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      Hypocholesterolemic and Prebiotic Effects of a Whole-Grain Oat-Based Granola Breakfast Cereal in a Cardio-Metabolic “At Risk” Population

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          Abstract

          Meta-analyses of randomized controlled trials (RTC) have confirmed the hypocholesterolaemic effect of oats and oat based fibers. However, the mechanisms by which oats or oat fractions lower cholesterol is not totally clear. Recognizing the important role of the gut microbiome in metabolism and metabolic disease risk, we examined the impact of whole grain oat Granola (WGO) on the human gut microbiota and cardio-metabolic risk factors using a randomized crossover dietary intervention in at risk individuals (ClinicalTrials.gov Identifier: NCT01925365). We randomized 32 individuals at risk of developing cardio-metabolic disease by virtue of mild hypercholesterolaemia or glucose intolerance, into two groups consuming either 45 g of WGO or non-whole grain (NWG) breakfast cereals daily for two 6-week intervention periods separated by a 4-week wash out period in a randomized, controlled, crossover, double-blinded design. Confirming the cholesterol lowering effect of WGO, we observed a significant time by treatment interaction, for total cholesterol (TC) ( P = 0.0001) and LDL-cholesterol (LDL-C) ( P = 0.02) compared to NWG. A significant time by treatment interaction was also observed for the relative abundance of fecal bifidobacteria ( P = 0.0001), lactobacilli ( P = 0.001) and total bacterial count ( P = 0.008), which were all elevated after consumption of WGO. Daily consumption of WGO resulted in a prebiotic effect on the human gut microbiota composition and significant reductions in TC and LDL-C concentrations. Prebiotic modulation of the human gut microbiota may thus constitute a previously unrecognized mechanism contributing to the hypocholesterolaemic effects of whole grain oat Granola.

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          Application of a suite of 16S rRNA-specific oligonucleotide probes designed to investigate bacteria of the phylum cytophaga-flavobacter-bacteroides in the natural environment.

          We designed a panel of four 16S rRNA-targeted oligonucleotide probes specific for bacteria of the phylum cytophaga-flavobacter-bacteroides (CFB). Probes CF319a and CF319b are targeted to members of the flavobacteria-cytophaga group and the genus Porphyromonas, whereas probe BAC303 has a target region characteristic for the genera Prevotella and Bacteroides within the bacteroides group. The probe FFE8b was developed for species-specific hybridizations with Flavobacterium ferrugineum. All probes were designed by computer-assisted sequence analysis and compared to all currently accessible 16S and 23S rRNA sequences. The oligonucleotides were further evaluated by whole-cell and non-radioactive dot-blot hybridization against reference strains of the CFB phylum and other major lineages of Bacteria. The newly developed probes were used together with other higher-order probes to analyse the structure and community composition in complex environments. In activated sludge samples, members of the flavobacteria-cytophaga group were revealed by in situ hybridization as important constituents of sludge flocs and characteristic colonizers of filamentous bacteria. By application of fluorescent probe BAC303, members of the genera Bacteroides and Prevotella could be visualized without prior cultivation as an important part of the human faecal microflora.
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            Whole-grain wheat breakfast cereal has a prebiotic effect on the human gut microbiota: a double-blind, placebo-controlled, crossover study.

            Epidemiological studies have shown an inverse association between dietary intake of whole grains and the risk of chronic disease. This may be related to the ability to mediate a prebiotic modulation of gut microbiota. However, no studies have been conducted on the microbiota modulatory capability of whole-grain (WG) cereals. In the present study, the impact of WG wheat on the human intestinal microbiota compared to wheat bran (WB) was determined. A double-blind, randomised, crossover study was carried out in thirty-one volunteers who were randomised into two groups and consumed daily 48 g breakfast cereals, either WG or WB, in two 3-week study periods, separated by a 2-week washout period. Numbers of faecal bifidobacteria and lactobacilli (the target genera for prebiotic intake), were significantly higher upon WG ingestion compared with WB. Ingestion of both breakfast cereals resulted in a significant increase in ferulic acid concentrations in blood but no discernible difference in faeces or urine. No significant differences in faecal SCFA, fasting blood glucose, insulin, total cholesterol (TC), TAG or HDL-cholesterol were observed upon ingestion of WG compared with WB. However, a significant reduction in TC was observed in volunteers in the top quartile of TC concentrations upon ingestion of either cereal. No adverse intestinal symptoms were reported and WB ingestion increased stool frequency. Daily consumption of WG wheat exerted a pronounced prebiotic effect on the human gut microbiota composition. This prebiotic activity may contribute towards the beneficial physiological effects of WG wheat.
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              Mechanisms underlying the cholesterol-lowering properties of soluble dietary fibre polysaccharides.

              A number of studies have shown a positive relationship between diets rich in soluble dietary fibres (SDF) such as β-glucan, pectin, guar gum and psyllium, and reduced serum cholesterol and thus a decreased risk of cardiovascular disease (CVD). Three major biological mechanisms have been proposed to explain the cholesterol-reducing effects of SDF: prevention of bile salt (BS) re-absorption from the small intestine leading to an excess faecal BS excretion; reduced glycemic response leading to lower insulin stimulation of hepatic cholesterol synthesis; and physiological effects of fermentation products of SDF, mainly propionate. Evidence for the latter mechanism is inconclusive, whereas in vivo, ex vivo and in vitro experiments suggest that BS micelles "bind" to SDF preventing their re-absorption. Whereas, glycemic responses to SDF have been studied extensively, the nature of interactions between bile salt micelles and SDF that lead to incomplete BS re-absorption are poorly defined. Three potential physicochemical mechanisms are proposed together with suggestions for in vitro experiments to test them.
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                Author and article information

                Contributors
                Journal
                Front Microbiol
                Front Microbiol
                Front. Microbiol.
                Frontiers in Microbiology
                Frontiers Media S.A.
                1664-302X
                07 November 2016
                2016
                : 7
                : 1675
                Affiliations
                [1] 1Hugh Sinclair Unit of Human Nutrition, University of Reading Reading, UK
                [2] 2Institute for Cardiovascular and Metabolic Research, University of Reading Reading, UK
                [3] 3Department of Food Quality and Nutrition, Research and Innovation Centre - Fondazione Edmund Mach Trento, Italy
                Author notes

                Edited by: Francesca Turroni, University College Cork, Ireland

                Reviewed by: Marco Ventura, University of Parma, Italy; Francesca Scazzina, University of Parma, Italy

                *Correspondence: Kieran M. Tuohy k.m.tuohy@ 123456fmach.it

                This article was submitted to Microbial Symbioses, a section of the journal Frontiers in Microbiology

                Article
                10.3389/fmicb.2016.01675
                5098205
                27872611
                771bbc8e-f701-4b17-b02c-5a154f918bb9
                Copyright © 2016 Connolly, Tzounis, Tuohy and Lovegrove.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 06 May 2016
                : 06 October 2016
                Page count
                Figures: 2, Tables: 4, Equations: 0, References: 47, Pages: 9, Words: 7243
                Categories
                Microbiology
                Original Research

                Microbiology & Virology
                whole-grain oat granola,prebiotic,cholesterol,cardiovascular risk,bifidobacterium

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