Effect of meal viscosity and nutrients on satiety, intragastric dilution, and emptying assessed by MRI

A physiologically-based digital twin for alcohol consumption-predicting real-life drinking responses and long-term plasma PEth

Alcohol consumption is associated with a wide variety of preventable health complications and is a major risk factor for all-cause mortality in the age group 15-47 years. To reduce dangerous drinking behavior, eHealth applications have shown promise. A particularly interesting potential lies in the combination of eHealth apps with mathematical models. However, existing mathematical models do not consider real-life situations, such as combined intake of meals and beverages, and do not connect drinking to clinical markers, such as phosphatidylethanol (PEth). Herein, we present such a model which can simulate real-life situations and connect drinking to long-term markers. The new model can accurately describe both estimation data according to a χ2 -test (187.0 < Tχ2 = 226.4) and independent validation data (70.8 < Tχ2 = 93.5). The model can also be personalized using anthropometric data from a specific individual and can thus be used as a physiologically-based digital twin. This twin is also able to connect short-term consumption of alcohol to the long-term dynamics of PEth levels in the blood, a clinical biomarker of alcohol consumption. Here we illustrate how connecting short-term consumption to long-term markers allows for a new way to determine patient alcohol consumption from measured PEth levels. An additional use case of the twin could include the combined evaluation of patient-reported AUDIT forms and measured PEth levels. Finally, we integrated the new model into an eHealth application, which could help guide individual users or clinicians to help reduce dangerous drinking.

Understanding age-related changes: exploring the interplay of protein intake, physical activity and appetite in the ageing population

Globally, we are currently facing a rapid demographic shift leading to an increase in the proportion of older adults within the population. This raises concerns about the potential increase in age-related diseases and their impact on our ability to provide adequate health and end-of-life care. To apply appropriate interventions, understanding the changes that happen with ageing becomes essential. Ageing is often accompanied by a decrease in appetite and physical activity, which may lead to malnutrition, resulting in decreased muscle mass, physical capabilities and independence. To preserve muscle mass, older adults are advised to increase protein intake and physical activity. However, protein's high satiating effect may cause reduced energy intake. Physical activity is also advised to maintain or enhance older adult's appetite. This review paper aims to discuss appetite-related changes that occur with ageing and their consequences. In particular, it will focus on investigating the relationship between protein intake and physical activity and their impact on appetite and energy intake in the ageing population. Recent studies suggest that physical activity might contribute to maintaining or enhancing appetite in older adults. Nevertheless, establishing a definitive consensus on the satiating effect of protein in ageing remains a work in progress, despite some promising results in the existing literature.

Effect of Food Viscosity on Drug Dissolution

PURPOSE

The purpose of the present study was to investigate the effect of food viscosity on the dissolution rate of a drug. There are two types of viscosity, macroviscosity and microviscosity. Macroviscosity affects the diffusion layer thickness, whereas microviscosity affects the molecular diffusion coefficient. The mass transfer coefficient (kc) in the intrinsic dissolution rate (IDR) depends on the viscosity (η) as kc ∝ ηa (a is an exponent on η). In theory, for rotating flow over a disk, if a thickener increases only macroviscosity, a = -1/6, and if it increases both macroviscosity and microviscosity equally, a = -7/6.

METHOD

Benzocaine was used as a model drug. Hydroxypropyl cellulose (HPC) and methylcellulose (MC) were employed as control thickeners that increase only macroviscosity. Sucrose was employed as a control thickener for both macroviscosity and microviscosity. The FDA breakfast homogenate (BFH) was diluted with distilled water or 1 mM HCl with/without pepsin digestion. The IDR value was measured by the paddle-over-disk method.

RESULTS

The η value of 30% BFH distilled water was 209 mPa∙s, about 300 times higher than distilled water. It was further increased by HCl (430 mPa∙s), and reduced by pepsin digestion (35 mPa∙s). The kc value was little affected by BFH (a = 0.00 to -0.09), slightly less than those in HPC (a = -0.19) and MC (a = -0.21). Sucrose decreased the kc value more significantly (a = -0.70).

CONCLUSION

The IDR and kc values of benzocaine were little affected by BFH, suggesting that BFH increased only macroviscosity.

In silico modelling of the effect of pyloric intervention procedures on gastric flow and emptying in a stomach with gastroparesis

Pyloric interventions are surgical procedures employed to increase the gastric emptying rate in gastroparesis patients. In this study, we use an in silico model to investigate the consequences of pyloric intervention on gastric flow and emptying for two phenotypes of gastroparesis: antral hypomotility and decreased gastric tone. The transpyloric pressure gradient predicted by the in silico model, based on viscous fluid flow equations, is compared against in vivo measurements. Both phenotypes exhibit a similar pre-procedural emptying rate reduction, but after pyloric surgery, antral hypomotility case with preserved gastric tone shows significant improvements in emptying rates, up to 131%, accompanied by bile reflux from the duodenum into the stomach. Conversely, severely reduced gastric tone cases exhibited a post-procedural reduction in the net emptying rate due to the relatively larger bile reflux. In cases with a combination of antral hypomotility and reduced gastric tone, post-procedural improvements were observed only when both conditions were mild. Our findings highlight the pivotal role of the relative increase in pyloric orifice diameter in determining post-operative emptying rates. The study suggests a possible explanation for the selective response of patients toward these procedures and underscores the potential of in silico modelling to generate valuable insights to inform gastric surgery.

SNAPIG: a model to study nutrient digestion and absorption kinetics in growing pigs based on diet and ingredient properties

Current feed formulation and evaluation practices rely on static values for the nutritional value of feed ingredients and assume additivity. Hereby, the complex interplay among nutrients in the diet and the highly dynamic digestive processes are ignored. Nutrient digestion kinetics and diet × animal interactions should be acknowledged to improve future predictions of the nutritional value of complex diets. Therefore, an in silico nutrient-based mechanistic digestion model for growing pigs was developed: "SNAPIG" (Simulating Nutrient digestion and Absorption kinetics in PIGs). Aiming to predict the rate and extent of nutrient absorption from diets varying in ingredient composition and physicochemical properties, the model represents digestion kinetics of ingested protein, starch, fat, and non-starch polysaccharides, through passage, hydrolysis, absorption, and endogenous secretions of nutrients along the stomach, proximal small intestine, distal small intestine, and caecum + colon. Input variables are nutrient intake and the physicochemical properties (i.e. solubility, and rate and extent of degradability). Data on the rate and extent of starch and protein hydrolysis of different ingredients per digestive segment were derived from in vitro assays. Passage of digesta from the stomach was modelled as a function of feed intake level, dietary nutrient solubility and diet viscosity. Model evaluation included testing against independent data from in vivo studies on nutrient appearance in (portal) blood of growing pigs. When simulating diets varying in physicochemical properties and nutrient source, SNAPIG can explain variation in glucose absorption kinetics (postprandial time of peak, TOP: 20-100 min observed vs 25-98 min predicted), and predict variation in the extent of ileal protein and fat digestion (root mean square prediction errors (RMSPE) = 12 and 16%, disturbance error = 12 and 86%, and concordance correlation coefficient = 0.34 and 0.27). For amino acid absorption, the observed variation in postprandial TOP (61 ± 11 min) was poorly predicted despite accurate mean predictions (58 ± 34 min). Recalibrating protein digestion and amino acid absorption kinetics require data on net-portal nutrient appearance, combined with observations on digestion kinetics, in pigs fed diets varying in ingredient composition. Currently, SNAPIG can be used to forecast the time and extent of nutrient digestion and absorption when simulating diets varying in ingredient and nutrient composition. It enhances our quantitative understanding of nutrient digestion kinetics and identifies knowledge gaps in this field of research. Already useful as research tool, SNAPIG can be coupled with a postabsorptive metabolism model to predict the effects of dietary and feeding-strategies on the pig's growth response.

Reducing starch digestibility of white rice by structuring with hydrocolloids

Controlling starch digestion in high glycaemic index staple foods such as white rice is of interest as it has been associated with reduced risk for conditions such as obesity and type-2 diabetes mellitus. Addition of hydrocolloids has been proposed to reduce the rate of post-prandial glucose by controlling the rate of starch hydrolysis. In this work, the potential of a range of hydrocolloids to modify starch digestibility when added (at 1 % maximum concentration) during cooking of white rice was first investigated. Low acyl gellan gum (LAG) showed the highest potential (in-vitro estimated Glycaemic Index reduced by about 20 %, from 94 in the control to 78 in the LAG rice) and was investigated further. While the grains of rice control and rice with LAG appeared similar, SEM images revealed a gel-like layer (a few micrometers in thickness) on the surface of the treated samples. Addition of LAG appeared to also have an effect on the breakdown of a simulated cm-sized bolus. During gastric digestion, bolus breakdown of the rice control was completed after 30 min, while the rice LAG bolus appeared intact after 1 h of observation. This was attributed to strengthening of the LAG gel in the acidic environment of the stomach. During intestinal digestion, rice samples containing 1 % LAG appeared to be less susceptible to breakdown when seen under a microscope and in environmental SEM, while they showed larger rice particle aggregates, compared to rice control. Overall, LAG showed potential to control starch digestion kinetics of white rice with a mechanism that may involve formation of a protective layer on the rice grains (um) that reduces bolus break down (cm) and enzymatic hydrolysis (nm). Outcomes of this work will be used to identify conditions for further relevant in-vitro and in-vivo investigations.

A comparative, randomised MRI study of the physiological and appetitive responses to gelling (alginate) and non-gelling nasogastric tube feeds in healthy men

Inclusion in nasogastric tube feeds (NGTF) of acid-sensitive, seaweed-derived alginate, expected to form a reversible gel in the stomach, may create a more normal intragastric state and modified gastrointestinal responses. This may ameliorate NGTF-associated risk of diarrhoea, upper gastrointestinal symptoms and appetite suppression. In a randomised, crossover, comparison study, undertaken in twelve healthy males, an alginate-containing feed (F + ALG) or one that was alginate-free (F-ALG) (300 ml) was given over 1 h with a 7-14-d washout period between treatments. Baseline and for 4-h post-feed initiation, MRI measurements were made to establish small bowel water content (SBWC), gastric contents volume (GCV) and appearance, and superior mesenteric artery blood flux. Blood glucose and gut peptides were measured. Subjective appetite and upper gastrointestinal symptoms scores were obtained. Ad libitum pasta consumption 3-h post-feeding was measured. F + ALG exhibited a gastric appearance consistent with gelling surrounded by a freely mobile water halo. Significant main effects of feed were seen for SBWC (P = 0·03) and peptide YY (PYY) (P = 0·004) which were attributed to generally higher values for SBWC with F + ALG (max difference between adjusted means 72 ml at 210 min) and generally lower values for PYY with F + ALG. GCV showed a faster reduction with F + ALG, less between-participant variation and a feed-by-time interaction (P = 0·04). Feed-by-time interactions were also seen with glucagon-like-peptide 1 (GLP-1) (P = 0·02) and glucose-dependent insulinotropic polypeptide (GIP) (P = 0·002), both showing a blunted response with F + ALG. Apparent intragastric gelling with F + ALG and subsequent differences in gastrointestinal and endocrine responses have been demonstrated between an alginate-containing and alginate-free feed.

Biomimetic superabsorbent hydrogel acts as a gut protective dynamic exoskeleton improving metabolic parameters and expanding A. muciniphila

The rising prevalence of obesity and metabolic disorders worldwide highlights the urgent need to find new long-term and clinically meaningful weight-loss therapies. Here, we evaluate the therapeutic potential and the mechanism of action of a biomimetic cellulose-based oral superabsorbent hydrogel (OSH). Treatment with OSH exerts effects on intestinal tissue and gut microbiota composition, functioning like a protective dynamic exoskeleton. It protects from gut barrier permeability disruption and induces rapid and consistent changes in the gut microbiota composition, specifically fostering Akkermansia muciniphila expansion. The mechanobiological, physical, and chemical structures of the gel are required for A. muciniphila growth. OSH treatment induces weight loss and reduces fat accumulation, in both preventative and therapeutic settings. OSH usage also prevents liver steatosis, immune infiltration, and fibrosis, limiting the progression of non-alcoholic fatty liver disease. Our work shows the potential of using OSH as a non-systemic mechanobiological approach to treat metabolic syndrome and its comorbidities.

Further evidence for sensitivity to energy density and a two-component model of meal size: Analysis of meal calorie intakes in Argentina and Malaysia

Previously, we demonstrated a non-linear association between meal caloric intake and meal energy density (ED, kcal/g) in data from a controlled trial in the US and from free-living participants in the UK [1]. In both datasets, meal caloric intake increased with ED in lower energy-dense meals (below ∼1.75 kcal/g) and decreased in higher energy-dense meals (above ∼1.75 kcal/g). In the current study, we sought to explore whether this pattern extends to data from free-living participants in Argentina (N = 2738 meals) and Malaysia (N = 4658 meals). Again, a significant breakpoint was found in both the Argentinean (2.04 kcal/g (SE = 0.06)) and Malaysian (2.17 kcal/g (SE = 0.06)) datasets with mean centered meal caloric intake increasing with ED below the breakpoint and decreasing above the breakpoint. These results lend further support for our two-component theoretical model of meal size (g) in which a volume signal is dominant in lower energy-dense meals and a calorie-content signal is dominant in higher energy-dense meals. Together, our research adds to evidence supporting human sensitivity to calories and exposes a complexity in the correspondence between meal energy content and meal size in everyday (non-manipulated) meals. Further research is needed to provide causal evidence for this sensitivity and whether individual variation impacts meal size and energy balance.

Plasticity of gastrointestinal vagal afferents in terms of feeding-related physiology and pathophysiology

Gastrointestinal vagal afferents play an important role in communicating food related information from the gut to the brain. This information initiates vago-vagal reflexes essential for gut functions, including gut motility and secretions. These afferents also play a role in energy homeostasis, signalling the arrival, amount and nutrient composition of a meal to the central nervous system where it is processed ultimately leading to termination of a meal. Vagal afferent responses to food related stimuli demonstrate a high degree of plasticity, responding to short term changes in nutritional demand, such as the fluctuations that occur across a 24-hr or in response to a fast, as well as long term changes in energy demand, such as occurs during pregnancy. This plasticity is disrupted in disease states, such as obesity or chronic stress where there is hypo- and hypersensitivity of these afferents, respectively. Improved understanding of the plasticity of these afferents will enable identification of new treatment options for diseases associated with vagal afferent function.

Application of small angle scattering (SAS) in structural characterisation of casein and casein-based products during digestion

In recent years, small and ultra-small angle scattering techniques, collectively known as small angle scattering (SAS) have been used to study various food structures during the digestion process. These techniques play an important role in structural characterisation due to the non-destructive nature (especially when using neutrons), various in situ capabilities and a large length scale (of 1 nm to ∼20 μm) they cover. The application of these techniques in the structural characterisation of dairy products has expanded significantly in recent years. Casein, a major dairy protein, forms the basis of a wide range of gel structures at different length scales. These gel structures have been extensively researched utilising scattering techniques to obtain structural information at the nano and micron scale that complements electron and confocal microscopy. Especially, neutrons have provided opportunity to study these gels in their natural environment by using various in situ options. One such example is understanding changes in casein gel structures during digestion in the gastrointestinal tract, which is essential for designing personalised food structures for a wide range of food-related diseases and improve health outcomes. In this review, we present an overview of casein gels investigated using small angle and ultra-small angle scattering techniques. We also reviewed their digestion using newly built setups recently employed in various research. To gain a greater understanding of micro and nano-scale structural changes during digestion, such as the effect of digestive juices and mechanical breakdown on structure, new setups for semi-solid food materials are needed to be optimised.

Diffeomorphic Surface Modeling for MRI-Based Characterization of Gastric Anatomy and Motility

OBJECTIVE

Gastrointestinal magnetic resonance imaging (MRI) provides rich spatiotemporal data about the movement of the food inside the stomach, but does not directly report muscular activity on the stomach wall. Here we describe a novel approach to characterize the motility of the stomach wall that drives the volumetric changes of the ingesta.

METHODS

A neural ordinary differential equation was optimized to model a diffeomorphic flow that ascribed the deformation of the stomach wall to a continuous biomechanical process. Driven by this diffeomorphic flow, the surface of the stomach progressively changes its shape over time, while preserving its topology and manifoldness.

RESULTS

We tested this approach with MRI data collected from 10 rats under a lightly anesthetized condition, and demonstrated accurate characterization of gastric motor events with an error in the order of sub-millimeters. Uniquely, we characterized gastric anatomy and motility with a surface coordinate system common at both individual and group levels. Functional maps were generated to reveal the spatial, temporal, and spectral characteristics of muscle activity and its coordination across different regions. The peristalsis at the distal antrum had a dominant frequency and peak-to-peak amplitude of [Formula: see text] cycles per minute and [Formula: see text] mm, respectively. The relationship between muscle thickness and gastric motility was found to be distinct between two functional regions in the proximal and distal stomach.

CONCLUSION

These results demonstrate the efficacy of using MRI to model gastric anatomy and function.

SIGNIFICANCE

The proposed approach is expected to enable non-invasive and accurate mapping of gastric motility for preclinical and clinical studies.

The contribution of cell wall integrity to gastric emptying and in vitro starch digestibility and fermentation performance of highland barley foods

Studies have shown that the structure, composition, and bioavailability of compounds in whole grains are affected by processing and the role of cells walls. In this study, the effects of different processing methods on highland barley, one of the mostly widely produced whole grains worldwide, were investigated. The processing methods applied were flaking-boiling (HB flake), sand-roasting (Puffed HB), and sand-roasting-milling (Tsamba). Results showed Puffed HB and Tsamba had higher levels of damaged starch content, starch short-range molecular order, and relative crystallinity than HB flake. The half-time of gastric emptying (t_1/2) was the slowest for Tsamba (132.3 min) compared to HB flake (122.5 min) and Puffed HB (84.0 min), indicating the slowest gastric emptying rate, which could be attributed to its high viscosity of gastric digesta. After in vitro gastroduodenal digestion, Puffed HB exhibited the lowest starch digestibility and the least amount of β-glucan due to its less damaged cellular structure. Furthermore, Puffed HB resulted in a 21% and 18% higher in vitro production of total short-chain fatty acids than Tsamba and HB flake, respectively. Besides, undigested starch of Puffed HB after in vitro gastroduodenal digestion delayed in vitro fecal fermentation of β-glucan. Our study provided insight into the potential mechanisms of how cell wall integrity affected the gastric emptying, in vitro starch digestibility, and in vitro fecal fermentation of highland barley foods.

Effects of Four Different Dietary Fibre Supplements on Weight Loss and Lipid and Glucose Serum Profiles during Energy Restriction in Patients with Traits of Metabolic Syndrome: A Comparative, Randomized, Placebo-Controlled Study

Obesity and its associated complications require various lifestyle changes and treatment options. Dietary supplements are considered an attractive alternative to traditional therapy, mainly because they are accessible to the general population. The aim of this study was to investigate the additive effects of a combination of energy restriction (ER) and four dietary supplements on changes in the anthropometric and biochemical parameters in 100 overweight or obese participants who were randomly assigned one of the dietary fibre supplements containing different dietary fibres or a placebo for 8 weeks. The results confirmed that fibre supplements plus ER significantly (p < 0.01) reduced the body weight, body mass index (BMI), fat mass, and visceral fat and ameliorated the lipid profile and inflammation at 4 and 8 weeks after the start of the study, while in the placebo group, significant differences in some parameters were observed only after 8 weeks of ER. A fibre supplement containing glucomannan, inulin, psyllium, and apple fibre was the most effective at reducing the BMI, body weight, and CRP (p = 0.018 for BMI and body weight and p = 0.034 for CRP compared to placebo at the end of the intervention). Overall, the results suggest that dietary fibre supplements in combination with ER may have additional effects on weight loss and the metabolic profile. Therefore, taking dietary fibre supplements may be a feasible approach to improve weight and metabolic health in obese and overweight individuals.

Role of segmental contraction in the small intestinal digestion: A computational approach to study the physics behind the luminal mixing and transport

Segmentation is well known to digest the food rich in proteins, starch, and lipids; however, the mechanism leading to the digestion remains unclear. In this study, a theoretical model for segmental contractions of the small intestine is developed using lubrication method to explore the mechanisms involved. Here, the nonlinear partial differential equations governing the fluid flow were normalized in viscous regime and solved semi-analytically for a power law fluid under long wavelength approximation on a Matlab^TM platform. Study indicates that shearing is highest at the 1st and 4th mid-occlusion in comparison to 2nd and 3rd mid-occlusion. Parametric study indicates that the flow is sensitive to - the span of segmentation or wavelength of the wave, occlusion of the wave and frequency of the contraction; with shearing being highest for dilatants. Shearing is more prominent at higher occlusion (>50 %) and frequency (>6Hz). Further, mixing is more prominent at the steep regions of the wave; having intensity of mixing highest for the outer waves in comparison to waves at mid-region of the segmentation. The power demand is found to be greater in segmentation and has the following precedence - frequency, wavelength, flow behavior index, and occlusion (up to 80 %). Further, multiplicity of the wave gives rise to multiple zones of mixing which increases the rate of mixing of the contents. Suggesting that, the segmentation primarily serves the purpose of mixing. The study will be useful to explore novel therapeutic strategies of managing patients suffering from various motility-associated disorders of the small intestine.

The importance of molecular weight in determining the minimum dose of oat β-glucan required to reduce the glycaemic response in healthy subjects without diabetes: a systematic review and meta-regression analysis

To determine the minimum amount of oat β-glucan (OBG) required to reduce glycaemic responses (MinDose), we conducted a systematic review and meta-regression analysis of acute, crossover, single-meal feeding trials that examined the effects of adding OBG or oat bran to a carbohydrate-containing test-meal versus a control test-meal containing an equivalent amount of available-carbohydrate (avCHO) from the same or similar source. Medline, Embase, and Cochrane Library were searched up to 18 August 2021. The primary outcome was glucose incremental-area-under-the-curve (iAUC). Secondary outcomes included insulin iAUC, and glucose and insulin incremental peak-rise (iPeak). Two independent reviewers extracted data. Results were expressed as ratio-of-means (RoM) with 95% confidence intervals (CIs). Linear associations were assessed by random effects meta-regression. MinDose was defined as the dose at which the upper 95% CI of the regression line cut the line of no effect (i.e., RoM = 1). Fifty-nine comparisons (n = 340) were included; 57 in healthy subjects without diabetes and two in subjects with diabetes; 24 high-MW (>1000 kg/mol), 22 medium-MW (300-1,000 kg/mol), and 13 low-MW (<300 kg/mol). In healthy subjects without diabetes the associations between OBG dose and glucose iAUC and iPeak were linear (non-linear p value >0.05). MinDoses for glucose iAUC for high-MW, medium-MW and low-MW OBG, respectively, were estimated to be 0.2 g, 2.2 g and 3.2 g per 30 g avCHO; MinDoses for glucose iPeak were less than those for iAUC. Insufficient data were available to assess MinDose for insulin, however, there was no evidence of a disproportionate increase in insulin. More high-quality trials are needed to establish MinDose in individuals with diabetes.

PhysioCell®; - a Novel, Bio-relevant Dissolution Apparatus: Hydrodynamic Conditions and Factors Influencing the Dissolution Dynamics

The physiologically relevant dissolution apparatuses simulate various aspects of gastrointestinal physiology and help to understand and predict the in vivo behavior of an oral dosage form. In this paper, we present and characterize for the first time a novel bio-relevant dissolution apparatus - PhysioCell®;. We evaluated the impact of several factors on the hydrodynamic conditions in the key vessel of the apparatus - the StressCell. We observed that the medium flow rate, but not the glass beads' size or amount, significantly influenced the dissolution rate. The relationship was disproportional: the increase in the flow rate from 4.6 to 9.0 mL/min reduced the dissolution time of 85% (T85) of the NaCl tablet by 46%, but from 134 to 300 mL/min decreased the T85 only by 24%. At the same time, the contractions of the StressCell's elastic walls promoted the content mixing and enhanced the dissolution rate of the paracetamol tablets: even very rare mixing contractions (1 per 10 min) decreased the T85 over twofold for the flow rate of 8 mL/min. In conclusion, the hydrodynamic conditions in the StressCell affect the dissolution of solid dosage forms and the understanding of these effects is crucial for modeling physiologically-based test conditions in the novel apparatus. Combinations of the unique PhysioCell®;features - adjustable medium flow, temperature control, controllable pH gradients and predefined mechanical agitation - can create a set of dissolution test scenarios for characterization of oral dosage forms and, in the future, making the in vitro-in vivo predictions. Graphical Abstract.

Bridging the Gap between Food Effects under Clinical Trial Conditions and Real Life: Modeling Delayed Gastric Emptying of Drug Substances and Gastric Content Volume Based on Meal Characteristics

Delayed gastric emptying is known to have a major impact on drug absorption. While the test meal recommended by the FDA and EMA to study food effects represents a worst-case scenario, it does not reflect the reality of the patients. Physiologically based pharmacokinetic (PBPK) models could bridge the gap between clinical settings of food effect studies and the diverse nonclinical situations by simulating the effect of meals with different compositions and volumes. A mathematical equation based on a stretched exponential function was reparameterized to describe the gastric emptying process of mixed solid meals. The model was fitted to literature data including the gastric emptying data of 23 meals from 15 studies. Using a multiple linear regression model, we were able to predict the two function parameters from the meal characteristics caloric content and the percentage of calories derived from fat. After implementation into the PBPK software PK-Sim, the model, together with a separate compartment for liquid gastric contents, was compared to commercially available software. The model is able to simulate the gastric emptying of mixed solid meals containing drugs based on specific meal characteristics. A second compartment allows for distribution between liquid and solid components and rapid gastric emptying along the Magenstrasse.

Integrating In Vitro Biopharmaceutics into Physiologically Based Biopharmaceutic Model (PBBM) to Predict Food Effect of BCS IV Zwitterionic Drug (GSK3640254)

A strategy followed to integrate in vitro solubility and permeability data into a PBBM model to predict the food effect of a BCS IV zwitterionic drug (GSK3640254) observed in clinical studies is described. The PBBM model was developed, qualified and verified using clinical data of an immediate release (IR)-tablet (10-320 mg) obtained in healthy volunteers under fasted and fed conditions. The solubility of GSK3640254 was a function of its ionization state, the media composition and pH, whereas its permeability determined using MDCK cell lines was enhanced by the presence of mixed micelles. In vitro data alongside PBBM modelling suggested that the positive food effect observed in the clinical studies was attributed to micelle-mediated enhanced solubility and permeability. The biorelevant media containing oleic acid and cholesterol in fasted and fed levels enabled the model to appropriately capture the magnitude of the food effect. Thus, by using Simcyp^® v20 software, the PBBM model accurately predicted the results of the food effect and predicted data were within a two-fold error with 70% being within 1.25-fold. The developed model strategy can be effectively adopted to increase the confidence of using PBBM models to predict the food effect of BCS class IV drugs.

Effects of peristaltic amplitude and frequency on gastric emptying and mixing: a simulation study

The amplitude and frequency of peristaltic contractions are two major parameters for assessing gastric motility. However, it is not fully understood how these parameters affect the important functions of the stomach, such as gastric mixing and emptying. This study aimed to quantify the effects of peristaltic amplitude and frequency on gastric mixing and emptying using computational fluid dynamics simulation of gastric flow with an anatomically realistic model of the stomach. Our results suggest that both the increase and decrease in peristaltic amplitude have a significant impact on mixing strength and emptying rate. For example, when the peristaltic amplitude was 1.2 times higher than normal, the emptying rate was 2.7 times faster, whereas when the amplitude was half, the emptying rate was 4.2 times slower. Moreover, the emptying rate increased more than proportionally with the peristaltic frequency. The nearest contraction wave to the pylorus and the subsequent waves promoted gastric emptying. These results suggest the importance of maintaining parameters within normal ranges to achieve healthy gastric function.

Study of Selected Beverages with Β-Glucan from Oats and Barley on Physical Properties, Sensory Perception, Glycemic Index and Satiety

Over recent years, more and more products with β-glucan have appeared in the market. This study was conducted to determine the physical, sensory evaluation and glycemic index (GI) of selected popular beverages with β-glucan in the Malaysian market, which were Biogrow Oat BG22 (from oats) and Biolife Barley BG25 (from barley). The physical parameters measured were colour, viscosity, and total suspended solid. Sensory analysis was conducted on 30 subjects using the 7-point hedonic scale. Attributes assessed were colour, aroma, viscosity, sweetness and overall acceptance. A total of 10 subjects were involved in the determination of GI value of these beverages. A total of 25 g glucose was used as the reference. Test meals also contained 25 g available carbohydrate and all beverages were mixed with 250 mL water. Blood samples (finger prick) were taken every 15 minutes (first hour) and 30 minutes (second hour) for the duration of 120 minutes after the food sample consumption. Test protocol was based on ISO26642:2010. Blood glucose values were determined using glucometer. A total of 30 subjects were chosen for the determination of satiety scores. Labelled magnitude satiety scale was used to measure satiety scores before and after test beverage consumption. Subjects were required to assess their perception of fullness or hunger by marking on the labelled magnitude satiety scale every 15 minutes for the first hour and 30 minutes for subsequent 2 hour for a total of 180 minutes. The colour analysis showed that BG25 and BG22 were slightly yellow due to positive b* value. The BG22 was more viscous and do not contain any sugar compared to BG25. Blood glucose level after glucose intake reached optimum level (9.9 mmol/L) at 30 minutes while BG25 and BG22 reached optimum level at 45 minutes with the value 7.9 mmol/L and 6.4 mmol/L respectively. Significant difference was found for attributes aroma, viscosity and overall acceptance of the two products. Our study found, BG22 from oats were has better physical attributes and is better accepted by the panelists. However, it is suggested that both products be taken together with milk or soy to improve the taste. The GI for BG25 was 79 (high GI) while BG22 was 32 (low GI). The BG22 with lower GI is significantly more satiating than BG25 and perhaps can be a choice of beverage for people who are managing diabetes and obesity.

Effect of stomach motility on food hydrolysis and gastric emptying: Insight from computational models

The peristaltic motion of stomach walls combines with the secretion of digestive enzymes to initiate the process that breaks down food. In this study, the mixing, breakdown, and emptying of a liquid meal containing protein is simulated in a model of a human stomach. In this model, pepsin, the gastric enzyme responsible for protein hydrolysis, is secreted from the proximal region of the stomach walls and allowed to react with the contents of the stomach. The velocities of the retropulsive jet induced by the peristaltic motion, the emptying rate, and the extent of hydrolysis are quantified for a control case as well as for three other cases with reduced motility of the stomach, which may result from conditions such as diabetes mellitus. This study quantifies the effect of stomach motility on the rate of food breakdown and its emptying into the duodenum and we correlate these observations with the mixing in the stomach induced by the wall motion.

Time Courses of Gastric Volume and Content after Different Types of Casein Ingestion in Healthy Men: A Randomized Crossover Study

BACKGROUND

Few studies have evaluated differences in the curd-forming ability of casein on gastric volume and content directly after ingestion in humans.

OBJECTIVES

This study evaluated the time course of gastric volume and curd conditions in the stomach after protein ingestion.

METHODS

This was an open-labeled, randomized crossover trial. Ten healthy men [age: 33.4 ± 7.3 y; BMI (kg/m²): 21.9 ± 0.9] received 350 g of 3 isonitrogenous and isocaloric protein drinks containing 30 g micellar casein (MCN), sodium caseinate (SCN), or whey protein concentrate (WPC). The gastric antrum cross-sectional area (CSA) and curd in the stomach were measured using ultrasonography within 5 h after ingestion. The differences between test foods were tested using the MIXED model and post hoc tests using Fisher's protected least significant difference.

RESULTS

The incremental AUC of the gastric antrum CSA after MCN ingestion was 1.3-fold and 1.5-fold higher than that after the ingestion of SCN and WPC, respectively (both P < 0.05), but not different between SCN and WPC. The number of participants with curds ≥20 mm with a high echogenicity clot observed in the stomach within 5 h after MCN ingestion was significantly greater than that after the ingestion of other proteins (n = 9 for MCN, n = 2 for SCN, and n = 0 for WPC; bothP < 0.01). The regression line slopes on total plasma amino acid concentration and gastric antrum CSA were significantly different between the participants with and without curds.

CONCLUSIONS

In contrast to SCN and WPC, MCN ingestion resulted in slow kinetics of gastric antrum CSA. Differences in curd formation of casein in the stomach affect gastric emptying and plasma amino acid absorption kinetics after ingestion in healthy men. This trial was registered at University Hospital Medical Information Network Clinical Trials Registry as UMIN000038388 (https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000043746).

Holistic approach to effects of foods, human physiology, and psychology on food intake and appetite (satiation & satiety)

Appetite (satiation and satiety) is an essential element for the control of eating behavior, and as a consequence human nutrition, body weight, and chronic disease risk. A better understanding of appetite mechanisms is necessary to modulate eating behavior and food intake, and also provide a practical approach for weight management. Although many researchers have investigated the relationships between satiation/satiety and specific factors including human physiology, psychology, and food characteristics, limited information on the interactions between factors or comparisons between the relative importance of factors in contributing to satiation/satiety have been reported. This article reviews progress and gaps in understanding individual attributes contributing to perceived satiation/satiety, the advantages of considering multiple factors together in appetite experiments, as well as the applications of nondestructive sensing in evaluating human factors contributing to relative appetite perception. The approaches proposed position characterization of appetite (satiation and satiety) for personalized and precision nutrition in relation to human status and healthy diets. In particular, it is recommended that future studies of appetite perception recognize the inter-dependence of food type and intake, appetite (satiation and satiety), and individual status.

Sodium caseinate enhances the effect of konjac flour on delaying gastric emptying based on a dynamic in vitro human stomach-IV (DIVHS-IV) system

BACKGROUND

In the context of the increasing prevalence of overweight and obesity worldwide, satiety-enhancing foods may help people control their energy intake and weight. In this study, an advanced near-real human gastric simulator equipped with a dynamic in vitro human stomach-IV (DIVHS-IV) system was used to determine the gastric digestion and gastric retention ratio of konjac flour (KF)/sodium caseinate (SC) mixtures with different ratios.

RESULTS

The apparent viscosity, viscoelastic properties, confocal laser scanning microscopy (CLSM) of the digested products were collected and analyzed to further study the effect of SC on the physical properties of KF during digestion. The results showed that the addition of SC could enhance the effect of KF on delaying gastric emptying in vitro. Besides, the addition of SC was shown to weaken the effect of gastric juice on the dilution of gastric contents by forming SC gel blocks in the acid environment. In particular, the synergistic gastric emptying delaying effect was the strongest in the KF/SC mixture containing 1% KF and 8% SC, and obvious massive aggregates were observed.

CONCLUSION

The combination of 1% KF and 8% SC was shown to synergistically delay gastric emptying and potentially enhance the sense of fullness. © 2022 Society of Chemical Industry.

Riceberry rice (Oryza sativa L.) slows gastric emptying and improves the postprandial glycaemic response

Postprandial glycaemia is a key determinant of overall glycaemic control. One mechanism by which dietary strategies can reduce postprandial glycaemic excursions is by slowing gastric emptying. This study aimed to evaluate the acute effect of ingesting riceberry rice (RR) compared with that of ingesting white rice (WR) on gastric emptying rate (GER), plasma glucose and glucose-regulating hormones, including insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1), in healthy subjects. A randomised, open-label, within-subject, crossover study was performed in six healthy men. GER was measured by scintigraphy over 240 min, and plasma concentrations of glucose, insulin, GLP-1 and GIP were measured at multiple time points over 180 min. This study revealed that RR slows GER with a reduction in postprandial plasma glucose concentrations compared with WR. Plasma insulin and GLP-1 concentrations did not differ between RR and WR. However, plasma GIP concentrations were markedly increased after WR ingesting v. after RR ingestion. We conclude that RR attenuates postprandial glycaemia by slowing GER without altering plasma insulin or GLP-1. Plasma GIP concentrations are likely related to differences in GER and carbohydrate absorption. We propose that dietary fibre-enriched foods, including RR, could contribute to improvement in postprandial glycaemia via delayed gastric emptying.

The [13 C]octanoic acid breath test for gastric emptying quantification: A focus on nutrition and modeling

Gastric emptying (GE) is the process of food being processed by the stomach and delivered to the small intestine where nutrients such as lipids are absorbed into the blood circulation. The combination of an easy and inexpensive method to measure GE such as the CO₂ breath test using the stable isotope [¹³C]octanoic acid with semi‐mechanistic modeling could foster a wider application in nutritional studies to further understand the metabolic response to food. Here, we discuss the use of the [¹³C]octanoic acid breath test to label the solid phase of a meal, and the factors that influence GE to support mechanistic studies. Furthermore, we give an overview of existing mathematical models for the interpretation of the breath test data and how much nutritional studies could benefit from a physiological based pharmacokinetic model approach.

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.

Vehicles for Drug Administration to Children: Results and Learnings from an In-Depth Screening of FDA-Recommended Liquids and Soft Foods for Product Quality Assessment

Purpose

Mixing with liquids or soft foods is a common procedure to improve acceptability of oral medicines in children but may affect drug stability and the in vivo performance of the administered drug product. The aim of the present study was to obtain an overview of the variability of critical attributes of commonly used vehicles and to identify which vehicle characteristics need to be considered when developing in vitro methods for evaluating product quality.

Methods

One product of each vehicle listed in the FDA draft guidance “Use of Liquids and/or Soft Foods as Vehicles for Drug Administration” was analyzed with regard to composition, calorific content and physicochemical properties.

Results

The studied vehicles show wide variability, both in composition and physicochemical properties. No correlation was observed between vehicle composition and physicochemical properties. Comparison of results of the present study with previously published data also provided variability in physicochemical properties within individual vehicle types.

Conclusions

To identify acceptable (qualified) vehicles for global drug product labeling, it is important that the vehicles selected for in vitro compatibility screening reflect the variability in composition and essential physicochemical properties of the vehicles recommended on the product label, rather than relying on results obtained with a single vehicle of each type. Future activities will focus on the development of standardized dosing vehicles that can represent key vehicle characteristics in all their variability to ensure reliable risk assessment.

An evolving view on food viscosity regulating gastric emptying

Viscosity is a property of most foods. The consumption of the high-viscosity food is associated with a variety of physiological responses, one of which is their ability to regulate gastric emptying and modulate postprandial glycemic response. Gastric emptying has been proven to be a key step affecting the digestion and absorption of food, whereas, the relationship between viscosity and gastric emptying is still far away from being understood. Here, we reviewed the factors that influence food viscosity and food viscosity changes during digestion. Besides, the effect of food viscosity on gastric emptying and food-viscosity-physiological response were highlighted. Finally, "quantitative relationship" of viscosity and gastric emptying was discussed. This review can contribute to the understanding that how food viscosity affects gastric emptying, and help for developing foods that could control satiety and manage body weight for the specific populations.

Automatic assessment of human gastric motility and emptying from dynamic 3D magnetic resonance imaging

BACKGROUND

Time-sequenced magnetic resonance imaging (MRI) of the stomach is an emerging technique for non-invasive assessment of gastric emptying and motility. However, an automated and systematic image processing pipeline for analyzing dynamic 3D (ie, 4D) gastric MRI data has not been established. This study uses an MRI protocol for imaging the stomach with high spatiotemporal resolution and provides a pipeline for assessing gastric emptying and motility.

METHODS

Diet contrast-enhanced MRI images were acquired from seventeen healthy humans after they consumed a naturalistic contrast meal. An automated image processing pipeline was developed to correct for respiratory motion, to segment and compartmentalize the lumen-enhanced stomach, to quantify total gastric and compartmental emptying, and to compute and visualize gastric motility on the luminal surface of the stomach.

KEY RESULTS

The gastric segmentation reached an accuracy of 91.10 ± 0.43% with the Type-I error and Type-II error being 0.11 ± 0.01% and 0.22 ± 0.01%, respectively. Gastric volume decreased 34.64 ± 2.8% over 1 h where the emptying followed a linear-exponential pattern. The gastric motility showed peristaltic patterns with a median = 4 wave fronts (range 3-6) and a mean frequency of 3.09 ± 0.07 cycles per minute. Further, the contractile amplitude was stronger in the antrum than in the corpus (antrum vs. corpus: 5.18 ± 0.24 vs. 3.30 ± 0.16 mm; p < 0.001).

CONCLUSIONS & INFERENCES

Our analysis pipeline can process dynamic 3D MRI images and produce personalized profiles of gastric motility and emptying. It will facilitate the application of MRI for monitoring gastric dynamics in research and clinical settings.

Dietary fibres and IBS: translating functional characteristics to clinical value in the era of personalised medicine

Clinical guidelines in the use of fibre supplementation for patients with IBS provide one-size-fits-all advice, which has limited value. This narrative review addresses data and concepts around the functional characteristics of fibre and subsequent physiological responses induced in patients with IBS with a view to exploring the application of such knowledge to the precision use of fibre supplements. The key findings are that first, individual fibres elicit highly distinct physiological responses that are associated with their functional characteristics rather than solubility. Second, the current evidence has focused on the use of fibres as a monotherapy for IBS symptoms overall without attempting to exploit these functional characteristics to elicit specific, symptom-targeted effects, or to use fibre types as adjunctive therapies. Personalisation of fibre therapies can therefore target several therapeutic goals. Proposed goals include achieving normalisation of bowel habit, modulation of gut microbiota function towards health and correction of microbial effects of other dietary therapies. To put into perspective, bulking fibres that are minimally fermented can offer utility in modulating indices of bowel habit; slowly fermented fibres may enhance the activities of the gut microbiota; and the combination of both fibres may potentially offer both benefits while optimising the activities of the microbiota throughout the different regions of the colon. In conclusion, understanding the GI responses to specific fibres, particularly in relation to the physiology of the individual, will be the future for personalising fibre therapy for enhancing the personalised management of patients with IBS.

Effect of the perception of breakfast consumption on subsequent appetite and energy intake in healthy males

Purpose

This study aimed to assess the effects of consuming a very-low-energy placebo breakfast on subsequent appetite and lunch energy intake.

Methods

Fourteen healthy males consumed water-only (WAT), very-low-energy, viscous placebo (containing water, low-calorie flavoured squash, and xanthan gum; ~ 16 kcal; PLA), and whole-food (~ 573 kcal; FOOD) breakfasts in a randomised order. Subjects were blinded to the energy content of PLA and specific study aims. Venous blood samples were collected pre-breakfast, 60- and 180-min post-breakfast to assess plasma acylated ghrelin and peptide tyrosine tyrosine concentrations. Subjective appetite was measured regularly, and energy intake was assessed at an ad libitum lunch meal 195-min post-breakfast.

Results

Lunch energy intake was lower during FOOD compared to WAT (P < 0.05), with no further differences between trials (P ≥ 0.132). Cumulative energy intake (breakfast plus lunch) was lower during PLA (1078 ± 274 kcal) and WAT (1093 ± 249 kcal), compared to FOOD (1554 ± 301 kcal; P < 0.001). Total area under the curve (AUC) for hunger, desire to eat and prospective food consumption were lower, and fullness was greater during PLA and FOOD compared to WAT (P < 0.05). AUC for hunger was lower during FOOD compared to PLA (P < 0.05). During FOOD, acylated ghrelin was suppressed compared to PLA and WAT at 60 min (P < 0.05), with no other hormonal differences between trials (P ≥ 0.071).

Conclusion

Consuming a very-low-energy placebo breakfast does not alter energy intake at lunch but may reduce cumulative energy intake across breakfast and lunch and attenuate elevations in subjective appetite associated with breakfast omission.

Trial registration

NCT04735783, 2nd February 2021, retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02727-5.

Matrix structure of dairy products results in different postprandial lipid responses: a randomized crossover trial

BACKGROUND

The dairy matrix may influence digestion and absorption of lipids and thereby risk of cardiovascular diseases (CVDs). However, few postprandial studies have compared dairy products that differed only in terms of their matrix.

OBJECTIVES

We aimed to investigate acute 8-h postprandial lipid, glycemic, and appetite responses after intake of isoenergetic dairy meals with different matrixes, but similar nutritional composition.

METHODS

Twenty-five normal-weight men (18-40 y old) were enrolled in a randomized controlled crossover trial. On 4 test days, a meal with 1 of 4 dairy products was served: cheddar cheese (Cheese), homogenized Cheese (Hom. Cheese), micellar casein isolate (MCI) with cream (MCI Drink), and a gel produced from the MCI Drink by addition of Glucono Delta-Lactone (MCI Gel). The fat- and protein-matched dairy products differed in terms of their casein network, fat droplet size, and/or texture. Blood biochemistry and appetite responses were collected.

RESULTS

Eighteen participants completed the trial. Postprandial triglycerides (TGs) (primary outcome) increased by (mean ± SEM) 0.24 ± 0.07 and 0.19 ± 0.07 mmol/L after MCI Gel compared with Cheese and Hom. Cheese, respectively (both P ≤ 0.05). Likewise, MCI Gel increased TG incremental AUC compared with Cheese and Hom. Cheese (both P < 0.05), and peak compared with Cheese (P < 0.05). ApoB-48 (primary outcome) was unaffected by dairy matrix. For free fatty acids (FFAs), glucose, and insulin, time × meal interactions were observed (all P < 0.001). During the first 2 h, FFAs were lower for Cheese than for MCI products, whereas the opposite was observed for glucose and insulin.

CONCLUSIONS

Postprandial TG but not apoB-48 response was higher after MCI Gel, indicating that the type of casein network influences lipid responses. This suggests that the dairy matrix may also affect risk factors for CVDs. Reducing fat droplet size (i.e., Hom. Cheese) did not affect blood biochemistry.This trial was registered at clinicaltrials.gov as NCT03656367.

Some pearl millet-based foods promote satiety or reduce glycaemic response in a crossover trial

In a previous trial in Mali, we showed that traditional pearl millet couscous and thick porridge delayed gastric emptying (about 5 h half-emptying times) in a normal-weight population compared with non-traditional carbohydrate-based foods (pasta, potatoes, white rice; about 3 h half-emptying times), and in a gastric simulator we showed millet couscous had slower digestion than wheat couscous. In light of these findings, we tested the hypothesis in a normal-weight US population (n 14) that millet foods would reduce glycaemic response (continuous glucose monitor), improve appetitive sensations (visual analogue scale ratings), as well as reduce gastric emptying rate (13C-octanoic acid breath test). Five carbohydrate-based foods (millet couscous - commercial and self-made, millet thick porridge, wheat couscous, white rice) were fed in a crossover trial matched on available carbohydrate basis. Significantly lower overall glycaemic response was observed for all millet-based foods and wheat couscous compared with white rice (P ≤ 0·05). Millet couscous (self-made) had significantly higher glycaemic response than millet couscous (commercial) and wheat couscous (P < 0·0001), but as there were no differences in peak glucose values an extended glycaemic response was indicated for self-made couscous. Millet couscous (self-made) had significantly lower hunger ratings and higher fullness ratings (P < 0·05) than white rice, millet thick porridge and millet couscous (commercial). A normal gastric emptying rate (<3 h half-emptying times) was observed for all foods, with no significant differences among them. In conclusion, some traditionally prepared pearl millet foods show the potential to reduce glycaemic response and promote satiety.

Malian Thick Porridges (tô) of Pearl Millet Are Made Thinner in Urban Than Rural Areas and Decrease Satiety

BACKGROUND

Changes in preparation, preference, and consumption of traditional staple foods between rural and urban areas in sub-Saharan Africa may be associated with the nutrition transition.

OBJECTIVE

Millet porridge thickness and postprandial hunger were investigated in Mali with the aim of understanding consumer preference and satiety properties.

METHODS

Rural and urban residents from 3 regions (N = 60) were surveyed regarding their porridge consumption frequency and thickness preference. Influence of millet porridge thickness on satiety was investigated. Ten participants consumed 4 porridges of different thicknesses (3 of millet and 1 thin porridge of rice) and rated their subjective hunger on 4 different days.

RESULTS

Thicker porridges were consumed more frequently in rural areas than in urban (P < .05). For the satiety study, thicker porridges induced higher satiety than thinner ones at 2 and 4 hours postconsumption (P < .05; Visual Analog Scale rating). A greater amount of flour, but not volume, was consumed for the thicker porridges (P < .05).

CONCLUSIONS

Urban participants preferred and consumed porridges that are less satiating, potentially contributing to higher food consumption related to the nutrition transition in Africa.

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

Evaluation of orally ingestible devices is critical to optimize their performance early in development. Using animals as a pre-clinical tool can provide useful information on functionality, yet it is important to recognize that animal gastrointestinal physiology, pathophysiology and anatomy can differ to that in humans and that the most suitable species needs to be selected to inform the evaluation. There has been a move towards in vitro and in silico models rather than animal models in line with the 3Rs (Replacement, Reduction and Refinement) as well as the better control and reproducibility associated with these systems. However, there are still instances where animal models provide the greatest understanding. This paper provides an overview of key aspects of human gastrointestinal anatomy and physiology and compares parameters to those reported in animal species. The value of each species can be determined based upon the parameter of interest from the ingested device when considering the use of pre-clinical animal testing.

Non-uniform gastric wall kinematics revealed by 4D Cine magnetic resonance imaging in humans

BACKGROUND

Assessment of gastric function in humans has relied on modalities with varying degrees of invasiveness, which are usually limited to the evaluation of single aspects of gastric function, thus requiring patients to undergo a number of often invasive tests for a full clinical understanding. Therefore, the development of a non-invasive tool able to concurrently assess multiple aspects of gastric function is highly desirable for both research and clinical assessments of gastrointestinal (GI) function. Recently, technological advances in magnetic resonance imaging (MRI) have provided new tools for dynamic (or "cine") body imaging. Such approaches can be extended to GI applications.

METHODS

In the present work, we propose a non-invasive assessment of gastric function using a four-dimensional (4D, volumetric cine imaging), free-breathing MRI sequence with gadolinium-free contrast enhancement achieved through a food-based meal. In healthy subjects, we successfully estimated multiple parameters describing gastric emptying, motility, and peristalsis propagation patterns.

KEY RESULTS

Our data demonstrated non-uniform kinematics of the gastric wall during peristaltic contraction, highlighting the importance of using volumetric data to derive motility measures.

CONCLUSIONS & INFERENCES

MRI has the potential of becoming an important clinical and gastric physiology research tool, providing objective parameters for the evaluation of impaired gastric function.

Inflammatory effect on the gastrointestinal system associated with COVID-19

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) that causes coronavirus disease-2019 (COVID-19) has provoked a global pandemic, mainly affecting the respiratory tract; however, a percentage of infected individuals can develop gastrointestinal (GI) symptoms. Some studies describe the development of GI symptoms and how they affect the progression of COVID-19. In this review, we summarize the main mechanisms associated with gut damage during infection by SARS-CoV-2 as well as other organs such as the liver and pancreas. Not only are host factors associated with severe COVID-19 but intestinal microbiota dysbiosis is also observed in patients with severe disease.

Structural breakdown of starch-based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

The digestion of starch-based foods in the small intestine as well as factors affecting their digestibility have been previously investigated and reviewed in detail. Starch digestibility has been studied both in vivo and in vitro, with increasing interest in the use of in vitro models. Although previous in vivo studies have indicated the effect of mastication and gastric digestion on the digestibility of solid starch-based foods, the physical breakdown of starch-based foods prior to small intestinal digestion is often less considered. Moreover, gastric digestion has received little attention in the attempt to understand the digestion of solid starch-based foods in the digestive tract. In this review, the physical breakdown of starch-based foods in the mouth and stomach, the quantification of these breakdown processes, and their links to physiological outcomes, such as gastric emptying and glycemic response, are discussed. In addition, the physical breakdown aspects related to gastric digestion that need to be considered when developing in vitro-in vivo correlation in starch digestion studies are discussed. The discussion demonstrates that physical breakdown prior to small intestinal digestion, especially during gastric digestion, should not be neglected in understanding the digestion of solid starch-based foods.

Macronutrient Sensing in the Oral Cavity and Gastrointestinal Tract: Alimentary Tastes

There are numerous and diverse factors enabling the overconsumption of foods, with the sense of taste being one of these factors. There are four well established basic tastes: sweet, sour, salty, and bitter; all with perceptual independence, salience, and hedonic responses to encourage or discourage consumption. More recently, additional tastes have been added to the basic taste list including umami and fat, but they lack the perceptual independence and salience of the basics. There is also emerging evidence of taste responses to kokumi and carbohydrate. One interesting aspect is the link with the new and emerging tastes to macronutrients, with each macronutrient having two distinct perceptual qualities that, perhaps in combination, provide a holistic perception for each macronutrient: fat has fat taste and mouthfeel; protein has umami and kokumi; carbohydrate has sweet and carbohydrate tastes. These new tastes can be sensed in the oral cavity, but they have more influence post- than pre-ingestion. Umami, fat, kokumi, and carbohydrate tastes have been suggested as an independent category named alimentary. This narrative review will present and discuss evidence for macronutrient sensing throughout the alimentary canal and evidence of how each of the alimentary tastes may influence the consumption of 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.