Products of the colonic microbiota mediate the effects of diet on colon cancer risk

Autoprobiotics in the Treatment of Patients with Colorectal Cancer in the Early Postoperative Period

Despite great advances in the treatment of oncological diseases, the development of medical technologies to prevent or reduce complications of therapy, in particular, those associated with surgery and the introduction of antibiotics, remains relevant. The aim of this study is to evaluate the effectiveness of the use of autoprobiotics based on indigenous non-pathogenic strains of Enterococcus faecium and Enterococcus hirae as a personalized functional food product (PFFP) in the complex therapy of colorectal cancer (CRC) in the early postoperative period. A total of 36 patients diagnosed with CRC were enrolled in the study. Study group A comprised 24 CRC patients who received autoprobiotic therapy in the early postoperative period, while the control group C included 12 CRC patients without autoprobiotic therapy. Prior to surgery and between days 14 and 16 post-surgery, comprehensive evaluations were conducted on all patients, encompassing the following: stool and gastroenterological complaints analysis, examination of the gut microbiota (bacteriological study, quantitative polymerase chain reaction, metagenome analysis), and analysis of interleukins in the serum. Results: The use of autoprobiotics led to a decrease in dyspeptic complaints after surgery. It was also associated with the absence of postoperative complications, did not cause any side effects, and led to a decrease in the level of pro-inflammatory cytokines (IL-6 and IL-18) in the blood serum. The use of autoprobiotics led to positive changes in the structure of escherichia and enterococci populations, the elimination of Parvomonas micra and Fusobacterium nucleatum, and a decrease in the quantitative content of Clostridium perfringens and Akkermansia muciniphila. Metagenomic analysis (16S rRNA) revealed an increase in alpha diversity. Conclusion: The introduction of autoprobiotics in the postoperative period is a highly effective and safe approach in the complex treatment of CRC. Future studies will allow the discovery of additional fine mechanisms of autoprobiotic therapy and its impact on the digestive, immune, endocrine, and neural systems.

Role of the Gut Microbiome and Bacterial Amyloids in the Development of Synucleinopathies

Less than ten years ago, evidence began to accumulate about association between the changes in the composition of gut microbiota and development of human synucleinopathies, in particular sporadic form of Parkinson's disease. We collected data from more than one hundred and thirty experimental studies that reported similar results and summarized the frequencies of detection of different groups of bacteria in these studies. It is important to note that it is extremely rare that a unidirectional change in the population of one or another group of microorganisms (only an elevation or only a reduction) was detected in the patients with Parkinson's disease. However, we were able to identify several groups of bacteria that were overrepresented in the patients with Parkinson's disease in the analyzed studies. There are various hypotheses about the molecular mechanisms that explain such relationships. Usually, α-synuclein aggregation is associated with the development of inflammatory processes that occur in response to the changes in the microbiome. However, experimental evidence is accumulating on the influence of bacterial proteins, including amyloids (curli), as well as various metabolites, on the α-synuclein aggregation. In the review, we provided up-to-date information about such examples.

Opening avenues for treatment of neurodegenerative disease using post-biotics: Breakthroughs and bottlenecks in clinical translation

Recent studies have indicated the significant involvement of the gut microbiome in both human physiology and pathology. Additionally, therapeutic interventions based on microbiome approaches have been employed to enhance overall health and address various diseases including aging and neurodegenerative disease (ND). Researchers have explored potential links between these areas, investigating the potential pathogenic or therapeutic effects of intestinal microbiota in diseases. This article provides a summary of established interactions between the gut microbiome and ND. Post-biotic is believed to mediate its neuroprotection by elevating the level of dopamine and reducing the level of α-synuclein in substantia nigra, protecting the loss of dopaminergic neurons, reducing the aggregation of NFT, reducing the deposition of amyloid β peptide plagues and ameliorating motor deficits. Moreover, mediates its neuroprotective activity by inhibiting the inflammatory response (decreasing the expression of TNFα, iNOS expression, free radical formation, overexpression of HIF-1α), apoptosis (i.e. active caspase-3, TNF-α, maintains the level of Bax/Bcl-2 ratio) and promoting BDNF secretion. It is also reported to have good antioxidant activity. This review offers an overview of the latest findings from both preclinical and clinical trials concerning the use of post-biotics in ND.

Low-dose daily folic acid (400 μg) supplementation does not affect regulation of folate transporters found present throughout the terminal ileum and colon of humans: a randomized clinical trial

BACKGROUND

Folic acid supplementation during the periconceptional period reduces the risk of neural tube defects in infants, but concern over chronic folic acid exposure remains. An improved understanding of folate absorption may clarify potential risks. Folate transporters have been characterized in the small intestine, but less so in the colon of healthy, free-living humans. The impact of folic acid fortification or supplementation on regulation of these transporters along the intestinal tract is unknown.

OBJECTIVE

The objective was to characterize expression of folate transporters/receptor (FT/R) and folate hydrolase, glutamate carboxypeptidase II (GCPII), from the terminal ileum and throughout the colon of adults and assess the impact of supplemental folic acid.

METHODS

In this 16-wk open-labeled randomized clinical trial, adults consumed a low folic acid-containing diet, a folate-free multivitamin, and either a 400 μg folic acid supplement or no folic acid supplement. Dietary intakes and blood were assessed at baseline, 8 wk, and 16 wk (time of colonoscopy). Messenger RNA (mRNA) expression and protein expression of FT/R and GCPII were assessed in the terminal ileum, cecum, and ascending and descending colon.

RESULTS

Among 24 randomly assigned subjects, no differences in dietary folate intake or blood folate were observed at baseline. Mean ± SD red blood cell folate at 16 wk was 1765 ± 426 and 911 ± 242 nmol/L in the 400 and 0 μg folic acid group, respectively (P < 0.0001). Reduced folate carrier, proton-coupled folate transporter, and folate-receptor alpha expression were detected in the terminal ileum and colon, as were efflux transporters of breast cancer resistance protein and multidrug resistance protein-3. Other than a higher mRNA expression of FR-alpha and GCPII in the 400 μg supplement group in the ascending colon, no treatment differences were observed (P < 0.02).

CONCLUSIONS

Folate transporters are present throughout the terminal ileum and colon; there is little evidence that a low dose of folic acid supplementation affects colonic absorption. This trial was registered at clinicaltrials.gov as NCT03421483.

Diet-mediated gut microbial community modulation and signature metabolites as potential biomarkers for early diagnosis, prognosis, prevention and stage-specific treatment of colorectal cancer

BACKGROUND

Over the last decade, studies have shown an increased incidence of colorectal cancer (CRC), particularly early onset colorectal cancer (EOCRC). Researchers have demonstrated that dietary behavior, especially among young adults, influences alterations in the gut microbial community, leading to an increased accumulation of pathogenic gut microbiota and a decrease in beneficial ones. Unfortunately, CRC is likely to be diagnosed at a late stage, increasing CRC-related mortality. However, this alteration in the gut microbiota (gut dysbiosis) can be harnessed as a biomarker for non-invasive diagnosis, prognosis, prevention, and treatment of CRC in an effort to prevent late diagnosis and poor prognosis associated with CRC.

AIM OF REVIEW

This review discusses identification of potential biomarkers by targeting diet-mediated gut dysbiosis for the stage-specific diagnosis, prognosis, treatment, and prevention of CRC. Our findings provide a comprehensive insight into the potential of protumorigenic bacteria (e.g.pathogenic Escherichia coli,enterotoxigenic Bacteroides fragilis and Fusobacterium nucleatum) and their metabolites (e.g., colibactin and B. fragilis toxin) from gut dysbiosis as biomarkers for the diagnosis of CRC.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Collectively, a detailed understanding of the available data from current studies suggests that, further research on quantification of metabolites and stage-specific pathogenic microbial abundance is required for the diagnosis and treatment of CRC based on microbial dysbiosis. Specifically, future studies on faecal samples, from patient with CRC, should be conducted for F. nucleatum among different opportunistic bacteria, given its repeated occurrence in faecal samples and CRC biopsies in numerous studies. Finally, we discuss the potential of faecal microbial transplantation (FMT) as an intervention to restore damaged gut microbiota during CRC treatment and management.

Dissecting Microbiome-Derived SCFAs in Prostate Cancer: Analyzing Gut Microbiota, Racial Disparities, and Epigenetic Mechanisms

Prostate cancer (PCa) continues to be the most diagnosed cancer and the second primary cause of fatalities in men globally. There is an abundance of scientific evidence suggesting that the human microbiome, together with its metabolites, plays a crucial role in carcinogenesis and has a significant impact on the efficacy of anticancer interventions in solid and hematological cancers. These anticancer interventions include chemotherapy, immune checkpoint inhibitors, and targeted therapies. Furthermore, the microbiome can influence systemic and local immune responses using numerous metabolites such as short-chain fatty acids (SCFAs). Despite the lack of scientific data in terms of the role of SCFAs in PCa pathogenesis, recent studies show that SCFAs have a profound impact on PCa progression. Several studies have reported racial/ethnic disparities in terms of bacterial content in the gut microbiome and SCFA composition. These studies explored microbiome and SCFA racial/ethnic disparities in cancers such as colorectal, colon, cervical, breast, and endometrial cancer. Notably, there are currently no published studies exploring microbiome/SCFA composition racial disparities and their role in PCa carcinogenesis. This review discusses the potential role of the microbiome in PCa development and progression. The involvement of microbiome-derived SCFAs in facilitating PCa carcinogenesis and their effect on PCa therapeutic response, particularly immunotherapy, are discussed. Racial/ethnic differences in microbiome composition and SCFA content in various cancers are also discussed. Lastly, the effects of SCFAs on PCa progression via epigenetic modifications is also discussed.

Effects of Broad-Spectrum Antibiotic Treatment or Germ-Free Status on Endurance Performance and Exercise Adaptations in Mice

PURPOSE

Endurance exercise alters the gut microbiome independently of diet. The extent to which gut microbes are responsible for physiologic adaptations to exercise training is unknown. The purpose of these experiments was to determine the role of gut microbes in performance and muscle adaptation to 6 wk of voluntary wheel running (VWR) in mice.

METHODS

We depleted microbes with broad-spectrum antibiotic (ABX) treatment and used germ-free (GF) mice to determine effects on adaptations to VWR. Male and female C57Bl/6 mice ( n = 56) were assigned to daily VWR or sedentary conditions. After the intervention, treadmill endurance and glucose tolerance were assessed, and gastrocnemius and soleus tissues were harvested and analyzed for citrate synthase (CS) enzyme activity and expression of exercise training-sensitive genes.

RESULTS

ABX treatment and GF status resulted in VWR volumes ~22% and 26% lower than controls, respectively. Analysis of variance revealed that, although VWR increased treadmill endurance, ABX had no effect. GF status significantly reduced treadmill performance in trained GF mice after training. VWR increased gastrocnemius CS enzyme activity in all groups, and ABX and GF status did not reduce the VWR effect. VWR also increased muscle expression of PGC1a, but this was not affected by ABX treatment.

CONCLUSIONS

ABX treatment and GF status reduced VWR behavior but did not affect VWR-induced adaptations in endurance capacity, CS activity, or expression of muscle metabolic genes. However, GF status reduced endurance capacity. These data indicated that reducing microbes in adulthood does not inhibit endurance training adaptations in C57Bl/6 mice, but that GF mice possess a reduced responsiveness to endurance exercise training, perhaps because of a developmental defect associated with lack of microbes from birth.

Human matters in asthma: Considering the microbiome in pulmonary health

Microbial communities form an important symbiotic ecosystem within humans and have direct effects on health and well-being. Numerous exogenous factors including airborne triggers, diet, and drugs impact these established, but fragile communities across the human lifespan. Crosstalk between the mucosal microbiota and the immune system as well as the gut-lung axis have direct correlations to immune bias that may promote chronic diseases like asthma. Asthma initiation and pathogenesis are multifaceted and complex with input from genetic, epigenetic, and environmental components. In this review, we summarize and discuss the role of the airway microbiome in asthma, and how the environment, diet and therapeutics impact this low biomass community of microorganisms. We also focus this review on the pediatric and Black populations as high-risk groups requiring special attention, emphasizing that the whole patient must be considered during treatment. Although new culture-independent techniques have been developed and are more accessible to researchers, the exact contribution the airway microbiome makes in asthma pathogenesis is not well understood. Understanding how the airway microbiome, as a living entity in the respiratory tract, participates in lung immunity during the development and progression of asthma may lead to critical new treatments for asthma, including population-targeted interventions, or even more effective administration of currently available therapeutics.

Short-chain fatty acid concentrations in the incidence and risk-stratification of colorectal cancer: a systematic review and meta-analysis

BACKGROUND

The beneficial role of gut microbiota and bacterial metabolites, including short-chain fatty acids (SCFAs), is well recognized, although the available literature around their role in colorectal cancer (CRC) has been inconsistent.

METHODS

We performed a systematic review and meta-analysis to examine the associations of fecal SCFA concentrations to the incidence and risk of CRC. Data extraction through Medline, Embase, and Web of Science was carried out from database conception to June 29, 2022. Predefined inclusion/exclusion criteria led to the selection of 17 case-control and six cross-sectional studies for quality assessment and analyses. Studies were categorized for CRC risk or incidence, and RevMan 5.4 was used to perform the meta-analyses. Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated using a random-effects model. Studies lacking quantitation were included in qualitative analyses.

RESULTS

Combined analysis of acetic, propionic, and butyric acid revealed significantly lower concentrations of these SCFAs in individuals with a high-risk of CRC (SMD = 2.02, 95% CI 0.31 to 3.74, P = 0.02). Additionally, CRC incidence was higher in individuals with lower levels of SCFAs (SMD = 0.45, 95% CI 0.19 to 0.72, P = 0.0009), compared to healthy individuals. Qualitative analyses identified 70.4% of studies reporting significantly lower concentrations of fecal acetic, propionic, butyric acid, or total SCFAs in those at higher risk of CRC, while 66.7% reported significantly lower concentrations of fecal acetic and butyric acid in CRC patients compared to healthy controls.

CONCLUSIONS

Overall, lower fecal concentrations of the three major SCFAs are associated with higher risk of CRC and incidence of CRC.

Role of the Gut–Brain Axis, Gut Microbial Composition, Diet, and Probiotic Intervention in Parkinson’s Disease

Parkinson’s disease (PD) is the second-most prevalent neurodegenerative or neuropsychiatric disease, affecting 1% of seniors worldwide. The gut microbiota (GM) is one of the key access controls for most diseases and disorders. Disturbance in the GM creates an imbalance in the function and circulation of metabolites, resulting in unhealthy conditions. Any dysbiosis could affect the function of the gut, consequently disturbing the equilibrium in the intestine, and provoking pro-inflammatory conditions in the gut lumen, which send signals to the central nervous system (CNS) through the vagus enteric nervous system, possibly disturbing the blood–brain barrier. The neuroinflammatory conditions in the brain cause accumulation of α-syn, and progressively develop PD. An important aspect of understanding and treating the disease is access to broad knowledge about the influence of dietary supplements on GM. Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Probiotic supplementation improves the function of the CNS, and improves the motor and non-motor symptoms of PD. Probiotic supplementation could be an adjuvant therapeutic method to manage PD. This review summarizes the role of GM in health, the GM–brain axis, the pathogenesis of PD, the role of GM and diet in PD, and the influence of probiotic supplementation on PD. The study encourages further detailed clinical trials in PD patients with probiotics, which aids in determining the involvement of GM, intestinal mediators, and neurological mediators in the treatment or management of PD.

Relevance of Biotin Deficiency in Patients with Inflammatory Bowel Disease and Utility of Serum 3 Hydroxyisovaleryl Carnitine as a Practical Everyday Marker

Background: Biotin, a water-soluble B vitamin, has demonstrable anti-inflammatory properties. A biotin-deficient diet induced a colitis-like phenotype in mice, alleviable by biotin substitution. Mice with dextran sulfate sodium (DSS)-induced colitis showed biotin deficiency and diminished levels of sodium-dependent multivitamin transporter, a protein involved in biotin absorption. Biotin substitution induced remission by reducing activation of NF-κB, a transcription factor involved in intestinal permeability and inflammatory bowel disease (IBD). We investigated for the first time a possible clinical role of biotin status in IBD. Methods: In a comparative, retrospective, cross-sectional study, serum samples of 138 patients with IBD (67 female; 72 Crohn’s disease (CD), 66 ulcerative colitis (UC)) aged 18–65 years and with a mean age (±SD) of 42.5 ± 14.3 years as well as 80 healthy blood donors (40 female; 40.0 ± 10.0 years; range 20–60 years) were analyzed. Inflammation was defined as hsCRP ≥5 mg/L, and to determine biotin status, serum 3-hydroxyisovaleryl carnitine (3HIVc) levels were measured by LC-MS/MS. Results: A total of 138 patients with IBD (67f; 72CD/66 UC; 42.5 ± 14.3 years) were enrolled: 83/138 had inflammation. Mean serum 3HIVc levels were significantly higher in IBD patients but unaffected by inflammation. Biotin deficiency (95th percentile of controls: >30 nmol/L 3HIVc) was significantly more common in IBD patients versus controls. Conclusion: High serum 3HIVc levels and biotin deficiency were associated with IBD but not inflammatory activity or disease type. Our findings suggest biotin may play a role as cause or effect in IBD pathogenesis. Routine assessment and supplementation of biotin may ameliorate IBD and support intestinal integrity.

Early-onset colorectal cancer: Current insights and future directions

Early-onset colorectal cancer (EOCRC) has seen an alarming rise worldwide over the past two decades. The reason for this global trend is poorly understood. EOCRC appears to have its own unique clinical and molecular features when compared with late-onset colorectal cancer. Younger patients appear to have more distal or rectal disease, a more advanced stage of disease at presentation, and more unfavorable histological features. Identifying risk factors for EOCRC is the first step in mitigating the rising burden of this disease. Here we summarize several noteworthy biological factors and environmental exposures that are postulated to be responsible culprits. This can hopefully translate in clinical practice to the development of better risk stratification tool for identifying high-risk individuals for early colorectal cancer screening, and identifying areas needed for further research to curb this rising trend.

Progress in the Study of Colorectal Cancer Caused by Altered Gut Microbiota After Cholecystectomy

Epidemiological studies have found an increased incidence of colorectal cancer (CRC) in people who undergo cholecystectomy compared to healthy individuals. After cholecystectomy, bile enters the duodenum directly, unregulated by the timing of meals. Disruption of the balance of bile acid metabolism and increased production of primary bile acids, which in turn affects the composition and abundance of intestinal microorganisms. The link among cholecystectomy, the gut microbiota, and the occurrence and development of CRC is becoming clearer. However, due to the complexity of the microbial community, the mechanistic connections are less well understood. In this review, we summarize the changes of gut microbiota after cholecystectomy and illuminate the potential mechanisms on CRC, such as inflammation and immune regulation, production of genotoxins, metabolism of dietary ingredients, activation of signaling pathways, and so on. By reviewing these, we aimed to unravel the interactions between the gut microbiota and its host and be better positioned to develop treatments for CRC after cholecystectomy.

Short-Chain and Total Fatty Acid Profile of Faeces or Plasma as Predictors of Food-Responsive Enteropathy in Dogs: A Preliminary Study

Simple Summary

Food-responsive enteropathy is the most common diagnosis given for dogs with chronic enteropathy, and there are no tests that can replace treatment trials. Furthermore, there is a lack of information on the specific nutritional status of these patients regarding the lipid profile that could relate them to the state of health/disease. This study evaluated differences in short-chain fatty acids and the total fatty acid profile of faeces and plasma as possible indicators of food-responsive enteropathy (FRE), as well as its relationship with body condition and the chronic enteropathy activity index. Changes in the long-chain fatty acid of plasma, and short-chain, branched and odd-chain fatty acids of faeces were detected in sick dogs, and high correlations were observed between some of these compounds and the existing calculated indices.

Abstract

The aim of this study was to evaluate differences in short-chain fatty acids (SCFAs) and the total fatty acid profile of faeces or plasma as possible indicators of FRE in comparison with healthy dogs. FRE dogs had a lower concentration (p = 0.026) of plasma α-tocopherol as an indicator of the oxidative status of the animal, and lower C20:5n-3 (p = 0.033), C22:5n-3 (p = 0.005), polyunsaturated fatty acids (PUFA) (p = 0.021) and n-6 (p = 0.041) when compared with the control dogs; furthermore, sick dogs had higher proportions of plasma C20:3n-6 (p = 0.0056). The dogs with FRE showed a decrease in the production of faecal levels of SCFAs, mainly propionic acid (C3) (p = 0.0001) and isovaleric acid (iC5) (p = 0.014). FRE dogs also had a lower proportion of C15:0 (p = 0.0003), C16:1n-9 (p = 0.0095), C16:1n-7 (p = 0.0001), C20:5n-3 (p = 0.0034) and monounsaturated fatty acids (p = 0.0315), and tended to have lower n-3 (p = 0.058) and a reduced desaturase activity index in the stool when compared with the control group. However, the dogs with chronic enteropathy tended to have greater C20:4n-6 (p = 0.065) in their faeces as signs of damage at the intestinal level. The faecal parameters were better predictors than plasma. The highest correlations between faecal odd-chain, medium- or long-chain fatty acids and SCFAs were observed for C15:0 that correlated positively with faecal acetic acid (C2) (r = 0.72, p = 0.004), propionic acid (r = 0.95, p = 0.0001), isobutyric acid (iC4) (r = 0.59, p = 0.027) and isovaleric acid (r = 0.64, p = 0.0136), as well as with total SCFAs (r = 0.61, p = 0.02). Conversely, faecal C20:4n-6 showed a high inverse correlation (r = −0.83, p = 0.0002) with C2 and C3 (r = −0.59, p = 0.027). Canine inflammatory bowel disease (IBD) activity (CIBDAI) index correlated negatively mainly with faecal measurements, such as C3 (r = −0.869, p = 0.0005) and C15:0 (r = −0.825, p = 0.0018), followed by C16:1/C16:0 (r = −0.66, p= 0.0374) and iC5 (r = −0.648, p = 0.0310), which would indicate that these fatty acids could be good non-invasive indicators of the chronic inflammatory status, specifically FRE.

Succinylsulfathiazole modulates the mTOR signaling pathway in the liver of c57BL/6 mice via a folate independent mechanism

Researchers studying the effect of folate restriction on rodents have resorted to the use of the antibiotic succinylsulfathiazole (SST) in the folate depleted diet to induce a folate deficient status. SST has been used extensively in rodent studies since the 1940s. Its localized effect on the gut bacteria as well as its effectiveness in reducing folate producing species is well documented. The possible overlap between the pathways affected by folate depletion and SST could potentially produce a confounding variable in such studies. In our novel study, we analyzed the effect of SST on folate levels in c57Bl/6 male mice fed folate supplemented and deficient diets. We did not observe any significant difference on growth and weight gain at 21 weeks. SST did not significantly affect folate levels in the plasma, liver and colon tissues; however, it did alter energy metabolism and expression of key genes in the mTOR signaling pathway in the liver. This research sheds light on a possible confounding element when using SST to study folate depletion due to the potential overlap with multiple critical pathways such as mTOR. SUMMARY: The antibiotic succinylsulfathiazole (SST) is used to reduce folate producing bacteria in rodent folate depletion studies. SST can modulate critical energy and nutrient sensing pathways converging onto mTOR signaling, and potentially confounding cancer studies.

The Relationship Between the Gut Microbiome and Neurodegenerative Diseases

Many recent studies have shown that the gut microbiome plays important roles in human physiology and pathology. Also, microbiome-based therapies have been used to improve health status and treat diseases. In addition, aging and neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, have become topics of intense interest in biomedical research. Several researchers have explored the links between these topics to study the potential pathogenic or therapeutic effects of intestinal microbiota in disease. But the exact relationship between neurodegenerative diseases and gut microbiota remains unclear. As technology advances, new techniques for studying the microbiome will be developed and refined, and the relationship between diseases and gut microbiota will be revealed. This article summarizes the known interactions between the gut microbiome and neurodegenerative diseases, highlighting assay techniques for the gut microbiome, and we also discuss the potential therapeutic role of microbiome-based therapies in diseases.

Racial and ethnic disparities in colorectal cancer incidence and mortality

The occurrence of colorectal cancer (CRC) shows a large disparity among recognized races and ethnicities in the U.S., with Black Americans demonstrating the highest incidence and mortality from this disease. Contributors for the observed CRC disparity appear to be multifactorial and consequential that may be initiated by structured societal issues (e.g., low socioeconomic status and lack of adequate health insurance) that facilitate abnormal environmental factors (through use of tobacco and alcohol, and poor diet composition that modifies one's metabolism, microbiome and local immune microenvironment) and trigger cancer-specific immune and genetic changes (e.g., localized inflammation and somatic driver gene mutations). Mitigating the disparity by prevention through CRC screening has been demonstrated; this has not been adequately shown once CRC has developed. Acquiring additional knowledge into the science behind the observed disparity will inform approaches towards abating both the incidence and mortality of CRC between U.S. racial and ethnic groups.

Treatment and mechanism of fecal microbiota transplantation in mice with experimentally induced ulcerative colitis

Restoring intestinal microbiota dysbiosis with fecal microbiota transplantation is considered as a promising treatment for ulcerative colitis. However, the mechanisms underlying its relieving effects remain unclear. Ulcerative colitis pathogenesis is associated with the involvement of immune cells and inflammatory cytokines. Here, we aimed to investigate the effect of fecal microbiota transplantation on T cell cytokines in a dextran sulfate sodium-induced ulcerative colitis mouse model. Five-aminosalicylic acid (5-ASA) was used as the positive control. Male C57BL/6 mice were randomly assigned to control, model (UC), UC + FMT, and UC + 5-ASA groups. Each group consisted of five mice. The establishment of the mouse model was verified by fecal occult-blood screening and hematoxylin-eosin staining. Results showed that fecal microbiota transplantation reduced colonic inflammation, significantly decreased T helper (Th)1 and Th17 cells, interferon-gamma, interleukin-2 and interleukin-17, as well as significantly increased Th2 and regulatory T (Treg) cells, interleukin-4, interleukin-10, and transforming growth factor-beta, and improved routine blood count. Furthermore, 16S rRNA gene-sequencing analysis showed a significant increase in the relative abundance of genus Akkermansia and a significant decrease in the relative abundance of genus Helicobacter in the ulcerative colitis group. Fecal microbiota transplantation restored the profile of the intestinal microbiota to that of the control group. These findings demonstrated the capability of fecal microbiota transplantation in controlling experimentally induced ulcerative colitis by improving Th1/Th2 and Th17/Treg imbalance through the regulation of intestinal microbiota.

The Role of Gut Barrier Dysfunction and Microbiome Dysbiosis in Colorectal Cancer Development

Accumulating evidence indicates that breakdown of the+ protective mucosal barrier of the gut plays a role in colorectal cancer (CRC) development. Inflammation and oxidative stress in the colonic epithelium are thought to be involved in colorectal carcinogenesis and the breakdown of the integrity of the colonic barrier may increase the exposure of colonocytes to toxins from the colonic milieu, enhancing inflammatory processes and release of Reactive Oxygen Species (ROS). The aetiological importance of the gut microbiome and its composition - influenced by consumption of processed meats, red meats and alcoholic drinks, smoking, physical inactivity, obesity - in CRC development is also increasingly being recognized. The gut microbiome has diverse roles, such as in nutrient metabolism and immune modulation. However, microbial encroachment towards the colonic epithelium may promote inflammation and oxidative stress and even translocation of species across the colonic lumen. Recent research suggests that factors that modify the above mechanisms, e.g., obesity and Western diet, also alter gut microbiota, degrade the integrity of the gut protective barrier, and expose colonocytes to toxins. However, it remains unclear how obesity, lifestyle and metabolic factors contribute to gut-barrier integrity, leading to metabolic disturbance, colonocyte damage, and potentially to CRC development. This review will discuss the interactive roles of gut-barrier dysfunction, microbiome dysbiosis, and exposure to endogenous toxins as another mechanism in CRC development, and how biomarkers of colonic mucosal barrier function may provide avenues for disease, prevention and detection.

Osteoprotective effect of green tea polyphenols and annatto-extracted tocotrienol in obese mice is associated with enhanced microbiome vitamin K2 biosynthetic pathways

The role of the gut microbiome in bone health has received significant attention in the past decade. We investigated the effects of green tea polyphenols (GTP) and annatto-extracted tocotrienols (AT) on bone properties and gut microbiome in obese mice. Male mice were assigned to a two (no AT vs. 400 mg/kg diet AT) × two (no GTP vs. 0.5% w/v GTP) factorial design, namely control, G, T, and G+T group respectively, for 14 weeks. The 4th lumbar vertebra (LV-4) and femur were harvested for bone microstructural analysis using μ-CT. Microbiome analysis using 16S rRNA gene sequencing of cecal feces was performed. AT increased bone volume at distal femur. GTP increased serum procollagen type 1 N-terminal propeptide concentration, bone volume at the distal femur and the LV-4, and trabecular number at distal femur; whereas GTP decreased trabecular separation at distal femur. Interactions between GTP and AT were observed in serum C-terminal telopeptide of type I collagen level (control>G=T=G+T) as well as the cortical bone area (control<G=T=G+T) and thickness (T≥G+T≥G≥control) at femur mid-diaphysis. Redundancy analysis showed a significant difference in the gut microbiome profile among different groups and the relative abundance of Akkermansia muciniphila, Clostridum saccharogumia, and Subdoligranulum variabile was increased in the GTP- and AT-supplemented groups. Functional profiling of the gut microbiome showed the combination of GTP and AT induced biosynthetic pathways for vitamin K₂. Our results suggest that GTP and AT supplementation benefits bone properties in obese mice through modifying gut microbiome composition and function.

Lipidomic-Based Advances in Diagnosis and Modulation of Immune Response to Cancer

While immunotherapies for diverse types of cancer are effective in many cases, relapse is still a lingering problem. Like tumor cells, activated immune cells have an anabolic metabolic profile, relying on glycolysis and the increased uptake and synthesis of fatty acids. In contrast, immature antigen-presenting cells, as well as anergic and exhausted T-cells have a catabolic metabolic profile that uses oxidative phosphorylation to provide energy for cellular processes. One goal for enhancing current immunotherapies is to identify metabolic pathways supporting the immune response to tumor antigens. A robust cell expansion and an active modulation via immune checkpoints and cytokine release are required for effective immunity. Lipids, as one of the main components of the cell membrane, are the key regulators of cell signaling and proliferation. Therefore, lipid metabolism reprogramming may impact proliferation and generate dysfunctional immune cells promoting tumor growth. Based on lipid-driven signatures, the discrimination between responsiveness and tolerance to tumor cells will support the development of accurate biomarkers and the identification of potential therapeutic targets. These findings may improve existing immunotherapies and ultimately prevent immune escape in patients for whom existing treatments have failed.

Vitamin Biosynthesis by Human Gut Butyrate-Producing Bacteria and Cross-Feeding in Synthetic Microbial Communities

We investigated the requirement of 15 human butyrate-producing gut bacterial strains for eight B vitamins and the proteinogenic amino acids by a combination of genome sequence analysis and in vitro growth experiments. The Ruminococcaceae species Faecalibacterium prausnitzii and Subdoligranulum variabile were auxotrophic for most of the vitamins and the amino acid tryptophan. Within the Lachnospiraceae, most species were prototrophic for all amino acids and several vitamins, but biotin auxotrophy was widespread. In addition, most of the strains belonging to Eubacterium rectale and Roseburia spp., but few of the other Lachnospiraceae strains, were auxotrophic for thiamine and folate. Synthetic coculture experiments of five thiamine or folate auxotrophic strains with different prototrophic bacteria in the absence and presence of different vitamin concentrations were carried out. This demonstrated that cross-feeding between bacteria does take place and revealed differences in cross-feeding efficiency between prototrophic strains. Vitamin-independent growth stimulation in coculture compared to monococulture was also observed, in particular for F. prausnitzii A2-165, suggesting that it benefits from the provision of other growth factors from community members. The presence of multiple vitamin auxotrophies in the most abundant butyrate-producing Firmicutes species found in the healthy human colon indicates that these bacteria depend upon vitamins supplied from the diet or via cross-feeding from other members of the microbial community.IMPORTANCE Microbes in the intestinal tract have a strong influence on human health. Their fermentation of dietary nondigestible carbohydrates leads to the formation of health-promoting short-chain fatty acids, including butyrate, which is the main fuel for the colonic wall and has anticarcinogenic and anti-inflammatory properties. A good understanding of the growth requirements of butyrate-producing bacteria is important for the development of efficient strategies to promote these microbes in the gut, especially in cases where their abundance is altered. The demonstration of the inability of several dominant butyrate producers to grow in the absence of certain vitamins confirms the results of previous in silico analyses. Furthermore, establishing that strains prototrophic for thiamine or folate (butyrate producers and non-butyrate producers) were able to stimulate growth and affect the composition of auxotrophic synthetic communities suggests that the provision of prototrophic bacteria that are efficient cross feeders may stimulate butyrate-producing bacteria under certain in vivo conditions.

Non-Digestible Carbohydrate and the Risk of Colorectal Neoplasia: A Systematic Review

Non-digestible carbohydrate (NDC) is a fiber that can be fermented into short chain fatty acids (SCFAs) in gut, represented by resistant starch (RS) and inulin. Colorectal cancer (CRC) is one of the most common malignant cancer. Pre-clinical studies have reported that NDC can produce SCFAs to protect the gut epithelium, which is associated with prevention of CRC, but this role in clinical trails is controversial. In this review, we discusses whether RS and inulin should be offered to cancer/precancerous patients or healthy subjects to decrease their risk of CRC. A multiple database search was conducted for studies published on RS/inulin supplementation as a chemopreventive method from 1989 to 2019. The meta-analysis showed the total SCFAs and butyrate concentrations (P = 0.84; P = 0.79), and excretions (P = 0.55; P = 0.63) in feces did not increase significantly after RS/inulin supplementation. Only two studies reported that RS/inulin inhibit the proliferation of large bowel epithelial, whereas 15 studies showed that it does not decrease the risk of neoplasia. RS/inulin restored the promotion of tumor risk factors in two studies and did not in four studies. Notably, the other four studies showed that RS increases pro-tumorigenesis mechanisms. The clinical evidences consistently show that RS/inulin is ineffective for preventing colorectal neoplasia.

Gut Microbiome and Osteoporosis

Gut microbiome refers to the microbes that live in human digestive tract and are symbiotic with the human body. They participate in the regulation of various physiological and pathological processes of the human body and are associated with various diseases. The pathological process of osteoporosis is affected by gut microbes. The molecular mechanisms of osteoporosis mainly include: 1) Intestinal barrier and nutrient absorption (involving SCFAs). 2) Immunoregulation (Th-17 and T-reg cells balance). 3) Regulation of intestinal-brain axis (involving 5-HT). Gut microbes can increase bone mass and improve osteoporosis by inhibiting osteoclast proliferation and differentiation, inducing apoptosis, reducing bone resorption, or promoting osteoblast proliferation and maturation. However, the therapeutic effect of gut microbes on osteoporosis remains to be further proven. At present, some of the findings on the impact of gut microbes on osteoporosis has been applied in clinical, including early diagnosis and intervention of osteoporosis and adjuvant therapy. In this article, we reviewed the molecular mechanisms underlying the regulatory effect of gut microbes on osteoporosis and the clinical practice of using gut microbes to improve bone health.

Bacteria increase host micronutrient availability: mechanisms revealed by studies in C. elegans

Micronutrients cannot be synthesized by humans and are obtained from three different sources: diet, gut microbiota, and oral supplements. The microbiota generates significant quantities of micronutrients, but the contribution of these compounds to total uptake is unclear. The role of bacteria in the synthesis and uptake of micronutrients and supplements is widely unexplored and may have important implications for human health. The efficacy and safety of several micronutrient supplements, including folic acid, have been questioned due to some evidence of adverse effects on health. The use of the simplified animal-microbe model, Caenorhabditis elegans, and its bacterial food source, Escherichia coli, provides a controllable system to explore the underlying mechanisms by which bacterial metabolism impacts host micronutrient status. These studies have revealed mechanisms by which bacteria may increase the bioavailability of folic acid, B12, and iron. These routes of uptake interact with bacterial metabolism, with the potential to increase bacterial pathogenesis, and thus may be both beneficial and detrimental to host health.

Comparison of the effects of four commercially available prescription diet regimens on the fecal microbiome in healthy dogs

The effects of prescription diets on canine intestinal microbiota are unknown. In this study, we used next generation sequencing to investigate the impact of four commercially available prescription diet regimens on the fecal microbiome in six healthy dogs. The diet regimens used were as follows: weight-loss diet, low-fat diet, renal diet, and anallergenic diet. We found a significantly decreased proportion of phylum Actinobacteria with the weight-loss diet compared to the anallergenic diet. There were no significant differences in the proportion of phylum Bacteroidetes between the four diets. The proportion of phylum Firmicutes was significantly decreased with the weight-loss diet compared to the anallergenic diet. The proportion of phylum Fusobacteria was significantly increased with the weight-loss diet compared to the anallergenic diet. There were no significant differences in the proportion of phylum Proteobacteria after consumption of the four diets. We therefore demonstrated that commercial prescription diet influences the fecal microbiome in healthy dogs. These results might be useful when choosing a prescription diet for targeting a disease.

Race, the microbiome and colorectal cancer

In the past decade, more cancer researchers have begun to understand the significance of cancer prevention, which has prompted a shift in the increasing body of scientific literature. An area of fascination and great potential is the human microbiome. Recent studies suggest that the gut microbiota has significant roles in an individual's ability to avoid cancer, with considerable focus on the gut microbiome and colorectal cancer. That in mind, racial disparities with regard to colorectal cancer treatment and prevention are generally understudied despite higher incidence and mortality rates among Non-Hispanic Blacks compared to other racial and ethnic groups in the United States. A comprehension of ethnic differences with relation to colorectal cancer, dietary habits and the microbiome is a meritorious area of investigation. This review highlights literature that identifies and bridges the gap in understanding the role of the human microbiome in racial disparities across colorectal cancer. Herein, we explore the differences in the gut microbiota, common short chain fatty acids produced in abundance by microbes, and their association with racial differences in cancer acquisition.

Tamoxifen-induced, intestinal-specific deletion of Slc5a6 in adult mice leads to spontaneous inflammation: involvement of NF-κB, NLRP3, and gut microbiota

The sodium-dependent multivitamin transporter (SMVT; SLC5A6) is involved in intestinal absorption of vitamin B7 (biotin). We have previously shown that mice with an embryonic intestinal-specific SMVT knockout (KO) develop biotin deficiency and severe spontaneous intestinal inflammation in addition to growth retardation, developmental delays, and death within the first 6-7 wk of life. The profound morbidity and mortality associated with the SMVT-KO has limited our ability to further characterize the intestinal inflammation and other sequelae of this deletion in adult mice with a mature gut microbiota. To overcome this limitation, we generated an intestine-specific, tamoxifen-inducible, conditional SMVT-KO (SMVT-icKO). Our results showed that adult SMVT-icKO mice have reduced body weight, biotin deficiency, shorter colonic length, and bloody diarrhea compared with age- and sex-matched control littermates. All SMVT-icKO mice also developed spontaneous intestinal inflammation associated with induction of calprotectin (S100a8/S100a9), proinflammatory cytokines (IL-1β, TNF-α, IFN-γ, and IL-6), and an increase in intestinal permeability. Additionally, the intestines of SMVT-icKO showed activation of the NF-κB pathway and the nucleotide-binding domain and leucine-rich repeat pyrin 3 domain (NLRP3) inflammasome. Notably, administration of broad-spectrum antibiotics reduced lethality and led to normalization of intestinal inflammation, proinflammatory cytokines, altered mucosal integrity, and reduced expression of the NLRP3 inflammasome. Overall, these findings support our conclusion that the biotin transport pathway plays an important role in the maintenance of intestinal homeostasis, and that NF-κB and the NLRP3 inflammasome, as well as gut microbiota, drive the development of intestinal inflammation when SMVT is absent.NEW & NOTEWORTHY This study demonstrates that deletion of the intestinal biotin uptake system in adult mice leads to the development of spontaneous gut inflammation and that luminal microbiota plays a role in its development.

Complex N-glycan breakdown by gut Bacteroides involves an extensive enzymatic apparatus encoded by multiple co-regulated genetic loci

Glycans are the major carbon sources available to the human colonic microbiota. Numerous N-glycosylated proteins are found in the human gut, from both dietary and host sources, including immunoglobulins such as IgA that are secreted into the intestine at high levels. Here, we show that many mutualistic gut Bacteroides spp. have the capacity to utilize complex N-glycans (CNGs) as nutrients, including those from immunoglobulins. Detailed mechanistic studies using transcriptomic, biochemical, structural and genetic techniques reveal the pathway employed by Bacteroides thetaiotaomicron (Bt) for CNG degradation. The breakdown process involves an extensive enzymatic apparatus encoded by multiple non-adjacent loci and comprises 19 different carbohydrate-active enzymes from different families, including a CNG-specific endo-glycosidase activity. Furthermore, CNG degradation involves the activity of carbohydrate-active enzymes that have previously been implicated in the degradation of other classes of glycan. This complex and diverse apparatus provides Bt with the capacity to access the myriad different structural variants of CNGs likely to be found in the intestinal niche.

Fecal short-chain fatty acid concentrations and dysbiosis in dogs with chronic enteropathy

Background

Accumulating evidence shows an important relationship between the gastrointestinal (GI) microbiota and host health. Microbial metabolites are believed to play a critical role in host‐microbial interactions. Short‐chain fatty acids (SCFAs) are major end products of bacterial carbohydrate fermentation in the intestinal tract. Decreased concentrations of SCFAs have been observed in humans with GI disease. However, large‐scale clinical data in dogs are lacking.

Hypothesis/Objective

To evaluate fecal concentrations of SCFAs and the fecal microbiota in healthy control (HC) dogs and dogs with chronic enteropathy (CE).

Animals

Forty‐nine privately owned HC dogs and 73 dogs with CE.

Methods

Prospective cohort study. Fecal concentrations of SCFAs were measured using gas chromatography/mass spectrometry. Illumina sequencing and quantitative real‐time polymerase chain reaction were utilized to evaluate the fecal microbiota.

Results

Fecal concentrations (median [range] μmol/g of dry matter) of acetate were lower (P = .03) in dogs with CE (185.8 [20.1‐1042.1]) than in HC dogs (224.0 [87.7‐672.8]). Propionate were also lower (P < .001) in dogs with CE (46.4 [0.4‐227.9]) than in HC dogs (105.9 [1.6‐266.9]). Moreover, total SCFAs were lower (P = .005) in dogs with CE (268.1 [21.8‐1378.2]) than in HC dogs (377.2 [126.6‐927.0]). Dysbiosis in dogs with CE was characterized by decreased bacterial diversity and richness, distinct microbial community clustering compared with that in HC dogs, and a higher dysbiosis index.

Conclusions and Clinical Importance

Dogs with CE had an altered fecal SCFA concentration accompanied by significant changes of the fecal microbiota.

A surface-exposed GH26 β-mannanase from Bacteroides ovatus: Structure, role, and phylogenetic analysis of BoMan26B

The galactomannan utilization locus (BoManPUL) of the human gut bacterium Bacteroides ovatus encodes BoMan26B, a cell-surface–exposed endomannanase whose functional and structural features have been unclear. Our study now places BoMan26B in context with related enzymes and reveals the structural basis for its specificity. BoMan26B prefers longer substrates and is less restricted by galactose side-groups than the mannanase BoMan26A of the same locus. Using galactomannan, BoMan26B generated a mixture of (galactosyl) manno-oligosaccharides shorter than mannohexaose. Three defined manno-oligosaccharides had affinity for the SusD-like surface–exposed glycan-binding protein, predicted to be implicated in saccharide transport. Co-incubation of BoMan26B and the periplasmic α-galactosidase BoGal36A increased the rate of galactose release by about 10-fold compared with the rate without BoMan26B. The results suggested that BoMan26B performs the initial attack on galactomannan, generating oligosaccharides that after transport to the periplasm are processed by BoGal36A. A crystal structure of BoMan26B with galactosyl-mannotetraose bound in subsites −5 to −2 revealed an open and long active-site cleft with Trp-112 in subsite −5 concluded to be involved in mannosyl interaction. Moreover, Lys-149 in the −4 subsite interacted with the galactosyl side-group of the ligand. A phylogenetic tree consisting of GH26 enzymes revealed four strictly conserved GH26 residues and disclosed that BoMan26A and BoMan26B reside on two distinct phylogenetic branches (A and B). The three other branches contain lichenases, xylanases, or enzymes with unknown activities. Lys-149 is conserved in a narrow part of branch B, and Trp-112 is conserved in a wider group within branch B.

Role of SCFAs in gut microbiome and glycolysis for colorectal cancer therapy

Increased risk of colorectal cancer (CRC) is associated with altered intestinal microbiota as well as short-chain fatty acids (SCFAs) reduction of output The energy source of colon cells relies mainly on three SCFAs, namely butyrate (BT), propionate, and acetate, while CRC transformed cells rely mainly on aerobic glycolysis to provide energy. This review summarizes recent research results for dysregulated glucose metabolism of SCFAs, which could be initiated by gut microbiome of CRC. Moreover, the relationship between SCFA transporters and glycolysis, which may correlate with the initiation and progression of CRC, are also discussed. Additionally, this review explores the linkage of BT to transport of SCFAs expressions between normal and cancerous colonocyte cell growth for tumorigenesis inhibition in CRC. Furthermore, the link between gut microbiota and SCFAs in the metabolism of CRC, in addition, the proteins and genes related to SCFAs-mediated signaling pathways, coupled with their correlation with the initiation and progression of CRC are also discussed. Therefore, targeting the SCFA transporters to regulate lactate generation and export of BT, as well as applying SCFAs or gut microbiota and natural compounds for chemoprevention may be clinically useful for CRCs treatment. Future research should focus on the combination these therapeutic agents with metabolic inhibitors to effectively target the tumor SCFAs and regulate the bacterial ecology for activation of potent anticancer effect, which may provide more effective application prospect for CRC therapy.

Dietary Fatty Acids Sustain the Growth of the Human Gut Microbiota

While a substantial amount of dietary fats escape absorption in the human small intestine and reach the colon, the ability of resident microbiota to utilize these dietary fats for growth has not been investigated in detail. In this study, we used an in vitro multivessel simulator system of the human colon to reveal that the human gut microbiota is able to utilize typically consumed dietary fatty acids to sustain growth. Gut microbiota adapted quickly to a macronutrient switch from a balanced Western diet-type medium to its variant lacking carbohydrates and proteins. We defined specific genera that increased in their abundances on the fats-only medium, including Alistipes, Bilophila, and several genera of the class Gammaproteobacteria In contrast, the abundances of well-known glycan and protein degraders, including Bacteroides, Clostridium, and Roseburia spp., were reduced under such conditions. The predicted prevalences of microbial genes coding for fatty acid degradation enzymes and anaerobic respiratory reductases were significantly increased in the fats-only environment, whereas the abundance of glycan degradation genes was diminished. These changes also resulted in lower microbial production of short-chain fatty acids and antioxidants. Our findings provide justification for the previously observed alterations in gut microbiota observed in human and animal studies of high-fat diets.IMPORTANCE Increased intake of fats in many developed countries has raised awareness of potentially harmful and beneficial effects of high fat consumption on human health. Some dietary fats escape digestion in the small intestine and reach the colon where they can be metabolized by gut microbiota. We show that human gut microbes are able to maintain a complex community when supplied with dietary fatty acids as the only nutrient and carbon sources. Such fatty acid-based growth leads to lower production of short-chain fatty acids and antioxidants by community members, which potentially have negative health consequences on the host.

The Effect of Microbiota on Colon Carcinogenesis

Although genetic background is known to contribute to colon carcinogenesis, the exact etiology of the disease remains elusive. The organ’s extensive interaction with microbes necessitated research on the role of microbiota on development of colon cancer. In this review, we summarized the defense mechanism of colon from foreign organism, and germ-free animal models that have been employed to elucidate microbial effect. We also comprehensively discussed the metabolic property of microbiota such as butyrate production, facilitation of heme toxicity, bile acid transformation, and nitrate reduction that has been shown to contribute to the development of the tumor. Finally, up-to-date subjects such as the effect of age and gender on microbiota are briefly discussed.

Switching to a fibre-rich and low-fat diet increases colonic folate contents among African Americans

How dietary patterns impact colonic bacterial biosynthesis of vitamins and utilization by humans is poorly understood. Our aim was to investigate whether a reciprocal dietary switch between rural South Africans (traditionally high fibre, low fat) and African Americans (Western diet of low fibre, high fat) affects colonic folate synthesis. Colonic evacuants were obtained from 20 rural South Africans and 20 African Americans consuming their usual diets at baseline. For 2 weeks thereafter, rural South Africans were provided with a Western diet (protein, 27%; fat, 52%; carbohydrate, 20%; and fibre, 8 g/day) and African Americans were provided with a high fibre, low-fat diet (protein, 16%; fat, 17%; carbohydrate, 63%; and fibre, 43 g/day). Colonic evacuants were again collected. No difference between groups at baseline in the folate content of 3-h evacuants was observed. The high-fibre, low-fat diet consumed by African Americans during the intervention produced a 41% increase in mean total folate content compared with baseline values (p = 0.0037). No change was observed in rural South Africans consuming a Western diet. Mean total folate content of colonic evacuants was higher among African Americans at the end of the dietary switch (3107 ± 1811 μg) compared with rural South Africans (2157 ± 1956 μg) (p = 0.0409). In conclusion, consistent with animal studies, switching from a Western diet to one higher in fibre and lower in fat can be expected to result in greater colonic folate content. Future research should confirm that these observations are not transitory and understand the contribution of transit-time to the findings.

Food, microbiome and colorectal cancer

You are what you eat. This adage has been confirmed by many studies demonstrating the high impact of nutrition on risk of cardiovascular diseases, many malignancies and other diseases. Dietary factors are of major relevance in the evolution of colorectal carcinoma. Various aspects are involved in colorectal carcinoma pathogenesis including genetics, lifestyle, age, chronic inflammation and others. It has only recently been recognized that the gut microbiota might reflect an important missing link in the interaction between diet and subsequent colorectal carcinoma development. Dietary factors are a major confounding factor affecting the composition of the intestinal microbiota. Several preclinical and clinical studies have recently suggested a role for the intestinal microbiota in potentially initiating and driving colorectal carcinoma. Therefore it is increasingly acknowledged that dietary factors might favor carcinogenesis via manipulation of the gut microbiota via potential outgrowth of certain bacterial populations, such as Fusobacterium nucleatum, Escherichia coli or Bacteroides fragilis. Excitingly, recent large clinical studies also highlighted a role for the gut microbiota and in particular Akkermansia muciniphila in tumor response toward chemotherapeutic agents and immune checkpoint inhibitors. This review will concentrate on the role of dietary factors in affecting the microbiota and implications in colorectal carcinoma.

Interindividual variability in gut microbiota and host response to dietary interventions

Dysbiosis is linked to human disease; therefore, gut microbiota modulation strategies provide an attractive means of correcting microbial imbalance to enhance human health. Because diet has a major influence on the composition, diversity, and metabolic capacity of the gut microbiota, numerous dietary intervention studies have been conducted to manipulate the gut microbiota to improve host outcomes and reduce disease risk. Emerging evidence suggests that interindividual variability in gut microbiota and host responsiveness exists, making it difficult to predict gut microbiota and host response to a given dietary intervention. This may, in turn, have implications on the consistency of results among studies and the perceived success or true efficacy of a dietary intervention in eliciting beneficial changes to the gut microbiota and human health.

The Need to Reassess Dietary Fiber Requirements in Healthy and Critically Ill Patients

This article provides evidence that current dietary fiber intake levels may be insufficient to maintain colonic mucosal health and defense, and reduce inflammation and cancer risk in otherwise healthy people. Current commercial tube feeds generally overlook the metabolic needs of the colon and may predispose patients to dysbiosis, bacterial overgrowth with pathogens such as Clostridium difficile, and acute colitis. These results raise concern about the wide-scale use of prophylactic antibiotics in the intensive care unit and the use of elemental, fiber-depleted tube feeds. Nutrition support is not complete without the addition of sufficient fiber to meet colonic nutritional needs.

Gut Microbiota: An Integral Moderator in Health and Disease

The gut microbiota, as the main member in gut microecology, is an essential mediator in health and disease. The gut microbiota interacts with various organs and systems in the body, including brain, lung, liver, bone, cardiovascular system, and others. Microbiota-derived metabolites such as the short chain fatty acid (SCFA) butyrate are primary signals, which link the gut microbiota and physiology. Recently, the gut microbiota has been identified as the origin of a number of diseases by influencing the related cell signaling pathways such as WNT/beta-catenin pathway in colorectal cancer and T cell receptor signaling in the central nervous system. Moreover, several microRNAs participate in signaling networks through the intervention of the gut microbiota. The interaction between the gut microbiota and miRNAs plays a crucial role in vascular dysfunction and hepatocellular carcinoma (HCC). In this review, we will report and discuss recent findings about the crosstalk between the gut microbiota and physical organs and how the gut microbiota and miRNAs regulate each other while influencing the host via genes, proteins, or metabolites.

Dietary Fiber Treatment Corrects the Composition of Gut Microbiota, Promotes SCFA Production, and Suppresses Colon Carcinogenesis

Epidemiological studies propose a protective role for dietary fiber in colon cancer (CRC). One possible mechanism of fiber is its fermentation property in the gut and ability to change microbiota composition and function. Here, we investigate the role of a dietary fiber mixture in polyposis and elucidate potential mechanisms using TS4Cre × cAPC^l°^x468 mice. Stool microbiota profiling was performed, while functional prediction was done using PICRUSt. Stool short-chain fatty acid (SCFA) metabolites were measured. Histone acetylation and expression of SCFA butyrate receptor were assessed. We found that SCFA-producing bacteria were lower in the polyposis mice, suggesting a decline in the fermentation product of dietary fibers with polyposis. Next, a high fiber diet was given to polyposis mice, which significantly increased SCFA-producing bacteria as well as SCFA levels. This was associated with an increase in SCFA butyrate receptor and a significant decrease in polyposis. In conclusion, we found polyposis to be associated with dysbiotic microbiota characterized by a decline in SCFA-producing bacteria, which was targetable by high fiber treatment, leading to an increase in SCFA levels and amelioration of polyposis. The prebiotic activity of fiber, promoting beneficial bacteria, could be the key mechanism for the protective effects of fiber on colon carcinogenesis. SCFA-promoting fermentable fibers are a promising dietary intervention to prevent CRC.

The Gut Microbiota and Ageing

Understanding how the human gut microbiota might influence ageing is challenging. The gut microbiota is a hugely complex ecology of organisms that varies greatly with individuals and time, making age-related changes difficult to measure. However, elderly and younger populations do show differences in gut microbe composition. The key question is whether these differences only reflect age-related changes in host physiology and diet, or if microbes can drive host ageing? Model organisms allow this question to be addressed. Longitudinal analyses in the fruit fly Drosophila melanogaster show that changes in microbial composition precedes intestinal and host ageing, and antibiotic treatment increases lifespan, implicating microbes in accelerating ageing. Antibiotics also extend the lifespan of middle-aged killifish but additional transplantation of gut microbes from young killifish extends lifespan further, suggesting a positive effect of microbes associated with young animals. Microbes from old, but not young, mice induce inflammation when added to germ-free mice suggesting that microbes become more harmful to the host with age. These studies implicate broad classes of bacteria, particularly members of the phylum Proteobacteria, as drivers of ageing in a feed-forward loop with intestinal degradation and inflammation. The nematode Caenorhabditis elegans can be associated with single strains of genetically-tractable bacteria, and this simplified system has revealed specific interventions in bacterial metabolism, such as inhibition of bacterial folate synthesis, that extend animal lifespan. Transferring this understanding to the human microbiota is challenging but promises to reveal how manipulation of the gut microbiota might be a route to maintain health in old age.

A Microbiomic Analysis in African Americans with Colonic Lesions Reveals Streptococcus sp.VT162 as a Marker of Neoplastic Transformation

Increasing evidence suggests a role of the gut microbiota in colorectal carcinogenesis (CRC). To detect bacterial markers of colorectal cancer in African Americans a metabolomic analysis was performed on fecal water extracts. DNA from stool samples of adenoma and healthy subjects and from colon cancer and matched normal tissues was analyzed to determine the microbiota composition (using 16S rDNA) and genomic content (metagenomics). Metagenomic functions with discriminative power between healthy and neoplastic specimens were established. Quantitative Polymerase Chain Reaction (q-PCR) using primers and probes specific to Streptococcus sp. VT_162 were used to validate this bacterium association with neoplastic transformation in stool samples from two independent cohorts of African Americans and Chinese patients with colorectal lesions. The metabolomic analysis of adenomas revealed low amino acids content. The microbiota in both cancer vs. normal tissues and adenoma vs. normal stool samples were different at the 16S rRNA gene level. Cross-mapping of metagenomic data led to 9 markers with significant discriminative power between normal and diseased specimens. These markers identified with Streptococcus sp. VT_162. Q-PCR data showed a statistically significant presence of this bacterium in advanced adenoma and cancer samples in an independent cohort of CRC patients. We defined metagenomic functions from Streptococcus sp. VT_162 with discriminative power among cancers vs. matched normal and adenomas vs. healthy subjects’ stools. Streptococcus sp. VT_162 specific 16S rDNA was validated in an independent cohort. These findings might facilitate non-invasive screening for colorectal cancer.

Diet, Gut Microbiota, and Colorectal Cancer Prevention: A Review of Potential Mechanisms and Promising Targets for Future Research

Diet plays an important role in the development of colorectal cancer. Emerging data have implicated the gut microbiota in colorectal cancer. Diet is a major determinant for the gut microbial structure and function. Therefore, it has been hypothesized that alterations in gut microbes and their metabolites may contribute to the influence of diet on the development of colorectal cancer. We review several major dietary factors that have been linked to gut microbiota and colorectal cancer, including major dietary patterns, fiber, red meat and sulfur, and obesity. Most of the epidemiologic evidence derives from cross-sectional or short-term, highly controlled feeding studies that are limited in size. Therefore, high-quality large-scale prospective studies with dietary data collected over the life course and comprehensive gut microbial composition and function assessed well prior to neoplastic occurrence are critically needed to identify microbiome-based interventions that may complement or optimize current diet-based strategies for colorectal cancer prevention and management.

Gut Microbiota, Inflammation, and Colorectal Cancer

Colorectal cancer is the second-leading cause of cancer-related deaths in the United States and fourth-leading cause of cancer-related deaths worldwide. While cancer is largely considered to be a disease of genetic and environmental factors, increasing evidence has demonstrated a role for the microbiota (the microorganisms associated with the human body) in shaping inflammatory environments and promoting tumor growth and spread. Herein, we discuss both human data from meta'omics analyses and data from mechanistic studies in cell culture and animal models that support specific bacterial agents as potentiators of tumorigenesis-including Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli. Further, we consider how microbes can be used in diagnosing colorectal cancer and manipulating the tumor environment to encourage better patient outcomes in response to immunotherapy treatments.

(Dis)Trust your gut: the gut microbiome in age-related inflammation, health, and disease

Chronic inflammation represents one of the most consistent biologic features of aging. However, the precise etiology of persistent low-grade increases in inflammation remains unclear. Recent evidence suggests that the gut microbiome may play a key role in age-related inflammation. Indeed, several studies have indicated that older adults display an altered composition of the gut microbiota, and early evidence indicates that this dysbiosis is associated with the presence of several key circulating inflammatory analytes. The present review summarizes knowledge on age-related inflammation and discusses how potential relationships with gut dysbiosis may lead to novel treatment strategies in the future."The pattern of disease is an expression of the response of man to his total environment (physical, biological, and social); this response is, therefore, determined by anything that affects man himself or his environment." - Rene Dubos, 1961.

The shifting epidemiology of colorectal cancer in sub-Saharan Africa

The perception that colorectal cancer is rare in sub-Saharan Africa is widely held; however, it is unclear whether this is due to poor epidemiological data or to lower disease rates. The quality of epidemiological data has somewhat improved, and there is an ongoing transition to western dietary and lifestyle practices associated with colorectal cancer. The impact of these changes on the incidence of colorectal cancer is not as evident as it is with other non-communicable diseases such as diabetes. In this Viewpoint, we discuss the epidemiology of colorectal cancer in sub-Saharan Africa. Colorectal cancer in this region frequently occurs at an early age, often with distinctive histological characteristics. We detail the crucial need for hypothesis-driven research on the risk factors for colorectal cancer in this population and identify key research gaps. Should colorectal cancer occur more frequently than assumed, then commensurate allocation of resources will be needed for diagnosis and treatment.

A metagenomic study of the preventive effect of Lactobacillus rhamnosus GG on intestinal polyp formation in ApcMin/+ mice

AIMS

To investigate the in vivo effects of Lactobacillus rhamnosus GG (LGG) on intestinal polyp development and the interaction between this single-organism probiotic and the gut microbiota therein.

METHODS AND RESULTS

The Apc^Min/+ mouse model was used to study the potential preventive effect of LGG on intestinal polyposis, while shotgun metagenomic sequencing was employed to characterize both taxonomic and functional changes within the gut microbial community. We found that the progression of intestinal polyps in the control group altered the community functional profile remarkably despite small variation in the taxonomic diversity. In comparison, the consumption of LGG helped maintain the overall functional potential and taxonomic profile in the resident microbes, thereby leading to a 25% decrease of total polyp counts. Furthermore, we found that LGG enriched those microbes or microbial activities related to short-chain fatty acid production (e.g. Roseburia and Coprococcus), as well as suppressed the ones that can lead to inflammation (e.g. Bilophila wadsworthia).

CONCLUSIONS

Our study using shotgun metagenomics highlights how single probiotic LGG may exert its beneficial effects and decrease polyp formation in mice by maintaining gut microbial functionality.

SIGNIFICANCE AND IMPACT OF THE STUDY

This probiotic intervention targeting microbiota may be used in conjugation with other dietary supplements or drugs as part of prevention strategies for early-stage colon cancer, after further clinical validations in human.

Lipopolysaccharide inhibits colonic biotin uptake via interference with membrane expression of its transporter: a role for a casein kinase 2-mediated pathway

Biotin (vitamin B7), an essential micronutrient for normal cellular functions, is obtained from both dietary sources as well as gut microbiota. Absorption of biotin in both the small and large intestine is via a carrier-mediated process that involves the sodium-dependent multivitamin transporter (SMVT). Although different physiological and molecular aspects of intestinal biotin uptake have been delineated, nothing is known about the effect of LPS on the process. We addressed this issue using in vitro (human colonic epithelial NCM460 cells) and in vivo (mice) models of LPS exposure. Treating NCM460 cells with LPS was found to lead to a significant inhibition in carrier-mediated biotin uptake. Similarly, administration of LPS to mice led to a significant inhibition in biotin uptake by native colonic tissue. Although no changes in total cellular SMVT protein and mRNA levels were observed, LPS caused a decrease in the fraction of SMVT expressed at the cell surface. A role for casein kinase 2 (CK2) (whose activity was also inhibited by LPS) in mediating the endotoxin effects on biotin uptake and on membrane expression of SMVT was suggested by findings that specific inhibitors of CK2, as well as mutating the putative CK2 phosphorylation site (Thr⁷⁸Ala) in the SMVT protein, led to inhibition in biotin uptake and membrane expression of SMVT. This study shows for the first time that LPS inhibits colonic biotin uptake via decreasing membrane expression of its transporter and that these effects likely involve a CK2-mediated pathway.