Intestinal absorption of small peptides: a review

Exploring the mechanisms of cow placental peptides in delaying liver aging based on mitochondrial energy metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Placenta is a kind of traditional Chinese medicine, known as "Ziheche". The role of cow placental peptides (CPP) in delaying liver aging has been reported, and in-depth exploration of the specific regulatory mechanisms is of great significance for the recycling and utilization of CPP and the development of natural anti-aging drugs.

AIM OF THE STUDY

To investigate the protective effects and mechanisms of CPP on liver aging induced by D-galactose (D-gal) in mice from the perspective of mitochondrial energy metabolism.

METHODS

An aging model was induced in mice using D-gal. The body weight and liver index of mice were measured, followed by staining and electron microscopy to observe liver morphology and aging markers. Reactive oxygen species (ROS) levels and antioxidant-related indicators were assessed, and mitochondrial function was evaluated. Finally, changes and mechanisms in liver transcriptomics and targeted mitochondrial energy metabolomics were analyzed and integrated to elucidate the regulatory pathways through which CPP delays liver aging.

RESULTS

CPP improved liver structural damage, oxidative stress, and mitochondrial dysfunction induced by D-galactose in aging mice. It increased the final body weight and liver index, alleviated hepatocyte swelling and degeneration, enhanced liver antioxidant capacity, and restored normal mitochondrial morphology and function. The combined analysis of targeted mitochondrial energy metabolomics and liver transcriptomics revealed that CPP directly or indirectly regulated mitochondrial energy metabolism and delayed aging by influencing the cAMP signaling pathway, PI3K-Akt signaling pathway, oxidative phosphorylation, and other pathways, thereby modulating related genes and metabolites.

Enzymatic synthesis of antioxidant peptides with controllable and adjustable molecular weights using magnetically recyclable immobilized Alcalase

Enzymatic hydrolysis of proteins to obtain bioactive peptides is increasingly attractive, but the poor stability and low reusability of enzymes remain unsolved. Here, the magnetically recyclable immobilized Alcalase (Alcalase@SGO-PEGA) was constructed by immobilizing the free protease of Alcalase to the superparamagnetic graphene oxide (SGO) whose surface was modified with polyethylene glycol diamine (PEGA). The results indicate that Alcalase@SGO-PEGA significantly improved the thermostability and pH tolerance of Alcalase, withstanding temperatures up to 70 °C and pH levels up to 12. Additionally, Alcalase@SGO-PEGA with a saturation magnetizations (Ms) of 20.64 emu/g allowed for efficient recovery using external magnetic fields, and its catalytic stability was demonstrated by retaining 50 % of its initial activity after seven cycles of reuse. Using Alcalase@SGO-PEGA for the enzymatic hydrolysis of soy protein isolate, casein, bovine, serum protein, β-lactoglobulin, sesame protein and flaxseed, bioactive peptides with different molecular weights were obtained by adjusting the hydrolysis temperature and time. Additionally, the antioxidative capacity of the bioactive peptides was confirmed by their ABTS+ free radicals scavenging rate and Fe2+ chelating activity. This paper presents a novel, sustainable strategy for obtaining antioxidant peptides with adjustable molecular weights using magnetically recyclable immobilized Alcalase, advancing its application and promoting cleaner protein processing.

Bioconversion of agriculture by-products with functionally enhanced Streptomyces sp. SCUT-3: Fish skin as a model

With the global population continuously rising, efficient bioconversion of inedible agricultural by-products is crucial for human food and energy sustainability. We here propose solid-state fermentation approaches to efficiently convert biopolymers into oligomers/monomers by accelerating the natural degradation process of the versatile Streptomyces sp. strain SCUT-3. Using fish skin as a representative by-product, 54.3 g amino acids and 14.7 g peptides (91 % < 2500 Da) were recovered from 89.0 g protein in 100 g tilapia skin sample by collagenase-overexpressed SCUT-3 for seven days at a 1:4 substrate:liquid ratio. Fish skin collagen hydrolysates exhibited excellent anti-oxidation, anti-hypertension, scratch-repairing, anti-aging, anti-ultraviolet radiation, and anti-inflammation effects on human skin fibroblasts In vitro and zebrafish larvae in vivo, indicating their potential applications in healthcare/skincare and anti-atopic dermatitis. As Laozi said, the divine law follows nature. This study underscores the efficacy of genetically engineered SCUT-3 according to its natural biomass utilization laws in large-scale biopolymer conversion.

Metabolomics Analysis Reveals Bitter Taste Formation in off-Season Crab Hepatopancreas Marketed in June of the Lunar Calendar

Crabs marketed off-season in lunar June often have a brown hepatopancreas (BH) that tastes bitter, unlike the nonbitter orange hepatopancreas (OH). We conducted nontargeted and widely targeted metabolomics analyses on both raw and cooked orange and brown hepatopancreas of Eriocheir sinensis. A total of 115 bitter metabolites were identified, including oxylipins, amino acids, small peptides, nucleotides, vitamins, and coenzymes. Targeted quantitative analysis revealed that seven oxylipins were major contributors to the bitterness of BH. The primary metabolic pathways affecting hepatopancreas bitterness involved the production of unsaturated fatty acids and α-linolenic acid metabolism. Furthermore, specific odorants were produced from OH and BH groups during heat treatment, namely ethyl caproate and methional, respectively. Moreover, differential metabolites were found to act as odor precursors, resulting in a brown and bitter hepatopancreas with poor odor quality. This study elucidates the generation of bitter substances in the hepatopancreas of Eriocheir sinensis through metabolic pathways and thermal reaction pathways.

Absorption of food-derived peptides: Mechanisms, influencing factors, and enhancement strategies

Food-derived peptides (FPs) are bioactive molecules produced from dietary proteins through enzymatic hydrolysis or fermentation. These peptides exhibit various biological activities. However, their efficacy largely depends on bioavailability, the ability to cross absorption barriers, and reach target sites within the body. This review addresses key issues in FP absorption, including barriers, pathways, influencing factors, and strategies to enhance absorption. The biochemical and physical barriers to FP absorption include pH variations, enzymes, unstirred water layer, mucus layer, and intestinal epithelial cells. FPs enter the bloodstream via four main pathways: carrier-mediated transport, endocytosis, paracellular, and passive diffusion. The barrier-crossing efficiency depends on the structural properties and state of FPs and coexisting substances. Absorption efficiency can be significantly improved with permeability enhancers, nano-delivery systems, and chemical modifications. These insights provide a scientific basis and practical guidance for optimizing the bioactivity and health benefits of food-derived peptides.

Obstacles, research progress, and prospects of oral delivery of bioactive peptides: a comprehensive review

Bioactive peptides hold significant potential for enhancing human health, however, their limited oral bioavailability poses a substantial barrier to their widespread use in the food and pharmaceutical industries. This article reviews the key factors influencing the absorption efficiency of oral bioactive peptides, including issues related to bitter taste perception, challenges in gastrointestinal environmental stability, and limitations in transmembrane transport. Furthermore, it highlights the latest technologies, such as osmotic technology, chemical modification, and advanced delivery systems, and discusses their advantages in enhancing the stability of bioactive peptides and facilitating intestinal absorption. In addition, the application and challenges of common delivery systems such as liposomes, emulsions, polymer nanoparticles, and hydrogels in oral bioactive peptide delivery are also discussed. This paper aims to provide a theoretical foundation for scientific research and practical applications of oral delivery of bioactive peptides, thereby promoting the further development of bioactive peptides in the context of human health.

Modified throughput ninhydrin method for the qualitative assessment of dietary protein absorption in pig plasma

Protein maldigestion and malabsorption lead to malnutrition and are a feature of exocrine pancreatic insufficiency (EPI). Although it is the current standard, measurement of nitrogen in stool to assess protease activity is indirect. Up to 80% of hydrolysed proteins appear in blood in the form of peptides, so we developed a method to measure peptide-derived amino acids in plasma as a relevant measure of proteolysis, verified its accuracy, precision, and linearity, and validated it in a porcine model. We modified a ninhydrin method. Large proteins were eliminated from plasma with 10 kDa-cut-off centrifugal filters. Free and total amino acids were measured in permeate before and after its hydrolysis. Peptide-derived amino acids were quantified by subtracting free amino acids from total amino acids. We verified the method in vitro and by comparing results in healthy and EPI pigs. The accuracy of the analysis was close to 100%, with excellent precision (mean relative standard deviation for low, medium, and high amino acid levels = 0.88%) and with stringent linearity (r2  = 0.986, %RE = 5.23). The high-throughput ninhydrin method detected levels of peptide-derived amino acids in vivo with maximal changes seen approximately 2 hours postprandially in young pigs. The AUC and Cmax were significantly higher in healthy compared to EPI pigs (P = .0026 and P = .0037, respectively). The high-throughput ninhydrin method is a sensitive, reliable, and practical method for the estimation of dietary peptide-derived amino acids. This assay endpoint could serve as a direct biomarker of protein digestion and absorption.

Bioactive Peptides from Fermented Foods: Production Approaches, Sources, and Potential Health Benefits

Microbial fermentation is a well-known strategy for enhancing the nutraceutical attributes of foods. Among the fermentation outcomes, bioactive peptides (BAPs), short chains of amino acids resulting from proteolytic activity, are emerging as promising components thanks to their bioactivities. Indeed, BAPs offer numerous health benefits, including antimicrobial, antioxidant, antihypertensive, and anti-inflammatory properties. This review focuses on the production of bioactive peptides during the fermentation process, emphasizing how different microbial strains and fermentation conditions influence the quantity and quality of these peptides. Furthermore, it examines the health benefits of BAPs from fermented foods, highlighting their potential in disease prevention and overall health promotion. Additionally, this review addresses the challenges and future directions in this field. This comprehensive overview underscores the promise of fermented foods as sustainable and potent sources of bioactive peptides, with significant implications for developing functional foods and nutraceuticals.

N-Pep-Zn Improves Cognitive Functions and Acute Stress Response Affected by Chronic Social Isolation in Aged Spontaneously Hypertensive Rats (SHRs)

BACKGROUND/OBJECTIVES

Aging and chronic stress are regarded as the most important risk factors of cognitive decline. Aged spontaneously hypertensive rats (SHRs) represent a suitable model of age-related vascular brain diseases. The aim of this study was to explore the effects of chronic isolation stress in aging SHRs on their cognitive functions and response to acute stress, as well as the influence of the chronic oral intake of N-Pep-Zn, the Zn derivative of N-PEP-12.

METHODS

Nine-month-old SHRs were subjected to social isolation for 3 months (SHRiso group), and one group received N-pep-Zn orally (SHRisoP, 1.5 mg/100 g BW). SHRs housed in groups served as the control (SHRsoc). The behavioral study included the following tests: sucrose preference, open field, elevated plus maze, three-chamber sociability and social novelty and spatial learning and memory in a Barnes maze. Levels of corticosterone, glucose and proinflammatory cytokines in blood plasma as well as salivary amylase activity were measured. Restraint (60 min) was used to test acute stress response.

RESULTS

Isolation negatively affected the SHRs learning and memory in the Barnes maze, while the treatment of isolated rats with N-Pep-Zn improved their long-term memory and working memory impairments, making the SHRisoP comparable to the SHRsoc group. Acute stress induced a decrease in the relative thymus weight in the SHRiso group (but not SHRsoc), whereas treatment with N-Pep-Zn prevented thymus involution. N-pep-Zn mitigated the increment in blood cortisol and glucose levels induced by acute stress.

CONCLUSIONS

N-pep-Zn enhanced the adaptive capabilities towards chronic (isolation) and acute (immobilization) stress in aged SHRs and prevented cognitive disturbances induced by chronic isolation, probably affecting the hypothalamo-pituitary-adrenal, sympathetic, and immune systems.

Evaluating intestinal absorption of peptide Met-Lys-Pro in casein hydrolysate using Caco-2 and human iPS cell-derived small intestinal epithelial cells

High blood pressure is a major risk factor for cardiovascular disease. Our previous study confirmed that daily intake of casein hydrolysate that contained Met-Lys-Pro (MKP) can safely lower mildly elevated blood pressure. The present study aimed to evaluate the intestinal absorption differences between peptide MKP as a casein hydrolysate and synthetic MKP alone using Caco-2 cells and human iPS cell-derived small intestinal epithelial cells (hiSIECs). MKP was transported intact through Caco-2 cells and hiSIECs with permeability coefficient (Papp) values of 0.57 ± 0.14 × 10-7 and 1.03 ± 0.44 × 10-7 cm/s, respectively. This difference in Papp suggests differences in the tight junction strength and peptidase activity of each cell. Moreover, the transepithelial transport and residual ratio of intact MKP after adding casein hydrolysate containing MKP was significantly higher than that after adding synthetic MKP alone, suggesting that other peptides in casein hydrolysate suppressed MKP degradation and increased its　transport. These findings suggest that hiSIECs could be useful for predicting the human intestinal absorption of bioactive peptides; ingesting MKP as a casein hydrolysate may also improve MKP bioavailability.

Exploring the impact of encapsulation on the stability and bioactivity of peptides extracted from botanical sources: trends and opportunities

Bioactive peptides derived from plant sources have gained significant attention for their potential use in preventing and treating chronic degenerative diseases. However, the efficacy of these peptides depends on their bioaccessibility, bioavailability, and stability. Encapsulation is a promising strategy for improving the therapeutic use of these compounds. It enhances their stability, prolongs their shelf life, protects them from degradation during digestion, and enables better release control by improving their bioaccessibility and bioavailability. This review aims to analyze the impact of various factors related to peptide encapsulation on their stability and release to enhance their biological activity. To achieve this, it is necessary to determine the composition and physicochemical properties of the capsule, which are influenced by the wall materials, encapsulation technique, and operating conditions. Furthermore, for peptide encapsulation, their charge, size, and hydrophobicity must be considered. Recent research has focused on the advancement of novel encapsulation methodologies that permit the formation of uniform capsules in terms of size and shape. In addition, it explores novel wall materials, including polysaccharides derived from unconventional sources, that allow the precise regulation of the rate at which peptides are released into the intestine.

The neuroprotective effects of SFGDI on sirtuin 3-related oxidative stress by regulating the Sirt3/SOD/ROS pathway and energy metabolism in BV2 cells

Recently, the investigation of neuroprotective peptides has gained attention in addressing memory impairment and cognitive decline. Although the potential neuroprotective peptide Serine-Phenylalanine-Glycine-Aspartic acid-Isoleucine (SFGDI) has been identified from sea cucumber, the molecular mechanisms remain unclear. This study was conducted to explore the neuroprotection of SFGDI against 3-TYP-induced oxidative stress in BV2 cells. The results showed a retention rate of 76.70% during in vitro simulated gastrointestinal digestion and an absorption rate of 10.41% in a rat-everted gut sac model for SFGDI. Two hours following the administration of SFGDI via gavage in mice, a notable fluorescence was observed in the brain, indicating a potential neuroprotection of SFGDI through its interactions with nerve cells. By utilizing a model of oxidative stress injury induced by 3-TYP in BV2 cells, it was determined that pretreatment with SFGDI (50-200 μg mL-1) resulted in a dose-dependent reduction in the acetylated SOD level, leading to enhanced SOD activity and reduced levels of ROS and MDA. In addition, this pretreatment triggered an increase in unsaturated lipid levels, which helped maintain the intracellular lipid metabolism balance and preserve the mitochondrial function and glycolysis levels to regulate energy metabolism. The results of this study indicate that SFGDI demonstrates neuroprotective properties through its modulation of the Sirt3/SOD/ROS pathway, regulation of lipid metabolism, and enhancement of energy metabolism in BV2 cells. These findings suggest potential novel therapeutic approaches for addressing Sirt3-related memory deficits and neurodegenerative disorders.

Encapsulation of short-chain bioactive peptides (BAPs) for gastrointestinal delivery: a review

The majority of known peptides with high bioactivity (BAPs) such as antihypertensive, antidiabetic, antioxidant, hypocholesterolemic, anti-inflammatory and antimicrobial actions, are short-chain sequences of less than ten amino acids. These short-chain BAPs of varying natural and synthetic origin must be bioaccessible to be capable of being adsorbed systemically upon oral administration to show their full range of bioactivity. However, in general, in vitro and in vivo studies have shown that gastrointestinal digestion reduces BAPs bioactivity unless they are protected from degradation by encapsulation. This review gives a critical analysis of short-chain BAP encapsulation and performance with regard to the oral delivery route. In particular, it focuses on short-chain BAPs with antihypertensive and antidiabetic activity and encapsulation methods via nanoparticles and microparticles. Also addressed are the different wall materials used to form these particles and their associated payloads and release kinetics, along with the current challenges and a perspective of the future applications of these systems.

Screening and molecular dynamics simulation of ACE inhibitory tripeptides derived from milk fermented with Lactobacillus delbrueckii QS306

Peptides in milk fermented with Lactobacillus delbrueckii QS306 before and after ultrahigh pressure treatment were identified using proteomics. Subsequently, 16 stable tripeptides were screened out based on activity score prediction, PeptideCutter analysis, and hydrophobicity calculations. Among them, WRP, WSR, and YRP showed the best angiotensin-converting enzyme (ACE) inhibitory activity, and their semi-inhibitory concentrations were 46.707, 300.121, and 89.555 μM, respectively. WRP and WSR were competitive inhibitors, whereas YRP was non-competitive. Gastrointestinal simulation revealed that WRP and YRP had better gastrointestinal stability. The values of RMSD, ΔGbind, ΔGpol, and RSMF obtained from molecular dynamics simulation indicated that the interaction of WRP and ACE was stable. Thus, Lactobacillus delbrueckii QS306-fermented milk can serve as an important source of ACE inhibitory peptides both before and after ultrahigh pressure treatment. The strategy of in silico screening, activity evaluation, and molecular dynamics simulation adopted in this study can be applied to the large-scale screening of novel peptides with high ACE inhibitory activity.

Comparative structural, digestion and absorption characterization of three common extruded plant proteins

Extruded plant proteins, also known as textured vegetable proteins (TVPs), serve as vital components in plant-based meat analogue, yet their structural and nutritional characteristics remain elusive. In this study, we examined the impact of high-moisture (HM) and low-moisture (LM) extrusion on the structures, digestion and absorption of three types of plant proteins. Extrusion transformed plant proteins from spherical to fibrous forms, and formed larger aggregate particles. It also led to the disruption of original disulfide bonds and hydrophobic interactions within protein molecules, and the formation of new cross-links. Intriguingly, compared to native plant proteins, TVPs' α-helix/β-sheet values decreased from 0.68 to 0.69 to 0.56-0.65. Extrusion increased the proportion of peptides shorter than 1 kD in digesta of TVPs by 1.44-23.63%. In comparison to unextruded plant proteins, TVPs exhibited lower content of free amino acids in cell transport products. Our findings demonstrated that extrusion can modify protein secondary structure by diminishing the α-helix/β-sheet value, and impact protein tertiary structure by reducing disulfide bonds and hydrophobic interactions, promoting the digestion and absorption of plant proteins. These insights offer valuable scientific backing for the utilization of extruded plant-based proteins, bolstering their role in enhancing the palatability and nutritional profile of plant-based meat substitutes.

Formation of dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides from Jack Bean (Canavalia ensiformis (L.) DC.) sprout in simulated digestion

Bean sprouts are potential plant proteins that produce DPP-IV inhibitory peptides. These peptides must be stable and active in the brush border membrane of the small intestine to inhibit DPP-IV. The purpose of this research is to evaluate the DPP-IV inhibitory activity of jack bean sprouts using pepsin-pancreatin during simulated digestion, as well as the absorption of these peptides through the everted gut sac method. The results showed that after 180 min of digestion simulation, the Mw < 1 kDa peptide fraction of jack bean hydrolysate, which germinated for 60 h (HG60), had the highest inhibitory activity. The duodenum absorbs most of the peptides with inhibitory activity of 61.77%, which is slightly lower than activity after digestion (62.19%). These outcomes suggest that the DPP-IV inhibitory activity of HG60 can be maintained after digestion and absorption. Two novel peptides KAVGDPI and QGVVLRP identified after absorption contain crucial amino acids confirming as DPP-IV inhibitor.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01343-9.

Novel orally bioavailable piperidine derivatives as extracellular arginase inhibitors developed by a ring expansion

Arginase is a multifaced enzyme that plays an important role in health and disease being regarded as a therapeutic target for the treatment of various pathological states such as malignancies, asthma, and cardiovascular disease. The discovery of boronic acid-based arginase inhibitors in 1997 revolutionized attempts of medicinal chemistry focused on development of drugs targeting arginase. Unfortunately, these very polar compounds had limitations such as analysis and purification without chromophores, synthetically challenging space, and poor oral bioavailability. Herein, we present a novel class of boronic acid-based arginase inhibitors which are piperidine derivatives exhibiting a different pharmacological profile compared to our drug candidate in cancer immunotherapy -OATD-02 - dual ARG1/2 inhibitor with high intracellular activity. Compounds from this new series show low intracellular activity, hence they can inhibit mainly extracellular arginase, providing different therapeutic space compared to a dual intracellular ARG1/2 inhibitor. The disclosed series showed good inhibitory potential towards arginase enzyme in vitro (IC50 up to 160 nM), favorable pharmacokinetics in animal models, and encouraging preliminary in vitro and in vivo tolerability. Compounds from the new series have moderate-to-high oral bioavailability (up to 66 %) and moderate clearance in vivo. Herein we describe the development and optimization of the synthesis of the new class of boronic acid-based arginase inhibitors via a ring expansion approach starting from the inexpensive chirality source (d-hydroxyproline). This upgraded methodology facilitated a gram-scale delivery of the final compound and eliminated the need for costly and time-consuming chiral resolution.

Dynamic analysis of metabolomics reveals the potential associations between colonic peptides and serum appetite-related hormones

Gut signals, including hormones and metabolites are crucial zeitgebers that regulate the circadian rhythm of host metabolism, but the potential links have been explored more in rodents. Herein, we performed an hour-scale metabolomics analysis of serum and colonic digesta to characterize the circadian rhythmic metabolic patterns using a pig model under ad libitum feeding conditions. Importantly, our findings identified potential associations between colonic and body metabolism, revealing the potential relationships between colonic peptides and host appetite regulation. Concretely, amino acids accounted for the highest proportion in rhythmic serum metabolites, whereas lipids accounted for the highest proportion in rhythmic colonic metabolites. The diurnal difference analysis revealed that the levels of most amino acids and peptides were higher in the light phase, while the levels of most lipids were higher in the dark phase. And more correlations were be checked between serum amino acids, lipids, peptides and colonic metabolites in the light and more correlations were be checked between serum carbohydrates, cofactors and vitamins, energy, nucleotides, xenobiotics and colonic metabolites in the dark. Interestingly, peptides oscillated to a similar extent in serum and colonic digesta. Of note, colonic peptides composed of valine, proline and leucine were checked in positive associations to glucagon-like peptide-1 (GLP-1) in serum. And these peptides were positive with the genera Butyricicoccus, Streptococcus, Clostridioides, Bariatricus and Coriobacteriia_norank, and negative with Prevotella, and showed the potential relationships with colonic microbial biosynthesis of amino acids. Collectively, we mapped the rhythmic profiling on pig serum and colonic metabolites and revealed the relationships between host and gut metabolism. However, the underlying regulatory mechanisms remains to be further investigated.

Antihypertensive Effect, ACE Inhibitory Activity, and Stability of Umami Peptides from Yeast Extract

Bioactive peptides from foods have garnered considerable attention as viable supplements for hypertensive patients. Herein, the antihypertensive effect and mechanism of umami peptides from yeast extract were investigated based on the pharmacophore model, simulated digestion, spontaneously hypertensive rat (SHR) model, and molecular docking. Notably, umami peptide LLLLPKP exhibited favorable angiotensin I-converting enzyme (ACE) inhibitory activity (IC50 = 10.22 μM) in vitro and regulated blood pressure in the SHR model with excellent durability. Remarkably, LLLLPKP showed the highest Fitvalue (4.022) of the pharmacophore model, indicating its similar pharmacological effects as ACE inhibitors. During the simulated gastrointestinal digestion, the ACE inhibition rate of LLLLPKP was merely reduced by 5.89%, but it was enzymatically cleaved into 14 peptide segments. The C-terminal sequence comprising L (4), P (5), K (6), and P (7) exhibited robust stability and a notable presence within the peptide segments postdigestion. Meanwhile, according to molecular docking, these four residues within LLLLPKP were responsible for all interactions with key sites within active pockets S1 and S2 and the active pocket of Zn2+. In light of these findings, LLLLPKP is a highly promising antihypertensive peptide. Developing this umami peptide with antihypertensive effects holds substantial importance for the long-term treatment of hypertension.

Impact of a Whey Protein Hydrolysate Treated by Electrodialysis with Ultrafiltration Membrane on the Development of Metabolic Syndrome and the Modulation of Gut Microbiota in Mice

The development of Metabolic Syndrome (MetS) affects a large number of people around the world and represents a major issue in the field of health. Thus, it is important to implement new strategies to reduce its prevalence, and various approaches are currently under development. Recently, an eco-friendly technology named electrodialysis with ultrafiltration membrane (EDUF) was used successfully for the first time at a semi-industrial scale to produce three fractions concentrated in bioactive peptides (BPs) from an enzymatically hydrolyzed whey protein concentrate (WPC): the initial (F1), the final (F2) and the recovery fraction (F3), and it was demonstrated in vitro that F3 exhibited interesting DPP-IV inhibitory effects. Therefore, the present study aimed to evaluate the effect of each fraction on in vivo models of obesity. A daily dose of 312.5 mg/kg was administered to High Fat/High Sucrose diet (HFHS) induced C57BL6/J mice for eight weeks. The physiological parameters of each group and alterations of their gut microbiota by the fractions were assessed. Little effect of the different fractions was demonstrated on the physiological state of the mice, probably due to the digestion process of the BP content. However, there were changes in the gut microbiota composition and functions of mice treated with F3.

Molecular Mechanism of Lotus Seedpod Oligomeric Procyanidins Inhibiting the Absorption of Oligopeptide-Advanced Glycation End Products

Research on advanced glycation end product (AGEs) inhibition has generally focused on food processing, but many protein-AGEs will still be taken. Oligopeptide (OLP)-AGEs, as the main form after digestion, will damage human health once absorbed. Here, we investigated the ability of lotus seedpod oligomeric procyanidins (LSOPC) to inhibit the absorption of the OLP-AGEs and elucidated the underlying mechanism. Our results showed that the inhibition rate of LSOPC on the absorption of OLP-AGEs was about 50 ± 5.38%. 0.1, 0.2, and 0.3 mg/mL could upregulate the expression of ZO-1 and downregulate the expression of PepT1 and clathrin. Molecular docking showed that LSOPC could compete with the binding of OLP-AGEs to PepT1 and AP-2, thus inhibiting the absorption of OLP-AGEs. Furthermore, the interaction of LSOPC with the OLP-AGEs reduced the surface hydrophobicity of OLP-AGEs. It altered the secondary structure of the OLP-AGEs, thus weakening the affinity of the OLP-AGEs to the transporter protein to inhibit the absorption of OLP-AGEs. Together, our data revealed potential mechanisms by which LSOPC inhibit the absorption of OLP-AGEs and opened up new perspectives on the application of LSOPC in reducing the increasing health risks posed by OLP-AGEs.

An in silico approach to unveil peptides from Acheta domesticus with potential bioactivity against hypertension, diabetes, cardiac and pulmonary fibrosis

Entomophagy is a sustainable alternative source of proteins for human nutrition. Acheta domesticus is one of the three insect species that complies with the European Union Regulation on novel foods, but to date, there are no reports on their potential bioactive peptides. In this study, an in silico approach was applied to simulate the gastrointestinal (GI) digestion of six A. domesticus proteins and identify new peptides with potential anti-hypertensive and/or anti-diabetic properties, resulting from their capability to inhibit the somatic Angiotensin-I converting enzyme (sACE) and/or dipeptidyl peptidase 4 (DPP-4), respectively. A molecular docking protocol was applied to evaluate the binding interactions between the 43 peptides ranked with high probability of being bioactive and three drug targets: DPP-4 and two catalytic domains (N- and C-) of sACE. Five peptides (AVQPCF, CAIAW, IIIGW, DATW and QIVW) showed high docking scores for both enzymes, suggesting their potential to inhibit the DPP-4 and both catalytic domains of sACE, thus possessing multifunctional bioactive properties. Two peptides (PIVCF and DVW) showed higher docking scores for the N-domain of sACE, indicating a potential action as selective inhibitors and consequently with anti-cardiac and pulmonary fibrosis bioactivities. This is the first study identifying peptides originated from the simulated GI digestion of A. domesticus with potential activities against hypertension, diabetes, cardiac and pulmonary fibrosis.

Advancing oral delivery of biologics: Machine learning predicts peptide stability in the gastrointestinal tract

The oral delivery of peptide therapeutics could facilitate precision treatment of numerous gastrointestinal (GI) and systemic diseases with simple administration for patients. However, the vast majority of licensed peptide drugs are currently administered parenterally due to prohibitive peptide instability in the GI tract. As such, the development of GI-stable peptides is receiving considerable investment. This study provides researchers with the first tool to predict the GI stability of peptide therapeutics based solely on the amino acid sequence. Both unsupervised and supervised machine learning techniques were trained on literature-extracted data describing peptide stability in simulated gastric and small intestinal fluid (SGF and SIF). Based on 109 peptide incubations, classification models for SGF and SIF were developed. The best models utilized k-Nearest Neighbor (for SGF) and XGBoost (for SIF) algorithms, with accuracies of 75.1% (SGF) and 69.3% (SIF), and f1 scores of 84.5% (SGF) and 73.4% (SIF) under 5-fold cross-validation. Feature importance analysis demonstrated that peptides' lipophilicity, rigidity, and size were key determinants of stability. These models are now available to those working on the development of oral peptide therapeutics.

Critical features of an in vitro intestinal absorption model to study the first key aspects underlying food allergen sensitization

New types of protein sources will enter our diet in a near future, reinforcing the need for a straightforward in vitro (cell-based) screening model to test and predict the safety of these novel proteins, in particular their potential risk for de novo allergic sensitization. The Adverse Outcome Pathway (AOP) for allergen sensitization describes the current knowledge of key events underlying the complex cellular interactions that proceed allergic food sensitization. Currently, there is no consensus on the in vitro model to study the intestinal translocation of proteins as well as the epithelial activation, which comprise the first molecular initiation events (ME1-3) and the first key event of the AOP, respectively. As members of INFOGEST, we have highlighted several critical features that should be considered for any proposed in vitro model to study epithelial protein transport in the context of allergic sensitization. In addition, we defined which intestinal cell types are indispensable in a consensus model of the first steps of the AOP, and which cell types are optional or desired when there is the possibility to create a more complex cell model. A model of these first key aspects of the AOP can be used to study the gut epithelial translocation behavior of known hypo- and hyperallergens, juxtaposed to the transport behavior of novel proteins as a first screen for risk management of dietary proteins. Indeed, this disquisition forms a basis for the development of a future consensus model of the allergic sensitization cascade, comprising also the other key events (KE2-5).

Ocular Delivery of Therapeutic Proteins: A Review

Therapeutic proteins, including monoclonal antibodies, single chain variable fragment (ScFv), crystallizable fragment (Fc), and fragment antigen binding (Fab), have accounted for one-third of all drugs on the world market. In particular, these medicines have been widely used in ocular therapies in the treatment of various diseases, such as age-related macular degeneration, corneal neovascularization, diabetic retinopathy, and retinal vein occlusion. However, the formulation of these biomacromolecules is challenging due to their high molecular weight, complex structure, instability, short half-life, enzymatic degradation, and immunogenicity, which leads to the failure of therapies. Various efforts have been made to overcome the ocular barriers, providing effective delivery of therapeutic proteins, such as altering the protein structure or including it in new delivery systems. These strategies are not only cost-effective and beneficial to patients but have also been shown to allow for fewer drug side effects. In this review, we discuss several factors that affect the design of formulations and the delivery of therapeutic proteins to ocular tissues, such as the use of injectable micro/nanocarriers, hydrogels, implants, iontophoresis, cell-based therapy, and combination techniques. In addition, other approaches are briefly discussed, related to the structural modification of these proteins, improving their bioavailability in the posterior segments of the eye without affecting their stability. Future research should be conducted toward the development of more effective, stable, noninvasive, and cost-effective formulations for the ocular delivery of therapeutic proteins. In addition, more insights into preclinical to clinical translation are needed.

Tryptophan metabolism and gut flora profile in different soybean protein induced enteritis of pearl gentian groupers

The substitution of high-level soy meals for fish meal (FM) generally leads to fish enteritis, accompanied by significant variations in gut flora. Relevant studies have pointed out a close relationship between tryptophan metabolism mediated by gut flora and vertebrate inflammatory bowel disease. Present study examines the role of tryptophan metabolism and gut flora profile in fish enteritis caused by different soybean meals. The 960 groupers were randomly assigned into 4 groups (n = 4), which including: (1) FM (the control group, fed with 50% FM feed), (2) SBM40 (replacing 40% FM with soybean meal), (3) SPC40 (replacing 40% FM with soybean protein concentrate), and (4) FSBM40 (replacing 40% FM with fermented soybean meal). Under average temperature and natural light, the groupers were cultivated with feeds of iso-nitrogen and iso-lipid for 10 weeks. The results showed that soybean meal feeds at all experimental levels had negative effects on fish gut physiology and growth performance. Typical enteritis features and fluctuations of immune system occur, which can be observed in the enzyme activities of total superoxide dismutase and lysozyme and in the contents of immunoglobulin M, complement 3 and complement 4. 16SrDNA high-throughput sequencing indicated that it greatly influenced the gut flora with the abundance of maleficent bacteria, like Vibrio, amplified with increasing dietary soybean meals. According to the "3 + 2" full-length transcriptome sequencing, soy meals at the three experimental levels inhibited the key gene expressions of tryptophan metabolic pathway in fish gut, however, there are some differences in the types of key genes that are inhibited. The canonical correlation analysis showed that the changes in key gene expressions in tryptophan metabolic pathway had a positive correlation with the expressions of pro-inflammatory genes (P < 0.05) and negatively correlated with the expression of anti-inflammatory genes (P < 0.05). It is speculated from this study that tryptophan metabolism is closely related to fish soy meal-related enteritis, and the abnormal tryptophan metabolism caused by intestinal flora imbalance may play an important role. In the future research, we can further study the tolerance of fish to soy meals feed from two aspects of tryptophan metabolism and intestinal flora changes.

Interaction mechanism of three egg protein derived ACE inhibitory tri-peptides and DPPC membrane using FS, FTIR, and DSC studies

Understanding the interaction of food derived angiotensin converting enzyme (ACE) inhibitory peptides and intestinal epithelial cell membrane may help to improve their absorption. This research aimed to study the molecular interaction of ACE inhibitory tri-peptides ADF, FGR, and MIR with DPPC membrane during absorption process. The DPPC liposome was prepared and characterized, then used as a model membrane. The permeability of tri-peptides across the membrane was investigated using Fluorescence spectroscopy. The effect of tri-peptides on the structure and dynamics of DPPC bilayers was determined using Fourier transform infrared spectroscopy. The effect of tri-peptides on the phase transition temperature in the DPPC membrane was also analyzed using Differential scanning calorimetry. The results showed that ACE inhibitory tri-peptides ADF, FGR, and MIR can penetrate into both the membrane-water interface and hydrophobic region of DPPC bilayer, and the tri-peptide FGR have higher permeability across the membrane.

Tripeptide Leu-Pro-Phe from Corn Protein Hydrolysates Attenuates Hyperglycemia-Induced Neural Tube Defect in Chicken Embryos

Neural tube defect (NTD) is the most common and severe embryopathy causing embryonic malformation and even death associated with gestational diabetes mellitus (GDM). Leu-Pro-Phe (LPF) is an antioxidative tripeptide isolated from hydrolysates of corn protein. However, the biological activity of LPF in vivo and in vitro remains unclear. This study is aimed at investigating the protective effects of tripeptide LPF against NTD in the high glucose exposure condition and delineate the underlying biological mechanism. We found that LPF alleviated NTD in the high glucose-exposed chicken embryo model. In addition, DF-1 chicken embryo fibroblast was loaded with high glucose for induction of oxidative stress and abnormal O-GlcNAcylation in vitro. LPF significantly decreased accumulation of reactive oxygen species and content of malondialdehyde in DF-1 cells but increased the ratio of reduced glutathione and oxidized glutathione in chick embryo. Oxygen radical absorbance capacity results showed that LPF itself had good free radical scavenging capacity and could enhance antioxidant activity of the cell content. Mechanistic studies suggested that the resistance of LPF to oxidative damage may be related to promotion of NRF2 expression and nuclear translocation. LPF alleviated the overall O-GlcNAcylation level of cellular proteins under high glucose conditions and restored the level of Pax3 protein. Collectively, our findings indicate that LPF peptide could act as a nutritional supplement for the protection of development of embryonic neural tube affected by GDM.

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.

Pep19 Has a Positive Effect on Insulin Sensitivity and Ameliorates Both Hepatic and Adipose Tissue Phenotype of Diet-Induced Obese Mice

Peptide DIIADDEPLT (Pep19) has been previously suggested to improve metabolic parameters, without adverse central nervous system effects, in a murine model of diet-induced obesity. Here, we aimed to further evaluate whether Pep19 oral administration has anti-obesogenic effects, in a well-established high-fat diet-induced obesity model. Male Swiss mice, fed either a standard diet (SD) or high-fat diet (HFD), were orally administrated for 30 consecutive days, once a day, with saline vehicle or Pep19 (1 mg/kg). Next, several metabolic, morphological, and behavioral parameters were evaluated. Oral administration of Pep19 attenuated HFD body-weight gain, reduced in approximately 40% the absolute mass of the endocrine pancreas, and improved the relationship between circulating insulin and peripheral insulin sensitivity. Pep19 treatment of HFD-fed mice attenuated liver inflammation, hepatic fat distribution and accumulation, and lowered plasma alanine aminotransferase activity. The inguinal fat depot from the SD group treated with Pep19 showed multilocular brown-fat-like cells and increased mRNA expression of uncoupling protein 1 (UCP1), suggesting browning on inguinal white adipose cells. Morphological analysis of brown adipose tissue (BAT) from HFD mice showed the presence of larger white-like unilocular cells, compared to BAT from SD, Pep19-treated SD or HFD mice. Pep19 treatment produced no alterations in mice behavior. Oral administration of Pep19 ameliorates some metabolic traits altered by diet-induced obesity in a Swiss mice model.

Alpha-ketoglutarate, a key molecule involved in nitrogen circulation in both animals and plants, in the context of human gut microbiota and protein metabolism

PURPOSE

Nitrogen (N₂) is an indispensable metabolite required for the synthesis of protein. In animals, gut bacteria and, to a certain extent, even hepatocytes, are able to assimilate nitrogen from ammonium (NH₄⁺), which is essentially derived from the amine group (-NH₂) and which is at the same time a very toxic metabolite. Initially, NH₄⁺ is coupled to alpha-ketoglutarate (AKG), a reaction which results in the appearance of glutamate (one amine group), and after that, in the appearance of glutamine - containing two amine groups. The surplus of NH₄⁺ which is not utilized by AKG/glutamate/glutamine is eliminated as urea in the urine, via the urea cycle in hepatocytes. Plants bacteria also assimilate nitrogen from NH₄⁺, by its fixation to ammonia (NH₃)/NH₄⁺.

MATERIALS/METHODS

Previous studies have shown that AKG (also known as 2-oxo-glutaric acid or 2-oxopentanedioic acid), the primary metabolite of Rhizobium and gut bacteria, is essential for the assimilation of nitrogen.

RESULTS

Symbiotic bacteria produce AKG, which together with glutamate dehydrogenase (GDH), 'generates' primarily amine groups from NH₄⁺. The final product is glutamate - the first amino acid. Glutamate has the capacity to be converted to glutamine, through the action of glutamine synthetase, after the assimilation of the second nitrogen from NH₄⁺.

CONCLUSION

Glutamate/glutamine, derivatives of AKG metabolism, are capable of donating amine groups for the creation of other amino acids, following NH₂ transamination to certain metabolites e.g., short chain fatty acids (SCFA).

In vitro digestion characteristics of cereal protein concentrates as assessed using a pepsin-pancreatin digestion model

An alkaline extraction method has been used in many studies to extract total protein from cereal samples. Wheat bran protein concentrate (WBPC), oat bran protein concentrate (OBPC), and barley protein concentrate (BPC) were prepared by alkaline extraction and isoelectric precipitation to study their functional and nutritional properties. The three protein concentrates were hydrolysed by an in vitro pepsin-pancreatin digestion model. Their digestibility (%) and degree of hydrolysis (DH%) were evaluated, and SDS-PAGE electrophoresis was used to illustrate the protein and peptides patterns. The change of the particle sizes and the release of the essential amino acids was followed during the digestion process. The in vitro digestibility of WBPC, OBPC and BPC was 87.4%, 96.1% and 76.9%, respectively. The DH% of protein concentrates were between 50 and 60%. The change of the particle size distribution values Dv(50) was assumed to be related to protein aggregations during the digestion. The protein fractions were identified and the degradation during the digestion and were analysed by SDS-PAGE; the gels of WBPC and OBPC digestion showed virtually complete degradation whereas the intensive bands of undigested protein were presented for BPC. The generation of the free amino acids and short chain peptides were significantly higher at the end of the intestinal digestion compared to the stages of before and after gastric digestion. Higher content of the deficient amino acids such as lysine and threonine were found comparing to the level of deficient amino acids in cereal grains but does not meet the daily recommended intake.

Metabolic Fate and Bioavailability of Food-Derived Peptides: Are Normal Peptides Passed through the Intestinal Layer To Exert Biological Effects via Proposed Mechanisms?

Previous studies have demonstrated that the oral administration of food-derived peptides exerts beneficial effects on human health beyond conventional nutritional functions. In vitro studies have suggested potential mechanisms and active peptides. However, the levels of most food-derived peptides in the body are far lower than the concentrations used in the in vitro assays, with some exceptions. These facts suggest that food-derived peptides might be metabolized into active compounds or function via different mechanisms than the proposed mechanisms. This work briefly discusses the perspectives related to the metabolites of the food-derived peptides in the body.

Characterizing the spatial distribution of dipeptides in rodent tissue using MALDI MS imaging with on-tissue derivatization

A highly efficient on-tissue derivatization method for the matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) of dipeptides in tissues has been developed via a combination of a home-built laser-assisted chemical transfer (LACT) technique and hexafluoroisopropanol (HFIP).

Measuring the oral bioavailability of protein hydrolysates derived from food sources: A critical review of current bioassays

BACKGROUND

Food proteins are a source of hydrolysates with potentially useful biological attributes. Bioactive peptides from food-derived proteins are released from hydrolysates using exogenous industrial processes or endogenous intestinal enzymes. Current in vitro permeability assays have limitations in predicting the oral bioavailability (BA) of bioactive peptides in humans. There are also difficulties in relating the low blood levels of food-derived bioactive peptides detected in preclinical in vivo models to pharmacodynamic read-outs relevant for humans.

SCOPE AND APPROACH

In this review, we describe in vitro assays of digestion, permeation, and metabolism as indirect predictors of the potential oral BA of hydrolysates and their constituent bioactive peptides. We discuss the relationship between industrial hydrolysis processes and the oral BA of hydrolysates and their peptide by-products.

KEY FINDINGS

Hydrolysates are challenging for analytical detection methods due to capacity for enzymatic generation of peptides with novel sequences and also new modifications of these peptides during digestion. Mass spectrometry and peptidomics can improve the capacity to detect individual peptides released from complex hydrolysates in biological milieu.

Oral intake of rice overexpressing ubiquitin ligase inhibitory pentapeptide prevents atrophy in denervated skeletal muscle

We previously reported that intramuscular injections of ubiquitin ligase CBLB inhibitory pentapeptide (Cblin; Asp-Gly-pTyr-Met-Pro) restored lost muscle mass caused by sciatic denervation. Here, we detected Cblin on the basolateral side of Caco-2 cells after being placed on the apical side, and found that cytochalasin D, a tight junction opener, enhanced Cblin transport. Orally administered Cblin was found in rat plasma, indicating that intact Cblin was absorbed in vitro and in vivo. Furthermore, transgenic Cblin peptide-enriched rice (CbR) prevented the denervation-induced loss of muscle mass and the upregulation of muscle atrophy-related ubiquitin ligases in mice. These findings indicated that CbR could serve as an alternative treatment for muscle atrophy.

Properties of peptides released from salmon and carp via simulated human-like gastrointestinal digestion described applying quantitative parameters

Apart from the classical (experimental) methods, biologically active peptides can be studied via bioinformatics approach, also known as in silico analysis. This study aimed to verify the following research hypothesis: ACE inhibitors and antioxidant peptides can be released from salmon and carp proteins during simulated in silico human-like gastrointestinal digestion. The potential to release biopeptides was evaluated using the BIOPEP-UWM quantitative criteria including the profile of biological activity, frequency of the occurrence (A)/release (AE) of fragments with an ACE inhibitory or antioxidant activity by selected enzymes, and relative frequency of release of bioactive fragments with a given activity by selected enzymes (W). Salmon collagen and myofibrillar proteins of carp turned out to be the best potential source of the searched peptides-ACE inhibitors and antioxidant peptides. Nonetheless, after digestion, the highest numbers of ACE inhibitors and antioxidant peptides were potentially released from the myofibrillar proteins of salmon and carp. Peptide Ranker Score, Pepsite2, and ADMETlab platform were applied to evaluate peptides' bioactivity potential, their safety and drug-like properties. Among the 63 sequences obtained after the simulated digestion of salmon and carp proteins, 30 were considered potential biopeptides. The amino acid sequences of ACE-inhibiting and antioxidant peptides were predominated by P, G, F, W, R, and L. The predicted high probability of absorption of most analyzed peptides and their low toxicity should be considered as their advantage.

Zinc in Dog Nutrition, Health and Disease: A Review

Simple Summary

This work compiles the current state of knowledge regarding zinc requirements of healthy dogs and biomarkers of zinc status. To ensure an adequate zinc status, it is important to know the zinc content of foods and their bioavailability to assess the need and the ideal supplementation strategy regarding levels and sources of additives in complete dog foods. As zinc is required for enzymatic, structural, and regulatory functions in the animal body, its nutritional status has been associated with several pathologies that may be due to, or exacerbated by, a deficit of dietary zinc supply.

Abstract

Zinc is an essential trace element, required for enzymatic, structural, and regulatory functions. As body reserves are scarce, an adequate zinc status relies on proper dietary supply and efficient homeostasis. Several biomarkers have been proposed that enable the detection of poor zinc status, but more sensitive and specific ones are needed to detect marginal deficiencies. The zinc content of commercial dry dog foods has great variability, with a more frequent non-compliance with the maximum authorized limit than with the nutritional requirement. The bioavailability of dietary zinc also plays a crucial role in ensuring an adequate zinc status. Despite controversial results, organic zinc sources have been considered more bioavailable than inorganic sources, albeit the zinc source effect is more evident after a restriction period of dietary zinc. Many disorders have been associated with inadequate zinc status, not being clear whether the occurrence of the disease is the consequence or the cause. This review presents data on zinc requirements and biomarkers for zinc status, that can be applied for the development of supplementation strategies of zinc in complete pet foods. Moreover, it provides an understanding of the role zinc plays in the health of dogs, and how altered zinc status affects diseases in dogs.

Identification of peptides in blood following oral administration of β-conglycinin to Wistar rats

In this study, β-conglycinin (100 mg/kg) was orally administered to Wistar rats in order to identify peptides that may be derived from the protein in the blood. Plasma samples taken from the tail vein up to 8 h after administration were analyzed by matrix-assisted laser desorption/ionization (MALDI) and liquid chromatography-time-of-flight (LC-TOF) mass spectrometry (MS). In total, 126 signals were detected by MALDI-MS. Among the signals, nine oligopeptides (SEL, KGPL, SILGA, DSEL, GDANI, SYFV, CLQSC, GEQPRPF, and LVINEGDA) were successfully identified as β-conglycinin-derived peptides by LC-TOF/MS at a plasma concentration of 0.75-756 pmol/mL. The results demonstrated that β-conglycinin could be the dietary source protein for the oligopeptides produced prior to entering the circulating bloodstream of rats.

A specific selenium-chelating peptide isolated from the protein hydrolysate of Grifola frondosa

Background: Grifola frondosa is a type of edible medicinal mushroom with abundant proteins. Selenium (Se) is an essential micronutrient for human. Many animal experiments and clinical studies had indicated that Se plays an important role in diverse physiologic actions. Most inorganic selenium compounds are toxic, and the lowest lethal dose is relatively small. Peptide-Se chelate can probably be dietary supplements in functional foods for humans with Se deficiency. Methods: In this study, a specific tripeptide Arg-Leu-Ala (RLA) with strong Se-chelating capacity was purified from Grifola frondosa through ultrafiltration, reversed-phase HPLC and gel filtration chromatography. The UV, SEM, XRD, 1H NMR spectra are shown to provide more information about characterization of RLA-Se chelates. The bioavailability of RLA-Se chelate in Caco-2 cell line was investigated by using human colon cancer Caco-2 cells as model. iTRAQ comparative proteomics approach were used to identify the differentially expressed proteins. Results: The Se binding capacity of RLA was 84.47 ± 1.21 mg g-1. The results of UV, X-ray diffraction (XRD), 1H NMR and SEM structure analysis showed that the binding of selenium in the hydrolysate of Grifola frondosa protein was successful, and the amino and carboxyl groups of RLA were involved in the coordination of Se, which was the main site of chelation. The results of absorption of RLA-Se chelate in Caco-2 cells showed that RLA-Se chelate could be used as selenium supplement source. Using iTRAQ comparative proteomics approach, 40 proteins found significant. RLA-Se treatment had been demonstrated to present a higher accumulation of Se compared with control treatment and show an effective absorption by Caco-2 with the result that E3 protein performed up regulation. RLA-Se may play roles in cell cycle and apoptosis as an essential micronutrient. To sum up, our research results show that Grifola polypeptide-Se chelate is a promising multifunctional organic selenium product, which can be used as a new functional supplement for selenium deficiency.

Peptidomimetics Therapeutics for Retinal Disease

Ocular disorders originating in the retina can result in a partial or total loss of vision, making drug delivery to the retina of vital importance. However, effectively delivering drugs to the retina remains a challenge for ophthalmologists due to various anatomical and physicochemical barriers in the eye. This review introduces diverse administration routes and the accordant pharmacokinetic profiles of ocular drugs to aid in the development of safe and efficient drug delivery systems to the retina with a focus on peptidomimetics as a growing class of retinal drugs, which have great therapeutic potential and a high degree of specificity. We also discuss the pharmacokinetic profiles of small molecule drugs due to their structural similarity to small peptidomimetics. Lastly, various formulation strategies are suggested to overcome pharmacokinetic hurdles such as solubility, retention time, enzymatic degradation, tissue targeting, and membrane permeability. This knowledge can be used to help design ocular delivery platforms for peptidomimetics, not only for the treatment of various retinal diseases, but also for the selection of potential peptidomimetic drug targets.

Techniques, perspectives, and challenges of bioactive peptide generation: A comprehensive systematic review

Due to the digestible refractory and absorbable structures of bioactive peptides (BPs), they could induce notable biological impacts on the living organism. In this regard, the current study was devoted to providing an overview regarding the available methods for BPs generation by the aid of a systematic review conducted on the published articles up to April 2019. In this context, the PubMed and Scopus databases were screened to retrieve the related publications. According to the results, although the characterization of BPs mainly has been performed using enzymatic and microbial in-vitro methods, they cannot be considered as suitable techniques for further stimulation of digestion in the gastrointestinal tract. Therefore, new approaches for both in-vivo and in-silico methods for BPs identification should be developed to overcome the obstacles that belonged to the current methods. The purpose of this review was to compile the recent analytical methods applied for studying various aspects of food-derived biopeptides, and emphasizing generation at in vitro, in vivo, and in silico.

Identification and comparison of proteomic and peptide profiles of mung bean seeds and sprouts

The objectives of this study were to analyze and compare the proteomic and peptide profiles of mung bean (Vigna radiata) seeds and sprouts. Label-free proteomics and peptidomics technologies allowed the identification and relative quantification of proteins and peptides. There were 1918 and 1955 proteins identified in mung bean seeds and sprouts, respectively. The most common biological process of proteins in these two samples was the metabolic process, followed by cellular process and single-organism process. Their dominant molecular functions were catalytic activity, binding, and structural molecule activity, and the majority of them were the cell, cell part, and organelle proteins. These proteins were primarily involved in metabolic pathways, biosynthesis of secondary metabolites, and ribosome. PCA and HCA results indicated the proteomic profile varied significantly during mung bean germination. A total of 260 differential proteins between mung bean seeds and sprouts were selected based on their relative abundance, which were associated with the specific metabolism during seed germination. There were 2364 peptides identified and 76 potential bioactive peptides screened based on the in silico analysis. Both the types and concentration of the peptides in mung bean sprouts were higher than those in seeds, and the content of bioactive peptides in mung bean sprouts was deduced to be higher.

Bioactive peptides from food fermentation: A comprehensive review of their sources, bioactivities, applications, and future development

Bioactive peptides (BPs) are specific protein fragments that exert various beneficial effects on human bodies and ultimately influence health, depending on their structural properties and amino acid composition and sequences. By offering promising solutions to solve diverse health issues, the production, characterization, and applications of food-derived BPs have drawn great interest in the current literature and are of particular interest to the food and pharmaceutical industries. The microbial fermentation of protein from various sources is indubitably a novel way to produce BPs with numerous beneficial health effects. Apart from its lower cost as compared to enzymes, the BPs produced from microbial fermentation can be purified without further hydrolysis. Despite these features, current literature shows dearth of information on the BPs produced from food via microbial fermentation. Hence, there is a strong necessity to explore the BPs obtained from food fermentation for the development of commercial nutraceuticals and functional foods. As such, this review focuses on the production of BPs from different food sources, including the extensively studied milk and milk products, with emphasis on microbial fermentation. The structure-activity (antihypertensive, antioxidant, antimicrobial, opiate-like, anti-inflammatory, anticancer/antiproliferative, antithrombotic, hypolipidemic, hypocholesterolemic, and mineral binding) relationship, potential applications, future development, and challenges of BPs obtained from food fermentation are also discussed.

Characteristics of Biopeptides Released In Silico from Collagens Using Quantitative Parameters

The potential of collagens to release biopeptides was evaluated using the BIOPEP-UWM-implemented quantitative criteria including the frequency of the release of fragments with a given activity by selected enzyme(s) (AE), relative frequency of release of fragments with a given activity by selected enzyme(s) (W), and the theoretical degree of hydrolysis (DHt). Cow, pig, sheep, chicken, duck, horse, salmon, rainbow trout, goat, rabbit, and turkey collagens were theoretically hydrolyzed using: stem bromelain, ficin, papain, pepsin, trypsin, chymotrypsin, pepsin+trypsin, and pepsin+trypsin+chymotrypsin. Peptides released from the collagens having comparable AE and W were estimated for their likelihood to be bioactive using PeptideRanker Score. The collagens tested were the best sources of angiotensin I-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibitors. AE and W values revealed that pepsin and/or trypsin were effective producers of such peptides from the majority of the collagens examined. Then, the SwissTargetPrediction program was used to estimate the possible interactions of such peptides with enzymes and proteins, whereas ADMETlab was applied to evaluate their safety and drug-likeness properties. Target prediction revealed that the collagen-derived peptides might interact with several human proteins, especially proteinases, but with relatively low probability. In turn, their bioactivity may be limited by their short half-life in the body.

Effect of Food Preparations on In Vitro Bioactivities and Chemical Components of Fucus vesiculosus

Fucus vesiculosus is a brown macroalgae used in food and generally considered safe to be consumed, according to EU Directive (EC 258/97). The aim of this study is to analyze the effect of food preparation on F.vesiculosus of different origins on what concerns its chemical constituents and final bioactivities. The aqueous extract of the seaweeds were obtained at different temperatures, similar to food preparation and then purified by SPE. The compound identification was carried out by Liquid Chromatography High Resolution Mass Spectrometry (LC-HRMS/MS) and algae extracts microstructure were observed by Scanning Electron Microscopy (SEM). The activities were determined by using antioxidant activity, inhibition of acetylcholinesterase (AChE) and 3-hidroxi-3-methyl-glutaril-CoA (HMG-CoA) reductase (HMGR) together with Caco-2 cells line simulating the intestinal barrier. The activity of AChE and the HMGR were inhibited by the extracts giving IC₅₀ values of 15.0 ± 0.1 µg/mL and 4.2 ± 0.1 µg/mL, respectively and 45% of the cholesterol permeation inhibition. The main compounds identified were phlorotannins and peptides derivatives. The mode of preparation significantly influenced the final bioactivities. Moreover, the in vitro results suggest that the preparation of F. vesiculosus as a soup could have hypercholesterolemia lowering effect.