Gut microbiota-derived succinate: Friend or foe in human metabolic diseases?

Host-microbe multi-omics and succinotype profiling have prognostic value for future relapse in patients with inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are chronic relapsing inflammatory bowel disorders (IBD), the pathogenesis of which is uncertain but includes genetic susceptibility factors, immune-mediated tissue injury and environmental influences, most of which appear to act via the gut microbiome. We hypothesized that host-microbe alterations could be used to prognostically stratify patients experiencing relapses up to four years after endoscopy. We therefore examined multiple omics data, including published and new datasets, generated from paired inflamed and non-inflamed mucosal biopsies from 142 patients with IBD (54 CD; 88 UC) and from 34 control (non-diseased) biopsies. The relapse-predictive potential of 16S rRNA gene and transcript amplicons (standing and active microbiota) were investigated along with host transcriptomics, epigenomics and genetics. While standard single-omics analysis could not distinguish between patients who relapsed and those that remained in remission within four years of colonoscopy, we did find an association between the number of flares and a patient's succinotype. Our multi-omics machine learning approach was also able to predict relapse when combining features from the microbiome and human host. Therefore multi-omics, rather than single omics, better predicts relapse within 4 years of colonoscopy, while a patient's succinotype is associated with a higher frequency of relapses.

The impact of gut microbial short-chain fatty acids on colorectal cancer development and prevention

Cancer is a long-term illness that involves an imbalance in cellular and immune functions. It can be caused by a range of factors, including exposure to environmental carcinogens, poor diet, infections, and genetic alterations. Maintaining a healthy gut microbiome is crucial for overall health, and short-chain fatty acids (SCFAs) produced by gut microbiota play a vital role in this process. Recent research has established that alterations in the gut microbiome led to decreased production of SCFA's in lumen of the colon, which associated with changes in the intestinal epithelial barrier function, and immunity, are closely linked to colorectal cancer (CRC) development and its progression. SCFAs influence cancer progression by modifying epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNA functions thereby affecting tumor initiation and metastasis. This suggests that restoring SCFA levels in colon through microbiota modulation could serve as an innovative strategy for CRC prevention and treatment. This review highlights the critical relationship between gut microbiota and CRC, emphasizing the potential of targeting SCFAs to enhance gut health and reduce CRC risk.

Patient-derived pancreatic tumor bacteria exhibit oncogenic properties and are recognized by MAIT cells in tumor spheroids

Introduction

Tumor-residing microbiota poses a new challenge in cancer progression and therapy; however, the functional behavior of patient tumor-derived microbes remains poorly understood. We previously reported the presence of tumor microbiota in intraductal papillary mucinous neoplasms (IPMNs), which are precursors of pancreatic cancer.

Methods

We examined the metabolic and pathogenic potential of clinical microbiota strains obtained from IPMN tumors using various pancreatic cell lines and 3D spheroid models.

Results

Our findings revealed that several strains from IPMNs with invasive cancer or high-grade dysplasia, such as E. cloacae, E. faecalis, and K. pneumoniae, induced a cancer metabolite signature in human pancreatic cells when infected ex vivo. Bacterial invasiveness was significantly correlated with DNA damage in spheroids derived from normal and tumor-derived pancreatic cells, particularly in strains derived from advanced neoplasia IPMN and under hypoxic conditions. Additionally, microbial metabolites activate human mucosal-associated invariant T (MAIT) cells and restrict the infection, both extra- and intracellularly, in hypoxic tumor conditions and in synergy with antibiotics.

Discussion

Immune sensing of tumor microbiota metabolites may have clinical implications in cancer management.

Efficacy of a postbiotic and its components in promoting colonic transit and alleviating chronic constipation in humans and mice

This study evaluates the efficacy of the postbiotic Probio-Eco in alleviating constipation in humans and mice. A randomized, double-blind, placebo-controlled crossover trial involving 110 adults with chronic constipation (Rome IV criteria) demonstrates that a 3-week Probio-Eco intervention significantly improves constipation symptoms, stool straining, and worry scores. Gut microbiota and metabolomic analyses reveal modulations in specific gut microbiota, succinate, tryptophan derivatives, deoxycholate, propionate, butyrate, and cortisol, correlating with symptom relief. A loperamide-induced mouse model confirms that Probio-Eco and its bioactive components (succinate, 3-indoleacrylic acid, and 5-hydroxytryptophan) alleviate constipation by stimulating mucin-2 secretion, regulating intestinal transport hormones, and promoting anti-inflammatory responses. Multi-omics integration identifies key pathways, including succinate-short-chain fatty acid, tryptophan-5-hydroxytryptophan-serotonin, and tryptophan-3-indoleacrylic acid, driving intestinal homeostasis and motility. These findings highlight the comprehensive efficacy of Probio-Eco and provide robust evidence for its clinical application in constipation management. This study was registered at Chinese Clinical Trial Registry (ChiCTR2100054376).

Gut commensal bacterium Bacteroides vulgatus exacerbates helminth-induced cardiac fibrosis through succinate accumulation

Trichinella spiralis (Ts) is known to cause cardiac fibrosis, which is a critical precursor to various heart diseases, and its progression is influenced by metabolic changes. However, the metabolic mechanisms remain unclear. Here, we observed that Ts-infected mice exhibited cardiac fibrosis along with elevated succinate levels in the heart using metabolomic analysis. Administration of succinate exacerbated fibrosis during Ts infection, while deficiency in succinate receptor 1 (Sucnr1) alleviated the condition, highlighting the role of the succinate-Sucnr1 axis in fibrosis development. Furthermore, metagenomics sequencing showed that Ts-infected mice had a higher abundance ratio of succinate-producing bacteria to succinate-consuming bacteria in the intestines. Notably, the succinate-producer Bacteroides vulgatus was enriched in Ts group. Oral supplementation with B. vulgatus aggravated Ts-induced cardiac fibrosis. In summary, our findings underscore the succinate-Sucnr1 axis as a critical pathway in helminth-induced cardiac fibrosis and highlight the potential of targeting this axis for therapeutic interventions. This study presents novel insights into the gut-heart axis, revealing innovative strategies for managing cardiovascular complications associated with helminth infections.

Succinate receptor 1 signaling mutually depends on subcellular localization and cellular metabolism

Succinate is a pivotal tricarboxylic acid cycle metabolite but also specifically activates the Gi- and Gq-coupled succinate receptor 1 (SUCNR1). Contradictory roles of succinate and succinate-SUCNR1 signaling include reports about its anti- or pro-inflammatory effects. The link between cellular metabolism and localization-dependent SUCNR1 signaling qualifies as a potential cause for the reported conflicts. To systematically address this connection, we used a diverse set of methods, including several bioluminescence resonance energy transfer-based biosensors, dynamic mass redistribution measurements, second messenger and kinase phosphorylation assays, calcium imaging, and metabolic analyses. Different cellular metabolic states were mimicked using glucose (Glc) or glutamine (Gln) as available energy substrates to provoke differential endogenous succinate (SUC) production. We show that SUCNR1 signaling, localization, and metabolism are mutually dependent, with SUCNR1 showing distinct spatial and energy substrate-dependent Gi and Gq protein activation. We found that Gln-consumption associated with a higher rate of oxidative phosphorylation causes increased extracellular SUC concentrations, accompanied by a higher rate of SUCNR1 internalization, reduced miniGq protein recruitment to the plasma membrane, and lower Ca2+ signals. In Glc, under basal conditions, SUCNR1 causes stronger Gq than Gi protein activation, while the opposite is true upon stimulation with an agonist. In addition, SUCNR1 specifically interacts with miniG proteins in endosomal compartments. In THP-1 cells, polarized to M2-like macrophages, endogenous SUCNR1-mediated Gi signaling stimulates glycolysis, while Gq signaling inhibits the glycolytic rate. Our results suggest that the metabolic context determines spatially dependent SUCNR1 signaling, which in turn modulates cellular energy homeostasis and mediates adaptations to changes in SUC concentrations.

Succinate predisposes mice to atrial fibrillation by impairing mitochondrial function via SUCNR1/AMPK axis

Atrial fibrillation (AF), a major public health concern, is associated with high rates of death and disability. Mitochondrial dysfunction has emerged as a key contributor to the pathophysiology of AF. Succinate, an essential Krebs cycle metabolite, is often elevated in the circulation of patients at risk for AF. However, its exact role in AF pathogenesis is still not well understood. To explore the association linking succinate overload and AF, we first established AF-susceptible mouse models of obesity and diabetes, confirming that circulating succinate levels were significantly elevated in these AF-prone mice. Next, we assessed AF vulnerability and atrial remodeling in succinate-treated mice (2 %/5 % for 7 weeks) or isolated primary atrial cells (0.5 mM for 24 h). Our results demonstrated that succinate overload increased AF susceptibility in mice and triggered adverse atrial remodeling, characterized by left atrial dilation, connexins lateralization, ion channel disturbances, and fibrosis. Moreover, succinate compromised atrial mitochondrial structure, leading to increased oxidative stress. Mechanistically, succinate overload upregulated the expression of its cognate receptor SUCNR1 (succinate receptor 1) and decreased AMPK (AMP-activated protein kinase) phosphorylation both in vitro and in vivo. AICAR (AMPK activator) maintained mitochondrial health to mitigate remodeling in succinate-exposed cells and prevented succinate-induced AF in obese and diabetic mice. In conclusion, succinate overload enhances AF vulnerability and atrial remodeling by impairing AMPK signaling and mitochondrial function. Succinate, therefore, represents an underappreciated contributor to AF pathogenesis and a potential biomarker.

Impaired angiogenesis in gestational diabetes is linked to succinate/SUCNR1 axis dysregulation in late gestation

Recent research has highlighted the significance of succinate and its receptor in gestational diabetes (GDM) pathogenesis. However, a clear interconnection between placenta metabolism, succinate levels, SUCNR1 signalling and pregnancy pathologies remains elusive. Here, we set out to investigate the potential role of succinate on labour and placental mechanisms by combining clinical and functional experimental data at the same time as exploring the specific SUCNR1-mediated effects of succinate on placenta vascularization, addressing its specific agonist actions. According to our data, succinate levels vary throughout pregnancy and postpartum, with a natural increase during the peripartum period. We also show that SUCNR1 activation in the umbilical cord endothelium promotes angiogenesis under normal conditions. However, in GDM, excessive succinate and impaired SUCNR1 function may weaken this angiogenic response. In conclusion, the present study underlines succinate as an emerging signalling molecule in the placenta, regulating labour and placental processes. The reduced sensitivity of the succinate/SUCNR1 pathway in the GDM environment may serve as a protective physiological mechanism or could have a pathogenic effect. KEY POINTS: Succinate levels increase at delivery in maternal and fetal circulation. Gestational diabetes (GDM) induces succinate accumulation and SUCNR1 downregulation in umbilical cords. GDM compromises angiogenic gene profile modulation by SUCNR1 in umbilical cord endothelium. SUCNR1 activation stimulates sprouting and tube-forming capacity of human umbilical vein endothelial cells from healthy, but not GDM pregnancies.

The role of microbial succinate in the pathophysiology of inflammatory bowel disease: mechanisms and therapeutic potential

Inflammatory bowel disease (IBD) is a chronic immune-mediated condition linked to gut microbiota dysbiosis and altered production of bacterial metabolites, including succinate, which is also a key intermediate in human mitochondrial energy metabolism in human cells. Succinate levels in the gut are influenced by microbial community dynamics and cross-feeding interactions, highlighting its dual metabolic and ecological importance. Extracellular succinate acts as a key signaling metabolite linking microbial metabolism to host physiology, with transient rises supporting metabolic regulation but chronic elevations contributing to metabolic disorders and disease progression. Succinate signals through its cognate receptor SUCNR1, which mediates adaptive metabolic responses under normal conditions but drives inflammation and fibrosis when dysregulated. IBD patients display a dysbiotic gut microbiota characterized by an increased prevalence of succinate-producing bacteria, contributing to elevated succinate levels in the gut and circulation. This imbalance drives inflammation, worsens IBD severity, and contributes to complications like Clostridioides difficile infection and fibrosis. Emerging evidence highlights the potential of intestinal and systemic succinate levels as indicators of microbial dysbiosis, with a bidirectional relationship between microbial composition and succinate metabolism. Understanding the factors influencing succinate levels and their interaction with dysbiosis shows promise in the development of therapeutic strategies to restore microbial balance. Approaches such as dietary fiber enrichment, prebiotics, and probiotics to enhance succinate-consuming bacteria, combined with targeted modulation of succinate pathways (e.g. SDH inhibitors, SUCNR1 antagonists), hold promise for mitigating inflammation and improving gut health in IBD.

Almond snacking modulates gut microbiome and metabolome in association with improved cardiometabolic and inflammatory markers

Western-style dietary patterns have been linked with obesity and associated metabolic disorders and gut dysbiosis, whereas prudent dietary and snacking choices mitigate these predispositions. Using a multi-omics approach, we investigated how almond snacking counters gut imbalances linked to adiposity and an average American Diet (AAD). Fifteen adults with overweight or obesity underwent a randomized, crossover-controlled feeding trial comparing a 4-week AAD with a similar isocaloric diet supplemented with 42.5 g/day of almonds (ALD). Almond snacking increases functional gut microbes, including Faecalibacterium prausnitzii, while suppressing opportunistic pathogens, thereby favorably modulating gut microecological niches through symbiotic and microbe-metabolite interactions. Moreover, ALD elevates health-beneficial monosaccharides and fosters bacterial consumption of amino acids, owing to enhanced microbial homeostasis. Additionally, ALD enhances metabolic homeostasis through a ketosis-like effect, reduces inflammation, and improves satiety-regulating hormones. The findings suggest that prudent dietary choices, such as almond snacking, promote gut microbial homeostasis while modulating immune metabolic state.

SUCNR1 Deficiency Alleviates Liver Ischemia-Reperfusion Injury by Regulating Kupffer Cell Activation and Polarization Through the ERK/NF-κB Pathway in Mice

Succinate regulates inflammation through its receptor, succinate receptor 1 (SUCNR1). However, the effects of this interaction on Kupffer cell (KC)-driven inflammation during liver ischemia-reperfusion injury (IRI) remain unclear. Herein, we investigated the succinate/SUCNR1 axis in the progression of liver IRI. In this study, succinate levels and SUCNR1 expression were analyzed in mice underwent segmental liver IRI. Sucnr1 deficiency (Sucnr1-/-) and Wild-type mice were treated with or without clodronate before liver IRI modeling, and a co-culture system was established to assess the impact of Sucnr1 deficiency in KCs on hepatocyte viability and apoptosis. KC activation status and polarization were determined, in vivo and in vitro. Furthermore, the downstream pathways in regulating KC polarization were investigated. We observed a significant increase in succinate levels in the serum and liver, and SUCNR1 expression in KCs after IRI. Sucnr1 deletion alleviated liver IRI and hepatocyte apoptosis either in vivo or in vitro. However, the aforementioned hepatoprotective effects were abolished by the depletion of KCs with clodronate. Sucnr1 deletion inhibited KC activation and M1 polarization, and dampened proinflammatory cytokine release after liver IRI. In addition, Sucnr1 knockout reversed the increasing phosphorylation of ERK and NF-κB p65 in KCs following liver IRI. The phosphorylation of ERK/NF-κB p65 and M1 polarization in KCs were also inhibited by the SUCNR1 antagonist Compound 4C or ERK inhibitor SCH772984. Together, these findings suggest that SUCNR1 deficiency protects against liver IRI by modulating KC activation and polarization probably through the ERK/NF-κB pathway.

Gut commensals-derived succinate impels colonic inflammation in ulcerative colitis

Gut microbiota-derived metabolites play a crucial role in modulating the inflammatory response in inflammatory bowel disease (IBD). In this study, we identify gut microbiota-derived succinate as a driver of inflammation in ulcerative colitis (UC) by activating succinate-responsive, colitogenic helper T (Th) cells that secrete interleukin (IL)-9. We demonstrate that colitis is associated with an increase in succinate-producing gut bacteria and decrease in succinate-metabolizing gut bacteria. Similarly, UC patients exhibit elevated levels of succinate-producing gut bacteria and luminal succinate. Intestinal colonization by succinate-producing gut bacteria or increased succinate availability, exacerbates colonic inflammation by activating colitogenic Th9 cells. In contrast, intestinal colonization by succinate-metabolizing gut bacteria, blocking succinate receptor signaling with an antagonist, or neutralizing IL-9 with an anti-IL-9 antibody alleviates inflammation by reducing colitogenic Th9 cells. Our findings underscore the role of gut microbiota-derived succinate in driving colitogenic Th9 cells and suggesting its potential as a therapeutic target for treating IBD.

Isomaltodextrin inhibits kidney enlargement induced by a high-protein diet through its metabolism by gut microbiota

To evaluate the effects of the soluble fiber isomaltodextrin in a protein-biased diet, a 21-day protein diet trial was conducted in rats, with 60% of the calories derived from protein. The results revealed that the high-protein diet alone led to a significant increase in kidney weight. In contrast, the consumption of water with 5% isomaltodextrin dissolved in it, along with a high-protein diet, suppressed this weight gain. To elucidate this mechanism, an analysis of serum urea toxins confirmed that the concentrations of phenyl sulfate were significantly higher with high protein, and significantly lower with isomaltodextrin. The impact of a high-protein diet increased phenol in cecal contents, an increase that was mitigated by isomaltodextrin. This suggests that the inhibitory effect of isomaltodextrin on renal hypertrophy was due to the suppression of urea toxin precursor production by the gut microbiota.

Maternal obesity, age and infant sex influence the profiles of amino acids, energetic metabolites, sugars, and fatty acids in human milk

PURPOSE

This study aimed to evaluate whether maternal nutritional status, maternal age, mode of delivery, and the infant's sex influence the profiles of amino acids, energetic metabolites, sugars, and fatty acids and as well as the metabolic pathways in mature human milk human milk (HM).

METHODS

This was a cross-sectional, prospective, and observational study. HM samples from normal weight (NW, n = 60), overweight (OW, n = 35), and obese (OB, n = 14) women were analyzed using a non-targeted GC-MS method to identify the metabolome. Data obtained were analyzed with Metaboanalyst software (v. 5.0) and SPSS (v.25.0).

RESULTS

OB women HM contains a higher proportion of amino acids such as leucine, lysine, tyrosine, and aspartic acid, energy metabolites such as lactic and succinic acid, and sugars and derivatives such as fucose, rhamnose, and gluconic acid (p < 0.05) compared with normal weight women HM. HM from women > 25 years of age contains a lower proportion of lauric acid and a higher proportion of leucine and tyrosine (p < 0.05) than ≤ 25 years women HM. Also, HM intended for female infants has a higher leucine and gluconic acid content. The main altered metabolic pathways in OB women HM correspond to amino acids and energetic metabolism.

CONCLUSION

OB women HM provides more amino acids, energetic molecules, and sugars. Increased maternal weight, BMI, and body fat mass predispose to more leucine and aspartic acid in HM. Maternal age influences lauric acid, leucin, and tyrosine levels, while the infant's sex influences leucine and gluconic acid levels in HM. The impact of obese women's HM metabolome on the offspring's physiology needs to be explored.

TRIAL REGISTRATION

R-2021-785-096.

Complete genome sequence of Bifidobacterium animalis subsp. lactis BI040, a probiotic strain with multiple health benefits from the NORDBIOTIC collection

The complete genome of Bifidobacterium animalis subsp. lactis BI040-a human stool isolate, was sequenced using Illumina and Oxford Nanopore technologies. The BI040 genome is composed of a circular 1,944,141-bp chromosome which carries genes potentially involved in vitamin synthesis and gut health.

Disruption of Gut Microbiota and Associated Fecal Metabolites in Collagen-Induced Arthritis Mice During the Early Stage

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease and increasing evidence suggests that disturbances in the composition and function of gut microbiota are potentially implicated in the progression of RA. Further revealing the microbiota and related metabolic disorders in the preclinical stage of RA (pre-RA) is of great significance for exploration of disease mechanisms.

Methods

DBA/1 mice were injected with type II collagen on days 0 and 21 to establish collagen-induced arthritis (CIA) mouse model. Footpad thickness, serum autoantibodies, and joint histopathology were used to assess the progression of RA. A combination of 16S rRNA sequencing, untargeted metabolomics and targeted short-chain fatty acids (SCFAs) analysis were employed to comprehensively investigate the alterations of gut microbiota and fecal metabolites in CIA during the pre-RA stage.

Results

20 days after the initial collagen immunization, CIA mice showed immune responses without joint symptoms, alongside gut microbiota disruption. Alterations were observed in 20 microbial taxa, including Oscillospira, Bifidobacterium, Ruminococcus, Allobaculum, Alistipes, Lactobacillus, and Candidatus_Arthromitus, etc. Untargeted and targeted metabolomics identified 33 altered fecal metabolites, mainly including sugars and their derivatives, amino acids, long-chain fatty acids and SCFAs, etc. Correlation analysis showed significant correlations between specific gut microbial abundances and fecal metabolite levels. Especially, SCFAs were strongly associated with Bifidobacterium, Alistipes, Ruminococcus, Anaerotruncus, and Allobaculum.

Conclusion

These findings suggest that collagen immunization leads to disruption of gut microbiome and induces changes of fecal metabolites in mice, which may play a key role in early development of RA in CIA mice.

The gut microbiome modulate response to immunotherapy in cancer

Gut microbiota have been reported to play an important role in the occurrence and development of malignant tumors. Currently, clinical studies have identified specific gut microbiota and its metabolites associated with efficacy of immunotherapy in multiple types of cancers. Preclinical investigations have elucidated that gut microbiota modulate the antitumor immunity and affect the efficacy of cancer immunotherapy. Certain microbiota and its metabolites may favorably remodel the tumor microenvironment by engaging innate and/or adaptive immune cells. Understanding how the gut microbiome interacts with cancer immunotherapy opens new avenues for improving treatment strategies. Fecal microbial transplants, probiotics, dietary interventions, and other strategies targeting the microbiota have shown promise in preclinical studies to enhance the immunotherapy. Ongoing clinical trials are evaluating these approaches. This review presents the recent advancements in understanding the dynamic interplay among the host immunity, the microbiome, and cancer immunotherapy, as well as strategies for modulating the microbiome, with a view to translating into clinical applications.

Better objective sleep quality is associated with higher gut microbiota richness in older adults

Aging is associated with disrupted sleep patterns, such as fragmented sleep and reduced efficiency, leading to negative health outcomes. There is evidence of a bidirectional relationship between sleep and gut microbiota, which plays a key role in the gut-brain axis and overall health. However, studies on this relationship in older adults have limited generalizability and show conflicting results, highlighting the need for further research. This study aimed to investigate the associations between sleep quality and gut microbiota composition in healthy Chinese older adults using subjective and objective sleep measures to capture various aspects of sleep quality and explore potential impacts on emotional well-being and cognitive performance. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) questionnaire, while objective sleep quality was measured with actigraphy. Gut microbiota sequencing was performed on stool samples. The results show a robust positive association between gut microbiota richness and objective sleep quality in older adults, independent of subjective sleep quality and demographics, lifestyle, and health covariates. However, no significant link was found between gut microbiota richness and subjective sleep quality. Specific taxa like Bacteroidetes, Ruminococcus, Collinsella, Veillonella, and Holdemania were tentatively linked to sleep quality. These findings emphasize the connection between sleep quality and gut microbiota composition in older adults with potential research and clinical implications, improving our understanding of the mechanisms underlying the sleep-gut microbiota relationship and guiding the development of interventions for improving both sleep quality and gut health in older adults.

Novel Fermented Plant-Based Functional Beverage: Biological Potential and Impact on the Human Gut Microbiota

Controlled fermentation carried out by selected starters might enhance the safety, nutritional, and biological profiles of non-dairy fermented products. This research aims to study the biological potential and impact on the human gut microbiota of a novel fermented finger millet-based product. Finger millet (Eleusine coracana), suspended in an aqueous sucrose-based solution, was fermented by Weissella confusa 2LABPT05 and Lactiplantibacillus plantarum 299v (1%, 1:1 ratio (v/v)), at 30 °C/200 rpm in an orbital incubator until pH ≈ 4.5-5.0. Microbial growth, phenolic compounds, antioxidant, and antidiabetic activities were evaluated. In vitro digestion followed by in vitro faecal fermentation were used to study the impact of the fermented plant-based functional beverage (PBFB) on the human gut microbiota. Antidiabetic activity (21% vs. 14%) and total phenolics (244 vs. 181 mg of gallic acid equivalents/kg PBFB) increased with fermentation. The digested fermented PBFB contributed to the increase, over the first 6 h, of the Bifidobacterium's 16S rRNA gene copy numbers, concomitant with significant release of the acetic, propionic, and butyric short chain fatty acids, and also lactic acid. The novel PBFB has been shown to have antidiabetic potential and bifidogenic effects, and consequently its consumption might positively impact blood glucose levels and the human gut microbiota.

Antibiotic-mediated dysbiosis leads to activation of inflammatory pathways

Introduction

The gut microbiota plays a pivotal role in influencing host health, through the production of metabolites and other key signalling molecules. While the impact of specific metabolites or taxa on host cells is well-documented, the broader impact of a disrupted microbiota on immune homeostasis is less understood, which is particularly important in the context of the increasing overuse of antibiotics.

Methods

Female C57BL/6 mice were gavaged twice daily for four weeks with Vancomycin, Polymyxin B, or PBS (control). Caecal microbiota composition was assessed via 16S rRNA sequencing and caecal metabolites were quantified with NMR spectroscopy. Immune profiles of spleen and mesenteric lymph nodes (MLNs) were assessed by flow cytometry, and splenocytes assessed for ex vivo cytokine production. A generalised additive model approach was used to examine the relationship between global antibiotic consumption and IBD incidence.

Results

Antibiotics significantly altered gut microbiota composition, reducing alpha-diversity. Acetate and butyrate were significantly reduced in antibiotic groups, while propionate and succinate increased in Vancomycin and PmB-treated mice, respectively. The MLNs and spleen showed changes only to DC numbers. Splenocytes from antibiotic-treated mice stimulated ex vivo exhibited increased production of TNF. Epidemiological analysis revealed a positive correlation between global antibiotic consumption and IBD incidence.

Discussion

Our findings demonstrate that antibiotic-mediated dysbiosis results in significantly altered short-chain fatty acid levels but immune homeostasis in spleen and MLNs at steady state is mostly preserved. Non-specific activation of splenocytes ex vivo, however, revealed mice with perturbed microbiota had significantly elevated production of TNF. Thus, this highlights antibiotic-mediated disruption of the gut microbiota may program the host towards dysregulated immune responses, predisposing to the development of TNF-associated autoimmune or chronic inflammatory disease.

Succinate-producing microbiota drives tuft cell hyperplasia to protect against Clostridioides difficile

The role of microbes and their metabolites in modulating tuft cell (TC) dynamics in the large intestine and the relevance of this pathway to infections is unknown. Here, we uncover that microbiome-driven colonic TC hyperplasia protects against Clostridioides difficile infection. Using selective antibiotics, we demonstrate increased type 2 cytokines and TC hyperplasia in the colon but not in the ileum. We demonstrate the causal role of the microbiome in modulating this phenotype using fecal matter transplantation and administration of consortia of succinate-producing bacteria. Administration of succinate production-deficient microbes shows a reduced response in a Pou2f3-dependent manner despite similar intestinal colonization. Finally, antibiotic-treated mice prophylactically administered with succinate-producing bacteria show increased protection against C. difficile-induced morbidity and mortality. This effect is nullified in Pou2f3-/- mice, confirming that the protection occurs via the TC pathway. We propose that activation of TCs by the microbiota in the colon is a mechanism evolved by the host to counterbalance microbiome-derived cues that facilitate invasion by pathogens.

Nurturing development: how a mother's nutrition shapes offspring's brain through the gut

Pregnancy is a transformative period marked by profound physical and emotional changes, with far-reaching consequences for both mother and child. Emerging research has illustrated the pivotal role of a mother's diet during pregnancy in influencing the prenatal gut microbiome and subsequently shaping the neurodevelopment of her offspring. The intricate interplay between maternal gut health, nutrition, and neurodevelopmental outcomes has emerged as a captivating field of investigation within developmental science. Acting as a dynamic bridge between mother and fetus, the maternal gut microbiome, directly and indirectly, impacts the offspring's neurodevelopment through diverse pathways. This comprehensive review delves into a spectrum of studies, clarifying putative mechanisms through which maternal nutrition, by modulating the gut microbiota, orchestrates the early stages of brain development. Drawing insights from animal models and human cohorts, this work underscores the profound implications of maternal gut health for neurodevelopmental trajectories and offers a glimpse into the formulation of targeted interventions able to optimize the health of both mother and offspring. The prospect of tailored dietary recommendations for expectant mothers emerges as a promising and accessible intervention to foster the growth of beneficial gut bacteria, potentially leading to enhanced cognitive outcomes and reduced risks of neurodevelopmental disorders.

Urinary Metabolite Profiles of Participants with Overweight and Obesity Prescribed a Weight Loss High Fruit and Vegetable Diet: A Single Arm Intervention Study

BACKGROUND/OBJECTIVES

Thus far, no studies have examined the relationship between fruit and vegetable (F and V) intake, urinary metabolite quantities, and weight change. Therefore, the aim of the current study was to explore changes in urinary metabolomic profiles during and after a 10-week weight loss intervention where participants were prescribed a high F and V diet (7 servings daily).

METHODS

Adults with overweight and obesity (n = 34) received medical nutrition therapy counselling to increase their F and V intakes to national targets (7 servings a day). Data collection included weight, dietary intake, and urine samples at baseline at week 2 and week 10. Urinary metabolite profiles were quantified using 1H NMR spectroscopy. Machine learning statistical approaches were employed to identify novel urine-based metabolite biomarkers associated with high F and V diet patterns at weeks 2 and 10. Metabolic changes appearing in urine in response to diet were quantified using Metabolite Set Enrichment Analysis (MSEA).

RESULTS

Energy intake was significantly lower (p = 0.02) at week 10 compared with baseline. Total F and V intake was significantly higher at week 2 and week 10 (p < 0.05). In total, 123 urinary metabolites were quantified. At week 10, 21 metabolites showed significant changes relative to baseline. Of these, 11 metabolites also significantly changed at week 2. These overlapping metabolites were acetic acid, dimethylamine, choline, fumaric acid, glutamic acid, L-tyrosine, histidine, succinic acid, uracil, histamine, and 2-hydroxyglutarate. Ridge Classifier and Linear Discriminant Analysis provided best prediction accuracy values of 0.96 when metabolite level of baseline was compared to week 10.

CONCLUSIONS

Urinary metabolites quantified represent potential candidate biomarkers of high F and V intake, associated with a reduction in energy intake. Further studies are needed to validate these findings in larger population studies.

Phenyllactic acid modulates the gut microbiota, enhances intestinal health, and alleviates physical frailty in aging mice

Phenyllactic acid (PLA) is a natural antibiotic-like compound derived from certain foods and probiotics. PLA levels have been associated with age-related sarcopenia and provide benefits to metabolic health when derived from probiotics. However, the specific regulatory effects of PLA in aging remain largely unexplored. In this study, aging mice were administered PLA via gavage, followed by fecal 16S rRNA sequencing, measurements of targeted metabolites, glucose metabolism monitoring, and physical performance assessments. Our results indicate that PLA administration significantly altered gut microbiota composition, increased the abundance of short-chain fatty acids (SCFAs) and succinate producing microbiota, and enhanced gut integrity in aging mice. Furthermore, PLA treatment raised fasting blood glucose levels and improved physical activity. Mechanistically, PLA intake elevated the levels of circulating SCFAs and succinate, promoting glycogen metabolic homeostasis and maintaining skeletal muscle oxidative capacity. This study provides evidence that PLA modulates the gut microbiota in aging mice, supports intestinal health, promotes glucose homeostasis, and enhances physical activity.

Racial-Ethnic Disparities of Obesity Require Community Context-Specific Biomedical Research for Native Hawaiians and Other Pacific Islanders

Compared to the general population of Hawai'i, Native Hawaiians and Other Pacific Islanders (NHPI) shoulder a disproportionately high risk for obesity-related cardiometabolic disorders, such as type 2 diabetes and cardiovascular disease. The gut microbiome is an area of rapid research interest for its role in regulating adjacent metabolic pathways, offering novel opportunities to better understand the etiology of these health disparities. Obesity and the gut microbiome are influenced by regional, racial-ethnic, and community-specific factors, limiting the generalizability of current literature for understudied populations. Additionally, anthropometric and directly measured obesity indices are variably predictive of adiposity and metabolic health risk in this diverse population. Thus, further NHPI-inclusive research is required to adequately characterize community-specific factors in the context of obesity-related disease etiology. Culturally responsible research ethics and scientific communication are crucial to conducting such research, especially among indigenous and understudied populations. In this review, we explore these limitations in current literature, emphasizing the urgent need for NHPI-inclusive research to assess community-specific factors accurately. Such accuracy in Indigenous health research may ensure that findings relevant to individual or public health recommendations and/or policies are meaningful to the communities such research aims to serve.

Analysis of early childhood intestinal microbial dynamics in a continuous-flow bioreactor

BACKGROUND

The human gut microbiota is inoculated at birth and undergoes a process of assembly and diversification during the first few years of life. Studies in mice and humans have revealed associations between the early-life gut microbiome and future susceptibility to immune and metabolic diseases. To resolve microbe and host contributing factors to early-life development and to disease states requires experimental platforms that support reproducible, longitudinal, and high-content analyses.

RESULTS

Here, we deployed a continuous single-stage chemostat culture model of the human distal gut to study gut microbiota from 18- to 24-month-old children integrating both culture-dependent and -independent methods. Chemostat cultures recapitulated multiple aspects of the fecal microbial ecosystem enabling investigation of relationships between bacterial strains and metabolic function, as well as a resource from which we isolated and curated a diverse library of early life bacterial strains.

CONCLUSIONS

We report the reproducible, longitudinal dynamics of early-life bacterial communities cultured in an advanced model of the human gut providing an experimental approach and a characterized bacterial resource to support future investigations of the human gut microbiota in early childhood.

The Influence of Protein Secretomes of Enterococcus durans on ex vivo Human Gut Microbiome

The gut microbiome plays a critical role to all animals and humans health. Methods based on ex vivo cultures are time and cost-effective solutions for rapid evaluation of probiotic effects on microbiomes. In this study, we assessed whether the protein secretome from the potential probiotic Enterococcus durans LAB18S grown on fructoligosaccharides (FOS) and galactoligosaccharides (GOS) had specific effects on ex vivo cultured intestinal microbiome obtained from a healthy individual. Metaproteomics was used to evaluate changes in microbial communities of the human intestinal microbiome. Hierarchical clustering analysis revealed 654 differentially abundant proteins from the metaproteome samples, showing that gut microbial protein expression varied on the presence of different E. durans secretomes. Increased amount of Bacteroidetes phylum was observed in treatments with secretomes from E. durans cultures on FOS, GOS and albumin, resulting in a decrease of the Firmicutes to Bacteroidetes (F/B) ratio. The most functionally abundant bacterial taxa were Roseburia, Bacteroides, Alistipes and Faecalibacterium. The results suggest that the secretome of E. durans may have favorable effects on the intestinal microbial composition, stimulating growth and different protein expression of beneficial bacteria. These findings suggest that proteins secreted by E. durans growing on FOS and GOS have different effects on the modulation of gut microbiota functional activities during cultivation.

Succinate exacerbates mastitis in mice via extracellular vesicles derived from the gut microbiota: a potential new mechanism for mastitis

BACKGROUND

A high grain diet causes an ecological imbalance in the gut microbiota and serves as an important endogenous trigger of mastitis in dairy cows, but the underlying mechanisms are unclear. Our previous study revealed that subacute rumen acidosis (SARA)-associated mastitis has distinct metabolic profiles in the rumen, especially a significant increase in succinate, but the role of succinate in the pathogenesis of mastitis remains unclear.

RESULTS

Succinate treatment exacerbates low-grade endotoxemia-induced mastitis in mice. Specifically, succinate increased the production of gut microbiota-extracellular vehicles (mEVs) containing lipopolysaccharides, which can diffuse across the damaged intestinal barrier into the mammary glands. Administration of mEVs promotes mammary inflammation via activation of the TLR4/NF-κB pathway.

CONCLUSIONS

Our findings suggest that succinate promotes mastitis through the proliferation of enteric pathogens and mEVs production, suggesting a potential strategy for mastitis intervention on the basis of intestinal metabolic regulation and pathogen inhibition. The role of mEVs in interspecific communication has also been elucidated.

Adipose tissue-gut microbiome crosstalk in inflammation and thermogenesis

Previously characterized as inert fat depots, adipocytes are now recognized as dynamic mediators of inflammatory tone, metabolic health, and nutrient homeostasis. As endocrine organs, specialized depots of adipose tissue engage in crosstalk between the gut, liver, pancreas, and brain to coordinate appetite, thermogenesis, and ultimately body weight. These functions are tightly linked to the inflammatory status of adipose tissue, which is in turn influenced by the health of the gut microbiome. Here, we review recent findings linking specific gut microbes and their secreted factors, including recently identified elements such as bacterial extracellular vesicles, to the functional status of adipocytes. We conclude that further study may generate novel approaches for treating obesity and metabolic disease.

Microbiota-derived succinic acid mediates attenuating effect of dietary tomato juice supplementation on steatohepatitis through enhancing intestinal barrier

The hepatoprotective potential of tomato juice (TJ) has been reported in chronic liver models, and its potential prebiotic properties may be key to its preventative effects. However, the mechanistic role of the gut microbiota and its derived metabolites in ameliorating nonalcoholic steatohepatitis (NASH) via TJ remains unclear. In this study, we explored how TJ regulates gut microbiota and succinic acid (SA) to restore intestinal barrier function and thus suppress NASH progression. TJ supplementation effectively reduced serum lipid concentrations, alleviated endotoxin levels, and suppressed activation of the endotoxin-TLR4-NF-κB pathway in methionine-choline-deficient (MCD) diet-induced NASH mice. TJ restored the MCD diet-induced gut microbiota dysbiosis, increased the abundance of short-chain fatty acid and SA-producing bacteria (Bifidobacterium, Ileibacterium, Odoribacter, and Parasutterella) and enhanced the expression of intestinal barrier-associated proteins (E-cadherin, Claudin-1, MUC-2, and ZO-1). The hepatoprotective and enteroprotective effects of TJ were abolished in an antibiotic-treated mouse model, underscoring the pivotal role of the gut microbiota in the beneficial effects of TJ on NASH. Fecal metabolomics demonstrated that TJ significantly upregulated the tricarboxylic acid cycle, pyruvate metabolism, and butanoate metabolism pathways, increasing levels of butyric acid (BA) and SA-metabolites associated with reduced hepatic steatosis and intestinal damage. We further found that the physiological concentration of SA, rather than BA, could reduce pro-inflammatory cytokines (TNF-α and IL-6) levels and enhance mucin proteins and tight junction markers in the LPS-induced colon cell line LS174T. This study uncovers new mechanisms by which TJ prevents NASH, highlighting the potential of TJ and SA as effective dietary supplements for patients with chronic liver diseases.

Ageing, proteostasis, and the gut: Insights into neurological health and disease

Recent research has illuminated the profound bidirectional communication between the gastrointestinal tract and the brain, furthering our understanding of neurological ailments facilitating possible therapeutic strategies. Technological advancements in high-throughput sequencing and multi-omics have unveiled significant alterations in gut microbiota and their metabolites in various neurological disorders. This review provides a thorough analysis of the role of microbiome-gut-brain axis in neurodegenerative disease pathology, linking it to reduced age-associated proteostasis. We discuss evidences that substantiate the existence of a gut-brain cross talk ranging from early clinical accounts of James Parkinson to Braak's hypothesis. In addition to understanding of microbes, the review particularly entails specific metabolites which are altered in neurodegenerative diseases. The regulatory effects of microbial metabolites on protein clearance mechanisms, proposing their potential therapeutic implications, are also discussed. By integrating this information, we advocate for a combinatory therapeutic strategy that targets early intervention, aiming to restore proteostasis and ameliorate disease progression. This approach not only provides a new perspective on the pathogenesis of neurodegenerative diseases but also highlights innovative strategies to combat the increasing burden of these age-related disorders.

Multi-omics reveals the effects of dietary supplementation with Bupleuri radix branch powder on gut microbiota and lipid metabolism: insights into gut microbial-muscle interactions

Improving livestock growth and raising the quality of livestock products have attracted much attention owing to the market's growing need for livestock products. Bupleuri Radix branches powder (BR) has a variety of health characteristics, but its effects on ruminant growth and animal product quality are still uncertain. This study explored the effects of BR on growth performance, health status, gut microbiota, and muscle lipid metabolism of Shaanxi fine-wool sheep (SFS), and examined the interaction between gut microbiota and lipid metabolism through correlation analysis. The results indicated that BR can regulate the immune function, intestinal VFAs, and enzyme activity of FSF by improving the gut microbiota, thereby affecting its muscle lipid metabolism. The lipid metabolite TG showed a strong positive correlation with the gut microbes Bacteroides and Fibrobacter, while Phosphatidylethanolamine and Phosphatidyl serine (PE and PS) showed a significant negative correlation with Fibrobacter. The above results indicate that gut microbiota and lipid metabolites interact with each other. BR has the effects of promoting SFS growth, improving body health, and improving meat quality. These findings offer new insights into improve animal growth performance and livestock product quality in modern farming.

IMPORTANCE

Enhancing livestock growth performance and improving meat quality are important guidelines for the development of the current animal husbandry industry; thus, we explored a comprehensive study of Bupleuri Radix (BR) on growth performance, gut microbiology, and muscle lipid metabolism in Shaanxi fine-wool sheep (SFS). Our research has found that BR could improve the growth performance of SFS and meat quality by affecting gut microbes. This study provides new solutions to improve the economic efficiency of animal husbandry.

Stratification of human gut microbiomes by succinotype is associated with inflammatory bowel disease status

BACKGROUND

The human gut microbiome produces and consumes a variety of compounds that interact with the host and impact health. Succinate is of particular interest as it intersects with both host and microbiome metabolism. However, which gut bacteria are most responsible for the consumption of intestinal succinate is poorly understood.

RESULTS

We build upon an enrichment-based whole fecal sample culturing approach and identify two main bacterial taxa that are responsible for succinate consumption in the human intestinal microbiome, Phascolarctobacterium and Dialister. These two taxa have the hallmark of a functional guild and are strongly mutual exclusive across 21,459 fecal samples in 94 cohorts and can thus be used to assign a robust "succinotype" to an individual. We show that they differ with respect to their rate of succinate consumption in vitro and that this is associated with higher concentrations of fecal succinate. Finally, individuals suffering from inflammatory bowel disease (IBD) are more likely to have the Dialister succinotype compared to healthy subjects.

CONCLUSIONS

We identified that only two bacterial genera are the key succinate consumers in human gut microbiome, despite the fact that many more intestinal bacteria encode for the succinate pathway. This highlights the importance of phenotypic assays in functionally profiling intestinal microbiota. A stratification based on "succinotype" is to our knowledge the first function-based classification of human intestinal microbiota. The association of succinotype with IBD thus builds a bridge between microbiome function and IBD pathophysiology related to succinate homeostasis. Video Abstract.

Barley β-glucan consumption improves glucose tolerance by increasing intestinal succinate concentrations

Barley is rich in β-glucan, which can alter gut microbiota and metabolome profiles, potentially affecting host metabolism. However, the microbiota and metabolites increased by barley β-glucan remain unclear. In this study, we focused on the gut-microbiota-derived metabolite succinate and investigated the microbiome and metabolome profiles altered by barley β-glucan intake. C57BL/6 J mice were fed a standard or middle-fat diet containing barley flour rich in β-glucan or barley flour without β-glucan, and their gut microbiota and metabolome profiles were analyzed. The results showed increased Bacteroides, Parasutterella, and succinate due to barley β-glucan intake independent of diet differences. Next, we used mice lacking slc13a2, a gene that is involved in the cellular uptake of succinate. Wild-type mice showed improved glucose tolerance after the intake of barley β-glucan, but this effect was attenuated in the slc13a2-deficient mice. These results suggest that barley β-glucan intake increases succinate and succinate-producing bacteria and affects glucose metabolism.

Organ crosstalk and dysfunction in sepsis

Sepsis is a dysregulated immune response to an infection that leads to organ dysfunction. Sepsis-associated organ dysfunction involves multiple inflammatory mechanisms and complex metabolic reprogramming of cellular function. These mechanisms cooperate through multiple organs and systems according to a complex set of long-distance communications mediated by cellular pathways, solutes, and neurohormonal actions. In sepsis, the concept of organ crosstalk involves the dysregulation of one system, which triggers compensatory mechanisms in other systems that can induce further damage. Despite the abundance of studies published on ​​organ crosstalk in the last decade, there is a need to formulate a more comprehensive framework involving all organs to create a more detailed picture of sepsis. In this paper, we review the literature published on organ crosstalk in the last 10 years and explore how these relationships affect the progression of organ failure in patients with septic shock. We explored these relationships in terms of the heart-kidney-lung, gut-microbiome-liver-brain, and adipose tissue-muscle-bone crosstalk in sepsis patients. A deep connection exists among these organs based on crosstalk. We also review how multiple therapeutic interventions administered in intensive care units, such as mechanical ventilation, antibiotics, anesthesia, nutrition, and proton pump inhibitors, affect these systems and must be carefully considered when managing septic patients. The progression to multiple organ dysfunction syndrome in sepsis patients is still one of the most frequent causes of death in critically ill patients. A better understanding and monitoring of the mechanics of organ crosstalk will enable the anticipation of organ damage and the development of individualized therapeutic strategies.

Strategies for producing probiotic biomass and postbiotics from Akkermansia muciniphila in submerged cultivations incorporating prebiotic sources

This research propounds an innovative technology focused on sustainability to increase the biomass yield of Akkermansia muciniphila, the next-generation probiotic, using prebiotic sources to replace or reduce animal mucin levels. A series of experimental design approaches were developed aiming to optimize the growth of Akkermansiamuciniphila by incorporating extracts of green leafy vegetables and edible mushroom into the cultivation media. Experiments using kale extract (KE), Brassica oleracea L., associated with lyophilized mushroom extract (LME) of Pleurotus ostreatus were the most promising, highlighting the assays with 0.376% KE and 0.423% LME or 1.05% KE and 0.5% LME, in which 3.5 × 1010 CFU (Colony Forming Units) mL- 1 was achieved - higher than in experiments in optimized synthetic media. Such results enhance the potential of using KE and LME not only as mucin substitutes, but also as a source to increase Akkermansia muciniphila biomass yields and release short-chain fatty acids. The work is relevant to the food and pharmaceutical industries in the preparation of the probiotic ingredient.

Lactobacillus Firm-5-derived succinate prevents honeybees from having diabetes-like symptoms

The gut microbiome plays an important role in honeybee hormonal regulation and growth, but the underlying mechanisms are poorly understood. Here, we showed that the depletion of gut bacteria resulted in reduced expression of insulin-like peptide gene (ilp) in the head, accompanied by metabolic syndromes resembling those of Type 1 diabetes in humans: hyperglycemia, impaired lipid storage, and decreased metabolism. These symptoms were alleviated by gut bacterial inoculation. Gut metabolite profiling revealed that succinate, produced by Lactobacillus Firm-5, played deterministic roles in activating ilp gene expression and in regulating metabolism in honeybees. Notably, we demonstrated that succinate modulates host ilp gene expression through stimulating gut gluconeogenesis, a mechanism resembling that of humans. This study presents evidence for the role of gut metabolite in modulating host metabolism and contributes to the understanding of the interactions between gut microbiome and bee hosts.

3-Hydroxypropionate production from myo-inositol by the gut acetogen Blautia schinkii

Species of the genus Blautia are not only abundant in the human gut but also contribute to human well-being. Our study demonstrates that the gut acetogen Blautia schinkii can grow on myo-inositol. We identified the pathway of myo-inositol degradation through a combination of physiological and biochemical studies, genome-wide expression profiling and homology searches. Initially, myo-inositol is oxidized to 2-keto-myo-inositol. This compound is then metabolized by a series of enzymes - a dehydratase, hydrolase, isomerase and kinase - to form 2-deoxy-5-keto-d-gluconic acid 6-phosphate. This intermediate is split by an aldolase into malonate semialdehyde and dihydroxyacetone phosphate, which is an intermediate of the Embden-Meyerhof-Parnas pathway. This pathway leads to the production of pyruvate and, subsequently, acetate. Concurrently, malonate semialdehyde is reduced to 3-hydroxypropionate (3-HP). The genes responsible for myo-inositol degradation are clustered on the genome, except for the gene encoding the aldolase. We identified the putative aldolase Fba_3 and 3-HP dehydrogenase Adh1 encoding genes bioinformatically and verified them biochemically using enzyme assays with heterologously produced and purified protein. The major fermentation end products were 3-HP and acetate, produced in similar amounts. The production of the unusual fermentation end product 3-HP is significant not only for human health but also for the potential bioindustrial production of this highly desired compound.

Gut microbe-derived metabolites and the risk of cardiovascular disease in the METSIM cohort

Background

An association between gut microbes and cardiovascular disease (CVD) has been established, but the underlying mechanisms remain largely unknown.

Methods

We conducted a secondary analysis of the cross-sectional data obtained from the Metabolic Syndrome in Men (METSIM) population-based cohort of 10,194 Finnish men (age = 57.65 ± 7.12 years). We tested the levels of circulating gut microbe-derived metabolites as predictors of CVD, ischemic cerebrovascular accident (CVA), and myocardial infarction (MI). The Kaplan-Meier method was used to estimate the time from the participants' first outpatient clinic visit to the occurrence of adverse outcomes. The associations between metabolite levels and the outcomes were assessed using Cox proportional hazard models.

Results

During a median follow-up period of 200 months, 979 participants experienced CVD, 397 experienced CVA, and 548 experienced MI. After adjusting for traditional risk factors and correcting for multiple comparisons, higher plasma levels of succinate [quartile 4 vs. quartile 1; adjusted hazard ratio, aHR = 1.30, (confidence interval (CI), 1.10-1.53) p = 0.0003, adjusted p = 0.01] were significantly associated with the risk of CVD. High plasma levels of ursodeoxycholic acid (UDCA) (quartile 3 vs. quartile 1); [aHR = 1.68, (CI, 1.26-2.2); p = 0.0003, adj. p = 0.01] were associated with a higher risk of CVA. Furthermore, as a continuous variable, succinate was associated with a 10% decrease in the risk of CVD [aHR = 0.9; (CI, 0.84-0.97); p = 0.008] and a 15% decrease in the risk of MI [aHR = 0.85, (CI, 0.77-0.93); p = 0.0007].

Conclusion

Gut microbe-derived metabolites, succinate, and ursodeoxycholic acid were associated with CVD, MI, and CVA, respectively. Regulating the gut microbes may represent a potential therapeutic target for modulating CVD and CVA.

Intestinal microbiota analysis of different Blastocystis subtypes and Blastocystis-negative individuals in Taiwan

BACKGROUND

Intestinal parasitic infections are the most common infectious diseases among Southeast Asian migrant workers in Taiwan, especially for infections with Blastocystis hominis. However, little is known about the impact of Blastocystis subtypes (STs) on the gut microbiota.

METHODS

We retrospectively evaluated the prevalence of intestinal parasites in a teaching hospital in Northern Taiwan in the period of 2015-2019. Blastocystis-positive stool specimens were collected for ST analysis by polymerase chain reaction in 2020. Intestinal microbiota analyses of different Blastocystis STs and Blastocystis-free individuals were conducted by 16S rRNA sequencing.

RESULTS

A total of 13,859 subjects were analyzed, of which 1802 cases (13%) were diagnosed with intestinal parasitic infections. B. hominis infections were the most prevalent (n = 1546, 85.7%). ST analysis of Blastocystis-positive samples (n = 150) indicated that ST1 was the most common type, followed by ST3, ST4, ST2, ST7, and ST5. Different Blastocystis STs (ST1, ST3, and ST4) were associated with distinct richness and diversity of the microbiota. Taxonomic profiles revealed that Akkermansia muciniphila was significantly enriched for all analyzed Blastocystis STs, whereas Holdemanella biformis was more abundant in the Blastocystis-free group. Additionally, Succinivibrio dextrinosolvens and Coprococcus eutactus were specifically more abundant in ST3 carriers than in non-infected individuals.

CONCLUSION

This study demonstrates that A. muciniphila is positively associated with all Blastocystis STs, while H. biformis was negatively associated with them. Several bacteria were enriched in specific STs, highlighting the need for further microbiota analysis at the ST level to elucidate the pathogenicity of Blastocystis.

Metabolic complexity drives divergence in microbial communities

Microbial communities are shaped by environmental metabolites, but the principles that govern whether different communities will converge or diverge in any given condition remain unknown, posing fundamental questions about the feasibility of microbiome engineering. Here we studied the longitudinal assembly dynamics of a set of natural microbial communities grown in laboratory conditions of increasing metabolic complexity. We found that different microbial communities tend to become similar to each other when grown in metabolically simple conditions, but they diverge in composition as the metabolic complexity of the environment increases, a phenomenon we refer to as the divergence-complexity effect. A comparative analysis of these communities revealed that this divergence is driven by community diversity and by the assortment of specialist taxa capable of degrading complex metabolites. An ecological model of community dynamics indicates that the hierarchical structure of metabolism itself, where complex molecules are enzymatically degraded into progressively simpler ones that then participate in cross-feeding between community members, is necessary and sufficient to recapitulate our experimental observations. In addition to helping understand the role of the environment in community assembly, the divergence-complexity effect can provide insight into which environments support multiple community states, enabling the search for desired ecosystem functions towards microbiome engineering applications.

Type 2 Diabetes Mellitus in Low- and Middle-Income Countries: The Significant Impact of Short-Chain Fatty Acids and Their Quantification

Globally, type 2 diabetes mellitus (T2DM) is a major threat to the public's health, particularly in low- and middle-income countries (LMICs). The production of short-chain fatty acids (SCFAs) by the gut microbiota has been reported to have the potential to reduce the prevalence of T2DM, particularly in LMICs where the disease is becoming more common. Dietary fibers are the primary source of SCFAs; they can be categorized as soluble (such as pectin and inulin) or insoluble (such as resistant starches). Increased consumption of processed carbohydrates, in conjunction with insufficient consumption of dietary fiber, has been identified as a significant risk factor for type 2 diabetes (T2DM). However, there are still controversies over the therapeutic advantages of SCFAs on human glucose homeostasis, due to a lack of studies in this area. Hence, a few questions need to be addressed to gain a better understanding of the beneficial link between SCFAs and glucose metabolism. These include the following: What are the biochemistry and biosynthesis of SCFAs? What role do SCFAs play in the pathology of T2DM? What is the most cost-effective strategy that can be employed by LMICs with limited laboratory resources to enhance their understanding of the beneficial function of SCFAs in patients with T2DM? To address the aforementioned questions, this paper aims to review the existing literature on the protective roles that SCFAs have in patients with T2DM. This paper further discusses possible cost-effective and accurate strategies to quantify SCFAs, which may be recommended for implementation by LMICs as preventive measures to lower the risk of T2DM.

Novel Dairy Fermentates Have Differential Effects on Key Immune Responses Associated with Viral Immunity and Inflammation in Dendritic Cells

Fermented foods and ingredients, including furmenties derived from lactic acid bacteria (LAB) in dairy products, can modulate the immune system. Here, we describe the use of reconstituted skimmed milk powder to generate novel fermentates from Lactobacillus helveticus strains SC232, SC234, SC212, and SC210, and from Lacticaseibacillus casei strains SC209 and SC229, and demonstrate, using in vitro assays, that these fermentates can differentially modulate cytokine secretion via bone-marrow-derived dendritic cells (BMDCs) when activated with either the viral ligand loxoribine or an inflammatory stimulus, lipopolysaccharide. Specifically, we demonstrate that SC232 and SC234 increase cytokines IL-6, TNF-α, IL-12p40, IL-23, IL-27, and IL-10 and decrease IL-1β in primary bone-marrow-derived dendritic cells (BMDCs) stimulated with a viral ligand. In contrast, exposure of these cells to SC212 and SC210 resulted in increased IL-10, IL-1β, IL-23, and decreased IL-12p40 following activation of the cells with the inflammatory stimulus LPS. Interestingly, SC209 and SC229 had little or no effect on cytokine secretion by BMDCs. Overall, our data demonstrate that these novel fermentates have specific effects and can differentially enhance key immune mechanisms that are critical to viral immune responses, or can suppress responses involved in chronic inflammatory conditions, such as ulcerative colitis (UC), and Crohn's disease (CD).

Important roles of Ruminococcaceae in the human intestine for resistant starch utilization

Intricate ecosystem of the human gut microbiome is affected by various environmental factors, genetic makeup of the individual, and diet. Specifically, resistant starch (RS) is indigestible in the small intestine but nourishes the gut microbiota in the colon. Degradation of RS in the gut begins with primary degraders, such as Bifidobacterium adolescentis and Ruminococcus bromii. Recently, new RS degraders, such as Ruminococcoides bili, have been reported. These microorganisms play crucial roles in the transformation of RS into short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate. SCFAs are necessary to maintain optimal intestinal health, regulate inflammation, and protect against various illnesses. This review discusses the effects of RS on gut and highlights its complex interactions with gut flora, especially the Ruminococcaceae family.

Heat stress and feeding effects on the mucosa-associated and digesta microbiome and their relationship to plasma and digesta fluid metabolites in the jejunum of dairy cows

The intestinal microbiota plays a pivotal role in digestive processes and maintains gut health and intestinal homeostasis. These functions may be compromised by increased environmental heat, which in turn reduces feed intake and gut integrity and activates the intestinal immune system. It remains unknown whether high ambient temperatures, which cause heat stress (HS) in dairy cows, disturb the eubiosis of the microbial community, and if so, to which extent the reduction in feed intake and the impairment of circulating and intestinal metabolites account for the alterations of the jejunal microbiota. To address these questions, jejunal digesta, mucosa, and plasma samples were collected from cows exposed to heat stress (HS; 28°C, temperature-humidity index [THI] = 76, n = 10), control conditions (CON; 16°C, THI = 60, n = 10), or pair-fed (PF; 16°C, THI = 60, n = 10) for 7 d. Digesta fluids were examined for pH, acetate, nonesterified fatty acids (NEFA), glucose, and lactate, and plasma samples were analyzed for glucose, lactate, BHB, triglycerides, NEFA, creatinine, and urea. The microbiota of the digesta and mucosa samples were analyzed by 16S rRNA sequencing. The α-diversity was higher in mucosa than digesta but was not affected by high ambient temperatures. However, the mucosa-associated microbiota appeared more responsive to ambient heat than the digesta microbiome. The adaptive responses under HS conditions comprised an increased mucosal abundance of Bifidobacteriaceae, Succinivibrionaceae UCG-001, Clostridia and Lactobacillus. In the digesta, HS has exerted effects on microbial abundance of Colidextribacter, and Lachnospiraceae UCG-008. Several correlations between plasma or intestinal metabolites and microbiota were elucidated, including Methanobacteriaceae correlating positively with plasma BHB and digesta glucose concentrations. Moreover, the reduction in feed intake during HS had non-negligible effects on microbial diversity and the abundance of certain taxa, underpinning the importance of nutrient supply on maintaining intestinal homeostasis.

Microbiota based personalized nutrition improves hyperglycaemia and hypertension parameters and reduces inflammation: a prospective, open label, controlled, randomized, comparative, proof of concept study

Background

Recent studies suggest that gut microbiota composition, abundance and diversity can influence many chronic diseases such as type 2 diabetes. Modulating gut microbiota through targeted nutrition can provide beneficial effects leading to the concept of personalized nutrition for health improvement. In this prospective clinical trial, we evaluated the impact of a microbiome-based targeted personalized diet on hyperglycaemic and hyperlipidaemic individuals. Specifically, BugSpeaks®-a microbiome profile test that profiles microbiota using next generation sequencing and provides personalized nutritional recommendation based on the individual microbiota profile was evaluated.

Methods

A total of 30 participants with type 2 diabetes and hyperlipidaemia were recruited for this study. The microbiome profile of the 15 participants (test arm) was evaluated using whole genome shotgun metagenomics and personalized nutritional recommendations based on their microbiota profile were provided. The remaining 15 participants (control arm) were provided with diabetic nutritional guidance for 3 months. Clinical and anthropometric parameters such as HbA1c, systolic/diastolic pressure, c-reactive protein levels and microbiota composition were measured and compared during the study.

Results

The test arm (microbiome-based nutrition) showed a statistically significant decrease in HbA1c level from 8.30 (95% confidence interval (CI), [7.74-8.85]) to 6.67 (95% CI [6.2-7.05]), p < 0.001 after 90 days. The test arm also showed a 5% decline in the systolic pressure whereas the control arm showed a 7% increase. Incidentally, a sub-cohort of the test arm of patients with >130 mm Hg systolic pressure showed a statistically significant decrease of systolic pressure by 14%. Interestingly, CRP level was also found to drop by 19.5%. Alpha diversity measures showed a significant increase in Shannon diversity measure (p < 0.05), after the microbiome-based personalized dietary intervention. The intervention led to a minimum two-fold (Log2 fold change increase in species like Phascolarctobacterium succinatutens, Bifidobacterium angulatum, and Levilactobacillus brevis which might have a beneficial role in the current context and a similar decrease in species like Alistipes finegoldii, and Sutterella faecalis which have been earlier shown to have some negative effects in the host. Overall, the study indicated a net positive impact of the microbiota based personalized dietary regime on the gut microbiome and correlated clinical parameters.

Lactobacillus-derived protoporphyrin IX and SCFAs regulate the fiber size via glucose metabolism in the skeletal muscle of chickens

The gut microbiota contributes to skeletal muscle energy metabolism and is an indirect factor affecting meat quality. However, the role of specific gut microbes in energy metabolism and fiber size of skeletal muscle in chickens remains largely unknown. In this study, we first performed cecal microbiota transplantation from Chinese indigenous Jingyuan chickens (JY) to Arbor Acres chickens (AA), to determine the effects of microbiota on skeletal muscle fiber and energy metabolism. Then, we used metagenomics, gas chromatography, and metabolomics analysis to identify functional microbes. Finally, we validated the role of these functional microbes in regulating the fiber size via glucose metabolism in the skeletal muscle of chickens through feeding experiments. The results showed that the skeletal muscle characteristics of AA after microbiota transplantation tended to be consistent with that of JY, as the fiber diameter was significantly increased, and glucose metabolism level was significantly enhanced in the pectoralis muscle. L. plantarum, L. ingluviei, L. salivarius, and their mixture could increase the production of the microbial metabolites protoporphyrin IX and short-chain fatty acids, therefore increasing the expression levels of genes related to the oxidative fiber type (MyHC SM and MyHC FRM), mitochondrial function (Tfam and CoxVa), and glucose metabolism (PFK, PK, PDH, IDH, and SDH), thereby increasing the fiber diameter and density. These three Lactobacillus species could be promising probiotics to improve the meat quality of chicken.IMPORTANCEThis study revealed that the L. plantarum, L. ingluviei, and L. salivarius could enhance the production of protoporphyrin IX and short-chain fatty acids in the cecum of chickens, improving glucose metabolism, and finally cause the increase in fiber diameter and density of skeletal muscle. These three microbes could be potential probiotic candidates to regulate glucose metabolism in skeletal muscle to improve the meat quality of chicken in broiler production.

Cellular succinate metabolism and signaling in inflammation: implications for therapeutic intervention

Succinate, traditionally viewed as a mere intermediate of the tricarboxylic acid (TCA) cycle, has emerged as a critical mediator in inflammation. Disruptions within the TCA cycle lead to an accumulation of succinate in the mitochondrial matrix. This excess succinate subsequently diffuses into the cytosol and is released into the extracellular space. Elevated cytosolic succinate levels stabilize hypoxia-inducible factor-1α by inhibiting prolyl hydroxylases, which enhances inflammatory responses. Notably, succinate also acts extracellularly as a signaling molecule by engaging succinate receptor 1 on immune cells, thus modulating their pro-inflammatory or anti-inflammatory activities. Alterations in succinate levels have been associated with various inflammatory disorders, including rheumatoid arthritis, inflammatory bowel disease, obesity, and atherosclerosis. These associations are primarily due to exaggerated immune cell responses. Given its central role in inflammation, targeting succinate pathways offers promising therapeutic avenues for these diseases. This paper provides an extensive review of succinate's involvement in inflammatory processes and highlights potential targets for future research and therapeutic possibilities development.

Human microbiota from drug-naive patients with obsessive-compulsive disorder drives behavioral symptoms and neuroinflammation via succinic acid in mice

Emerging evidence suggests that the gut microbiota is closely related to psychiatric disorders. However, little is known about the role of the gut microbiota in the development of obsessive-compulsive disorder (OCD). Here, to investigate the contribution of gut microbiota to the pathogenesis of OCD, we transplanted fecal microbiota from first-episode, drug-naive OCD patients or demographically matched healthy individuals into antibiotic-treated specific pathogen-free (SPF) mice and showed that colonization with OCD microbiota is sufficient to induce core behavioral deficits, including abnormal anxiety-like and compulsive-like behaviors. The fecal microbiota was analyzed using 16 S rRNA full-length sequencing, and the results demonstrated a clear separation of the fecal microbiota of mice colonized with OCD and control microbiota. Notably, microbiota from OCD-colonized mice resulted in injured neuronal morphology and function in the mPFC, with inflammation in the mPFC and colon. Unbiased metabolomic analyses of the serum and mPFC region revealed the accumulation of succinic acid (SA) in OCD-colonized mice. SA impeded neuronal activity and induced an inflammatory response in both the colon and mPFC, impacting intestinal permeability and brain function, which act as vital signal mediators in gut microbiota-brain-immune crosstalk. Manipulations of dimethyl malonate (DM) have been reported to exert neuroprotective effects by suppressing the oxidation of accumulated succinic acid, attenuating the downstream inflammatory response and neuronal damage, and can help to partly improve abnormal behavior and reduce neuroinflammation and intestinal inflammation in OCD-colonized mice. We propose that the gut microbiota likely regulates brain function and behaviors in mice via succinic acid signaling, which contributes to the pathophysiology of OCD through gut-brain crosstalk and may provide new insights into the treatment of this disorder.

Pulmonary succinate receptor 1 elevation in high-fat diet mice exacerbates lipopolysaccharides-induced acute lung injury via sensing succinate

BACKGROUND

Individuals with obesity have higher level of circulating succinate, which acts as a signaling factor that initiates inflammation. It is obscure whether succinate and succinate receptor 1 (SUCNR1) are involved in the process of obesity aggravating acute lung injury (ALI).

METHODS

The lung tissue and blood samples from patients with obesity who underwent lung wedgectomy or segmental resection were collected. Six-week-old male C57BL/6J mice were fed a high-fat diet for 12 weeks to induce obesity and lipopolysaccharides (LPS) were injected intratracheally (100 μg, 1 mg/ml) for 24 h to establish an ALI model. The pulmonary SUCNR1 expression and succinate level were measured. Exogenous succinate was supplemented to assess whether succinate exacerbated the LPS-induced lung injury. We next examined the cellular localization of pulmonary SUCNR1. Furthermore, the role of the succinate-SUCNR1 pathway in LPS-induced inflammatory responses in MH-s macrophages and obese mice was investigated.

RESULT

The pulmonary SUCNR1 expression and serum succinate level were significantly increased in patients with obesity and in HFD mice. Exogenous succinate supplementation significantly increased the severity of ALI and inflammatory response. SUCNR1 was mainly expressed on lung macrophages. In LPS-stimulated MH-s cells, knockdown of SUCNR1 expression significantly inhibited pro-inflammatory cytokines' expression, the increase of hypoxia-inducible factor-1α (HIF-1α) expression, inhibitory κB-α (IκB-α) phosphorylation, p65 phosphorylation and p65 translocation to nucleus. In obese mice, SUCNR1 inhibition significantly alleviated LPS-induced lung injury and decreased the HIF-1α expression and IκB-α phosphorylation.

CONCLUSION

The high expression of pulmonary SUCNR1 and serum succinate accumulation at least partly participate in the process of obesity aggravating LPS-induced lung injury.