MUC2 mucin, the primary gel-forming component of intestinal mucus, is well researched and a model of polymerisation and post-secretory organisation has been published previously. Recently, several significant developments have been made which either introduce new ideas or challenge previous theories. New ideas include an overhaul of the MUC2 C-terminal globular structure which is proposed to harbour several previously unobserved domains, and include a site for an extra intermolecular disulphide bridge dimer between the cysteine 4379 of adjacent MUC2 C-termini. MUC2 polymers are also now thought to be secreted attached to the epithelial surface of goblet cells in the small intestine and removed following secretion via a metalloprotease meprin β-mediated cleavage of the von Willebrand D2 domain of the N-terminus. It remains unclear whether MUC2 forms intermolecular dimers, trimers, or both, at the N-termini during polymerisation, with several articles supporting either trimer or dimer formation. The presence of a firm inner mucus layer in the small intestine is similarly unclear. Considering this recent research, this review proposes an update to the previous model of MUC2 polymerisation and secretion, considers conflicting theories and data, and highlights the importance of this research to the understanding of MUC2 mucus layers in health and disease.

When initiated the human microbiome project did not include the lungs and airways in its sampling sites, indicating an under appreciation of the role of the human lung microbiome in health and disease. This paradigm has recently changed through the use of culture independent methods to characterise the human lung microbiome. The original thinking, that the normal lung was essentially sterile, had previously been challenged by findings of microaspiration in normal volunteers and in patients with decreased levels of consciousness. The sterile lung was also questioned by findings of clinically occult infection markers in lung allograft recipients. What is arguably a “rediscovery” of the importance of the human lung microbiome may still underappreciate physiological and patho-physiological inter-relationships between organ systems, studied in separate research disciplines. In particular, microaspiration may be an important, direct mechanism through which the lung microbiome is modulated. As well as aspiration related to gastro-oesophageal reflux and microaspiration the authors feel that the importance of dysphagia in chronic lung disease, will be increasingly recognised in frailty related microbiome exchange between the oropharynx into the lung. This review therefore discusses interconnections in the human microbiome, with a focus on the potential for aerodigestive pathophysiology and microaspiration. Potential connections with human lung disease are discussed and contextualised within a developing literature. This review therefore highlights much needed new targets for translational intervention in lung pathophysiology and underlies the importance of a mixed disciplinary team approach for the future.

Abstract White kidney bean extract (WKBE) is a nutraceutical often advocated as an anti-obesity agent. The main proposed mechanism for these effects is alpha-amylase inhibition, thereby slowing carbohydrate digestion and absorption. Thus, it is possible that WKBE could impact the gut microbiota and modulate gut health. We investigated the effects of supplementing 20 healthy adults with WKBE for 1 week in a randomised, placebo-controlled crossover trial on the composition of the gut microbiota, gastrointestinal (GI) inflammation (faecal calprotectin), GI symptoms, and stool habits. We conducted in vitro experiments and used a gut model system to explore potential inhibition of alpha-amylase. We gained qualitative insight into participant experiences of using WKBE via focus groups. WKBE supplementation decreased the relative abundance of Bacteroidetes and increased that of Firmicutes, however, there were no significant differences in post-intervention gut microbiota measurements between the WKBE and control. There were no significant effects on GI inflammation or symptoms related to constipation, or stool consistency or frequency. Our in vitro and gut model system analyses showed no effects of WKBE on alpha-amylase activity. Our findings suggest that WKBE may modulate the gut microbiota in healthy adults, however, the underlying mechanism is unlikely due to active site inhibition of alpha-amylase.

Background A “balanced, adequate, and varied diet” is recommended as the basis of nutritionally sound diet by the World Health Organisation and national public health agencies. Huel is a proprietary, on-the-go, powdered, plant based food, providing all 26 essential vitamins and minerals, protein, essential fats, carbohydrate, fibre, and phytonutrients. Objectives Assessing the effect of solely consuming Huel on micronutrient status, dietary intake and markers of health was achieved through a 4-week intervention of solely Huel powder. Methods Habitual energy intake was assessed through a one-week lead in period with healthy adult participants (aged 18 or over) logging their food intake, after which only Huel was consumed for 4 weeks. Blood samples and body composition was assessed before and after the lead in week as well the end of the intervention. Thirty participants were recruited with 20 (11 females, median age 31, range 22–44) completing the study, 19 sets of blood samples were collected. 22 blood markers were analysed along with weight, BMI, waist circumference, visceral adipose tissue (VAT), and body composition. All blood micronutrients, except for Thyroid Stimulating Hormone and choline were sent to Royal Victoria Infirmary NHS, Newcastle Laboratory (Newcastle upon Tyne, United Kingdom) for analysis. Results Fourteen of the parameters significantly changed over the course of the study with circulating haemoglobin, iron, vitamins B12 and D as well as selenium significantly increasing (p < 0.05). HbA1c, total and non-HDL cholesterol, vitamins A and E, potassium, BMI, VAT, and waist circumference all significantly decreased (p < 0.05) post intervention. Conclusion Although energy intake decreased during the intervention period, the adherence to recommended micronutrient intake, as quantified by the dietary Total Adherence Score, significantly increased which tallies with the preservation or improvement of micronutrient status. This study potentially demonstrates that consuming only Huel for 4 weeks does not negatively affect micronutrient status.

Background: Satiety in the stomach is often caused by distension and the satiating feeling is triggered through afferent vagal signals. Increasing or prolonging the distension of the stomach with a low-calorie agent would be beneficial in reducing the energy intake and potentially aid in the management of weight. The aim of this work was to quantify the rheological properties of an alginate formulation to induce satiety (AFIS) as it passes through a physiologically relevant model of human digestive tract. Methods: A physiologically relevant model of oral, gastric and small intestinal digestion was used to simulate in vivo conditions, including digestive capacity and physical forces. Samples were taken from the model and the rheological properties and viscosity of them assessed. This was repeated in the presence of a mixed meal. Results: The addition of the AFIS gelled strongly in the gastric phase of the model gut system and reformed the gel after shear stress disrupted the gel network. The inclusion of the formulation to induce satiety with a mixed meal to the model gut system increased the viscosity in the gastric phase to a greater extent than just the formulation alone. Conclusions: The forces generated by the stomach in vivo would be sufficient to eventually overcome the gelled formulation and with the repeated breakdown and additional gastric secretions would eventually allow passage into the small intestine. The synergistic increase in viscosity seen with the mixed meal and the formulation indicated an interaction between the formulation and the meal. The AFIS would potentially increase the retention time of gastric contents as well as gelling strongly. However, the forces generated by the stomach in vivo would eventually be sufficient to breakdown the formulation, and with the additional gastric secretion, allow it to pass into the small intestine, avoiding indefinite retention.

Pepsin is an aspartate protease that is generated from its proenzyme, pepsinogen by autocatalysis initiated by a fall in pH below 5. Human gastric juice contains eight isoenzymes of pepsin. The peptides released on conversion of pepsinogen to pepsin of which there are potentially five, have been shown to have antimicrobial activity against a wide range of bacteria including Escherichia coli, Pseudomonas and Staphylococcus which have also been shown to have biofilm formation inhibiting properties. The stability in response to changes in pH varies between pepsin and pepsinogen. Pepsinogen is stable up to pH 10, pepsin is only stable to pH just above 7.0 and is completely denatured at pH 8.0. Many diseases of the aerodigestive tract have been linked to reflux and the presence of pepsin. Therefore, the measurement of pepsin in tissue and lavages or in saliva or sputum, could be a good screening tool for the diagnosis of reflux related disease. However, there is no current consensus as to the best methods to measure it or the best time to sample it. For an effective pepsin ELISA, the following is required; a monoclonal/monospecific polyclonal antibody with a good lowest level of detection (LLOD) and sensitivity 1–25 ng/mL (depending on dilution) and an adequate supply of purified human pepsin as a standard for antibody-based assays. If possible, an activity assay for pepsin should also be used as the presence of pepsin protein does not indicate it is capable of damaging activity. Finally, if pepsin is associated with a disease large studies are required to confirm it with multiple samples. This review deals with several studies where pepsin quantitation is attempted, and their measurement techniques assessed.

This review discusses the utility and limitations of model gut systems in accurately modelling the mucosa of the digestive tract from both an anatomical and functional perspective, with a particular focus on the oesophagus and the upper digestive tract, and what this means for effective in vitro modelling of oesophageal pathology. Disorders of the oesophagus include heartburn, dysphagia, eosinophilic oesophagitis, achalasia, oesophageal spasm and gastroesophageal reflux disease. 3D in vitro models of the oesophagus, such as organotypic 3D culture and spheroid culture, have been shown to be effective tools for investigating oesophageal pathology. However, these models are not integrated with modelling of the upper digestive tract—presenting an opportunity for future development. Reflux of upper gastrointestinal contents is a major contributor to oesophageal pathologies like gastroesophageal reflux disease and Barratt’s oesophagus, and in vitro models are essential for understanding their mechanisms and developing solutions. The limitations of current model gut systems in modelling the mucosa is not only limited to the oesophagus. Integration of modelling of the mucus covered epithelia of the stomach and small intestine in to upper digestive tract models is limited and often not considered at all. In this paper we discuss mucus structure and function and current approaches to modelling of the mucus layer in isolation, and in integrated systems with cell culture systems and digestive models. We identify a need for relevant modelling of the viscoelastic properties of mucus and its protective function to allow complete integration in modelling. Addressing limitations of current in vitro models and integrating upper gastrointestinal models with those of the oesophagus presents an opportunity for better understanding oesophageal physiology and pathophysiology where reflux of digestive fluids is involved.

Two seaweeds; Ascophyllum nodosum and Fucus vesiculosus, were incorporated into bread at 0.5 and 2% and their effect on blood glucose in vivo and carbohydrate digestion in vitro were studied. In the five way randomised placebo controlled double blind pilot trial (n = 10) each volunteer consumed 100 g of available carbohydrate (from bread) and their blood glucose was measured over two hours. The breads were tested in a human digestion model and compared against control bread and control bread with the equivalent amount of seaweed. In the pilot human study the enriched breads did not cause any significant reductions in iAUC of blood glucose with average reductions of 0.1 ± 44.4%, 8.2 ± 19.3%, 1.0 ± 54.3% and 2.7 ± 31.9% for 0.5% F.vesiculosus, 0.5% A.nodosum, 2% F.vesiculosus, and 2% A.nodosum respectively. However, seaweed added alongside the control bread in vitro significantly reduced the level of carbohydrate digestion compared to the control bread. F.vesiculosus or A.nodosum can reduce carbohydrate digestion, however baking into bread reduces the effect.

Searchable abstracts of presentations at key conferences in obesity ISSN 2632-9808 (online)

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

The thick mucus layer of the gut provides a barrier to infiltration of the underlying epithelia by both the normal microbiota and enteric pathogens. Some members of the microbiota utilise mucin glycoproteins as a nutrient source, but a detailed understanding of the mechanisms used to breakdown these complex macromolecules is lacking. Here we describe the discovery and characterisation of endo-acting enzymes from prominent mucin-degrading bacteria that target the polyLacNAc structures within oligosaccharide side chains of both animal and human mucins. These O-glycanases are part of the large and diverse glycoside hydrolase 16 (GH16) family and are often lipoproteins, indicating that they are surface located and thus likely involved in the initial step in mucin breakdown. These data provide a significant advance in our knowledge of the mechanism of mucin breakdown by the normal microbiota. Furthermore, we also demonstrate the potential use of these enzymes as tools to explore changes in O-glycan structure in a number of intestinal disease states.

Lifestyle interventions and physical activity remain the cornerstone of obesity management, as pharmacological therapies (orlistat) are associated with gastrointestinal (GI) side effects. Combining orlistat with fibers can reduce side effects, improving compliance. Therefore, a fiber that inhibits lipase without side effects could help treat obesity. The aims of the present work were to assess whether alginate enriched bread could inhibit fat digestion, and assess the acceptability of alginate bread and its effect on GI wellbeing. A double-blind, randomised, controlled cross-over pilot study (NCT03350958) assessed the impact of an alginate bread meal on; lipid content in ileal effluent and circulating triacylglycerol levels. This was compared against the same meal with non-enriched (control) bread. GI wellbeing and acceptability of alginate bread was compared to control bread through daily wellbeing questionnaires and food diaries (NCT03477981). Control bread followed by alginate bread were consumed for two weeks respectively. Consumption of alginate bread reduced circulating triacylglycerol compared to control (2% reduction in AUC) and significantly increased lipid content in ileal effluent (3.8 g ± 1.6 after 210 min). There were no significant changes to GI wellbeing when comparing alginate bread to control bread. A significant increase in the feeling of fullness occurred with alginate bread compared to baseline and the first week of control bread consumption. This study showed that sustained consumption of alginate enriched bread does not alter GI wellbeing and can decrease lipolysis, increasing lipid leaving the small intestine. Further studies are required to demonstrate that reduced fat digestion through the action of alginate can reduce fat mass or body weight.

Starch provides a large proportion of the dietary energy consumed worldwide. The breakdown of dietary starch is driven by α‐amylase produced by the salivary glands and pancreatic acini and is completed by a range of brush‐border bound enzymes. This enzymatic digestion is aided by mechanical and secretory actions of the gastrointestinal tract. The absorption of the resultant glucose in the small intestine is primarily driven by two separate transport proteins − SGLT1 and GLUT2. The control of processes that govern starch digestion is complex and still not fully understood, although it appears that the human gut has the ability to sense both glucose and non‐sweet glucose oligomers. Recent work has also suggested that variations in the genes encoding for α‐amylase also appear to be associated with health outcomes. The authors consider the physiological factors that govern starch digestion and absorption, consider other dietary factors that may impact on this process and attempt to highlight the limitations in current knowledge to help focus future research needs in relation to starch digestion the upper gastrointestinal tract.

We formulated and characterised two alginate blends for the encapsulation of stevia extract (SE) via ionic gelation through an extrusion technique. Calcium chloride in SE and calcium chloride solutions were assessed as crosslinkers to overcome phenolic losses by diffusion and increase encapsulation efficiency (EE). Regardless of the blend, all stevia-loaded beads exhibited high EE (62.7-101.0%). The size of the beads decreased as EE increased. Fourier transform infrared analysis showed increased hydrogen bonding between SE and alginates, confirming the successful incorporation of SE within the matrix. Untargeted metabolomics profiling identified 479 free and encapsulated polyphenolic compounds. Flavonoids (catechin and luteolin equivalents) were predominant in SE whereas tyrosols and 5-pentadecylresorcinol equivalents were predominant in all bead formulations. Three-common discriminant compounds were exclusive to each blend and were inversely affected by the crosslinking conditions. Both alginate blends have been shown to be feasible as carrier systems of stevia extracts independent of crosslinking conditions.

Aim: Aim of the study was the development of ζ potential changing nanoparticles as gene delivery system for the cystic fibrosis transmembrane conductance regulator gene. Methods: Chitosan and carboxymethyl cellulose were modified with phosphotyrosine, a substrate for the brush border enzyme alkaline phosphatase. With these synthesized derivatives, different nanoparticle formulations, including the cystic fibrosis transmembrane conductance regulator gene were prepared by ionic gelation. Results: A change from negative to positive ζ potential after enzymatic cleavage could be observed. Transfection studies with HEK-293 and Caco-2 cells showed transfection rates comparable to Lipofectamine 2000. Transfection efficiencies were significantly decreased when phosphate cleavage and thus ζ potential change was inhibited by phosphatase inhibitor. Conclusion: The developed nanoparticles represent a promising gene delivery system.

"Dietary fibre" represents a wide spectrum of polysaccharides that escape digestion in the human gastrointestinal tract. The term has been widely associated with positive health outcomes, with the fibre content of food products being a potential basis for nutritional composition claims in many parts of the world. The current review aims to evaluate the current evidence from human trials on the impact of fibre-rich foods and isolated dietary fibre on body weight management. Evidence from observational studies consistently demonstrates that habitual increased intake of fruits, vegetables and whole grains is associated with lower body weight increase over time. Adherence to healthier dietary templates (including incorporation of higher amounts of plant-based foods) in intervention studies also tend to evidence greater weight loss than control diets. This further highlights the importance of fruits, vegetables and whole grains as the foundation of positive dietary habit. In contrast, randomised, controlled trials based on increase of fruit/vegetable or wholegrain food intake alone tend to show no impact on body weight or body fat outcomes, suggesting either that the length of previous studies is not long enough to observe measurable effects or that such dietary changes alone do not benefit these outcomes. While individual intervention studies suggest potential benefits of some fibre isolates on weight loss, there only appears to be reproducible evidence of efficacy for glucomannan. The limited amount of available evidence suggests a need for further, well-designed and appropriately targeted intervention studies in the future.

Drug delivery to the mucus covered mucosae is fraught with difficulties and many different approaches have been developed to permeate the mucus barrier. Generally by modifying the delivery system to avoid interaction with the mucus. These modifications are reviewed here in terms of efficacy and safety. These are particular problems for oral delivery the pharmaceutical industry's favoured route for drug administration. For effective delivery through the gastrointestinal tract a drug must pass through three barriers in sufficient amounts to yield a biological effect. These barriers are the digestive barrier in the lumen, the mucus barrier, and the epithelial barrier. Other approaches involve mucolytic agents added with or prior to the delivery system or agents regulating mucus production and are reviewed here. In terms of safety, a key property of a mucus modulating delivery system is that it must not damage the protective function of the mucus layer.

The effect of three Hebridean brown seaweeds on lipase activity was assessed using a turbidimetric lipase activity assay and an in vitro simulation of the upper digestive tract. The preparations of Ascophyllum nodosum, Fucus vesiculosus, and Pelvetia canaliculata were tested; whole seaweed homogenate, sodium carbonate extract, and ethanol extracts (pellet and supernatant were tested separately). All extracts showed significant inhibition of lipase, suggesting multiple bioactive agents, potentially including alginates, fucoidans, and polyphenols. Whole homogenate extract of F. vesiculosus was the most potent inhibitor of Lipase (IC50 = 0.119 mg mL-1), followed by ethanol supernatant (IC50 = 0.159 mg mL-1) while ethanol pellet and sodium carbonate extract showed relatively weaker inhibition (IC50 = 0.360 mg mL-1 and IC50 = 0.969 mg mL-1 respectively). For A. nodosum and P. canaliculata, strongest inhibition occurred with ethanol pellet (IC50 = 0.238 and 0.228 mg mL-1, respectively). These inhibitory effects were validated in a model gut system. The data presented herein suggests the use of seaweed as a potential weight management tool is deserving of further investigation.