Dietary protein precipitation properties have effects on gastric emptying in healthy volunteers

Tolerability, gastric emptying patterns, and symptoms during the Nottingham Test Meal in 330 secondary care non-diabetic dyspeptic patients

BACKGROUND

Scintigraphy is used for overall assessment of gastric emptying. Adherence to an international consensus protocol is recommended to ensure quality; however, this has not been widely adopted because preparation of the "egg-beater" meal is inconvenient in clinical practice. In this report, we audit the tolerability and the results of gastric emptying scintigraphy with the 400 ml Tc-99 m-labeled liquid nutrient Nottingham Test Meal (NTM).

METHODS

Results from 330 consecutive adult, non-diabetic patients with dyspeptic symptoms referred for gastric scintigraphy were analyzed. Gastric half-emptying time (T50) and validated measurements of early- and late-phase gastric emptying were acquired. Postprandial sensations of fullness, bloating, heartburn, nausea, and epigastric pain were recorded using 100 mm visual analog scales (VAS) before and 0, 30, and 90 min after NTM ingestion. Results were compared with those previously obtained in healthy subjects.

KEY RESULTS

Almost all (98%) of the patients were able to consume the 400 ml NTM. Considering early- and late-phase gastric emptying, frequently observed patterns included normal early- with slow late-phase (25%) and fast early- with slow late-phase emptying (27%). Abnormal score of fullness and/ or dyspeptic symptoms were observed in 88% of dyspeptic patients. Abnormal fullness at T0 (after completed drink ingestion) was associated with slow late phase of gastric emptying, especially in women.

CONCLUSIONS

Gastric scintigraphy with the NTM is simple to perform and well tolerated. Whether the identified abnormal gastric emptying patterns could predict different treatment outcome in patients with functional dyspepsia is the subject of ongoing prospective studies.

Study on the Mechanism of the Blood-Glucose-Lowering Effect of Collagen Peptides from Sturgeon By-Products

In a previous study, we found that the collagen peptides prepared from the by-products of Bester sturgeon had an inhibitory effect on elevated blood glucose levels in a glucose tolerance test with ICR mice. In the present study, we examine the mechanism of the effect of sturgeon collagen peptides (SCPs) in detail. When glucose was orally administered to mice along with the SCPs, it was found that the glucose remained in the stomach for a longer time. In the above tests, the amount of glucose excreted in the feces of mice also increased. On the contrary, it was revealed that the SCPs have a dipeptidyl-peptidase-IV (DPP-IV) inhibitory ability in an in vitro test. In subsequent oral and intravenous glucose administration tests, glucagon-like peptide-1 (GLP-1) and insulin levels in the blood of mice were maintained at high levels. These results suggested the following three mechanisms: SCPs slow the rate of transportation of glucose from the stomach into the small intestine, resulting in delayed glucose absorption; SCPs suppress the absorption of glucose in the small intestine and excrete it from the body; SCPs inhibit DPP-IV in the blood and maintain a high GLP-1 level in blood, which in turn stimulates insulin secretion.

Circulating Branched Chain Amino Acid Concentrations Are Higher in Dairy-Avoiding Females Following an Equal Volume of Sheep Milk Relative to Cow Milk: A Randomized Controlled Trial

Background: Intolerances to bovine dairy are a motivating factor in consumers seeking alternate-or replacement-dairy beverages and foods. Sheep milk (SM) is an alternate dairy source, with greater protein, although similar amino acid composition compared to cow milk (CM). Studies are yet to address the appearance of circulating amino acids following consumption of SM, relative to CM, in humans. Objective: To clinically determine the appearance of branched chain amino acids, and other amino acids, in circulation in response to equal servings of SM and CM, in females who avoid dairy products. Design: In a double-blinded, randomized, cross-over trial, 30 self-described dairy avoiding females (20-40 years) drank 650 mL of SM or CM that were reconstituted from the spray dried powders (30 and 25 g in 180 mL water, respectively) on separate occasions, following an overnight fast. After reconstitution, the energy and protein provided by SM was higher than for CM (2,140 vs. 1,649 kJ; 29.9 vs. 19.4 g protein); content of branched chain amino acids (BCAAs) were 10.5 and 6.5 mg·mL-1, respectively. Blood samples were collected at fasting and at regular intervals over 5 h after milk consumption. Plasma amino acids were measured by HPLC. Results: 80% of subjects self-identified as lactose intolerant, and the majority (47%) "avoided drinking milk" "most of the time". SM resulted in greater plasma appearance of BCAAs at 60 min (641.1 ± 16.3 vs. 563.5 ± 14.4 μmol·L-1; p < 0.001) compared with CM. SM similarly resulted in elevated postprandial concentrations of the amino acids lysine, methionine, and proline, particularly at 240 min (time × milk interactions p = 0.011, 0.017, and p = 0.002, respectively). Postprandial increases in plasma alanine concentrations were sustained to 120 min after CM (time × milk interaction p = 0.001) but not after SM, despite greater quantities provided by SM. Conclusions: SM is a rich source of protein, and relative to CM, provides a greater quantity of BCAAs, with a corresponding elevation of the postprandial circulating BCAA response. SM is therefore a possible dairy alternative of benefit to those who need to increase total protein intake or for individuals with heightened protein requirements. Unique Identifier and Registry: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375324, identifier U1111-1209-7768.

How processing may affect milk protein digestion and overall physiological outcomes: A systematic review

Dairy is one of the main sources for high quality protein in the human diet. Processing may, however, cause denaturation, aggregation, and chemical modifications of its amino acids, which may impact protein quality. This systematic review covers the effect of milk protein modifications as a result of heating, on protein digestion and its physiological impact. A total of 5363 records were retrieved through the Scopus database of which a total of 102 were included. Although the degree of modification highly depends on the exact processing conditions, heating of milk proteins can modify several amino acids. In vitro and animal studies demonstrate that glycation decreases protein digestibility, and hinders amino acid availability, especially for lysine. Other chemical modifications, including oxidation, racemization, dephosphorylation and cross-linking, are less well studied, but may also impact protein digestion, which may result in decreased amino acid bioavailability and functionality. On the other hand, protein denaturation does not affect overall digestibility, but can facilitate gastric hydrolysis, especially of β-lactoglobulin. Protein denaturation can also alter gastric emptying of the protein, consequently affecting digestive kinetics that can eventually result in different post-prandial plasma amino acid appearance. Apart from processing, the kinetics of protein digestion depend on the matrix in which the protein is heated. Altogether, protein modifications may be considered indicative for processing severity. Controlling dairy processing conditions can thus be a powerful way to preserve protein quality or to steer gastrointestinal digestion kinetics and subsequent release of amino acids. Related physiological consequences mainly point towards amino acid bioavailability and immunological consequences.

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.

Digestive Responses to Fortified Cow or Goat Dairy Drinks: A Randomised Controlled Trial

Fortified milk drinks are predominantly manufactured from bovine (cow) sources. Alternative formulations include those prepared with hydrolysed bovine milk proteins or from alternate bovidae species, such as caprine (goat) milk. Currently, there is little data on protein digestive and metabolic responses following ingestion of fortified milk drinks. To examine the digestive and metabolic responses to commercially-available fortified milks, young adults (n = 15 males: 15 females), in a randomised sequence, ingested isonitrogenous quantities of whole cow-protein (WC), whole goat-protein (WG), or partially-hydrolysed whey cow-protein (HC), commercial fortified milks. Plasma amino acid (AA) and hormonal responses were measured at baseline and again at 5 h after ingestion. Paracetamol recovery, breath hydrogen, and subjective digestive responses were also measured. Postprandial plasma AA was similar between WC and WG, while AA appearance was suppressed with HC. Following HC, there was a negative incremental AUC in plasma branched-chain AAs. Further, HC had delayed gastric emptying, increased transit time, and led to exaggerated insulin and GLP-1 responses, in comparison to whole protein formulas. Overall, WC and WG had similar protein and digestive responses with no differences in digestive comfort. Contrastingly, HC led to delayed gastric emptying, attenuated AA appearance, and a heightened circulating insulin response.

Development and validation of a large, modular test meal with liquid and solid components for assessment of gastric motor and sensory function by non-invasive imaging

BACKGROUND

Current investigations of stomach function are based on small test meals that do not reliably induce symptoms and analysis techniques that rarely detect clinically relevant dysfunction. This study introduces the large 'Nottingham Test Meal' (NTM) for assessment of gastric motor and sensory function by non-invasive imaging.

METHODS

NTM comprises 400 mL liquid nutrient (0.75 kcal/mL) and 12 solid agar-beads (0 kcal) with known breaking strength. Gastric fullness and dyspeptic sensations were documented by 100 mm visual analogue scale (VAS). Gastric emptying (GE) were measured in 24 healthy volunteers (HVs) by gastric scintigraphy (GS) and magnetic resonance imaging (MRI). The contribution of secretion to gastric volume was assessed. Parameters that describe GE were calculated from validated models. Inter-observer agreement and reproducibility were assessed.

KEY RESULTS

NTM produced moderate fullness (VAS ≥30) but no more than mild dyspeptic symptoms (VAS <30) in 24 HVs. Stable binding of meal components to labels in gastric conditions was confirmed. Distinct early and late-phase GE were detected by both modalities. Liquid GE half-time was median 49 (95% CI: 36-62) min and 68 (57-71) min for GS and MRI, respectively. Differences between GS and MRI measurements were explained by the contribution of gastric secretion. Breaking strength for agar-beads was 0.8 N/m(2) such that median 25 (8-50) % intact agar-beads and 65 (47-74) % solid material remained at 120 min on MRI and GS, respectively. Good reproducibility for liquid GE parameters was present and GE was not altered by agar-beads.

CONCLUSIONS & INFERENCES

The NTM provided an objective assessment of gastric motor and sensory function. The results were reproducible and liquid emptying was not affected by non-nutrient agar-beads. The method is potentially suitable for clinical practice.

Crosslinking with transglutaminase does not change metabolic effects of sodium caseinate in model beverage in healthy young individuals

Background

Postprandial metabolic and appetitive responses of proteins are dependent on protein source and processing technique prior to ingestion. Studies on the postprandial effects of enzymatic crosslinking of milk proteins are sparse. Our aim was to study the effect of transglutaminase (TG)-induced crosslinking of sodium caseinate on postprandial metabolic and appetite responses. Whey protein was included as reference protein.

Methods

Thirteen healthy individuals (23.3 ± 1.1 y, BMI 21.7 ± 0.4 kg/m²) participated in a single-blind crossover design experiment in which the subjects consumed three different isovolumic (500 g) pourable beverages containing either sodium caseinate (Cas, 29 g), TG-treated sodium caseinate (Cas-TG, 29 g) or whey protein (Wh, 30 g) in a randomized order. Blood samples were collected at baseline and for 4 h postprandially for the determination of plasma glucose, insulin and amino acid (AA) concentrations. Gastric emptying (GE) was measured using the ¹³ C-breath test method. Appetite was assessed using visual analogue scales.

Results

All examined postprandial responses were comparable with Cas and Cas-TG. The protein type used in the beverages was reflected as differences in plasma AA concentrations between Wh and Cas, but there were no differences in plasma glucose or insulin responses. A tendency for faster GE rate after Wh was detected. Appetite ratings or subsequent energy intake did not differ among the protein beverages.

Conclusions

Our results indicate that the metabolic responses of enzymatically crosslinked and native sodium caseinate in a liquid matrix are comparable, suggesting similar digestion and absorption rates and first pass metabolism despite the structural modification of Cas-TG.

The effect of α- or β-casein addition to waxy maize starch on postprandial levels of glucose, insulin, and incretin hormones in pigs as a model for humans

BACKGROUND

Starch is a main source of glucose and energy in the human diet. The extent to which it is digested in the gastrointestinal tract plays a major role in variations in postprandial blood glucose levels. Interactions with other biopolymers, such as dairy proteins, during processing can influence both the duration and extent of this postprandial surge.

OBJECTIVE

To evaluate the effect of the addition of bovine α- or β-casein to waxy maize starch on changes in postprandial blood glucose, insulin, and incretin hormones [glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1)] in 30 kg pigs used as an animal model for humans.

DESIGN

Gelatinised starch, starch gelatinised with α-casein, and starch gelatinised with β-casein were orally administered to trained pigs (n = 8) at a level of 60 g of available carbohydrate. Pre- and postprandial glucose measurements were taken every 15 min for the first hour and every 30 min thereafter up to 180 min. Insulin, GIP, and GLP-1 levels were measured in plasma samples up to 90 min postprandial.

RESULTS

Starch gelatinised with α-casein had a significantly (p < 0.05) lower peak viscosity on pasting and resulted in significantly lower glucose release at 15, 30, and 90 min postprandial compared to starch gelatinised with β-casein. During the first 45-min postprandial, the area under the glucose curve (AUC) for starch gelatinised with α-casein was significantly (p < 0.05) lower than that for starch gelatinised with β-casein. There was also a significant (p < 0.05) difference at T30 in GIP levels in response to the control compared to starch gelatinised with α- or β-casein. Significant (p < 0.05) increases in several free amino acid concentrations were observed on ingestion of either α- or β-casein gelatinised with starch at 30 and 90 min postprandial compared to starch alone. In addition, plasma levels of six individual amino acids were increased on ingestion of starch gelatinised with α-casein compared to ingestion of starch gelatinised with β-casein.

CONCLUSION

The presence of casein fractions (α- or β-casein) in gelatinised waxy maize starch affects swelling characteristics, viscosity, and subsequent in vivo digestion as determined by glucose levels in blood postprandial.

Effects of protein quality on appetite and energy metabolism in normal weight subjects

OBJECTIVE

The purpose of this study was to compare the effects of consumption of different protein sources on food intake and energy expenditure in normal weight subjects.

SUBJECTS AND METHODS

Breakfast preparations (casein, soy protein, whey protein or control) were ingested during seven consecutive days. Appetite, food intake, and energy expenditure were assessed.

RESULTS

Casein consumption led to a lower energy intake than whey protein. There was lower energy intake on day 7 than on day 1 of the casein session. Soy protein preparations resulted in higher diet induced thermogenesis (DIT) than in control preparations. The respiratory quotient (RQ) obtained in the whey protein session was lower than the control and soy protein sessions.

CONCLUSION

These results suggest that the consumption of different protein types leads to distinct effects on satiety (casein), DIT (soy protein), and/or RQ (whey protein).

Camel's milk and gastric emptying

BACKGROUND & AIM

Gastric emptying is determined by food consistency, pH, osmolality, lipid and calorie content as well as the presence of different nutrients in the duodenal lumen. Control of gastric emptying is essential for ensuring optimal digestion. The present study tested the hypothesis that due to its different precipitation properties, gastric emptying of camel's milk may be quicker than that of bovine's milk with the same caloric and fat content.

METHODS

Gastric emptying was studied by a scintigraphic technique in a randomized, double blind fashion in 8 volunteers after drinking 450 mL of either cow's milk or camel's milk.

RESULTS

No differences in gastric emptying rates were found between the two types of milk. The percentage of retention of the meal after 60 min was 74.6+/-13.2% for cow's milk and 79.8+/-10.8% for camel's milk. The 50% emptying time (T(1/2)) was 131.8+/-37.4 min for cow's milk and 136.8+/-55.8 min for camel's milk.

CONCLUSIONS

Camel's milk is most probably not a useful substitute for other types of milk to shorten gastric emptying.