Faecal microbial transfer and complex carbohydrates mediate protection against COPD

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a major cause of global illness and death, most commonly caused by cigarette smoke. The mechanisms of pathogenesis remain poorly understood, limiting the development of effective therapies. The gastrointestinal microbiome has been implicated in chronic lung diseases via the gut-lung axis, but its role is unclear.

DESIGN

Using an in vivo mouse model of cigarette smoke (CS)-induced COPD and faecal microbial transfer (FMT), we characterised the faecal microbiota using metagenomics, proteomics and metabolomics. Findings were correlated with airway and systemic inflammation, lung and gut histopathology and lung function. Complex carbohydrates were assessed in mice using a high resistant starch diet, and in 16 patients with COPD using a randomised, double-blind, placebo-controlled pilot study of inulin supplementation.

RESULTS

FMT alleviated hallmark features of COPD (inflammation, alveolar destruction, impaired lung function), gastrointestinal pathology and systemic immune changes. Protective effects were additive to smoking cessation, and transfer of CS-associated microbiota after antibiotic-induced microbiome depletion was sufficient to increase lung inflammation while suppressing colonic immunity in the absence of CS exposure. Disease features correlated with the relative abundance of Muribaculaceae, Desulfovibrionaceae and Lachnospiraceae family members. Proteomics and metabolomics identified downregulation of glucose and starch metabolism in CS-associated microbiota, and supplementation of mice or human patients with complex carbohydrates improved disease outcomes.

CONCLUSION

The gut microbiome contributes to COPD pathogenesis and can be targeted therapeutically.

Prebiotic diet changes neural correlates of food decision-making in overweight adults: a randomised controlled within-subject cross-over trial

OBJECTIVE

Animal studies suggest that prebiotic, plant-derived nutrients could improve homoeostatic and hedonic brain functions through improvements in microbiome-gut-brain communication. However, little is known if these results are applicable to humans. Therefore, we tested the effects of high-dosed prebiotic fibre on reward-related food decision-making in a randomised controlled within-subject cross-over study and assayed potential microbial and metabolic markers.

DESIGN

59 overweight young adults (19 females, 18-42 years, body mass index 25-30 kg/m2) underwent functional task MRI before and after 14 days of supplementary intake of 30 g/day of inulin (prebiotics) and equicaloric placebo, respectively. Short chain fatty acids (SCFA), gastrointestinal hormones, glucose/lipid and inflammatory markers were assayed in fasting blood. Gut microbiota and SCFA were measured in stool.

RESULTS

Compared with placebo, participants showed decreased brain activation towards high-caloric wanted food stimuli in the ventral tegmental area and right orbitofrontal cortex after prebiotics (preregistered, family wise error-corrected p <0.05). While fasting blood levels remained largely unchanged, 16S-rRNA sequencing showed significant shifts in the microbiome towards increased occurrence of, among others, SCFA-producing Bifidobacteriaceae, and changes in >60 predicted functional signalling pathways after prebiotic intake. Changes in brain activation correlated with changes in Actinobacteria microbial abundance and associated activity previously linked with SCFA production, such as ABC transporter metabolism.

CONCLUSIONS

In this proof-of-concept study, a prebiotic intervention attenuated reward-related brain activation during food decision-making, paralleled by shifts in gut microbiota.

TRIAL REGISTRATION NUMBER

NCT03829189.

Strategies used for childhood chronic functional constipation: the SUCCESS evidence synthesis

Background

Up to 30% of children have constipation at some stage in their life. Although often short-lived, in one-third of children it progresses to chronic functional constipation, potentially with overflow incontinence. Optimal management strategies remain unclear.

Objective

To determine the most effective interventions, and combinations and sequences of interventions, for childhood chronic functional constipation, and understand how they can best be implemented.

Methods

Key stakeholders, comprising two parents of children with chronic functional constipation, two adults who experienced childhood chronic functional constipation and four health professional/continence experts, contributed throughout the research. We conducted pragmatic mixed-method reviews. For all reviews, included studies focused on any interventions/strategies, delivered in any setting, to improve any outcomes in children (0-18 years) with a clinical diagnosis of chronic functional constipation (excluding studies of diagnosis/assessment) included. Dual reviewers applied inclusion criteria and assessed risk of bias. One reviewer extracted data, checked by a second reviewer. Scoping review: We systematically searched electronic databases (including Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, Cumulative Index to Nursing and Allied Health Literature) (January 2011 to March 2020) and grey literature, including studies (any design) reporting any intervention/strategy. Data were coded, tabulated and mapped. Research quality was not evaluated. Systematic reviews of the evidence of effectiveness: For each different intervention, we included existing systematic reviews judged to be low risk of bias (using the Risk of Bias Assessment Tool for Systematic Reviews), updating any meta-analyses with new randomised controlled trials. Where there was no existing low risk of bias systematic reviews, we included randomised controlled trials and other primary studies. The risk of bias was judged using design-specific tools. Evidence was synthesised narratively, and a process of considered judgement was used to judge certainty in the evidence as high, moderate, low, very low or insufficient evidence. Economic synthesis: Included studies (any design, English-language) detailed intervention-related costs. Studies were categorised as cost-consequence, cost-effectiveness, cost-utility or cost-benefit, and reporting quality evaluated using the consensus health economic criteria checklist. Systematic review of implementation factors: Included studies reported data relating to implementation barriers or facilitators. Using a best-fit framework synthesis approach, factors were synthesised around the consolidated framework for implementation research domains.

Results

Stakeholders prioritised outcomes, developed a model which informed evidence synthesis and identified evidence gaps.

Scoping review

651 studies, including 190 randomised controlled trials and 236 primary studies, conservatively reported 48 interventions/intervention combinations.

Effectiveness systematic reviews

studies explored service delivery models (n = 15); interventions delivered by families/carers (n = 32), wider children's workforce (n = 21), continence teams (n = 31) and specialist consultant-led teams (n = 42); complementary therapies (n = 15); and psychosocial interventions (n = 4). One intervention (probiotics) had moderate-quality evidence; all others had low to very-low-quality evidence. Thirty-one studies reported evidence relating to cost or resource use; data were insufficient to support generalisable conclusions. One hundred and six studies described implementation barriers and facilitators.

Conclusions

Management of childhood chronic functional constipation is complex. The available evidence remains limited, with small, poorly conducted and reported studies. Many evidence gaps were identified. Treatment recommendations within current clinical guidelines remain largely unchanged, but there is a need for research to move away from considering effectiveness of single interventions. Clinical care and future studies must consider the individual characteristics of children.

Study registration

This study is registered as PROSPERO CRD42019159008.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 128470) and is published in full in Health Technology Assessment; Vol. 28, No. 5. See the NIHR Funding and Awards website for further award information.

High-level adherence to a Mediterranean diet beneficially impacts the gut microbiota and associated metabolome

OBJECTIVES

Habitual diet plays a major role in shaping the composition of the gut microbiota, and also determines the repertoire of microbial metabolites that can influence the host. The typical Western diet corresponds to that of an omnivore; however, the Mediterranean diet (MD), common in the Western Mediterranean culture, is to date a nutritionally recommended dietary pattern that includes high-level consumption of cereals, fruit, vegetables and legumes. To investigate the potential benefits of the MD in this cross-sectional survey, we assessed the gut microbiota and metabolome in a cohort of Italian individuals in relation to their habitual diets.

DESIGN AND RESULTS

We retrieved daily dietary information and assessed gut microbiota and metabolome in 153 individuals habitually following omnivore, vegetarian or vegan diets. The majority of vegan and vegetarian subjects and 30% of omnivore subjects had a high adherence to the MD. We were able to stratify individuals according to both diet type and adherence to the MD on the basis of their dietary patterns and associated microbiota. We detected significant associations between consumption of vegetable-based diets and increased levels of faecal short-chain fatty acids, Prevotella and some fibre-degrading Firmicutes, whose role in human gut warrants further research. Conversely, we detected higher urinary trimethylamine oxide levels in individuals with lower adherence to the MD.

CONCLUSIONS

High-level consumption of plant foodstuffs consistent with an MD is associated with beneficial microbiome-related metabolomic profiles in subjects ostensibly consuming a Western diet.

TRIAL REGISTRATION NUMBER

This study was registered at clinical trials.gov as NCT02118857.

Reduced keratin expression in colorectal neoplasia and associated fields is reversible by diet and resection

BACKGROUND

Patients with adenomatous colonic polyps are at increased risk of developing further polyps suggesting field-wide alterations in cancer predisposition. The current study aimed to identify molecular alterations in the normal mucosa in the proximity of adenomatous polyps and to assess the modulating effect of butyrate, a chemopreventive compound produced by fermentation of dietary residues.

METHODS

A cross-sectional study was undertaken in patients with adenomatous polyps: biopsy samples were taken from the adenoma, and from macroscopically normal mucosa on the contralateral wall to the adenoma and from the mid-sigmoid colon. In normal subjects biopsies were taken from the mid-sigmoid colon. Biopsies were frozen for proteomic analysis or formalin-fixed for immunohistochemistry. Proteomic analysis was undertaken using iTRAQ workflows followed by bioinformatics analyses. A second dietary fibre intervention study arm used the same endpoints and sampling strategy at the beginning and end of a high-fibre intervention.

RESULTS

Key findings were that keratins 8, 18 and 19 were reduced in expression level with progressive proximity to the lesion. Lesional tissue exhibited multiple K8 immunoreactive bands and overall reduced levels of keratin. Biopsies from normal subjects with low faecal butyrate also showed depressed keratin expression. Resection of the lesion and elevation of dietary fibre intake both appeared to restore keratin expression level.

CONCLUSION

Changes in keratin expression associate with progression towards neoplasia, but remain modifiable risk factors. Dietary strategies may improve secondary chemoprevention.

TRIAL REGISTRATION NUMBER

ISRCTN90852168.