Gut microbial metabolites limit the frequency of autoimmune T cells and protect against type 1 diabetes.

Gut dysbiosis might underlie the pathogenesis of type 1 diabetes. In mice of the non-obese diabetic (NOD) strain, we found that key features of disease correlated inversely with blood and fecal concentrations of the microbial metabolites acetate and butyrate. We therefore fed NOD mice specialized diets designed to release large amounts of acetate or butyrate after bacterial fermentation in the colon. Each diet provided a high degree of protection from diabetes, even when administered after breakdown of immunotolerance. Feeding mice a combined acetate- and butyrate-yielding diet provided complete protection, which suggested that acetate and butyrate might operate through distinct mechanisms. Acetate markedly decreased the frequency of autoreactive T cells in lymphoid tissues, through effects on B cells and their ability to expand populations of autoreactive T cells. A diet containing butyrate boosted the number and function of regulatory T cells, whereas acetate- and butyrate-yielding diets enhanced gut integrity and decreased serum concentration of diabetogenic cytokines such as IL-21. Medicinal foods or metabolites might represent an effective and natural approach for countering the numerous immunological defects that contribute to T cell-dependent autoimmune diseases.

Erratum: Gut microbial metabolites limit the frequency of autoimmune T cells and protect against type 1 diabetes.

This corrects the article DOI: 10.1038/ni.3713.

Real-world effectiveness of systemic anticancer therapy for advanced melanoma in the west of Scotland from 2010 to 2018.

Aim: Assess the real-world effectiveness of systemic anticancer therapy in advanced (unresectable or metastatic) melanoma. Methods: This was a retrospective cohort study linking routine healthcare data with systemic anticancer therapy prescriptions for patients starting immunotherapy or targeted treatments between 1 November 2010 and 31 December 2017 in the west of Scotland. Results: Among 362 patients identified, median overall survival varied between 18.5 months (95% CI: 14.4-not estimable) for ipilimumab/nivolumab combination and 5.6 months (95% CI: 4.5-7.3) for dabrafenib, but there were differences in the characteristics of each regimen cohort. Raised lactate dehydrogenase levels and Eastern Cooperative Oncology Group performance status ≥2 negatively impacted overall survival. Conclusion: The patients had a shorter median overall survival than those in pivotal trials. This was expected, given that this real-world cohort included patients with poorer prognostic indicators, typically excluded from trials.

What matters to patients and clinicians when discussing the impact of cancer medicines on health-related quality of life? Consensus-based mixed methods approach in prostate cancer.

OBJECTIVE: To identify what matters to clinicians and patients when discussing cancer medicines' impact on health-related quality of life (HRQoL). METHODS: A framework of HRQoL domain/domain elements was developed, informed by analysis of published patient reported outcome measures (PROMs), applicable to prostate cancer. Using mixed methods (eDelphi, Nominal Group Technique and questionnaire), prostate cancer clinicians and patients attending prostate cancer clinics and support groups were asked which domains/domain elements would be important to them when discussing the impact prostate cancer medicines have on their HRQoL. RESULTS: Twenty-one clinicians and 71 patients participated from the West of Scotland. Clinicians and patients identified 53/62 domain elements across seven domains as important, of which 32 (60%) were common to both groups. Clinicians placed more importance than patients on Mood & Emotion; in contrast, patients placed importance on a broader range of Symptoms & Side Effects, being informed about their care, and having effective healthcare professional collaboration. CONCLUSION: This study provides insight into the similarities and differences between what clinicians and patients think is important when discussing the impact of cancer medicines on HRQoL. Future research should involve exploring the potential for consistency of medicines PROMs across different cancer types to support patient-clinician communication and drive improvements in care.

Use of record linkage to evaluate treatment outcomes and trial eligibility in a real-world metastatic prostate cancer population in Scotland.

PURPOSE: New treatments are introduced into standard care based on clinical trial results. However, it is not clear if these benefits are reflected in the broader population. This study analysed the clinical outcomes of patients with metastatic castration-resistant prostate cancer, treated with abiraterone and enzalutamide, within the Scottish National Health Service. METHODS: Retrospective cohort study using record linkage of routinely collected healthcare data (study period: February 2012 to February 2017). Overall survival (OS) was analysed using Kaplan-Meier methods and Cox Proportional Hazard models; a subgroup analysis comprised potentially trial-eligible patients. RESULTS: Overall, 271 patients were included and 73.8% died during the study period. Median OS was poorer than in the pivotal trials, regardless of medication and indication: 10.8 months (95% confidence interval [CI] 8.6-15.1) and 20.9 months (95% CI 14.9-29.0) for abiraterone, and 12.6 months (95% CI 10.5-18.2) and 16.0 months (95% CI 9.8-not reached) for enzalutamide, post and pre chemotherapy, respectively. Only 46% of patients were potentially "trial eligible" and in this subgroup OS improved. Factors influencing survival included baseline performance status, and baseline prostate-specific antigen, alkaline phosphatase, and albumin levels. CONCLUSIONS: Poorer prognostic features of non-trial eligible patients impact real-world outcomes of cancer medicines. Electronic record linkage of routinely collected healthcare data offers an opportunity to report outcomes on cancer medicines at scale and describe population demographics. The availability of such observational data to supplement clinical trial results enables patients and clinicians to make more informed treatment decisions, and policymakers to contextualise trial findings.

Consensus workshops on the development of an ADHD medication management protocol using QbTest: developing a clinical trial protocol with multidisciplinary stakeholders.

BACKGROUND: The study design and protocol that underpin a randomised controlled trial (RCT) are critical for the ultimate success of the trial. Although RCTs are considered the gold standard for research, there are multiple threats to their validity such as participant recruitment and retention, identifying a meaningful change, and non-adherence to the protocol. For clinical RCTs, involving patients and clinicians in protocol design provides the opportunity to develop research protocols that are meaningful to their target audience and may help overcome some of the inherent threats in conducting RCTs. However, the majority of protocols do not describe the methodology underpinning their development, limiting the amount of learned experience shared between research groups. METHOD: With the purpose of reporting a collaborative approach towards developing a protocol, we present the findings from three sequential workshops that were conducted with the aim of developing a protocol to investigate the feasibility of adding a computerised test of attention, impulsivity and activity (QbTest) to medication management of children and young people with Attention deficit hyperactivity disorder (ADHD). Based on previous qualitative interviews with clinicians and families, each workshop prioritised topics for focused discussion. Information from the workshops was fed back to the participants for reflection in advance of the next workshop. RESULTS: The workshops involved 21 multi-disciplinary ADHD experts, including clinicians, patient and public involvement (PPI) members, parents of young people with ADHD and researchers. The consensus workshops addressed key research issues such as: the most relevant outcome measures/ resource drivers; methods and time points for data collection; and the clinical protocol for utilising the QbTest, including when best to use this within the medication management process. The resulting protocol details a feasibility RCT design describing these factors. CONCLUSION: Protocols which are co-developed may help overcome some of the risks associated with RCT completion (e.g. recruitment, retention, protocol adherence) and help prioritise outcomes of greater relevance to the populations under study. The methodology has potential value for researchers and organisations developing clinical guidelines, and offers insights into the valuable impact of PPI upon trial design. TRIAL REGISTRATION: Clinicaltrials.gov NCT03368573, 11th December 2017 (retrospectively registered).

Commensal microbe-derived butyrate induces the differentiation of colonic regulatory T cells.

Gut commensal microbes shape the mucosal immune system by regulating the differentiation and expansion of several types of T cell. Clostridia, a dominant class of commensal microbe, can induce colonic regulatory T (Treg) cells, which have a central role in the suppression of inflammatory and allergic responses. However, the molecular mechanisms by which commensal microbes induce colonic Treg cells have been unclear. Here we show that a large bowel microbial fermentation product, butyrate, induces the differentiation of colonic Treg cells in mice. A comparative NMR-based metabolome analysis suggests that the luminal concentrations of short-chain fatty acids positively correlates with the number of Treg cells in the colon. Among short-chain fatty acids, butyrate induced the differentiation of Treg cells in vitro and in vivo, and ameliorated the development of colitis induced by adoptive transfer of CD4(+) CD45RB(hi) T cells in Rag1(-/-) mice. Treatment of naive T cells under the Treg-cell-polarizing conditions with butyrate enhanced histone H3 acetylation in the promoter and conserved non-coding sequence regions of the Foxp3 locus, suggesting a possible mechanism for how microbial-derived butyrate regulates the differentiation of Treg cells. Our findings provide new insight into the mechanisms by which host-microbe interactions establish immunological homeostasis in the gut.

Bifidobacteria can protect from enteropathogenic infection through production of acetate.

The human gut is colonized with a wide variety of microorganisms, including species, such as those belonging to the bacterial genus Bifidobacterium, that have beneficial effects on human physiology and pathology. Among the most distinctive benefits of bifidobacteria are modulation of host defence responses and protection against infectious diseases. Nevertheless, the molecular mechanisms underlying these effects have barely been elucidated. To investigate these mechanisms, we used mice associated with certain bifidobacterial strains and a simplified model of lethal infection with enterohaemorrhagic Escherichia coli O157:H7, together with an integrated 'omics' approach. Here we show that genes encoding an ATP-binding-cassette-type carbohydrate transporter present in certain bifidobacteria contribute to protecting mice against death induced by E. coli O157:H7. We found that this effect can be attributed, at least in part, to increased production of acetate and that translocation of the E. coli O157:H7 Shiga toxin from the gut lumen to the blood was inhibited. We propose that acetate produced by protective bifidobacteria improves intestinal defence mediated by epithelial cells and thereby protects the host against lethal infection.

Housing experimental rats in solid-based cages with digestible bedding may confound outcomes of nutritional studies.

BACKGROUND: Rats used in nutritional studies are often kept in wire-based cages to prevent ingestion of bedding and minimise ingestion of faeces. However, wire-based cages are criticised because of potential negative animal welfare implications. This study investigated the effects of wire and solid-based cages with corncob bedding on large bowel fermentation and microbiota. Rats were group housed in wire or solid-based cages and fed either a low-fibre (LF) diet or a high-fibre (HF) diet composed of resistant starch for 4 weeks. RESULTS: Bedding material was observed in faeces of rats housed in solid-based cages. Caging type and diet altered large bowel fermentation variables and bacterial populations. Caecal digesta weight was lower in rats fed HF diet and maintained on bedding than in HF-fed rats maintained on wire. Bacteria abundance associated with fibre fermentation was higher in LF-diet fed rats maintained on bedding compared with LF-fed rats housed on wire. CONCLUSION: Maintaining rats in solid-based cages with corncob bedding alters large bowel fermentation and bacterial communities owing to ingestion of bedding. These changes may confound outcomes of nutritional studies, particularly those investigating the health effects of fibres. The use of wire-based caging may be justified in research of this type.

Butyrylated starch increases colonic butyrate concentration but has limited effects on immunity in healthy physically active individuals.

BACKGROUND: Butyrate delivery to the large bowel may positively modulate commensal microbiota and enhance immunity. OBJECTIVE: To determine the effects of increasing large bowel butyrate concentration through ingestion of butyrylated high amylose maize starch (HAMSB) on faecal biochemistry and microbiota, and markers of immunity in healthy active individuals. DESIGN: Male and female volunteers were assigned randomly to consume either two doses of 20 g HAMSB (n = 23; age 37.9 +/- 7.8 y; mean +/- SD) or a low amylose maize starch (LAMS) (n = 18; age 36.9 = 9.5 y) twice daily for 28 days. Samples were collected on days 0, 10 and 28 for assessment of faecal bacterial groups, faecal biochemistry, serum cytokines and salivary antimicrobial proteins. RESULTS: HAMSB led to relative increases in faecal free (45%; 12-86%; mean; 90% confidence interval; P = 0.02), bound (950%; 563-1564%; P < 0.01) and total butyrate (260%; 174-373%; P < 0.01) and faecal propionate (41%; 12-77%; P = 0.02) from day 0 to day 28 compared to LAMS. HAMSB was also associated with a relative 1.6-fold (1.2- to 2.0-fold; P < 0.01) and 2.5-fold (1.4- to 4.4-fold; P = 0.01) increase in plasma IL-10 and TNF-alpha but did not alter other indices of immunity. There were relative greater increases in faecal P. distasonis (81-fold (28- to 237-fold; P < 0.01) and F. prausnitzii (5.1-fold (2.1- to 12-fold; P < 0.01) in the HAMSB group. CONCLUSIONS: HAMSB supplementation in healthy active individuals promotes the growth of bacteria that may improve bowel health and has only limited effects on plasma cytokines.

Genomic homeostasis is dysregulated in favour of apoptosis in the colonic epithelium of the azoxymethane treated rat.

BACKGROUND: The acute response to genotoxic carcinogens in rats is an important model for researching cancer initiation events. In this report we define the normal rat colonic epithelium by describing transcriptional events along the anterior-posterior axis and then investigate the acute effects of azoxymethane (AOM) on gene expression, with a particular emphasis on pathways associated with the maintenance of genomic integrity in the proximal and distal compartments using whole genome expression microarrays. RESULTS: There are large transcriptional changes that occur in epithelial gene expression along the anterior-posterior axis of the normal healthy rat colon. AOM administration superimposes substantial changes on these basal gene expression patterns in both the distal and proximal rat colonic epithelium. In particular, the pathways associated with cell cycle and DNA damage and repair processes appear to be disrupted in favour of apoptosis. CONCLUSIONS: The healthy rats' colon exhibits extensive gene expression changes between its proximal and distal ends. The most common changes are associated with metabolism, but more subtle expression changes in genes involved in genomic homeostasis are also evident. These latter changes presumably protect and maintain a healthy colonic epithelium against incidental dietary and environmental insults. AOM induces substantial changes in gene expression, resulting in an early switch in the cell cycle process, involving p53 signalling, towards cell cycle arrest leading to the more effective process of apoptosis to counteract this genotoxic insult.

Can butyrate prevent colon cancer? The AusFAP study: A randomised, crossover clinical trial.

Increased colonic butyrate from microbial fermentation of fibre may protect from colorectal cancer (CRC). Dietary butyrylated high amylose maize starch (HAMSB) delivers butyrate to the large bowel. The objective of this clinical trial (AusFAP) is to evaluate potential chemoprotective effects of HAMSB on polyposis in individuals with a genetic form of colon cancer, Familial Adenomatous Polyposis (FAP). The study is a multi-site, double blind, randomised, placebo-controlled crossover trial undertaken at major hospitals in Australia. After a baseline endoscopy participants consume either 40g/day of HAMSB or placebo (low amylose maize) starch for 26 weeks. After another endoscopic examination participants consume the alternate starch for 26 weeks. A third endoscopy at 52 weeks is followed by 26 weeks' washout and a final endoscopy at 78 weeks. Primary outcome measure is the global large bowel polyp number. Secondary measures include global polyp size counts, and number and size of polyps at two tattoo sites: one cleared of polyps at baseline, and another safely chosen with polyps left in situ during the study. Other secondary outcome measures include the effects of intervention on cellular proliferation in colonic biopsies, faecal measures including short chain fatty acid concentrations, and participants' dietary intakes. Generalized linear mixed models analysis will be used to estimate differences in primary outcomes between intervention and placebo periods. This study represents the first clinical evaluation of the effects of increased colonic butyrate on polyp burden in FAP which, if effective, may translate to lower risk of sporadic CRC in the community. Australian New Zealand Clinical Trials Registry Number: 12612000804886.

Involving Patients and Clinicians in the Design of Wireframes for Cancer Medicines Electronic Patient Reported Outcome Measures in Clinical Care: Mixed Methods Study.

BACKGROUND: Cancer treatment is a key component of health care systems, and the increasing number of cancer medicines is expanding the treatment landscape. However, evidence of the impact on patients has been focused more on chemotherapy toxicity and symptom control and less on the effect of cancer medicines more broadly on patients' lives. Evolving electronic patient-reported outcome measures (ePROMs) presents the opportunity to secure early engagement of patients and clinicians in shaping the collection of quality-of-life metrics and presenting these data to better support the patient-clinician decision-making process. OBJECTIVE: The aim of this study was to obtain initial feedback from patients and clinicians on the wireframes of a digital solution (patient app and clinician dashboard) for the collection and use of cancer medicines ePROMs. METHODS: We adopted a 2-stage, mixed methods approach. Stage 1 (March to June 2019) consisted of interviews and focus groups with cancer clinicians and patients with cancer to explore the face validity of the wireframes, informed by the technology acceptance model constructs (perceived ease of use, perceived usefulness, and behavioral intention to use). In stage 2 (October 2019 to February 2020), the revised wireframes were assessed through web-based, adapted technology acceptance model questionnaires. Qualitative data (stage 1) underwent a framework analysis, and descriptive statistics were performed on quantitative data (stage 2). Clinicians and patients with cancer were recruited from NHS Greater Glasgow & Clyde, the largest health board in Scotland. RESULTS: A total of 14 clinicians and 19 patients participated in a combination of stage 1 interviews and focus groups. Clinicians and patients indicated that the wireframes of a patient app and clinician dashboard for the collection of cancer medicines ePROMs would be easy to use and could focus discussions, and they would be receptive to using such tools in the future. In stage 1, clinicians raised the potential impact on workload, and both groups identified the need for adequate IT skills to use each technology. Changes to the wireframes were made, and in stage 2, clinicians (n=8) and patients (n=16) indicated it was "quite likely" that the technologies would be easy to use and they would be "quite likely" to use them in the future. Notably, clinicians indicated that they would use the dashboard to enable treatment decisions "with around half" of their patients. CONCLUSIONS: This study emphasizes the importance of consulting both patients and clinicians in the design of digital solutions. The wireframes were perceived positively by patients and clinicians who were willing to use such technologies if available in the future as part of routine care. However, challenges were raised, and some differences were identified between participant groups, which warrant further research.

Butyrate delivered by butyrylated starch increases distal colonic epithelial apoptosis in carcinogen-treated rats.

Animal studies show that increasing large bowel butyrate concentration through ingestion of butyrylated or resistant starches opposes carcinogen-induced tumorigenesis, which is consistent with population data linking greater fiber consumption with lowered colorectal cancer (CRC) risk. Butyrate has been shown to regulate the apoptotic response to DNA damage. This study examined the impact of increasing large bowel butyrate concentration by dietary butyrylated starch on the colonic epithelium of rats treated with the genotoxic carcinogen azoxymethane (AOM). Four groups of 10 male rats were fed AIN-93G based-diets containing either low amylose maize starch (LAMS), LAMS with 3% tributyrin, 10% high amylose maize starch (HAMS) or 10% butyrylated HAMS (HAMSB). HAMS and HAMSB starches were cooked by heating in water. After 4 weeks, rats were injected once with AOM and killed 6 h later. Rates of apoptosis and proliferation were measured in colonic epithelium. Short-chain fatty acid concentrations in large bowel digesta and hepatic portal venous plasma were higher in HAMSB than all other groups. Apoptotic rates in the distal colon were increased by HAMSB and correlated with luminal butyrate concentrations but cellular proliferation rates were unaffected by diet. The increase in apoptosis was most marked in the base and proliferative zone of the crypt. Regulation of luminal butyrate using HAMSB increases the rates of apoptotic deletion of DNA-damaged colonocytes. We propose this pro-apoptotic function of butyrate plays a major role reducing tumour formation in the AOM-treated rat and that these data support a potential protective role of butyrate in CRC.

Resistant starches protect against colonic DNA damage and alter microbiota and gene expression in rats fed a Western diet.

Resistant starch (RS), fed as high amylose maize starch (HAMS) or butyrylated HAMS (HAMSB), opposes dietary protein-induced colonocyte DNA damage in rats. In this study, rats were fed Western-type diets moderate in fat (19%) and protein (20%) containing digestible starches [low amylose maize starch (LAMS) or low amylose whole wheat (LAW)] or RS [HAMS, HAMSB, or a whole high amylose wheat (HAW) generated by RNA interference] for 11 wk (n = 10/group). A control diet included 7% fat, 13% protein, and LAMS. Colonocyte DNA single-strand breaks (SSB) were significantly higher (by 70%) in rats fed the Western diet containing LAMS relative to controls. Dietary HAW, HAMS, and HAMSB opposed this effect while raising digesta levels of SCFA and lowering ammonia and phenol levels. SSB correlated inversely with total large bowel SCFA, including colonic butyrate concentration (R(2) = 0.40; P = 0.009), and positively with colonic ammonia concentration (R(2) = 0.40; P = 0.014). Analysis of gut microbiota populations using a phylogenetic microarray revealed profiles that fell into 3 distinct groups: control and LAMS; HAMS and HAMSB; and LAW and HAW. The expression of colonic genes associated with the maintenance of genomic integrity (notably Mdm2, Top1, Msh3, Ung, Rere, Cebpa, Gmnn, and Parg) was altered and varied with RS source. HAW is as effective as HAMS and HAMSB in opposing diet-induced colonic DNA damage in rats, but their effects on the large bowel microbiota and colonocyte gene expression differ, possibly due to the presence of other fiber components in HAW.

Healthcare Costs for Metastatic Castration-Resistant Prostate Cancer Patients Treated with Abiraterone or Enzalutamide.

OBJECTIVE: The aim was to assess the real-world healthcare resource use and direct medical costs for metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone or enzalutamide, in whom chemotherapy is not yet indicated (pre-chemotherapy) or who had previously received docetaxel-based chemotherapy (post-chemotherapy), before commencing these medicines. METHODS: A retrospective cost analysis of mCRPC patients who commenced abiraterone or enzalutamide between 2012 and 2015 was conducted. Routinely collected datasets from the largest health board in Scotland and the UK, Greater Glasgow and Clyde, were linked. They contained information on patient demographics, diagnosis, outpatient consultations, hospital admissions, treatments (abiraterone and enzalutamide), and supportive medicines. Unit costs were obtained from the Scottish Health Service Costs, Personal Social Services Research Unit, and British National Formulary. Generalised linear model-based regression was used to estimate total mean direct costs, and two-part models were used to estimate separate cost components. All models were adjusted for propensity score and key variables. Sensitivity analysis was conducted to explore the impact of hypothetical patient access scheme discounts. RESULTS: Estimated total mean direct medical costs of treating mCRPC patients were similar, albeit with wide and overlapping confidence intervals. Across both treatments, patients who received abiraterone or enzalutamide in a pre-chemotherapy setting incurred the highest total mean direct medical costs. However, post-chemotherapy patients were associated with higher outpatient clinic visits, inpatient hospital admissions, and supportive medicines. Regarding relative contribution to the total mean direct medical cost, the treatment costs were the main contributor, followed by inpatient admissions, outpatient clinic visits, and supportive medicines. CONCLUSION: The total mean direct medical costs were similar for abiraterone and enzalutamide patients. The costs were not driven by the choice of treatment regimen, but treatment setting (pre-chemotherapy or post-chemotherapy indications) and related healthcare resource utilisation. Future studies should focus on economic evaluations, such as cost-effectiveness analyses, using real-world data.

Opportunities and challenges when using record linkage of routinely collected electronic health care data to evaluate outcomes of systemic anti-cancer treatment in clinical practice.

The efficacy and safety of cancer medicines as reported from randomised clinical trials do not always translate into similar benefits in routine clinical practice; hence, post-marketing studies are a useful addition to the evidence base. With recent advances in digital infrastructure and the advent of electronically available health records, linkage of routinely collected data has emerged as a promising evaluation method for these studies. This paper discusses the opportunities and challenges when applying an electronic record linkage methodology with respect to systemic anti-cancer therapy by showcasing exemplar studies conducted over a three-year period in Scotland, and highlights some of the potential pitfalls spanning the entire breadth and depth of the research process. Our experiences as an interdisciplinary team indicate that there is scope to conduct large cohort studies to generate results from routine clinical practice within a reasonable time frame; however, close collaboration between researchers, data controllers and clinicians is required in order to obtain valid and meaningful results.

Dietary resistant and butyrylated starches have different effects on the faecal bacterial flora of azoxymethane-treated rats.

Epidemiological studies have suggested that dietary fibre lowers the risk of colorectal cancer, which may be due to increased butyrate production from colonic fermentation of a type of fibre, resistant starch (RS). The present study investigated the effects of dietary RS and butyrylated RS on the faecal microbiota of rats treated with azoxymethane. A total of four groups of nine rats were fed diets containing either standard maize starch (low-amylose maize starch (LAMS), low RS), LAMS with 3 % tributyrin (LAMST), cooked 10 % high-amylose maize starch (HAMS, high RS) or cooked 10 % butyrylated HAMS (HAMSB). Faecal samples were examined by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments. Multivariate analysis demonstrated no differences between faecal microbiota before treatment but revealed differences in DGGE patterns between diet groups, with the exception of the two low-RS groups (LAMS and LAMST). Subsequent analysis identified eleven DGGE bands contributing significantly to the differentiation between diets. These phylotypes belonged to Clostridiales (five), Lactobacillus (one) and Bacteroidetes (five) lineages. Rats fed HAMS had increased concentration of propionate in their distal colonic digesta and developed faecal populations containing Ruminococcus bromii-like bacteria. HAMSB increased propionate and butyrate concentrations in distal colonic digesta and was associated with the appearance of two non-butyrate-producing bacteria, Lactobacillus gasseri and Parabacteroides distasonis. In conclusion, supplementation with specific dietary RS leads to changes in faecal microbiota profiles that may be associated with improved bowel health.

Is the tissue persistence of O(6)-methyl-2'-deoxyguanosine an indicator of tumour formation in the gastrointestinal tract?

Azoxymethane (AOM) is a methylating agent capable of inducing mutations in DNA by forming adducts with DNA bases. It has been used to understand the mechanisms involved in colon carcinogenesis. Of the adducts formed in response to AOM, O(6)-methyl-2'-deoxy-guanosine (O(6)-mdGua) is the most mutagenic. Based on studies in rodents of the abundance and persistence of DNA adducts in various tissues after treatment with alkylating agents, previous results suggest, as a generalization, that the longer O(6)-mdGua adducts remain unrepaired in the cells of a tissue, the greater the risk for tumorigenesis. To test this hypothesis, we have built on these studies, expanding the number of tissues in which O(6)-mdGua abundance and persistence were examined and correlating these data with tumour distribution and abundance in rats maintained for 26 weeks after the treatment with AOM. Our study revealed firstly the existence of groups of tissues that developed relatively large amounts (proximal and distal colon, proximal small intestine (SI), liver and kidney) and relatively low levels (stomach, distal SI, bladder, spleen, blood and lung) of O(6)-mdGua after AOM exposure. Secondly, while all tissues showed an increase in adduct levels at 6h after mutagen treatment and most showed a significant drop in adduct levels between 6h and 48h (stomach, proximal and distal SI, liver, spleen, blood and lung), one group of tissues displayed O(6)-mdGua levels that did not decrease at 48h (proximal and distal colon, kidney and bladder). Predictably, the colon displayed tumours 26 weeks after treatment. Interestingly, however, the proximal SI also displayed significant tumour formation at that time. Our findings demonstrate (1) a direct association between exposure to O(6)-mdGua and tumours of the distal colon and (2) a dissociation of the relationship between adduct clearance and tumorigenesis in the SI. This diversity of response in the gastrointestinal tract warrants further analysis.