Potential of novel dextran oligosaccharides as prebiotics for obesity management through in vitro experimentation

The energy-salvaging capacity of the gut microbiota from dietary ingredients has been proposed as a contributing factor for the development of obesity. This knowledge generated interest in the use of non-digestible dietary ingredients such as prebiotics to manipulate host energy homeostasis. In the present study, the in vitro response of obese human faecal microbiota to novel oligosaccharides was investigated. Dextrans of various molecular weights and degrees of branching were fermented with the faecal microbiota of healthy obese adults in pH-controlled batch cultures. Changes in bacterial populations were monitored using fluorescent in situ hybridisation and SCFA concentrations were analysed by HPLC. The rate of gas production and total volume of gas produced were also determined. In general, the novel dextrans and inulin increased the counts of bifidobacteria. Some of the dextrans were able to alter the composition of the obese human microbiota by increasing the counts of Bacteroides–Prevotella and decreasing those of Faecalibacterium prausnitzii and Ruminococcus bromii/R. flavefaciens. Considerable increases in SCFA concentrations were observed in response to all substrates. Gas production rates were similar during the fermentation of all dextrans, but significantly lower than those during the fermentation of inulin. Lower total gas production and shorter time to attain maximal gas production were observed during the fermentation of the linear 1 kDa dextran than during the fermentation of the other dextrans. The efficacy of bifidobacteria to ferment dextrans relied on the molecular weight and not on the degree of branching. In conclusion, there are no differences in the profiles between the obese and lean human faecal fermentations of dextrans

Prebiotic potential of a maize-based soluble fibre and impact of dose on the human gut microbiota

Dietary management of the human gut microbiota towards a more beneficial composition is one approach that may improve host health. To date, a large number of human intervention studies have demonstrated that dietary consumption of certain food products can result in significant changes in the composition of the gut microbiota i.e. the prebiotic concept. Thus the prebiotic effect is now established as a dietary approach to increase beneficial gut bacteria and it has been associated with modulation of health biomarkers and modulation of the immune system. Promitor™ Soluble Corn Fibre (SCF) is a well-known maize-derived source of dietary fibre with potential selective fermentation properties. Our aim was to determine the optimum prebiotic dose of tolerance, desired changes to microbiota and fermentation of SCF in healthy adult subjects. A double-blind, randomised, parallel study was completed where volunteers (n = 8/treatment group) consumed 8, 14 or 21 g from SCF (6, 12 and 18 g/fibre delivered respectively) over 14-d. Over the range of doses studied, SCF was well tolerated Numbers of bifidobacteria were significantly higher for the 6 g/fibre/day compared to 12g and 18g/fibre delivered/day (mean 9.25 and 9.73 Log10 cells/g fresh faeces in the pre-treatment and treatment periods respectively). Such a numerical change of 0.5 Log10 bifidobacteria/g fresh faeces is consistent with those changes observed for inulin-type fructans, which are recognised prebiotics. A possible prebiotic effect of SCF was therefore demonstrated by its stimulation of bifidobacteria numbers in the overall gut microbiota during a short-term intervention

Study design of a double-blind, randomised, parallel study with eight volunteers per treatment group, and consisting of a pre-treatment and treatment period (14-days).

<p>Treatments with were 8, 14 and 21 g-SCF/d designed to 6, 12 and 18 g fibre/delivered/day from Promitor™ Soluble Corn Fibre (SCF).</p

Representative baseline (pre-contrast) MRI images of the mouse brain showing assignment of regions of interest (ROIs) in various brain areas from which signal intensities (SI) were obtained.

<p>Time course of changes in SI (as a percentage of baseline) before and at various times after IV manganese chloride infusion in the (a) ARC, (b) VMH (c) PVN (d) PE (e) NTS. Data are presented as means of four consecutive image acquisitions±SEM. * = p<0.05, ** = p<0.01, *** = p<0.001 Key: ARC, arcuate nucleus; VMH, ventromedial hypothalamic nucleus; PVN, paraventricular hypothalamic nucleus; PE, periventricular nucleus; NTS, nucleus of solitaries tractus; HFD-C, high fat diet control; HFD-I, high fat diet+inulin; HFD-BG, high fat diet+β-glucan.</p

Flowchart showing the study design.

<p>Flowchart showing the study design.</p

Multivariate statistical analysis of the fecal ¹H NMR spectra.

<p>OPLS-DA cross validated scores plots for mice fed with (a) HFD-C and HDF-BG; and (b) HFD-C and HFD-I. The corresponding coefficient plots indicated fecal metabolic differences for (c) HFD-C and HFD-BG; and (d) HFD-C and HFD-I. Insets show an expansion of the aromatic region. HFD-C, high fat diet control; HFD-I, high fat diet+inulin; HFD-BG, high fat diet+β-glucan. 1, Bile acids; 2, Butyrate; 3, Isoleucine, leucine and valine; 4, Propionate (tentative); 5, Unknown at δ 1.17 (doublets) ; 6, Lactate; 7, Alanine; 8, Acetate; 9 Glutamate (tentative); 10, Succinate; 11, Aspartate; 12, Citrate; 13, Lysine; 14, Glycine; 15, Glucose and amino acids; 16, Glucose; 17, Uracil; 18, Fumarate; 19, Thyrosine; 20, Phenylalanine; 21, Histidine; 22, Unknown at δ7.84 (doublets); 23, Unknown at δ8.02 (doublets); 24, Unknown at δ8.20 (doublets); 25, Amine related compounds.</p

The effect of inulin and β-glucan supplementation over the 8-week dietary interventional period (a) weekly cumulative body weight gain, n = 12 per group (b) weekly cumulative food intake over the 8 week dietary intervention period, n = 12 per group. * = p<0.05, ** = p<0.01, *** = p<0.001.

<p>Key: HFD-C, high fat diet control; HFD-I, high fat diet+inulin; HFD-BG, high fat diet+β-glucan.</p

Effect of inulin and β-glucan supplementation on adiposity parameters and tissue weights in high fat fed mice (n = 6).

<p>Superscipt (*) shows the significant difference between HFD-I or HFD-BG vs. HFD-C.</p>*<p> = P<0.05,</p>**<p> = P<0.01,</p>***<p> = P<0.001.</p><p>Superscipt (#) shows the significant difference between HFD-I vs. HFD-BG.</p>#<p> = P<0.05,</p>##<p> = P<0.01.</p

The effect of inulin and β-glucan supplementation on cecal and fecal microbial contents over the 8-week dietary interventional period (a) cecal microflora groups, n = 6 per group (b) fecal total bacteria microflora at week 0, 4 and 8, n = 6 per group: (c) fecal mouse intestinal bacteria, (d) fecal <i>Eubacterium rectal-Clostridium coccoides</i>; (e) fecal Lactobacilli; and (f) fecal Bifidobacteria. * = p<0.05, ** = p<0.01, *** = p<0.001.

<p>Key: HFD-C, high fat diet control; HFD-I, high fat diet+inulin; HFD-BG, high fat diet+β-glucan.</p