Preventing gastric sieving by blending a solid/water meal enhances satiation in healthy humans

Intra- and interindividual variability in fasted gastric content volume

BACKGROUND

Gastric fluid plays a key role in food digestion and drug dissolution, therefore, the amount of gastric fluid present in a fasted state may influence subsequent digestion and drug delivery. We aimed to describe intra- and interindividual variation in fasted gastric content volume (FGCV) and to determine the association with age, sex, and body size characteristics.

METHODS

Data from 24 MRI studies measuring FGCV in healthy, mostly young individuals after an overnight fast were pooled. The analysis included 366 participants who had up to 6 repeated measurements, with a total of 870 measurements. Linear mixed model analysis was performed to calculate intra- and interindividual variability and to assess the effects of age, sex, weight, height, weight*height as a proxy for body size, and body mass index (BMI).

RESULTS

FGCV ranged from 0 to 156 mL, with a mean (± SD) value of 33 ± 25 mL. The overall coefficient of variation within the study population was 75.6%, interindividual SD was 15 mL, and the intraindividual SD was 19 mL. Age, weight, height, weight*height, and BMI had no effect on FGCV. Women had lower volumes compared to men (MD: -6 mL), when corrected for the aforementioned factors.

CONCLUSION

FGCV is highly variable, with higher intraindividual compared to interindividual variability, indicating that FGCV is subject to day-to-day and within-day variation and is not a stable personal characteristic. This highlights the importance of considering FGCV when studying digestion and drug dissolution. Exact implications remain to be studied.

Randomized, crossover trial: comparing the effects of standardized egg-white meal and Vital® on global gastric emptying parameters and intragastric meal distribution in healthy Asian participants

BACKGROUND AND AIM

Measurements of gastric emptying and accommodation for alternative test-meal protocol during gastric emptying scintigraphy (GES), such as high-calorie nutrient drinks, are not fully established. We aimed to compare the effects of standardized egg-white meal (EWM) versus high-calorie nutrient drink (Vital®; Abbott Laboratories) on global GES parameters and intragastric meal distribution at immediate scan (IMD0h).

METHODS

Of 84 screened participants, 60 asymptomatic healthy Asian population (38 females; 24.0 ± 1.5 years; 23.8 ± 2.6 kg/m2) were recruited in this 2 × 2 (AB/BA) crossover trial. Participants were randomized to a 4-h GES with 99mTc-radiolabeled EWM (~255.8 kcal), followed by a 200 mL Vital® (300 kcal), or vice versa, separated by a 2-week washout period. Global meal retention (GMR), power-exponential model emptying parameters (half-emptying [T1/2], lag phases [Tlag2%, Tlag5%, Tlag10%]), and IMD0h were determined and compared.

RESULTS

GMRs for both test meals were within the international standard references for solid GES. Compared to EWM, Vital® exhibited significantly lower GMRs (faster emptying) from 0.5 to 3 h (all P < 0.001) but comparable at 4 h (P = 0.153). Similar observations were found for the model-based T1/2 and the different Tlag thresholds (all P < 0.001). Furthermore, IMD0h was found to be lower with Vital®, indicating lower gastric accommodation (faster antral filling) immediately post-ingestion (P < 0.001). Both test meals showed significant moderate-to-strong positive associations at the late-phase GE (GMR 2-4 h, T1/2) (all P < 0.05).

CONCLUSIONS

Overall, Vital® is an acceptable alternative test meal to the EWM for GES; however, exercise caution when interpreting early-phase GE. The normative values for global GES parameters and IMD0h are also established.

Gastric coagulation and postprandial amino acid absorption of milk is affected by mineral composition: a randomized crossover trial

Background: In vitro studies suggest that casein coagulation of milk is influenced by its mineral composition, and may therefore affect the dynamics of protein digestion, gastric emptying and appearance of amino acids (AA) in the blood, but this remains to be confirmed in vivo. Objective: This study aimed to compare gastrointestinal digestion between two milks with the same total calcium content but different casein mineralization (CM). Design: Fifteen males (age 30.9 ± 13.8 years, BMI 22.5 ± 2.2 kg m-2) participated in this randomized cross-over study with two treatments. Participants underwent gastric magnetic resonance imaging (MRI) scans at the baseline and every 10 min up to 90 min after consumption of 600 ml milk with low or high CM. Blood samples were taken at the baseline and up to 5 hours postprandially. Primary outcomes were postprandial plasma AA concentrations and gastric emptying rate. Secondary outcomes were postprandial glucose and insulin levels, gastric coagulation as estimated by image texture metrics, and appetite ratings. Results: Gastric content volume over time was similar for both treatments. However, gastric content image analysis suggested that the liquid fraction emptied quicker in the high CM milk, while the coagulum emptied slower. Relative to high CM, low CM showed earlier appearance of AAs that are more dominant in casein, such as proline (MD 4.18 μmol L-1, 95% CI [2.38-5.98], p < 0.001), while there was no difference in appearance of AAs that are more dominant in whey protein, such as leucine. The image texture metrics homogeneity and busyness differed significantly between treatments (MD 0.007, 95% CI [0.001, 0.012], p = 0.022; MD 0.005, 95% CI [0.001, 0.010], p = 0.012) likely because of a reduced coagulation in the low CM milk. Conclusions: Mineral composition of milk can influence postprandial serum AA kinetics, likely due to differences in coagulation dynamics. The clinical trial registry number is NL8959 (https://clinicaltrials.gov).

Evidence that carbohydrate-to-fat ratio and taste, but not energy density or NOVA level of processing, are determinants of food liking and food reward

This virtual (online) study tested the common but largely untested assumptions that food energy density, level of processing (NOVA categories), and carbohydrate-to-fat (CF) ratio are key determinants of food reward. Individual participants (224 women and men, mean age 35 y, 53% with healthy weight, 43% with overweight or obesity) were randomised to one of three, within-subjects, study arms: energy density (32 foods), or level of processing (24 foods), or CF ratio (24 foods). They rated the foods for taste pleasantness (liking), desire to eat (food reward), and sweetness, saltiness, and flavour intensity (for analysis averaged as taste intensity). Against our hypotheses, there was not a positive relationship between liking or food reward and either energy density or level of processing. As hypothesised, foods combining more equal energy amounts of carbohydrate and fat (combo foods), and foods tasting more intense, scored higher on both liking and food reward. Further results were that CF ratio, taste intensity, and food fibre content (negatively), independent of energy density, accounted for 56% and 43% of the variance in liking and food reward, respectively. We interpret the results for CF ratio and fibre in terms of food energy-to-satiety ratio (ESR), where ESR for combo foods is high, and ESR for high-fibre foods is low. We suggest that the metric of ESR should be considered when designing future studies of effects of food composition on food reward, preference, and intake.

Milk coagulation and gastric emptying in women experiencing gastrointestinal symptoms after ingestion of cow's milk

BACKGROUND

Gastrointestinal symptoms after drinking milk are often attributed to lactose intolerance or cow's milk allergy. However, some individuals without either condition still report gastrointestinal symptoms after drinking milk. This may be caused by gastric emptying (GE) rate or gastric protein coagulation. This study aimed to compare GE rate and protein coagulation after milk consumption between individuals reporting gastrointestinal symptoms and those without symptoms using a novel gastric MRI approach.

METHODS

Thirty women were included in this case-control study, of whom 15 reported gastrointestinal symptoms after drinking milk and 15 were controls. Participants underwent gastric MRI before and up to 90 min after consumption of 250 mL cow's milk. Gastric content volume and image texture of the stomach contents were used to determine GE and changes in the degree of coagulation.

KEY RESULTS

GE half-time did not differ between the groups (gastrointestinal symptom group 66 ± 18 min; control group 61 ± 14 min, p = 0.845). The gastrointestinal symptom group reported symptoms from 30 min onwards and rated pain highest at 90 min. The control group reported no symptoms. Image texture analyses showed a significantly higher percentage of coagulum and lower percentage of liquid in the group in the GI symptom group (MD 11%, 95% CI [3.9, 17], p = 0.003). In vitro data suggests that pH and proteolytic enzyme activity influence the coagulum structure.

CONCLUSIONS AND INFERENCES

Gastric milk coagulation and emptied fraction of stomach content may differ between individuals experiencing symptoms after milk consumption, possibly due to differences in pH and proteolytic enzyme activity.

Particle size and water content impact breakdown and starch digestibility of chickpea snacks during in vitro gastrointestinal digestion

Chickpeas are an agriculturally-important legume that are an excellent source of protein, fiber, and minerals. Developing chickpea-based snacks could provide consumers with snack products rich in protein and other nutrients. In this study, chickpea puree (high moisture content) and cracker (low moisture content) were each produced with large (7 mm sieve; coarse) or small (2 mm sieve; fine) particle size to investigate the impact of initial particle size and moisture content on particle breakdown, starch hydrolysis, and protein hydrolysis during in vitro digestion. All treatments underwent static in vitro oral digestion, dynamic gastric digestion in the Human Gastric Simulator (HGS), and static in vitro small intestinal digestion. The emptying rate from the HGS was significantly (p < 0.05) higher for fine puree compared to the other treatments, due to higher saturation ratio and smaller initial particle size. The reducing sugars and free amino groups released (representing starch and protein hydrolysis, respectively) from fine puree were higher than coarse puree, and fine cracker was higher than coarse cracker due to the influence of initial particle size. For example, after 360 min total in vitro digestion, the starch hydrolysis of the fine cracker (48.1 ± 3.2%) was significantly higher than (p < 0.05) the coarse cracker (36.3 ± 5.8%). Overall, crackers had higher protein and starch hydrolysis compared to puree in the liquid phase during digestion. The study showed that both the smaller initial particle size and drying significantly (p < 0.05) increased the particle size reduction during gastric digestion and starch and protein digestibility in chickpea-based snacks.

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.

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.

Evaluation of the performance of the human gastric simulator using durum wheat-based foods of contrasting food structure

The selection of gastric digestion parameters in food digestion studies using in vitro models is critical to properly represent structural changes in the stomach. This study aimed to evaluate the performance of digestion in the human gastric simulator (HGS) using generalized in vitro gastric digestion parameters (secretion rate of 4.1 mL min^-1, gastric emptying rate of 5.68 g min^-1) that were derived from a previous in vivo study using six starch-rich foods. Two of the six foods used in the in vivo study (cooked durum wheat porridge/semolina and pasta) were digested in the HGS for up to 240 min, then the properties of the emptied and remaining digesta were measured. The properties of the in vitro remaining digesta were compared to those measured in vivo (growing pig stomach). The trends in the gastric breakdown rate and mechanisms, dry matter emptying kinetics, and starch hydrolysis of pasta and semolina were similar to those of in vivo. Gastric breakdown and dilution kinetics in vitro and in vivo were well-related but did not have a 1 : 1 correlation, whereas gastric acidification kinetics in the HGS deviated from that observed in vivo. The results suggest that generalized digestion parameters could be used to predict the effect of food structure on in vivo gastric breakdown and emptying, but care should be taken in interpretation of results, as the gastric acidification process was different from what was observed in vivo. This information will help refine in vitro digestion model parameters to provide more physiologically-relevant data in future studies.

Impact of energy density on energy intake in children and adults: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The energy density (ED) of a diet can be leveraged to prevent weight gain or treat overweight and obesity. By lowering the ED of the diet, energy intake can be reduced while maintaining portion size. However, a reliable meta-analysis of data from randomized controlled trials (RCTs) is missing. Therefore, this meta-analysis synthesized the evidence of ED manipulation on energy intake in RCTs.

METHODS

The systematic literature search of multiple databases according to PRISMA criteria considered RCTs investigating the objectively measured energy intake from meals with different ED (lower ED (median 1.1 kcal/g) versus higher ED (median 1.5 kcal/g)) under controlled conditions. Subgroup analyses for age (children versus adults), meal type (preload versus entrée design), and intervention length (1 meal versus > 1 meal) were performed to achieve the most homogeneous result.

RESULTS

The meta-analysis of 38 included studies demonstrated that lowering ED considerably reduced energy intake - 223 kcal (95% CI: - 259.7, - 186.0) in comparison to the higher ED interventions. As heterogeneity was high among studies, subgroup analyses were conducted. Heterogeneity decreased in subgroup analyses for age and meal type combined, strengthening the results. An extended analysis showed a positive linear relationship between ED and energy intake. Dietary ED did not affect the amount of food intake.

CONCLUSION

Manipulating ED substantially affects energy intake whereas food intake remains constant. Thus, this approach can be regarded as a powerful tool for weight management through nutrition therapy. Registration on 08/08/2021: CRD42021266653.

Apple versus chocolate: Evidence for discrimination of distension-related and calorie-related satiety signals in post-prandial fullness and hunger, and in the quality and location of other body sensations

Gastric distension and detection of macronutrients (calories) in the gut are determinants of satiation and satiety. We tested effects of these variables on body sensations after eating, and their connection with visual-analogue scale (VAS) hunger and fullness ratings. Participants completed VAS ratings and quality and location of body sensations tasks after consumption of milk chocolate (38 g, 200 kcal) versus fresh apple fruit matched for weight (38 g, 20 kcal) and matched for calories (380 g, 200 kcal). Effects of food weight (380 vs 38 g) were large and located predominantly in the abdominal region. They also occupied a greater body area and occurred sooner after eating than effects related to calories (200 vs 20 kcal). The same pattern was apparent in the results from the quality of sensations task. VAS ratings indicated that hunger was affected by food volume and calories, whereas fullness was affected primarily by food volume. Together, these results provide evidence of dissociation of the perceived after-effects of food ingestion related to food volume and food calorie content in humans. Additionally, the studies demonstrate the utility of two rarely used, semi-quantitative tasks, which generate information on the identity, intensity, valence, and location of eating-related sensations.

A novel MRI-based three-dimensional model of stomach volume, surface area, and geometry in response to gastric filling and emptying

BACKGROUND

Gastric motility and accommodation have a critical role in maintaining normal gastrointestinal homeostasis. Different modalities can be adopted to quantify those processes, that is, scintigraphy to measure emptying time and intragastric Barostat for accommodation assessment. However, magnetic resonance imaging (MRI) can assess the same parameters noninvasively without ionizing radiation. Our study aimed to develop a detailed three-dimensional (3D) MRI model of the stomach to describe gastric volumes, surface areas, wall tension distribution, and interobserver agreement.

METHODS

Twelve healthy volunteers underwent an MRI protocol of six axial T2-weighted acquisitions. Each dataset was used to construct a 3D model of the stomach: First, the volumes of the whole stomach, gastric liquid, and air were segmented. After landmark placing, a raw 3D model was generated from segmentation data. Subsequently, irregularities were removed, and the model was divided into compartments. Finally, surface area and 3D geometry parameters (inverse curvatures) were extracted. The inverse curvatures were used as a proxy for wall tension distribution without measuring the intragastric pressure.

KEY RESULTS

The model was able to describe changes in volume and surface geometry for each compartment with a distinct pattern in response to filling and emptying. The surface tension was distributed nonhomogeneously between compartments and showed dynamical changes at various time points.

CONCLUSION & INFERENCES

The presented model offers a detailed tool for evaluating gastric volumes, surface geometry, and wall tension in response to filling and emptying and will provide insights into gastric emptying and accommodation in diseases such as diabetic gastroparesis.

Quantification of gastric emptying with magnetic resonance imaging in healthy volunteers: A systematic review

BACKGROUND

Several magnetic resonance imaging (MRI) protocols have been used to assess gastric emptying (GE) with MRI. This systematic review summarizes the current literature on the topic. The aim was to provide an overview of the available imaging protocols and underline the items that appear most agreed upon and those that deserve further investigation.

METHODS

According to PRISMA guidelines, two independent reviewers conducted a systematic literature search with a pre-specified strategy in different databases. Peer-reviewed articles that utilized MRI techniques to assess GE in healthy volunteers (HVs) were included. The quality and the outcomes of the studies were reported and analyzed.

KEY RESULTS

The literature search yielded 30 studies (531 HVs, weighted mean age 27.4, weighted mean body mass index 23.0 kg/m² ), T2-weighted sequences, balanced turbo field echo, and balanced gradient echo were evenly utilized, with volunteers in the supine position (74% of the studies). After overnight fasting, both liquid (56%) and mixed (44%) meals were equally utilized. Segmentation of the volumes was predominantly performed manually (63%) with a reported mean T50 ranging from 7 to 330 min.

CONCLUSIONS & INFERENCES

As observed in this systematic review, MRI is a flexible tool for assessing GE. Different protocols were analyzed, showing an equal capacity to assess the GE. However, many items in these protocols still require further investigation to obtain a common standard and increase this assessment quality.

Small bowel water content assessed by MRI in health and disease: a collation of single-centre studies

BACKGROUND

New developments in MRI have allowed the non-invasive, accurate measurement of the small bowel water content (SBWC).

AIMS

To collate studies measuring SBWC following ingestion of a range of foods in both health and disease to provide data for adequately powering future studies in this area.

METHODS

This collation brings together 29 studies including 954 participants (530 healthy, 54 diverticulosis, 255 IBS, 53 functional constipation, 12 cystic fibrosis, 15 Crohn's disease, 20 coeliac disease, 15 scleroderma) which have been carried out in a single centre using comparable study designs.

RESULTS

Fasting SBWC (mean 82 [SD 65] mL) shows high variability with a small decline with advancing age (healthy volunteers only; individual patient data). Fasting values are increased in untreated coeliac disease (202 [290] mL, P = 0.004). Post-prandial SBWC shows less intra-individual variability than fasting values in healthy volunteers. SBWC is increased by eating, most markedly by high fat meals but also by fibre, both viscous and particulate. Indigestible residue accumulates in late post-prandial period but empties soon after ingestion of a high calorie meal which produces a significant drop (by 50 [52] mL) in healthy volunteers. The associated fall in SBWC is abnormal in people with cystic fibrosis (SBWC reduced by 10 [121] mL, P = 0.002) and in people with irritable bowel syndrome with diarrhoea (SBWC reduced by 17 [43] mL, P = 0.007).

CONCLUSIONS

SBWC as assessed by MRI is a valuable biomarker indicating the balance of secretion and absorption in health and disease and the impact of treatments.

Size and Number of Food Boluses in the Stomach after Eating Different Meals: Magnetic Resonance Imaging Insights in Healthy Humans

Oral processing of food results in the formation of food boluses, which are then swallowed and reach the stomach for further digestion. The number, size and surface properties of the boluses will affect their processing and emptying from the stomach. Knowledge of these parameters, however, is incomplete due to limitations of the techniques used. In this work, non-invasive magnetic resonance imaging (MRI) was used for the first time to measure boluses in the stomach a few minutes after swallowing. Three groups of nine healthy participants were fed three different meals: chicken and roasted vegetables (Meal 1), bread and jam (Meal 2) and cheese and yogurt (Meal 3), and then, their stomach content was imaged. The median number of boluses within the stomach was 282, 106 and 9 for Meal 1, Meal 2 and Meal 3 (p < 0.0001) with an average volume of 0.47 mL, 2.4 mL and 13.6 mL, respectively (p < 0.0001). The cohesiveness as well as the meal composition seem to play a key role in the resulting boluses. These new in vivo data from undisturbed organ imaging can improve knowledge of the digestion process, which will, in turn, inform in vitro and in silico modelling of digestion, thus improving their in vitro/in vivo relevance.

Gastric Emptying and Intragastric Behavior of Breast Milk and Infant Formula in Lactating Mothers

BACKGROUND

When sufficient breast milk is not available, infant formula is often used as an alternative. As for digestion, gastric behavior of infant formula and breast milk have not been studied in detail.

OBJECTIVE

This study aimed to compare gastric emptying and intragastric behavior between breast milk and infant formula in vivo using MRI.

METHODS

In this randomized crossover study, 16 lactating mothers (age: 31.7 ± 2.9 y; time since giving birth: 9.3 ± 2 mo), underwent gastric MRI scans before and after consumption of 200 mL of infant formula or their own breast milk. MRI scans were performed after an overnight fast (baseline) and every 10 min up until 60 min following ingestion. Primary outcomes were gastric emptying measures and the secondary outcome was gastric layer volume over time. Differences between infant formula and breast milk in total gastric volume and layering volume were tested using linear mixed models.

RESULTS

Gastric emptying half-time was 5.1 min faster for breast milk than for infant formula (95% CI: -19.0 to 29.2) (n = 14). Within a subgroup (n = 12) with similar initial gastric volume (<20 mL difference), gastric emptying half-time was 20 min faster for breast milk (95% CI: 1.23-43.1). Top layer volume (n = 16) was 6.4 mL greater for infant formula than for breast milk (95% CI: 1.9-10.8). This effect is driven by t = 10 and t = 20 min postingestion.

CONCLUSIONS

When taking initial gastric volume into account, breast milk emptied faster than infant formula in women, which is in line with previous findings in infants. Infant formula showed a significantly larger top layer volume in the first 20 min after ingestion. MRI in adults may find application in studies assessing gastric behavior of infant formula.

Protein acidification and hydrolysis by pepsin ensure efficient trypsin-catalyzed hydrolysis

Enzyme-catalysed hydrolysis is important in protein digestion. Protein hydrolysis is initiated by pepsin at low pH in the stomach. However, pepsin action and acidification happen simultaneously to gastric emptying, especially for liquid meals. Therefore, different extents of exposure to the gastric environment change the composition of the chyme that is emptied from the stomach into the small intestine over time. We assessed the susceptibility of a protein to trypsin-catalysed hydrolysis in the small intestine, depending on its pH and hydrolysis history, simulating chyme at different times after the onset of gastric emptying. Isothermal titration calorimetry was used to study the kinetics of pepsin and trypsin-catalysed hydrolysis. Bovine serum albumin (BSA) that was acidified and hydrolysed with pepsin, showed the highest extent and most efficient hydrolysis by trypsin. BSA in the chyme that would be first emptied from the stomach, virtually bypassing gastric acidity and peptic action, reduced trypsin-catalysed hydrolysis by up to 58% compared to the acidified, intact protein, and 77% less than the acidified, pepsin-hydrolysate. The least efficient substrate for trypsin-catalysed hydrolysis was the acidified, intact protein with a specificity constant (k_cat/K_m) nearly five times lower than that of the acidified, pepsin-hydrolysate. Our results illustrate the synergy between pepsin and trypsin hydrolysis, and indicate that gastric hydrolysis increases the efficiency of the subsequent trypsin-catalysed hydrolysis of a model protein in the small intestine.

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.

Effects of Oro-Sensory Exposure on Satiation and Underlying Neurophysiological Mechanisms-What Do We Know So Far?

The mouth is the first part of the gastrointestinal tract. During mastication sensory signals from the mouth, so-called oro-sensory exposure, elicit physiological signals that affect satiation and food intake. It has been established that a longer duration of oro-sensory exposure leads to earlier satiation. In addition, foods with more intense sweet or salty taste induce earlier satiation compared to foods that are equally palatable, but with lower taste intensity. Oro-sensory exposure to food affects satiation by direct signaling via the brainstem to higher cortical regions involved in taste and reward, including the nucleus accumbens and the insula. There is little evidence that oro-sensory exposure affects satiation indirectly through either hormone responses or gastric signals. Critical brain areas for satiation, such as the brainstem, should be studied more intensively to better understand the neurophysiological mechanisms underlying the process of satiation. Furthermore, it is essential to increase the understanding of how of highly automated eating behaviors, such as oral processing and eating rate, are formed during early childhood. A better understanding of the aforementioned mechanisms provides fundamental insight in relation to strategies to prevent overconsumption and the development of obesity in future generations.

A semi dynamic in vitro digestion study of milk protein concentrate dispersions structured with different polysaccharides

Hydrocolloids are often added as functional ingredients in foods, to better design the structure of the matrix and ensure food quality and optimal sensory properties. However, much less is known about their influence on the physical and chemical changes during gastric digestion. In this study, semi-continuous in vitro gastric digestion was applied on a model food system, prepared with milk protein concentrate (MPC) (3% w/v) and 1% alginate, pectin, guar gum, as well as a 1:1 mixture of alginate and pectin. The dynamics during simulated gastric digestion were observed by measuring particle size distributions, structuring at various length scales, as well as by evaluating differences in protein breakdown. Immediately after contact with the simulated gastric fluids, all samples showed extensive aggregation and formation of different structures. MPC control dispersions (no polysaccharide) and MPC containing alginate formed large inhomogeneous aggregates. The lack of structural homogeneity affected the simulated gastric emptying: there were marked differences in the type of aggregates present at various times of emptying depending on the hydrocolloid present in the mixture. MPC containing pectin or guar gum formed macroscopically homogeneous dispersion, with rather small protein aggregates showing a large population of particles between 60 and 100 ​μm of diameter, with marked differences in microstructure. Pectin created large coacervates, while guar microscopic phase separated systems. These dispersions showed a higher extent of protein digestion, due to the larger surface area created for enzyme activity compared to the macroscopically phase separated matrices. In all cases, there was a large undigested fraction at the end point of 140 ​min. SDS PAGE demonstrated differences in the casein peptides distribution depending on the type of polysaccharide present during simulated gastric emptying. This in spite of similarities in cumulative protein emptied. It was concluded that in this semi-continuous in vitro gastric digestion model, structuring with polysaccharides has a significant impact on gastric emptying and protein digestion kinetics.

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Protein-hydrocolloid interactions cause differences in structuring during gastrointestinal transit.

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Milk protein concentrates show different proteolysis kinetics during gastric digestion depending on aggregates formed.

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Milk protein concentrates with alginates show a delay in digestion.

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Pectin and guar form homogenous dispersions during gastric digestion.

Processing Apples to Puree or Juice Speeds Gastric Emptying and Reduces Postprandial Intestinal Volumes and Satiety in Healthy Adults

BACKGROUND

Whole apples produce greater satiety than processed apples, but the underlying mechanisms remain unclear.

OBJECTIVE

Our aim was to assess the intragastric processing of apple preparations and the associated small and large bowel contents using MRI.

METHODS

An open label, 3-way crossover, randomized, controlled trial. Eighteen healthy adults (mean ± SD age, 25 ± 4 y; BMI, 22.7 ± 3.5 kg/m2) underwent serial MRI scans on 3 occasions separated by 7 d, after consumption of isocaloric (178 kcal) portions of either whole apples, apple puree, or apple juice. Gastric emptying, small bowel water content (SBWC; primary endpoint), were measured at baseline and at 45 min intervals (0-270 min) postmeal ingestion. Fullness and satiety were also assessed at each time point. Treatment effects between groups were analyzed using ANOVA.

RESULTS

Gastric emptying half-time (GE t50) was greater (P < 0.0001) after participants consumed whole apple (mean ± SEM), 65 (3.3) min compared with when they consumed apple puree (41 [2.8] min) or apple juice (38 [2.9] min), times that did not differ. Postprandial area under the curve (AUC) (135-270 min) SBWC was also greater for whole apples than puree (P = 0.025) and juice (P = 0.0004) but juice and puree did not differ. AUC for fullness and satiety (0-270 min) postingestion was also greater (P = 0.002 and 0.004, respectively) for whole apple compared with juice but juice and puree did not differ.

CONCLUSIONS

Gastric emptying is slower after whole apple consumption causing a greater sensation of fullness and satiety than puree or juice in healthy adults. Whole apples increased small bowel and colonic contents during the later phase of the study which may be relevant for subsequent food consumption.This study was registered at clinicaltrials.gov as NCT03714464.

Monitoring food digestion with magnetic resonance techniques

This review outlines the current use of magnetic resonance (MR) techniques to study digestion and highlights their potential for providing markers of digestive processes such as texture changes and nutrient breakdown. In vivo digestion research can be challenging due to practical constraints and biological complexity. Therefore, digestion is primarily studied using in vitro models. These would benefit from further in vivo validation. NMR is widely used to characterise food systems. MRI is a related technique that can be used to study both in vitro model systems and in vivo gastro-intestinal processes. MRI allows visualisation and quantification of gastric processes such as gastric emptying and coagulation. Both MRI and NMR scan sequences can be configured to be sensitive to different aspects of gastric or intestinal contents. For example, magnetisation transfer and chemical exchange saturation transfer can detect proton (1H) exchange between water and proteins. MRI techniques have the potential to provide molecular-level and quantitative information on in vivo gastric (protein) digestion. This requires careful validation in order to understand what these MR markers of digestion mean in a specific digestion context. Combined with other measures they can be used to validate and inform in vitro digestion models. This may bridge the gap between in vitro and in vivo digestion research and can aid the optimisation of food properties for different applications in health and disease.

Food texture influences on satiety: systematic review and meta-analysis

Obesity is one of the leading causes of preventable deaths. Development of satiety-enhancing foods is considered as a promising strategy to reduce food intake and promote weight management. Food texture may influence satiety through differences in appetite sensations, gastrointestinal peptide release and food intake, but the degree to which it does remains unclear. Herein, we report the first systematic review and meta-analyses on effects of food texture (form, viscosity, structural complexity) on satiety. Both solid and higher viscous food reduce hunger by − 4.97 mm (95% confidence interval (CI) − 8.13, − 1.80) and − 2.10 mm (95% CI − 4.38, 1.18), respectively compared to liquid and low viscous food. An effect of viscosity on fullness (95% CI 5.20 (2.43, 7.97) and a moderate effect of the form of food (95% CI − 26.19 (− 61.72, − 9.35) on food intake were noted. Due to the large variation among studies, the results should be interpreted cautiously and modestly.

Effects of Laparoscopic Sleeve Gastrectomy on Gastric Structure and Function Documented by Magnetic Resonance Imaging Are Strongly Associated with Post-operative Weight Loss and Quality of Life: a Prospective Study

BACKGROUND

This prospective study applied magnetic resonance imaging (MRI) to assess the effect of laparoscopic sleeve gastrectomy (LSG) on gastric structure and function. The impact of these changes on patient outcomes was analyzed.

METHOD

Obese patients without gastrointestinal symptoms referred for bariatric surgery were recruited prospectively. Pre-operative assessment included (i) high-resolution manometry and pH-impedance monitoring and (ii) magnetic resonance imaging (MRI) measurement of gastric capacity, accommodation, and emptying with the 400 ml liquid Nottingham test meal (NTM). Studies were repeated 6-7 months after LSG. Weight loss and changes in the Gastrointestinal Quality of Life Index (GIQLI) assessed patient outcomes.

RESULTS

From 35 patients screened, 23 (66%) completed the study (17 females, age 36 ± 10 years, BMI 42 ± 5 kg/m2). Mean excess weight loss was 59 ± 18% at follow-up. Total gastric volume (capacity) after the meal was 467 mL (455-585 ml) before and 139 mL (121-185 ml) after LSG (normal reference 534 (419-675) mL), representing a mean 70% reduction (p < 0.0001). Similar findings were present for gastric content volume indicating rapid early-phase gastric emptying (GE) post-LSG. Conversely, late-phase GE was slower post-LSG (2.5 ± 1.0 vs. 1.4 ± 0.6 mL/min; p < 0.0001; (reference 1.5(1.4-4.9) mL/min)). Patients with ≥ 80% reduction in gastric capacity had greater weight loss (p = 0.008), but worse gastrointestinal outcomes (p = 0.023).

CONCLUSIONS

MRI studies quantified the marked reduction in gastric capacity after LSG. The reduction in capacity was associated with rapid early- but slow late-phase GE after surgery. These changes were associated with weight loss; however, reductions in gastric capacity ≥ 80% were linked to increased acid reflux and impacted on gastrointestinal quality of life.

The effects of pre-meal drink volume on gastric motility and energy intake in healthy men

Pre-meal drink ingestion is an effective method of controlling energy intake in humans. However, no studies have addressed the influence of differences in the volume of drink intake on gastric motility and energy intake. The purpose of the present study was to examine the effects of differences in the volume of drink intake before a meal on subsequent gastric motility and energy intake in healthy young men. Twelve men completed two, one-day trials in a random order. Subjects visited the laboratory after a 10-h overnight fast and consumed the nutrient drink (0.84 MJ) in either 100 mL or 600 mL quantities over a 5-min period. Then, the subjects sat on a chair for over 2 h to measure their cross-sectional gastric antral areas and gastric contractions with an ultrasound imaging system. Thereafter, the subjects consumed a test meal until they felt completely full. Energy intake was calculated from the amount of food consumed. Energy intake in the 600 mL trial was 12% higher than the 100 mL trial (5.1 ± 1.3 vs. 4.6 ± 1.4 MJ, P = 0.046). The antral area (P = 0.046) and the frequency of the gastric contraction (P = 0.001) over 2 h after consuming the nutrient drink were higher in the 600 mL trial than the 100 mL trial. These findings demonstrated that consumption of a 600 mL nutrient drink increased energy intake. The modulation of gastric motility might have some effects on energy intake.

Altered circulating endocannabinoids in anorexia nervosa during acute and weight-restored phases: A pilot study

Anorexia nervosa (AN) is an eating disorder characterized by a low food intake and often exceeding exercise, leading to a particularly low body × weight proportion. Patients with AN usually report less hunger than healthy controls. Endogenous endocannabinoids (eCBs), specifically the anandamide, have been associated to hunger, as a meal initiator, but research regarding AN and eCB and inconclusive. In this pilot study, we investigated plasma levels of eCB in inpatients with AN during fasting and after eating, both during the acute AN phase and after weight recovery. After an 8-hr fasting period, blood sample was collected from all participants. After that, participants were given a muffin test meal. Blood samples for the investigation of endogenous eCBs anandamide (N-arachidonoylethanolamide [AEA]) and 2-arachidonoylglycerol (2-AG) were then collected after 120 and 240 min. Participants were only allowed to eat and drink what was offered them during the research. AN reported less hunger than controls during fasting and at the end of the experiment. Also, plasma levels of AEA were significantly smaller in AN in comparison with controls in all time points. No significant difference was found for 2-AG plasma levels. After recovery, no significant difference was found for eCB levels. These findings could be interpreted as an AEA deregulation in AN before and after food intake, which persists after weight recovery. These findings may have implications to the pharmacological treatment of AN and to relapse occurring in the disorder.

Food Intake and Satiety Response after Medium-Chain Triglycerides Ingested as Solid or Liquid

Consuming medium-chain triglycerides (MCT) may reduce subsequent energy intake and increase satiety compared to long-chain triglycerides (LCT) but this may be dependent on the physical form in which MCT is ingested. Twenty-nine participants completed four trials where they consumed a breakfast containing either LCT or MCT in solid (Con-S and MCT-S, respectively) or liquid (Con-L and MCT-L, respectively) form. Appetite ratings and gastric emptying (GE) were taken at baseline and at 15 min intervals for 4 h. Energy intake was assessed at an ad libitum meal and via weighed food records for the remainder of the day. Ad libitum energy intake was highest in Con-L (4101 ± 1278 kJ vs. Con-S, 3323 ± 1196; MCT-S, 3516 ± 1058; MCT-L, 3257 ± 1345; p = 0.001). Intake over the whole day was significantly lower in MCT-L (7904 ± 3244) compared to Con-L (9531 ± 3557; p = 0.001). There were significant differences in GE times (p < 0.05), with MCT breakfasts delaying GE to a greater extent than LCT, and MCT-L having the longest GE times. There were no differences in appetite sensations. MCT reduce subsequent intake without affecting subjective sensations of appetite when consumed in liquid form.

Intraluminal Impact of Food: New Insights from MRI

Understanding how the gut responds to food has always been limited by the available investigatory techniques. Previous methods involving intubation and aspiration are largely limited to liquid-only meals. The aim of this review is to describe how MRI has allowed analysis of the processing of complex multiphase meals. This has demonstrated the role of physical factors such as viscosity, fat and fibre content in controlling gastric secretion and motility. It has also allowed the description of changes induced in small bowel water content and the role of osmotic effects of poorly absorbed carbohydrates such as fructose, sorbitol and mannitol. Intestinal secretions can be shown to be stimulated by a range of fruit and vegetables and the effect of this on colonic water content can also be measured. This has been used to demonstrate the mode of action of commonly used laxatives including bran and psyllium. The wealth of data which can be obtained together with its non-invasive nature and safety makes the technique ideal for the serial evaluation of the impact of different nutrients and drugs in both health and disease.

The influence of a fruit smoothie or cereal and milk breakfast on subsequent dietary intake: a pilot study

Smoothies are popular breakfast foods. This study examined the effect of consuming Cereal & Milk (CM) or a nutritionally-comparable Fruit Smoothie (FS) for breakfast on daily energy intake (EI) in free-living adults and the extent to which individuals compensated for calories ingested in a High Energy Fruit Smoothie (HE). Ten participants (28.4 ± 2.2y; 23.3 ± 1.0 kg·m ^-2, Mean ± SEM) attended the laboratory on 3 consecutive days per week for 3 weeks. Each week, they received a CM, FS or HE breakfast, then recorded all food/beverages consumed across the remainder of the day. The CM and FS were energy-matched to participants' usual breakfast (1675 ± 283 kJ), while the HE contained an additional 100 kJ·kg^-1 of maltodextrin (3019 ± 335 kJ). Mean 3-day EI was similar on CM and FS (7894 ± 547 vs. 7570 ± 463 kJ, p > .05), but elevated on HE (8861 ± 726 kJ, p =  .012). Thus, individuals who substitute CM for a FS breakfast should be mindful that energy-dense beverages may result in increased daily EI.

Food vs money? Effects of hunger on mood and behavioral reactivity to reward in anorexia nervosa

BACKGROUND

Previous studies using neuroimaging and behavioral measures reported altered reward processing in anorexia nervosa (AN). In addition, anhedonia states are frequently reported in AN, potentially due to the physiological stress produced by the permanent starvation. We investigated the effect of fasting and satiety on mood and reaction times to monetary rewards in AN patients and healthy controls.

METHODS

Twenty-four participants with acute AN (BMI 14.4 (11.9-15.5) Kg/m²) and 17 age and gender matched healthy, normal weight subjects (HW) (BMI 21.8 (18.9-24.9) Kg/m²) performed a reward task (the wheel of fortune) involving uncertain (50/50 probability of winning high and low rewards), safe and risky (30/70 and 10/90 probabilities) categories in fasted (after an 8-h fasting period) and fed (after intake of a standardized meal) states. Data analysis was done with linear mixed models.

RESULTS

AN reacted slower than HW when maximum uncertainty (50/50) was involved. Positive mood in response to winning was higher when fasting especially for HW, while negative mood in response to not winning was higher in the fed state for both groups. Still, HW were more reactive than AN to not winning a highly predictable monetary reward (10/90 safe).

CONCLUSION

The data on the reaction times indicate an impaired motor response to uncertainty in AN. Mood reactivity to winning a monetary reward does not seem to be impaired in AN, however, our results suggest that negative mood in response to not winning is less adaptive in AN. Implications to clinical psychotherapy are discussed.

Gastric motor and sensory function in health assessed by magnetic resonance imaging: Establishment of reference intervals for the Nottingham test meal in healthy subjects

BACKGROUND

Current investigations of gastric emptying rarely identify the cause of symptoms or provide a definitive diagnosis in patients with dyspepsia. This study assessed gastric function by magnetic resonance imaging (MRI) using the modular "Nottingham test meal" (NTM) in healthy volunteers (HVs).

METHODS

The NTM comprises (a) 400 mL liquid nutrient (0.75 kcal/mL) labeled with Gadolinium-DOTA and (b) an optional solid component (12 agar-beads [0 kcal]). Filling sensations were documented. MRI measurements of gastric volume, emptying, contraction wave frequency, and secretion were obtained using validated methods.

KEY RESULTS

Gastric function was measured in a population of 73 HVs stratified for age and sex. NTM induced moderate satiety and fullness. Labeled fluid was observed in the small bowel in all subjects after meal ingestion ("early-phase" GE). Secretion was rapid such that postprandial gastric content volume was often greater than meal volume (GCV0 > 400 mL), and there was increasing dilution of the meal during the study (P < 0.001). Gastric half-time was median 66-minutes (95% reference interval 35 to 161-minutes ["late-phase" GE]). The number of intact agar beads in the stomach was 7/12 (58%) at 60-minutes and 1/12 (8%) at 120-minutes. Age, bodyweight and sex had measurable effects on gastric function; however, these were small compared to inter-individual variation for most metrics.

CONCLUSIONS AND INFERENCES

Reference intervals are presented for MRI measurements of gastric function assessed for the mixed liquid/solid NTM. Studies in patients will determine which metrics are of clinical value and also whether the reference intervals presented here offer optimal diagnostic sensitivity and specificity.

Just add water: Effects of added gastric distention by water on gastric emptying and satiety related brain activity

BACKGROUND

Gastric distention contributes to meal termination. There is little research on the neural correlates of gastric distention by food. To date, neural measures have not been obtained concurrently with measurements of gastric distention.

OBJECTIVES

1) To study how offering a small versus a large water load following a standardized nutrient load affects gastric distention over time. 2) To assess associations between satiety experiences and brain activity and the degree of gastric distention.

METHOD

19 healthy males (age 22.2 ± 2.5 y, BMI 21.8 ± 1.5 kg/m²) participated in a randomized crossover study with two treatments: ingestion of a 500-kcal 150-mL liquid meal shake followed by a low (LV, 50 mL) or a high volume (HV, 350 mL) water load. At baseline and three times after ingestion satiety was scored, MRI scans were made to determine total gastric content volume (TGV) and functional MRI scans were made to measure cerebral blood flow (CBF).

RESULTS

TGV was significantly higher for HV compared to LV at all time points (p < 0.001) with relative differences between HV and LV of 292 ± 37 mL after ingestion, 182 ± 83 mL at t = 15 min and 62 ± 57 mL at t = 35 min. Hunger decreased (p = 0.023) and fullness increased (p = 0.030) significantly more for HV compared to LV. Ingestion increased CBF in the inferior frontal gyrus and the anterior insula, but there were no differences between treatments. There were no significant correlations between appetite ratings and CBF values.

CONCLUSION

Performing concurrent gastric MRI and CBF measurements can be used to investigate neural correlates of gastric distention. Increased distention did not induce significantly greater brain activation. Future research should further examine the role of the inferior frontal gyrus in satiety.

Lipid droplet size and emulsification on postprandial glycemia, insulinemia and lipidemia

Previous studies have suggested that a smaller lipid droplet size results in a greater rate of lipolysis. However, acute health impacts of emulsification and small lipid droplet size are not well understood. We aimed to investigate the effect of emulsification and lipid droplet size on postprandial lipidemia, glycemia and insulinemia. Fifteen healthy Chinese males (mean ± SD, age of 26 ± 6 years and BMI of 22.2 ± 1.2 kg m^-2) participated on 3 separate occasions in a randomized order. Participants received an olive oil-water beverage and white bread as test meals. The three test beverages were as follows: (1) an olive oil-water mixture (non-emulsified, control), (2) fine olive oil-water emulsion (small lipid droplet size) and (3) coarse olive oil-water emulsion (large lipid droplet size). Glucose, insulin, triglyceride, non-esterified fatty acid (NEFA), gastric antral distention and appetite measurements were recorded for 4 hours. Glucose and insulin concentrations increased rapidly after administration of non-emulsified beverages as compared to fine and coarse emulsions with a significant difference at 30 min (95% confidence interval, P < 0.05). Fine emulsion led to a significant increase in triglyceride responses, a smaller suppression of NEFA responses and slowed gastric emptying compared to the non-emulsified beverage and coarse emulsion (iAUC, 95% confidence interval, P < 0.05). Emulsification and alteration of lipid droplet size have acute effects on glucose, insulin, triglyceride and fatty acid responses.

MRI assessment of the postprandial gastrointestinal motility and peptide response in healthy humans

BACKGROUND

Feeding triggers inter-related gastrointestinal (GI) motor, peptide and appetite responses. These are rarely studied together due to methodological limitations. Recent MRI advances allow pan-intestinal, non-invasive assessment of motility in the undisturbed gut. This study aimed to develop a methodology to assess pan-intestinal motility and transit in a single session using MRI and compare imaging findings to GI peptide responses to a test meal and symptoms in a healthy volunteer cohort.

METHODS

Fifteen healthy volunteers (29.3±2.7 years and BMI 20.1±1.2 kg m^-2 ) underwent baseline and postprandial MRI scans, symptom questionnaires, and blood sampling (for subsequent GI peptide analysis, Glucagon-like peptide-1 [GLP-1], Polypeptide YY [PYY], Cholecystokinin [CCK]) at intervals for 270 minutes following a 400 g soup meal (204 kcal, Heinz, UK). Gastric volume, gall bladder volume, small bowel water content, small bowel motility, and whole gut transit were measured from the MRI scans.

KEY RESULTS

(mean±SEM) Small bowel motility index increased from fasting 39±3 arbitrary units (a.u.) to a maximum of 87±7 a.u. immediately after feeding. PYY increased from fasting 98±10 pg mL^-1 to 149±14 pg mL^-1 at 30 minutes and GLP-1 from fasting 15±3 μg mL^-1 to 22±4 μg mL^-1 . CCK increased from fasting 0.40±0.06 pmol mL^-1 to 0.94±0.1 pmol mL^-1 . Gastric volumes declined with a T_1/2 of 46±5 minute and the gallbladder contracted from a fasting volume of 19±2 mL^-1 to 12±2 mL^-1 . Small bowel water content increased from 39±2 mL^-1 to 51±2 mL^-1 postprandial. Fullness VAS score increased from 9±5 mm to 41±6 mm at 30 minutes postprandial.

CONCLUSIONS AND INFERENCES

The test meal challenge was effective in inducing a change in MRI motility end-points which will improve understanding of the pathophysiological postprandial GI response.

Glycaemic, gastrointestinal and appetite responses to breakfast porridges from ancient cereal grains: A MRI pilot study in healthy humans

Cereal grain based porridges are commonly consumed throughout the world. Whilst some data are available for varieties that are popular in the Western world such as oats and rye, other 'ancient' grains used in the East and in Africa such as millets are thought to have beneficial health effects, such as a suppression of post prandial hunger and circulating glucose levels. These grains, a sustainable food source due to their tolerance of extreme weather and growing conditions, are commonly found throughout Asia and Africa. However, knowledge of the physiological responses to these grain varieties is very limited. This study aimed to collect initial pilot data on the physiological and gastrointestinal responses to breakfast porridges made with two millet varieties and oats and rye grains. A total of n=15 completed the oats and rye, n=9 the finger millet n=12 the pearl millet meals. MRI scans were undertaken at baseline, immediately after consumption and then hourly postprandially. Blood glucose was measured at baseline, immediately after consumption and then every 15min until t=80min, then every 20min until t=120min, followed on each occasion by completion of VAS. Seven participants completed the entire protocol and were included in the final analysis. A subgroup analysis with the n=10 paired comparison between the same individuals that completed the oats, rye and pearl millet was also considered. The gastric volume AUC was higher for pearl millet than oats and rye (n=10, p<0.001). The incremental area under the curve (iAUC) for blood glucose was not significantly different between the meals although this showed a trend to be lower for pearl millet. Hunger was lower for pearl millet compared to oats and rye (n=10, p=0.01). There was a significant correlation between total gastric volume AUC and average appetite AUC r=-0.47, p<0.010. Isoenergetic breakfast porridges from 'ancient' varieties of millet grains showed physiological responses that were comparable with those from common Western varieties known to have beneficial health effects. Pearl millet appeared to induce lower postprandial blood glucose response and appetite scores though the differences were not conclusive compared with the other porridges and further work is needed. Improved knowledge of the effects of different cereal grains could help direct dietary advice and ultimately improve health outcomes in the general population worldwide.

Oatmeal particle size alters glycemic index but not as a function of gastric emptying rate

The aim of this study was to determine the extent to which oat particle size in a porridge could alter glucose absorption, gastric emptying, gastrointestinal hormone response, and subjective feelings of appetite and satiety. Porridge was prepared from either oat flakes or oat flour with the same protein, fat, carbohydrate, and mass. These were fed to eight volunteers on separate days in a crossover study, and subjective appetite ratings, gastric contents, and plasma glucose, insulin, and gastrointestinal hormones were determined over a period of 3 h. The flake porridge gave a lower glucose response than the flour porridge, and there were apparent differences in gastric emptying in both the early and late postprandial phases. The appetite ratings showed similar differences between early- and late-phase behavior. The structure of the oat flakes remained sufficiently intact to delay their gastric emptying, leading to a lower glycemic response, even though initial gastric emptying rates were similar for the flake and flour porridge. This highlights the need to take food structure into account when considering relatively simple physiological measures and offering nutritional guidance.NEW & NOTEWORTHY The impact of food structure on glycemic response even in simple foods such as porridge is dependent on both timing of gastric emptying and the composition of what is emptied as well as duodenal starch digestion. Thus structure should be accounted for when considering relatively simple physiological measures and offering nutritional guidance.

Dietary energy density: Applying behavioural science to weight management

Studies conducted by behavioural scientists show that energy density (kcal/g) provides effective guidance for healthy food choices to control intake and promote satiety. Energy density depends upon a number of dietary components, especially water (0 kcal/g) and fat (9 kcal/g). Increasing the proportion of water or water-rich ingredients, such as vegetables or fruit, lowers a food's energy density. A number of studies show that when the energy density of the diet is reduced, both adults and children spontaneously decrease their ad libitum energy intake. Other studies show that consuming a large volume of a low-energy-dense food such as soup, salad, or fruit as a first course preload can enhance satiety and reduce overall energy intake at a meal. Current evidence suggests that energy density influences intake through a complex interplay of cognitive, sensory, gastrointestinal, hormonal and neural influences. Other studies that focus on practical applications show how the strategic incorporation of foods lower in energy density into the diet allows people to eat satisfying portions while improving dietary patterns. This review discusses studies that have led to greater understanding of the importance of energy density for food intake regulation and weight management.

Gastric Mixing During Food Digestion: Mechanisms and Applications

Gastric mixing is a complex process that is governed by meal properties, such as food buffering capacity, physical properties, and the rate of breakdown as well as physiological factors, such as the rate of gastric secretions, gastric emptying, and gastric motility. Gastric mixing processes have been studied through the use of experimental and computational methods. Gastric mixing impacts the intragastric pH distribution and residence time in the stomach for ingested materials. Development of a fundamental understanding of the advective and diffusion processes and their roles in gastric mixing will be important in furthering our understanding of food breakdown, microbial survival, and drug dissolution during gastric digestion.

Relationship of body weight with gastrointestinal motor and sensory function: studies in anorexia nervosa and obesity

Background

Whether gastrointestinal motor and sensory function is primary cause or secondary effect of abnormal body weight is uncertain. Moreover, studies relating continuous postprandial sensations of satiation to measurable pathology are scarce. This work assessed postprandial gastrointestinal function and concurrent sensations of satiation across a wide range of body weight and after weight change.

Methods

Patients with anorexia nervosa (AN) and obesity (OB) were investigated in reference to normal weight controls (HC). AN were additionally investigated longitudinally. Gastric emptying, antral contractions and oro-cecal transit after ingestion of a solid meal were investigated by MRI and ¹³C-lactose-ureide breath test. The dependency of self-reported sensations of satiation on the varying degree of stomach filling during gastric emptying was compared between groups.

Results

24 AN (BMI 14.4 (11.9–16.0) kg/m²), 16 OB (34.9 (29.6–41.5) kg/m²) and 20 HC (21.9 (18.9–24.9) kg/m²) were studied. Gastric half-emptying time (t₅₀) was slower in AN than HC (p = 0.016) and OB (p = 0.007), and a negative association between t₅₀ and BMI was observed between BMI 12 and 25 kg/m² (p = 0.007). Antral contractions and oro-cecal transit were not different. For any given gastric content volume, self-reported postprandial fullness was greater in AN than in HC or OB (p < 0.001). After weight rehabilitation, t₅₀ in AN tended to become shorter (p = 0.09) and postprandial fullness was less marked (p < 0.01).

Conclusions

A relationship between body weight and gastric emptying as well as self-reported feelings of satiation is present. AN have slower gastric emptying and heightened visceral perception compared to HC and OB. Longitudinal follow-up after weight rehabilitation in AN suggests these abnormalities are not a primary feature, but secondary to other factors that determine abnormal body weight.

Trial registration

Registered July 20, 2009 at ClinicalTrials.gov (NCT00946816).

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-016-0560-y) contains supplementary material, which is available to authorized users.

Ghrelin, CCK, GLP-1, and PYY(3-36): Secretory Controls and Physiological Roles in Eating and Glycemia in Health, Obesity, and After RYGB

The efficacy of Roux-en-Y gastric-bypass (RYGB) and other bariatric surgeries in the management of obesity and type 2 diabetes mellitus and novel developments in gastrointestinal (GI) endocrinology have renewed interest in the roles of GI hormones in the control of eating, meal-related glycemia, and obesity. Here we review the nutrient-sensing mechanisms that control the secretion of four of these hormones, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine [PYY(3-36)], and their contributions to the controls of GI motor function, food intake, and meal-related increases in glycemia in healthy-weight and obese persons, as well as in RYGB patients. Their physiological roles as classical endocrine and as locally acting signals are discussed. Gastric emptying, the detection of specific digestive products by small intestinal enteroendocrine cells, and synergistic interactions among different GI loci all contribute to the secretion of ghrelin, CCK, GLP-1, and PYY(3-36). While CCK has been fully established as an endogenous endocrine control of eating in healthy-weight persons, the roles of all four hormones in eating in obese persons and following RYGB are uncertain. Similarly, only GLP-1 clearly contributes to the endocrine control of meal-related glycemia. It is likely that local signaling is involved in these hormones' actions, but methods to determine the physiological status of local signaling effects are lacking. Further research and fresh approaches are required to better understand ghrelin, CCK, GLP-1, and PYY(3-36) physiology; their roles in obesity and bariatric surgery; and their therapeutic potentials.