On designing biomimic in vitro human and animal digestion track models: ideas, current and future devices

In vitro release and bioaccessibility of oral solid preparations in a dynamic gastrointestinal system simulating fasted and fed states: A case study of metformin hydrochloride tablets

Food and formulation characteristics are crucial factors affecting the gastrointestinal release and absorption kinetics of oral solid preparations. In the present study, the dynamic continuous release and bioaccessibility of metformin hydrochloride immediate-release (IR) and sustained-release (SR) tablets were investigated in the dynamic human stomach-intestine (DHSI-IV) system simulating fasted and fed states in healthy adults. Both tablet formulations (particularly IR tablet) exhibited a postponed release in the fed state compared to the fasted state. Correspondingly, the bioaccessible fraction of metformin from IR tablets in the presence of high-fat meal was significantly reduced to 76.2 % of the fasted state. However, the in vitro bioaccessibility was less impaired by food for SR tablets with a fed/fasted ratio of 95.5 %. A convolution-based approach was used to convert in vitro bioaccessibility results to plasma concentration data. The predicted plasma concentration curve showed good agreement with human data in terms of pharmacokinetic (PK) parameters. In the fasted state, the predicted Cmax, Tmax and AUC0-24h of IR tablets were 943.9 ± 25.7 ng/mL, 2.0 ± 0.4 h and 7090.7 ± 112.0 ng.h/mL, respectively, mirroring values observed in healthy subjects. Overall, the DHSI-IV system has demonstrated potential to assess and predict the impact of meal intake on the in vivo release and absorption behaviors of oral solid preparations.

Intestinal retentive systems - recent advances and emerging approaches

Intestinal retentive devices (IRDs) are devices designed to anchor within the lumen of the intestines for long-term residence in the gastrointestinal tract. IRDs can enable impactful medical device technologies including sustained oral drug delivery systems, indwelling sensors, or real-time diagnostics. The design and testing of IRDs present a myriad of challenges, including precise deployment of the device at desired intestinal locations, secure anchoring within the gastrointestinal tract to allow for natural function, and safe removal of the IRD at user-defined times. Advancing the state-of-the-art of IRD is an interdisciplinary effort that requires innovations such as new materials, novel anchoring mechanisms, and medical device design with consistent input from clinical practitioners and end-users. This perspective briefly reviews the current state-of-the-art for IRDs and charts a path forward to inform the design of future concepts. Specifically, this article will highlight materials, retention mechanisms, and test beds to measure the efficacy of IRDs and their mechanisms. Finally, potential synergies between IRD and other medical device technologies are presented to identify future opportunities.

Exploring in vitro gastrointestinal digestion of myofibrillar proteins at different heating temperatures

The effects of different heating temperatures (40-115 °C) on the structure, oxidation, and digestibility of beef myofibrillar protein were investigated. Reductions in the number of sulfhydryl groups were observed, together with gradual increases in the number of carbonyl groups, indicating oxidation of the protein by the increased temperatures. At temperatures between 40 °C and 85 °C, β-sheets were converted to α-helices, and increased surface hydrophobicity showed that the protein expanded as the temperature approached 85 °C. These changes were reversed at temperatures over 85 °C, indicative of aggregation induced by thermal oxidation. Between 40 °C and 85 °C, the digestibility of the myofibrillar protein was increased, reaching a maximum of 59.5 % at 85 °C, after which it began to decrease. These results indicated that moderate heating and oxidation-induced protein expansion were beneficial to digestion while protein aggregation resulting from excessive heating is not conducive to digestion.

Relations between in vitro starch digestibility of commercial baked products and their macronutrients

BACKGROUND

Baked products such as biscuits and breads are the staple foods for a large population, with the starch digestion rate having a crucial effect on human health. Currently, there is a lack of information on general starch digestibility in commercial baked products and its correlation with macronutrient content.

RESULTS

The present study investigated the starch digestibility of 35 commercial baked products, ranging from low to high moisture contents. Biscuits generally had a slower starch digestion rate than mini-breads, whereas breads including whole wheat bread had the fastest digestion rate. Additionally, starch digestibility was negatively correlated with the calorie (R²  = 0.71) and fat content (R²  = 0.56) in per serving size, possibly because of the formation of amylose-lipid complex.

CONCLUSION

The present study provides a database for the in vitro starch digestibility of a large number of food items, which gives general indications on the performance of starch components of commercial products in the human gastrointestinal tract. © 2022 Society of Chemical Industry.

A rethinking of collagen as tough biomaterials in meat packaging: assembly from native to synthetic

Due to the high moisture-associated typical rheology and the changeable and harsh processing conditions in the production process, packaging materials for meat products have higher requirements including a sufficient mechanical strength and proper ductility. Collagen, a highly conserved structural protein consisting of a triple helix of Gly-X-Y repeats, has been proved to be suitable packaging material for meat products. The treated animal digestive tract (i.e. the casing) is the perfect natural packaging material for wrapping meat into sausage. Its thin walls, strong toughness and impact resistance make it the oldest and best edible meat packaging. Collagen casing is another wisdom of meat packaging, which is made by collagen fibers from hide skin, presenting a rapid growth in casing market. To strengthen mechanical strength and barrier behaviors of collagen-based packaging materials, different physical, chemical, and biological cross-linking methods are springing up exuberantly, as well as a variety of reinforcement approaches including nanotechnology. In addition, the rapid development of biomimetic technology also provides a good research idea and means for the promotion of collagen's assembly and relevant mechanical properties. This review can offer some reference on fundamental theory and practical application of collagenous materials in meat products.

Effects of Marine Bioactive Compounds on Gut Ecology Based on In Vitro Digestion and Colonic Fermentation Models

Digestion and the absorption of food compounds are necessary steps before nutrients can exert a role in human health. The absorption and utilization of nutrients in the diet is an extremely complex dynamic process. Accurately grasping the digestion and absorption mechanisms of different nutrients or bioactive compounds can provide a better understanding regarding the relationship between health and nutrition. Several in vitro models for simulating human gastrointestinal digestion and colonic fermentation have been established to obtain more accurate data for further understanding of the metabolism of dietary components. Marine media is rich in a wide variety of nutrients that are essential for humans and is gaining increased attention as a research topic. This review summarizes some of the most explored in vitro digestion and colonic fermentation models. It also summarizes the research progress on the digestion and absorption of nutrients and bioactive compounds from marine substrates when subjected to these in vitro models. Additionally, an overview of the changes imparted by the digestion process on these bioactive compounds is provided, in order to support those marine resources that can be utilized for developing new healthy foods.

Quantitative visualization study on the physical movement and gastric emptying of diced carrot particle in a transparent rat stomach-duodenum model

In this study, a transparent soft-elastic silicone rat stomach model was prepared to visualize the gastric movement and emptying of one individual diced carrot in a dynamic in vitro rat stomach system. The influences of the viscosity of solution medium, the pattern of gastric peristalsis and the extraction rate of the emptying pump on the location and gastric residence time of the carrot particle were examined. A proper medium viscosity could promote the emptying of the carrot particle. Compared to the combined actions of plate and roller, gastric residence time of the carrot particle was reduced from 32.3 to 19.8 min under the single plate compression. This time was also shortened from 34.8 to 12.3 min when the extraction rate of emptying pump was changed from 100 mL/min to 400 mL/min. Knowledge gained from this work is unique and may provide new insights for optimizing biomimic gastrointestinal models.

Possible regulation of liver glycogen structure through the gut-liver axis by resistant starch: a review

Liver glycogen α particles in diabetic patients are fragile relative to those in healthy individuals, and restoring these fragile glycogen particles to a normal state shows potential to contribute to the remission of diabetes. Resistant starch (RS) is beneficial for diabetes management through its interactions with the gut microbiota. However, its effects on glycogen fragility are not fully understood. This review aims to summarize the recent understanding of the interactions between RS and the human gut microbiota and the possible connections to liver glycogen biosynthesis to elucidate its role in the development of glycogen fragility. RS might regulate glycogen fragility in diabetes by modulating the postprandial glycemic response and glycogen biosynthesis pathways. Before RS can be applied to repair fragile glycogen, more work should be done to better understand in vivo RS structures and identify the factor binding glycogen β particles together. This review contains important information on the connections between glycogen fragility and RS-gut microbiota interactions, which could help to better understand the health benefits of RS consumption.

Effect of heat treatment on the digestion behavior of pea and rice protein dispersions and their blends, studied using the semi-dynamic INFOGEST digestion method

In the present study, the structuring and breakdown of a 5% protein dispersion prepared with commercial fractions of pea and rice isolates (PPI and RPI, respectively) were monitored by in vitro digestion. These proteins were blended in a 2 : 1 ratio of pea and rice, respectively, as this would deliver a high amino acid score. The effect of heating at 90 °C for 15 min on the digestion behavior was evaluated not only for the blend, but also for the respective protein isolate fractions, using the INFOGEST international consensus, semi-dynamic in vitro gastric model. Digesta were characterized by gel electrophoresis, light scattering, confocal laser scanning microscopy and size exclusion HPLC. Heating increased the solubility of PPI from 15.7% to 26.6% at pH 7.4. RPI showed low solubility (a maximum of 2.6% at pH 2), regardless of the treatment. Confocal microscopy observations evidenced major differences in the aggregates formed during digestion, with larger aggregates for heated PPI. While the unheated pea protein dispersions precipitated near the isoelectric pH, the heated counterpart formed macro-aggregates under the same conditions. In the case of RPI, there were no differences in structuring behaviour between unheated and heat treated reconstituted powder, due to their low solubility. Rice prolamins showed resistance to hydrolysis by pepsin and pancreatic enzymes. In the heated blend, macro-aggregates formed, but with a smaller size compared to heated pea protein alone, suggesting that pea protein aggregation was hindered by the presence of rice proteins. These results demonstrate how the composition of protein isolates can affect their in vitro digestion. However, pre-treatment of plant protein blends, such as heating, can modulate the rate and mechanism of digestion.

Achieving realistic gastric emptying curve in an advanced dynamic in vitro human digestion system: experiences with cheese-a difficult to empty material

Nowadays, in vitro digestion models have received growing interest in recent years to track the digestive fate of foods in the gastrointestinal tract. A major challenge in the development of more physiologically relevant in vitro gastric models is to simulate realistic gastric emptying. In this study, an advanced dynamic in vitro human gastric system was investigated for its potential in achieving the above. The mechanisms for controlling the gastric emptying rate by modulations of the peristaltic moving distance, the pylorus opening size/frequency, and the stomach tilting angle in relation to time are illustrated. With solid cheese, a difficult food material for emptying, different combinations of the operational parameters of the stomach system were evaluated. The system was steered to attain consistent gastric emptying curve with the theoretical data by optimizing operational parameters. By fitting the gastric retention data with a power-exponential model, which is a common approach for describing gastric emptying, the total meal achieved an average emptying half-time (t1/2) of 84.5 min and a curve shape coefficient (β) of 1.69, similar to the theoretical data reported in the literature, where the values of t1/2 and β were 85 min and 1.8, respectively (p > 0.05). Furthermore, the mean median particle size was significantly decreased from the initial 2.80 mm (cheese cubes) to the final 1.35 mm (p < 0.05). There are few particles greater than 2 mm observed in the emptied cheese digesta throughout the digestion process. These suggest the powerful gastric grinding and sieving capacity exhibited by the in vitro system. The current study demonstrates that a well-considered in vitro system can offer a reasonable approach for tracking the structural and physicochemical changes of foods during digestion in the stomach, which is practically meaningful.

In vitro gastrointestinal digestion and fermentation models and their applications in food carbohydrates

Food nutrients plays a crucial role in human health, especially in gastrointestinal (GI) health. The effect of food nutrients on human health mainly depends on the digestion and fermentation process in the GI tract. In vitro GI digestion and fermentation models had the advantages of reproducibility, simplicity, universality, and could integrally simulate the in vivo conditions to mimic oral, gastric, small intestinal and large intestinal digestive processes. They could not only predict the relationship among material composition, structure and digestive characteristics, but also evaluate the bioavailability of material components and the impact of digestive metabolites on GI health. This review systematicly summarized the current state of the in vitro simulation models, and made detailed descriptions for their applications, advantages and disadvantages, and specially their applications in food carbohydrates. In addition, it also provided the suggestions for the improvement of in vitro models and firstly proposed to establish a set of standardized methods of in vitro dynamic digestion and fermentation conditions for food carbohydrates, which were in order to further evaluate more effects of the nutrients on human health in future.