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      Soluble fibre supplementation with and without a probiotic in adults with asthma: A 7-day randomised, double blind, three way cross-over trial

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          Summary

          Background

          Soluble fibre modulates airway inflammation in animal models. The aim of this study was to investigate the effects of soluble fibre supplementation, with and without a probiotic, on plasma short chain fatty acids (SCFA), airway inflammation, asthma control and gut microbiome in adults with asthma.

          Methods

          A randomised, double-blinded, placebo controlled 3-way cross-over trial in 17 subjects with stable asthma at the Hunter Medical Research Institute, Newcastle, Australia. Subjects received 3 × 7 day oral interventions in random order; soluble fibre (inulin 12 g/day), soluble fibre + probiotic (inulin 12 g/day + multi-strain probiotic >25 billion CFU) and placebo. Plasma SCFA, sputum cell counts and inflammatory gene expression, asthma control gut microbiota, adverse events including gastrointestinal symptoms were measured.

          Findings

          There was no difference in change in total plasma SCFA levels (μmol/L) in the placebo versus soluble fibre (Δmedian [95% CI] 16·3 [−16·9, 49·5], p = 0·335) or soluble fibre+probiotic (18·7 [−14·5, 51·9], p = 0·325) group. Following the soluble fibre intervention there was an improvement in the asthma control questionnaire (ACQ6) (∆median (IQR) -0·35 (−0·5, −0·13), p = 0·006), sputum %eosinophils decreased (−1.0 (−2·5, 0), p = 0·006) and sputum histone deacetylase 9 (HDAC9) gene expression decreased (−0.49 (−0.83, −0.27) 2 -ΔCt, p = .008). Individual bacterial operational taxonomic units changed following both inulin and inulin+probiotic arms.

          Interpretation

          Soluble fibre supplementation for 7 days in adults with asthma did not change SCFA levels. Within group analysis showed improvements in airway inflammation, asthma control and gut microbiome composition following inulin supplementation and these changes warrant further investigation, in order to evaluate the potential of soluble fibre as a non-pharmacological addition to asthma management.

          Fund

          John Hunter Hospital Charitable Trust.

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          Most cited references50

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          Functional characterization of human receptors for short chain fatty acids and their role in polymorphonuclear cell activation.

          Short chain fatty acids (SCFAs), including acetate, propionate, and butyrate, are produced at high concentration by bacteria in the gut and subsequently released in the bloodstream. Basal acetate concentrations in the blood (about 100 microm) can further increase to millimolar concentrations following alcohol intake. It was known previously that SCFAs can activate leukocytes, particularly neutrophils. In the present work, we have identified two previously orphan G protein-coupled receptors, GPR41 and GPR43, as receptors for SCFAs. Propionate was the most potent agonist for both GPR41 and GPR43. Acetate was more selective for GPR43, whereas butyrate and isobutyrate were more active on GPR41. The two receptors were coupled to inositol 1,4,5-trisphosphate formation, intracellular Ca2+ release, ERK1/2 activation, and inhibition of cAMP accumulation. They exhibited, however, a differential coupling to G proteins; GPR41 coupled exclusively though the Pertussis toxin-sensitive Gi/o family, whereas GPR43 displayed a dual coupling through Gi/o and Pertussis toxin-insensitive Gq protein families. The broad expression profile of GPR41 in a number of tissues does not allow us to infer clear hypotheses regarding its biological functions. In contrast, the highly selective expression of GPR43 in leukocytes, particularly polymorphonuclear cells, suggests a role in the recruitment of these cell populations toward sites of bacterial infection. The pharmacology of GPR43 matches indeed the effects of SCFAs on neutrophils, in terms of intracellular Ca2+ release and chemotaxis. Such a neutrophil-specific SCFA receptor is potentially involved in the development of a variety of diseases characterized by either excessive or inefficient neutrophil recruitment and activation, such as inflammatory bowel diseases or alcoholism-associated immune depression. GPR43 might therefore constitute a target allowing us to modulate immune responses in these pathological situations.
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            Dietary modulation of the human colonic microbiota: updating the concept of prebiotics.

            Prebiotics are non-digestible (by the host) food ingredients that have a beneficial effect through their selective metabolism in the intestinal tract. Key to this is the specificity of microbial changes. The present paper reviews the concept in terms of three criteria: (a) resistance to gastric acidity, hydrolysis by mammalian enzymes and gastrointestinal absorption; (b) fermentation by intestinal microflora; (c) selective stimulation of the growth and/or activity of intestinal bacteria associated with health and wellbeing. The conclusion is that prebiotics that currently fulfil these three criteria are fructo-oligosaccharides, galacto-oligosaccharides and lactulose, although promise does exist with several other dietary carbohydrates. Given the range of food vehicles that may be fortified by prebiotics, their ability to confer positive microflora changes and the health aspects that may accrue, it is important that robust technologies to assay functionality are used. This would include a molecular-based approach to determine flora changes. The future use of prebiotics may allow species-level changes in the microbiota, an extrapolation into genera other than the bifidobacteria and lactobacilli, and allow preferential use in disease-prone areas of the body.
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              Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii.

              Prebiotics are food ingredients that improve health by modulating the colonic microbiota. The bifidogenic effect of the prebiotic inulin is well established; however, it remains unclear which species of Bifidobacterium are stimulated in vivo and whether bacterial groups other than lactic acid bacteria are affected by inulin consumption. Changes in the faecal microbiota composition were examined by real-time PCR in twelve human volunteers after ingestion of inulin (10 g/d) for a 16-d period in comparison with a control period without any supplement intake. The prevalence of most bacterial groups examined did not change after inulin intake, although the low G+C % Gram-positive species Faecalibacterium prausnitzii exhibited a significant increase (10.3% for control period v. 14.5% during inulin intake, P=0.019). The composition of the genus Bifidobacterium was studied in four of the volunteers by clone library analysis. Between three and five Bifidobacterium spp. were found in each volunteer. Bifidobacterium adolescentis and Bifidobacterium longum were present in all volunteers, and Bifidobacterium pseudocatenulatum, Bifidobacterium animalis, Bifidobacterium bifidum and Bifidobacterium dentium were also detected. Real-time PCR was employed to quantify the four most prevalent Bifidobacterium spp., B. adolescentis, B. longum, B. pseudocatenulatum and B. bifidum, in ten volunteers carrying detectable levels of bifidobacteria. B. adolescentis showed the strongest response to inulin consumption, increasing from 0.89 to 3.9% of the total microbiota (P=0.001). B. bifidum was increased from 0.22 to 0.63% (P<0.001) for the five volunteers for whom this species was present.
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                Author and article information

                Contributors
                Journal
                EBioMedicine
                EBioMedicine
                EBioMedicine
                Elsevier
                2352-3964
                31 July 2019
                August 2019
                31 July 2019
                : 46
                : 473-485
                Affiliations
                [a ]Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, University of Newcastle, NSW, Australia
                [b ]South Australian Health and Medical Research Institute, Microbiome & Host Health Programme, South Australia, Australia
                [c ]College of Medicine and Public Health, Flinders University, South Australia, Australia
                [d ]Microbiology and Infectious Diseases, SA Pathology, South Australia, Australia
                [e ]Department of Respiratory and Sleep Medicine, John Hunter Hospital, Newcastle, NSW, Australia
                Author notes
                [* ]Corresponding author at: Centre Healthy Lungs, Level 2, West Wing, Hunter Medical Research Institute, Lot 1 Kookaburra Circuit, New Lambton Heights, NSW 2305, Australia. lisa.wood@ 123456newcastle.edu.au
                [1]

                These authors contributed equally

                Article
                S2352-3964(19)30490-6
                10.1016/j.ebiom.2019.07.048
                6712277
                31375426
                f11a292f-5472-433a-8b82-d4506b2790f9
                © 2019 The Authors

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 21 May 2019
                : 18 July 2019
                : 18 July 2019
                Categories
                Research paper

                asthma,inulin,soluble fibre,scfas,inflammation,free fatty acid receptors,histone deacetylases

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