In vitro analysis of partially hydrolyzed guar gum fermentation differences between six individuals

Understanding the role of the human gut microbiome in overweight and obesity

The gut microbiome may be related to the prevalence of overweight and obesity, but high interindividual variability of the human microbiome complicates our understanding. Obesity often occurs concomitantly with micronutrient deficiencies that impair energy metabolism. Microbiota composition is affected by diet. Host-microbiota interactions are bidirectional. We propose three pathways whereby these interactions may modulate the gut microbiome and obesity: (1) ingested compounds or derivatives affecting small intestinal transit, endogenous secretions, digestion, absorption, microbiome balance, and gut barrier function directly affect host metabolism; (2) substrate availability affecting colonic microbial composition and contact with the gut barrier; and (3) microbial end products affecting host metabolism. The quantity/concentration, duration, and/or frequency (circadian rhythm) of changes in these pathways can alter the gut microbiome, disrupt the gut barrier, alter host immunity, and increase the risk of and progression to overweight and obesity. Host-specific characteristics (e.g., genetic variations) may further affect individual sensitivity and/or resilience to diet- and microbiome-associated perturbations in the colonic environment. In this narrative review, the effects of selected interventions, including fecal microbiota transplantation, dietary calorie restriction, dietary fibers and prebiotics, probiotics and synbiotics, vitamins, minerals, and fatty acids, on the gut microbiome, body weight, and/or adiposity are summarized to help identify mechanisms of action and research opportunities.

Role of Baseline Gut Microbiota on Response to Fiber Intervention in Individuals with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most prevalent functional gut disorders in the world. Partially hydrolyzed guar gum, a low-viscosity soluble fiber, has shown promise in the management of IBS-related symptoms. In this study, we aimed to determine if an individual's baseline gut microbiota impacted their response to a partially hydrolyzed guar gum intervention. Patients diagnosed with IBS undertook a 90-day intervention and follow-up. IBS symptom severity, tolerability, quality-of-life, and fecal microbiome composition were recorded during this study. Patients with normal microbiota diversity (Shannon index ≥ 3) showed significant improvements to IBS symptom scores, quality-of-life, and better tolerated the intervention compared to patients with low microbiota diversity (Shannon index < 3). Our findings suggest that an individual's baseline microbiome composition exerts a substantial influence on their response to fiber intervention. Future investigations should explore a symbiotic approach to the treatment of IBS.

Short Chain Fatty Acid Metabolism in Relation to Gut Microbiota and Genetic Variability

It is widely accepted that the gut microbiota plays a significant role in modulating inflammatory and immune responses of their host. In recent years, the host-microbiota interface has gained relevance in understanding the development of many non-communicable chronic conditions, including cardiovascular disease, cancer, autoimmunity and neurodegeneration. Importantly, dietary fibre (DF) and associated compounds digested by the microbiota and their resulting metabolites, especially short-chain fatty acids (SCFA), were significantly associated with health beneficial effects, such as via proposed anti-inflammatory mechanisms. However, SCFA metabolic pathways are not fully understood. Major steps include production of SCFA by microbiota, uptake in the colonic epithelium, first-pass effects at the liver, followed by biodistribution and metabolism at the host's cellular level. As dietary patterns do not affect all individuals equally, the host genetic makeup may play a role in the metabolic fate of these metabolites, in addition to other factors that might influence the microbiota, such as age, birth through caesarean, medication intake, alcohol and tobacco consumption, pathogen exposure and physical activity. In this article, we review the metabolic pathways of DF, from intake to the intracellular metabolism of fibre-derived products, and identify possible sources of inter-individual variability related to genetic variation. Such variability may be indicative of the phenotypic flexibility in response to diet, and may be predictive of long-term adaptations to dietary factors, including maladaptation and tissue damage, which may develop into disease in individuals with specific predispositions, thus allowing for a better prediction of potential health effects following personalized intervention with DF.

Partially Hydrolyzed Guar Gum Modulates Gut Microbiota, Regulates the Levels of Neurotransmitters, and Prevents CUMS-Induced Depressive-Like Behavior in Mice

SCOPE

Depression is the leading cause of disability around the world; however, most antidepressants have drug tolerance and serious side effects. In this study, it is explored whether partially hydrolyzed guar gum (PHGG) is a safe food that exhibits protection in a mouse model of depression.

METHODS AND RESULTS

PHGG is orally administered to mice with depression induced by chronic unpredictable mild stress (CUMS) in two animal experiments (prevention trial and intervention trial) to characterize the potentially protective effect of PHGG. The results in the prevention trial show that PHGG significantly inhibits the loss of body weight, and prevents CUMS-induced depressive-like behavior in mice. The beneficial effects may be associated with PHGG modulating the gut microbiota structure and then increasing the levels of short-chain fatty acids in mice feces and the levels of 5-hydroxytryptamine and dopamine in serum, striatum, and hippocampus. Besides, PHGG in the intervention trial is less effective than that in the prevention trial, but it may have a synergistic effect on improving depression with fluoxetine.

CONCLUSIONS

This study suggests that moderate daily intake of PHGG can contribute to relieving depressive-like behavior.

Plant Prebiotics and Their Role in the Amelioration of Diseases

Prebiotics are either natural or synthetic non-digestible (non-)carbohydrate substances that boost the proliferation of gut microbes. Undigested fructooligosaccharides in the large intestine are utilised by the beneficial microorganisms for the synthesis of short-chain fatty acids for their own growth. Although various food products are now recognized as having prebiotic properties, several others, such as almonds, artichoke, barley, chia seeds, chicory, dandelion greens, flaxseeds, garlic, and oats, are being explored and used as functional foods. Considering the benefits of these prebiotics in mineral absorption, metabolite production, gut microbiota modulation, and in various diseases such as diabetes, allergy, metabolic disorders, and necrotising enterocolitis, increasing attention has been focused on their applications in both food and pharmaceutical industries, although some of these food products are actually used as food supplements. This review aims to highlight the potential and need of these prebiotics in the diet and also discusses data related to the distinct types, sources, modes of action, and health benefits.

Impact of the source of fermentable carbohydrate on SCFA production by human gut microbiota in vitro - a systematic scoping review and secondary analysis

Short chain fatty acids (SCFA) are produced by bacterial fermentation of non-digestible carbohydrates (NDC) and have many potential tissue and SCFA specific actions, from providing fuel for colonic cells to appetite regulation. Many studies have described the fermentation of different carbohydrates, often using in vitro batch culture. As evidence-based critical evaluation of substrates selectively promoting production of individual SCFA is lacking, we performed a systematic scoping literature review. Databases were searched to identify relevant papers published between 1900 and 12/06/2016. Search terms included In vitro batch fermentation and In vitro short chain fatty acid production. Articles were considered for essential criteria allowing equivalent comparison of SCFA between NDC. Seventy seven articles were included in the final analysis examining 29 different carbohydrates. After 24-hour fermentation, galacto-oligosaccharide ranked highest for butyrate and total SCFA production and second for acetate production. Rhamnose ranked highest for propionate production. The lowest SCFA production was observed for kiwi fiber, polydextrose, and cellulose. This review demonstrates that choosing a substrate to selectively enhance a specific SCFA is difficult, and the molar proportion of each SCFA produced by individual substrates may be misleading. Instead the rate and ratio of SCFA production should be evaluated in parallel.

Effect of β-Glucan and Black Tea in a Functional Bread on Short Chain Fatty Acid Production by the Gut Microbiota in a Gut Digestion/Fermentation Model

β-Glucan and black tea are fermented by the colonic microbiota producing short chain fatty acids (SCFA) and phenolic acids (PA). We hypothesized that the addition of β-glucan, a dietary fiber, and tea polyphenols to a food matrix like bread will also affect starch digestion in the upper gut and thus further influence colonic fermentation and SCFA production. This study investigated SCFA and PA production from locally developed breads: white bread (WB), black tea bread (BT), β-glucan bread (βG), β-glucan plus black tea bread (βGBT). Each bread was incubated in an in vitro system mimicking human digestion and colonic fermentation. Digestion with α-amylase significantly (p = 0.0001) increased total polyphenol and polyphenolic metabolites from BT bread compared with WB, βG, and βGBT. Total polyphenols in βGBT remained higher (p = 0.016; 1.3-fold) after digestion with pepsin and pancreatin compared with WB. Fermentations containing βG and βGBT produced similar propionate concentrations ranging from 17.5 to 18.6 mmol/L and total SCFA from 46.0 to 48.9 mmol/L compared with control WB (14.0 and 37.4 mmol/L, respectively). This study suggests that combination of black tea with β-glucan in this functional bread did not impact on SCFA production. A higher dose of black tea and β-glucan or in combination with other fibers may be needed to increase SCFA production.

Polyphenol-rich Mango (Mangifera indica L.) Ameliorate Functional Constipation Symptoms in Humans beyond Equivalent Amount of Fiber

SCOPE

Chronic constipation is a common gastrointestinal condition associated with intestinal inflammation and considerably impaired quality of life, affecting about 20% of Americans. Dietary fiber and laxatives aid in its treatment but do not fully address all symptoms, such as intestinal inflammation. Mango (Mangifera indica L.), a fiber- and polyphenol-rich fruit may provide anti-inflammatory effects in constipation.

METHODS AND RESULTS

The 4 week consumption of mango fruit (300 g) or the equivalent amount of fiber is investigated in otherwise healthy human volunteers with chronic constipation who are randomly assigned to either group. Blood and fecal samples and digestive wellness questionnaires are collected at the beginning and end of the study. Results show that mango consumption significantly improve constipation status (stool frequency, consistency, and shape) and increase gastrin levels and fecal concentrations of short chain fatty acid (valeric acid) while lowering endotoxin and interleukin 6 concentrations in plasma.

CONCLUSION

In this pilot study, the consumption of mango improves symptoms and associated biomarkers of constipation beyond an equivalent amount of fiber. Larger follow-up studies would need to investigate biomarkers for intestinal inflammation in more detail.

Health Effects and Sources of Prebiotic Dietary Fiber

Prebiotic dietary fibers act as carbon sources for primary and secondary fermentation pathways in the colon, and support digestive health in many ways. Fructooligosaccharides, inulin, and galactooligosaccharides are universally agreed-upon prebiotics. The objective of this paper is to summarize the 8 most prominent health benefits of prebiotic dietary fibers that are due to their fermentability by colonic microbiota, as well as summarize the 8 categories of prebiotic dietary fibers that support these health benefits. Although not all categories exhibit similar effects in human studies, all of these categories promote digestive health due to their fermentability. Scientific and regulatory definitions of prebiotics differ greatly, although health benefits of these compounds are uniformly agreed upon to be due to their fermentability by gut microbiota. Scientific evidence suggests that 8 categories of compounds all exhibit health benefits related to their metabolism by colonic taxa.

Fermentability of Novel Type-4 Resistant Starches in In Vitro System

Resistant starches are non-digestible starches that are fermented in the colon by microbiota. These carbohydrates are prebiotic and can be beneficial to consumer health. Many types of resistant starch exist with varying physical properties that may result in differences in fermentability. The objective of this research project was to compare potential prebiotic effects and fermentability of four novel resistant starches using an in vitro fermentation system and measuring changes in total gas production, pH, and formation of SCFAs (short chain fatty acids). Fecal donations were collected from seven healthy volunteers. Four novel resistant starches, modified potato starch (MPS), modified tapioca starch (MTS), and modified maize starches (MMS-1 and MMS-2), were analyzed and compared to polydextrose and short chain fructooligosaccharides (FOS) as controls. After twenty-four hours of fermentation, MPS and MTS responded similarly in gas production (74 mL; 70.6 mL respectively), pH (5.93; 5.93 respectively), and SCFA production (Acetate: 115; 124, Propionate: 21; 26, Butyrate: 29; 31 μmol/mL respectively). While MMS-1 had similar gas production and individual SCFA production, the pH was significantly higher (6.06). The fermentation of MMS-2 produced the least amount of gas (22 mL), with a higher pH (6.34), and lower acetate production (78.4 μmol/mL). All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.