The Role of Diet Related Short-Chain Fatty Acids in Colorectal Cancer Metabolism and Survival: Prevention and Therapeutic Implications

Differential effects of pectin-based dietary fibre type and gut microbiota composition on in vitro fermentation outcomes

Interactions between human gut microbiota and dietary fibres (DF) are influenced by the complexity and diversity of both individual microbiota and sources of DF. Based on 480 in vitro fermentations, a full factorial experiment was performed with six faecal inocula representing two enterotypes and three DF sources with nanometer, micrometer, and millimeter length-scales (apple pectin, apple cell walls and apple particles) at two concentrations. Increasing DF size reduced substrate disappearance and fermentation rates but not biomass growth. Concentrated DF enhanced butyrate production and lactate cross-feeding. Enterotype differentiated final microbial compositions but not biomass or fermentation metabolite profiles. Individual donor microbiota differences did not influence DF type or concentration effects but were manifested in the promotion of different functional microbes within each population with the capacity to degrade the DF substrates. Overall, consistent effects (independent of donor microbiota variation) of DF type and concentration on kinetics of substrate degradation, microbial biomass production, gas kinetics and metabolite profiles were found, which can form the basis for informed design of DF for desired rates/sites and consequences of gut fermentation. These results add further evidence to the concept that, despite variations between individuals, the human gut microbiota represents a community with conserved emergent properties.

Post-diagnosis dietary factors, supplement use and colorectal cancer prognosis: A Global Cancer Update Programme (CUP Global) systematic literature review and meta-analysis

The role of diet in colorectal cancer prognosis is not well understood and specific lifestyle recommendations are lacking. We searched for randomised controlled trials (RCTs) and longitudinal observational studies on post-diagnosis dietary factors, supplement use and colorectal cancer survival outcomes in PubMed and Embase from inception until 28th February 2022. Random-effects dose-response meta-analyses were conducted when at least three studies had sufficient information. The evidence was interpreted and graded by the CUP Global independent Expert Committee on Cancer Survivorship and Expert Panel. Five RCTs and 35 observational studies were included (30,242 cases, over 8700 all-cause and 2100 colorectal cancer deaths, 3700 progression, recurrence, or disease-free events). Meta-analyses, including 3-10 observational studies each, were conducted for: whole grains, nuts/peanuts, red and processed meat, dairy products, sugary drinks, artificially sweetened beverages, coffee, alcohol, dietary glycaemic load/index, insulin load/index, marine omega-3 polyunsaturated fatty acids, supplemental calcium, circulating 25-hydroxyvitamin D (25[OH]D) and all-cause mortality; for alcohol, supplemental calcium, circulating 25(OH)D and colorectal cancer-specific mortality; and for circulating 25(OH)D and recurrence/disease-free survival. The overall evidence was graded as 'limited'. The inverse associations between healthy dietary and/or lifestyle patterns (including diets that comprised plant-based foods), whole grains, total, caffeinated, or decaffeinated coffee and all-cause mortality and the positive associations between unhealthy dietary patterns, sugary drinks and all-cause mortality provided 'limited-suggestive' evidence. All other exposure-outcome associations provided 'limited-no conclusion' evidence. Additional, well-conducted cohort studies and carefully designed RCTs are needed to develop specific lifestyle recommendations for colorectal cancer survivors.

An optimal combination of four active components in Huangqin decoction for the synergistic sensitization of irinotecan against colorectal cancer

BACKGROUND

Irinotecan (CPT-11) is a first-line treatment for advanced colorectal cancer (CRC). Four components (baicalin, baicalein, wogonin, and glycyrrhizic acid) derived from Huangqin Decoction (HQD) have been proven to enhance the anticancer activity of CPT-11 in our previous study.

OBJECTIVE

This study aimed to determine the optimal combination of the four components for sensitizing CPT-11 as well as to explore the underlying mechanism.

METHODS

The orthogonal design method was applied to obtain candidate combinations (Cmb1-9) of the four components. The influence of different combinations on the anticancer effect of CPT-11 was first evaluated in vitro by cell viability, wound healing ability, cloning formation, apoptosis, and cell cycle arrest. Then, a CRC xenograft mice model was constructed to evaluate the anticancer effect of the optimal combination in vivo. Potential mechanisms of the optimal combination exerting a sensitization effect combined with CPT-11 against CRC were analyzed by targeted metabolomics.

RESULTS

In vitro experiments determined that Cmb8 comprised of baicalin, baicalein, wogonin, and glycyrrhizic acid at the concentrations of 17 μM, 47 μM, 46.5 μM and 9.8 μM respectively was the most effective combination. Importantly, the cell viability assay showed that Cmb8 exhibited synergistic anticancer activity in combination with CPT-11. In in vivo experiments, this combination (15 mg/kg of baicalin, 24 mg/kg of baicalein, 24 mg/kg of wogonin, and 15 mg/kg of glycyrrhizic acid) also showed a synergistic anticancer effect. Meanwhile, inflammatory factors and pathological examination of the colon showed that Cmb8 could alleviate the gastrointestinal damage induced by CPT-11. Metabolic profiling of the tumors suggested that the synergistic anticancer effect of Cmb8 might be related to the regulation of fatty acid metabolism.

CONCLUSION

The optimal combination of four components derived from HQD for the synergistic sensitization of CPT-11 against CRC was identified.

Enhancing insights into diseases through horizontal gene transfer event detection from gut microbiome

Horizontal gene transfer (HGT) phenomena pervade the gut microbiome and significantly impact human health. Yet, no current method can accurately identify complete HGT events, including the transferred sequence and the associated deletion and insertion breakpoints from shotgun metagenomic data. Here, we develop LocalHGT, which facilitates the reliable and swift detection of complete HGT events from shotgun metagenomic data, delivering an accuracy of 99.4%-verified by Nanopore data-across 200 gut microbiome samples, and achieving an average F1 score of 0.99 on 100 simulated data. LocalHGT enables a systematic characterization of HGT events within the human gut microbiome across 2098 samples, revealing that multiple recipient genome sites can become targets of a transferred sequence, microhomology is enriched in HGT breakpoint junctions (P-value = 3.3e-58), and HGTs can function as host-specific fingerprints indicated by the significantly higher HGT similarity of intra-personal temporal samples than inter-personal samples (P-value = 4.3e-303). Crucially, HGTs showed potential contributions to colorectal cancer (CRC) and acute diarrhoea, as evidenced by the enrichment of the butyrate metabolism pathway (P-value = 3.8e-17) and the shigellosis pathway (P-value = 5.9e-13) in the respective associated HGTs. Furthermore, differential HGTs demonstrated promise as biomarkers for predicting various diseases. Integrating HGTs into a CRC prediction model achieved an AUC of 0.87.

Ganoderma lucidum Polysaccharide Supplementation Significantly Activates T-Cell-Mediated Antitumor Immunity and Enhances Anti-PD-1 Immunotherapy Efficacy in Colorectal Cancer

Ganoderma lucidum polysaccharide (GLP) is a prebiotic with immunomodulatory effects. However, the therapeutic potential of GLP in tumor immunotherapy has not been fully explored, especially in T cell-mediated antitumor immunity. In this study, we found that GLP significantly inhibited tumor growth and activated antitumor immunity in colorectal cancer (CRC). In the spleens and tumor tissues, the proportion of cytotoxic CD8+T cells and Th1 helper cells increased, while immunosuppressive Tregs decreased. Additionally, microbiota dysbiosis was alleviated by GLP, and short-chain fatty acid production was increased. Meanwhile, GLP decreased the ratio of kynurenine and tryptophan (Kyn/Trp) in the serum, which contributed to antitumor immunity of T cells. More importantly, the combination of GLP and the immune checkpoint inhibitor anti-PD-1 monoclonal antibody further enhanced the efficacy of anti-PD-1 immunotherapy. Thus, GLP as a prebiotic has the potential to be used in tumor immunotherapy.

Gut microbiome-metabolites axis: A friend or foe to colorectal cancer progression

An expanding corpus of research robustly substantiates the complex interrelation between gut microbiota and the onset, progression, and metastasis of colorectal cancer. Investigations in both animal models and human subjects have consistently underscored the role of gut bacteria in a variety of metabolic activities, driven by dietary intake. These activities include amino acid metabolism, carbohydrate fermentation, and the generation and regulation of bile acids. These metabolic derivatives, in turn, have been identified as significant contributors to the progression of colorectal cancer. This thorough review meticulously explores the dynamic interaction between gut bacteria and metabolites derived from the breakdown of amino acids, fatty acid metabolism, and bile acid synthesis. Notably, bile acids have been recognized for their potential carcinogenic properties, which may expedite tumor development. Extensive research has revealed a reciprocal influence of gut microbiota on the intricate spectrum of colorectal cancer pathologies. Furthermore, strategies to modulate gut microbiota, such as dietary modifications or probiotic supplementation, may offer promising avenues for both the prevention and adjunctive treatment of colorectal cancer. Nevertheless, additional research is imperative to corroborate these findings and enhance our comprehension of the underlying mechanisms in colorectal cancer development.

Mechanism of Iron Ion Homeostasis in Intestinal Immunity and Gut Microbiota Remodeling

Iron is a vital trace element that plays an important role in humans and other organisms. It plays an active role in the growth, development, and reproduction of bacteria, such as Bifidobacteria. Iron deficiency or excess can negatively affect bacterial hosts. Studies have reported a major role of iron in the human intestine, which is necessary for maintaining body homeostasis and intestinal barrier function. Organisms can maintain their normal activities and regulate some cancer cells in the body by regulating iron excretion and iron-dependent ferroptosis. In addition, iron can modify the interaction between hosts and microorganisms by altering their growth and virulence or by affecting the immune system of the host. Lactic acid bacteria such as Lactobacillus acidophilus (L. acidophilus), Lactobacillus rhamnosus (L. rhamnosus), and Lactobacillus casei (L. casei) were reported to increase trace elements, protect the host intestinal barrier, mitigate intestinal inflammation, and regulate immune function. This review article focuses on the two aspects of the iron and gut and generally summarizes the mechanistic role of iron ions in intestinal immunity and the remodeling of gut microbiota.

Dietary medium-chain fatty acids and risk of incident colorectal cancer in a predominantly low-income population: a report from the Southern Community Cohort Study

BACKGROUND

No prospective observational study has specifically examined the associations between dietary intakes of medium-chain fatty acids and risk of colorectal cancer.

OBJECTIVES

This study examined the association between dietary intakes of medium-chain fatty acids and colorectal cancer risk overall and by racial subgroups in a predominantly low-income United States population.

METHODS

This prospective study included 71,599 eligible participants aged 40 to 79 who were enrolled in the Southern Community Cohort Study between 2002 and 2009 in 12 southeastern United States states. Incident colorectal cancer cases were ascertained via linkage to state cancer registries, which was completed through 31 December, 2016. The dietary intakes of medium-chain fatty acids were assessed using a validated 89-item food frequency questionnaire. Multivariable Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between intakes of medium-chain fatty acids and risk for incident colorectal cancer.

RESULTS

Among 71,599 participants, 48,008 (67.3%) were Black individuals and 42,260 (59.0%) were female. A total of 868 incident colorectal cancer cases occurred during a median follow-up of 13.7 y. Comparing the highest to the lowest quartile, high intake of dodecanoic acid/lauric acid (C12:0) was associated with reduced risk of colorectal cancer among White participants (HR: 0.52; 95% CI: 0.30, 0.91; P-trend = 0.05), but not in Black individuals (HR: 0.92; 95% CI, 0.68, 1.24; P-trend = 0.80) in multivariable-adjusted models. No associations were found between intakes of hexanoic acid/caproic acid (C6:0), octanoic acid/caprylic acid (C8:0), or decanoic acid/capric acid (C10:0) and risk of incident colorectal cancer overall or within racial subgroups.

CONCLUSIONS

In a predominantly low-income United States population, an increased dietary C12:0 intake was associated with a substantially reduced risk of colorectal cancer only among White individuals, but not in Black individuals.

Tracing the evolving dynamics and research hotspots of microbiota and immune microenvironment from the past to the new era

Gut microbiota can regulate many physiological processes within gastrointestinal tract and other distal sites. Dysbiosis may not only influence chronic diseases like the inflammatory bowel disease (IBD), metabolic disease, tumor and its therapeutic efficacy, but also deteriorate acute injuries. This article aims to review the documents in this field and summarize the research hotspots as well as developing processes. Gut microbiota and immune microenvironment-related documents from 1976 to 2022 were obtained from the Web of Science Core Collection database. Bibliometrics was used to assess the core authors and journals, most contributive countries and affiliations together with hotspots in this field and keyword co-occurrence analysis. Data were visualized to help comprehension. Nine hundred and twelve documents about gut microbiota and immune microenvironment were retrieved, and the annual publications increased gradually. The most productive author, country, and affiliation were "Zitvogel L," USA and "UNIV TEXAS MD ANDERSON CANC CTR," respectively. FRONTIERS IN IMMUNOLOGY, CANCERS, and INTERNATIONAL JOURNAL OF MOLECULAR SCIENCE were the periodicals with most publications. Keyword co-occurrence analysis identified three clusters, including gut microbiota, inflammation, and IBD. Combined with the visualized analysis of documents and keyword co-occurrence as well as literature reading, we recognized three key topics of gut microbiota: cancer and therapy; immunity, inflammation and IBD; acute injuries and metabolic diseases. This article revealed researches on gut microbiota and immune microenvironment were growing. More attention should be given to the latest hotspots like gut microbiota, inflammation, IBD, cancer and immunotherapy, acute traumas, and metabolic diseases.IMPORTANCEGut microbiota can regulate many physiological processes within gastrointestinal tract and other distal sites. Dysbiosis may not only influence chronic diseases like inflammatory bowel disease (IBD), metabolic disease, tumor and its therapeutic efficacy, but also deteriorate acute injuries. While the application of bibliometrics in the field of gut microbiota and immune microenvironment still remains blank, which focused more on the regulation of the gut microbiota on the immune microenvironment of different kinds of diseases. Here, we intended to review and summarize the presented documents in gut microbiota and immune microenvironment field by bibliometrics. And we revealed researches on gut microbiota and immune microenvironment were growing. More attention should be given to the latest hotspots like gut microbiota, inflammation, IBD, cancer and immunotherapy, acute traumas, and metabolic diseases.

A Multi-Omics and Human Biomonitoring Approach to Assessing the Effectiveness of Fortified Balanced Energy-Protein Supplementation on Maternal and Newborn Health in Burkina Faso: A Study Protocol

Fortified balanced energy-protein (BEP) supplementation is a promising intervention for improving maternal health, birth outcomes and infant growth in low- and middle-income countries. This nested biospecimen sub-study aimed to evaluate the physiological effect of multi-micronutrient-fortified BEP supplementation on pregnant and lactating women and their infants. Pregnant women (15-40 years) received either fortified BEP and iron-folic acid (IFA) (intervention) or IFA only (control) throughout pregnancy. The same women were concurrently randomized to receive either a fortified BEP supplement during the first 6 months postpartum in combination with IFA for the first 6 weeks (i.e., intervention) or the postnatal standard of care, which comprised IFA alone for 6 weeks postpartum (i.e., control). Biological specimens were collected at different timepoints. Multi-omics profiles will be characterized to assess the mediating effect of BEP supplementation on the different trial arms and its effect on maternal health, as well as birth and infant growth outcomes. The mediating effect of the exposome in the relationship between BEP supplementation and maternal health, birth outcomes and infant growth were characterized via biomonitoring markers of air pollution, mycotoxins and environmental contaminants. The results will provide holistic insight into the granular physiological effects of prenatal and postnatal BEP supplementation.

Diet as a modifiable factor in tumorigenesis: Focus on microbiome-derived bile acid metabolites and short-chain fatty acids

Several lines of evidences have implicated the resident microbiome as a key factor in the modulation of host physiology and pathophysiology; including the resistance to cancers. Gut microbiome heavily influences host lipid homeostasis by their modulatory effects on the metabolism of bile acids (BAs). Microbiota-derived BA metabolites such as deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) are implicated in the pathogeneses of various cancer types. The pathogenic mechanisms are multimodal in nature, with widespread influences on the host immunes system, cell survival and growth signalling and DNA damage. On the other hand, short-chain fatty acids (SCFAs) produced by the resident microbial activity on indigestible dietary fibres as well as during intermittent fasting regimens (such as the Ramazan fasting) elicit upregulation of the beneficial anti-inflammatory and anticancer pathways in the host. The present review first provides a brief overview of the molecular mechanisms of microbiota-derived lipid metabolites in promotion of tumour development. The authors then discuss the potential of diet as a therapeutic route for beneficial alteration of microbiota and the consequent changes in the production of SCFAs, particularly butyrate, in relation to the cancer prevention and treatment.

Molecular Mechanisms of Obesity-Induced Development of Insulin Resistance and Promotion of Amyloid-β Accumulation: Dietary Therapy Using Weak Organic Acids via Improvement of Lowered Interstitial Fluid pH

Insulin resistance is one of the etiologies of type 2 diabetes mellitus (T2DM) and has been suggested to contribute to the development of Alzheimer's disease by promoting amyloid-β accumulation. Various causes of insulin resistance have been suggested; however, mechanisms of insulin resistance development remain to be elucidated in many respects. Elucidating the mechanisms underlying the development of insulin resistance is one of the key factors in developing methods to prevent the onset of T2DM and Alzheimer's disease. It has been suggested that the body pH environment plays an important role in the control of cellular functions by regulating the action of hormones including insulin and the activity of enzymes and neurons, thereby maintaining homeostatic conditions of the body. This review introduces: (1) Mitochondrial dysfunction through oxidative stress caused by obesity-induced inflammation. (2) Decreased pH of interstitial fluid due to mitochondrial dysfunction. (3) Development of insulin resistance due to diminution of insulin affinity to its receptor caused by the lowered interstitial fluid pH. (4) Accelerated accumulation of amyloid-β due to elevated activities of β- and γ-secretases caused by the lowered interstitial fluid pH. (5) Diet therapies for improving insulin resistance with weak organic acids that act as bases in the body to raise the pH of lowered interstitial fluid and food factors that promote absorption of weak organic acids in the gut.

Modulation of the Tumor Microenvironment by Microbiota-Derived Short-Chain Fatty Acids: Impact in Colorectal Cancer Therapy

Finding new therapeutic approaches towards colorectal cancer (CRC) is of increased relevance, as CRC is one of the most common cancers worldwide. CRC standard therapy includes surgery, chemotherapy, and radiotherapy, which may be used alone or in combination. The reported side effects and acquired resistance associated with these strategies lead to an increasing need to search for new therapies with better efficacy and less toxicity. Several studies have demonstrated the antitumorigenic properties of microbiota-derived short-chain fatty acids (SCFAs). The tumor microenvironment is composed by non-cellular components, microbiota, and a great diversity of cells, such as immune cells. The influence of SCFAs on the different constituents of the tumor microenvironment is an important issue that should be taken into consideration, and to the best of our knowledge there is a lack of reviews on this subject. The tumor microenvironment is not only closely related to the growth and development of CRC but also affects the treatment and prognosis of the patients. Immunotherapy has emerged as a new hope, but, in CRC, it was found that only a small percentage of patients benefit from this treatment being closely dependent on the genetic background of the tumors. The aim of this review was to perform an up-to-date critical literature review on current knowledge regarding the effects of microbiota-derived SCFAs in the tumor microenvironment, particularly in the context of CRC and its impact in CRC therapeutic strategies. SCFAs, namely acetate, butyrate, and propionate, have the ability to modulate the tumor microenvironment in distinct ways. SCFAs promote immune cell differentiation, downregulate the expression of pro-inflammatory mediators, and restrict the tumor-induced angiogenesis. SCFAs also sustain the integrity of basement membranes and modulate the intestinal pH. CRC patients have lower concentrations of SCFAs than healthy individuals. Increasing the production of SCFAs through the manipulation of the gut microbiota could constitute an important therapeutic strategy towards CRC due to their antitumorigenic effect and ability of modulating tumor microenvironment.

The Gut Microbiome and Ferroptosis in MAFLD

Metabolic-associated fatty liver disease (MAFLD) is a new disease definition, and is proposed to replace the previous name, nonalcoholic fatty liver disease (NAFLD). Globally, MAFLD/NAFLD is the most common liver disease, with an incidence rate ranging from 6% to 35% in adult populations. The pathogenesis of MAFLD/NAFLD is closely related to insulin resistance (IR), and the genetic susceptibility to acquired metabolic stress-associated liver injury. Similarly, the gut microbiota in MAFLD/NAFLD is being revaluated by scientists, as the gut and liver influence each other via the gut-liver axis. Ferroptosis is a novel form of programmed cell death caused by iron-dependent lipid peroxidation. Emerging evidence suggests that ferroptosis has a key role in the pathological progression of MAFLD/NAFLD, and inhibition of ferroptosis may become a novel therapeutic strategy for the treatment of NAFLD. This review focuses on the main mechanisms behind the promotion of MAFLD/NAFLD occurrence and development by the intestinal microbiota and ferroptosis. It outlines new strategies to target the intestinal microbiota and ferroptosis to facilitate future MAFLD/NAFLD therapies.

Quantification of short-chain fatty acids in human stool samples by LC-MS/MS following derivatization with aniline analogues

The gut microbiome produces a range of short chain fatty acids (SCFA) crucially linked with diet and nutrition, metabolism, gastrointestinal health and homeostasis. SCFA are primarily measured using gas or liquid chromatography-mass spectrometry (LC/MS) after undergoing chemical derivatization. Here we assess the merits of a derivatization protocol using aniline and two aniline analogues (3-phenoxyaniline and 4-(benzyloxy)aniline) for the targeted LC-MS/MS quantification of nine SCFA (acetic, propionic, butyric, valeric, caproic acid, isobutyric, isovaleric, 2-methylbutyric, and 2-ethylbutyric acid). Evaluation of product ion spectra and optimization of MS detection conditions, provided superior detection sensitivity for 3-phenoxyaniline and 4-(benzyloxy)aniline compared to aniline. We developed a facile SCFA derivatization method using 3-phenoxyaniline under mild reaction conditions which allows for the simultaneous quantification of these SCFA in human stool samples in under eleven minutes using multiple reaction monitoring LC-MS/MS. The method was successfully validated and demonstrates intra- and inter-day accuracy (88.5-103% and 86.0-109%) and precision (CV of 0.55-7.00% and 0.33-9.55%) with recoveries (80.1-87.2% for LLOQ, 88.5-93.0% for ULOQ) and carry-over of (2.68-17.9%). Selectivity, stability and matrix effects were also assessed and satisfied validation criteria. Method applicability was demonstrated by analysing SCFA profiles in DNA-stabilized human stool samples from newly diagnosed colorectal cancer patients prior to surgery. The development of this improved method and its compatibility to measure SCFAs from DNA-stabilized stool will facilitate studies investigating the gut microbiome in health and disease.

Host Microbiomes Influence the Effects of Diet on Inflammation and Cancer

Cancer is the second leading cause of death globally, and there is a growing appreciation for the complex involvement of diet, microbiomes, and inflammatory processes culminating in tumorigenesis. Although research has significantly improved our understanding of the various factors involved in different cancers, the underlying mechanisms through which these factors influence tumor cells and their microenvironment remain to be completely understood. In particular, interactions between the different microbiomes, specific dietary factors, and host cells mediate both local and systemic immune responses, thereby influencing inflammation and tumorigenesis. Developing an improved understanding of how different microbiomes, beyond just the colonic microbiome, can interact with dietary factors to influence inflammatory processes and tumorigenesis will support our ability to better understand the potential for microbe-altering and dietary interventions for these patients in future.

Metabolites as extracellular vesicle cargo in health, cancer, pleural effusion, and cardiovascular diseases: An emerging field of study to diagnostic and therapeutic purposes

Extracellular vesicles (EVs) are highly diverse nanoscale membrane-bound structures released from different cell types into the extracellular environment. They play essential functions in cell signaling by transporting their cargo, such as proteins, RNA, DNA, lipids, metabolites, and small molecules, to recipient cells. It has recently been shown that EVs might modulate carcinogenesis by delivering cargo to recipient cells. Furthermore, recent discoveries revealed that changes in plasma-derived EV levels and cargo in subjects with metabolic diseases were documented by many researchers, suggesting that EVs might be a promising source of disease biomarkers. One of the cargos of EVs that has recently attracted the most attention is metabolites. The metabolome of these vesicles introduces a plethora of disease indicators; hence, examining the metabolomics of EVs detected in human biofluids would be an effective approach. On the other hand, metabolites have various roles in biological systems, including the production of energies, synthesizing macromolecules, and serving as signaling molecules and hormones. Metabolome rewiring in cancer and stromal cells is a characteristic of malignancy, but the current understanding of how this affects the metabolite composition and activity of tumor-derived EVs remains in its infancy. Since new findings and studies in the field of exosome biology and metabolism are constantly being published, it is likely that diagnostic and treatment techniques, including the use of exosome metabolites, will be launched in the coming years. Recent years have seen increased interest in the EV metabolome as a possible source for biomarker development. However, our understanding of the role of these molecules in health and disease is still immature. In this work, we have provided the latest findings regarding the role of metabolites as EV cargoes in the pathophysiology of diseases, including cancer, pleural effusion (PE), and cardiovascular disease (CVD). We also discussed the significance of metabolites as EV cargoes of microbiota and their role in host-microbe interaction. In addition, the latest findings on metabolites in the form of EV cargoes as biomarkers for disease diagnosis and treatment are presented in this study.

Gut microbiota-derived short-chain fatty acids regulate gastrointestinal tumor immunity: a novel therapeutic strategy?

Tumor immune microenvironment (TIME), a tumor-derived immune component, is proven to be closely related to the development, metastasis, and recurrence of tumors. Gut microbiota and its fermented-metabolites short-chain fatty acids (SCFAs) play a critical role in maintaining the immune homeostasis of gastrointestinal tumors. Consisting mainly of acetate, propionate, and butyrate, SCFAs can interact with G protein-coupled receptors 43 of T helper 1 cell or restrain histone deacetylases (HDACs) of cytotoxic T lymphocytes to exert immunotherapy effects. Studies have shed light on SCFAs can mediate the differentiation and function of regulatory T cells, as well as cytokine production in TIME. Additionally, SCFAs can alter epigenetic modification of CD8⁺ T cells by inhibiting HDACs to participate in the immune response process. In gastrointestinal tumors, the abundance of SCFAs and their producing bacteria is significantly reduced. Direct supplementation of dietary fiber and probiotics, or fecal microbiota transplantation to change the structure of gut microbiota can both increase the level of SCFAs and inhibit tumor development. The mechanism by which SCFAs modulate the progression of gastrointestinal tumors has been elucidated in this review, aiming to provide prospects for the development of novel immunotherapeutic strategies.

Fecal Luminal Factors from Patients with Gastrointestinal Diseases Alter Gene Expression Profiles in Caco-2 Cells and Colonoids

Previous in vitro studies have shown that the intestinal luminal content, including metabolites, possibly regulates epithelial layer responses to harmful stimuli and promotes disease. Therefore, we aimed to test the hypothesis that fecal supernatants from patients with colon cancer (CC), ulcerative colitis (UC) and irritable bowel syndrome (IBS) contain distinct metabolite profiles and establish their effects on Caco-2 cells and human-derived colon organoids (colonoids). The metabolite profiles of fecal supernatants were analyzed by liquid chromatography-mass spectrometry and distinguished patients with CC (n = 6), UC (n = 6), IBS (n = 6) and healthy subjects (n = 6). Caco-2 monolayers and human apical-out colonoids underwent stimulation with fecal supernatants from different patient groups and healthy subjects. Their addition did not impair monolayer integrity, as measured by transepithelial electrical resistance; however, fecal supernatants from different patient groups and healthy subjects altered the gene expression of Caco-2 monolayers, as well as colonoid cultures. In conclusion, the stimulation of Caco-2 cells and colonoids with fecal supernatants derived from CC, UC and IBS patients altered gene expression profiles, potentially reflecting the luminal microenvironment of the fecal sample donor. This experimental approach allows for investigating the crosstalk at the gut barrier and the effects of the gut microenvironment in the pathogenesis of intestinal diseases.

Microbiota-Derived Short-Chain Fatty Acids: New Road in Colorectal Cancer Therapy

The colon microbiota is an important player in colorectal cancer (CRC) development, which is responsible for most of the cancer-related deaths worldwide. During carcinogenesis, the colon microbiota composition changes from a normobiosis profile to dysbiosis, interfering with the production of short-chain fatty acids (SCFAs). Each SCFA is known to play a role in several biological processes but, despite their reported individual effects, colon cells are exposed to these compounds simultaneously and the combined effect of SCFAs in colon cells is still unknown. Our aim was to explore the effects of SCFAs, alone or in combination, unveiling their biological impact on CRC cell phenotypes. We used a mathematical model for the prediction of the expected SCFA mixture effects and found that, when in mixture, SCFAs exhibit a concentration addition behavior. All SCFAs, alone or combined at the physiological proportions founded in the human colon, revealed to have a selective and anticancer effect by inhibiting colony formation and cell proliferation, increasing apoptosis, disturbing the energetic metabolism, inducing lysosomal membrane permeabilization, and decreasing cytosolic pH. We showed for the first time that SCFAs are specific towards colon cancer cells, showing promising therapeutic effects. These findings open a new road for the development of alternatives for CRC therapy based on the increase in SCFA levels through the modulation of the colon microbiota composition.

Alterations in Fecal Short-Chain Fatty Acids after Bariatric Surgery: Relationship with Dietary Intake and Weight Loss

Bariatric surgery is associated with weight loss attributed to reduced caloric intake, mechanical changes, and alterations in gut hormones. However, some studies have suggested a heightened incidence of colorectal cancer (CRC) has been associated with bariatric surgery, emphasizing the importance of identifying mechanisms of risk. The objective of this study was to determine if bariatric surgery is associated with decreases in fecal short-chain fatty acids (SCFA), a group of bacterial metabolites of fiber. Fecal samples (n = 22) were collected pre- (~6 weeks) and post-bariatric surgery (~4 months) in patients undergoing Roux-en-Y gastric bypass and sleeve gastrectomy. SCFA levels were quantified using liquid chromatography/mass spectrometry. Dietary intake was quantified using 24-h dietary recalls. Using an aggregate variable, straight SCFAs significantly decreased by 27% from pre- to post-surgery, specifically acetate, propionate, butyrate, and valerate. Pre-surgery weight was inversely associated with butyrate, with no association remaining post-surgery. Multiple food groups were positively (sugars, milk, and red and orange vegetables) and inversely (animal protein) associated with SCFA levels. Our results suggest a potential mechanism linking dietary intake and SCFA levels with CRC risk post-bariatric surgery with implications for interventions to increase SCFA levels.

Role of brain-gut-muscle axis in human health and energy homeostasis

The interrelationship between brain, gut and skeletal muscle plays a key role in energy homeostasis of the body, and is becoming a hot topic of research. Intestinal microbial metabolites, such as short-chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites, communicate with the central nervous system (CNS) by binding to their receptors. In fact, there is a cross-talk between the CNS and the gut. The CNS, under the stimulation of pressure, will also affect the stability of the intestinal system, including the local intestinal transport, secretion and permeability of the intestinal system. After the gastrointestinal tract collects information about food absorption, it sends signals to the central system through vagus nerve and other channels to stimulate the secretion of brain-gut peptide and produce feeding behavior, which is also an important part of maintaining energy homeostasis. Skeletal muscle has receptors for SCFAs and BAs. Therefore, intestinal microbiota can participate in skeletal muscle energy metabolism and muscle fiber conversion through their metabolites. Skeletal muscles can also communicate with the gut system during exercise. Under the stimulation of exercise, myokines secreted by skeletal muscle causes the secretion of intestinal hormones, and these hormones can act on the central system and affect food intake. The idea of the brain-gut-muscle axis is gradually being confirmed, and at present it is important for regulating energy homeostasis, which also seems to be relevant to human health. This article focuses on the interaction of intestinal microbiota, central nervous, skeletal muscle energy metabolism, and feeding behavior regulation, which will provide new insight into the diagnostic and treatment strategies for obesity, diabetes, and other metabolic diseases.

Colon microbiota modulation by dairy-derived diet: new strategy for prevention and treatment of colorectal cancer

An unbalanced diet is one of the well-known risk factors for the development of colorectal cancer (CRC). This type of cancer is currently the main cause of cancer-related deaths worldwide, urging the need for new and more effective preventive and therapeutic approaches. It is already known that CRC patients have alterations in the microbial community and metabolism. In this regard, a concept that has been recently attracting the attention of the scientific community is the development of functional food or nutraceuticals, as a new and more effective strategy to overcome CRC patient-associated dysbiosis. Particularly, dairy product enriched diets are the major dairy source of dietary calcium, vitamin D and folate intake, which are well-known to have a protective effect against CRC development. In addition, these products are rich in both pre- and probiotics, constituting a double strategy to modulate both the intestinal microbiota composition and the production of microbial metabolites. Short-chain fatty acids (SCFA), namely, acetate, butyrate, and propionate, are major contributors to colonic homeostasis since they regulate several biological and metabolic processes. In this review, we performed a state of art study concerning the use of dietary patterns, specifically the dairy-derived diet, in the modulation of the human microbiota and their potential use as pre-, pro- or synbiotics for the development of new preventive and therapeutic strategies for CRC.

Gut Microbiome in Colorectal Cancer: Clinical Diagnosis and Treatment

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers and the leading cause of cancer-associated deaths. Epidemiological studies have shown that both genetic and environmental risk factors contribute to the development of CRC. Several metagenomic studies of CRC have identified gut dysbiosis as a fundamental risk factor in the evolution of colorectal malignancy. Although enormous efforts and substantial progresses have been made in understanding the relationship between the human gut microbiome and CRC, the precise mechanisms involved remain elusive. Recent data have shown a direct causative role of the gut microbiome in DNA damage, inflammation, and drug resistance in CRC, suggesting that modulation of the gut microbiome can act as a powerful tool in CRC prevention and therapy. Here, we provide an overview of the relationship between the gut microbiome and CRC, and explore relevant mechanisms of colorectal tumorigenesis. We next highlight the potential of bacterial species as clinical biomarkers, as well as their roles in therapeutic response. Factors limiting the clinical translation of the gut microbiome and strategies for resolving the current challenges are further discussed.

Exploring Gut Microenvironment in Colorectal Patient with Dual-Omics Platform: A Comparison with Adenomatous Polyp or Occult Blood

The gut mucosa is actively absorptive and functions as the physical barrier to separate the gut ecosystem from host. Gut microbiota-utilized or food-derived metabolites are closely relevant to the homeostasis of the gut epithelial cells. Recent studies widely suggested the carcinogenic impact of gut dysbiosis or altered metabolites on the development of colorectal cancer (CRC). In this study, liquid chromatography coupled-mass spectrometry and long-read sequencing was applied to identify gut metabolites and microbiomes with statistically discriminative abundance in CRC patients (n = 20) as compared to those of a healthy group (n = 60) ofenrolled participants diagnosed with adenomatous polyp (n = 67) or occult blood (n = 40). In total, alteration in the relative abundance of 90 operational taxonomic units (OTUs) and 45 metabolites were identified between recruited CRC patients and healthy participants. Among the candidates, the gradual increases in nine OTUs or eight metabolites were identified in healthy participants, patients diagnosed with occult blood and adenomatous polyp, and CRC patients. The random forest regression model constructed with five OTUs or four metabolites achieved a distinct classification potential to differentially discriminate the presence of CRC (area under the ROC curve (AUC) = 0.998 or 0.975) from the diagnosis of adenomatous polyp (AUC = 0.831 or 0.777), respectively. These results provide the validity of CRC-associated markers, including microbial communities and metabolomic profiles across healthy and related populations toward the early screening or diagnosis of CRC.

Lacticaseibacillus rhamnosus LS8 Ameliorates Azoxymethane/Dextran Sulfate Sodium-Induced Colitis-Associated Tumorigenesis in Mice via Regulating Gut Microbiota and Inhibiting Inflammation

Gut microbiota dysbiosis may promote the process of colorectal cancer (CRC). Lacticaseibacillus rhamnosus LS8 (LRL) is a potential gut microbiota regulating strain because it can produce a novel antimicrobial substance (like cycloalanopine). In addition, this probiotic had an inflammation-ameliorating effect on the dextran sulfate sodium (DSS)-induced colitis mice. However, it is not known whether treatment with this probiotic could ameliorate colitis-associated CRC via regulating gut microbiota. In this study, a CRC mouse model was induced by a single intraperitoneal injection of azoxymethane (AOM, 10 mg/kg) and followed by three 7-day cycles of 2% DSS administration. Results showed that LRL could inhibit tumor formation. Moreover, LRL enhanced the gut barrier by preventing goblet cell loss and promoting the expression of ZO-1, occludin, and claudin-1. Furthermore, LRL ameliorated gut microbiota dysbiosis, which was conducive to the growth of beneficial bacteria (e.g., Faecalibaculum and Akkermansia), and further led to an increase in SCFAs and a decrease in LPS. In addition, LRL alleviated colonic inflammation by inhibiting the overexpression of TLR4/NF-κB, pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-γ, and IL-17a), and chemokines (Cxcl1, Cxcl2, Cxcl3, Cxcl5, and Cxcl7). In conclusion, LRL could alleviate CRC by regulating gut microbiota and preventing gut barrier damage and inflammation.

Regulatory role of short-chain fatty acids in inflammatory bowel disease

Inflammatory bowel disease (IBD) comprises a group of chronic inflammatory disorders of the gastrointestinal tract. Accumulating evidence shows that the development of IBD is always accompanied by the dysbiosis of the gut microbiota (GM), causing a decrease in prebiotic levels and an increase in harmful metabolite levels. This leads to persistent immune response and inflammation in the intestine, greatly impairing the physiological function of the gastrointestinal tract. Short-chain fatty acids (SCFAs) are produced by probiotic gut bacteria from a fiber-rich diet that cannot be digested directly. SCFAs with significant anti-inflammatory functions regulate immune function and prevent an excessive immune response, thereby delaying the clinical progression of IBD. In this review, we summarize the generation of SCFAs and their potential therapeutic effects on IBD. Furthermore, we suggest that SCFAs may modulate innate immune recognition and cytokine production to intervene in the progression of IBD. Additional randomized controlled trials and prospective cohort studies should also investigate the clinical impact of SCFA. Video Abstract.

Dietary α-Linolenic Acid-Rich Flaxseed Oil Ameliorates High-Fat Diet-Induced Atherosclerosis via Gut Microbiota-Inflammation-Artery Axis in ApoE−/− Mice

Atherosclerosis (AS) is closely associated with abnormally chronic low-grade inflammation and gut dysbiosis. Flaxseed oil (FO) rich in omega-3 polyunsaturated fatty acids (PUFAs), which are mainly composed of alpha-linolenic acid (ALA, 18:3 omega-3), has been demonstrated to exhibit pleiotropic benefits in chronic metabolic diseases. However, the impact of dietary ALA-rich FO on AS and its associated underlying mechanisms remain poorly understood. Thus, the present study was designed as two phases to investigate the effects in atherosclerotic Apolipoprotein E (ApoE)^−/− mice. In the initial portion, the ApoE^−/− mice were randomly allocated to three groups: control group (CON), model group (MOD), and FO-fed model group (MOD/FO) and were treated for 12 weeks. The second phase used antibiotic (AB)-treated ApoE^−/− mice were divided into two groups: AB-treated model group (AB/MOD) and FO-fed AB-treated model group (AB/FO). In the results, the dietary ALA-rich FO administration ameliorated atherosclerotic lesion, as well as the parameters of AS (body weights (BWs) and the total bile acids (TBA). Chronic systemic/vascular inflammatory cytokines and in situ macrophages (Mψs) were reduced with FO intervention. In addition, the FO improved the gut integrity and permeability by decreasing the plasma lipopolysaccharide (LPS). Moreover, gut dysbiosis and metabolites [short-chain fatty acids (SCFAs) and bile acids (BAs)] in AS were modulated after FO treatment. Intriguingly, during an AB-treated condition, a significantly weakened amelioration of FO-treated on AS proposed that the intestinal microbiota contributed to the FO effects. A correlation analysis showed close relationships among gut bacteria, metabolites, and inflammation. Collectively, these results suggested that the dietary ALA-rich FO ameliorated the AS in ApoE^−/− mice via the gut microbiota-inflammation-artery axis.

Alterations in the Gut Microbiota and Their Metabolites in Colorectal Cancer: Recent Progress and Future Prospects

Colorectal cancer (CRC) is a leading cause of cancer morbidity and mortality worldwide. The etiology and pathogenesis of CRC remain unclear. A growing body of evidence suggests dysbiosis of gut bacteria can contribute to the occurrence and development of CRC by generating harmful metabolites and changing host physiological processes. Metabolomics, a systems biology method, will systematically study the changes in metabolites in the physiological processes of the body, eventually playing a significant role in the detection of metabolic biomarkers and improving disease diagnosis and treatment. Metabolomics, in particular, has been highly beneficial in tracking microbially derived metabolites, which has substantially advanced our comprehension of host-microbiota metabolic interactions in CRC. This paper has briefly compiled recent research progress of the alterations of intestinal flora and its metabolites associated with CRC and the application of association analysis of metabolomics and gut microbiome in the diagnosis, prevention, and treatment of CRC; furthermore, we discuss the prospects for the problems and development direction of this association analysis in the study of CRC. Gut microbiota and their metabolites influence the progression and causation of CRC, and the association analysis of metabolomics and gut microbiome will provide novel strategies for the prevention, diagnosis, and therapy of CRC.

Lactulose Modulates the Structure of Gut Microbiota and Alleviates Colitis-Associated Tumorigenesis

Lactulose, a galactose-fructose disaccharide, is made from the milk sugar lactose by heating or isomerization processes. Lactulose is proposed to modulate gut microbiota and thus expected to be beneficial in treating inflammatory bowel disease. In the present study, we investigated the therapeutic effect of lactulose on gastrointestinal inflammation and inflammation-related tumorigenesis in a mouse model of colorectal cancer as well as its effect on gut microbiota composition. Azoxymethane (AOM)/dextran sulfate sodium (DSS) model was used in this study. Lactulose treatment was performed by feeding 2% lactulose for 14 weeks. Stool samples collected at 4 time points were used for metagenomic analysis of the microbiota. Pathological analysis was performed 21 weeks after AOM injection. AOM/DSS increased the macrophage counts, inflammatory cytokine expression, colorectal tumorigenesis, and imbalance in gut microbiota composition, as evidenced by increased pathogen abundance (e.g., Escherichia and Clostridium). Lactulose significantly inhibited the inflammatory events, and ameliorated inflammation and tumorigenesis. The composition of the intestinal microbiota was also restored upon lactulose treatment, and lactulose reduced pathogen abundance and increased the abundance of Muribaculum and Lachnospiraceae. Meanwhile, the pathways related to Crohn’s disease were downregulated after lactulose treatment. Our findings suggest that lactulose restores the structure and composition of the intestinal microbiota, mitigates inflammation, and suppresses inflammatory tumorigenesis.

Short-Chain Fatty Acid Butyrate Induces Cilia Formation and Potentiates the Effects of HDAC6 Inhibitors in Cholangiocarcinoma Cells

Cholangiocarcinoma (CCA) is a deadly form of liver cancer with limited therapeutic approaches. The pathogenesis of CCA involves the loss of primary cilia in cholangiocytes, an important organelle that regulates several key cellular functions including the regulation of cell polarity, growth, and differentiation, by a mechanism involving increased expression of deacetylases like HDAC6 and SIRT1. Therefore, cilia restoration may represent an alternative and novel therapeutic approach against CCA. Butyrate is produced by bacterial fermentation of fibers in the intestine and has been shown to inhibit SIRT1, showing antitumor effects on various cancers. Herein, we investigated the role of butyrate on CCA cell proliferation, migration, and EMT and evaluated the synergistic effects with specific HDAC6 inhibition. When CCA cells, including HuCCT1 and KMCH, were treated with butyrate, the cilia formation and acetylated-tubulin levels were increased, while no significant effects were observed in normal human cholangiocytes. Butyrate treatment also depicted reduced cell proliferation in HuCCT1 and KMCH cells, but on the other hand, it affected cell growth of the normal cholangiocytes only at high concentrations. In HuCCT1 cells, spheroid formation and cell migration were also halted by butyrate treatment. Furthermore, we found that butyrate augmented the previously described effects of HDAC6 inhibitors on CCA cell proliferation and migration by reducing the expression of CD44, cyclin D1, PCNA, Zeb1, and Vimentin. In summary, butyrate targets cancer cell growth and migration and enhances the anti-cancer effects of HDAC6 inhibitors in CCA cells, suggesting that butyrate may have therapeutic effects in CCA and other ciliopathies.

Lactate-related metabolic reprogramming and immune regulation in colorectal cancer

Changes in cellular metabolism involving fuel sources are well-known mechanisms of cancer cell differentiation in the context of carcinogenesis. Metabolic reprogramming is regulated by oncogenic signaling and transcriptional networks and has been identified as an essential component of malignant transformation. Hypoxic and acidified tumor microenvironment contributes mainly to the production of glycolytic products known as lactate. Mounting evidence suggests that lactate in the tumor microenvironment of colorectal cancer(CRC) contributes to cancer therapeutic resistance and metastasis. The contents related to the regulatory effects of lactate on metabolism, immune response, and intercellular communication in the tumor microenvironment of CRC are also constantly updated. Here we summarize the latest studies about the pleiotropic effects of lactate in CRC and the clinical value of targeting lactate metabolism as treatment. Different effects of lactate on various immune cell types, microenvironment characteristics, and pathophysiological processes have also emerged. Potential specific therapeutic targeting of CRC lactate metabolism is also discussed. With increased knowledge, effective druggable targets might be identified, with the aim of improving treatment outcomes by reducing chemoresistance.

Microenvironmental Factors Modulating Tumor Lipid Metabolism: Paving the Way to Better Antitumoral Therapy

Metabolic reprogramming is one of the emerging hallmarks of cancer and is driven by both the oncogenic mutations and challenging microenvironment. To satisfy the demands of energy and biomass for rapid proliferation, the metabolism of various nutrients in tumor cells undergoes important changes, among which the aberrant lipid metabolism has gained increasing attention in facilitating tumor development and metastasis in the past few years. Obstacles emerged in the aspect of application of targeting lipid metabolism for tumor therapy, due to lacking of comprehensive understanding on its regulating mechanism. Tumor cells closely interact with stromal niche, which highly contributes to metabolic rewiring of critical nutrients in cancer cells. This fact makes the impact of microenvironment on tumor lipid metabolism a topic of renewed interest. Abundant evidence has shown that many factors existing in the tumor microenvironment can rewire multiple signaling pathways and proteins involved in lipid metabolic pathways of cancer cells. Hence in this review, we summarized the recent progress on the understanding of microenvironmental factors regulating tumor lipid metabolism, and discuss the potential of modulating lipid metabolism as an anticancer approach.

Association of circulating short chain fatty acid levels with colorectal adenomas and colorectal cancer

BACKGROUND & AIMS

Short chain fatty acid (SCFAs) are bacterially derived metabolites suggested to have protective roles against colorectal cancer (CRC) development. However, there is sparse evidence from epidemiological studies in this context. Here, we assessed whether circulating SCFA concentrations varied in patients with colorectal adenomas (CRA) and CRC.

METHODS

Levels of seven SCFAs were extracted from plasma samples and determined by gas chromatography for 213 individuals from Ireland and the Czech Republic (CRC, n = 84; CRA, n = 66; controls, n = 63).

RESULTS

In the Irish CRA/CRC cohort, only levels of 2-MethylButyric acid were significantly higher in cancers compared to the adenoma and control groups (p-values = 0.016 and 0.043). Using regression analysis, we observed that levels of Acetic and Propionic acid were associated with an increased CRC risk in the Czech cohort (Odd Ratio (OR): 1.02; 95% Confidence interval (CI): 1.00-1.03; OR: 1.29; 95% CI: 1.05-1.59, respectively), while i-Valeric and Valeric acid levels were associated with a decreased cancer risk (OR: 0.92; 95% CI: 0.86-0.99; OR: 0.67; 95% CI: 0.44-1.00). In the Irish cohort, levels of SCFAs were not associated with CRC risk.

CONCLUSIONS

The association with colorectal neoplasia varied between the studied SCFAs. Future studies need to confirm these findings and address the mechanism of how these acids may promote or prevent colorectal carcinogenesis.

Effects of valerate on intestinal barrier function in cultured Caco-2 epithelial cell monolayers

BACKGROUND

Short-chain fatty acids (SCFAs) are a group of microbial metabolites of undigested dietary fiber, protein and unabsorbed amino acids in the colon, well-known for their gut health promoting benefits. A relatively high intestinal level of valerate was found in the healthy human subjects. However, the intestinal protection effects and the underlying mechanism of valerate are waiting to be verified and elucidated.

METHODS AND RESULTS

In the present study, valerate, a SCFAs mainly converted from proteins or amino acids, was demonstrated to promote intestinal barrier function at its physiological concentrations of 0-4 mM in the Caco-2 cell monolayer model of intestinal barrier using transepithelial electrical resistance (TEER) assay and paracellular permeability assay. Valerate achieved the maximum increase in the TEER at 2 mM and reduced the paracellular permeability. Its intestinal barrier function promoting activity is similar to that of butyrate, with a broader range of effective concentrations than the later. Through western blot analysis, this activity is linked to the valerate-induced AMPK activation and tight junctions (TJs) assembly, but not to the reinforced expression of TJs related proteins.

CONCLUSIONS

It provides direct experimental evidence supporting valerate's function in intestinal health, implying the once under-valued function of valerate and its amino acid precursors. The valerate's role in regulating intestine homeostasis and its possible synergetic effects with other SCFAs warranted to be further investigated.

The probiotic Companilactobacillus crustorum MN047 alleviates colitis-associated tumorigenesis via modulating the intestinal microenvironment

Supplementation of probiotics is a promising method to alleviate colorectal cancer (CRC) via modulating the intestinal microenvironment. This study aimed to assess the potential anti-CRC effect of Companilactobacillus crustorum MN047 on an azoxymethane and dextran sulfate sodium-induced colitis-associated (CA)-CRC mouse model. Mice were gavaged with C. crustorum MN047 once daily (∼1 × 10⁹ CFU per mouse). The CA-CRC ameliorating effect of this strain was investigated based on the gut microbiota, inflammation and intestinal barrier integrity. Results showed that C. crustorum MN047 could significantly attenuate tumorigenesis and inflammation via suppressing the TLR4/NF-κB pathway. Moreover, this probiotic could improve the intestinal barrier integrity by increasing the mRNA level of some tight junction-related proteins and reducing goblet cell loss. In addition, C. crustorum MN047 administration led to an increase in beneficial bacteria and a decrease in harmful bacteria, thereby increasing SCFAs and reducing LPS levels. These results suggested that C. crustorum MN047 could partially ameliorate the formation of CA-CRC by modulating the gut microbiota, attenuating inflammation and enhancing the intestinal barrier integrity. Therefore, C. crustorum MN047 was a promising probiotic supplement for attenuating CA-CRC.

Natural Products Induce Lysosomal Membrane Permeabilization as an Anticancer Strategy

Cancer is a global health and economic issue. The majority of anticancer therapies become ineffective due to frequent genomic turnover and chemoresistance. Furthermore, chemotherapy and radiation are non-specific, killing all rapidly dividing cells including healthy cells. In this review, we examine the ability of some natural products to induce lysosomal-mediated cell death in neoplastic cells as a way to kill them more specifically than conventional therapies. This list is by no means exhaustive. We postulate mechanisms to explain lysosomal membrane permeabilization and its role in triggering cell death in cancer cells.

Lactobacillus plantarum TWK10 Attenuates Aging-Associated Muscle Weakness, Bone Loss, and Cognitive Impairment by Modulating the Gut Microbiome in Mice

In humans, aging is characterized by the progressive decline in biological, physiological, and psychological functions, and is a major risk factor in the development of chronic diseases. Therefore, the development of strategies aimed at attenuating aging-related disorders and promoting healthy aging is critical. In a previous study, we have demonstrated that Lactobacillus plantarum TWK10 (TWK10), a probiotic strain isolated from Taiwanese pickled cabbage, improved muscle strength, exercise endurance, and overall body composition in healthy humans. In this study, the effect of TWK10 on the progression of age-related impairments was investigated in mice. We found that TWK10 not only enhanced muscle strength in young mice, but also prevented the aging-related loss of muscle strength in aged mice, which was accompanied by elevated muscle glycogen levels. Furthermore, TWK10 attenuated the aging-associated decline in learning and memory abilities, as well as bone mass. Further analyses of gut microbiota using next-generation sequencing (NGS) of the 16S rRNA gene showed that the pattern of gut microbial composition was clearly altered following 8 weeks of TWK10 administration. TWK10-treated mice also experienced an increase in short-chain fatty acid (SCFA)-producing bacteria and higher overall levels of gut SCFA. Furthermore, TWK10 administration to some extent reversed the aging-associated accumulation of pathogenic bacterial taxa. In conclusion, TWK10 could be viewed as a potential therapeutic agent that attenuates aging-related disorders and provides health benefits by modulating the imbalance of gut microbiota.

Transorgan short-chain fatty acid fluxes in the fasted and postprandial state in the pig

The short-chain fatty acids (SCFAs) acetate, propionate, butyrate, isovalerate, and valerate are end products of intestinal bacterial fermentation and important mediators in the interplay between the intestine and peripheral organs. To unravel the transorgan fluxes and mass balance comparisons of SCFAs, we measured their net fluxes across several organs in a translational pig model. In multicatheterized conscious pigs [n = 12, 25.6 (95% CI [24.2, 26.9]) kg, 8-12 wk old], SCFA fluxes across portal-drained viscera (PDV), liver, kidneys, and hindquarter (muscle compartment) were measured after an overnight fast and in the postprandial state, 4 h after administration of a fiber-free, mixed meal. PDV was the main releasing compartment of acetate, propionate, butyrate, isovalerate, and valerate during fasting and in the postprandial state (all P = 0.001). Splanchnic acetate release was high due to the absence of hepatic clearance. All other SCFAs were extensively taken up by the liver (all P < 0.05). Even though only 7% [4, 10] (propionate), 42% [23, 60] (butyrate), 26% [12, 39] (isovalerate), and 3% [0.4, 5] (valerate) of PDV release were excreted from the splanchnic area in the fasted state, splanchnic release of all SCFAs was significant (all P values ≤0.01). Splanchnic propionate, butyrate, isovalerate, and valerate release remained low but significant in the postprandial state (all P values <0.01). We identified muscle and kidneys as main peripheral SCFA metabolizing organs, taking up the majority of all splanchnically released SCFAs in the fasted state and in the postprandial state. We conclude that the PDV is the main SCFA releasing and the liver the main SCFA metabolizing organ. Splanchnically released SCFAs appear to be important energy substrates to peripheral organs not only in the fasted but also in the postprandial state.NEW & NOTEWORTHY Using a multicatheterized pig model, we identified the portal-drained viscera as the main releasing compartment of the short-chain fatty acids acetate, propionate, butyrate, isovalerate, and valerate in the fasted and postprandial states. Low hepatic acetate metabolism resulted in a high splanchnic release, whereas all other SCFAs were extensively cleared resulting in low but significant splanchnic releases. Muscle and kidneys are the main peripheral SCFA metabolizing organs during fasting and in the postprandial state.

Obesity and inflammation: colorectal cancer engines

The prevalence of obesity continues to increase to the extent that it became a worldwide pandemic. An accumulating body of evidence has associated obesity with the development of different types of cancer, including colorectal cancer, which is a notorious disease with a high mortality rate. At the molecular level, colorectal cancer is a heterogenous disease characterized by a myriad of genetic and epigenetic alterations associated with various forms of genomic instability (detailed in Supplementary Materials). Recently, the microenvironment has emerged as a major factor in carcinogenesis. Our aim is to define the different molecular alterations leading to the development of colorectal cancer in obese patients with a focus on the role of the microenvironment in carcinogenesis. We also highlight all existent molecules in clinical trials that target the activated pathways in obesity-associated colorectal cancer, whether used as single treatments or in combination. Obesity predisposes to colorectal cancer via creating a state of chronic inflammation with dysregulated adipokines, inflammatory mediators, and other factors such as immune cell infiltration. A unifying theme in obesity-mediated colorectal cancer is the activation of the PI3K/AKT, mTOR/MAPK, and STAT3 signaling pathways. Different inhibitory molecules towards these pathways exist, increasing the therapeutic choice of obesity-associated colon cancer. However, obese patients are more likely to suffer from chemotherapy overdosing. Preventing obesity through maintaining a healthy and active lifestyle remains to be the best remedy.

Functional lower airways genomic profiling of the microbiome to capture active microbial metabolism

BACKGROUND

Microbiome studies of the lower airways based on bacterial 16S rRNA gene sequencing assess microbial community structure but can only infer functional characteristics. Microbial products, such as short-chain fatty acids (SCFAs), in the lower airways have significant impact on the host's immune tone. Thus, functional approaches to the analyses of the microbiome are necessary.

METHODS

Here we used upper and lower airway samples from a research bronchoscopy smoker cohort. In addition, we validated our results in an experimental mouse model. We extended our microbiota characterisation beyond 16S rRNA gene sequencing with the use of whole-genome shotgun (WGS) and RNA metatranscriptome sequencing. SCFAs were also measured in lower airway samples and correlated with each of the sequencing datasets. In the mouse model, 16S rRNA gene and RNA metatranscriptome sequencing were performed.

RESULTS

Functional evaluations of the lower airway microbiota using inferred metagenome, WGS and metatranscriptome data were dissimilar. Comparison with measured levels of SCFAs shows that the inferred metagenome from the 16S rRNA gene sequencing data was poorly correlated, while better correlations were noted when SCFA levels were compared with WGS and metatranscriptome data. Modelling lower airway aspiration with oral commensals in a mouse model showed that the metatranscriptome most efficiently captures transient active microbial metabolism, which was overestimated by 16S rRNA gene sequencing.

CONCLUSIONS

Functional characterisation of the lower airway microbiota through metatranscriptome data identifies metabolically active organisms capable of producing metabolites with immunomodulatory capacity, such as SCFAs.

Microbiota Signals during the Neonatal Period Forge Life-Long Immune Responses

The microbiota regulates immunological development during early human life, with long-term effects on health and disease. Microbial products include short-chain fatty acids (SCFAs), formyl peptides (FPs), polysaccharide A (PSA), polyamines (PAs), sphingolipids (SLPs) and aryl hydrocarbon receptor (AhR) ligands. Anti-inflammatory SCFAs are produced by Actinobacteria, Bacteroidetes, Firmicutes, Spirochaetes and Verrucomicrobia by undigested-carbohydrate fermentation. Thus, fiber amount and type determine their occurrence. FPs bind receptors from the pattern recognition family, those from commensal bacteria induce a different response than those from pathogens. PSA is a capsular polysaccharide from B. fragilis stimulating immunoregulatory protein expression, promoting IL-2, STAT1 and STAT4 gene expression, affecting cytokine production and response modulation. PAs interact with neonatal immunity, contribute to gut maturation, modulate the gut–brain axis and regulate host immunity. SLPs are composed of a sphingoid attached to a fatty acid. Prokaryotic SLPs are mostly found in anaerobes. SLPs are involved in proliferation, apoptosis and immune regulation as signaling molecules. The AhR is a transcription factor regulating development, reproduction and metabolism. AhR binds many ligands due to its promiscuous binding site. It participates in immune tolerance, involving lymphocytes and antigen-presenting cells during early development in exposed humans.

The gut microbiome: what the oncologist ought to know

The gut microbiome (GM) has been implicated in a vast number of human pathologies and has become a focus of oncology research over the past 5 years. The normal gut microbiota imparts specific function in host nutrient metabolism, xenobiotic and drug metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation and protection against pathogens. Strong evidence is emerging to support the effects of the GM on the development of some malignancies but also on responses to cancer therapies, most notably, immune checkpoint inhibition. Tools for manipulating the GM including dietary modification, probiotics and faecal microbiota transfer (FMT) are in development. Current understandings of the many complex interrelationships between the GM, cancer, the immune system, nutrition and medication are ultimately based on a combination of short‐term clinical trials and observational studies, paired with an ever-evolving understanding of cancer biology. The next generation of personalised cancer therapies focusses on molecular and phenotypic heterogeneity, tumour evolution and immune status; it is distinctly possible that the GM will become an increasingly central focus amongst them. The aim of this review is to provide clinicians with an overview of microbiome science and our current understanding of the role the GM plays in cancer.

Resectable Colorectal Cancer: Current Perceptions on the Correlation of Recurrence Risk, Microbiota and Detection of Genetic Mutations in Liquid Biopsies

Metastatic colorectal cancer (mCRC) remains a highly lethal malignancy, although considerable progress has resulted from molecular alterations in guiding optimal use of available treatments. CRC recurrence remains a great barrier in the disease management. Hence, the spotlight turns to newly mapped fields concerning recurrence risk factors in patients with resectable CRC with a focus on genetic mutations, microbiota remodeling and liquid biopsies. There is an urgent need for novel biomarkers to address disease recurrence since specific genetic signatures can identify a higher or lower recurrence risk (RR) and, thus, be used both as biomarkers and treatment targets. To a large extent, CRC is mediated by the immune and inflammatory interplay of microbiota, through intestinal dysbiosis. Clarification of these mechanisms will yield new opportunities, leading not only to the appropriate stratification policies, but also to more precise, personalized monitoring and treatment navigation. Under this perspective, early detection of post-operative CRC recurrence is of utmost importance. Ongoing trials, focusing on circulating tumor cells (CTCs) and, even more, circulating tumor DNA (ctDNA), seem to pave the way to a promising, minimally invasive but accurate and life-saving monitoring, not only supporting personalized treatment but favoring patients' quality of life, as well.

Lactobacillus coryniformis MXJ32 administration ameliorates azoxymethane/dextran sulfate sodium-induced colitis-associated colorectal cancer via reshaping intestinal microenvironment and alleviating inflammatory response

PURPOSE

Gut microbiota has been reported to contribute to either prevent or promote colorectal cancer (CRC), and treatment with probiotics might be a promising intervention method. The present study aimed to evaluate the potential anti-CRC effects of Lactobacillus coryniformis MXJ32 on a colitis-associated (CA)-CRC mouse model.

METHODS

The CA-CRC mouse model was induced by a single intraperitoneal injection of 10 mg/kg azoxymethane and followed by three 7-day cycles of 2% dextran sulfate sodium in drinking water with a 14-day recovery period. Mice were supplemented with L. coryniformis MXJ32 by oral gavage (1 × 10⁹ CFU/day/mouse). The CA-CRC attenuating effects of this probiotic were assessed via intestinal barrier integrity, inflammation, and gut microenvironment.

RESULTS

Treatment with L. coryniformis MXJ32 could significantly inhibit the total number of tumors and the average tumor diameter. This probiotic administration prevented the damage of intestinal barrier function by enhancing the expression of tight junction proteins (Occludin, Claudin-1, and ZO-1) and recovering the loss of goblet cells. Moreover, L. coryniformis MXJ32 alleviated intestinal inflammation via down-regulating the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-γ, and IL-17a) and chemokines (Cxcl1, Cxcl2, Cxcl3, Cxcl5, and Ccl7). In addition, L. coryniformis MXJ32 supplementation increased the abundance of some beneficial bacteria (such as SCFAs-producing bacteria, Lactobacillus, Bifidobacterium, Akkermansia, and Faecalibaculum) and decreased the abundance of some harmful bacteria (such as pro-inflammatory bacteria, Desulfovibrio and Helicobacter), which in turn attenuated the overexpression of inflammation.

CONCLUSION

Lactobacillus coryniformis MXJ32 could effectively ameliorate CA-CRC via regulating intestinal microenvironment, alleviating inflammation, and intestinal barrier damage, which further suggested that L. coryniformis MXJ32 could be considered as a functional food ingredient for the alleviation of CA-CRC.

Orange fibre effects on nutrient digestibility, fermentation products in faeces and digesta mean retention time in dogs

Fermentable fibres are used in commercial dog food to promote intestinal health by providing substrates for better metabolic activity of the gut microbiota. Brazil is the world's largest producer of oranges, from which it is possible to obtain fibre with a relevant soluble fraction. The present study compared the effects of two inclusions of orange fibre (1% and 3%, on as fed basis) with a negative control (without addition of fibre source) and two positive controls, beet pulp (3%) and purified inulin (1%), totalling five extruded diets for dogs. The experiment followed a randomised block design with 4 blocks of 10 dogs, 2 dogs per food in each block, totalling 8 dogs per diet. The apparent total tract nutrient digestibility was determined by total faecal collection. Faecal pH and fermentation product content were also measured. The digesta mean retention time (DMRT) was evaluated using plastic markers. The inclusion of a 3% fibre source in diets with 3% orange fibre and beet pulp reduced DM, OM, and energy digestibility (p < 0.05). Diets with 3% orange fibre, beet pulp and 1% inulin presented lower crude protein digestibility than the control (p < 0.05). Dietary fibre digestibility was higher for orange fibre-supplemented diets than inulin (p < 0.05). Beet pulp and 3% orange fibre inclusions resulted in increased moisture content in the faeces of dogs (p < 0.05) but did not alter DMRT. Total short-chain fatty acids were higher than the control in the faeces of dogs fed both orange fibre levels and the beet pulp-supplemented diet (p < 0.05), and the inulin diet-fed dogs presented intermediate values. Butyrate was higher in the faeces of dogs fed the diets supplemented with 1% and 3% orange fibre (p < 0.05), and similar values to the control were observed for beet pulp- and inulin-fed animals. Thus, it was concluded that orange fibre presented higher apparent total tract dietary fibre digestibility than beet pulp and had a fermentation profile in the colon that promoted the generation of butyrate, an effect not observed for inulin and beet pulp.

Ganoderma lucidum polysaccharide modulates gut microbiota and immune cell function to inhibit inflammation and tumorigenesis in colon

This study investigated the effects of water-soluble polysaccharide extracted from the sporoderm-removed spores of Ganoderma lucidum (GLP) against AOM/DSS-induced inflammation, tumorigenesis, and gut microbiota modification, which has never been reported before. Our data revealed that GLP (200 and 300 mg/kg) decreased AOM/DSS-induced colitis and tumorigenesis, manifested by significantly reduced disease activity index score, and total number and size of tumors. Furthermore, GLP ameliorated AOM/DSS-induced microbiota dysbiosis, increased short-chain fatty acid production, and alleviated endotoxemia by inhibiting TLR4/MyD88/NF-κB signaling. Besides, GLP profoundly improved gut barrier function as evidenced by increased numbers of goblet cells, MUC2 secretion, and tight junction protein expressions. GLP treatment inhibited macrophage infiltration and downregulated IL-1β, iNOS, and COX-2 expressions. Additionally, GLP inhibited lipopolysaccharides (LPS)-induced inflammation markers and MAPK (JNK and ERK) activation in macrophage RAW264.7, intestinal HT-29, and NCM460 cells. In conclusion, these results indicate that GLP is a promising prebiotic for the treatment of colorectal cancer.

Participation of Short-Chain Fatty Acids and Their Receptors in Gut Inflammation and Colon Cancer

Short-chain fatty acids (SCFAs) are the main metabolites produced by the bacterial fermentation of dietary fiber, and they play a critical role in the maintenance of intestinal health. SCFAs are also essential for modulating different processes, and they have anti-inflammatory properties and immunomodulatory effects. As the inflammatory process predisposes the development of cancer and promotes all stages of tumorigenesis, an antitumor effect has also been associated with SCFAs. This is strongly supported by epidemiological studies showing that a diet rich in fiber is linked to a reduced risk of colon cancer and has significant clinical benefits in patients with inflammatory bowel disease (IBD). SCFAs may signal through the metabolite-sensing G protein-coupled receptors free fatty acid receptor 3 [FFAR3 or G protein-coupled receptor 41 (GPR41)], FFAR2 (GPR43), and GPR109A (also known as hydroxycarboxylic acid receptor 2 or HCAR2) expressed in the gut epithelium and immune cells. This review summarizes the existing knowledge regarding the SCFA-mediated suppression of inflammation and carcinogenesis in IBD and colon cancer.