Transepithelial transport of milk derived bioactive peptide VLPVPQK

Functional attributes of bioactive peptides of bovine milk origin and application of in silico approaches for peptide prediction and functional annotations

Bovine milk peptides are the protein fragments with diverse bioactive properties having antioxidant, anticarcinogenic, other therapeutic and nutraceutical potentials. These peptides are formed in milk by enzymatic hydrolysis, gastrointestinal digestion and fermentation processes. They have significant health impact with high potency and low toxicity making them a suitable natural alternative for preventing and managing diseases. Antibiotic resistance has increased the quest for better peptide candidates with antimicrobial effects. This article presents a comprehensive review on well documented antimicrobial, immunological, opioid, and anti-hypertensive activities of bovine milk peptides. It also covers the usage of computational biology tools and databases for prediction and analysis of the food-derived bioactive peptides. In silico analysis of amino acid sequences of Bos taurus milk proteins have been predicted to generate peptides with dipeptidyl peptidase IV inhibitory and ACE inhibitory properties, making them favorable candidates for developing blood sugar lowering drugs and anti-hypertensives. In addition to the prediction of new bioactive peptides, application of bioinformatics tools to predict novel functions of already known peptides is also discussed. Overall, this review focuses on the reported as well as predicted biologically active peptide of casein and whey proteins of bovine milk that can be utilized to develop therapeutic agents.

Identification of flavor peptides based on virtual screening and molecular docking from Hypsizygus marmoreuss

Hypsizygus marmoreuss is an under-explored source of flavor peptides that can enhance the flavor of NaCl or MSG, allowing products to be reformulated in line with reduction policies. This study utilized advanced techniques, including UPLC-Q-TOF MS/MS and molecular docking, to identify H. marmoreuss peptides. Sensory evaluations revealed 10 peptides with pronounced umami flavors and seven with dominantly salty tastes. VLPVPQK scored highest for umami intensity (5.2), and EGNPAHQK for salty intensity (6.2). Further investigation influenced by 0.35 % MSG or 0.35 % NaCl exposed peptides with elevated umami and salty thresholds. LDSPATPEK, VVEGEPSLK, and QKLPEKPER had umami-enhancing thresholds of 0.18, 0.18, and 0.35 mM, while LDSPATPEK and VVEGEPSLK had similar thresholds for salt (0.09 mM). Molecular docking revealed that taste receptor proteins interacted with umami peptides through hydrogen, carbon-hydrogen, alkyl, and van der Waals forces. Specific amino acids in the umami receptor T1R1 had roles in bonding with umami peptides through hydrogen and carbon-hydrogen interactions. In conclusion, molecular docking proved to be an effective and efficient method for flavor peptide screening. Further, this study demonstrated that flavor peptides from H. marmoreuss had the capacity to enhance NaCl and MSG flavours and might be useful tools for reformulation, reducing salt and MSG contents.

Glutamine-derived peptides: Current progress and future directions

Glutamine, the most abundant amino acid in the body, plays a critical role in preserving immune function, nitrogen balance, intestinal integrity, and resistance to infection. However, its limited solubility and instability present challenges for its use a functional nutrient. Consequently, there is a preference for utilizing glutamine-derived peptides as an alternative to achieve enhanced functionality. This article aims to review the applications of glutamine monomers in clinical, sports, and enteral nutrition. It compares the functional effectiveness of monomers and glutamine-derived peptides and provides a comprehensive assessment of glutamine-derived peptides in terms of their classification, preparation, mechanism of absorption, and biological activity. Furthermore, this study explores the potential integration of artificial intelligence (AI)-based peptidomics and synthetic biology in the de novo design and large-scale production of these peptides. The findings reveal that glutamine-derived peptides possess significant structure-related bioactivities, with the smaller molecular weight fraction serving as the primary active ingredient. These peptides possess the ability to promote intestinal homeostasis, exert hypotensive and hypoglycemic effects, and display antioxidant properties. However, our understanding of the structure-function relationships of glutamine-derived peptides remains largely exploratory at current stage. The combination of AI based peptidomics and synthetic biology presents an opportunity to explore the untapped resources of glutamine-derived peptides as functional food ingredients. Additionally, the utilization and bioavailability of these peptides can be enhanced through the use of delivery systems in vivo. This review serves as a valuable reference for future investigations of and developments in the discovery, functional validation, and biomanufacturing of glutamine-derived peptides in food science.

Intestinal absorption of bioactive oligopeptides: paracellular transport and tight junction modulation

Bioactive oligopeptides have gained increasing attention due to their diverse physiological functions, and these can be transported into the vasculature via transcellular and paracellular pathways. Among these, paracellular transport through the intercellular space is a passive diffusion process without energy consumption. It is currently the most frequently reported absorption route for food-derived bioactive oligopeptides. Previous work has demonstrated that paracellular pathways are mainly controlled by tight junctions, but the mechanism by which they regulate paracellular absorption of bioactive oligopeptides remains unclear. In this review, we summarized the composition of paracellular pathways across the intercellular space and elaborated on the paracellular transport mechanism of bioactive oligopeptides in terms of the interaction between oligopeptides and tight junction proteins, the protein expression level of tight junctions, the signaling pathways regulating intestinal permeability, and the properties of oligopeptides themselves. These findings contribute to a more profound understanding of the paracellular absorption of bioactive oligopeptides.

Investigating the Transepithelial Transport and Enzymatic Stability of Lactononadecapeptide (NIPPLTQTPVVVPPFLQPE), a 19-Amino Acid Casein-Derived Peptide in Caco-2 Cells

Lactononadecapeptide (LNDP; NIPPLTQTPVVVPPFLQPE), a casein-derived peptide comprising 19 residues, is known for its capacity to enhance cognitive function. This study aimed to explore the transepithelial transport and stability of LNDP. Results showed that LNDP retained over 90% stability after 2 h of treatment with gastrointestinal enzymes. The stability of LNDP on Caco-2 cell monolayers ranged from 93.4% ± 0.9% to 101.1% ± 1.2% over a period of 15-60 min, with no significant differences at each time point. The permeability of LNDP across an artificial lipid membrane was very low with the effective permeability of 3.6 × 10-11 cm/s. The Caco-2 assay demonstrated that LNDP could traverse the intestinal epithelium, with an apparent permeability of 1.22 × 10-6 cm/s. Its transport was significantly inhibited to 67.9% ± 5.0% of the control by Gly-Pro, a competitor of peptide transporter 1 (PEPT1). Furthermore, PEPT1 knockdown using siRNA significantly inhibited LNDP transport by 77.6% ± 1.9% in Caco-2 cell monolayers. The LNDP uptake in PEPT1-expressing HEK293 cells was significantly higher (54.5% ± 14.6%) than that in mock cells. These findings suggest that PEPT1 plays a crucial role in LNDP transport, and LNDP exhibits good resistance to gastrointestinal enzymes.

Bioactive peptides in dry-cured ham: A comprehensive review of preparation methods, metabolic stability, safety, health benefits, and regulatory frameworks

Dry-cured hams contain abundant bioactive peptides with significant potential for the development of functional foods. However, the limited bioavailability of food-derived bioactive peptides has hindered their utilization in health food development. Moreover, there is insufficient regulatory information regarding bioactive peptides and related products globally. This review summarizes diverse bioactive peptides derived from dry-cured ham and by-products originating from various countries and regions. The bioactivity, preparation techniques, bioavailability, and metabolic stability of these bioactive peptides are described, as well as the legal and regulatory frameworks in various countries. The primary objectives of this review are to dig deeper into the functionality of dry-cured ham and provide theoretical support for the commercialization of bioactive peptides from food sources, especially the dry-cured ham.

An Overview of the Occurrence of Bioactive Peptides in Different Types of Cheeses

The search for improvements in quality of life has increasingly involved changes in the diet, especially the consumption of foods which, in addition to having good nutritional value, are characterized by offering health benefits. Among the molecules that trigger several beneficial responses are peptides, which are specific fragments of proteins known to produce positive effects on the human body. This review aimed to discuss the bioactive potential of peptides from cheeses. Studies show that the protein composition of some cheese varieties exhibits a potential for the release of bioactive peptides. The production of these peptides can be promoted by some technological procedures that affect the milk structure and constituents. The cheese maturation process stands out for producing bioactive peptides due to the action of enzymes produced by lactic acid bacteria. Thus, in addition to being proteins with high biological value due to their excellent amino acid profile, peptides from some types of cheeses are endowed with functional properties such as anti-hypertensive, antimicrobial, antioxidant, anticarcinogenic, opioid, and zinc-binding activities.

Absorption of egg white hydrolysate in the intestine: Clathrin-dependent endocytosis as the main transport route

This paper aimed to investigate the in vivo absorption of egg white hydrolysate (EWH) in rats and the transport route across the intestinal epithelium. Results showed that the level of plasma peptide-bound amino acid (PAA) of the EWH-supplemented rats (EWH-R) was determined to be 2012.18 ± 300.98 μmol/L, 10.72% higher than that of the control group, and was significantly positively correlated to that of EWH. Thirty-three egg white-derived peptides were successfully identified from the plasma of EWH-R, and 20 of them were found in both EWH-R plasma and EWH, indicating that these peptides tend to be absorbed through the intestinal epithelium in intact forms into the blood circulation. In addition, 637 up-regulated and 577 down-regulated genes in Caco-2 cells incubated with EWH were detected by RNA-sequencing and the clathrin-dependent endocytosis was the most enriched pathway in KEGG analysis. EWH significantly increased the mRNA levels of the key genes involved in the clathrin-dependent endocytosis but these changes would be inhibited by the clathrin-dependent endocytosis inhibitor of chlorpromazine. Moreover, the transepithelial transport of EWH across Caco-2 cell monolayers was significantly reduced by chlorpromazine. This study provided molecular-level evidence for the first time that clathrin-dependent endocytosis might be the main transport route of EWH in the intestinal epithelium.

Transepithelial Transport of the Bifunctional Peptide IPYWTY Indirectly Induced Insulin Release Mediated by Active GLP-1

There is currently no appropriate cell model suitable for evaluating the insulinotropic effects of DPP-4 inhibitory peptides (DPP-4IPs) mediated by active glucagon-like peptide-17-36 (active GLP-1). The study aims to evaluate the transepithelial transport of IPYWTY on its in situ insulinotropic effects by using a 2D and dual-layered coculture cell model that consists of Caco-2 and NCI-H716 cells on the apical (AP) side and β-TC-6 cells on the basolateral (BL) side. During transportation, IPYWTY was absorbed in its intact form through PepT1 and paracellular transport. Meanwhile, it was degraded to several peptide fragments, including PYWTY, YWTY, WTY, and IPY, which decreased its in situ DPP-4 inhibitory activity. IPYWTY does not directly stimulate insulin release in β-TC-6 cells, while it increased the active GLP-1 level from 76.57 ± 15.16 to 95.63 ± 1.99 pM (1.25 times) in NCI-H716 cells. Interestingly, IPYWTY indirectly increased insulin levels from 426.91 ± 6.07 to 573.94 ± 2.97 μIU/mL (1.34 times) in the 2D and dual-layered coculture cell model for its dual function of stimulating active GLP-1 secretion and DPP-4 inhibition. These results suggested that the 2D and dual-layered coculture cell model is an alternative strategy for effectively evaluating the insulinotropic effects of DPP-4IPs mediated by active GLP-1.

The Effects and Regulatory Mechanism of Casein-Derived Peptide VLPVPQK in Alleviating Insulin Resistance of HepG2 Cells

The liver plays a key role in keeping the homeostasis of glucose and lipid metabolism. Insulin resistance of the liver induced by extra glucose and lipid ingestion contributes greatly to chronic metabolic disease, which is greatly threatening to human health. The small peptide, VLPVPQK, originating from casein hydrolysates of milk, shows various health-promoting functions. However, the effects of VLPVPQK on metabolic disorders of the liver are still not fully understood. Therefore, in the present study, the effects and regulatory mechanism of VLPVPQK on insulin-resistant HepG2 cells was further investigated. The results showed that VLPVPQK exerted strong scavenging capacities against various free radicals, including oxygen radicals, hydroxyl radicals, and cellular reactive oxygen species. In addition, supplementation of VLPVPQK (62.5, 125, and 250 μM) significantly reversed the high glucose and fat (30 mM glucose and 0.2 mM palmitic acid) induced decrement of glucose uptake in HepG2 cells without affecting cell viability. Furthermore, VLPVPQK intervention affected the transcriptomic profiling of the cells. The differentially expressed (DE) genes (FDR < 0.05, and absolute fold change (FC) > 1.5) between VLPVPQK and the model group were mostly enriched in the carbohydrate metabolism-related KEGG pathways. Interestingly, the expression of two core genes (HKDC1 and G6PC1) involved in the above pathways was dramatically elevated after VLPVPQK intervention, which played a key role in regulating glucose metabolism. Furthermore, supplementation of VLPVPQK reversed the high glucose and fat-induced depression of AKR1B10. Overall, VLPVPQK could alleviate the metabolic disorder of hepatocytes by elevating the glucose uptake and eliminating the ROS, while the HKDC1 and AKR1B10 genes might be the potential target genes and play important roles in the process.

Effect of Fermentation with Streptococcus thermophilus Strains on In Vitro Gastro-Intestinal Digestion of Whey Protein Concentrates

Three Streptococcus thermophilus strains, namely RBC6, RBC20, and RBN16, were proven to release bioactive peptides during whey protein concentrate (WPC) fermentation, resulting in WPC hydrolysates with biological activities. However, these bioactive peptides can break down during gastro-intestinal digestion (GID), hindering the health-promoting effect of fermented WPC hydrolysates in vivo. In this work, the effect of simulated GID on three WPC hydrolysates fermented with S. thermophilus strains, as well as on unfermented WPC was studied in terms of protein hydrolysis, biological activities, and peptidomics profiles, respectively. In general, WPC fermentation enhanced protein hydrolysis compared to unfermented WPC. After in vitro GID, WPC fermented with S. thermophilus RBC20 showed the highest antioxidant activity, whereas WPC fermented with strain RBC06 displayed the highest angiotensin-converting enzyme (ACE)- and dipeptidyl peptidase IV (DPP-IV)-inhibitory activities. Peptidomics analysis revealed that all digested WPC samples were highly similar to each other in peptide profiles, and 85% of the 46 identified bioactive peptides were shared among fermented and unfermented samples. However, semi-quantitative analysis linked the observed differences in biological activities among the samples to differences in the amount of bioactive peptides. The anti-hypertensive peptides VPP and IPP, as well as the DPP-IV-inhibitory peptide APFPE, were quantified. In conclusion, WPC fermentation with S. thermophilus positively impacted protein hydrolysis and bioactive peptide release during GID.

Potential of Food Protein-Derived Bioactive Peptides against Sarcopenia: A Comprehensive Review

Sarcopenia is an age-related progressive muscle disorder characterized by accelerated loss of muscle mass, strength, and function, which are important causes of physiological dysfunctions in the elderly. At present, the main alleviating method includes protein supplements to stimulate synthesis of muscle proteins. Food protein-derived peptides containing abundant branched-chain amino acids have a remarkable effect on the improvement of sarcopenia. Understanding the underlying molecular mechanism and clarifying the structure-activity relationship is essential for the mitigation of sarcopenia. This present review recaps the epidemiology, pathogenesis, diagnosis, and treatment of sarcopenia, which facilitates a comprehensive understanding of sarcopenia. Moreover, the latest research progress on food-derived antisarcopenic peptides is reviewed, including their antisarcopenic activity, molecular mechanism as well as structural characteristics. Food-derived bioactive peptides can indeed alleviate/mitigate sarcopenia. These antisarcopenic peptides play a pivotal role mainly by activating the PI3K/Akt/mTOR and MAPK pathways and inhibiting the ubiquitin-proteasome system and AMPK pathway, thus promoting the synthesis of muscle proteins and inhibiting their degradation. Antisarcopenic peptides alleviate sarcopenia via specific peptides, which may be absorbed into the circulation and exhibit their bioactivity in intact forms. The present review provides a theoretical reference for mitigation and prevention of sarcopenia by food protein-derived bioactive peptides.

In Silico Identification of Peptides with PPARγ Antagonism in Protein Hydrolysate from Rice (Oryza sativa)

At least half the population in industrialized countries suffers from obesity due to excessive accumulation of adipose tissue. Recently, rice (Oryza sativa) proteins have been considered valuable sources of bioactive peptides with antiadipogenic potential. In this study, the digestibility and bioaccessibility in vitro of a novel protein concentrate (NPC) from rice were determined through INFOGEST protocols. Furthermore, the presence of prolamin and glutelin was evaluated via SDS-PAGE, and their potential digestibility and the bioactivity of ligands against peroxisome proliferator-activated receptor gamma (PPARγ) were explored by BIOPEP UWM and HPEPDOCK. For the top candidates, molecular simulations were conducted using Autodock Vina to evaluate their binding affinity against the antiadipogenic region of PPARγ and their pharmacokinetics and drug-likeness using SwissADME. Simulating gastrointestinal digestion showed a recovery of 43.07% and 35.92% bioaccessibility. The protein banding patterns showed the presence of prolamin (57 kDa) and glutelin (12 kDa) as the predominant proteins in the NPC. The in silico hydrolysis predicts the presence of three and two peptide ligands in glutelin and prolamin fraction, respectively, with high affinity for PPARγ (≤160). Finally, the docking studies suggest that the prolamin-derived peptides QSPVF and QPY (−6.38 & −5.61 kcal/mol, respectively) have expected affinity and pharmacokinetic properties to act as potential PPARγ antagonists. Hence, according to our results, bioactive peptides resulting from NPC rice consumption might have an antiadipogenic effect via PPARγ interactions, but further experimentation and validation in suitable biological model systems are necessary to gain more insight and to provide evidence to support our in silico findings.

Current trends and perspectives on bioaccessibility and bioavailability of food bioactive peptides: in vitro and ex vivo studies

The bioaccessibility and bioavailability of food-derived bioactive compounds are important issues when assessing their in vivo physiological health-promoting effects. Food components such as proteins and peptides are exposed to different proteases and peptidases during gastrointestinal digestion and absorption. Different in vitro approaches have therefore been developed to evaluate the bioaccessibility and stability of bioactive peptides. The static simulated gastrointestinal digestion model (SGD) was widely reported to assess the bioaccessibility of bioactive peptides. On the other hand, although the dynamic SGD model may better simulate human digestion, it has rarely been explored in bioaccessibility studies of food bioactive peptides due to its high cost and lack of standardization. For bioavailability studies, the Caco-2 cell monolayer model has been used extensively for the assessment of food bioactive peptides. In fact, very few reports using alternative methods for determining transepithelial transport of bioactive peptides have been employed. In this sense, ex vivo tissue-based models such as the Ussing chamber and the everted sac gut have been used. Current evidence supports the fact that using SGD with cell-based models for evaluating the bioaccessibility, absorption, and bioavailability of food-derived bioactive peptides, is the most commonly used approach. Nevertheless, SGD with ex vivo tissue-based models such as the everted sac, remains to be further explored because it seems to be the model that better mimics the physiological process - it is also fast and inexpensive, and several compounds may be tested simultaneously. In the present review, we discuss information available on the different in vitro approaches for the determination of bioaccessibility and bioavailability of food-derived bioactive peptides with special emphasis on ex vivo tissue-based models such as the everted sac and the Ussing chamber models. © 2022 Society of Chemical Industry.

Food Protein-Derived Antioxidant Peptides: Molecular Mechanism, Stability and Bioavailability

The antioxidant activity of protein-derived peptides was one of the first to be revealed among the more than 50 known peptide bioactivities to date. The exploitation value associated with food-derived antioxidant peptides is mainly attributed to their natural properties and effectiveness as food preservatives and in disease prevention, management, and treatment. An increasing number of antioxidant active peptides have been identified from a variety of renewable sources, including terrestrial and aquatic organisms and their processing by-products. This has important implications for alleviating population pressure, avoiding environmental problems, and promoting a sustainable shift in consumption. To identify such opportunities, we conducted a systematic literature review of recent research advances in food-derived antioxidant peptides, with particular reference to their biological effects, mechanisms, digestive stability, and bioaccessibility. In this review, 515 potentially relevant papers were identified from a preliminary search of the academic databases PubMed, Google Scholar, and Scopus. After removing non-thematic articles, articles without full text, and other quality-related factors, 52 review articles and 122 full research papers remained for analysis and reference. The findings highlighted chemical and biological evidence for a wide range of edible species as a source of precursor proteins for antioxidant-active peptides. Food-derived antioxidant peptides reduce the production of reactive oxygen species, besides activating endogenous antioxidant defense systems in cellular and animal models. The intestinal absorption and metabolism of such peptides were elucidated by using cellular models. Protein hydrolysates (peptides) are promising ingredients with enhanced nutritional, functional, and organoleptic properties of foods, not only as a natural alternative to synthetic antioxidants.

Assessment of Novel Oligopeptides from Rapeseed Napin (Brassica napus) in Protecting HepG2 Cells from Insulin Resistance and Oxidative Stress

Oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Pro-Leu-Lys (HPLK), Leu-Pro-Lys (LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)) are newly identified from rapeseed napin (Brassica napus) protein-derived hydrolysates with the capability of upregulating glucose transporter-4 (GLUT4) expression and translocation. However, whether each of them enhances GLUT4 expression and translocation and their specific mechanisms remain unclear. Here, we assess the effects of the oligopeptides against insulin resistance (IR) and oxidative stress in hepatocytes and screen out the most antidiabetic one. Specifically, compared with other oligopeptides, LPK not only remarkably elevated glucose consumption to 8.45 mmol/L protein; superoxide dismutase (SOD) activity to 319 U/mg protein; GLUT4 expression and translocation; and phosphorylated level of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) (P < 0.05) but also remarkably attenuated the reactive oxygen species (ROS) level to 2255, lactate dehydrogenase (LDH) activity to 20.5 U/mg protein, malondialdehyde (MDA) content to 241 nmol/mg protein, and NO content to 1302 μmol/mL protein (P < 0.05). These findings demonstrated that antidiabetic oligopeptide LPK possessed the most potential to protect HepG2 cells from IR and oxidative stress via activating IRS-1/PI3K/Akt/GLUT4 and regulating common oxidative markers in vitro.

Transepithelial transport and cellular mechanisms of food-derived antioxidant peptides

Considering the involvement of oxidative stress in the etiology of many non-communicable diseases, food-derived antioxidant peptides (FDAPs) are strong candidates for nutraceutical development for disease prevention and management. This paper reviews current evidence on the transepithelial transport and cellular mechanisms of antioxidant activities of FDAPs. Several FDAPs have multiple health benefits such as anti-inflammatory and anti-photoaging activities, in addition to antioxidant properties through which they protect cellular components from oxidative damage. Some FDAPs have been shown to permeate the intestinal epithelium, which could facilitate their bioavailability and physiological bioactivities. Molecular mechanisms of FDAPs include suppression of oxidative stress as evidenced by reduction in intracellular reactive oxygen species production, lipid peroxidation and apoptotic protein activation as well as increase in antioxidant defense mechanisms (enzymatic and non-enzymatic). Since many FDAPs have demonstrated promising antioxidant activity, future investigation should focus on further elucidation of molecular mechanisms and human studies to explore their practical application for the prevention and management of oxidative stress-related diseases.

Peptide profile of Parmigiano Reggiano cheese after simulated gastrointestinal digestion: From quality drivers to functional compounds

Time of ripening has a strong impact on shaping the valuable and recognizable characteristics of long-ripened types of cheese such as Parmigiano Reggiano (PR) due to the interrelationship between microbiota and proteolysis that occurs during ripening. The derived peptide profile is linked to cheese quality and represents the canvas for enzymes upon digestion, which could be responsible for the release of potentially bioactive peptides (BPs). In this study, we aimed at investigating the presence of BP in 72 PR cheese samples of different ripening times, from curd to 24 months of ripening, produced in six different dairies, and following their fate after simulated gastrointestinal digestion. A small number of peptide sequences sharing 100% similarity with known antimicrobial, antioxidant, and ACE-inhibitor sequences were found in PR cheeses, while a higher number of potential BPs were found after their simulated gastrointestinal digestion, in different amounts according to ripening time. Taking advantage of the complex organization of the sampling plan, we were able to follow the fate of peptides considered quality drivers during cheese ripening to their release as functional compounds upon digestion.

Transport of Biologically Active Ultrashort Peptides Using POT and LAT Carriers

Ultrashort peptides (USPs), consisting of 2–7 amino-acid residues, are a group of signaling molecules that regulate gene expression and protein synthesis under normal conditions in various diseases and ageing. USPs serve as a basis for the development of drugs with a targeted mechanism of action. The purpose of this review is to systematize the available data on USP transport involving POT and LAT transporters in various organs and tissues under normal, pathological and ageing conditions. The carriers of the POT family (PEPT1, PEPT2, PHT1, PHT2) transport predominantly di- and tripeptides into the cell. Methods of molecular modeling and physicochemistry have demonstrated the ability of LAT1 to transfer not only amino acids but also some di- and tripeptides into the cell and out of it. LAT1 and 2 are involved in the regulation of the antioxidant, endocrine, immune and nervous systems’ functions. Analysis of the above data allows us to conclude that, depending on their structure, di- and tripeptides can be transported into the cells of various tissues by POT and LAT transporters. This mechanism is likely to underlie the tissue specificity of peptides, their geroprotective action and effectiveness in the case of neuroimmunoendocrine system disorders.

Novel peptides from sea cucumber intestinal hydrolysates promote longitudinal bone growth in adolescent mice through accelerating cell cycle progress by regulating glutamine metabolism

Sea cucumber intestines are recognized as a major by-product in the sea cucumber processing industry and have been shown to exhibit bioactive properties. However, whether the sea cucumber intestine is beneficial for osteogenesis remains unknown. In this study, low molecular weight peptides rich in glutamate/glutamine were obtained from sea cucumber intestines (SCIP) by enzymatic hydrolysis, and orally administered to adolescent mice to investigate the effects on longitudinal bone growth. The results showed that the SCIP supplement significantly increased the femur length and new bone formation rate by 9.6% and 56.3%, and elevated the levels of serum osteogenic markers alkaline phosphatase (ALP), Collagen I and osteocalcin (OCN). Notably, H&E staining showed that SCIP significantly increased the height of the growth plate, in which the height of the proliferation zone was elevated by 95.6%. Glutamine is a major determinant of bone growth. SCIP supplement significantly increased glutamine levels in the growth plate by 44.2% and upregulated the expression of glutamine metabolism-related enzymes glutaminase 1 (Gls1) and glutamate dehydrogenase 1 (GLUD1) in the growth plate. Furthermore, SCIP supplement upregulated growth plate acetyl coenzyme A levels to promote histone acetylation and accelerated cell cycle progression by upregulating Sox9 expression, thereby contributing to rapid chondrocyte proliferation. To the best of our knowledge, this is the first report where SCIP could enhance longitudinal bone growth via promoting growth plate chondrocyte proliferation. The present study will provide new ideas and a theoretical basis for the high-value utilization of sea cucumber intestines.

Transport, Stability, and In Vivo Hypoglycemic Effect of a Broccoli-Derived DPP-IV Inhibitory Peptide VPLVM

Diabetes is a major metabolic disease that requires long-term pharmacotherapy. Bioactive peptides have unique advantages such as higher potency, selectivity, and safety over small molecules and have achieved great success in the treatment of diabetes. We previously isolated a dipeptidyl peptidase-IV (DPP-IV) inhibitory peptide VPLVM with IC₅₀ = 99.68 μM from the protein hydrolysates of broccoli stems and leaves. Here, we evaluated the interaction with DPP-IV, transport, stability, and in vivo hypoglycemic effects of VPLVM. VPLVM interacted closely and steadily with DPP-IV at S1 and S2 pockets. VPLVM had a good gastrointestinal enzyme resistance and was transported through the Caco-2 cell monolayer via paracellular diffusion and by the PepT1 with a P_app of 6.96 × 10^-7 cm/s. VPLVM has a t_1/2 of 12.56 ± 0.41 min in vitro plasma stability. In the oral glucose tolerance test, VPLVM showed an excellent hypoglycemic effect at 30 min after administration. VPLVM has potential as a candidate for the treatment of hyperglycemia.

Peptidomic analysis of digested products of surimi gels with different degrees of cross-linking: In vitro gastrointestinal digestion and absorption

To investigate the cross-linking degree on the in vitro gastrointestinal digestion and absorption properties of surimi gel, three types of surimi gels with low, moderate, and high cross-linking degrees were prepared, and then in vitro digestion models (static and dynamic) and a Caco-2 cell monolayer model combined with LC-MS/MS were used to do peptidomic analysis of digestive and absorbed juices. The results showed that an increase in cross-linking degree promoted the release of peptides after gastrointestinal digestion. These peptides originated from the myosin head and rod, the rod was the main digestion region. More potential bioactive peptides from intestinal digestive juice could be transported through the intestinal epithelium. Compared with static digestion, dynamic digestion digested surimi gels more thoroughly, especially during gastric digestion. This study provides a theoretical basis and guidance for the production of surimi products with higher nutritional value and the in vitro digestion methods of gelatinous foods.

Current findings support the potential use of bioactive peptides in enhancing zinc absorption in humans

More than two billion people around the world are affected by zinc deficiency, mainly due to the inadequate intake and absorption of zinc. Based on recent research findings, the bioactive peptides could potentially be used to combat zinc deficiency particularly due to their Zinc chelating ability. The main aim of this review was to present current findings, supporting the potential use of bioactive peptides based on their ability to enhance zinc absorption. In-vivo, in-vitro, and ex-vivo studies have demonstrated that zinc chelating peptides can enhance the retention, transportation, and absorption of zinc. Comparative studies on zinc bioavailability from protein hydrolysates and zinc salts have demonstrated that the protein hydrolysates-zinc complexes are more bioavailable than the zinc salts. Data from the structure-function relationship of zinc chelating peptides suggest that the zinc chelating capacities of peptides increase in the following order; the position of zinc chelator > zinc chelator strength > abundance of zinc chelators > net charge > molecular weight. In addition, the transport mechanism of peptide-zinc complex is hypothesized, and the potential use of bioactive peptides based on their safety and taste and limitations to their commercialization are also discussed.

Angiotensin I-converting enzyme inhibitory peptide: an emerging candidate for vascular dysfunction therapy

Abnormal vasoconstriction, inflammation, and vascular remodeling can be promoted by angiotensin II (Ang II) in the renin-angiotensin system (RAS), leading to vascular dysfunction diseases such as hypertension and atherosclerosis. Researchers have recently focused on angiotensin I-converting enzyme inhibitory peptides (ACEIPs), that have desirable efficacy in vascular dysfunction therapy due to Ang II reduction by inhibiting ACE activity. Promising methods for the large-scale preparation of ACEIPs include selective enzymatic hydrolysis and microbial fermentation. Thus far, ACEIPs have been widely reported to be hydrolyzed from protein-rich sources, including animals, plants, and marine organisms, while many emerging microorganism-derived ACEIPs are theoretically biosynthesized through the nonribosomal peptide synthase (NRPS) pathway. Notably, vasodilatation, anti-inflammation, and vascular reconstruction reversal of ACEIPs are strongly correlated. However, the related molecular mechanisms underlying signal transduction regulation in vivo remain unclear. We provide a comprehensive update of the ACE-Ang II-G protein-coupled type 1 angiotensin receptor (AT1R) axis signaling and its functional significance for potential translation into therapeutic strategies, particularly targeting AT1R by ACEIPs, as well as specific related signaling pathways. Future studies are expected to verify the biosynthetic regulatory mechanism of ACEIPs via the NRPS pathway, the effect of gut microbiota metabolism on vascular dysfunction and rigorous studies of ACE-Ang II-AT1R signaling pathways mediated by ACEIPs in large animals and humans.

Advancement and prospects of production, transport, functional activity and structure-activity relationship of food-derived angiotensin converting enzyme (ACE) inhibitory peptides

Food-derived antihypertensive peptides have attracted increasing attention in functional foods for health promotion, due to their high biological activity, low toxicity and easy metabolism in the human body. Angiotensin converting enzyme (ACE) is a key enzyme that causes the increase in blood pressure in mammals. However, few reviews have summarized the current understanding of ACE inhibitory peptides and their knowledge gaps. This paper focuses on the food origins and production methods of ACE inhibitory peptides. Compared with conventional methods, the advanced technologies and emerging bioinformatics approaches have recently been applied for efficient and targeted release of ACE inhibitory peptides from food proteins. Furthermore, the transport and underlying mechanisms of ACE inhibitory peptides are emphatically described. Molecular modeling and the Michaelis-Menten equation can provide information on how ACE inhibitors function. Finally, we discuss the structure-activity relationships and other bio-functional properties of ACE inhibitory peptides. Molecular weight, hydrophobic amino acid residues, charge, amino acid composition and sequence (especially at the C-terminal and N-terminal) have a significant influence on ACE inhibitory activity. Some studies are required to increase productivity, improve bioavailability of peptides, evaluate their bio-accessibility and efficiency on reducing blood pressure to provide a reference for the development and application of health products and auxiliary treatment drugs.

Protein Concentrates on Tepary Bean (Phaseolus acutifolius Gray) as a Functional Ingredient: In silico Docking of Tepary Bean Lectin to Peroxisome Proliferator-Activated Receptor Gamma

The tepary bean (Phaseolus acutifolius Gray) is a US-Mexico frontier native crop, produces high yields in agriculture, and needs to be reconsidered because of its nutritional and functional properties. This study aimed to determine the technological and nutritional properties of flours and protein concentrates of tepary bean, besides determining an in silico agonist effect of tepary bean lectin to peroxisome proliferator-activated receptor gamma (PPAR-γ). We evaluated the technological properties of raw samples (tepary flour and tepary protein concentrate) and cooked samples (tepary flour and tepary protein concentrate). The flours present a significant difference (p < 0.05) concerning protein concentrates in water absorption and oil absorption capacity. The raw samples' emulsifying capacity was higher than that reported in the literature for other legumes, but not the cooked samples. The samples' foaming capacity had no significant difference in treatments (p > 0.05), and cooked tepary bean protein concentrate presented complete gelation at a lower concentration (2%). Nutritionally, raw samples present a protein percentage of 23.46 ± 0.06 and 71.38 ± 0.44 and cooked samples present a protein percentage of 25.27 ± 0.04 and 62.69 ± 0.14; a chemical score of 72, 86, 82, and 72; in vitro protein digestibility (%) = 48.20 ± 0.31, 49.80 ± 0.80, 61.77 ± 1.70, and 63.61 ± 4.19; and C-PER = 0.86, 1.34, 1.93, and 1.81, respectively. All the samples showed methionine + cysteine as the limiting amino acid. All these nutritional data are very similar to the common bean (Phaseolus vulgaris). SDS-PAGE preserves the lectin fraction in both protein concentrates. The in silico study of tepary lectin (PDB: 6tt9) shows that there were seven peptides that presented values below -120 kcal/mol: PEW, VSVGF, PSQK, TTPW, ATSF, ITY, and TSF, with VSVGF, PSQK, and PEW having the highest affinity for active sites of the PAPRγ receptor (binding energies from -5.32 to -7.04 kcal/mol). These peptides could show antiadipogenic or antidiabetic activity based on the intermolecular bond energies and open an interesting research item.

Transport of Dietary Anti-Inflammatory Peptide, γ-Glutamyl Valine (γ-EV), across the Intestinal Caco-2 Monolayer

The present study analyzed the transepithelial transport of the dietary anti-inflammatory peptide, γ-glutamyl valine (γ-EV). γ-EV is naturally found in dry edible beans. Our previous study demonstrated the anti-inflammatory potency of γ-EV against vascular inflammation at a concentration of 1mM, and that it can transport with the apparent permeability coefficient (P_app) of 1.56 × 10^-6 ± 0.7 × 10^-6 cm/s across the intestinal Caco-2 cells. The purpose of the current study was to explore whether the permeability of the peptide could be enhanced and to elucidate the mechanism of transport of γ-EV across Caco-2 cells. The initial results indicated that γ-EV was nontoxic to the Caco-2 cells up to 5 mM concentration and could be transported across the intestinal cells intact. During apical-to-basolateral transport, a higher peptide dose (5 mM) significantly (p < 0.01) enhanced the transport rate to 2.5 × 10^-6 ± 0.6 × 10^-6 cm/s. Cytochalasin-D disintegrated the tight-junction proteins of the Caco-2 monolayer and increased the P_app of γ-EV to 4.36 × 10^-6 ± 0.16 × 10^-6 cm/s (p < 0.001), while theaflavin 3'-gallate and Gly-Sar significantly decreased the P_app (p < 0.05), with wortmannin having no effects on the peptide transport, indicating that the transport route of γ-EV could be via both PepT1-mediated and paracellular.

Characterization of DPP-IV Inhibitory Peptides Using an In Vitro Cell Culture Model of the Intestine

Here, we characterize the activities of two depeptidyl peptidase-IV (DPP-IV) inhibitory peptides, VLATSGPG and LDKVFER, using the Caco-2 monolayer model for the intestine. VLATSGPG and LDKVFR inhibited the DPP-IV in the cells via a mixed-type inhibition mode, with in situ IC₅₀ values of 207.3 and 148.5 μM, respectively. Furthermore, VLATSGPG and LDKVFR were transported intact across the cells, with P_app values of 2.41 ± 0.16 and 4.23 ± 0.29 × 10^-7 cm/s, respectively. Fragmented peptides were identified in the basolateral side of the membrane. Two of these, GPG and VLA, exhibited high inhibitory activities of 83.6 ± 3.3 and 58.5 ± 2.5%, respectively, at 100 μM concentration. Although 3 mM VLATSGPG and LDKVFR were transported across the epithelium in a concentration-dependent manner, their transport did not damage the tight junction proteins, ZO-1 and occludin. This study demonstrates that the two peptides potentially regulate DPP-IV activity in the intestine.

Activity and bioavailability of food protein-derived angiotensin-I-converting enzyme-inhibitory peptides

Angiotensin-I-converting enzyme (ACE) inhibitory peptides are able to inhibit the activity of ACE, which is the key enzymatic factor mediating systemic hypertension. ACE-inhibitory peptides can be obtained from edible proteins and have the function of antihypertension. The amino acid sequences and the secondary structures of ACE-inhibitory peptides determine the inhibitory activities and stability. The resistance of ACE-inhibitory peptides to digestive enzymes and peptidase affect their antihypertensive bioactivity in vivo. In this paper, the mechanism of ACE-inhibition, sources of the inhibitory peptides, structure-activity relationships, stability during digestion, absorption and transportation of ACE-inhibitory peptides, and consumption of ACE-inhibitory peptides are reviewed, which provide guidance to the development of new functional foods and production of antihypertensive nutraceuticals and pharmaceuticals.

miR300 intervenes Smad3/β-catenin/RunX2 crosstalk for therapy with an alternate function as indicative biomarker in osteoporosis

The study reports a theranostic nature of rno-miR-300 (miR300) in the osteoblast functioning, by influencing the signaling pathway(s), associated with osteoblast differentiation. Excessive expression of miR300 suppresses osteoblast functions. Smad3 served as a validated target for miR300, on homology-based computational analysis and experimental testimony, which activates β-catenin, and subsequently potentiates Runx2. The impact of miR300 on the Smad3/β-catenin/Runx2 signaling interactions in the induction of osteoblast differentiation was scrutinized by immunoblotting and in vivo miRNA antagonism. Overexpression of miR300 in the rat calvarial osteoblasts decreases the protein levels of Smad3, β-catenin and Runx2. Besides, in vivo silencing of miR300 in the neonatal pups and adult rats by AntimiR300 abolishes the suppressing action of miR300 on the osteoblast differentiation and expressions of Smad3/β-catenin/Runx2 axis. MicroCT studies showed improved trabecular microarchitecture in the AntimiR300 transfected ovariectomised rat model compared to sham and negative control. Furthermore, expression levels of miR300 were evaluated in serum samples from an independent set of 30 osteoporotic patients followed by a Receiver Operating Characteristic Curve (ROC) based analysis for the diagnostic efficiency of miR300. Interestingly, the results exhibited high levels of miR300 (p < 0.0001) in the serum samples from osteoporotic patients relative to non-osteoporotic subjects (AUC = 0.9689). Thus, miR300 negatively regulates the differentiation of osteoblasts by targeting crosstalk among Smad3, β-catenin and Runx2, unveiling an enormous ability to serve as a therapeutic target for bone-related disorder management strategies. Besides, miR300 may potentially function for the diagnosis of osteoporosis as a non-invasive biomarker.

The Influence of Peptidases in Intestinal Brush Border Membranes on the Absorption of Oligopeptides from Whey Protein Hydrolysate: An Ex Vivo Study Using an Ussing Chamber

For many years, it was believed that only amino acids, dipeptides, and tripeptides could be absorbed and thus reach the bloodstream. Nowadays, the bioavailability of oligopeptides is also considered possible, leading to new research. This pilot study investigates the activity of brush border enzymes on undigested whey protein hydrolysate (WPH) and on simulated intestinal digested (ID) whey hydrolysate and the subsequent absorption of resultant peptides through the proximal jejunum of a 7-week old piglet setup in an Ussing chamber model. Amongst all samples taken, 884 oligopeptides were identified. The brush border peptidase activity was intense in the first 10 min of the experiment, producing several new peptides in the apical compartment. With respect to the ID substrate, 286 peptides were detected in the basolateral compartment after 120 min of enzyme activity, originating from β-lactoglobulin (60%) and β-casein (20%). Nevertheless, only 0.6 to 3.35% of any specific peptide could pass through the epithelial barrier and thus reach the basolateral compartment. This study demonstrates transepithelial jejunum absorption of whey oligopeptides in an ex vivo model. It also confirmed the proteolytic activity of brush border enzymes on these oligopeptides, giving birth to a myriad of new bioactive peptides available for absorption.

Current Evidence on the Bioavailability of Food Bioactive Peptides

Food protein-derived bioactive peptides are recognized as valuable ingredients of functional foods and/or nutraceuticals to promote health and reduce the risk of chronic diseases. However, although peptides have been demonstrated to exert multiple benefits by biochemical assays, cell culture, and animal models, the ability to translate the new findings into practical or commercial uses remains delayed. This fact is mainly due to the lack of correlation of in vitro findings with in vivo functions of peptides because of their low bioavailability. Once ingested, peptides need to resist the action of digestive enzymes during their transit through the gastrointestinal tract and cross the intestinal epithelial barrier to reach the target organs in an intact and active form to exert their health-promoting properties. Thus, for a better understanding of the in vivo physiological effects of food bioactive peptides, extensive research studies on their gastrointestinal stability and transport are needed. This review summarizes the most current evidence on those factors affecting the digestive and absorptive processes of food bioactive peptides, the recently designed models mimicking the gastrointestinal environment, as well as the novel strategies developed and currently applied to enhance the absorption and bioavailability of peptides.

The Coconut Water Antimicrobial Peptide CnAMP1 Is Taken up into Intestinal Cells but Does Not Alter P-Glycoprotein Expression and Activity

Coconut antimicrobial peptide-1 (CnAMP1) is a naturally occurring bioactive peptide from green coconut water (Cocos nucifera L.). Although biological activities have been reported, the physiological relevance of these reports remains elusive as it is unknown if CnAMP1 is taken up into intestinal cells. To address this open question, we investigated the cytotoxicity of CnAMP1 in intestinal cells and its cellular uptake into human intestinal cells. Considering the importance of the P-glycoprotein (P-gp) to the intestinal metabolism of xenobiotics, we also investigated the influence of CnAMP1 on P-gp activity and expression. Both cell lines showed intracellular fluorescence after incubation with fluorescein labelled CnAMP1, indicating cellular uptake of the intact or fragmented peptide. CnAMP1 (12.5-400 μmol/L) showed no signs of cytotoxicity in LS180 and differentiated Caco-2 cells and did not affect P-gp expression and activity. Further research is required to investigate the identity of CnAMP1 hydrolysis fragments and their potential biological activities.

Repertoire of Structure-Activity-Based Novel Modified Peptides Elicits Enhanced Osteogenic Potential

Biologically active peptides in milk proteins can be used as effective dietary supplements for management of bone-associated issues including osteoporosis. A bioactive peptide derived from milk, viz. VLPVPQK/PepC, has been validated previously from our lab for its osteoanabolic action. In this study, we report 14 novel variants of PepC, designed in silico, based on the structure-activity relationship, aiming to enhance its osteogenic effect that holds tremendous therapeutic utility for bone-related injuries. PepC was computationally modified at seven positions of its original sequence, resulting in 14 modified synthetic peptides for functional predictions and in vitro assessment by comparative analysis of modified peptides by PepC for improved ability in osteogenic functional assays (proliferation potential, antioxidant ability, gene and protein expression, cytotoxic effect, bone mineralization) using calvarial osteoblasts. For most peptides with the highest Peptide7 response relative to PepC (p < 0.05), enhanced osteoanabolic response was observed. Further observations on Peptide7 have therefore been investigated in depth (qPCR, immunoblotting, LCMS/MS, and PCA analysis). Peptide7 displayed a rise in the expression of osteogenes (Osterix, Opg, Bmp2, and Runx2, p < 0.05) and protein (Runx2 and Bmp2, p < 0.05). Besides, LCMS/MS findings suggest Peptide7 escapes intestinal peptidases degradation. Experimental evidence supports an improved osteological reaction to newly modified peptides and hence exploitation in the preparation of functional foods or supplements.

Occurrence, biological properties and potential effects on human health of β-casomorphin 7: Current knowledge and concerns

The genetic variant A1 of bovine β-casein (β-Cn) presents a His residue at a position 67 of the mature protein. This feature makes the Ile⁶⁶-His⁶⁷ bond more vulnerable to enzymatic cleavage, determining the release of the peptide β-Cn f(60-66), named β-casomorphin 7 (BCM7). BCM7 is an opioid-agonist for μ receptors, and it has been hypothesized to be involved in the development of different non-transmissible diseases in humans. In the last decade, studies have provided additional results on the potential health impact of β-Cn A1 and BCM7. These studies, here reviewed, highlighted a relation between the consumption of β-Cn A1 (and its derivative BCM7) and the increase of inflammatory response as well as discomfort at the gastrointestinal level. Conversely, the role of BCM7 and the effects of ingestion of β-Cn A1 on the onset or worsening of other non-transmissible diseases as caused or favored by still need proof of evidence. Overall, the reviewed literature demonstrates that the "β-Cn A1/BCM7 issue" remains an intriguing but not exhaustively explained topic in human nutrition. On this basis, policies in favor of breeding for β-Cn variants not releasing BCM7 and consumption of "A1-like" milk appear not yet sound for a healthier and safer nutrition.

In silico evaluation of marine fish proteins as nutritional supplements for COVID-19 patients

To date, no specific drug has been discovered for the treatment of COVID-19 and hence, patients are in a state of anxiety.

Antihypertensive and antioxidant activities of enzymatic wheat bran protein hydrolysates

Bioactive peptides from plant protein sources have been continuously identified as nutrient supplements for low toxicity but multiple physiological activities such as antihypertensive, antioxidant, and anti-inflammatory. In this study, wheat bran protein isolate was digested with alcalase to produce wheat bran protein hydrolysate (WPH) that was then separated into different peptide fractions (<1, 1-3, 3-5, and 5-10 kDa) by membrane ultrafiltration. WPH and the peptide fractions were evaluated for in vitro activities such as antioxidant, renin inhibition, and angiotensin-converting enzyme (ACE) inhibition. In addition, the blood pressure-lowering effects of WPH and the <1 kDa peptides were determined by oral administration to spontaneously hypertensive rats (SHRs). Results showed that the ACE and renin inhibitions were significantly (p < .05) higher for the <1 kDa fraction (84.25% ± 2.45%, 75.19% ± 1.75%, respectively) when compared to the WPH and >1 kDa fractions. The <1 kDa fraction also showed significantly (p < .05) higher oxygen radical antioxidant activity with 2044.73 ± 37.45 (μM TE/g protein) when compared to lower values obtained for the >1 kDa membrane fractions and WPH. Oral administration (100 mg/kg body weight) of the <1 kDa membrane fraction to SHRs resulted in a better decrease (-35 mmHg) in the systolic blood pressure when compared to the WPH (-20 mmHg) after 6 hr. And seven peptides (NL, QL, FL, HAL, AAVL, AKTVF, and TPLTR) were identified and amino acid sequence was determined by tandem mass spectrometry. We conclude that the WPH could be considered as a suitable natural antihypertensive and antioxidant resource. PRACTICAL APPLICATIONS: The results of the present study indicate that WPH and its ultrafiltration fractions possess potential as a source of antihypertensive and strong antioxidant peptides. It has been proved that wheat bran has a good blood pressure lowering and antioxidation and other biological activities, and the <1 kDa fraction showing high oxygen radical absorbance capacity level also has better in vitro ACE inhibition and renin-inhibitory activity. The higher antihypertensive efficiency of the <1 kDa fraction may be because the peptides can be better absorbed from the gastrointestinal tract or an increased ability to interact with the enzyme (ACE or renin) protein structure to change the active conformation and lead to decreased catalysis. The results of this study indicate that WPH, especially <1 kDa peptide, can be used as a component in formulating antihypertensive functional foods and nutraceuticals, thus improving the industrial production efficiency and bioavailability of wheat bran.