Harnessing the microbiota for therapeutic purposes

Does "all disease begin in the gut"? The gut-organ cross talk in the microbiome

The human microbiome, a diverse ecosystem of microorganisms within the body, plays pivotal roles in health and disease. This review explores site-specific microbiomes, their role in maintaining health, and strategies for their upkeep, focusing on oral, lung, vaginal, skin, and gut microbiota, and their systemic connections. Understanding the intricate relationships between these microbial communities is crucial for unraveling mechanisms underlying human health. Recent research highlights bidirectional communication between the gut and distant microbiome sites, influencing immune function, metabolism, and disease susceptibility. Alterations in one microbiome can impact others, emphasizing their interconnectedness and collective influence on human physiology. The therapeutic potential of gut microbiota in modulating distant microbiomes offers promising avenues for interventions targeting various disorders. Through interdisciplinary collaboration and technological advancements, we can harness the power of the microbiome to revolutionize healthcare, emphasizing microbiome-centric approaches to promote holistic well-being while identifying areas for future research.

Exploring the Therapeutic Potential of Gamma-Aminobutyric Acid in Stress and Depressive Disorders through the Gut-Brain Axis

Research conducted on individuals with depression reveals that major depressive disorders (MDDs) coincide with diminished levels of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) in the brain, as well as modifications in the subunit composition of the primary receptors (GABAA receptors) responsible for mediating GABAergic inhibition. Furthermore, there is substantial evidence supporting the significant role of GABA in regulating stress within the brain, which is a pivotal vulnerability factor in mood disorders. GABA is readily available and approved as a food supplement in many countries. Although there is substantial evidence indicating that orally ingested GABA may affect GABA receptors in peripheral tissues, there is comparatively less evidence supporting its direct action within the brain. Emerging evidence highlights that oral GABA intake may exert beneficial effects on the brain and psyche through the gut-brain axis. While GABA enjoys wide consumer acceptance in Eastern Asian markets, with many consumers reporting favorable effects on stress regulation, mood, and sleep, rigorous independent research is still largely lacking. Basic research, coupled with initial clinical findings, makes GABA an intriguing neuro-nutritional compound deserving of clinical studies in individuals with depression and other psychological problems.

Detoxified pneumolysin derivative ΔA146Ply inhibits triple- negative breast cancer metastasis mainly via mannose receptor-mediated autophagy inhibition

The detoxified pneumolysin derivative ΔA146Ply has been proven to have a direct anti-triple negative breast cancer effect by our group, but its work model remains unclear. In this study, we focused on its ability to inhibit triple-negative breast cancer metastasis. We found that ΔA146Ply suppressed the migration and invasion of triple-negative breast cancer cells by activating mannose receptor and toll-like receptor 4. Their activation triggers the activation of the mammalian target of rapamycin signaling, sequentially leading to autophagy, transforming growth factor-β1, and epithelial-mesenchymal transition inhibition. Furthermore, the combination of doxorubicin and ΔA146Ply significantly inhibited triple-negative breast cancer progression and prolonged survival in tumor-bearing mice. Taken together, our study provides an alternative microbiome-based mannose receptor-targeted therapy for triple-negative breast cancer and a novel theoretical and experimental basis for the downstream signaling pathway of the mannose receptor.

The Evolving Landscape of Fecal Microbial Transplantation

The human gastrointestinal tract houses an enormous microbial ecosystem. Recent studies have shown that the gut microbiota plays significant physiological roles and maintains immune homeostasis in the human body. Dysbiosis, an imbalanced gut microbiome, can be associated with various disease states, as observed in infectious diseases, inflammatory diseases, autoimmune diseases, and cancer. Modulation of the gut microbiome has become a therapeutic target in treating these disorders. Fecal microbiota transplantation (FMT) from a healthy donor restores the normal gut microbiota homeostasis in the diseased host. Ample evidence has demonstrated the efficacy of FMT in recurrent Clostridioides difficile infection (rCDI). The application of FMT in other human diseases is gaining attention. This review aims to increase our understanding of the mechanisms of FMT and its efficacies in human diseases. We discuss the application, route of administration, limitations, safety, efficacies, and suggested mechanisms of FMT in rCDI, autoimmune diseases, and cancer. Finally, we address the future perspectives of FMT in human medicine.

The gut microbiota promotes distal tissue regeneration via RORγ+ regulatory T cell emissaries

Specific microbial signals induce the differentiation of a distinct pool of RORγ+ regulatory T (Treg) cells crucial for intestinal homeostasis. We discovered highly analogous populations of microbiota-dependent Treg cells that promoted tissue regeneration at extra-gut sites, notably acutely injured skeletal muscle and fatty liver. Inflammatory meditators elicited by tissue damage combined with MHC-class-II-dependent T cell activation to drive the accumulation of gut-derived RORγ+ Treg cells in injured muscle, wherein they regulated the dynamics and tenor of early inflammation and helped balance the proliferation vs. differentiation of local stem cells. Reining in IL-17A-producing T cells was a major mechanism underlying the rheostatic functions of RORγ+ Treg cells in compromised tissues. Our findings highlight the importance of gut-trained Treg cell emissaries in controlling the response to sterile injury of non-mucosal tissues.

Profiling rhythmicity of bile salt hydrolase activity in the gut lumen with a rapid fluorescence assay

Diurnal rhythmicity of cellular function is key to survival for most organisms on Earth. Many circadian functions are driven by the brain, but regulation of a separate set of peripheral rhythms remains poorly understood. The gut microbiome is a potential candidate for regulation of host peripheral rhythms, and this study sought to specifically examine the process of microbial bile salt biotransformation. To enable this work, an assay for bile salt hydrolase (BSH) that could work with small quantities of stool samples was necessary. Using a turn-on fluorescence probe, we developed a rapid and inexpensive assay to detect BSH enzyme activity with concentrations as low as 6-25 μM, which is considerably more robust than prior approaches. We successfully applied this rhodamine-based assay to detect BSH activity in a wide range of biological samples such as recombinant protein, whole cells, fecal samples, and gut lumen content from mice. We were able to detect significant BSH activity in small amounts of mouse fecal/gut content (20-50 mg) within 2 h, which illustrates its potential for use in various biological/clinical applications. Using this assay, we investigated the diurnal fluctuations of BSH activity in the large intestine of mice. By using time restricted feeding conditions, we provided direct evidence of 24 h rhythmicity in microbiome BSH activity levels and showed that this rhythmicity is influenced by feeding patterns. Our novel function-centric approach has potential to aid in the discovery of therapeutic, diet, or lifestyle interventions for correction of circadian perturbations linked to bile metabolism.

The Interplay Between Gut Microbiota and miRNAs in Cardiovascular Diseases

The human microbiota contains microorganisms found on the skin, mucosal surfaces and in other tissues. The major component, the gut microbiota, can be influenced by diet, genetics, and environmental factors. Any change in its composition results in pathophysiological changes that can further influence the evolution of different conditions, including cardiovascular diseases (CVDs). The microbiome is a complex ecosystem and can be considered the metagenome of the microbiota. MicroRNAs (miRNAs) are speculated to interact with the intestinal microbiota for modulating gene expressions of the host. miRNAs represent a category of small non-coding RNAs, consisting of approximately 22 nucleotides, which can regulate gene expression at post-transcriptional level, by influencing the degradation of mRNA and modifying protein amounts. miRNAs display a multitude of roles, being able to influence the pathogenesis and progression of various diseases. Circulating miRNAs are stable against degradation, due to their enclosure into extracellular vesicles (EVs). This review aims to assess the current knowledge of the possible interactions between gut microbiota, miRNAs, and CVDs. As more scientific research is conducted, it can be speculated that personalized patient care in the future may include the management of gut microbiota composition and the targeted treatment against certain expression of miRNAs.

Towards a deeper understanding of the vaginal microbiota

The human vaginal microbiota is a critical determinant of vaginal health. These communities live in close association with the vaginal epithelium and rely on host tissues for resources. Although often dominated by lactobacilli, the vaginal microbiota is also frequently composed of a collection of facultative and obligate anaerobes. The prevalence of these communities with a paucity of Lactobacillus species varies among women, and epidemiological studies have associated them with an increased risk of adverse health outcomes. The mechanisms that drive these associations have yet to be described in detail, with few studies establishing causative relationships. Here, we review our current understanding of the vaginal microbiota and its connection with host health. We centre our discussion around the biology of the vaginal microbiota when Lactobacillus species are dominant versus when they are not, including host factors that are implicated in shaping these microbial communities and the resulting adverse health outcomes. We discuss current approaches to modulate the vaginal microbiota, including probiotics and vaginal microbiome transplants, and argue that new model systems of the cervicovaginal environment that incorporate the vaginal microbiota are needed to progress from association to mechanism and this will prove invaluable for future research.

Probiotics and MicroRNA: Their Roles in the Host-Microbe Interactions

Probiotics are widely accepted to be beneficial for the maintenance of the gut homeostasis - the dynamic and healthy interactions between host and gut microorganisms. In addition, emerging as a key molecule of inter-domain communication, microRNAs (miRNAs) can also mediate the host-microbe interactions. However, a comprehensive description and summary of the association between miRNAs and probiotics have not been reported yet. In this review, we have discussed the roles of probiotics and miRNAs in host-microbe interactions and proposed the association of probiotics with altered miRNAs in various intestinal diseases and potential molecular mechanisms underlying the action of probiotics. Furthermore, we provided a perspective of probiotics-miRNA-host/gut microbiota axis applied in search of disease management highly associated with the gut microbiome, which will potentially prove to be beneficial for future studies.

Feasibility of fecal microbiota transplantation via oral gavage to safely alter gut microbiome composition in marmosets

Disruption of microbial communities within human hosts has been associated with infection, obesity, cognitive decline, cancer risk and frailty, suggesting that microbiome-targeted therapies may be an option for improving healthspan and lifespan. The objectives of this study were to determine the feasibility of delivering fecal microbiota transplants (FMTs) to marmosets via oral gavage and to evaluate if alteration of the gut microbiome post-FMT could be achieved. This was a prospective study of marmosets housed at the Barshop Institute for Longevity and Aging Studies in San Antonio, Texas. Eligible animals included healthy young adult males (age 2-5 years) with no recent medication use. Stool from two donors was combined and administered in 0.5 ml doses to five young recipients once weekly for 3 weeks. Safety outcomes and alterations in the gut microbiome composition via 16S ribosomal RNA sequencing were compared at baseline and monthly up to 6 months post-FMT. Overall, significant differences in the percent relative abundance was seen in FMT recipients at the phylum and family levels from baseline to 1 month and baseline to 6 months post-FMT. In permutational multivariate analysis of variance analyses, treatment status (donor vs. recipient) (p = .056) and time course (p = .019) predicted β diversity (p = .056). The FMT recipients did not experience any negative health outcomes over the course of the treatment. FMT via oral gavage was safe to administer to young adult marmosets. The marmoset microbiome may be altered by FMT; however, progressive changes in the microbiome are strongly driven by the host and its baseline microbiome composition.

Amelioration of non-alcoholic fatty liver disease by sodium butyrate is linked to the modulation of intestinal tight junctions in db/db mice

The intestinal microenvironment, a potential factor that contributes to the development of non-alcoholic fatty liver disease (NALFD) and type 2 diabetes (T2DM), has a close relationship with intestinal tight junctions (TJs). Here, we show that the disruption of intestinal TJs in the intestines of 16-week-old db/db mice and in high glucose (HG)-cultured Caco-2 cells can both be improved by sodium butyrate (NaB) in a dose-dependent manner in vitro and in vivo. Accompanying the improved intestinal TJs, NaB not only relieved intestine inflammation of db/db mice and HG and LPS co-cultured Caco-2 cells but also restored intestinal Takeda G-protein-coupled (TGR5) expression, resulting in up-regulated serum GLP-1 levels. Subsequently, the GLP-1 analogue Exendin-4 was used to examine the improvement of lipid accumulation in HG and free fatty acid (FFA) co-cultured HepG2 cells. Finally, we used 16-week-old db/db mice to examine the hepatoprotective effects of NaB and its producing strain Clostridium butyricum. Our data showed that NaB and Clostridium butyricum treatment significantly reduced the levels of blood glucose and serum transaminase and markedly reduced T2DM-induced histological alterations of the liver, together with improved liver inflammation and lipid accumulation. These findings suggest that NaB and Clostridium butyricum are a potential adjuvant treatment strategy for T2DM-induced NAFLD; their hepatoprotective effect was linked to the modulation of intestinal TJs, causing the restoration of glucose and lipid metabolism and the improvement of inflammation in hepatocytes.

Commentary: Reconciling Hygiene and Cleanliness: A New Perspective from Human Microbiome

Human beings have co-evolved with the microorganisms in our environment for millions of years, and have developed into a symbiosis in a mutually beneficial/defensive way. Human beings have significant multifaceted relationships with the diverse microbial community. Apart from the important protective role of microbial community exposure in development of early immunity, millions of inimitable bacterial genes of the diverse microbial community are the indispensable source of essential nutrients like essential amino acids and essential fatty acids for human body. The essential nutrition from microbiome is harvested through xenophagy. As an immune effector, xenophagy will capture any microorganisms that touch the epithelial cells of our gastrointestinal tract, degrade them and turn them into nutrients for the use of our body.