Effects of a protein preload on gastric emptying, glycemia, and gut hormones after a carbohydrate meal in diet-controlled type 2 diabetes

Nocturnal whey protein ingestion impairs post-prandial glucose tolerance at breakfast

Poor post-prandial glucose control is a risk factor for multiple health conditions. The second-meal effect refers to the progressively improved glycaemic control with repeated feedings, an effect which is achievable with protein ingestion at the initial eating occasion. The most pronounced glycaemic response each day therefore typically occurs following breakfast, so the present study investigated whether ingesting protein during the night could improve glucose control at the first meal of the day. In a randomised crossover design, fifteen adults (seven males, eight females; age, 22 (sd 3) years; BMI, 24·0 (sd 2·8) kg/m2; fasting blood glucose, 4·9 (sd 0·5) mmol/l) woke at 04.00 (sd 1) hours to ingest 300 ml water with or without 63 g whey protein. Participants then completed a mixed-macronutrient meal tolerance test (1 g carbohydrate/kg body mass, 2356 (sd 435) kJ), 5 h 39 min following the nocturnal feeding. Nocturnal protein ingestion increased the glycaemic response (incremental AUC) to breakfast by 43·5 (sd 55·5) mmol × 120 min/l (P = 0·009, d = 0·94). Consistent with this effect, individual peak blood glucose concentrations were 0·6 (sd 1·0) mmol/l higher following breakfast when protein had been ingested (P = 0·049, d = 0·50). Immediately prior to breakfast, rates of lipid oxidation were 0·02 (sd 0·03) g/min higher (P = 0·045) in the protein condition, followed by an elevated post-prandial energy expenditure (0·38 (sd 0·50) kJ/min, P = 0·018). Post-prandial appetite and energy intake were similar between conditions. The present study reveals a paradoxical second-meal phenomenon whereby nocturnal whey protein feeding impaired subsequent glucose tolerance, whilst increasing post-prandial energy expenditure.

Development of innovative tools for investigation of nutrient-gut interaction

The gastrointestinal tract is the key interface between the ingesta and the human body. There is wide recognition that the gastrointestinal response to nutrients or bioactive compounds, particularly the secretion of numerous hormones, is critical to the regulation of appetite, body weight and blood glucose. This concept has led to an increasing focus on "gut-based" strategies for the management of metabolic disorders, including type 2 diabetes and obesity. Understanding the underlying mechanisms and downstream effects of nutrient-gut interactions is fundamental to effective translation of this knowledge to clinical practice. To this end, an array of research tools and platforms have been developed to better understand the mechanisms of gut hormone secretion from enteroendocrine cells. This review discusses the evolution of in vitro and in vivo models and the integration of innovative techniques that will ultimately enable the development of novel therapies for metabolic diseases.

Whey protein consumption following fasted exercise reduces early postprandial glycaemia in centrally obese males: a randomised controlled trial

Purpose

Acute submaximal exercise and whey protein supplementation have been reported to improve postprandial metabolic and appetite responses to a subsequent meal independently. We aimed to examine the combination of these strategies on postprandial responses to a carbohydrate-rich breakfast.

Methods

Twelve centrally obese males (age 41 ± 3 years, waist circumference 123.4 ± 2.9 cm), completed three trials in a single-blind, crossover design. Participants rested for 30 min (CON) or completed 30 min low–moderate-intensity treadmill walking (51 ± 1% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\dot{V}O}}_{\text{2peak}}$$\end{document}V˙O2peak) followed immediately by ingestion of 20 g whey protein (EX + PRO) or placebo (EX). After 15 min, a standardised breakfast was consumed and blood, expired gas and subjective appetite were sampled postprandially. After 240 min, an ad libitum lunch meal was provided to assess energy intake.

Results

During EX + PRO, post-breakfast peak blood glucose was reduced when compared with EX and CON (EX + PRO: 7.6 ± 0.4 vs EX: 8.4 ± 0.3; CON: 8.3 ± 0.3 mmol l⁻¹, p ≤ 0.04). Early postprandial glucose AUC_0–60 min was significantly lower under EX + PRO than EX (p = 0.011), but not CON (p = 0.12). Over the full postprandial period, AUC_0–240 min during EX + PRO did not differ from other trials (p > 0.05). Peak plasma insulin concentrations and AUC_0–240 min were higher during EX + PRO than CON, but similar to EX. Plasma triglyceride concentrations, substrate oxidation and subjective appetite responses were similar across trials and ad libitum energy intake was not influenced by prior fasted exercise, nor its combination with whey protein supplementation (p > 0.05).

Conclusion

Following fasted low–moderate-intensity exercise, consuming whey protein before breakfast may improve postprandial glucose excursions, without influencing appetite or subsequent energy intake, in centrally obese males.

Trial registration number

NCT02714309.

Effects of L-Phenylalanine on Energy Intake and Glycaemia-Impacts on Appetite Perceptions, Gastrointestinal Hormones and Gastric Emptying in Healthy Males

In humans, phenylalanine stimulates plasma cholecystokinin (CCK) and pyloric pressures, both of which are important in the regulation of energy intake and gastric emptying. Gastric emptying is a key determinant of postprandial blood glucose. We evaluated the effects of intragastric phenylalanine on appetite perceptions and subsequent energy intake, and the glycaemic response to, and gastric emptying of, a mixed-nutrient drink. The study consisted of two parts, each including 16 healthy, lean males (age: 23 ± 1 years). In each part, participants received on three separate occasions, in randomised, double-blind fashion, 5 g (Phe-5 g) or 10g ('Phe-10 g) L-phenylalanine, or control, intragastrically, 30 min before a standardised buffet-meal (part A), or a standardised mixed-nutrient drink (part B). In part A, plasma CCK and peptide-YY (PYY), and appetite perceptions, were measured at baseline, after phenylalanine alone, and following the buffet-meal, from which energy intake was assessed. In part B, plasma glucose, glucagon-like peptide-1 (GLP-1), insulin and glucagon were measured at baseline, after phenylalanine alone, and for 2 h following the drink. Gastric emptying of the drink was also measured by 13C-acetate breath-test. Phe-10 g, but not Phe-5 g, stimulated plasma CCK (p = 0.01) and suppressed energy intake (p = 0.012); energy intake was correlated with stimulation of CCK (r = -0.4, p = 0.027), and tended to be associated with stimulation of PYY (r = -0.31, p = 0.082). Both Phe-10 g and Phe-5 g stimulated insulin and glucagon (all p < 0.05), but not GLP-1. Phe-10 g, but not Phe-5 g, reduced overall plasma glucose (p = 0.043) and peak plasma glucose (p = 0.017) in response to the mixed-nutrient drink. Phenylalanine had no effect on gastric emptying of the drink. In conclusion, our observations indicate that the energy intake-suppressant effect of phenylalanine is related to the stimulation of CCK and PYY, while the glucoregulatory effect may be independent of stimulation of plasma GLP-1 or slowing of gastric emptying.

The Role of Nutri(epi)genomics in Achieving the Body's Full Potential in Physical Activity

Physical activity represents a powerful tool to achieve optimal health. The overall activation of several molecular pathways is associated with many beneficial effects, mainly converging towards a reduced systemic inflammation. Not surprisingly, regular activity can contribute to lowering the “epigenetic age”, acting as a modulator of risk toward several diseases and enhancing longevity. Behind this, there are complex molecular mechanisms induced by exercise, which modulate gene expression, also through epigenetic modifications. The exercise-induced epigenetic imprint can be transient or permanent and contributes to the muscle memory, which allows the skeletal muscle adaptation to environmental stimuli previously encountered. Nutrition, through key macro- and micronutrients with antioxidant properties, can play an important role in supporting skeletal muscle trophism and those molecular pathways triggering the beneficial effects of physical activity. Nutrients and antioxidant food components, reversibly altering the epigenetic imprint, have a big impact on the phenotype. This assigns a role of primary importance to nutri(epi)genomics, not only in optimizing physical performance, but also in promoting long term health. The crosstalk between physical activity and nutrition represents a major environmental pressure able to shape human genotypes and phenotypes, thus, choosing the right combination of lifestyle factors ensures health and longevity.

Whey Protein and Its Components Lactalbumin and Lactoferrin Affect Energy Balance and Protect against Stroke Onset and Renal Damage in Salt-Loaded, High-Fat Fed Male Spontaneously Hypertensive Stroke-Prone Rats

BACKGROUND

Whey protein (WH)-enriched diets are reported to aid in weight loss and to improve cardiovascular health. However, the bioactive components in whey responsible for causing such effects remain unidentified.

OBJECTIVE

We determined the effects of whey and its components [α-lactalbumin (LA) and lactoferrin (LF)] on energy balance, glucose tolerance, gut hormones, renal damage, and stroke onset in rats.

METHODS

Male spontaneously hypertensive stroke-prone (SHRSP) rats (age 8 wk) were fed isocaloric high-fat (40% kcal) and high-salt (4% wt/wt) diets (n = 8-10/group) and randomized for 8 wk to diets enriched as follows: control (CO): 15% kcal from egg albumin, 45% kcal from carbohydrate; WH: 20%kcal WH isolate + 15% kcal egg albumin; LA: 20% kcal LA  + 15% kcal egg albumin; or LF: 20% kcal lactoferrin + 15% kcal egg albumin. Measurements included energy balance (food intake, energy expenditure, and body composition), stroke-related behaviors, brain imaging, glucose tolerance, metabolic hormones, and tissue markers of renal damage. Data were analyzed by linear mixed models with repeated measures or 1-way ANOVA.

RESULTS

Diets enriched with WH, LA, or LF increased survival, with 25% of rats fed these diets exhibiting stroke-associated morbidity, whereas 90% of CO rats were morbid by 8 wk (P < 0.05). The nephritis scores of rats fed WH-, LA-, or LF-enriched diets were 80%, 92%, and 122% lower than those of COs (P = 0.001). The mRNA abundances of renin and osteopontin were 100-600% lower in rats fed WH-, LA-, or LF-enriched diets than in COs (P < 0.05). Urine albumin concentrations and albumin-to-creatinine ratios were 200% lower in rats fed LF-enriched diets than in COs (P < 0.05). Compared with COs, rats fed LF-enriched diets for 2-3 wk had food intake decreased by 29%, body weight decreased by 13-19%, lean mass decreased by 12-19%, and fat mass decreased by 20% (P < 0.001). Relative to COs, rats fed WH and LA had food intake decreased by 10% (P < 0.1), but COs had 12-45% lower weight than rats fed LA- and WH-enriched diets by 3 wk (P < 0.01). Compared with COs, rats fed WH-enriched diets increased energy expenditure by 7%, whereas, rats fed LA-enriched diets had energy expenditure acutely decreased by 7% during the first 4 d, and rats fed LF-enriched diets had energy expenditure decreased by 7-17% throughout the first week ( P < 0.001). Rats fed LA- and LF-enriched diets had blood glucose decreased by 14-19% (P < 0.05) and WH by 9% (P = 0.1), relative to COs. Compared with COs, rats fed LF had GIP decreased by 90% and PYY by 87% (P < 0.05).

CONCLUSION

Together, these findings indicate that whey and its components α-lactalbumin and lactoferrin improved energy balance and glycemic control, and protected against the onset of neurological deficits associated with stroke and renal damage in male SHRSP rats.

Effects of mycoprotein on glycaemic control and energy intake in humans: a systematic review

Mycoprotein is a food high in both dietary fibre and non-animal-derived protein. Global mycoprotein consumption is increasing, although its effect on human health has not yet been systematically reviewed. This study aims to systematically review the effects of mycoprotein on glycaemic control and energy intake in humans. A literature search of randomised controlled trials was performed in PubMed, Embase, Web of Science, Google Scholar and hand search. A total of twenty-one studies were identified of which only five studies, totalling 122 participants, met the inclusion criteria. All five studies were acute studies of which one reported outcomes on glycaemia and insulinaemia, two reported on energy intake and two reported on all of these outcomes. Data were extracted, and risk-of-bias assessment was then conducted. The results did not show a clear effect of acute mycoprotein on blood glucose levels, but it showed a decrease in insulin levels. Acute mycoprotein intake also showed to decrease energy intake at an ad libitum meal and post-24 h in healthy lean, overweight and obese humans. In conclusion, the acute ingestion of mycoprotein reduces energy intake and insulinaemia, whereas its impact on glycaemia is currently unclear. However, evidence comes from a very limited number of heterogeneous studies. Further well-controlled studies are needed to elucidate the short- and long-term effects of mycoprotein intake on glycaemic control and energy intake, as well as the mechanisms underpinning these effects.

Intragastric administration of the bitter tastant quinine lowers the glycemic response to a nutrient drink without slowing gastric emptying in healthy men

The rate of gastric emptying and the release of gastrointestinal (GI) hormones are major determinants of postprandial blood-glucose concentrations and energy intake. Preclinical studies suggest that activation of GI bitter-taste receptors potently stimulates GI hormones, including glucagon-like peptide-1 (GLP-1), and thus may reduce postprandial glucose and energy intake. We evaluated the effects of intragastric quinine on the glycemic response to, and the gastric emptying of, a mixed-nutrient drink and the effects on subsequent energy intake in healthy men. The study consisted of 2 parts: part A included 15 lean men, and part B included 12 lean men (aged 26 ± 2 yr). In each part, participants received, on 3 separate occasions, in double-blind, randomized fashion, intragastric quinine (275 or 600 mg) or control, 30 min before a mixed-nutrient drink (part A) or before a buffet meal (part B). In part A, plasma glucose, insulin, glucagon, and GLP-1 concentrations were measured at baseline, after quinine alone, and for 2 h following the drink. Gastric emptying of the drink was also measured. In part B, energy intake at the buffet meal was quantified. Quinine in 600 mg (Q600) and 275 mg (Q275) doses alone stimulated insulin modestly (P < 0.05). After the drink, Q600 and Q275 reduced plasma glucose and stimulated insulin (P < 0.05), Q275 stimulated GLP-1 (P < 0.05), and Q600 tended to stimulate GLP-1 (P = 0.066) and glucagon (P = 0.073) compared with control. Quinine did not affect gastric emptying of the drink or energy intake. In conclusion, in healthy men, intragastric quinine reduces postprandial blood glucose and stimulates insulin and GLP-1 but does not slow gastric emptying or reduce energy intake under our experimental conditions.

Reducing the glycemic impact of carbohydrates on foods and meals: Strategies for the food industry and consumers with special focus on Asia

Type 2 diabetes is increasingly prevalent in Asia, which can be attributed to a carbohydrate-rich diet, consisting of foods in the form of grains, for example, rice, or a food product made from flours or isolated starch, for example, noodles. Carbohydrates become a health issue when they are digested and absorbed rapidly (high glycemic index), and more so when they are consumed in large quantities (high glycemic load). The principal strategies of glycemic control should thus aim to reduce the amount of carbohydrate available for digestion, reduce the rate of digestion of the food, reduce the rate of glucose absorption, and increase the rate of glucose removal from blood. From a food perspective, the composition and structure of the food can be modified to reduce the amount of carbohydrates or alter starch digestibility and glucose absorption rates via using different food ingredients and processing methods. From a human perspective, eating behavior and food choices surrounding a meal can also affect glycemic response. This review therefore identifies actionable strategies and opportunities across foods and meals that can be considered by food manufacturers or consumers. They are (a) using alternative ingredients, (b) adding functional ingredients, and (c) changing processing methods and parameters for foods, and optimizing (a) eating behavior, (b) preloading or co-ingestion of other macronutrients, and (c) meal sequence and history. The effectiveness of a strategy would depend on consumer acceptance, compatibility of the strategy with an existing food product, and whether it is economically or technologically feasible. A combination of two or more strategies is recommended for greater effectiveness and flexibility.

A word of caution against excessive protein intake

Dietary protein is crucial for human health because it provides essential amino acids for protein synthesis. In addition, dietary protein is more satiating than carbohydrate and fat. Accordingly, many people consider the protein content when purchasing food and beverages and report 'trying to eat more protein'. The global market for protein ingredients is projected to reach approximately US$90 billion by 2021, largely driven by the growing demand for protein-fortified food products. This Perspective serves as a caution against the trend of protein-enriched diets and provides an evidence-based counterpoint that underscores the potential adverse public health consequences of high protein intake.

Effect of Oyster Meat Preload on Postmeal Glycemic Control in Healthy Young Adults

Objective: Evidence suggests that food preload improves postmeal glycemic profiles, but the effects of marine food are poorly understood. Our study aims to verify the regulating effects of premeal oyster meat (OM) on postprandial blood glucose.Method: Edible parts of the flesh of oyster were prepared for a randomized crossover experiment. After overnight fasting, 20 healthy young men consumed 300 mL of preload drinks with 0 g/kg body weight (BW) (control), 0.1 g/kg BW, and 0.2 g/kg BW. Peripheral blood concentrations of glucose and gastrointestinal hormones were measured before preloading at baseline (0 minutes) and at intervals after the preload and after a preset rice meal. The nutrient composition of OM was analyzed.Results: Compared with other doses, 0.2 g/kg BW OM preload induced higher plasma premeal insulin (p < 0.05), C-peptide (p < 0.05), and glucagon-like peptide-1 (GLP-1; p < 0.05) without altering the glucose concentrations during premeal times. By contrast, 0.2 g/kg BW OM induced less secretion of glucose (p < 0.05) and gastric inhibitory peptide (GIP; p < 0.05), but higher secretion of GLP-1 (p < 0.05) than 0.1 g/kg BW of OM after a meal. During the entire experiment (0-170 minutes), OM reduced the blood glucose (p < 0.05) and GIP (p < 0.05), but increased GLP-1 (p < 0.05). OM was rich in protein (78.4%) and low in fat (6%). Glutamic acid, aspartic acids, glycine, and taurine are the amino acids with high content found in OM.Conclusions: OM preload reduces postmeal glycemia in healthy young people with associated changes in gastrointestinal hormone responses. This effect may be attributed to the rich contents of protein and amino acids of OM.

Apple Preload Halved the Postprandial Glycaemic Response of Rice Meal on in Healthy Subjects

This study aimed to investigate the possible glycemic effect of apple preload on acute postprandial glycemic responses (GRs) of a following rice meal, comparing with its co-ingestion counterpart and an apple sugar solution preload, based on equal carbohydrates intake. In a randomized crossover trial, 18 healthy female subjects consumed (1) rice, (2) co-ingestion of apple and rice (A+R), (3) apple preload and rice (PA+R), and (4) rice with sugar solution preload (same sugar profile as in apple) (PSS+R). Acute postprandial GR tests and subjective satiety tests were carried out for each test food. Compared with rice reference, the PA+R achieved a 50% reduction of the iAUC_0-120, a 51.4% reduction of the average peak value, and a 52.6% reduction of glycemic excursion in 240 min, while the PSS+R showed 29.7% and 31.6% reduction of peak value and glycemic excursion, respectively. No significant differences were found between R and PA+R in any of the satiety characteristics. Compared with rice control, apple preload of 15 g available carbohydrates remarkably lowered the acute postprandial GR without negative effect on satiety. The sugar component may partly contribute to the glycemic suppressing effect of the apple preload.

Title: Differentiating the effects of whey protein and guar gum preloads on postprandial glycemia in type 2 diabetes

BACKGROUND AND AIMS

Whey protein and guar gum have both been reported to reduce postprandial glycemia in health and type 2 diabetes, associated with stimulation of glucagon-like peptide-1 (GLP-1) and/or slowing of gastric emptying. Our aim was to evaluate, in type 2 diabetes, the acute effects of low dose "preloads" of whey and guar, given alone or in combination before a meal, on postprandial glycemia, insulin, GLP-1, and gastric emptying.

METHODS

21 patients with type 2 diabetes, managed by diet or metformin alone, were each studied on 4 days. They received a preload "shake" 15min before a mashed potato meal (368.5 kcal) labeled with 13C-octanoic-acid. The preloads comprised either (i) 17 g whey (W), (ii) 5 g guar (G), (iii) 17 g whey + 5 g guar (WG) each sweetened with 60 mg sucralose, and (iv) 60 mg sucralose alone (control; C), all dissolved in 150 mL water. Venous blood was sampled frequently for measurements of glucose, insulin, and GLP-1 concentrations. Gastric half-emptying time (T50) was calculated from breath 13CO2 excretion over 240 min.

RESULTS

Postprandial blood glucose concentrations were lower with W and WG compared to C (each P < 0.0001, treatment × time interaction), and lower after G than C only at 30min. Insulin, GLP-1, and glucagon concentrations were higher after W than WG, G, or C (P < 0.05, treatment × time interaction), without differences between the latter three. Gastric emptying was slower with W (T50: 179.6 ± 6.1 min, P < 0.05) and WG (T50: 197.6 ± 9.7 min, P < 0.0001) when compared to C (T50: 162.9 ± 6.2 min), but did not differ between G (T50: 171.3 ± 7.0) and C (P > 0.99).

CONCLUSION

Both whey and whey/guar preloads reduced postprandial glycemia, associated with slowing of gastric emptying. Low dose guar was less effective as a preload for glucose-lowering and did not slow gastric emptying.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

Australian and New Zealand Clinical Trials Registry, Trial ID ACTRN12615001272583, http://www.anzctr.org.au.

Wheat Protein Hydrolysate Fortified With l-Arginine Enhances Satiation Induced by the Capsaicinoid Nonivamide in Moderately Overweight Male Subjects

SCOPE

Increasing the intake of satiety-enhancing food compounds represents a promising strategy for maintaining a healthy body weight. Recently, satiating effects for the capsaicinoid nonivamide have been demonstrated. As various proteins and amino acids have also been demonstrated to decrease energy intake, oral glucose tolerance test (oGTT)-based bolus interventions of 75 g glucose + 0.15 mg nonivamide (NV control) are tested with/without combination of a wheat protein hydrolysate (WPH: 2 g) and/or l-arginine (ARG: 3.2 g) for their satiating effects in 27 moderately overweight male subjects.

METHODS AND RESULTS

Compared to NV control intervention, ARG and WPH + ARG treatment both reduce (p < 0.01) total calorie intake from a standardized breakfast by -5.9 ± 4.15% and -6.07 ± 4.38%, respectively. For the WPH + ARG intervention, increased mean plasma serotonin concentrations (AUC: 350 ± 218), quantitated by ELISA, and delayed gastric emptying, assessed by 13 C-Na-acetate breath test (-2.10 ± 0.51%, p < 0.05), are demonstrated compared to NV control. Correlation analysis between plasma serotonin and gastric emptying reveals a significant association after WPH ± ARG intervention (r = -0.396, p = 0.045).

CONCLUSION

Combination of WPH and ARG enhances the satiating effect of nonivamide, providing opportunities to optimize satiating food formulations by low amounts of the individual food constituents.

The homeostatic dynamics of feeding behaviour identify novel mechanisms of anorectic agents

Better understanding of feeding behaviour will be vital in reducing obesity and metabolic syndrome, but we lack a standard model that captures the complexity of feeding behaviour. We construct an accurate stochastic model of rodent feeding at the bout level in order to perform quantitative behavioural analysis. Analysing the different effects on feeding behaviour of peptide YY3-36 (PYY3-36), lithium chloride, glucagon-like peptide 1 (GLP-1), and leptin shows the precise behavioural changes caused by each anorectic agent. Our analysis demonstrates that the changes in feeding behaviour evoked by the anorectic agents investigated do not mimic the behaviour of well-fed animals and that the intermeal interval is influenced by fullness. We show how robust homeostatic control of feeding thwarts attempts to reduce food intake and how this might be overcome. In silico experiments suggest that introducing a minimum intermeal interval or modulating upper gut emptying can be as effective as anorectic drug administration.

Effect of a Snack Bar Optimized to Reduce Alcohol Bioavailability: A Randomized Controlled Clinical Trial in Healthy Individuals

Alcohol intoxication impairs judgment and reaction times and the level of blood alcohol concentration (BAC) is highly correlated with accidents and injury. We hypothesized that a food optimized to delay gastric emptying, a reduced alcohol bioavailability bar (RABB), would decrease postprandial BAC and alcohol bioavailability with greater caloric-efficiency than control foods. Therefore, we evaluated the RABB in a randomized, crossover trial in 21 overnight fasted healthy adults (10 male, 11 female). Just before consuming a moderate dose of alcohol (0.3-0.35 g/kg body weight), participants ate either (1) no food (NF, 0 kcal), (2) the RABB (210 kcal), (3) a savory snack mix (SSM, 210 kcal), or (4) a multicomponent meal (MCM, 635 kcal) and their BAC was measured over 90 minutes using a breathalyzer, the primary endpoint being peak BAC (pBAC). pBACs were analyzed by repeated measures analysis of variance (ANOVA) (F = 107.5, P < .0001) with the differences between means assessed using Tukey's honestly significant difference test. The pBAC of each group was different (P < .001) from all other groups (NF = 0.064 ± 0.003, SSM = 0.047 ± 0.002, RABB = 0.031 ± 0.002, MCM = 0.020 ± 0.002%; mean ± standard error of the mean). Furthermore, the bioavailability of alcohol over 90 minutes (BA90) was reduced compared to the NF group by similar margins (SSM = 22.0 ± 2.2, RABB = 45.0 ± 3.8, MCM = 67.9 ± 3.1%) with the mean BA90 of each group different from all other groups (P < .001). Compared to the NF condition, the average reduction of pBAC per 100 calories of food consumed was higher for the RABB (24.0%) than either the SSM (11.8%) or the MCM (10.7%). This study demonstrates that the RABB can reduce both pBAC and alcohol bioavailability with high caloric-efficiency.

Effects of Duodenal Infusion of Lauric Acid and L-Tryptophan, Alone and Combined, on Fasting Glucose, Insulin and Glucagon in Healthy Men

The fatty acid, lauric acid ('C12'), and the amino acid, tryptophan ('Trp'), when given intraduodenally at loads that individually do not affect energy intake, have recently been shown to stimulate plasma cholecystokinin, suppress ghrelin and reduce energy intake much more markedly when combined. Both fatty acids and amino acids stimulate insulin secretion by distinct mechanisms; fatty acids enhance glucose-stimulated insulin secretion, while amino acids may have a direct effect on pancreatic β cells. Therefore, it is possible that, by combining these nutrients, their effects to lower blood glucose may be enhanced. We have investigated the potential for the combination of C12 and Trp to have additive effects to reduce blood glucose. To address this question, plasma concentrations of glucose, insulin and glucagon were measured in 16 healthy, lean males during duodenal infusions of saline (control), C12 (0.3 kcal/min), Trp (0.1 kcal/min), or C12+Trp (0.4 kcal/min), for 90 min. Both C12 and C12+Trp moderately reduced plasma glucose compared with control (p < 0.05). C12+Trp, but not C12 or Trp, stimulated insulin and increased the insulin-to-glucose ratio (p < 0.05). There was no effect on plasma glucagon. In conclusion, combined intraduodenal administration of C12 and Trp reduced fasting glucose in healthy men, and this decrease was driven primarily by C12. The effects of these nutrients on postprandial blood glucose and elevated fasting blood glucose in type 2 diabetes warrant evaluation.

The Effects of a Whey Protein and Guar Gum-Containing Preload on Gastric Emptying, Glycaemia, Small Intestinal Absorption and Blood Pressure in Healthy Older Subjects

A whey protein/guar gum preload reduces postprandial glycaemia in type 2 diabetes through slowing gastric emptying. However, gastric emptying has previously been assessed using a stable isotope breath test technique, which cannot discriminate between slowing of gastric emptying and small intestinal absorption. This preload also may be useful in the management of postprandial hypotension. We evaluated the effects of a whey protein/guar preload on gastric emptying, glucose absorption, glycaemic/insulinaemic and blood pressure (BP) responses to an oral glucose load. Eighteen healthy older participants underwent measurements of gastric emptying (scintigraphy), plasma glucose and insulin, glucose absorption, superior mesenteric artery (SMA) flow, BP and heart rate (HR) after ingesting a 50 g glucose drink, with or without the preload. The preload reduced plasma glucose (p = 0.02) and serum 3-O-methylglucose (3-OMG) (p = 0.003), and increased plasma insulin (p = 0.03). There was no difference in gastric emptying or BP between the two days. The reduction in plasma glucose on the preload day was related to the reduction in glucose absorption (r = 0.71, p = 0.002). In conclusion, the glucose-lowering effect of the preload may relate to delayed small intestinal glucose absorption and insulin stimulation, rather than slowing of gastric emptying.

The Impact of a Large Bolus Dose of l-leucine and l-isoleucine on Enteroendocrine and Pancreatic Hormones, and Glycemia in Healthy, Inactive Adults

Background: The ingestion of whey protein and amino acids with carbohydrate (CHO) enhances the release of glucagon-like peptide-1 (GLP-1) and glucose-dependent-insulinotropic peptide (GIP) that promote insulin secretion. It is unknown if L-isoleucine (Ile) and L-leucine (Leu) have this same effect. The purpose of this study was to examine how Ile and Leu influence both GLP-1 and GIP, subsequent pancreatic hormones, and glycemia in healthy, inactive adults. Methods: Twelve adults (6F/6M; age 27.4 ± 2 years; BMI 26.3 ± 2 kg/m²; lean body mass 53.2 ± 5 kg; body fat 34.1 ± 3%) completed four conditions in a randomized, cross-over fashion. Treatments standardized (0.3 g/kg·LBM⁻¹) (1) Leu, (2) Ile, (3) Equal (1:1 g) of Leu + Ile, and (4) placebo (Pla, 3.5 g inert stevia) ingested 30 min prior to an oral glucose tolerance test (OGTT). Samples of plasma glucose, insulin, glucagon, GIP_Total, and GLP-1_Active were assessed. Results: A treatment (p = 0.01) effect comparing Ile vs. Leu (p = 0.02) in GIP_Total. Area under the curve showed an increase in GIP_Total from Ile compared to Leu and Pla (p = 0.03). No effect was found on GLP-1. The ingestion of Ile prior to CHO augmented GIP concentration greater than Leu or Pla. No correlation was found between GIP, insulin, and glucose between conditions. Conclusions: Ile impacts GIP concentration, which did not relate to either insulin or glucose concentrations. Neither Ile, nor Leu seem to have an effect on hyperglycemia ingested prior to a CHO drink.

Milk in the prevention and management of type 2 diabetes: The potential role of milk proteins

Globally, diabetes mellitus is not only considered a leading cause of mortality and morbidities but has also created a substantial economic burden. There is growing evidence that foods and their components can be implemented in the prevention and management of type 2 diabetes mellitus (T2DM). Increased dairy consumption has been linked to a lower risk of T2DM. The protective role of dairy foods in the development of T2DM is thought to be largely attributable to dairy nutrients, one of them being dairy protein. There is considerable evidence that milk proteins increase the postprandial insulin response and lower the postprandial blood glucose response in both healthy subjects and patients with T2DM. The exact mechanisms by which milk proteins lower postprandial glucose levels are yet to established; however, the amino acids and bioactive peptides derived from milk proteins are thought to modify a physiological milieu, which includes delayed gastric emptying and the enhancement of incretin and insulin responses, consequently leading to lower postprandial glucose levels. The present review will focus on providing a clear presentation of the potential implementation of milk proteins as a dietary supplement in the prevention and management of T2DM by summarizing the relevant supporting evidence for this particular topic.

Plasma Free Amino Acid Responses to Whey Protein and Their Relationships with Gastric Emptying, Blood Glucose- and Appetite-Regulatory Hormones and Energy Intake in Lean Healthy Men

This study determined the effects of increasing loads of whey protein on plasma amino acid (AA) concentrations, and their relationships with gastric emptying, blood glucose- and appetite-regulatory hormones, blood glucose and energy intake. Eighteen healthy lean men participated in a double-blinded study, in which they consumed, on 3 separate occasions, in randomised order, 450-mL drinks containing either 30 g (L) or 70 g (H) of pure whey protein isolate, or control with 0 g of protein (C). Gastric emptying, serum concentrations of AAs, ghrelin, cholecystokinin (CCK), glucagon-like-peptide 1 (GLP-1), insulin, glucagon and blood glucose were measured before and after the drinks over 180 min. Then energy intake was quantified. All AAs were increased, and 7/20 AAs were increased more by H than L. Incremental areas under the curve (iAUC0-180 min) for CCK, GLP-1, insulin and glucagon were correlated positively with iAUCs of 19/20 AAs (p < 0.05). The strongest correlations were with the branched-chain AAs as well as lysine, tyrosine, methionine, tryptophan, and aspartic acid (all R2 > 0.52, p < 0.05). Blood glucose did not correlate with any AA (all p > 0.05). Ghrelin and energy intake correlated inversely, but only weakly, with 15/20 AAs (all R2 < 0.34, p < 0.05). There is a strong relationship between gluco-regulatory hormones with a number of (predominantly essential) AAs. However, the factors mediating the effects of protein on blood glucose and energy intake are likely to be multifactorial.

The Metabolic Concept of Meal Sequence vs. Satiety: Glycemic and Oxidative Responses with Reference to Inflammation Risk, Protective Principles and Mediterranean Diet

With increasing exposure to eating opportunities and postprandial conditions becoming dominant states, acute effects of meals are garnering interest. In this narrative review, meal components, combinations and course sequence were questioned vis-à-vis resultant postprandial responses, including satiety, glycemic, oxidative and inflammatory risks/outcomes vs. protective principles, with reference to the Mediterranean diet. Representative scientific literature was reviewed and explained, and corresponding recommendations discussed and illustrated. Starting meals with foods, courses and/or preloads high in innate/added/incorporated water and/or fibre, followed by protein-based courses, delaying carbohydrates and fatty foods and minimizing highly-processed/sweetened hedonic foods, would increase satiety-per-calorie vs. obesogenic passive overconsumption. Similarly, starting with high-water/fibre dishes, followed by high-protein foods, oils/fats, and delayed/reduced slowly-digested whole/complex carbohydrate sources, optionally closing with simpler carbohydrates/sugars, would reduce glycaemic response. Likewise, starting with foods high in innate/added/incorporated water/fibre/antioxidants, high monounsaturated fatty acid foods/oils, light proteins and whole/complex carbohydrate foods, with foods/oils low in n-6 polyunsaturated fatty acids (PUFA) and n-6:n-3 PUFA ratios, and minimal-to-no red meat and highly/ultra-processed foods/lipids, would reduce oxidative/inflammatory response. Pyramids illustrating representative meal sequences, from most-to-least protective foods, visually communicate similarities between axes, suggesting potential unification for optimal meal sequence, consistent with anti-inflammatory nutrition and Mediterranean diet/meal principles, warranting application and outcome evaluation.

Energy Expenditure, Carbohydrate Oxidation and Appetitive Responses to Sucrose or Sucralose in Humans: A Pilot Study

Background: In light of obesity, replacing sugar with non-nutritive sweeteners is commonly used to reduce sugar content of food products. This study aimed to compare human energy expenditure (EE), carbohydrate oxidation and food intake after the ingestion of test foods sweetened with sucrose or a non-nutritive sweetener. Methods: This was an acute crossover feeding study that entailed consumption of three test foods: jelly sweetened with 50 g sucrose (SUCROSE), with 120 mg of sucralose only (NNS), or 120 mg sucralose but matched in carbohydrate with 50 g maltodextrin (MALT). On test days, participants arrived at the research facility after an overnight fast. Resting energy expenditure (indirect calorimeter) was measured for 30 min followed by jelly consumption. Participants’ EE and substrate oxidation were measured for 90 min subsequently. After EE assessment, participants completed a meal challenge before leaving the research facility, and recorded food intake for the remaining day. Subjective appetite ratings were assessed before and after test foods and meal challenge. Results: Eleven participants completed the study. EE was higher in SUCROSE and MALT than NNS, but not statistically significant. Carbohydrate oxidation was SUCROSE > MALT > NNS (p < 0.001). Earlier and bigger rise in carbohydrate oxidation was observed in SUCROSE than MALT, although both were carbohydrate-matched. NNS did not promote energy expenditure, carbohydrate oxidation or stimulate appetite. Conclusions: Foods sweetened with sucrose or non-nutritive sweeteners but matched in carbohydrate content have different effects on human EE and carbohydrate oxidation. Sucralose alone did not affect EE, but lower energy in the test food from sugar replacement was eventually fully compensated. Findings from this pilot study should be verified with bigger clinical studies in the future to establish clinical relevance.

Relationship between diet/exercise and pharmacotherapy to enhance the GLP-1 levels in type 2 diabetes

The rapid rise in the prevalence of type 2 diabetes mellitus (T2DM) poses a huge healthcare burden across the world. Although there are several antihyperglycaemic agents (AHAs) available including addition of new drug classes to the treatment algorithm, more than 50% of patients with T2DM do not achieve glycaemic targets, suggesting an urgent need for treatment strategies focusing on prevention and progression of T2DM and its long-term complications. Lifestyle changes including implementation of healthy diet and physical activity are cornerstones for the management of T2DM. The positive effects of diet and exercise on incretin hormones such as glucagon-like peptide-1 (GLP-1) have been reported. We hypothesize an IDEP concept (Interaction between Diet/Exercise and Pharmacotherapy) aimed at modifying the diet and lifestyle, along with pharmacotherapy to enhance the GLP-1 levels, would result in good glycaemic control in patients with T2DM. Consuming protein-rich food, avoiding saturated fatty acids and making small changes in eating habits such as eating slowly with longer mastication time can have a positive impact on the GLP-1 secretion and insulin levels. Further the type of physical activity (aerobic/resistance training), intensity of exercise, duration, time and frequency of exercise have shown to improve GLP-1 levels. Apart from AHAs, a few antihypertensive drugs and lipid-lowering drugs have also shown to increase endogenous GLP-1 levels, however, due to quick degradation of GLP-1 by dipeptidyl peptidase-4 (DPP-4) enzyme, treatment with DPP-4 inhibitors would protect GLP-1 from degradation and prolong its activity. Thus, IDEP concept can be a promising treatment strategy, which positively influences the GLP-1 levels and provide additive benefits in terms of improving metabolic parameters in patients with T2DM and slowing the progression of T2DM and its associated complications.

Increased milk protein content and whey-to-casein ratio in milk served with breakfast cereal reduce postprandial glycemia in healthy adults: An examination of mechanisms of action

This study describes the effects on glycemic response and the underlying mechanisms of action of increasing the protein concentration and decreasing the casein-to-whey ratio in milk when consumed with a high glycemic breakfast cereal. Twelve healthy men and women, aged 18 to 30 yr and with a body mass index of 20 to 24.9 kg/m², consumed (in random order) milk beverages (250 mL) containing either 3.1 or 9.3% protein and casein-to-whey ratios of either 80:20 or 40:60. We measured postprandial appetite, glucose, regulatory hormones, and stomach emptying rate over 200 min, as well as food intake at an ad libitum meal at 120 min. Although pre-meal appetite was suppressed to a greater extent with milk beverages that had high (9.3%) compared with regular (3.1%) protein content, food intake was similar among all 4 treatments. Pre-meal mean blood glucose was lower with beverages that had high rather than regular milk protein content, with the lowest glucose peaks after the high milk protein treatment with the 40:60 casein-to-whey ratio. Pre-meal insulin and C-peptide levels were not affected by milk protein content or casein-to-whey ratio, but pre-meal glucagon-like peptide 1 was higher after the treatment containing high milk protein and the 40:60 casein-to-whey ratio, and pre-meal cholecystokinin was higher after the treatments containing high milk protein content. Plasma paracetamol response was also lower after the treatments containing high compared with regular milk protein content. When consumed with carbohydrate, milk beverages with high protein content and (to a lesser extent) a decreased casein-to-whey ratio lowered postprandial glycemia through insulin-independent mechanisms, primarily associated with delayed stomach emptying.

Postprandial glucose, insulin and incretin responses differ by test meal macronutrient ingestion sequence (PATTERN study)

BACKGROUND

Previous studies have shown that the sequential order of consuming different food components significantly impacts postprandial glucose and insulin excursions in prediabetes and type 2 diabetes, but the causative mechanisms in healthy humans remain ill-defined.

OBJECTIVE

Using a typical Asian meal comprising vegetables, protein (chicken breast), and carbohydrate (white rice), the aim of this study was to examine the effect of food intake sequence on postprandial glucose, insulin and incretin secretions in healthy adults.

DESIGN

Sixteen healthy Chinese adults participated in a randomized, controlled, crossover meal trial. Subjects consumed in random order 5 experimental isocaloric meals that differed in the food intake sequence of vegetables, protein and carbohydrate. Glucose, insulin, incretins and satiety markers were measured over 3 h.

RESULTS

There were significant food intake sequence × time interaction effects on plasma glucose, insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) concentrations (P < 0.001). In comparison with rice consumed first followed by vegetable and meat (R-VM), the overall postprandial glucose response was significantly attenuated after the food intake sequence of vegetable first, followed by meat and rice (V-MR) or meat first, followed by vegetable and rice (M-VR) or vegetable first followed by meat and rice (V-M-R) or vegetable, meat and rice consumed together (VMR). The insulin iAUC (0-60) was significant lower after V-M-R than M-VR, VMR and R-VM. V-M-R food intake sequence stimulated higher GLP-1 release than other meal sequences. However, GIP response was lower after V-MR and V-M-R than M-VR and R-MR food intake sequences.

CONCLUSIONS

Food macronutrient intake sequence can considerably influence its glycemic, insulinemic and incretin responses. V-M-R food intake sequence attenuates the glycemic response to a greater degree with accentuated GLP-1 stimulation without any increased demand for insulin. The sequence of food intake has great potential as a novel and simple behavioral strategy to modulate glycemic response in healthy adults. The trial was registered at clinicaltrials.gov as NCT03533738.

Effects of Long-Term Dietary Protein Restriction on Intestinal Morphology, Digestive Enzymes, Gut Hormones, and Colonic Microbiota in Pigs

Simple Summary

In China, a shortage of protein resources is an important limiting factor to the economic benefit of pig production, and the use of protein-restriction diets balanced with amino acids is an effective strategy to save protein resources. However, long-term protein-restriction diets can impair the growth performance, and the reason is still unknown. This study is to investigate the response of gastrointestinal physiology and gut microbiota to the condition of long-term low-protein diet and to try to provide a theoretical foundation for better use of protein resources in swine production. Results showed that presented with moderate protein-restriction diets, pigs are able to adjust their absorption and consumption of nutrients to maintain growth performance; whereas extremely low-protein diets suppress pigs’ appetite, impair intestinal morphology, decrease Lactobacillus and Streptococcus, and reduce energy expenditure. Thus, moderate reduction of dietary protein is more suitable for pig production than extremely low-protein diets supplemented with essential amino acids, and moderate protein-restriction diets can potentially increase protein utilization in pig production.

Abstract

Using protein-restriction diets becomes a potential strategy to save the dietary protein resources. However, the mechanism of low-protein diets influencing pigs’ growth performance is still controversial. This study aimed to investigate the effect of protein-restriction diets on gastrointestinal physiology and gut microbiota in pigs. Eighteen weaned piglets were randomly allocated to three groups with different dietary protein levels. After a 16-week trial, the results showed that feeding a low-protein diet to pigs impaired the epithelial morphology of duodenum and jejunum (p < 0.05) and reduced the concentration of many plasma hormones (p < 0.05), such as ghrelin, somatostatin, glucose-dependent insulin-tropic polypeptide, leptin, and gastrin. The relative abundance of Streptococcus and Lactobacillus in colon and microbiota metabolites was also decreased by extreme protein-restriction diets (p < 0.05). These findings suggested that long-term ingestion of a protein-restricted diet could impair intestinal morphology, suppress gut hormone secretion, and change the microbial community and fermentation metabolites in pigs, while the moderately low-protein diet had a minimal effect on gut function and did not impair growth performance.

A whey/guar "preload" improves postprandial glycaemia and glycated haemoglobin levels in type 2 diabetes: A 12-week, single-blind, randomized, placebo-controlled trial

AIMS

To evaluate the effects of 12 weeks of treatment with a whey/guar preload on gastric emptying, postprandial glycaemia and glycated haemoglobin (HbA1c) levels in people with type 2 diabetes (T2DM).

MATERIALS AND METHODS

A total of 79 people with T2DM, managed on diet or metformin (HbA1c 49 ± 0.7 mmol/mol [6.6 ± 0.1%]), were randomized, in single-blind fashion, to receive 150 mL flavoured preloads, containing either 17 g whey protein plus 5 g guar (n = 37) or flavoured placebo (n = 42), 15 minutes before two meals, each day for 12 weeks. Blood glucose and gastric emptying (breath test) were measured before and after a mashed potato meal at baseline (without preload), and after the preload at the beginning (week 1) and end (week 12) of treatment. HbA1c levels, energy intake, weight and body composition were also evaluated.

RESULTS

Gastric emptying was slower (P < 0.01) and postprandial blood glucose levels lower (P < 0.05) with the whey/guar preload compared to placebo preload, and the magnitude of reduction in glycaemia was related to the rate of gastric emptying at both week 1 (r = -0.54, P < 0.001) and week 12 (r = -0.54, P < 0.0001). At the end of treatment, there was a 1 mmol/mol [0.1%] reduction in HbA1c in the whey/guar group compared to the placebo group (49 ± 1.0 mmol/mol [6.6 ± 0.05%] vs. 50 ± 0.8 mmol/mol [6.7 ± 0.05%]; P < 0.05). There were no differences in energy intake, body weight, or lean or fat mass between the groups.

CONCLUSIONS

In patients with well-controlled T2DM, 12 weeks' treatment with a low-dose whey/guar preload, taken twice daily before meals, had sustained effects of slowing gastric emptying and reducing postprandial blood glucose, which were associated with a modest reduction in HbA1c, without causing weight gain.

Fibre-enriched buckwheat pasta modifies blood glucose response compared to corn pasta in individuals with type 1 diabetes and celiac disease: Acute randomized controlled trial

AIM

People with type 1 diabetes and celiac disease (T1D&CD) have high blood glucose variability. Processed gluten-free foods have shown to induce a worse metabolic profile whereas naturally gluten-free foods may represent healthier options. On the other hand, dietary fibre has shown to reduce postprandial glycemic excursions in individuals with diabetes. Thus, we evaluated the acute effect of fibre-enriched buckwheat (FBP) and corn pasta (CP) on postprandial blood glucose response (PP-BGR).

METHODS

Ten adult patients with T1D&CD consumed two meals with the same amount of carbohydrate while differing only for pasta type (FBP or CP) preceded by the same insulin bolus. Participants utilized continuous glucose monitoring (CGM) and data over 6 h after meal were analyzed.

RESULTS

PP-BGR differed between the two meals, being significantly lower in the first period (0-3 h) after the CP than the FBP meal (iAUC: -38 ± 158 vs. 305 ± 209 mmol/L · 180 min, p = 0.040), whereas significantly higher in the second period (3-6 h) after the CP than the FBP meal (iAUC: 432 ± 153 vs. 308 ± 252 mmol/L · 180 min, p = 0.030). Overall, a less variable postprandial profile was observed after FBP than CP consumption.

CONCLUSIONS

In individuals with T1D&CD, the acute consumption of FBP induces significant differences in PP-BGR compared with CP that may be clinically relevant.

Effect of supplemental whey protein timing on postprandial glycaemia in centrally obese males

Consuming whey protein before a meal may reduce postprandial glucose excursions, however, optimising timing of supplementation is important to improve its clinical utility. A total of thirteen centrally obese, insulin-resistant males (waist circumference: 121 (sem 3) cm; homeostasis model assessment for insulin resistance (HOMA-IR): 6·4 (sem 1·2)) completed four experimental conditions in a single-blind, crossover design. Participants consumed mixed-macronutrient breakfast and lunch meals on all occasions, with 20 g whey protein consumed 15 min before (PRE), alongside (DUR) or 15 min post-breakfast (POST) or omitted (CON). Capillary glucose and plasma concentrations of insulin, TAG and NEFA, in addition to subjective appetite ratings, were collected for 180 min after each meal. PRE and DUR reduced post-breakfast glucose peak by 17·0 (sem 1·9) % (P<0·001) and 9·2 (sem 2·9) % (P=0·046), respectively, compared with CON. Post-breakfast glucose AUC was lower following PRE compared with POST and CON (PRE: 982 (sem 30) v. POST: 1031 (sem 36) and CON: 1065 (sem 37) mmol/l×180 min; P≤0·042) but similar to DUR (1013 (sem 32) mmol/l×180 min; P=0·77). Insulin was lower during PRE, when compared with POST and DUR (both P≤0·042) but similar to CON. There were no between-condition differences in measures of postprandial lipaemia or appetite, and no effect of condition post-lunch. Consumption of whey protein as a preload or alongside a mixed-macronutrient breakfast reduces postprandial glucose excursions in centrally obese, insulin-resistant males. Whey consumed as a preload has superior glycaemic-lowering effects. Supplementation at breakfast does not alter glycaemic responses to subsequent meals.

Effects of Dietary Protein and Fat Content on Intrahepatocellular and Intramyocellular Lipids during a 6-Day Hypercaloric, High Sucrose Diet: A Randomized Controlled Trial in Normal Weight Healthy Subjects

Sucrose overfeeding increases intrahepatocellular (IHCL) and intramyocellular (IMCL) lipid concentrations in healthy subjects. We hypothesized that these effects would be modulated by diet protein/fat content. Twelve healthy men and women were studied on two occasions in a randomized, cross-over trial. On each occasion, they received a 3-day 12% protein weight maintenance diet (WM) followed by a 6-day hypercaloric high sucrose diet (150% energy requirements). On one occasion the hypercaloric diet contained 5% protein and 25% fat (low protein-high fat, LP-HF), on the other occasion it contained 20% protein and 10% fat (high protein-low fat, HP-LF). IHCL and IMCL concentrations (magnetic resonance spectroscopy) and energy expenditure (indirect calorimetry) were measured after WM, and again after HP-LF/LP-HF. IHCL increased from 25.0 ± 3.6 after WM to 147.1 ± 26.9 mmol/kg wet weight (ww) after LP-HF and from 30.3 ± 7.7 to 57.8 ± 14.8 after HP-LF (two-way ANOVA with interaction: p < 0.001 overfeeding x protein/fat content). IMCL increased from 7.1 ± 0.6 to 8.8 ± 0.7 mmol/kg ww after LP-HF and from 6.2 ± 0.6 to 6.9 ± 0.6 after HP-LF, (p < 0.002). These results indicate that liver and muscle fat deposition is enhanced when sucrose overfeeding is associated with a low protein, high fat diet compared to a high protein, low fat diet.

Intraduodenal Administration of L-Valine Has No Effect on Antropyloroduodenal Pressures, Plasma Cholecystokinin Concentrations or Energy Intake in Healthy, Lean Men

Whey protein is rich in the branched-chain amino acids, L-leucine, L-isoleucine and L-valine. Thus, branched-chain amino acids may, at least in part, mediate the effects of whey to reduce energy intake and/or blood glucose. Notably, 10 g of either L-leucine or L-isoleucine, administered intragastrically before a mixed-nutrient drink, lowered postprandial blood glucose, and intraduodenal infusion of L-leucine (at a rate of 0.45 kcal/min, total: 9.9 g) lowered fasting blood glucose and reduced energy intake from a subsequent meal. Whether L-valine affects energy intake, and the gastrointestinal functions involved in the regulation of energy intake, as well as blood glucose, in humans, is currently unknown. We investigated the effects of intraduodenally administered L-valine on antropyloroduodenal pressures, plasma cholecystokinin, blood glucose and energy intake. Twelve healthy lean men (age: 29 ± 2 years, BMI: 22.5 ± 0.7 kg/m²) were studied on 3 separate occasions in randomised, double-blind order. Antropyloroduodenal pressures, plasma cholecystokinin, blood glucose, appetite perceptions and gastrointestinal symptoms were measured during 90-min intraduodenal infusions of L-valine at 0.15 kcal/min (total: 3.3 g) or 0.45 kcal/min (total: 9.9 g), or 0.9% saline (control). Energy intake from a buffet-meal immediately after the infusions was quantified. L-valine did not affect antral, pyloric (mean number; control: 14 ± 5; L-Val-0.15: 21 ± 9; L-Val-0.45: 11 ± 4), or duodenal pressures, plasma cholecystokinin (mean concentration, pmol/L; control: 3.1 ± 0.3; L-Val-0.15: 3.2 ± 0.3; L-Val-0.45: 3.0 ± 0.3), blood glucose, appetite perceptions, symptoms or energy intake (kcal; control: 1040 ± 73; L-Val-0.15: 1040 ± 81; L-Val-0.45: 1056 ± 100), at either load (p > 0.05 for all). In conclusion, intraduodenal infusion of L-valine, at loads that are moderately (3.3 g) or substantially (9.9 g) above World Health Organization valine requirement recommendations, does not appear to have energy intake- or blood glucose-lowering effects.

Pre-meal and postprandial lipaemia in subjects with the metabolic syndrome: effects of timing and protein quality (randomised crossover trial)

Non-fasting TAG - postprandial lipaemia (PPL) - are to a higher degree associated with cardiovascular risk compared with fasting TAG. Dietary protein, especially whey proteins (WP), may lower PPL. We hypothesised that a WP pre-meal (17·6 g protein) consumed 15 v. 30 min before a fat-rich meal reduces the PPL response in subjects with the metabolic syndrome (MetS) and that a WP pre-meal has more potent effects than casein and gluten pre-meals. A total of sixteen subjects with the MetS completed an acute, randomised, crossover trial. WP pre-meals were consumed 15 and 30 min, and casein and gluten 15 min before a fat-rich meal. Blood samples were drawn 360 min postprandially to determine metabolite and hormone responses, S-paracetamol (for assessment of gastric emptying) and amino acids. Insulin and glucagon responses were affected by both timing and protein type (for all P <0·01), with significantly higher concentrations for WP given at -15 min than WP at -30 min and higher responses compared with gluten for the first 30 min after pre-meal consumption (for all P <0·05). The PPL responses changed neither by timing nor by protein type. Glucose-dependent insulinotropic peptide but not glucagon-like peptide 1 responses differed between the three protein types. S-paracetamol concentration was higher for WP (-30 min) than for WP (-15 min) 15 min after the main meal (P = 0·028), and higher for casein and gluten than for WP at time point 30 min (for all P <0·05). In conclusion, the PPL response was not changed by ingestion of a 17·6 g protein pre-meal, whereas both timing and protein quality affected hormone secretion (insulin and glucagon).

Impact of Nutrient Type and Sequence on Glucose Tolerance: Physiological Insights and Therapeutic Implications

Pharmacological and dietary interventions targeting postprandial glycemia have proved effective in reducing the risk for type 2 diabetes and its cardiovascular complications. Besides meal composition and size, the timing of macronutrient consumption during a meal has been recently recognized as a key regulator of postprandial glycemia. Emerging evidence suggests that premeal consumption of non-carbohydrate macronutrients (i.e., protein and fat "preloads") can markedly reduce postprandial glycemia by delaying gastric emptying, enhancing glucose-stimulated insulin release, and decreasing insulin clearance. The same improvement in glucose tolerance is achievable by optimal timing of carbohydrate ingestion during a meal (i.e., carbohydrate-last meal patterns), which minimizes the risk of body weight gain when compared with nutrient preloads. The magnitude of the glucose-lowering effect of preload-based nutritional strategies is greater in type 2 diabetes than healthy subjects, being comparable and additive to current glucose-lowering drugs, and appears sustained over time. This dietary approach has also shown promising results in pathological conditions characterized by postprandial hyperglycemia in which available pharmacological options are limited or not cost-effective, such as type 1 diabetes, gestational diabetes, and impaired glucose tolerance. Therefore, preload-based nutritional strategies, either alone or in combination with pharmacological treatments, may offer a simple, effective, safe, and inexpensive tool for the prevention and management of postprandial hyperglycemia. Here, we survey these novel physiological insights and their therapeutic implications for patients with diabetes mellitus and altered glucose tolerance.

Influence of rice, pea and oat proteins in attenuating glycemic response of sugar-sweetened beverages

PURPOSE

Liquids have higher ingestion and gastric-emptying rates, resulting in rapid glycemic response. They are also less satiating than solid foods. This study examined if the addition of plant proteins alter postprandial glucose, insulin, triglycerides, glucose-dependent insulinotropic peptide (GIP), glycogen-like peptide-1 (GLP-1) and appetitive responses to a sugar-sweetened beverage.

METHODS

This was a randomized, crossover acute feeding study consisting of four treatments: chocolate beverage alone (50 g carbohydrate), or added with 24 g oat, pea or rice proteins. Twenty Chinese males (mean ± SD age 26 ± 5 years; body mass index 21.5 ± 1.7 kg/m2) ingested the test drink after an overnight fast. Venous blood samples and subjective appetite ratings were collected before test beverage and at fixed intervals for 180 min. Blood biochemical data and appetite ratings were compared using repeated-measures ANOVA.

RESULTS

Significant interaction effects were found in postprandial glucose excursions (time × protein effects, p = 0.003). Glucose iAUC was lower in pea and rice proteins, although not significantly (p > 0.385). Insulin iAUC was significantly higher in the oat (p = 0.035) and pea (p = 0.036) protein beverages. GIP and GLP-1 release in a sub-sample (n = 10) followed a comparable order as insulin release (p = 0.397 and 0.454, respectively). Significant interaction effects were found in fullness ratings (p = 0.024), and a trend of greater suppression of hunger and desire-to-eat was also documented (p = 0.088 and 0.080, respectively).

CONCLUSIONS

Plant proteins altered the glycemic and appetitive responses of Asian males to a sugar-sweetened beverage. Food-based interventions are useful in promoting glycemic control. This trial was registered with ClinicalTrials.gov as NCT02933424.

Effect of a cod protein hydrolysate on postprandial glucose metabolism in healthy subjects: a double-blind cross-over trial

The increased prevalence of lifestyle diseases, such as the metabolic syndrome and type 2 diabetes mellitus (T2DM), calls for more knowledge on dietary treatments targeting the specific metabolic pathways involved in these conditions. Several studies have shown a protein preload before a meal to be effective in lowering the postprandial glycaemic response in healthy individuals and patients with T2DM. The aim of the present study was to assess the effect of a marine protein hydrolysate (MPH) from Atlantic cod (Gadus morhua) on postprandial glucose metabolism in healthy, middle-aged to elderly subjects. This double-blind cross-over trial (n 41) included two study days with 4–7 d wash-out in between. The intervention consisted of 20 mg of MPH (or casein as control) per kg body weight given before a breakfast meal. The primary outcome was postprandial response in glucose metabolism, measured by samples of serum glucose, insulin and plasma glucagon-like peptide 1 (GLP-1) in 20 min intervals for 180 min. In a mixed-model regression analysis, no differences were observed between MPH and control for postprandial glucose concentration (mean difference: −0·04 (95 % CI –0·17, 0·09) mmol/l; P = 0·573) or GLP-1 concentration (mean difference between geometric means: 1·02 (95 % CI 0·99, 1·06) pmol/l; P = 0·250). The postprandial insulin concentration was significantly lower after MPH compared with control (mean difference between geometric means: 1·067 (95 % CI 1·01, 1·13) mIU/l; P = 0·032). Our findings demonstrate that a single dose of MPH before a breakfast meal reduces postprandial insulin secretion, without affecting blood glucose response or GLP-1 levels, in healthy individuals. Further studies with repeated dosing and in target groups with abnormal glucose control are warranted.

Acute Effects of Substitution, and Addition, of Carbohydrates and Fat to Protein on Gastric Emptying, Blood Glucose, Gut Hormones, Appetite, and Energy Intake

Whey protein, when ingested on its own, load-dependently slows gastric emptying and stimulates gut hormone concentrations in healthy young men. The aim of this study was to determine the effects of substitution, and addition, of carbohydrate (dextrose) and fat (olive oil) to whey protein. In randomized, double-blind order, 13 healthy young men (age: 23 ± 1 years, body mass index: 24 ± 1 kg/m²) ingested a control drink (450 mL; ~2 kcal/'control') or iso-volumetric drinks containing protein/carbohydrate/fat: (i) 14 g/28 g/12.4 g (280 kcal/'M280'), (ii) 70 g/28 g/12.4 g (504kcal/'M504'), and (iii) 70 g/0 g/0 g (280 kcal/'P280'), on 4 separate study days. Gastric emptying (n = 11, 3D-ultrasonography), blood glucose, plasma insulin, ghrelin, cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) concentrations (0⁻180 min), appetite (visual analogue scales), and ad-libitum buffet-meal energy intake (180⁻210 min) were determined. Substitution of protein with carbohydrate and fat was associated with faster gastric emptying (lower 50% emptying time (T50)), reduced suppression of ghrelin, and stimulation of GLP-1 (all P < 0.001); while the addition of carbohydrate and fat to protein did not affect gastric emptying or gut hormone responses significantly. Total energy intake (i.e., drink plus meal) was greater after all caloric drinks than control (P < 0.001). In conclusion, substitution of whey protein with dextrose and olive oil accelerated gastric emptying. Higher protein content of a mixed macronutrient drink increased gut hormone and insulin responses.

Bidirectional Relationship between Gastric Emptying and Plasma Glucose Control in Normoglycemic Individuals and Diabetic Patients

Gastric emptying and glycemic control pathways are closely interrelated processes. Gastric chyme is transferred into the duodenum with velocities depending on its solid or liquid state, as well as on its caloric and nutritional composition. Once nutrients enter the intestine, the secretion of incretins (hormonal products of intestinal cells) is stimulated. Among incretins, glucagon-like peptide-1 (GLP-1) has multiple glycemic-regulatory effects that include delayed gastric emptying, thus triggering a feedback loop lowering postprandial serum glucose levels. Glycemic values also influence gastric emptying; hyperglycemia slows it down, and hypoglycemia accelerates it, both limiting glycemic fluctuations. Disordered gastric emptying in diabetes mellitus is understood today as a complex pathophysiological condition, with both irreversible and reversible components and high intra- and interindividual variability of time span and clinical features. While limited delays may be useful for reducing postprandial hyperglycemias, severely hindered gastric emptying may be associated with higher glycemic variability and worsened long-term glycemic control. Therapeutic approaches for both gastric emptying and glycemic control include dietary modifications of meal structure or content and drugs acting as GLP-1 receptor agonists. In the foreseeable future, we will probably witness a wider range of dietary interventions and more incretin-based medications used for restoring both gastric emptying and glycemic levels to nearly physiological levels.

Role of Intestinal Bitter Sensing in Enteroendocrine Hormone Secretion and Metabolic Control

The gastrointestinal tract stores ingested nutrients in the stomach which are then delivered to the small intestine at a controlled rate to optimize their digestion and absorption. The interaction of nutrients with the small and large intestine generates feedback that slows gastric emptying, induces satiation, and reduces postprandial glycemic excursions. The mechanisms underlying these nutrient-gut interactions are complex; it has only recently been appreciated that the gut has the capacity to detect intraluminal contents in much the same way as the tongue, via activation of specific G-protein-coupled receptors, and that ensuing signaling mechanisms modulate the release of an array of gut hormones that influence gastrointestinal motility, appetite and glycemia. Interestingly, evidence from preclinical models supports a functional link between intestinal bitter taste receptor (BTRs) and gastrointestinal hormone secretion, and the outcomes of recent studies indicate that stimulation of intestinal BTRs may be used to modulate gastrointestinal function, to diminish energy intake and limit postprandial blood glucose excursions in humans. This review summarizes current evidence about the expression and function of intestinal BTRs in relation to enteroendocrine hormone release and discusses the clinical implications of this pathway for the management of obesity and type 2 diabetes.

Effects of acute ingestion of whey protein with or without prior aerobic exercise on postprandial glycemia in type 2 diabetics

PURPOSE

Acute protein co-ingestion or a single bout of aerobic exercise can attenuate postprandial glycemia, but their combined effect has not been investigated in type 2 diabetics.

METHODS

Using a randomised crossover design, male type 2 diabetics (n = 8) [mean (95% CI); age, 55.0 (45.2, 64.8) year; BMI, 33.7 (25.6, 41.8) kg·m^- 2; 2 h glucose 14.0 (12.5, 15.5) mM] completed (1) 75 g oral glucose tolerance test (OGTT) (CON); (2) OGTT supplemented with 0.33 g·kg BM^- 1 of whey protein concentrate (PRO); or OGTT supplemented with PRO but preceded by a bout of aerobic cycling exercise (PRO + EX). Postprandial venous blood samples were collected for glucose, insulin, C-peptide and glucagon.

RESULTS

Despite a fold-increase of 1.90 (1.26, 2.56; p < 0.05) in postprandial insulin compared to CON, PRO failed to attenuate postprandial glycemia measured by 2 h glucose area under the curve. During PRO + EX, plasma glucose was elevated by 1.51 (0.5, 2.5) mM and 1.3 (0.3, 2.3) mM at 15 and 30 min, respectively, compared to CON, but was lower by 1.60 (0.6, 2.6) mM and 1.5 (0.5, 2.5) mM at 90 and 120 min, respectively (all p < 0.01). The additive effect of exercise and protein ingestion resulted in a fold-increase of 1.67 (1.35, 2.00; p < 0.05) in postprandial glucagon compared to CON.

CONCLUSION

In type 2 diabetics, prior aerobic exercise altered the humoral response to co-ingestion of whey protein with a carbohydrate load, but neither protein ingestion alone nor when preceded by prior exercise attenuated postprandial glycemia.

Postprandial Glycaemic, Hormonal and Satiety Responses to Rice and Kiwifruit Preloads in Chinese Adults: A Randomised Controlled Crossover Trial

Controlling postprandial glycaemia helps to prevent and manage non-communicable diseases. One strategy in controlling glycaemia may be to consume meals in two parts; a preload, followed by the remainder of the meal. Our aim was to test preloading a rice meal given for breakfast and lunch on different days, either by splitting the meal (rice preload followed by rice meal) or by using kiwifruit as a preload compared with consuming the rice meal in one sitting. Primary outcomes were glycaemic and insulinaemic responses with secondary outcomes of other hormonal responses, subjective satiety, and subsequent energy intake. Following breakfast, postprandial glycaemic peak concentration was 0.9 (95% CI: 0.2, 1.6) mmol/L lower for the kiwifruit preload compared with the rice meal eaten in one sitting. Following lunch, glycaemic peak concentrations were 1.0 (0.7, 1.4) and 1.1 (0.5, 1.7) mmol/L lower for the rice-split and kiwifruit preload compared with the rice meal alone, respectively. Postprandial insulinaemia area-under-the-curve was 1385 (87, 2684) mU/L·min less for the kiwifruit preload compared with the rice-split. There were no differences among treatments for subsequent energy intake. Meal splitting is useful for lowering postprandial glycaemia, and replacing part of a meal with kiwifruit may help with insulin efficiency without detriment to subsequent energy intake.

Rate of appearance of amino acids after a meal regulates insulin and glucagon secretion in patients with type 2 diabetes: a randomized clinical trial

Background

Meal composition regulates the postprandial response of pancreatic and gastrointestinal hormones and plays an important role in patients with type 2 diabetes (T2D). Proteins have glucagon and insulinotropic effects, which may differ depending on amino acid composition, form of intake, and rate of digestibility and absorption.

Objective

The aim of this study was to test effects of isolated pea protein-based (PP) compared with casein protein-based (CP) meals differing in amino acid compositions on endocrine responses to meal tolerance tests (MTTs) in patients with T2D.

Design

Thirty-seven individuals with T2D [mean ± SD age: 64 ± 6 y; mean ± SD body mass index (kg/m2): 30.2 ± 3.6; mean ± SD glycated hemoglobin: 7.0% ± 0.6%] were randomly assigned to receive either high-animal-protein (∼80% of total protein) or high-plant-protein (∼72% of total protein) diets (30% of energy from protein, 40% of energy from carbohydrate, 30% of energy from fat) for 6 wk. MTTs were performed at study onset and after 6 wk. Participants received standardized high-protein (30% of energy) meals 2 times/d containing either CP-rich (∼85% wt:wt) or PP-rich (∼95% wt:wt) foods.

Results

The CP and PP meals produced differences in insulin, C-peptide, glucagon, and glucose-dependent insulinotropic peptide (GIP) release. Total areas under the curve after CP were significantly lower than after the PP lunch by 40% for insulin and 23% for glucagon. Indexes of insulin sensitivity and secretion were significantly improved for the second CP MTT. This was accompanied by differential rates of appearance of amino acids. The ingestion of PP resulted in significant increases in amino acids after both meals, with a decline between meals. By contrast, CP intake resulted in increases in most amino acids after breakfast, which remained elevated but did not increase further after lunch.

Conclusions

PP elicits greater postprandial increases in glucagon than does CP and consequently requires higher insulin to control glucose metabolism, which appears to be related to the rate of amino acid appearance. The metabolic impact of protein quality could be used as a strategy to lower insulin needs in patients with T2D. This trial was registered at www.clinicaltrials.gov as NCT02402985.

The insulinotropic effect of a high-protein nutrient preload is mediated by the increase of plasma amino acids in type 2 diabetes

AIMS

Eating protein before carbohydrate reduces postprandial glucose excursions by enhancing insulin and glucagon-like peptide-1 (GLP-1) secretion in type 2 diabetes (T2D). We tested the hypothesis that this insulinotropic effect depends on the elevation of plasma amino acids (AA) after the digestion of food protein.

METHODS

In 16 T2D patients, we measured plasma AA levels through the course of two 75-g oral glucose tolerance tests (OGTT) preceded by either 500-ml water or a high-protein nutrient preload (50-g Parmesan cheese, one boiled egg, and 300-ml water). Changes in beta cell function were evaluated by measuring and modelling plasma glucose, insulin, and C-peptide through the OGTT. Changes in incretin hormone secretion were assessed by measuring plasma GLP-1.

RESULTS

Plasma AA levels were 24% higher after the nutrient preload (p < 0.0001). This increment was directly proportional to both the enhancement of beta cell function (r = 0.58, p = 0.02) and the plasma GLP-1 gradients (r = 0.57, p = 0.02) produced by the nutrient preload. Among single AA, glutamine showed the strongest correlation with changes in beta cell function (r = 0.61, p = 0.01), while leucine showed the strongest correlation with GLP-1 responses (r = 0.74, p = 0.001).

CONCLUSIONS

The elevation of circulating AA that occurs after a high-protein nutrient preload is associated with an enhancement of beta cell function and GLP-1 secretion in T2D. Manipulating the meal sequence of nutrient ingestion may reduce postprandial hyperglycaemia through a direct and GLP-1-mediated stimulation of insulin secretion by plasma AA.

TRIAL REGISTRATION NUMBER

NCT02342834.

The influence of food order on postprandial glucose levels in children with type 1 diabetes

OBJECTIVE

To evaluate the effect of the order of intake of carbohydrates, protein, and fat on postprandial glucose levels in children with type 1 diabetes (T1D). Our hypothesis was that postprandial glucose levels would be lower when fat and protein are consumed prior to carbohydrates, compared to a meal where all macronutrients are combined.

METHODS

A randomized, open-label, within-subject crossover study was conducted. Twenty patients aged 7 to 17 years diagnosed with T1D for >1 year consumed 2 isocaloric meals (with similar composition) in random order. In 1 meal, the protein and fat part was consumed 15 minutes prior to the carbohydrates (test meal). In the other meal, all macronutrients were consumed together (standard meal). Capillary blood glucose measurements and continuous glucose monitoring system were used to assess multiple glucose levels during a 3-hour postprandial period.

RESULTS

Overall, mean glucose levels were 1 mmol/L lower following the test meal compared to the standard meal (9.30 ± 3.20 vs 10.24 ± 3.35 mmol/L; P < .001). No significant difference in peak glucose was found. Glucose excursions were 1.5 and 1 mmol/L lower at 30 and 120 minutes following the test meal. A reduction in the total time period in which glucose levels exceeded 10 and 12 mmol/L of 28.7 (P = .001) and 22.3 minutes (P = .004), respectively, after the test meal was found.

CONCLUSIONS

This study shows that consumption of protein and fat prior to carbohydrates results in lower postprandial glucose levels and reduced glycemic variability in children with T1D.

Effects of Intragastric Administration of Tryptophan on the Blood Glucose Response to a Nutrient Drink and Energy Intake, in Lean and Obese Men

Tryptophan stimulates plasma cholecystokinin and pyloric pressures, both of which slow gastric emptying. Gastric emptying regulates postprandial blood glucose. Tryptophan has been reported to decrease energy intake. We investigated the effects of intragastric tryptophan on the glycaemic response to, and gastric emptying of, a mixed-nutrient drink, and subsequent energy intake. Lean and obese participants (n = 16 each) received intragastric infusions of 1.5 g ("Trp-1.5g") or 3.0 g ("Trp-3.0g") tryptophan, or control, and 15 min later consumed a mixed-nutrient drink (56 g carbohydrates). Gastric emptying (13C-acetate breath-test), blood glucose, plasma C-peptide, glucagon, cholecystokinin and tryptophan concentrations were measured (t = 0-60 min). Energy intake was assessed between t = 60-90 min. In lean individuals, Trp-3.0g, but not Trp-1.5g, slowed gastric emptying, reduced C-peptideAUC and increased glucagonAUC (all P < 0.05), but did not significantly decrease the blood glucose response to the drink, stimulate cholecystokinin or reduce mean energy intake, compared with control. In obese individuals, Trp-3.0g, but not Trp-1.5g, tended to slow gastric emptying (P = 0.091), did not affect C-peptideAUC, increased glucagonAUC (P < 0.001) and lowered blood glucose at t = 30 min (P < 0.05), and did not affect cholecystokinin or mean energy intake. In obese individuals, intragastrically administered tryptophan may reduce postprandial blood glucose by slowing gastric emptying; the lack of effect on mean energy intake requires further investigation.

A pre-meal of whey proteins induces differential effects on glucose and lipid metabolism in subjects with the metabolic syndrome: a randomised cross-over trial

PURPOSE

Postprandial lipaemia (PPL), an independent risk factor for cardiovascular disease, is affected by composition and timing of meals. We evaluated if whey proteins (WP) consumed as a pre-meal before a fat-rich meal reduce postprandial triglyceride (TG) and apolipoprotein B-48 (ApoB-48) responses in subjects with the metabolic syndrome (MeS).

METHODS

An acute, randomised, cross-over trial was conducted. 20 subjects with MeS consumed a pre-meal of 0, 10 or 20 g WP 15 min prior to a fat-rich meal. The responses of TG and ApoB-48 were assessed. We also analysed postprandial responses of free fatty acids (FFA), glucose, insulin, glucagon, glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and paracetamol (reflecting gastric emptying rates).

RESULTS

WP pre-meal did not alter the TG or ApoB-48 responses. In contrast, the insulin response was more pronounced after a pre-meal of 20 g WP than with 10 g WP (P = 0.0005) and placebo (P < 0.0001). Likewise, the postprandial glucagon response was greater with a pre-meal of 20 g WP than with 10 g WP (P < 0.0001) and 0 g WP (P < 0.0001). A pre-meal with 20 g of WP generated lower glucose (P = 0.0148) and S-paracetamol responses (P = 0.0003) and a higher GLP-1 response (P = 0.0086) than placebo. However, the pre-meal did not influence responses of GIP, FFA or appetite assessed by a Visual Analog Scale.

CONCLUSIONS

Consumption of a WP pre-meal prior to a fat-rich meal did not affect TG and chylomicron responses. In contrast, the WP pre-meal stimulates insulin and glucagon secretion and reduces blood glucose as expected, and delays gastric emptying. Consequently, our study points to a differential impact of a WP pre-meal on lipid and glucose metabolism to a fat-rich meal in subjects with MeS.

Comparable effects of breakfast meals varying in protein source on appetite and subsequent energy intake in healthy males

PURPOSE

The satiating effect of animal vs plant proteins remains unknown. The present study examined the effects of breakfasts containing animal proteins [milk (AP)], a blend of plant proteins [oat, pea and potato (VP)] or 50:50 mixture of the two (MP) compared with a carbohydrate-rich meal (CHO) on appetite, energy intake (EI) and metabolic measures.

METHODS

A total of 28 males [mean age 27.4 (±SD 4.2) years, BMI 23.4 (±2.1) kg/m2] consumed three isoenergetic (1674 kJ) rice puddings matched for energy density and macronutrient content as breakfast (25% E from protein) in a single-blind, randomised, cross over design. Appetite ratings and blood samples were collected and assessed at baseline and every 30 and 60 min, respectively, until an ad libitum test meal was served 3.5 h later. Free-living appetite was recorded hourly and EI in weighed food records for the remainder of the day.

RESULTS

No differences in subjective appetite ratings were observed after consumption of the AP, VP and MP. Furthermore, there were no differences between the AP, VP, MP and CHO breakfasts in ad libitum EI and self-reported EI during the remainder of the day. Although insulin metabolism was not affected, CHO induced a higher glucose response (P = 0.001) and total amino acids concentration was in the order of AP = MP > VP > CHO breakfast (P = 0.001).

CONCLUSION

Manipulating the protein source of foods consumed as breakfast, elicited comparable effects on appetite and EI at both laboratory and free-living environment in healthy men.