The gut microbiota and diabetes: research, translation, and clinical applications - 2023 Diabetes, Diabetes Care, and Diabetologia Expert Forum.

This article summarises the state of the science on the role of the gut microbiota (GM) in diabetes from a recent international expert forum organised by Diabetes, Diabetes Care, and Diabetologia, which was held at the European Association for the Study of Diabetes 2023 Annual Meeting in Hamburg, Germany. Forum participants included clinicians and basic scientists who are leading investigators in the field of the intestinal microbiome and metabolism. Their conclusions were as follows: (1) the GM may be involved in the pathophysiology of type 2 diabetes, as microbially produced metabolites associate both positively and negatively with the disease, and mechanistic links of GM functions (e.g. genes for butyrate production) with glucose metabolism have recently emerged through the use of Mendelian randomisation in humans; (2) the highly individualised nature of the GM poses a major research obstacle, and large cohorts and a deep-sequencing metagenomic approach are required for robust assessments of associations and causation; (3) because single time point sampling misses intraindividual GM dynamics, future studies with repeated measures within individuals are needed; and (4) much future research will be required to determine the applicability of this expanding knowledge to diabetes diagnosis and treatment, and novel technologies and improved computational tools will be important to achieve this goal.

Role of bacteria and microbial metabolites in immune modulation during early life.

Host-microbiome interplay from birth is essential for immune imprinting and tuning. Live gut microbes and microbial-derived metabolites regulate the development and modulation of the immune system, but whether microbial metabolites solely are sufficient to induce immune maturation remains unclear. Sterile faecal filtrates (FFT) were generated from murine gut contents. Newborn germ-free (GF) mice were treated twice daily with FFT (GF-FFT) or saline (GF-NaCl) from post-natal day 5 until 4 weeks of age. A third group of GF neonates were conventionalized by the transfer of caecal microbiota with live gut microbes. Host immune compartments were comprehensively immunophenotyped and systemically analysed in all available immune-related organs using flow cytometry. Oral FFT was associated with reduced survival among neonates (n = 7/19; 36.8% mortality), while saline treatment was well tolerated (n = 1/17, 5.9% mortality). Four-week-old FFT-treated pups were comparable in body weight to GF-NaCl, and the major B-cell, conventional T-cell and unconventional T-cell subsets were unchanged from saline-treated mice. Live bacteria administered during early life induced clear changes in proportions of B cells, T cells and T-cell subsets in all mucosal tissues and secondary lymphoid organs compared to GF-FFT, including restoration of intestinal natural killer T (NKT) cells with characteristics similar to conventional pups. Our findings show that oral administration of a FFT made of microbial metabolites, antigens and bacteriophages alone is insufficient to induce normal immune development elicited by the presence of live bacteria. Reduced survival during neonatal FFT treatment suggests a potential bioactive attribute of sterile faecal filtrates.

Long-term efficacy of washed microbiota transplantation in overweight patients.

BACKGROUND: Faecal microbiota transplantation holds promise in mitigating fat accumulation and improving obesity. This study aimed to evaluate the long-term efficacy of washed microbiota transplantation (WMT) among overweight patients. METHODS: The clinical data pertaining to the treatment of patients with WMT were collected retrospectively. Compared alterations in body mass index (BMI), blood glucose, blood lipids and blood pressure prior to and following WMT treatment. Comprehensive efficacy evaluation and atherosclerosis cardiovascular disease (ASCVD) grading evaluation were carried out, with an analysis of gut microbiota composition before and after WMT. RESULTS: A total of 186 patients were included (80 overweight, 106 normal weight). WMT not only had the effect of improving overweight patients to the normal weight patients (p < .001), but also could significantly reduce BMI in the long term by restoring gut microbiota homeostasis (p < .001). In addition, the BMI improvement value of multi course was more significant than that of single course or double course. WMT had a significant ASCVD downgrade effect on the high-risk and medium-risk groups outside 1 year, while it did not increase the risk of upgrading ASCVD for low-risk group. CONCLUSIONS: WMT could significantly reduce the BMI of overweight patients and still had an improvement effect in the long term.

Increasing the transplant dose and repeating faecal microbiota transplantation results in the responses of male patients with IBS reaching those of females.

BACKGROUND: Faecal microbiota transplantation (FMT) performed with a proper protocol is a safe treatment for IBS that has high efficacy and durable effects. Females have been reported to respond better than males to FMT. The present study aimed at determining whether increasing the transplant dose or repeating FMT improve the responses of males to FMT. METHODS: This study included 186 IBS patients (131 females and 55 males) who were randomized at a 1:1:1 ratio to receive 90 g of donor faeces once into the large intestine, once into the small intestine or twice into the small intestine. Patients completed five questionnaires that assessed their symptoms and quality of life, and provided faecal samples at baseline and at 3, 6 and 12 months after FMT. The faecal bacterial profile and dysbiosis index were determined using 16S rRNA gene PCR DNA amplification covering variable genes V3-V9. RESULTS: The response rates to FMT at all observation times did not differ significantly between females and males regardless of the transplant administration route or whether it was repeated. Faecal Alistipes levels were higher in females than in males at baseline and increased in both females and males after FMT. In the repeated group, the Alistipes levels did not differ between females and males after FMT. CONCLUSIONS: Increasing the transplant dose and repeating FMT results in the responses of male IBS patients to FMT reaching those of females regardless of the administration route. Alistipes spp. levels appear to play a role in this improvement.www.clinicaltrials.gov (NCT04236843).

Microbiota from Alzheimer's patients induce deficits in cognition and hippocampal neurogenesis.

Alzheimer's disease is a complex neurodegenerative disorder leading to a decline in cognitive function and mental health. Recent research has positioned the gut microbiota as an important susceptibility factor in Alzheimer's disease by showing specific alterations in the gut microbiome composition of Alzheimer's patients and in rodent models. However, it is unknown whether gut microbiota alterations are causal in the manifestation of Alzheimer's symptoms. To understand the involvement of Alzheimer's patient gut microbiota in host physiology and behaviour, we transplanted faecal microbiota from Alzheimer's patients and age-matched healthy controls into microbiota-depleted young adult rats. We found impairments in behaviours reliant on adult hippocampal neurogenesis, an essential process for certain memory functions and mood, resulting from Alzheimer's patient transplants. Notably, the severity of impairments correlated with clinical cognitive scores in donor patients. Discrete changes in the rat caecal and hippocampal metabolome were also evident. As hippocampal neurogenesis cannot be measured in living humans but is modulated by the circulatory systemic environment, we assessed the impact of the Alzheimer's systemic environment on proxy neurogenesis readouts. Serum from Alzheimer's patients decreased neurogenesis in human cells in vitro and were associated with cognitive scores and key microbial genera. Our findings reveal for the first time, that Alzheimer's symptoms can be transferred to a healthy young organism via the gut microbiota, confirming a causal role of gut microbiota in Alzheimer's disease, and highlight hippocampal neurogenesis as a converging central cellular process regulating systemic circulatory and gut-mediated factors in Alzheimer's.

Efficacy of Donor-Recipient-Matched Faecal Microbiota Transplantation in Patients with IBS-D: A Single-Centre, Randomized, Double-Blind Placebo-Controlled Study.

INTRODUCTION: The imbalance in gut microbiota is contributing to the development and progression of IBS. FMT can improve the gut microbiota, and donor-recipient-matched FMT can help develop individualized treatment plans according to different enterotypes. This study aimed to explore the efficacy of donor-recipient-matched FMT in IBS with predominant diarrhoea (IBS-D) and evaluate its effects on gut microbiota. METHODS: Twenty-seven patients with IBS-D were randomly divided into donor-recipient-matched FMT group (group P), random-donor FMT group (group R), and placebo group (group B). All participants received corresponding FMT treatment after filling in IBS-S, IBS-QoL, GSRS, and HADS questionnaires and having their stool samples collected at 4, 8, and 12 weeks after treatment. The improvement in the symptoms and the changes in the bacterial flora were analysed for three groups. RESULTS: The IBS-SSS, IBS-QoL, GSRS, and anxiety scores of group P were significantly lower after treatment (p < 0.05). The IBS-QoL scores of group R were significantly lower after treatment (p < 0.05). Beta diversity analysis showed that the gut microbiota of group P had an obvious trend of classification after treatment. Seven bacterial genera were related to the differences in the IBS-SSS scores before and after treatment. CONCLUSION: Donor-recipient-matched FMT significantly improved the clinical symptoms, quality of life, and anxiety scores of the patients with IBS-D than random-donor FMT.

Reduction in Renal Interstitial Fibrosis in Aged Male Mice by Intestinal Microbiota Rejuvenation.

INTRODUCTION: Renal interstitial fibrosis is an important pathological basis for kidney ageing and the progression of ageing nephropathy. In the present research, we established an aged mouse model of faecal microbiota transplantation (FMT), identified the rejuvenation features of the kidney in aged male mice, and preliminarily analysed the possible mechanism by which the rejuvenation of the intestinal microbiota reduces renal interstitial fibrosis and delays senescence in aged male mice. METHODS: We established an aged male mice model that was treated with FMT (FMT-Old) and a normal aged male mice control group (Old). Differentially expressed cytokines were identified using a cytokine array, and changes in protein expression related to signal transduction pathways in renal tissues were detected using a signalling pathway array. Senescence-associated ß-galactosidase and Masson staining were performed to observe the degrees of renal senescence and tubule interstitial fibrosis. Immunohistochemistry was utilized to detect changes in the expression of the ageing markers p53 and p21 and the inflammation-related protein nuclear factor (NF-κB) subunit (RelA/p65). RESULTS: The pathological features of renal senescence in the FMT-Old group were significantly alleviated, and the levels of the ageing indicators p53 and p21 were decreased (p < 0.05). Ingenuity Pathway Analysis revealed that six differentially expressed cytokines, MIP-3ß (CCL-19), E-selectin (SELE), Fas ligand (Fas L/FASLG), CXCL-11 (I-TAC), CXCL-1 and CCL-3 (MIP-1α) were related to a common upstream regulatory protein, RelA/p65, and the expression of this protein was significantly different between groups according to the signalling pathway array. CONCLUSION: Our findings suggest that the intestinal microbiota regulates the renal microenvironment by reducing immune inflammatory responses through the inhibition of the NF-κB signalling pathway, thereby delaying renal senescence in aged male mice.

Assessment of Faecal Microbiota Transplant Stability in Deep-Freeze Conditions: A 12-Month Ex Vivo Viability Analysis.

BACKGROUND: Faecal microbiota transplantation (FMT) is an established treatment for Clostridioides difficile infection and is under investigation for other conditions. The availability of suitable donors and the logistics of fresh stool preparation present challenges, making frozen, biobanked stools an attractive alternative. AIMS: This study aimed to evaluate the long-term viability of bacterial populations in faecal samples stored at -80°C for up to 12 months, supporting the feasibility of using frozen grafts for FMT. METHODS: Fifteen faecal samples from nine healthy donors were processed, mixed with cryoprotectants and stored at -80°C. Samples were assessed at baseline and after 3, 6 and 12 months using quantitative culturing methods to determine the concentration of live bacteria. RESULTS: Quantitative analysis showed no significant decrease in bacterial viability over the 12-month period for both aerobic and anaerobic cultures (p = 0.09). At all timepoints, the coefficients of variability in colony-forming unit (CFU) counts were greater between samples (102 ± 21% and 100 ± 13% for aerobic and anaerobic cultures, respectively) than the variability between measurements of the same sample (30 ± 22% and 30 ± 19%). CONCLUSIONS: The study confirmed that faecal microbiota can be preserved with high viability in deep-freeze storage for up to a year, making allogenic FMT from biobanked samples a viable and safer option for patients. However, a multidonor approach may be beneficial to mitigate the risk of viability loss in any single donor sample.

Faecal microbiota transplantation in children: A systematic review.

AIM: Novel technologies offer insights into the potential role of the intestinal microbiota in human health and disease. Dysbiosis has been associated with several diseases, and it is thought to play a role in the pathogenesis of different gastrointestinal diseases. Faecal microbiota transplantation (FMT) is emerging as a method to modulate the gastrointestinal microbial ecosystem. While recurrent Clostridioides difficile infection is the recognised FMT indication, exploration of other therapeutic uses is ongoing. METHODS: Following PRISMA guidelines, we conducted a systematic review, extracting 583 articles from Embase and PubMed (index date to October 2022). RESULTS: The search yielded 58 studies for full review, with 50 included in the systematic review. Articles were categorised by FMT indication, study design, efficacy, adverse events, donor selection and administration route. FMT appears safe and effective for recurrent Clostridioides difficile infection, although severe adverse events are reported in children. However, there are currently insufficient data to support the use of FMT for other potential therapeutic indications (such as irritable or inflammatory bowel disease or obesity), beside the potential to decolonise multi-drug resistant organisms. CONCLUSION: This underscores the need for randomised, controlled, prospective cohort studies in children to assess FMT effectiveness in diverse conditions and counteract publication bias.

Randomized, double-blinded, placebo-controlled pilot study: efficacy of faecal microbiota transplantation on chronic fatigue syndrome.

BACKGROUND: Chronic fatigue syndrome (CFS) is a disabling illness of unknown aetiology. Disruption of gut microbiota may play a role in several neurological disorders. In this study, the effect of faecal microbiota transplantation (FMT) on fatigue severity and health-related quality of life (HRQOL) in patients with CFS was evaluated. METHODS: Randomized, placebo-controlled pilot trial. Patients and researchers were blinded to treatment assignment. 11 patients with CFS (10 female and 1 male, mean age 42.2 years and mean duration of CFS 6.3 years) were randomly assigned to receive either FMT from a universal donor (n = 5) or autologous FMT (n = 6) via colonoscopy. Patients' HRQOL was assessed by using visual analog scale (VAS) and self-reporting questionnaires Modified Fatigue Impact Scale (MFIS), 15D and EQ-5D-3L. Patients' HRQOL was evaluated at baseline, and 1 and 6 months after the FMT. RESULTS: The baseline VAS scores in the FMT and placebo groups were 62.4 and 76.0 (p = 0.29). 1-month scores were 60.0 and 73.7 and 6-months scores 72.8 and 69.5, respectively. Total MFIS scores in the FMT and placebo groups were 59.6 and 61.0 at the baseline (p = 0.80), 53.5 and 62.0 at 1 month and 58.6 and 56.2 at 6 months. Compared to the baseline scores, differences at 1 and 6 months were statistically insignificant both in VAS and in MFIS. The 15D and EQ-5D-3L profiles did not change after the FMT or placebo. FMT-related adverse events were not reported. CONCLUSION: FMT was safe but did not relieve symptoms or improve the HRQOL of patients with CFS. Small number of study subjects limits the generalizability of these results. Trial Registration ClinicalTrials.gov Identifier NCT04158427, https://register. CLINICALTRIALS: gov , date of registration 08/08/2019.

Washed microbiota transplantation improves renal function in patients with renal dysfunction: a retrospective cohort study.

BACKGROUND: Changes in the gut microbiota composition is a hallmark of chronic kidney disease (CKD), and interventions targeting the gut microbiota present a potent approach for CKD treatment. This study aimed to evaluate the efficacy and safety of washed microbiota transplantation (WMT), a modified faecal microbiota transplantation method, on the renal activity of patients with renal dysfunction. METHODS: A comparative analysis of gut microbiota profiles was conducted in patients with renal dysfunction and healthy controls. Furthermore, the efficacy of WMT on renal parameters in patients with renal dysfunction was evaluated, and the changes in gut microbiota and urinary metabolites after WMT treatment were analysed. RESULTS: Principal coordinate analysis revealed a significant difference in microbial community structure between patients with renal dysfunction and healthy controls (P = 0.01). Patients with renal dysfunction who underwent WMT exhibited significant improvement in serum creatinine, estimated glomerular filtration rate, and blood urea nitrogen (all P < 0.05) compared with those who did not undergo WMT. The incidence of adverse events associated with WMT treatment was low (2.91%). After WMT, the Shannon index of gut microbiota and the abundance of several probiotic bacteria significantly increased in patients with renal dysfunction, aligning their gut microbiome profiles more closely with those of healthy donors (all P < 0.05). Additionally, the urine of patients after WMT demonstrated relatively higher levels of three toxic metabolites, namely hippuric acid, cinnamoylglycine, and indole (all P < 0.05). CONCLUSIONS: WMT is a safe and effective method for improving renal function in patients with renal dysfunction by modulating the gut microbiota and promoting toxic metabolite excretion.

Washed microbiota transplantation improves haemoglobin levels in anaemia of chronic disease.

BACKGROUND: Anaemia of chronic disease (ACD) is the second most common type of anaemia and lacks an effective treatment. Patients with anaemia are reported to have altered gut microbial profiles, which may affect erythropoiesis. Here, we investigated the gut microbial features of patients with ACD and determined whether regulating gut microbiota using washed microbiota transplantation (WMT) was effective in treating ACD. METHODS: We compared the gut microbiota profile of patients with ACD and healthy controls, evaluated the efficacy of WMT on haematological parameters in the patients, and analysed the alterations in gut microbiota after WMT treatment. RESULTS: Patients with ACD had lower gut microbial richness, and differences in microbial composition and function, relative to healthy controls. Additionally, the relative abundances of two butyrate-producing genera Lachnospiraceae NK4A136 group and Butyricicoccus, were positively correlated with the haemoglobin (HGB) level and lower in patients with ACD than controls. WMT significantly increased HGB levels in patients with ACD. After the first, second and third WMT rounds, normal HGB levels were restored in 27.02%, 27.78% and 36.37% (all p < .05) of patients with ACD, respectively. Moreover, WMT significantly increased the abundance of butyrate-producing genera and downregulated gut microbial functions that were upregulated in patients with ACD. CONCLUSIONS: Patients with ACD exhibited differences in gut microbial composition and function relative to healthy controls. WMT is an effective treatment for ACD that reshapes gut microbial composition, restores butyrate-producing bacteria and regulates the functions of gut microbiota.

Absence of gut microbiota reduces neonatal survival and exacerbates liver disease in Cyp2c70-deficient mice with a human-like bile acid composition.

Mice with deletion of Cyp2c70 have a human-like bile acid composition, display age- and sex-dependent signs of hepatobiliary disease and can be used as a model to study interactions between bile acids and the gut microbiota in cholestatic liver disease. In the present study, we rederived Cyp2c70-/- mice as germ-free (GF) and colonized them with a human or a mouse microbiota to investigate whether the presence of a microbiota can be protective in cholangiopathic liver disease associated with Cyp2c70-deficiency. GF Cyp2c70-/- mice showed reduced neonatal survival, liver fibrosis, and distinct cholangiocyte proliferation. Colonization of germ-free breeding pairs with a human or a mouse microbiota normalized neonatal survival of the offspring, and particularly colonization with mouse microbiota from a conventionally raised mouse improved the liver phenotype at 6-10 weeks of age. The improved liver phenotype in conventionalized (CD) Cyp2c70-/- mice was associated with increased levels of tauro-ursodeoxycholic acid (TUDCA) and UDCA, resulting in a more hydrophilic bile acid profile compared with GF and humanized Cyp2c70-/- mice. The hydrophobicity index of biliary bile acids of CD Cyp2c70-/- mice was associated with changes in gut microbiota, liver weight, liver transaminases, and liver fibrosis. Hence, our results indicate that neonatal survival of Cyp2c70-/- mice seems to depend on the establishment of a gut microbiota at birth, and the improved liver phenotype in CD Cyp2c70-/- mice may be mediated by a larger proportion of TUDCA/UDCA in the circulating bile acid pool and/or by the presence of specific bacteria.

Feasibility, Acceptability, and Safety of Faecal Microbiota Transplantation in the Treatment of Major Depressive Disorder: A Pilot Randomized Controlled Trial.

OBJECTIVES: Perturbations of the intestinal microbiota have been associated with mental health disorders, including major depressive disorder (MDD). Therefore, faecal microbiota transplantation (FMT) holds promise as a microbiota-modulating treatment for MDD. Yet, to date, there are no published controlled studies evaluating the use of FMT for MDD. This study aimed to address this gap by evaluating the feasibility, acceptability, and safety of FMT for MDD. METHODS: The study was an 8-week, double-blind, 2:1 parallel group, randomized controlled pilot trial (n = 15) of enema-delivered FMT (n = 10) compared with a placebo enema (n = 5) in adults with moderate-to-severe MDD. RESULTS: Recruitment was completed within 2 months, with 0% attrition and 100% attendance at key study appointments. There were no major protocol deviations. The placebo and blinding strategies were considered successful; nurses and participants correctly guessing their treatment allocation at a rate similar to that anticipated by chance. No serious or severe adverse events were reported in either group, and there were no significant differences in mild-to-moderate adverse events between groups (median of 2 adverse events per participant reported in both groups). Furthermore, the 12/15 participants who completed the Week 2 participant satisfaction survey agreed or strongly agreed that the enema delivery was tolerable and that they would have the treatment again if required. Whilst the study was not designed to measure clinical outcomes, exploratory data also suggested that the active FMT treatment may lead to improvements in gastrointestinal symptoms and quality of life in this population, noting that irritable bowel syndrome is commonly comorbid with MDD. CONCLUSIONS: All feasibility targets were met or exceeded. This study found that enema-delivered FMT is feasible, acceptable, well-tolerated, and safe in patients with MDD. The findings of this study support further research to evaluate clinical efficacy, and the use of this protocol is supported.

Exploring the complex and multifaceted interplay of the gut microbiome and cancer prevention and therapy.

Recent scientific research has indicated that the gut microbiota constitutes a nuanced, diverse ecosystem of microorganisms that have gained significant attention due to its crucial involvement in shaping human health and diseases. In particular, the gut microbiota plays a pivotal role in cancer prevention, and disturbances in its composition and function, known as dysbiosis, that have been linked to an increased risk of developing various malignancies. The gut microbiota exerts a myriad of effects on the production of anti-cancer compounds, the host's immune system and inflammation, underscoring its crucial involvement in cancer. Additionally, recent studies have shown that the gut microbiota has a role in the development of cancer, influencing cancer risk, co-infections, disease progression, and treatment response. The observation of reduced efficacy of immunotherapy in patients receiving antibiotic treatment indicates a substantial influence of the microbiota in mediating the toxicity and response of cancer therapy, notably immunotherapy, and its immune-related side effects. A growing body of research has focused on cancer treatments that target the microbiome, including probiotics, dietary modifications, and faecal microbiota transplantation (FMT). The forthcoming era of personalised cancer therapies is anticipated to prioritise tumor evolution, molecular and phenotypic heterogeneity, and immunological profiling, with gut microbiota assuming a pivotal position in this domain. This review aims to offer clinicians a comprehensive perspective on the microbiota-cancer axis, including its influence on cancer prevention and therapy and highlights the importance of integrating microbiome science into the design and implementation of cancer therapies.

Alkylresorcinols as New Modulators of the Metabolic Activity of the Gut Microbiota.

Alkylresorcinols (ARs) are polyphenolic compounds with a wide spectrum of biological activities and are potentially involved in the regulation of host metabolism. The present study aims to establish whether ARs can be produced by the human gut microbiota and to evaluate alterations in content in stool samples as well as metabolic activity of the gut microbiota of C57BL, db/db, and LDLR (-/-) mice according to diet specifications and olivetol (5-n-pentylresorcinol) supplementation to estimate the regulatory potential of ARs. Gas chromatography with mass spectrometric detection was used to quantitatively analyse AR levels in mouse stool samples; faecal microbiota transplantation (FMT) from human donors to germ-free mice was performed to determine whether the intestinal microbiota could produce AR molecules; metagenome sequencing analysis of the mouse gut microbiota followed by reconstruction of its metabolic activity was performed to investigate olivetol's regulatory potential. A significant increase in the amounts of individual members of AR homologues in stool samples was revealed 14 days after FMT. Supplementation of 5-n-Pentylresorcinol to a regular diet influences the amounts of several ARs in the stool of C57BL/6 and LDLR (-/-) but not db/db mice, and caused a significant change in the predicted metabolic activity of the intestinal microbiota of C57BL/6 and LDLR (-/-) but not db/db mice. For the first time, we have shown that several ARs can be produced by the intestinal microbiota. Taking into account the dependence of AR levels in the gut on olivetol supplementation and microbiota metabolic activity, AR can be assumed to be potential quorum-sensing molecules, which also influence gut microbiota composition and host metabolism.

Faecal Microbiota Transplantation, Paving the Way to Treat Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is currently the most prevalent cause of chronic liver disease (CLD). Currently, the only therapeutic recommendation available is a lifestyle change. However, adherence to this approach is often difficult to guarantee. Alteration of the microbiota and an increase in intestinal permeability seem to be key in the development and progression of NAFLD. Therefore, the manipulation of microbiota seems to provide a promising therapeutic strategy. One way to do so is through faecal microbiota transplantation (FMT). Here, we summarize the key aspects of FMT, detail its current indications and highlight the most recent advances in NAFLD.

Microbiomes in physiology: insights into 21st-century global medical challenges.

NEW FINDINGS: What is the topic of this review? The role of the gut microbiome in physiology and how it can be targeted as an effective strategy against two of the most important global medical challenges of our time, namely, metabolic diseases and antibacterial resistance. What advances does it highlight? The critical roles of the microbiome in regulating host physiology and how microbiome analysis is useful for disease stratification to enable informed clinical decisions and develop interventions such as faecal microbiota transplantation, prebiotics and probiotics. Also, the limitations of microbiome modulation, including the potential for probiotics to enhance antimicrobial resistance gene reservoirs, and that currently a 'healthy microbiome' that can be used as a biobank for transplantation is yet to be defined. ABSTRACT: The human gut microbiome is a key factor in the development of metabolic diseases and antimicrobial resistance, which are among the greatest global medical challenges of the 21st century. A recent symposium aimed to highlight state-of-the-art evidence for the role of the gut microbiome in physiology, from childhood to adulthood, and the impact this has on global disease outcomes, ageing and antimicrobial resistance. Although the gut microbiome is established early in life, over time the microbiome and its components including metabolites can become perturbed due to changes such as dietary habits, use of antibiotics and age. As gut microbial metabolites, including short-chain fatty acids, secondary bile acids and trimethylamine-N-oxide, can interact with host receptors including G protein-coupled receptors and can alter host metabolic fluxes, they can significantly affect physiological homoeostasis leading to metabolic diseases. These metabolites can be used to stratify disease phenotypes such as irritable bowel syndrome and adverse events after heart failure and allow informed decisions on clinical management and treatment. While strategies such as use of probiotics, prebiotics and faecal microbiota transplantation have been proposed as interventions to treat and prevent metabolic diseases and antimicrobial resistance, caution must be exercised, first due to the potential of probiotics to enhance antimicrobial resistance gene reservoirs, and second, a 'healthy gut microbiome' that can be used as a biobank for transplantation is yet to be defined. We highlight that sampling other parts of the gastrointestinal tract may produce more representative data than the faecal microbiome alone.

The gut microbiome modulates nitroglycerin-induced migraine-related hyperalgesia in mice.

BACKGROUND: Gut microbiota disturbance is increasingly suggested to be involved in the pathogenesis of migraine but this connection remains unsubstantiated. This study aimed to investigate whether the gut microbiome influences migraine-related hyperalgesia. METHODS: Nitroglycerin-induced hyperalgesia was evaluated in mice with different gut microbiota statuses as follows: Specific pathogen-free mice; germ-free mice; specific pathogen-free mice treated with antibiotics to deplete the gut microbiome (ABX mice); and germ-free mice transplanted with the gut microbial profile from specific pathogen-free mice (GFC mice). Moreover, nitroglycerin-induced hyperalgesia was compared between recipient mice transplanted with gut microbiota from a patient with migraine and those that received gut microbiota from a sex- and age-matched healthy control. RESULTS: In specific pathogen-free mice, a decreased mechanical threshold in the hind paw, increased grooming time, increased c-Fos expression level and decreased calcitonin gene-related peptide expression level as well as increased tumor necrosis factor-α concentration in the trigeminal nucleus caudalis were observed after nitroglycerin administration compared with saline treatment. However, increased basal sensitivity and higher basal concentrations of TNF-α in the trigeminal nucleus caudalis were observed in germ-free and ABX mice, while no significant difference in hyperalgesia was observed between the nitroglycerin group and saline group in germ-free and ABX mice. Moreover, significant hyperalgesia was induced by nitroglycerin administration in GFC mice. The mice transplanted with the gut microbial profile from a patient with migraine had more severe nitroglycerin-induced hyperalgesia than the mice receiving microbiota from a matched healthy control. CONCLUSION: Our findings highlight the involvement of the gut microbiome in normal mechanical pain sensation and pathogenesis of migraine.

The role of gut dysbiosis in Parkinson's disease: mechanistic insights and therapeutic options.

Parkinson's disease is a common neurodegenerative disorder in which gastrointestinal symptoms may appear prior to motor symptoms. The gut microbiota of patients with Parkinson's disease shows unique changes, which may be used as early biomarkers of disease. Alterations in the gut microbiota composition may be related to the cause or effect of motor or non-motor symptoms, but the specific pathogenic mechanisms are unclear. The gut microbiota and its metabolites have been suggested to be involved in the pathogenesis of Parkinson's disease by regulating neuroinflammation, barrier function and neurotransmitter activity. There is bidirectional communication between the enteric nervous system and the CNS, and the microbiota-gut-brain axis may provide a pathway for the transmission of α-synuclein. We highlight recent discoveries about alterations to the gut microbiota in Parkinson's disease and focus on current mechanistic insights into the microbiota-gut-brain axis in disease pathophysiology. Moreover, we discuss the interactions between the production and transmission of α-synuclein and gut inflammation and neuroinflammation. In addition, we draw attention to diet modification, the use of probiotics and prebiotics and faecal microbiota transplantation as potential therapeutic approaches that may lead to a new treatment paradigm for Parkinson's disease.