changes in the Raman signal. Through this rational design, the Au@4-MBN@Ag@ZIF-8 nanoprobe exhibited excellent detection sensitivity, with a sulfide detection limit in the nanomolar range and strong linearity in the concentration range  50 nM to 500 μM. Furthermore, the proposed Au@4-MBN@Ag@ZIF-8 nanoprobe was effectively utilized for sulfide detection in intricate biofilm matrices, demonstrating its robust selectivity and reproducibility.

Genetic predisposition of the gastrointestinal microbiome and primary biliary cholangitis: a bi-directional, two-sample Mendelian randomization analysis

Background

The gut-liver axis indicates a close relationship between the gastrointestinal microbiome (GM) and primary biliary cholangitis (PBC). However, the causality of this relationship remains unknown. This study investigates the causal relationship between the GM and PBC using a bidirectional, two-sample Mendelian randomization (MR) analysis.

Methods

Genome-wide association data for GM and PBC were obtained from public databases. The inverse-variance weighted method was the primary method used for MR analysis. Sensitivity analyses were conducted to assess the stability of the MR results. A reverse MR analysis was performed to investigate the possibility of reverse causality.

Results

Three bacterial taxa were found to be causally related to PBC. Class Coriobacteriia (odds ratio (OR) = 2.18, 95% confidence interval (CI): 1.295-3.661, P< 0.05) and order Coriobacteriales (OR = 2.18, 95% CI: 1.295-3.661, P<0.05) were associated with a higher risk of PBC. Class Deltaproteobacteria (OR = 0.52, 95% CI: 0.362-0.742, P< 0.05) had a protective effect on PBC. There was no evidence of reverse causality between PBC and the identified bacterial taxa.

Conclusion

Previously unrecognized taxa that may be involved in the pathogenesis of PBC were identified in this study, confirming the causality between the GM and PBC. These results provide novel microbial targets for the prevention and treatment of PBC.

Targeted vaccine development against Bilophila wadsworthia to curb colon diseases: A multiepitope approach based on reverse vaccinology and computational analysis

The presence of excessive hydrogen sulfide (H2S)-producing bacteria, particularly Bilophila wadsworthia in appendices, is linked to a weaker colonic mucus barrier, inflammatory bowel disease, and colorectal cancer. Thus, targeting this bacterium could reduce sulfide levels and address associated health concerns. Here, we utilized reverse vaccinology and immunoinformatics to design a chimeric vaccine against B. wadsworthia, focusing on membrane-bound and extracellular proteins. Subtractive proteome analysis identified 18 potential vaccine candidates (PVCs), from which six B-cell, eight CD8+ T cell, and six CD4+ T cell epitopes were predicted. Chosen epitopes were assessed for immunological properties and cross-reactivity with human and mouse proteomes. Subsequently, these epitopes were fused with appropriate linkers, PADRE epitope, TAT peptide, and Cholera Toxin B subunit adjuvant to form a robust multi-epitope vaccine (MEV). The MEV's tertiary structure was modelled and validated for reliable analysis. Molecular docking and dynamics simulations demonstrated stable binding of MEV with Toll-like receptor 4. The MEV showed favorable physicochemical characteristics, high expression potential in Escherichia coli, broad population coverage (∼98 %), and cross-protection against different B. wadsworthia strains. Immune simulation suggested induction of strong B and T cell responses, including primary, secondary, and tertiary immune responses. Further experimental studies are necessary to validate these findings.

A changing gut virome ecological landscape with longevity

A recent study (Johansen et al., 2023) shows how the ecological composition of the human gut virome changes with age, showing a decline in core taxa and an enrichment of subdominant taxa, similar to what has been observed in the gut bacteriomes of centenarians.

The Alteration of the Gut Microbiome during Ramadan Offers a Novel Perspective on Ramadan Fasting: A Pilot Study

An intermittent fasting regimen is widely perceived to lead to various beneficial health effects, including weight loss, the alleviation of insulin resistance, and the restructuring of a healthy gut microbiome. Because it shares certain commonalities with this dietary intervention, Ramadan fasting is sometimes misinterpreted as intermittent fasting, even though there are clear distinctions between these two regimens. The main purpose of this study is to verify whether Ramadan fasting drives the same beneficial effects as intermittent fasting by monitoring alterations in the gut microbiota. We conducted a study involving 20 Muslim individuals who were practicing Ramadan rituals and assessed the composition of their gut microbiomes during the 4-week period of Ramadan and the subsequent 8-week period post-Ramadan. Fecal microbiome analysis was conducted, and short-chain fatty acids (SCFAs) were assessed using liquid-chromatography-mass spectrometry. The observed decrease in the levels of SCFAs and beneficial bacteria during Ramadan, along with the increased microbial diversity post-Ramadan, suggests that the daily diet during Ramadan may not provide adequate nutrients to maintain robust gut microbiota. Additionally, the notable disparities in the functional genes detected through the metagenomic analysis and the strong correlation between Lactobacillus and SCFAs provide further support for our hypothesis.

Dietary Acid Load and Cancer Risk: A Review of the Uruguayan Experience

Dietary acid load (DAL) is recognized as a risk factor for several chronic disorders, including obesity, diabetes, and osteoporosis. Recent evidence suggests that an elevated DAL, as measured by the validated potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores, could also increase the risk for several cancers. This narrative review summarizes the potential role of DAL in Uruguayan cancer patients and outlines the potentially involved pathophysiological pathways that mediate the role of DAL in both cancer development and growth. Although Uruguay is a developing country, its average diet is a heavily meat-based Western one, translating into a supraphysiological acid burden from diet. In recent years, we have published epidemiologic evidence based on ten case-control studies involving 3736 cancer cases and 9534 hospital-based controls. Odds ratios and 95% confidence intervals were estimated for each interest variable to analyze the association between the exposure levels of DAL scores and cancer, calculated by unconditional logistic regression. In a majority of the cases, the highest DAL scores tended to double the cancer risk as compared to the lowest category. We also found high risks for methionine intake, an acidifying amino acid found in higher concentrations in animal-based foods, which may increase cancer risks at least by a joint action based on the pH and the proliferation enhancing properties of the amino acid itself.

Desulfovibrio in the Gut: The Enemy within?

Desulfovibrio (DSV) are sulfate-reducing bacteria (SRB) that are ubiquitously present in the environment and as resident commensal bacteria within the human gastrointestinal tract. Though they are minor residents of the healthy gut, DSV are opportunistic pathobionts that may overgrow in the setting of various intestinal and extra-intestinal diseases. An increasing number of studies have demonstrated a positive correlation between DSV overgrowth (bloom) and various human diseases. While the relationship between DSV bloom and disease pathology has not been clearly established, mounting evidence suggests a causal role for these bacteria in disease development. As DSV are the most predominant genera of SRB in the gut, this review summarizes current knowledge regarding the relationship between DSV and a variety of diseases. In this study, we also discuss the mechanisms by which these bacteria may contribute to disease pathology.

Centenarians have a diverse gut virome with the potential to modulate metabolism and promote healthy lifespan

Distinct gut microbiome ecology may be implicated in the prevention of aging-related diseases as it influences systemic immune function and resistance to infections. Yet, the viral component of the microbiome throughout different stages in life remains unexplored. Here we present a characterization of the centenarian gut virome using previously published metagenomes from 195 individuals from Japan and Sardinia. Compared with gut viromes of younger adults (>18 yr) and older individuals (>60 yr), centenarians had a more diverse virome including previously undescribed viral genera, such as viruses associated with Clostridia. A population shift towards higher lytic activity was also observed. Finally, we investigated phage-encoded auxiliary functions that influence bacterial physiology, which revealed an enrichment of genes supporting key steps in sulfate metabolic pathways. Phage and bacterial members of the centenarian microbiome displayed an increased potential for converting methionine to homocysteine, sulfate to sulfide and taurine to sulfide. A greater metabolic output of microbial hydrogen sulfide in centenarians may in turn support mucosal integrity and resistance to pathobionts.

The role of IL-10 in regulating inflammation and gut microbiome in mice consuming milk kefir and orally challenged with S. Typhimurium

Kefir has been suggested as a possible bacterial prophylaxis against Salmonella and IL-10 production seems to be crucial in the pathogenesis of salmonellosis in mice. This study evaluated the role of IL-10 in the inflammation and gut microbiome in mice consuming milk kefir and orally challenged with Salmonella enterica serovar Typhimurium. C57BL wild type (WT) (n = 40) and C57BL IL-10-/- (KO) (n = 40) mice were subdivided into eight experimental groups either treated or not with kefir. In the first 15 days, the water groups received filtered water (0.1 mL) while the kefir groups received milk kefir (10% w/v) orally by gavage. Then, two groups of each strain received a single dose (0.1 mL) of the inoculum of S. Typhimurium (ATCC 14028, dose: 106 CFU mL-1). After four weeks, the animals were euthanized to remove the colon for further analysis. Kefir prevented systemic infections only in IL-10-/- mice, which were able to survive, regulate cytokines, and control colon inflammation. The abundance in Lachnospiraceae and Roseburia, and also the higher SCFA production in the pre-infection, showed that kefir has a role in intestinal health and protection, colonizing and offering competition for nutrients with the pathogen as well as acting in the regulation of salmonella infectivity only in the absence of IL-10. These results demonstrate the role of IL-10 in the prognosis of salmonellosis and how milk kefir can be used in acute infections.

Sulfur Metabolism of the Gut Microbiome and Colorectal Cancer: The Threat to the Younger Generation

Colorectal cancer diagnosed in individuals under 50 years old is called early-onset colorectal cancer (EOCRC), and its incidence has been rising worldwide. Simultaneously occurring with increasing obesity, this worrisome trend is partly explained by the strong influence of dietary elements, particularly fatty, meaty, and sugary food. An animal-based diet, the so-called Western diet, causes a shift in dominant microbiota and their metabolic activity, which may disrupt the homeostasis of hydrogen sulfide concentration. Bacterial sulfur metabolism is recognized as a critical mechanism of EOCRC pathogenesis. This review evaluates the pathophysiology of how a diet-associated shift in gut microbiota, so-called the microbial sulfur diet, provokes injuries and inflammation to the colonic mucosa and contributes to the development of CRC.

Who is in the driver's seat? Parvimonas micra: An understudied pathobiont at the crossroads of dysbiotic disease and cancer

Recent advances in our understanding of microbiome composition at sites of inflammatory dysbiosis have triggered a substantial interest in a variety of historically understudied bacteria, especially among fastidious obligate anaerobes. A plethora of new evidence suggests that these microbes play outsized roles in establishing synergistic polymicrobial infections at many different sites in the human body. Parvimonas micra is a prime example of such an organism. Despite being almost completely uncharacterized at the genetic level, it is one of the few species commonly detected in abundance at multiple mucosal sites experiencing either chronic or acute inflammatory diseases, and more recently, it has been proposed as a discriminating biomarker for multiple types of malignancies. In the absence of disease, P. micra is commonly found in low abundance, typically residing within the oral cavity and gastrointestinal tract. P. micra exhibits the typical features of an inflammophilic organism, meaning its growth actually benefits from active inflammation and inflammatory tissue destruction. In this mini-review, we will describe our current understanding of this underappreciated but ubiquitous pathobiont, specifically focusing upon the role of P. micra in polymicrobial inflammatory dysbiosis and cancer as well as the key emerging questions regarding its pathobiology. Through this timely work, we highlight Parvimonas micra as a significant driver of disease and discuss its unique position at the crossroads of dysbiosis and cancer.

Gut microbiota biofilms: From regulatory mechanisms to therapeutic targets

Gut microbiota contain communities of viruses, bacteria, fungi, and Eukarya, and live as biofilms. In health, these biofilms adhere to the intestinal mucus surface without contacting the epithelium. Disruptions to the equilibrium between these biofilms and the host may create invasive pathobionts from these commensal communities and contribute to disease pathogenesis. Environmental factors appear to dominate over genetics in determining the shifts in microbiota populations and function, including when comparing microbiota between low-income and industrialized countries. The observations discussed herein carry enormous potential for the development of novel therapies targeting phenotype in microbiota dysbiosis.

H2S-activated fluorescent probe enables dual-channel fluorescence tracking of drug release in tumor cells

Nowadays, the selective release of therapeutic drugs into tumor cells has become an important way of tumor treatment due to the high side effects of chemotherapy drugs. As one of the gas mediators, hydrogen sulfide (H₂S) is closely related to cancer. Due to the high content of H₂S in tumor cells, it can be used as a signaling molecule that triggers the release of drugs to achieve the selective release of therapeutic drugs. In addition, dual-channel fluorescence imaging technology can be better applied to monitor the drug delivery process and distinguish the state before and after drug release, so as to better track the effect of drug therapy. Based on this, we used NBD amines (NBD-NHR) as the recognition group of H₂S and connected the tyrosine kinase inhibitor crizotinib to construct an activated dual-channel fluorescent probe CZ-NBD. After the probe enters the tumor cells, it consumes H₂S and releases crizotinib, which is highly toxic to the tumor cells. Importantly, the probe displays significant fluorescence changes in different cells, enabling not only the screening of tumor cells, but also tracking and monitoring drug release and tumor cell activity. Therefore, the construction of probe CZ-NBD provides a new strategy for drug release monitoring in tumor cells.

Local delivery of gaseous signaling molecules for orthopedic disease therapy

Over the past decade, a proliferation of research has used nanoparticles to deliver gaseous signaling molecules for medical purposes. The discovery and revelation of the role of gaseous signaling molecules have been accompanied by nanoparticle therapies for their local delivery. While most of them have been applied in oncology, recent advances have demonstrated their considerable potential in diagnosing and treating orthopedic diseases. Three of the currently recognized gaseous signaling molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), are highlighted in this review along with their distinctive biological functions and roles in orthopedic diseases. Moreover, this review summarizes the progress in therapeutic development over the past ten years with a deeper discussion of unresolved issues and potential clinical applications.

Impact of diet on hydrogen sulfide production: implications for gut health

PURPOSE OF REVIEW

Excessive hydrogen sulfide (H 2 S) production by the gut microbiota may contribute to the pathogenesis of multiple intestinal diseases, including colon cancer and ulcerative colitis. Therefore, understanding of dietary drivers of H 2 S production has potential implications for nutritional strategies to optimize gut health and treat intestinal diseases.

RECENT FINDINGS

Recent studies support a positive relationship between dietary protein intake and H 2 S production. However, protein rarely exists in isolation in the diet, and dietary fiber intake could reduce H 2 S production in humans and animals, even with ∼30% of calories derived from protein.

SUMMARY

These findings suggest that increased fiber intake may reduce H 2 S production irrespective of protein intake, enabling the ability to meet the metabolic demands of the illness while supporting gut health. Here we discuss two recent ulcerative colitis diet studies that illustrate this point.

Association between diabetes and cancer. Current mechanistic insights into the association and future challenges

Compelling pieces of epidemiological, clinical, and experimental research have demonstrated that Diabetes mellitus (DM) is a major risk factor associated with increased cancer incidence and mortality in many human neoplasms. In the pathophysiology context of DM, many of the main classical actors are relevant elements that can fuel the different steps of the carcinogenesis process. Hyperglycemia, hyperinsulinemia, metabolic inflammation, and dyslipidemia are among the classic contributors to this association. Furthermore, new emerging actors have received particular attention in the last few years, and compelling data support that the microbiome, the epigenetic changes, the reticulum endoplasmic stress, and the increased glycolytic influx also play important roles in promoting the development of many cancer types. The arsenal of glucose-lowering therapeutic agents used for treating diabetes is wide and diverse, and a growing body of data raised during the last two decades has tried to clarify the contribution of therapeutic agents to this association. However, this research area remains controversial, because some anti-diabetic drugs are now considered as either promotors or protecting elements. In the present review, we intend to highlight the compelling epidemiological shreds of evidence that support this association, as well as the mechanistic contributions of many of these potential pathological mechanisms, some controversial points as well as future challenges.

Dietary protein and the intestinal microbiota: An understudied relationship

Diet has a profound impact on the microbial community in the gastrointestinal tract, the intestinal microbiota, to the benefit or detriment of human health. To understand the influence of diet on the intestinal microbiota, research has focused on individual macronutrients. Some macronutrients (e.g. fiber) have been studied in great detail and have been found to strongly influence the intestinal microbiota. The relationship between dietary protein, a vital macronutrient, and the intestinal microbiota has gone largely unexplored. Emerging evidence suggests that dietary protein strongly impacts intestinal microbiota composition and function and that protein-microbiota interactions can have critical impacts on host health. In this review, we focus on recent studies investigating the impact of dietary protein quantity and source on the intestinal microbiota and resulting host health consequences. We highlight major open questions critical to understanding health outcomes mediated by interactions between dietary protein and the microbiota.

The oral-gut axis: Salivary and fecal microbiome dysbiosis in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that fall into two main categories: Crohn's disease (CD) and ulcerative colitis (UC). The gastrointestinal tract extends from the mouth to the anus and harbors diverse bacterial communities. Several sequencing-based studies have identified an intestinal enrichment of oral-associated bacteria and demonstrated their ability to induce intestinal inflammation in mice, suggesting that intestinal pathobionts originate from the oral cavity, particularly members of the genus Streptococcus. This study aimed to investigate the composition of the salivary and fecal microbiome of IBD patients (n = 14) compared to healthy controls (n = 12) and to determine the abundance of common bacterial taxa in both niches. Metagenomic DNA was extracted from saliva and fecal samples, and the 16S rRNA gene was targeted for sequencing. Our results revealed that the overall microbial composition of saliva was significantly altered in the IBD patients compared to the control subjects (p = 0.038). At the genus level, Veillonella and Prevotella were highly abundant in IBD (median: 25.4% and 22.2%, respectively) compared to the control group (17.9% and 13.4%, respectively). In contrast, Neisseria, Streptococcus, Haemophilus, and Fusobacterium were associated with a healthy gut state. Regarding the fecal microbiome, the IBD group had a significantly higher abundance of Clostridium sensu stricto 1 and Escherichia-Shigella (both comprising pathogenic bacteria) compared with the control group. Members of both bacterial groups have previously been shown to positively correlate with intestinal inflammation and high expression of pro-inflammatory cytokines that disrupt intestinal barrier integrity. In addition, we demonstrate that the increased abundance of Clostridium sensu stricto 1 and Escherichia-Shigella has also been associated with significant upregulation of certain metabolic pathways in the feces of the IBD group, including bacterial invasion of epithelial cells. Streptococcus was the only common genus detected in both the salivary and fecal microbiome and represented the oral-gut axis in our study. Using culture-based methods, we isolated 57 and 91 Streptococcus strains from saliva as well as 40 and 31 strains from fecal samples of the controls and IBD patients, respectively. The phylogenetic tree of streptococci based on sodA sequences revealed several patient-specific clusters comprising salivary and fecal streptococcal isolates from the same patient and belonging to the same species, suggesting that the oral cavity is an endogenous reservoir for intestinal strains.

Association of human gut microbiota composition and metabolic functions with Ficus hirta Vahl dietary supplementation

Ficus hirta Vahl (FHV), a traditional herbal ingredient of the tonic diet, receives increasing popularity in southern China. However, it is largely unknown that how a FHV diet (FHVD) affects the human gut microbiome. In this exploratory study, a total of 43 healthy individuals were randomized into the FHVD (n = 25) and Control (n = 18) groups to receive diet intervention for 8 weeks. 16S rRNA gene sequencing, metagenomic sequencing and metabolic profile of participants were measured to assess the association between FHV diet and gut microbiome. A preservation effect of Faecalibacterium and enrichment of Dialister, Veillonella, Clostridium, and Lachnospiraceae were found during the FHVD. Accordingly, the pathway of amino acid synthesis, citrate cycle, coenzyme synthesis, and partial B vitamin synthesis were found to be more abundant in the FHVD. In addition, serine, glutamine, gamma-aminobutyric acid, tryptamine, and short-chain fatty acids (SCFAs) were higher after the FHVD. The conjoint analysis of FHV components and in-vitro fermentation confirmed that the improved SCFAs concentration was collectively contributed by the increasing abundance of key enzyme genes and available substrates. In conclusion, the muti-omics analysis showed that the FHVD optimized the structure of the gut microbial community and its metabolic profile, leading to a healthy tendency, with a small cluster of bacteria driving the variation rather than a single taxon.

Dietary compounds in modulation of gut microbiota-derived metabolites

Gut microbiota, a group of microorganisms that live in the gastrointestinal tract, plays important roles in health and disease. One mechanism that gut microbiota in modulation of the functions of hosts is achieved through synthesizing and releasing a series of metabolites such as short-chain fatty acids. In recent years, increasing evidence has indicated that dietary compounds can interact with gut microbiota. On one hand, dietary compounds can modulate the composition and function of gut microbiota; on the other hand, gut microbiota can metabolize the dietary compounds. Although there are several reviews on gut microbiota and diets, there is no focused review on the effects of dietary compounds on gut microbiota-derived metabolites. In this review, we first briefly discussed the types of gut microbiota metabolites, their origins, and the reasons that dietary compounds can interact with gut microbiota. Then, focusing on gut microbiota-derived compounds, we discussed the effects of dietary compounds on gut microbiota-derived compounds and the following effects on health. Furthermore, we give our perspectives on the research direction of the related research fields. Understanding the roles of dietary compounds on gut microbiota-derived metabolites will expand our knowledge of how diets affect the host health and disease, thus eventually enable the personalized diets and nutrients.

A Whiff of Sulfur: One Wind a Day Keeps the Doctor Away

Reactive Sulfur Species (RSS), such as allicin from garlic or sulforaphane from broccoli, are fre-quently associated with biological activities and possible health benefits in animals and humans. Among these Organic Sulfur Compounds (OSCs) found in many plants and fungi, the Volatile Sulfur Compounds (VSCs) feature prominently, not only because of their often-pungent smell, but also because they are able to access places which solids and solutions cannot reach that easily. Indeed, inorganic RSS such as hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) can be used to lit-erally fumigate entire rooms and areas. Similarly, metabolites of garlic, such as allyl methyl sulfide (AMS), are formed metabolically in humans in lower concentrations and reach the airways from inside the body as part of one’s breath. Curiously, H₂S is also formed in the gastrointestinal tract by gut bacteria, and the question of if and for which purpose this gas then crosses the barriers and enters the body is indeed a delicate matter for equally delicate studies. In any case, nature is surprisingly rich in such VSCs, as fruits (for instance, the infamous durian) demonstrate, and therefore these VSCs represent a promising group of compounds for further studies.

Emerging roles of cystathionine β-synthase in various forms of cancer

The expression of the reverse transsulfuration enzyme cystathionine-β-synthase (CBS) is markedly increased in many forms of cancer, including colorectal, ovarian, lung, breast and kidney, while in other cancers (liver cancer and glioma) it becomes downregulated. According to the clinical database data in high-CBS-expressor cancers (e.g. colon or ovarian cancer), high CBS expression typically predicts lower survival, while in the low-CBS-expressor cancers (e.g. liver cancer), low CBS expression is associated with lower survival. In the high-CBS expressing tumor cells, CBS, and its product hydrogen sulfide (H₂S) serves as a bioenergetic, proliferative, cytoprotective and stemness factor; it also supports angiogenesis and epithelial-to-mesenchymal transition in the cancer microenvironment. The current article reviews the various tumor-cell-supporting roles of the CBS/H₂S axis in high-CBS expressor cancers and overviews the anticancer effects of CBS silencing and pharmacological CBS inhibition in various cancer models in vitro and in vivo; it also outlines potential approaches for biomarker identification, to support future targeted cancer therapies based on pharmacological CBS inhibition.

Hydrogen therapy after resuscitation improves myocardial injury involving inhibition of autophagy in an asphyxial rat model of cardiac arrest

Hydrogen (H₂) therapy is a therapeutic strategy using molecular H₂. Due to its ability to regulate cell homeostasis, H₂ therapy has exhibited marked therapeutic effects on a number of oxidative stress-associated diseases. The present study investigated the effectiveness of H₂ therapy in protecting against myocardial injury in a rat model of asphyxial cardiac arrest and cardiopulmonary resuscitation. Rats underwent 10-min asphyxia-induced cardiac arrest (CA) and cardiopulmonary resuscitation (CPR), and were randomly divided into control and H₂ therapy groups. After resuscitation, the H₂ therapy group was administered room air mixed with 2% H₂ gas for respiration. During CA/CPR, the arterial pressure and heart rate were measured every minute. Survival rate, cardiac function, myocardial injury biomarkers creatine kinase-MB and cardiac troponin-T, and histopathological changes were evaluated to determine the protective effects of H₂ therapy in CA/CPR. Immunohistochemistry and western blot analysis were used to determine the expression levels of autophagy-associated proteins. In vitro, H9C2 cells were subjected to hypoxia/reoxygenation and H₂-rich medium was used in H₂ treatment groups. Western blotting and immunofluorescence were used to observe the expression levels of autophagy-associated proteins. Moreover, an adenovirus-monomeric red fluorescent protein-green fluorescent protein-LC3 construct was used to explore the dynamics of autophagy in the H9C2 cells. The results showed that H₂ therapy significantly improved post-resuscitation survival and cardiac function. H₂ therapy also improved mitochondrial mass and decreased autophagosome numbers in cardiomyocytes after resuscitation. The treatment inhibited autophagy activation, with lower expression levels of autophagy-associated proteins and decreased autophagosome formation in vivo and vitro. In conclusion, H₂ gas inhalation after return of spontaneous circulation improved cardiac function via the inhibition of autophagy.

Impact of the Gastrointestinal Tract Microbiota on Cardiovascular Health and Pathophysiology

ABSTRACT

The microbiota of the gastrointestinal tract (GIT) is an extremely diverse community of microorganisms, and their collective genomes (microbiome) provide a vast arsenal of biological activities, in particular enzymatic ones, which are far from being fully elucidated. The study of the microbiota (and the microbiome) is receiving great interest from the biomedical community as it carries the potential to improve risk-prediction models, refine primary and secondary prevention efforts, and also design more appropriate and personalized therapies, including pharmacological ones. A growing body of evidence, though sometimes impaired by the limited number of subjects involved in the studies, suggests that GIT dysbiosis, i.e. the altered microbial composition, has an important role in causing and/or worsening cardiovascular disease (CVD). Bacterial translocation as well as the alteration of levels of microbe-derived metabolites can thus be important to monitor and modulate, because they may lead to initiation and progression of CVD, as well as to its establishment as chronic state. We hereby aim to provide readers with details on available resources and experimental approaches that are used in this fascinating field of biomedical research, and on some novelties on the impact of GIT microbiota on CVD.

NMR Metabolomics Reveal Urine Markers of Microbiome Diversity and Identify Benzoate Metabolism as a Mediator between High Microbial Alpha Diversity and Metabolic Health

Microbial metabolites measured using NMR may serve as markers for physiological or pathological host–microbe interactions and possibly mediate the beneficial effects of microbiome diversity. Yet, comprehensive analyses of gut microbiome data and the urine NMR metabolome from large general population cohorts are missing. Here, we report the associations between gut microbiota abundances or metrics of alpha diversity, quantified from stool samples using 16S rRNA gene sequencing, with targeted urine NMR metabolites measures from 951 participants of the Study of Health in Pomerania (SHIP). We detected significant genus–metabolite associations for hippurate, succinate, indoxyl sulfate, and formate. Moreover, while replicating the previously reported association between hippurate and measures of alpha diversity, we identified formate and 4-hydroxyphenylacetate as novel markers of gut microbiome alpha diversity. Next, we predicted the urinary concentrations of each metabolite using genus abundances via an elastic net regression methodology. We found profound associations of the microbiome-based hippurate prediction score with markers of liver injury, inflammation, and metabolic health. Moreover, the microbiome-based prediction score for hippurate completely mediated the clinical association pattern of microbial diversity, hinting at a role of benzoate metabolism underlying the positive associations between high alpha diversity and healthy states. In conclusion, large-scale NMR urine metabolomics delivered novel insights into metabolic host–microbiome interactions, identifying pathways of benzoate metabolism as relevant candidates mediating the beneficial health effects of high microbial alpha diversity.

Effects of Exogenous Hydrogen Sulfide on Diabetic Metabolic Disorders in db/db Mice Are Associated With Gut Bacterial and Fungal Microbiota

The effects of hydrogen sulfide (H2S) on diabetic metabolic disorders are still controversial, and the mechanisms underlying these effects remain largely unknown. This study was conducted to investigate the potential relationship between the gut microbiota and the improvement of diabetic metabolic disorders by exogenous H2S in obese db/db mice. The db/db mice were treated with sodium hydrosulfide (NaHS) (80 μmol/kg), or vehicle for 16 weeks, respectively. We measured the serum H2S, obesity parameters, glucose homeostasis, and triglyceride. The sequencing of bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) in the cecal contents of NaHS-treated mice was performed to evaluate the gut microbial communities. We found that supplying exogenous H2S for 16 weeks significantly inhibited the increase of serum triglyceride, blood glucose, and insulin levels and altered specifically the gut bacterial microbiota structure in db/db mice. The relative abundance of some bacterial genera was correlated with the H2S or blood glucose level. Indeed, exogenous H2S increased Firmicutes and decreased Bacteroidetes at the phylum level along with changes of abundance of multifarious genera. Among them, Unclassified_Enterobacteriaceae, Prevotella, and Lactobacillus decreased and Unclassified_Ruminococcaceae, Oscillospira, Ruminococcus, Sutterella, and Desulfovibrio increased. For fungi, exogenous H2S decreased the abundance of Candida and Aspergillus. Here we demonstrated that, in diabetes, microbial dysbiosis may not be just limited to bacteria due to the inter-linked metabolic interactions among bacteria and fungi in the gut. The beneficial effects of exogenous H2S on diabetic metabolic disorders are likely associated with the alterations of specific microbiota.

Hydrogen Sulfide Produced by Gut Bacteria May Induce Parkinson's Disease

Several bacterial species can generate hydrogen sulfide (H2S). Study evidence favors the view that the microbiome of the colon harbors increased amounts of H2S producing bacteria in Parkinson's disease. Additionally, H2S can easily penetrate cell membranes and enter the cell interior. In the cells, excessive amounts of H2S can potentially release cytochrome c protein from the mitochondria, increase the iron content of the cytosolic iron pool, and increase the amount of reactive oxygen species. These events can lead to the formation of alpha-synuclein oligomers and fibrils in cells containing the alpha-synuclein protein. In addition, bacterially produced H2S can interfere with the body urate metabolism and affect the blood erythrocytes and lymphocytes. Gut bacteria responsible for increased H2S production, especially the mucus-associated species of the bacterial genera belonging to the Desulfovibrionaceae and Enterobacteriaceae families, are likely play a role in the pathogenesis of Parkinson's disease. Special attention should be devoted to changes not only in the colonic but also in the duodenal microbiome composition with regard to the pathogenesis of Parkinson's disease. Influenza infections may increase the risk of Parkinson's disease by causing the overgrowth of H2S-producing bacteria both in the colon and duodenum.

Advances in pathogenesis and therapeutic strategies for osteoporosis

Osteoporosis, is the most common bone disorder worldwide characterized by low bone mineral density, leaving affected bones vulnerable to fracture. Bone homeostasis depends on the precise balance between bone resorption by osteoclasts and bone matrix formation by mesenchymal lineage osteoblasts, and involves a series of complex and highly regulated steps. Bone homeostasis will be disrupted when the speed of bone resorption is faster than bone formation. Based on various regulatory mechanisms of bone homeostasis, a series of drugs targeting osteoporosis have emerged in clinical practice, including bisphosphonates, selective estrogen receptor modulators, calcitonin, molecular-targeted drugs and so on. However, many drugs have major adverse effects or are unsuitable for long-term use. Therefore, it is very urgent to find more effective therapeutic drugs based on the new pathogenesis of osteoporosis. In this review, we summarize novel mechanisms involved in the pathological process of osteoporosis, including the roles of gut microbiome, autophagy, iron balance and cellular senescence. Based on the above pathological mechanism, we found promising drugs for osteoporosis treatment, such as: probiotics, alpha-ketoglutarate, senolytics and hydrogen sulfide. This new finding may provide an important basis for elucidating the complex pathological mechanisms of osteoporosis and provide promising drugs for clinical osteoporosis treatment.