New dynamic digestion model reactor that mimics gastrointestinal function

Intestinal organ chips for disease modelling and personalized medicine

Alterations in intestinal structure, mechanics and physiology underlie acute and chronic intestinal conditions, many of which are influenced by dysregulation of microbiome, peristalsis, stroma or immune responses. Studying human intestinal physiology or pathophysiology is difficult in preclinical animal models because their microbiomes and immune systems differ from those of humans. Although advances in organoid culture partially overcome this challenge, intestinal organoids still lack crucial features that are necessary to study functions central to intestinal health and disease, such as digestion or fluid flow, as well as contributions from long-term effects of living microbiome, peristalsis and immune cells. Here, we review developments in organ-on-a-chip (organ chip) microfluidic culture models of the human intestine that are lined by epithelial cells and interfaced with other tissues (such as stroma or endothelium), which can experience both fluid flow and peristalsis-like motions. Organ chips offer powerful ways to model intestinal physiology and disease states for various human populations and individual patients, and can be used to gain new insight into underlying molecular and biophysical mechanisms of disease. They can also be used as preclinical tools to discover new drugs and then validate their therapeutic efficacy and safety in the same human-relevant model.

Resistance model of an active capsule endoscope in a peristaltic intestine

In the past studies, the resistance of magnetically controlled capsules running through the small intestine has been modeled assuming that the small intestine was a circular tube with a constant diameter. Peristalsis is an important character of the human gastrointestinal system, and it would result in some changes in the diameter of the intestine, meaning that the existing resistance models would no longer be applicable. In this paper, based on the assumption that intestinal peristalsis is actually a sinusoidal wave, a resistance model of the capsule running in the peristaltic intestine is established, and then it is validated experimentally. The model provides a realistic foundation for the optimization and control of the magnetically controlled endoscopy.

New Horizons in Probiotics: Unraveling the Potential of Edible Microbial Polysaccharides through In Vitro Digestion Models

In vitro digestion models, as innovative assessment tools, possess advantages such as speed, high throughput, low cost, and high repeatability. They have been widely applied to the investigation of food digestion behavior and its potential impact on health. In recent years, research on edible polysaccharides in the field of intestinal health has been increasing. However, there is still a lack of systematic reviews on the application of microbial-derived edible polysaccharides in in vitro intestinal models. This review thoroughly discusses the limitations and challenges of static and dynamic in vitro digestion experiments, while providing an in-depth introduction to several typical in vitro digestion models. In light of this, we focus on the degradability of microbial polysaccharides and oligosaccharides, with a particular emphasis on edible microbial polysaccharides typically utilized in the food industry, such as xanthan gum and gellan gum, and their potential impacts on intestinal health. Through this review, a more comprehensive understanding of the latest developments in microbial polysaccharides, regarding probiotic delivery, immobilization, and probiotic potential, is expected, thus providing an expanded and deepened perspective for their application in functional foods.

Effects of In Vitro Fermentation of Polysialic Acid and Sialic Acid on Gut Microbial Community Composition and Metabolites in Healthy Humans

The influence of polysialic acid (PSA) and sialic acid (SA) on the gut microbial community composition and metabolites in healthy humans was investigated using a bionic gastrointestinal reactor. The results indicated that PSA and SA significantly changed the gut microbiota and metabolites to different degrees. PSA can increase the relative abundances of Faecalibacterium and Allisonella, whereas SA can increase those of Bifidobacterium and Megamonas. Both can significantly increase the content of short-chain fatty acids. The results of metabolome analysis showed that PSA can upregulate ergosterol peroxide and gallic acid and downregulate the harmful metabolite N-acetylputrescine. SA can upregulate 4-pyridoxic acid and lipoic acid. PSA and SA affect gut microbiota and metabolites in different ways and have positive effects on human health. These results will provide a reference for the further development of PSA- and SA-related functional foods and health products.

Development and analysis of a multi-module peristaltic simulator for gastrointestinal research

Many existing in vitro digestion systems do not accurately represent the peristaltic contractions of the gastrointestinal system; most of the systems that have physiologically-relevant peristaltic contractions have low throughput and can only test one sample at a time. A device has been developed that provides simulated peristaltic contractions for up to 12 digestion modules simultaneously using rollers of varying width to modulate the dynamics of the peristaltic motion. The force applied to a simulated food bolus varied from 2.61 ± 0.03 N to 4.51 ± 0.16 N (p < 0.05) depending on roller width. Video analysis showed that the degree of occlusion of the digestion module varied from 72.1 ± 0.4% to 84.6 ± 1.2% (p < 0.05). A multiphysics, computational fluid dynamics model was created to understand the fluid flow. The fluid flow was also examined experimentally using video analysis of tracer particles. The model-predicted maximum fluid velocity in the peristaltic simulator incorporating the thin rollers was 0.016 m/s, and the corresponding value measured using tracer particles was 0.015 m/s. The occlusion, pressure, and fluid velocity in the new peristaltic simulator fell within physiologically representative ranges. Although no in vitro device perfectly recreates the conditions of the gastrointestinal system, this novel device is a flexible platform for future gastrointestinal research and could allow for high-throughput screening of food materials for health-promoting properties under conditions representative of human gastrointestinal motility.

In Vitro Digestion and Fecal Fermentation of Low-Gluten Rice and Its Effect on the Gut Microbiota

Low-gluten rice is part of a special diet for chronic kidney disease patients, but its digestive mechanism in the gastrointestinal tract is unclear. In this study, low-gluten rice (LGR), common rice (CR), and rice starch (RS) were used as experimental samples, and their digestion and bacterial fermentation were simulated using an in vitro gastrointestinal reactor to investigate the mechanism of the effect of LGR on human health. The starch digestibility of CR was higher than that of LGR, with statistically significant differences. LGR has growth-promoting and metabolic effects on Akkermansia muciniphila. Among the beneficial metabolites, the concentration of short-chain fatty acids (SCFAs) from LGR reached 104.85 mmol/L, an increase of 44.94% (versus RS) and 25.33% (versus CR). Moreover, the concentration of lactic acid reached 18.19 mmol/L, an increase of 60.55% (versus RS) and 25.28% (versus CR). Among the harmful metabolites, the concentration of branched-chain fatty acids (BCFAs) in LGR was 0.29 mmol/L and the concentration of ammonia was 2.60 mmol/L, which was 79.31% and 16.15% lower than CR, respectively. A significant increase in the concentration of the beneficial intestinal bacteria Bacteroides and Bifidobacterium occurred from LGR. The 16s rDNA sequencing showed that the abundance of the Bacteroidetes and Firmicutes increased and the abundance of the Proteobacteria and Fusobacteria decreased. Thus, LGR has positive effects on digestion and gut microbiota structure and metabolism in humans.

Simulated Digestion and Fermentation In Vitro by Obese Human Gut Microbiota of Sulforaphane from Broccoli Seeds

BACKGROUND

sulforaphane is a kind of isothiocyanate, which is obtained by hydrolysis of glucosinolate by the unique myrosinase in plants. It has been proved to prevent the occurrence of many chronic diseases, such as obesity, diabetes and cancer.

OBJECTIVE

The impact of SFN on obese human gut flora, however, has not been established.

METHODS

In this research, SFN was isolated from broccoli seeds and then refined to achieve 95% purity. Next, an investigation was conducted into the digestion and fermentation processes of SFN.

RESULTS

The stability of the SFN in simulated saliva, gastric fluid, and intestinal juice provides evidence that it can reach the gut and be available for utilization by gut microflora. In vitro fermentation of SFN by gut microbes in obese patients results in alteration in constitution of microbiota and production of short chain fatty acids. As the result of SFN ingestion by human gut bacteria, the content of butyric and valeric acids increased 1.21- and 1.46-fold, respectively. In obese human guts, the relative abundances of the beneficial genera including Lactobacillus, Weissella, Leuconosto, Algiphilus and Faecalibacterium significantly increased, whilst the detrimental genera, such as Escherichia-Shigella, Klebsiella, Clostridium_sensu_stricto_1, Sutterella, Megamonas and Proteus drastically declined.

CONCLUSION

Taken together, these findings demonstrate that SFN can be used as a nutraceutical ingredient for obese patients and for improving human health.

The effects of high-fat foods on gut microbiota and small molecule intestinal gases: release kinetics and distribution in vitro colon model

Profiling intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. High-fat foods (HFF) can alter the gut microbiota and its metabolites, posing a potential health risk. However, little is known about the effects of HFF on intestinal gas distribution. Therefore, in this study, we used human fecal microorganisms as strains, an in vitro three-chamber colon model and an intestinal gas array sensor as tools. We performed in vitro fermentation using HFF as the fermentation substrate to reveal the effects of HFF on the kinetics of intestinal gas production and changes in the gut microbiota and its metabolites. We found that dietary fatty acids stimulated the production of H2S and volatile organic compounds in the colon, promoted Firmicutes abundance, and decreased Bacteroidetes abundance. These results highlight the potential role of HFF in altering the gut microbiota and intestinal gas, which can lead to health hazards.

•

High-fat foods (HFF) can alter the gut microbiota and its metabolites.

•

HFF stimulate H₂S and volatile organic compound production in the colon.

•

Specific intestinal gases can be used as disease markers.

Simulating human gastrointestinal motility in dynamic in vitro models

The application of dynamic in vitro gastrointestinal (GI) models has grown in popularity to understand the impact of food structure and composition on human health. Given that GI motility is integral to digestion and absorption, a predictive in vitro model should faithfully replicate the motility patterns and motor functions in vivo. In this review, typical characteristics of gastric and small intestinal motility in humans as well as the biomechanical and hydrodynamic events pertinent to gut motility are summarized. The simulation of GI motility in the presently existing dynamic in vitro models is discussed from an engineering perspective and categorized into hydraulic, piston/probe-driven, roller-driven, pneumatic, and other systems. Each system and its representative models are evaluated in terms of their motility patterns, the key hydrodynamic characteristics concerning gut motility, their performance in simulating the key physiological events, and their ability to establish in vitro-in vivo correlations. Practical Application: The review paper provided useful information in the design of dynamic GI models and the simulation of human gastric and small intestinal motility which are important for understanding food and health.

Evaluation of the Brewing Characteristics, Digestion Profiles, and Neuroprotective Effects of Two Typical Se-Enriched Green Teas

As a functional beverage, selenium (Se)-enriched green tea (Se-GT) has gained increasing popularity for its superior properties in promoting health. In this study, we compared the brewing characteristics, in vitro digestion profiles, and protective effects on neurotoxicity induced through the amyloid-beta (Aβ) peptide of two typical Se-GTs (Enshi Yulu (ESYL) and Ziyang Maojian (ZYMJ), representing the typical low-Se green tea and high-Se green tea, respectively). ESYL and ZYMJ showed similar chemical component leaching properties with the different brewing methods, and the optimized brewing conditions were 5 min, 90 °C, 50 mL/g, and first brewing. The antioxidant activities of the tea infusions had the strongest positive correlation with the tea polyphenols among all of the leaching substances. The tea infusions of ESYL and ZYMJ showed similar digestive behaviors, and the tea polyphenols in the tea infusions were almost totally degraded or transferred after 150 min of dynamic digestion. Studies conducted in a cell model of Alzheimer’s disease (AD) showed that the extract from the high-Se green tea was more effective for neuroprotection compared with the low-Se green tea. Overall, our results revealed the best brewing conditions and digestion behaviors of Se-GT and the great potential of Se-GT or Se-enriched green extract (Se-GTE) to be used as promising AD-preventive beverages or food ingredients.

Trends in lactose-derived bioactives: synthesis and purification

Lactose obtained from cheese whey is a low value commodity despite its great potential as raw material for the production of bioactive compounds. Among them, prebiotics stand out as valuable ingredients to be added to food matrices to build up functional foods, which currently represent the most active sector within the food industry. Functional foods market has been growing steadily in the recent decades along with the increasing awareness of the World population about healthy nutrition, and this is having a strong impact on lactose-derived bioactives. Most of them are produced by enzyme biocatalysis because of molecular precision and environmental sustainability considerations. The current status and outlook of the production of lactose-derived bioactive compounds is presented with special emphasis on downstream operations which are critical because of the rather modest lactose conversion and product yields that are attainable. Even though some of these products have already an established market, there are still several challenges referring to the need of developing better catalysts and more cost-effective downstream operations for delivering high quality products at affordable prices. This technological push is expected to broaden the spectrum of lactose-derived bioactive compounds to be produced at industrial scale in the near future.

Graphical abstract

In vitro models to evaluate ingestible devices: Present status and current trends

Orally ingestible medical devices offer significant opportunity in the diagnosis and treatment of gastrointestinal conditions. Their development necessitates the use of models that simulate the gastrointestinal environment on both a macro and micro scale. An evolution in scientific technology has enabled a wide range of in vitro, ex vivo and in vivo models to be developed that replicate the gastrointestinal tract. This review describes the landscape of the existing range of in vitro tools that are available to characterize ingestible devices. Models are presented with details on their benefits and limitations with regards to the evaluation of ingestible devices and examples of their use in the evaluation of such devices is presented where available. The multitude of models available provides a suite of tools that can be used in the evaluation of ingestible devices that should be selected on the functionality of the device and the mechanism of its function.

Effect of an Antibacterial Polysaccharide Produced by Chaetomium globosum CGMCC 6882 on the Gut Microbiota of Mice

Previously, a polysaccharide produced by Chaetomiumglobosum CGMCC 6882 was found to have antibacterial activity, but its toxic effects on body health and gut microbiota were concealed. Recent results showed that this polysaccharide was safe to Caco-2 cells and mice, while it reduced the body weight gain of mice from 10.5 ± 1.21 g to 8.4 ± 1.17 g after 28 days administration. Acetate, propionate, butyrate and total short-chain fatty acids concentrations increased from 23.85 ± 1.37 μmol/g, 10.23 ± 0.78 μmol/g, 7.15 ± 0.35 μmol/g and 41.23 ± 0.86 μmol/g to 42.77 ± 1.29 μmol/g, 20.03 ± 1.44 μmol/g, 12.06 ± 0.51 μmol/g and 74.86 ± 2.07 μmol/g, respectively. Furthermore, this polysaccharide enriched the abundance of gut microbiota and the Firmicutes/Bacteroidetes ratio was increased from 0.5172 to 0.7238. Overall, this study provides good guidance for the promising application of polysaccharides as preservatives in foods and in other fields in the future.

In vitro digestion and fecal fermentation of highly resistant starch rice and its effect on the gut microbiota

Highly resistant starch rice (HRSR) is of particular interest in terms of its capacity to deliver short-chain fatty acids (SCFAs) to the colon in the prevention of diabetes mellitus and obesity. In this study, HRSR was processed into cooked rice, rice milk, rice cake, and rice popcorn, and the in vitro digestion and fermentation processes were monitored. The results showed that the starch digestibility of the four samples conformed to a first-order two-phase equation, and the resistant starch content of rice cake was the highest (11.98%). Compared with inulin, rice cake had a slower fermentation rate, and the butyrate concentration increased by 67.85%. The abundances of Prevotellaceae, which promotes the synthesis of SCFAs, and anti-inflammatory Faecalibacterium increased. The abundances of Proteobacteria and Megamonas, markers of gut microbiota imbalance, decreased. The results might facilitate the design and production of functional food products for type 2 diabetic and obese patients and improving colonic health.

Study of growth, metabolism, and morphology of Akkermansia muciniphila with an in vitro advanced bionic intestinal reactor

Background

As a kind of potential probiotic, Akkermansia muciniphila abundance in human body is directly causally related to obesity, diabetes, inflammation and abnormal metabolism. In this study, A. muciniphila dynamic cultures using five different media were implemented in an in vitro bionic intestinal reactor for the first time instead of the traditional static culture using brain heart infusion broth (BHI) or BHI + porcine mucin (BPM).

Results

The biomass under dynamic culture using BPM reached 1.92 g/L, which improved 44.36% compared with the value under static culture using BPM. The biomass under dynamic culture using human mucin (HM) further increased to the highest level of 2.89 g/L. Under dynamic culture using porcine mucin (PM) and HM, the main metabolites were short-chain fatty acids (acetic acid and butyric acid), while using other media, a considerable amount of branched-chain fatty acids (isobutyric and isovaleric acids) were produced. Under dynamic culture Using HM, the cell diameters reached 999 nm, and the outer membrane protein concentration reached the highest level of 26.26 μg/mg.

Conclusions

This study provided a preliminary theoretical basis for the development of A. muciniphila as the next generation probiotic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02111-7.

Determining the glycaemic responses of foods: conventional and emerging approaches

A low-glycaemic diet is crucial for those with diabetes and cardiovascular diseases. Information on the glycaemic index (GI) of different ingredients can help in designing novel food products for such target groups. This is because of the intricate dependency of material source, composition, food structure and processing conditions, among other factors, on the glycaemic responses. Different approaches have been used to predict the GI of foods, and certain discrepancies exist because of factors such as inter-individual variation among human subjects. Besides other aspects, it is important to understand the mechanism of food digestion because an approach to predict GI must essentially mimic the complex processes in the human gastrointestinal tract. The focus of this work is to review the advances in various approaches for predicting the glycaemic responses to foods. This has been carried out by detailing conventional approaches, their merits and limitations, and the need to focus on emerging approaches. Given that no single approach can be generalised to all applications, the review emphasises the scope of deriving insights for improvements in methodologies. Reviewing the conventional and emerging approaches for the determination of GI in foods, this detailed work is intended to serve as a state-of-the-art resource for nutritionists who work on developing low-GI foods.

New insights into in vivo gastroduodenal digestion of oil-in-water emulsions: gastric stability and in vitro digestion modeling

In this paper, effect of emulsion stability on gastroduodenal emptying/secretion was reviewed and differentiated. Moreover, novel perspectives on physiology of gastric lumen, duodenum, and gall bladder were achieved using mathematical models, being useful for designing artificial digestive systems. In this regard, numerical data for dynamic gastric emptying/secretion were offered for gastric-stable and gastric-unstable emulsion intakes. It was shown that alterations in human gastric and duodenal volume follow, respectively, linear and sinusoidal curves, with high correlation coefficients (r² > 0.93). For both emulsions, about 30-40 mL ingesta discharged rapidly from stomach upon ingestion; However, further gastric emptying was regulated for the rest of digestion period, so that 0.1 mL/min oil was passing through duodenum. Intragastric evacuation of both emulsions started with a lag phase during which stomach stored secretions incrementally by slow gastric discharge. Lag phase ended with fat layering, when emptying considerably enhanced. This reduction was gradual for stable emulsion while unstable emulsion experienced a rapid emptying before slow declining trend. Along with initial gastric emptying, 87% of gallbladder content discharged into duodenum, prolonged up to the gradual reduction phase of stomach. Supplementary investigations are needed to quantify gastroduodenal secretions, particularly pepsin and pancreas in response to emulsion ingesta.