Wheat gluten hydrolysate potently stimulates peptide-YY secretion and suppresses food intake in rats

Plant-based meat analogues enhance the gastrointestinal motility function and appetite of mice by specific volatile compounds and peptides

Eating behavior is critical for maintaining energy homeostasis. Previous studies have found that plant-based meat analogues increased diet intake in mice compared with animal meat under a free feeding mode, however the reasons were unclear. To explore the underlying mechanisms of plant-based meat analogues increasing diet intake, mice were fed animal or plant-based pork and beef analogue diets, respectively. Biochemical and histological analyses were performed to evaluate appetite-regulating hormones and gastrointestinal motility function. Peptiomics and GC-IMS were applied to identify key substances. We found that the intake of plant-based meat analogues significantly enhanced the gastrointestinal motility function of mice. The long-term intake (68 days) of plant-based meat analogues significantly increased the muscle layer thickness of the duodenum and jejunum of mice; the activity of gastrointestinal cells of Cajal were also promoted by upregulating the expression of c-kit related signals as compared to animal meat; plant-based meat analogues intake markedly enhanced the signal intensity of the intestinal neurotransmitter 5-hydroxytryptamine (5-HT) by upregulating the expression of 5-HT synthase and receptors but downregulating its transporter and catabolic enzyme in the intestine. Moreover, plant-based meat analogues intake significantly increased levels of appetite-stimulating factors in the peripheral or hypothalamus but reduced levels of appetite-suppressing factors compared with animal meat. Specific volatile compounds were significantly associated with appetite regulating factors. Among them, 7 substances such as linalool have a potential promoting effect on food intake. Besides, different digestive peptides in gastrointestinal tract may affect eating behavior mainly through the neuroactive ligand-receptor interaction pathway, exerting hormone-like effects or influencing endocrine cell secretion. These findings preliminarily clarified the mechanism of plant-based meat analogues promoting diet intake and provided a theoretical basis for a reasonable diet.

The impacts and mechanisms of dietary proteins on glucose homeostasis and food intake: a pivotal role of gut hormones

Glucose and energy metabolism disorders are the main reasons induced type 2 diabetes (T2D) and obesity. Besides providing energy, dietary nutrients could regulate glucose homeostasis and food intake via intestinal nutrient sensing induced gut hormone secretion. However, reviews regarding intestinal protein sensing are very limited, and no accurate information is available on their underlying mechanisms. Through intestinal protein sensing, dietary proteins regulate glucose homeostasis and food intake by secreting gut hormones, such as glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), peptide YY (PYY) and glucose-dependent insulinotropic polypeptide (GIP). After activating the sensory receptors, such as calcium-sensing receptor (CaSR), peptide transporter-1 (PepT1), and taste 1 receptors (T1Rs), protein digests induced Ca2+ influx and thus triggered gut hormone release. Additionally, research models used to study intestinal protein sensing have been emphasized, especially several innovative models with excellent physiological relevance, such as co-culture cell models, intestinal organoids, and gut-on-a-chips. Lastly, protein-based dietary strategies that stimulate gut hormone secretion and inhibit gut hormone degradation are proposed for regulating glucose homeostasis and food intake.

Do gluten peptides stimulate weight gain in humans?

Observations from animal and in vitro laboratory research, and anecdotal evidence, have led to the suggestion that gluten consumption stimulates weight gain by the presence of peptides expressing opioid activity. Another proposed mechanism is that gluten peptides decrease resting energy expenditure resulting in a positive energy balance. In order to induce such effects in vivo, intact food peptides must be absorbed in sufficient quantities, remain intact in the blood for sufficient time to have long‐lasting biological activity and bind to receptors involved in appetite, satiety and energy regulation. However, although peptides from food may pass from the intestine into the blood in extremely low quantities, they are generally rapidly degraded by plasma and vasculum‐bound aminopeptidases, resulting in very short half‐lives and loss of bioactivity. At present, gluten peptide sequences that influence regulators of energy metabolism have not been identified. Furthermore, data on the quantitative absorption of gluten peptides in the blood stream, their stability and lasting bioactivity are also lacking. Therefore, there is no evidence for proposed effects on driving appetite by the brain, nor on energy expenditure and weight gain. Furthermore, the level of overweight observed in various countries appears to be independent of the level of wheat consumption, and abundant observational evidence in humans shows that the levels of gluten consumption are neither related to daily calorie intake nor to BMI. This narrative review therefore discusses the proposed effects of gluten on bodyweight (BW) and putative biological mechanisms in the light of the current evidence.

A comprehensive review on the glucoregulatory properties of food-derived bioactive peptides

Diabetes mellitus, a group of metabolic disorders characterized by persistent hyperglycemia, affects millions of people worldwide and is on the rise. Dietary proteins, from a wide range of food sources, are rich in bioactive peptides with antidiabetic properties. Notable examples include AGFAGDDAPR, a black tea-derived peptide, VRIRLLQRFNKRS, a β-conglycinin-derived peptide, and milk-derived peptide VPP, which have shown antidiabetic effects in diabetic rodent models through variety of pathways including improving beta-cells function, suppression of alpha-cells proliferation, inhibiting food intake, increasing portal cholecystokinin concentration, enhancing insulin signaling and glucose uptake, and ameliorating adipose tissue inflammation. Despite the immense research on glucoregulatory properties of bioactive peptides, incorporation of these bioactive peptides in functional foods or nutraceuticals is widely limited due to the existence of several challenges in the field of peptide research and commercialization. Ongoing research in this field, however, is fundamental to pave the road for this purpose.

Blue Whiting (Micromesistius poutassou) Protein Hydrolysates Increase GLP-1 Secretion and Proglucagon Production in STC-1 Cells Whilst Maintaining Caco-2/HT29-MTX Co-Culture Integrity

Inducing the feeling of fullness via the regulation of satiety hormones presents an effective method for reducing excess energy intake and, in turn, preventing the development of obesity. In this study, the ability of blue whiting soluble protein hydrolysates (BWSPHs) and simulated gastrointestinal digested (SGID) BWSPHs, to modulate the secretion and/or production of satiety hormones, such as glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK) and peptide YY (PYY), was assessed in murine enteroendocrine STC-1 cells. All BWSPHs (BW-SPH-A to BW-SPH-F) (1.0% w/v dw) increased active GLP-1 secretion and proglucagon production in STC-1 cells compared to the basal control (Krebs–Ringer buffer) (p < 0.05). The signaling pathway activated for GLP-1 secretion was also assessed. A significant increase in intracellular calcium levels was observed after incubation with all BWSPHs (p < 0.05) compared with the control, although none of the BWSPHs altered intracellular cyclic adenosine monophosphate (cAMP) concentrations. The secretagogue effect of the leading hydrolysate was diminished after SGID. Neither pre- nor post-SGID hydrolysates affected epithelial barrier integrity or stimulated interleukin (IL)-6 secretion in differentiated Caco-2/HT-29MTX co-cultured cells. These results suggest a role for BWSPH-derived peptides in satiety activity; however, these peptides may need to be protected by some means to avoid loss of activity during gastrointestinal transit.

An Exploratory Study of the Role of Dietary Proteins in the Regulation of Intestinal Glucose Absorption

Several studies have demonstrated that high protein diets improve glucose homeostasis. Nevertheless, the mechanisms underlying this effect remain elusive. This exploratory study aims to screen and compare the acute effects of dietary proteins from different sources on intestinal glucose absorption. Six dietary proteins from various sources were thus selected and digested thanks to the INFOGEST static gastrointestinal digestion protocol. The digested proteins were able to decrease intestinal glucose absorption in vitro and ex vivo. Moreover, acute ingestion of casein and fish gelatin led to improved glucose tolerance in Wistar rats without significant effect on insulin secretion. In parallel, GLUT2 mRNA expression in enterocytes was decreased following short-term incubation with some of the digested proteins. These results strengthen the evidence that digested protein-derived peptides and amino acids are key regulators of glucose homeostasis and highlight their role in intestinal glucose absorption.

Soybean protein hydrolysate stimulated cholecystokinin secretion and inhibited feed intake through calcium-sensing receptors and intracellular calcium signalling in pigs

Although soybean protein is the major component in livestock feeds, its effect on pigs' appetites is largely unknown. Recently, the importance of gut nutrient-sensing for appetite modulation by regulating anorectic gut hormone release has been recognised. This study investigates the roles of soybean proteins in appetite regulation, anorectic gut hormone secretion, and underlying mechanisms. The duodenal-cannulated piglets were used to evaluate the effects of soybean protein hydrolysate (SPH) on feed intake and anorectic hormone release, including cholecystokinin (CCK), peptide YY (PYY), glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) in the hepatic vein by infusing SPH. Identifying which nutrient-sensing receptor in pig duodenum response to SPH stimulation for gut hormone release was conducted. Using its antagonist, the role of the identified receptor in feed intake and anorectic hormone release was also investigated. Combination with an ex vivo perfusion system, the possible mechanism by which SPH exerts the effects in porcine duodenum was further illustrated. Results in vivo showed that intraduodenal infusion of SPH inhibited short-term feed intake in pigs and promoted CCK, PYY, and GIP secretion in the hepatic vein. SPH also increased duodenum calcium-sensing receptor (CaSR) expression. Pre-treated with CaSR antagonist NPS 2143, the feed intake of pigs tended to be attenuated by SPH (P = 0.09), and CCK release was also suppressed (P < 0.05), indicating that CaSR was involved in SPH-stimulated CCK release and inhibited feed intake in pigs. The ex vivo perfused duodenum tissues revealed that SPH-triggered CCK secretion was likeliest due to the activation of the intracellular Ca²⁺/TRPM5 pathway. Overall, this study's result illustrates that the diet soybean protein might decrease appetite in pigs by triggering duodenum CCK secretion by activating CaSR and the intracellular Ca²⁺/TRPM5 pathway.

Impact of food-derived bioactive peptides on gut function and health

The gastrointestinal tract (GIT) is the largest interface between our body and the environment. It is an organ system extending from the mouth to the anus and functions for food intake, digestion, transport and absorption of nutrients, meanwhile providing protection from environmental factors, like toxins, antigens, and pathogens. Diet is one of the leading factors modulating the function of the GIT. Bioactive peptides presenting naturally in food or derived from food proteins during digestion or processing have been revealed multifunctional in diverse biological processes, including maintaining gut health and function. This review summarizes the available evidence regarding the effects of food-derived bioactive peptides on gut function and health. Findings and insights from studies based on in vitro and animal models are discussed. The gastrointestinal mucosa maintains a delicate balance between immune tolerance to nutrients and harmful components, which is crucial for the digestive system's normal functions. Dietary bioactive peptides positively impact gastrointestinal homeostasis by modulating the barrier function, immune responses, and gut microbiota. However, there is limited clinical evidence on the safety and efficacy of bioactive peptides, much less on the applications of dietary peptides for the treatment or prevention of diseases related to the GIT. Further study is warranted to establish the applications of bioactive peptides in regulating gut health and function.

Glucagon-like peptide-1 regulation by food proteins and protein hydrolysates

Glucagon-like peptide-1 (GLP-1) is an enterohormone with a key role in several processes controlling body homeostasis, including glucose homeostasis and food intake regulation. It is secreted by the intestinal cells in response to nutrients, such as glucose, fat and amino acids. In the present review, we analyse the effect of protein on GLP-1 secretion and clearance. We review the literature on the GLP-1 secretory effects of protein and protein hydrolysates, and the mechanisms through which they exert these effects. We also review the studies on protein from different sources that has inhibitory effects on dipeptidyl peptidase-4 (DPP4), the enzyme responsible for GLP-1 inactivation, with particular emphasis on specific sources and treatments, and the gaps there still are in knowledge. There is evidence that the protein source and the hydrolytic processing applied to them can influence the effects on GLP-1 signalling. The gastrointestinal digestion of proteins, for example, significantly changes their effectiveness at modulating this enterohormone secretion in both in vivo and in vitro studies. Nevertheless, little information is available regarding human studies and more research is required to understand their potential as regulators of glucose homeostasis.

Proteins and peptides from vegetable food sources as therapeutic adjuvants for the type 2 diabetes mellitus

Proteins and peptides are fundamental components of the cereals, pseudocereals, and legumes, giving them numerous health-beneficial properties. Previous studies have demonstrated that these molecules exerted effects on current therapeutic targets related to type 2 diabetes mellitus, such as incretin hormones (responsible for appetite suppression), dipeptidyl peptidase IV (an enzyme involved in the inactivation and degradation of the incretin hormones), and glucose transporters (molecules that transport glucose in or out of cells). Therefore, this review presents the current biological activity of protein derivatives and peptides isolated from cereals, pseudocereals, and legumes on these therapeutic markers, highlighting their potential as a possible pharmacological treatment for type 2 diabetes mellitus.

Explorative Screening of Bioactivities Generated by Plant-Based Proteins after In Vitro Static Gastrointestinal Digestion

The gastrointestinal digestion of food proteins can generate peptides with a wide range of biological activities. In this study, we screened various potential bioactivities generated by plant-based proteins. Whey protein as an animal protein reference, five grades of pea protein, two grades of wheat protein, and potato, fava bean, and oat proteins were submitted to in vitro SGID. They were then tested in vitro for several bioactivities including measures on: (1) energy homeostasis through their ability to modulate intestinal hormone secretion, to inhibit DPP-IV activity, and to interact with opioid receptors; (2) anti-hypertensive properties through their ability to inhibit ACE activity; (3) anti-inflammatory properties in Caco-2 cells; (4) antioxidant properties through their ability to inhibit production of reactive oxygen species (ROS). Protein intestinal digestions were able to stimulate intestinal hormone secretion by enteroendocrine cells, to inhibit DPP-IV and ACE activities, to bind opioid receptors, and surprisingly, to decrease production of ROS. Neither pro- nor anti-inflammatory effects have been highlighted and some proteins lost their pro-inflammatory potential after digestion. The best candidates were pea, potato, and fava bean proteins.