Dipeptidyl peptidase-IV inhibitory peptides generated by tryptic hydrolysis of a whey protein concentrate rich in β-lactoglobulin

Efficient purification and identification of α-glucosidase inhibitory peptides from rice proteins by enzyme membrane reactors

Bioactive peptides are growingly recognized with exceptional therapeutic abilities against numerous chronic diseases such as cardiovascular diseases. However, the advancement of peptide manufacturing is hindered by the trade-off between protein-peptide bioconversion and bioactivity retention. In this study, we demonstrate the efficient preparation of rice peptides using enzymatic membrane reactors (EMRs). Owing to the delicately coupled enzymatic hydrolysis and timely filtration, these peptides featured highly integral molecular structures pertinent to their bioactivities, while thorough hydrolysis ensured a high protein-peptide bioconversion (78.06 %). Specifically, over 89 % of the peptides prepared by EMRs had molecular weights <1 kDa, exhibiting significantly enhanced α-glucosidase inhibitory capacities (by 41.67 %) as compared to the conventional direct hydrolysis method (DEH). Furthermore, this technique significantly enhanced the peptide screening efficiency by 91.88 % due to increased screening accuracy. Our study would properly solve the technical challenges concerning the paradox between bioconversion and bioactivity for efficient manufacturing of bioactive peptides.

A comparative study on antidiabetic and anti-inflammatory activities of fermented whey and soy protein isolates and the release of biofunctional peptides: an in vitro and in silico studies

BACKGROUND

This study aims to evaluate the antidiabetic and anti-inflammatory activities of Lacticaseibacillus rhamnosus (M9) MTCC 25516 during the fermentation of whey and soy protein isolates. It also seeks to characterize protein profiles, identify multifunctional peptides, and assess structural changes using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional (2D) gel electrophoresis, Fourier-transform infrared (FTIR) spectroscopy, and confocal laser scanning microscopy (CLSM).

RESULTS

Fermentation with Lacticaseibacillus rhamnosus (M9) significantly enhanced antidiabetic activity, with optimal peptide production at a 25 mL L-1 inoculation rate for 48 h at 37 °C. Proteolytic activity reduced inflammatory markers (IL-6, TNF-α, IL-1β, NO) in RAW 267.4 cells. SDS-PAGE and 2D gel electrophoresis revealed distinct protein profiles, with 19 and 49 protein spots in whey and soy isolates, respectively. Reverse-phase high-performance liquid chromatography (RP-HPLC) identified multifunctional peptides, and FTIR spectroscopy confirmed structural changes post-fermentation. Confocal microscopy further revealed protein modifications.

CONCLUSION

Fermentation of whey and soy protein isolates with Lacticaseibacillus rhamnosus (M9) enhances antidiabetic and anti-inflammatory properties. Optimal conditions (25 mL L-1 inoculation, 48-h incubation) improved peptide production, with analytical techniques confirming structural and functional changes. These findings suggest fermented protein isolates could be valuable in functional foods with health benefits. © 2025 Society of Chemical Industry.

Peptidomics and molecular dynamics on bioactive peptides produced and characterized from the fermented whey of "Panchali" sheep of West India

The study assessed the peptide production by using potent Lactiplantibacillus plantarum KGL3A (MG722814) culture to ferment the sheep milk for evaluation of α-glucosidase inhibition, ACE inhibition, α-amylase inhibition, & inhibiting lipase activities. The maximal ACE inhibitory, α-amylase, α-glucosidase, & lipase inhibiting actions were 71.69 %, 71.32 %, 67.14 %, and 64.15 %, respectively, at 37 °C after 48 h. Proteolytic activity was tested at various incubation times & inoculation rates to maximise the conditions for growth and the greatest action (9.38 mg/mL) was reported at 2.5 % rate of inoculation after incubation of 48 h. The anti-diabetic as well as ACE inhibitory properties of less than 3 kDa were maximum in contrast to >3 kDa, <10 kDa, and > 10 kDa cut-off fractions. Further, when LPS stimulation is applied to RAW 267.4 macrophage cells, the overabundance generation of IL-6, IL-1β, NO, and TNF-α is greatly reduced by using KGL3A to ferment sheep milk. 2D gel electrophoresis & SDS-PAGE were utilized in relation to protein purifications. Maximum numbers of sheep milk's fermented protein bands were present, about 10 to 124 kDa by SDS-PAGE, and 38 spots of protein were discovered using 2D gel chromatography. Ultra-filtered fractions water soluble extracts (WSEs) were employed in RP-HPLC to differentiate between various peptide fractions. The peptide sequences produced were matched using the databases of AHTPDB and BIOPEP to match hypertensive peptides & antidiabetic peptides, respectively. Furthermore, the discovered peptide sequences from the fermenting sheep milk was studied due to their penchant for binding against the active locations of human bile salt activated lipase (hBAL); human maltase-glucoamylase (hMGA); human pancreatic alpha-amylase (hPAM); & human angiotensin-converting enzyme (hACE) through molecular docking.

Pulse protein quality and derived bioactive peptides

There is a growing consumer interest in sources of dietary protein that are plant-based. Pulse crops, such as lentils, beans, chickpeas, and peas, are gaining popularity due to their environmental sustainability, nutrient density, and functional attributes. The protein content and quality of pulses vary across different pulse classes and processing methods. The biological properties of the protein and the physiologically active peptides make pulse crops attractive as potentially functional or health-promoting foods. This review highlights the nutritional quality of pulse proteins as determined by the Protein Efficiency Ratio and Protein Digestibility Corrected Amino Acid Score as well as bioactive properties of specific bioactive peptides related to amelioration of hypertension and diabetes. Additionally, the use of proteomics platforms, such as mass spectrometry, in combination with bioinformatics tools, enables the identification and characterization of bioactive peptides in pulse crops. These technologies facilitate the development of pulse-derived products with enhanced nutritional values. Overall, the high nutritional quality of pulse-based proteins supports the benefits of pulse inclusion in the diet, which can also exert beneficial bioactivities resulting in improving outcomes in non-communicable diseases.

The effects of whey protein supplementation on indices of cardiometabolic health: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

The increasing prevalence of cardiometabolic diseases highlights the urgent need for practical interventions to mitigate their associated public health burden. Whey protein supplementation has emerged as a potential intervention for improving markers of cardiometabolic health. The aim of this systematic review and meta-analysis was to examine the effect of whey protein ingestion on cardiometabolic profile in adults.

METHODS

A systematic search was conducted in PubMed, Web of Science, Scopus, and Cochrane Library from inception until June 2024. Eligible RCTs compared the effect of whey protein supplementation compared to placebo or a carbohydrate-based control on markers of cardiometabolic health. Using the random effects inverse-variance model, we estimated the mean difference (MD) in blood pressure, high- and low-density lipoproteins (HDL-cholesterol, LDL-cholesterol), total cholesterol, triglycerides, and homeostatic model assessment for insulin resistance (HOMA-IR) index.

RESULTS

This meta-analysis included 21 RCTs. Whey protein supplementation had no effect on HDL-cholesterol concentration but did elicit a reduction in LDL-cholesterol in individuals aged <50 years (P < 0.01) and when combined with exercise (MD: -5.38, 95 % confidence interval (95 % CI): -8.87 to -1.88, I2 = 0 %, P < 0.01). Total cholesterol was reduced with interventions that combined whey protein supplementation and exercise (MD: -8.58, -14.32 to -2.83, I2 = 55 %, P < 0.01), irrespective of age, protein dose, and body mass index ≥25 kg/m2 (MD: -6.71, 95 % CI: -11.60 to -1.83, I2 = 74 %, P < 0.01). Whey protein supplementation of ≥12 weeks was associated with reduced triglyceride levels (MD: -6.61, 95 % CI: -11.06 to -2.17, I2 = 70 %, P < 0.01). There was no clinically relevant effect of whey protein supplementation on blood pressure and HOMA-IR, however, changes pertinent to HDL-cholesterol, total cholesterol, and triglyceride reduction were primarily displayed in healthy adults.

CONCLUSIONS

Whey protein supplementation may be an effective intervention for reducing LDL and total cholesterol levels, particularly in healthy, overweight/obese adults aged <50 years, with the greatest benefits observed when combined with exercise. Healthy adults also showed a benefit regarding triglyceride levels.

Discovery of novel dipeptidyl peptidase-IV inhibitory peptides derived from walnut protein and their bioactivities in vivo and in vitro

The inhibition of dipeptidyl peptidase IV (DPP-IV) has been regarded as a major target for treating type-2 diabetes (T2D). Food-derived peptides are a great source of DPP-IV inhibitory peptides. In this study, we utilized walnut protein as the raw material and hydrolyzed it using four different proteases. The trypsin hydrolysate exhibited the highest DPP-IV inhibitory activity. A DEAE-52 anion exchange column and a Sephadex G-25 gel filtration column were used to sequentially separate and purify the enzymatic hydrolysates. Mass spectrometry identified 117 peptide sequences, of which LPFA, VPFWA, and WGLP were three highly active DPP-IV inhibitory peptides. Molecular docking results revealed that three peptides primarily bind tightly to DPP-IV through hydrogen bonds and van der Waals forces. The inhibitory activity and absorption transport of the peptides were examined using a Caco-2 cell model. LPFA, VPFWA, and WGLP could cross the Caco-2 cell monolayer intact, with in situ IC50s of 267.9 ± 7.2 μM, 325.0 ± 8.4 μM, and 350.9 ± 8.3 μM, respectively. Oral glucose tolerance tests (OGTT) demonstrated that the three inhibitory peptides significantly improved glucose metabolism in normal ICR mice. This study establishes a theoretical basis for the high-value utilization of walnuts and the therapeutic treatment of T2D.

Precooked Jack Bean [Canavalia ensiformis (L.) DC] Sprout: Generation of Dipeptidyl Peptidase-IV Inhibitory Peptides during Simulated Digestion

Bioactive peptides generated from jack bean sprouts are reported to function as dipeptidyl peptidase IV (DPP-IV) inhibitors. However, no studies have investigated the effect of precooking followed by simulated digestion using pepsin-pancreatin to increase DPP-IV inhibitory peptide generation in jack bean sprouts. Therefore, the present study aimed to explore the generation of DPP-IV inhibitory peptides from precooked jack bean [Canavalia ensiformis (L.) DC] sprouts during simulated digestion with pepsin-pancreatin. The results showed that peptide fractions of the sample hydrolysate with molecular weight <1 kDa exhibited the strongest DPP-IV inhibitory activity (84.77%±0.49%) after simulated digestion. This activity was slightly greater than that (74.12%±0.85%) observed prior to simulated digestion. These findings demonstrate that the DPP-IV inhibitory activity of precooked jack bean sprouts can be retained following simulated digestion. Moreover, our investigation revealed the sequences of two novel peptides following simulated digestion with critical amino acids. The presence of alanine and glycine at the penultimate N-terminus of AAGPKP and LGDLLK confirmed the presence of DPP-IV inhibitors. Both peptide sequences are nontoxic and interact with the catalytic sites of enzymes through hydrogen bonds.

Characterization of Peptide Profiles and the Hypoallergenic and High Antioxidant Activity of Whey Protein Hydrolysate Prepared Using Different Hydrolysis Modes

Food proteins and peptides are generally considered a source of dietary antioxidants. The aim of this study was to investigate the antioxidant activity, allergenicity, and peptide profiles of whey protein hydrolysates (WPHs) using different hydrolysis methods. The results demonstrated that the degrees of hydrolysis of the hydrolysates with one-step (O-AD) and two-step (T-AD) methods reached 16.25% and 17.64%, respectively. The size exclusion chromatography results showed that the O-AD had a higher content of >5 and <0.3 kDa, and the distribution of peptide profiles for the two hydrolysates was significantly different. Furthermore, 5 bioactive peptides and 15 allergenic peptides were identified using peptidomics. The peptide profiles and the composition of the master proteins of the O-AD and T-AD were different. The DPPH and ABTS radical scavenging abilities of WPHs were measured, and hydrolysates were found to exhibit a strong radical scavenging ability after being treated using different hydrolysis methods. An enzyme-linked immunosorbent assay showed that the sensitization of WPHs was significantly reduced. This study may provide useful information regarding the antioxidant properties and allergenicity of WPHs.

DPP-IV Inhibitory Peptide against In Vitro Gastrointestinal Digestion Derived from Goat's Milk Protein and Its Activity Enhancement via Amino Acid Substitution

Goat milk protein can release a variety of bioactive peptides after digestion, while most of them are digested into free amino acids or dipeptides via the GI tract. We investigated the peptide profiles of goat milk protein following in vitro gastrointestinal digestion using LC-MS/MS and identified 683 bioactive peptides, including 105 DPP-IV inhibitory peptides. Among these peptides, ILDKVGINY (IL), derived from β-lactoglobulin, was found to be high in content and resistance to digestion. Herein, we explore the effect of amino acid residue substitution at the second N-terminus on its DPP-IV inhibitory activity. Three 9 polypeptide fragments (peptide IL, IP, and II) were synthesized and subjected to molecular docking and activity analysis. The peptide IL demonstrated the highest affinity for DPP-IV with a binding energy of -8.4 kcal/mol and a moderate IC50 value of 1.431 mg/mL determined based on the Caco-2 cell model. The replacement of specific amino acid residues by Pro and Leu led to an increase in the hydrophobic force interaction between the inhibitor peptide and DPP-IV. The inhibition rates of the three peptides were significantly different (p < 0.05). Peptide II containing an Ile residue instead of Leu resulted in a significant enhancement of DPP-IV inhibitory activity, with an IC50 value of 0.577 mg/mL. The GRAVY changes in the three peptides were consistent with the trend of the inhibitory rates. Therefore, the GRAVY of peptides and branch-chain amino acids should be considered in its activity improvement. The present study revealed the presence and activity of DPP-IV inhibitory peptides in goat milk, providing important insights for further investigation of their potential food functionality and health benefits.

Digestion of whey peptide induces antioxidant and anti-inflammatory bioactivity on glial cells: Sequences identification and structural activity analysis

Whey derived peptides have shown potential activity improving brain function in pathological condition. However, there is little information about their mechanism of action on glial cells, which have important immune functions in brain. Astrocytes and microglia are essential in inflammatory and oxidative defense that take place in neurodegenerative disease. In this work we evaluate antioxidant and anti-inflammatory potential bioactivity of whey peptide in glial cells. Peptides were formed during simulated gastrointestinal digestion (Infogest protocol), and low molecular weight (<5kDA) peptides (WPHf) attenuated reactive oxygen species (ROS) production induced by hydrogen peroxide stimulus in both cells in dose-dependent manner. WPHf induced an increase in the antioxidant glutathione (GSH) content and prevented GSH reduction induced by lipopolysaccharides (LPS) stimulus in astrocytes cells in a cell specific form. An increase in cytokine mRNA expression (TNFα and IL6) and nitric oxide secretion induced by LPS was attenuated by WPHf pre-treatment in both cells. The inflammatory pathway was dependent on NFκB activation. Bioactive peptide ranking analysis showed positive correlation with hydrophobicity and negative correlation with high molecular weights. The sequence identification revealed 19 peptides cross-referred with bioactive database. Whey peptides were rich in leucine, valine and tyrosine in the C-terminal region and lysine in the N-terminal region. The anti-inflammatory and antioxidant potential of whey peptides were assessed in glia cells and its mechanisms of action were related, such as modulation of antioxidant enzymes and anti-inflammatory pathways. Features of the peptide structure, such as molecular size, hydrophobicity and types of amino acids present in the terminal region are associated to bioactivity.

Production and characterization of anti-hypertensive and anti-diabetic peptides from fermented sheep milk with anti-inflammatory activity: in vitro and molecular docking studies

BACKGROUND

The present study aimed to evaluate the anti-hypertensive and anti-diabetic activities from biologically active peptides produced by fermented sheep milk with Lacticaseibacillus paracasei M11 (MG027695), as well as to purify and characterize the angiotensin-converting enzyme (ACE) inhibitory and anti-diabetic peptides produced from fermented sheep milk.

RESULTS

After 48 h of fermentation at 37 °C, sheep milk demonstrated significant changes in anti-diabetic effects and ACE-I effects, with inhibition percentages observed for ACE inhibition (76.32%), α-amylase (70.13%), α-glucosidase (70.11%) and lipase inhibition (68.22%). The highest level of peptides (9.77 mg mL-1) was produced by optimizing the growth conditions, which included an inoculation rate of 2.5% and a 48 h of incubation period. The comparison of molecular weight distributions among protein fractions was conducted through sodium dodecyl-sulfate polyacrylamide gel electrophoresis analysis, whereas spots were separated using 2D gel electrophoresis according to both the molecular weight and pH. Peptide characterization with ultra-filtration membranes at 3 and 10 kDa allowed the study to assess molecular weight-based separation. Nitric oxide generated by lipopolysaccharide and the secretion of pro-inflammatory cytokines in RAW 264.7 immune cells were both inhibited by sheep milk fermented with M11. Fourier-transform infrared spectroscopy was employed to assess changes in functional groups after fermentation, providing insights into the structural changes occurring during fermentation.

CONCLUSION

The present study demonstrates that fermentation with L. paracasei (M11) led to significant changes in fermented sheep milk, enhancing its bioactive properties, notably in terms of ACE inhibition and anti-diabetic activities, and the generation of peptides with bioactive properties has potential health benefits. © 2024 Society of Chemical Industry.

Enzymes for production of whey protein hydrolysates and other value-added products

Whey is a byproduct of dairy industries, the aqueous portion which separates from cheese during the coagulation of milk. It represents approximately 85-95% of milk's volume and retains much of its nutrients, including functional proteins and peptides, lipids, lactose, minerals, and vitamins. Due to its composition, mainly proteins and lactose, it can be considered a raw material for value-added products. Whey-derived products are often used to supplement food, as they have shown several physiological effects on the body. Whey protein hydrolysates are reported to have different activities, including antihypertensive, antioxidant, antithrombotic, opioid, antimicrobial, cytomodulatory, and immuno-modulatory. On the other hand, galactooligosaccharides obtained from lactose can be used as prebiotic for beneficial microorganisms for the human gastrointestinal tract. All these compounds can be obtained through physicochemical, microbial, or enzymatic treatments. Particularly, enzymatic processes have the advantage of being highly selective, more stable than chemical transformations, and less polluting, making that the global enzyme market grow at accelerated rates. The sources and different products associated with the most used enzymes are particularly highlighted in this review. Moreover, we discuss metagenomics as a tool to identify novel proteolytic enzymes, from both cultivable and uncultivable microorganisms, which are expected to have new interesting activities. Finally enzymes for the transformation of whey sugar are reviewed. In this sense, carbozymes with ß-galactosidase activity are capable of lactose hydrolysis, to obtain free monomers, and transgalactosylation for prebiotics production. KEY POINTS: • Whey can be used to obtain value-added products efficiently through enzymatic treatments • Proteases transform whey proteins into biopeptides with physiological activities • Lactose can be transformed into prebiotic compounds using ß-galactosidases.

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.

Mechanistic Study of Novel Dipeptidyl Peptidase IV Inhibitory Peptides from Goat's Milk Based on Peptidomics and In Silico Analysis

Two novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides (YPF and LLLP) were discovered from goat milk protein by peptidomics, in silico analysis, and in vitro assessment. A total of 698 peptides (<23 AA) were successfully identified by LC-MS/MS from goat milk hydrolysates (hydrolyzed by papaian plus proteinase K). Then, 105 potential DPP-IV inhibitory peptides were screened using PeptideRanker, the ToxinPred tool, Libdock, iDPPIV-SCM, and sequence characteristics. After ADME, physicochemical property evaluation, and a literature search, 12 candidates were efficiently selected and synthesized in vitro for functional validation. Two peptides (YPF and LLLP) were found to exert relatively high in vitro chemical system (IC50 = 368.54 ± 12.97 μM and 213.99 ± 0.64 μM) and in situ (IC50 = 159.46 ± 17.40 μM and 154.96 ± 8.41 μM) DPP-IV inhibitory capacities, and their inhibitory mechanisms were further explored by molecular docking. Our study showed that the formation of strong non-bonding interactions with the core residues from the pocket of DPP-IV (such as ARG358, PHE357, GLU205, TYR662, TYR547, and TYR666) might primarily account for the DPP-IV inhibitory activity of two identified peptides. Overall, the two novel DPP-IV inhibitory peptides rapidly identified in this study can be used as functional food ingredients for the control of diabetes.

Revisiting the Multifaceted Therapeutic Potential of Withaferin A (WA), a Novel Steroidal Lactone, W-ferinAmax Ashwagandha, from Withania Somnifera (L) Dunal

Withania somnifera (L.) Dunal, abundant in the Indian subcontinent as Ashwagandha or winter cherry, is a herb of unprecedented therapeutic value. The number of ailments for which crude Ashwagandha extract can be used as a preventive or curative is practically limitless; and this explains why its use has been in vogue in ancient Ayurveda since at-least about four thousand years. The therapeutic potential of Ashwagandha mainly owes from its reservoir of alkaloids (isopelletierine, anaferine), steroidal lactones (withanolides) and saponins with an extra acyl group (sitoindoside VII and VIII). Withaferin A is an exceptionally potent withanolide which is found in high concentrations in W. somnifera plant extracts. The high reactivity of Withaferin A owes to the presence of a C-28 ergostane network with multiple sites of unsaturation and differential oxygenation. It interacts with the effectors of multiple signaling pathways involved in inflammatory response, oxidative stress response, cell cycle regulation and synaptic transmission and has been found to be significantly effective in inducing programmed cell death in cancer cells, restoring cognitive health, managing diabetes, alleviating metabolic disorders, and rejuvenating the overall body homeostasis. Additionally, recent studies suggest that Withaferin A (WA) has the potential to prevent viral endocytosis by sequestering TMPRSS2, the host transmembrane protease, without altering ACE-2 expression. The scope of performing subtle structural modifications in this multi-ring compound is believed to further expand its pharmacotherapeutic horizon. Very recently, a novel, heavy metal and pesticide free formulation of Ashwagandha whole herb extract, with a significant amount of WA, termed W-ferinAmax Ashwagandha, has been developed. The present review attempts to fathom the present and future of this wonder molecule with comprehensive discussion on its therapeutic potential, safety and toxicity.Key teaching pointsWithania somnifera (L.) Dunal is a medicinal plant with versatile therapeutic values.The therapeutic potential of the plant owes to the presence of withanolides such as Withaferin A.Withaferin A is a C-28 ergostane based triterpenoid with multiple reactive sites of therapeutic potential.It is effective against a broad spectrum of ailments including neurodegenerative disorders, cancer, inflammatory and oxidative stress disorders and it also promotes cardiovascular and sexual health.W-ferinAmax Ashwagandha, is a heavy metal and pesticide free Ashwagandha whole herb extract based formulation with significant amount of Withaferin A.

An Update on Dipeptidyl Peptidase-IV Inhibiting Peptides

Diabetes is a chronic metabolic disorder. According to the International Diabetes Federation, about 537 million people are living with diabetes. The two types of diabetes are type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM), among which the population affected by T2DM is relatively higher. A major reason for T2DM is that insulin stimulation is hampered due to the inactivation of incretin hormones. Dipeptidyl peptidase-IV (DPP-IV) is a serine protease that is directly involved in the inactivation of incretin hormones, e.g., glucagon-like peptide-1 (GLP-1). Therefore, the inhibition of DPP-IV can be a promising method for managing T2DM, in addition to other enzyme inhibition strategies, such as inhibition of α-amylase and α -glucosidase. Currently, about 12 different gliptin drugs are available in the market that inhibit DPP-IV in a dose-dependent manner. Instead of gliptins, 'peptides' can also be employed as an alternative and promising way to inhibit DPP-IV. Peptide inhibitors of DPP-IV have been identified from various plants and animals. Chemically synthesized peptides have also been experimented for inhibiting DPP-IV. Most peptides have been analysed by biochemical assays, whereas some in vitro assays have also been reported. Molecular docking analysis has been applied to comprehend the mechanism of inhibition. In this review, certain aspects of natural as well as synthetic peptides are described that have been proven to inhibit DPP-IV.

Selection of goat β-casein derived ACE-inhibitory peptide SQPK and insights into its effect and regulatory mechanism on the function of endothelial cells

The angiotensin I-converting enzyme (ACE)-inhibitory peptide SQPK was selected by in silico digestion and virtual screening from goat β-casein, and its effect and regulatory mechanism on function of endothelial cells was further evaluated. The results showed that SQPK exhibited relatively good ACE inhibition capacity (IC50 = 452.7 μg/mL). Treatment with 25 μg/mL SQPK for 12 h significantly elevated nitric oxide (NO) production, stimulated eNOS expression (p < 0.05) and affected the transcriptomic profiling of EA. Hy926 cells. In particular, SQPK stimulated the expression of genes encoding inflammatory cytokines (CXCL1/2 and IL6) but depressed encoding mesenchymal markers (FN1 and CNN3). Furthermore, SQPK modified the expression of genes involved in endothelial-to-mesenchymal transition (EndMT). Therefore, the selected peptide SQPK may exert potential protective effects on the function of endothelial cells by inhibiting the EndMT.

Preparation, identification, activity prediction, and protective effects on IR-HepG2 cells of five novel DPP-IV inhibitory peptides from protein hydrolysate of skipjack tuna dark muscles

To produce peptides with high dipeptidyl peptidase IV (DPP-IV) inhibitory activity, neutrase was selected from five proteases (trypsin, neutrase, pepsin, alcalase and flavor protease) with the highest degree of hydrolysis (DH) (18.23 ± 1.08%) and DPP-IV inhibitory rate (53.35 ± 4.02%) to produce protein hydrolysate (NPH) from the dark muscles of skipjack tuna (Katsuwonus pelamis). Then, NPH-1 was isolated from NPH by gel permeation chromatography and found to possess the highest DPP-IV inhibitory rate (65.12 ± 7.94% at 0.5 mg ml-1) in the separated components (including NPH-1, NPH-2, NPH-3 and NPH-4). Subsequently, the available prediction models of tripeptides and tetrapeptides with the DPP-IV inhibitory rate were established using an artificial neural network (ANN). The RMSE (0.56 and 0.33 for the model established through collected tripeptides and tetrapeptides, respectively) and R2 (0.95 and 0.99 for the model established through collected tripeptides and tetrapeptides, respectively) of the ANN model's parameters were within acceptable limits, indicating that this model is available. Next, the ANN model was applied to predict tripeptides and tetrapeptides from the hydrolysate of skipjack tuna dark muscles, and five peptides (Ala-Pro-Pro (APP), Pro-Pro-Pro (PPP), Asp-Pro-Leu-Leu (DPLL), Glu-Ala-Val-Pro (EAVP) and Glu-Ala-Iie-Pro (EAIP)) possessing a noticeable DPP-IV inhibitory rate (with DPP-IV IC50 values of 42.46 ± 5.02, 37.71 ± 9.17, 58.85 ± 14.42, 49.94 ± 6.69 and 57.15 ± 6.13 μM, respectively) were screened from the protein hydrolysate. The above five peptides were proved to effectively promote glucose consumption in the insulin resistant-HepG2 (IR-HepG2) cell model considering that the glucose consumption rates of APP, PPP, DPLL, EAVP and EAIP treatment groups are all more than twice that of the dexamethasone group. Accordingly, mechanistic studies showed that these peptides interacted with PI3K/AKT and AMPK signaling pathways and promoted the phosphorylation of PI3K p110, AKT and AMPK (the protein expressions of PI3K p110, p-AKT and p-AMPK in APP, PPP, DPLL, EAVP and EAIP treatment groups are 1.64-2.22 fold compared with that in the dexamethasone group), thereby enhancing glucose uptake and further alleviating insulin resistance. These findings demonstrated that skipjack tuna dark muscle is a potential DPP-IV inhibitory peptide source, and five DPP-IV inhibitory peptides from its hydrolysate may exert potent anti-diabetic activity. In comparison, PPP may be the most potential active ingredient for healthy food against type 2 diabetes mellitus in the five screened peptides considering synthetically the DPP-IV inhibitory rate, bioavailability and synthesis cost.

Dairy products and constituents: a review of their effects on obesity and related metabolic diseases

Obesity has become a global public health problem that seriously affects the quality of life. As an important part of human diet, dairy products contain a large number of nutrients that are essential for maintaining human health, such as proteins, peptides, lipids, vitamins, and minerals. A growing number of epidemiological investigations provide strong evidence on dairy interventions for weight loss in overweight/obese populations. Therefore, this paper outlines the relationship between the consumption of different dairy products and obesity and related metabolic diseases. In addition, we dive into the mechanisms related to the regulation of glucose and lipid metabolism by functional components in dairy products and the interaction with gut microbes. Lastly, the role of dairy products on obesity of children and adolescents is revisited. We conclude that whole dairy products exert more beneficial effect than single milk constituent on alleviating obesity and that dairy matrix has important implications for metabolic health.

Preparation, structural properties, and in vitro and in vivo activities of peptides against dipeptidyl peptidase IV (DPP-IV) and α-glucosidase: a general review

Diabetes is one of the fastest-growing and most widespread diseases worldwide. Approximately 90% of diabetic patients have type 2 diabetes. In 2019, there were about 463 million diabetic patients worldwide. Inhibiting the dipeptidyl peptidase IV (DPP-IV) and α-glucosidase activity is an effective strategy for the treatment of type 2 diabetes. Currently, various anti-diabetic bioactive peptides have been isolated and identified. This review summarizes the preparation methods, structure-effect relationships, molecular binding sites, and effectiveness validation of DPP-IV and α-glucosidase inhibitory peptides in cellular and animal models. The analysis of peptides shows that the DPP-IV inhibitory peptides, containing 2-8 amino acids and having proline, leucine, and valine at their N-terminal and C-terminal, are the highly active peptides. The more active α-glucosidase inhibitory peptides contain 2-9 amino acids and have valine, isoleucine, and proline at the N-terminal and proline, alanine, and serine at the C-terminal.

Production and Characterization of ACE Inhibitory and Anti-Diabetic Peptides from Buffalo and Camel Milk Fermented with Lactobacillus and Yeast: A Comparative Analysis with In Vitro, In Silico, and Molecular Interaction Study

The investigation aimed at assessing a comparative study on the production and characterization of ACE inhibitory, anti-diabetic, and anti-inflammatory activities, along with the production of ACE inhibitory and anti-diabetic peptides through the fermentation of buffalo and camel milk by Limosilactobacillus fermentum (KGL4) and Saccharomyces cerevisiae (WBS2A). The angiotensin-converting enzyme (ACE) inhibitory and anti-diabetic properties were evaluated at particular time intervals (12, 24, 36, and 48 h) at 37 °C, and we discovered maximum activity at 37 °C after 48 h of incubation. The maximum ACE inhibitory, lipase inhibitory activities, alpha-glucosidase inhibitory, and alpha-amylase inhibitory activities were found in the fermented camel milk (77.96 ± 2.61, 73.85 ± 1.19, 85.37 ± 2.15, and 70.86 ± 1.02), as compared to the fermented buffalo milk (FBM) (75.25 ± 1.72, 61.79 ± 2.14, 80.09 ± 0.51, and 67.29 ± 1.75). Proteolytic activity was measured with different inoculation rates (1.5%, 2.0%, and 2.5%) and incubation times (12, 24, 36, and 48 h) to optimize the growth conditions. Maximum proteolysis was found at a 2.5% inoculation rate and at a 48 h incubation period in both fermented buffalo (9.14 ± 0.06) and camel milk (9.10 ± 0.17). SDS-PAGE and 2D gel electrophoresis were conducted for protein purification. The camel and buffalo milk that had not been fermented revealed protein bands ranging from 10 to 100 kDa and 10 to 75 kDa, respectively, whereas all the fermented samples showed bands ranging from 10 to 75 kDa. There were no visible protein bands in the permeates on SDS-PAGE. When fermented buffalo and camel milk were electrophoresed in 2D gel, 15 and 20 protein spots were detected, respectively. The protein spots in the 2D gel electrophoresis ranged in size from 20 to 75 kDa. To distinguish between different peptide fractions, water-soluble extract (WSE) fractions of ultrafiltration (3 and 10 kDa retentate and permeate) of fermented camel and buffalo milk were employed in RP-HPLC (reversed-phase high-performance liquid chromatography). The impact of fermented buffalo and camel milk on inflammation induced by LPS (lipopolysaccharide) was also investigated in the RAW 264.7 cell line. Novel peptide sequences with ACE inhibitory and anti-diabetic properties were also analyzed on the anti-hypertensive database (AHTDB) and bioactive peptide (BIOPEP) database. We found the sequences SCQAQPTTMTR, EMPFPK, TTMPLW, HPHPHLSFMAIPPK, FFNDKIAK, ALPMHIR, IPAVFK, LDQWLCEK, and AVPYPQR from the fermented buffalo milk and the sequences TDVMPQWW, EKTFLLYSCPHR, SSHPYLEQLY, IDSGLYLGSNYITAIR, and FDEFLSQSCAPGSDPR from the fermented camel milk.

In Vitro Assessment Methods for Antidiabetic Peptides from Legumes: A Review

Almost 65% of the human protein supply in the world originates from plants, with legumes being one of the highest contributors, comprising between 20 and 40% of the protein supply. Bioactive peptides from various food sources including legumes have been reported to show efficacy in modulating starch digestion and glucose absorption. This paper will provide a comprehensive review on recent in vitro studies that have been performed on leguminous antidiabetic peptides, focusing on the α-amylase inhibitor, α-glucosidase inhibitor, and dipeptidyl peptidase-IV (DPP-IV) inhibitor. Variations in legume cultivars and methods affect the release of peptides. Different methods have been used, such as in sample preparation, including fermentation (t, T), germination (t), and pre-cooking; in protein extraction, alkaline extraction, isoelectric precipitation, phosphate buffer extraction, and water extraction; in protein hydrolysis enzyme types and combination, enzyme substrate ratio, pH, and time; and in enzyme inhibitory assays, positive control type and concentration, inhibitor or peptide concentration, and the unit of inhibitory activity. The categorization of the relative scale of inhibitory activities among legume samples becomes difficult because of these method differences. Peptide sequences in samples were identified by means of HPLC/MS. Software and online tools were used in bioactivity prediction and computational modelling. The identification of the types and locations of chemical interactions between the inhibitor peptides and enzymes and the type of enzyme inhibition were achieved through computational modelling and enzyme kinetic studies.

Food-derived dipeptidyl peptidase IV inhibitory peptides: Production, identification, structure-activity relationship, and their potential role in glycemic regulation

Dipeptidyl Peptidase IV (DPP-IV) inhibitory peptides are attracting increasing attention, owing to their potential role in glycemic regulation by preventing the inactivation of incretins. However, few reviews have summarized the current understanding of DPP-IV inhibitory peptides and their knowledge gaps. This paper reviews the production, identification and structure-activity relationships (SAR) of DPP-IV inhibitory peptides. Importantly, their bioavailability and hypoglycemic effects are critically discussed. Unlike the traditional method to identifying peptides after separation step by step, the bioinformatics approach identifies peptides via virtual screening that is more convenient and efficient. In addition, the bioinformatics approach was also used to investigate the SAR of peptides. Peptides with proline (Pro) or alanine (Ala) residue at the second position of N-terminal are exhibit strong DPP-IV inhibitory activity. Besides, the bioavailability of DPP-IV inhibitory peptides is related to their gastrointestinal stability and cellular permeability, and in vivo studies showed that the glucose homeostasis has been improved by these peptides. Especially, the intestinal transport of DPP-IV inhibitory peptides and cell biological assays used to evaluate their potential role in glycemic regulation are innovatively summarized. For further successful development of DPP-IV inhibitory peptides in glycemic regulation, future study should elucidate their SAR and in vivo hypoglycemic effects .

Whey protein hydrolysate alleviated atherosclerosis and hepatic steatosis by regulating lipid metabolism in apoE-/- mice fed a Western diet

Whey protein hydrolysate (WPH) has been proved to possess various biological activities associated with the amelioration of cardiovascular disease (CVD). The objective of this study was to investigate the anti-atherosclerotic and hepatoprotective effects of WPH on apolipoprotein E knockout (apoE^-/-) mice fed with a Western diet for 15 weeks. Results revealed that WPH markedly inhibited the development of atherosclerotic lesions in the aorta and steatosis injury in the liver. The serum lipid and inflammation levels were both reduced after WPH supplemented in apoE^-/- mice. In addition, WPH inhibited the lipid accumulation in the liver, thereby decreasing the hepatic inflammation level and oxidative stress injury. Mechanism investigation revealed that WPH down-regulated the expression of cholesterol biosynthesis genes while up-regulated the expression of cholesterol uptake and excretion genes in the liver. Meanwhile, the de novo lipogenesis was inhibited while the fatty acids β-oxidation was activated in the liver by WPH supplementation. Notably, the n-3 polyunsaturated fatty acid (PUFA)/n-6 PUFA ratio in serum and liver of the WPH-H group were 2.69-fold (p < 0.01) and 3.64-fold (p < 0.01) higher than that of the Model group. Collectively, our results proved WPH possesses potent anti-atherosclerotic and hepatoprotective activities and has the potential to be used as a novel functional ingredient for the management of CVD.

Significance of whey protein hydrolysate on anti-oxidative, ACE-inhibitory and anti-inflammatory activities and release of peptides with biofunctionality: an in vitro and in silico approach

The study aimed to investigate potent antioxidant activities (ABTS assay, Hydroxyl free radical scavenging assay, and Superoxide free radical assay), ACE inhibitory activity, and anti-inflammatory activity in the WPC (whey protein concentrate) hydrolysate using Alcalase. The hydrolysis conditions (addition rate and incubation times) for peptide synthesis were also optimized using proteolytic activity. The generation of proinflammatory cytokines by lipopolysaccharide-treated murine macrophages was reduced when the protein hydrolysate concentration was low. In comparison to unhydrolyzed WPC, SDS-PAGE examination revealed no protein bands in WPC hydrolysates. Two-Dimensional (2D) gel electrophoresis did not show any protein spots. Using the 'In-solution trypsin digestion' approach, the trypsin digested protein samples were put into RPLC/MS for amino acid sequencing. Peptides were also identified using RPLC/MS on fractions of 3 and 10 kDa permeates and retentates. The MASCOT database was used to look up the raw masses of LC/MS. By comparing hydrolyzed whey protein to the BLASTp (NCBI), PIR, BIOPEP, and AHTPDB databases, novel antioxidative and ACE inhibitory peptides were reported.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05282-3.

Whey Protein Peptides Have Dual Functions: Bioactivity and Emulsifiers in Oil-In-Water Nanoemulsion

Whey protein isolate (WPI)-derived bioactive peptide fractions (1−3, 3−5, 5−10, 1−10, and >10 kDa) were for the first time used as emulsifiers in nanoemulsions. The formation and storage stability of WPI bioactive peptide-stabilized nanoemulsions depended on the peptide size, enzyme type, peptide concentration, and storage temperature. The highly bioactive <10 kDa fractions were either poorly surface-active or weak stabilizers in nanoemulsions. The moderately bioactive >10 kDa fractions formed stable nanoemulsions (diameter = 174−196 nm); however, their performance was dependent on the peptide concentration (1−4%) and enzyme type. Overall, nanoemulsions exhibited better storage stability (less droplet growth and creaming) when stored at lower (4 °C) than at higher (25 °C) temperatures. This study has shown that by optimizing peptide size using ultrafiltration, enzyme type and emulsification conditions (emulsifier concentration and storage conditions), stable nanoemulsions can be produced using WPI-derived bioactive peptides, demonstrating the dual-functionality of WPI peptides.

Beneficial effects of non-herbal supplements on patients with diabetes

BACKGROUND AND AIMS

Controlling glycemic levels is crucial for patients with diabetes mellitus to improve their disease management and health outcomes. Beyond lifestyle modification and pharmacotherapy, some supplements have been shown to lower blood glucose as well as mitigate diabetic complications.

METHODS

Information was primarily gathered by employing various PubMed scholarly articles for real-world examples in addition to data extraction from supplementary manuscripts. Only original human trials were used, and those published within the past two decades were primarily chosen. However, background information may contains review articles.

RESULTS

Some non-herbal supplements have been suggested to lower fasting blood glucose, postprandial glucose, glycated glucose (HbA1c), lipid profiles, oxidative stress, and inflammation, as well as improving body composition, insulin sensitivity, blood pressure, and nephropathy.

CONCLUSION

This review discusses ten non-herbal supplements that have been reported to have beneficial effects among different types of patients with diabetes as well as potential future clinical application. However, more long-term studies with a larger amount and more diverse participants need to be conducted for a robust conclusion. Also, mechanisms of action of antidiabetic effects are poorly understood and need further research.

Bioactive peptides of whey: obtaining, activity, mechanism of action, and further applications

Bioactive peptides derived from diverse food proteins have been part of diverse investigations. Whey is a rich source of proteins and components related to biological activity. It is known that proteins have effects that promote health benefits. Peptides derived from whey proteins are currently widely studied. These bioactive peptides are amino acid sequences that are encrypted within the first structure of proteins, which required hydrolysis for their release. The hydrolysis could be through in vitro or in vivo enzymatic digestion and using microorganisms in fermented systems. The biological activities associated with bio-peptides include immunomodulatory properties, antibacterial, antihypertensive, antioxidant and opioid, etc. These functions are related to general conditions of health or reduced risk of certain chronic illnesses. To determine the suitability of these peptides/ingredients for applications in food technology, clinical studies are required to evaluate their bioavailability, health claims, and safety of them. This review aimed to describe the biological importance of whey proteins according to the incidence in human health, their role as bioactive peptides source, describing methods, and obtaining technics. In addition, the paper exposes biochemical mechanisms during the activity exerted by biopeptides of whey, and their application trends.

Identification and Characterization of Dipeptidyl Peptidase-IV Inhibitory Peptides from Oat Proteins

In this study, flavourzyme, papain, neutrase, and alcalase, as well as gastrointestinal digestion simulated with pepsin and pancreatin, were used to hydrolyze oat protein, and the dipeptidyl peptidase-IV (DPP-IV) inhibitory activities of the oat protein hydrolysates were investigated. The results indicated that the oat protein hydrolysate by neutrase showed the most potent DPP-IV inhibitory property with an IC50 value of 2.55 ± 0.38 mg/mL. Using UPLC-MS/MS, ten new DPP-IV inhibitory peptides were identified from the oat protein hydrolysate by neutrase. Among these peptides, IPQHY, VPQHY, VAVVPF, and VPLGGF exhibited the strongest DPP-IV inhibitory activity with IC50 values below 50 μM, and all of them acted as mixed-type inhibitors. Molecular docking indicated that the above four oat-derived peptides were predicted to form hydrogen bonds, attractive charge, and hydrophobic interactions with the residues of the active site of DPP-IV. Therefore, our results suggest that oat is an excellent protein source for food-derived DPP-IV inhibitory peptides and it has the prospect of becoming a dietary supplement for T2DM.

Semi-Industrial Production of a DPP-IV and ACE Inhibitory Peptide Fraction from Whey Protein Concentrate Hydrolysate by Electrodialysis with Ultrafiltration Membrane

The separation by electrodialysis with ultrafiltration membranes (EDUF), at a semi-industrial scale, of a new whey protein hydrolysate obtained from a whey protein concentrate was assessed. After 6 h of treatment, more than 9 g of peptides were recovered in the peptide recovery fraction, for a recovery yield of 5.46 ± 0.56% and containing 18 major components. Among these components, positively charged peptides, such as ALPMHIR + PHMIR, LIVTQTMK and TKIPAVF, were present, and their relative abundances increased by nearly 1.25 X and up to 7.55 X. The presence of these peptides may be promising, as ALPMHIR has a strong activity against angiotensin-converting enzyme (ACE), and LIVTQTMK has structural properties that could interfere with dipeptidyl peptidase-IV (DPP-IV). Many neutral peptides were also recovered alongside those. Nevertheless, the inhibitory activity against DPP-IV and ACE increased from 2 X and 4 X, respectively, in the peptide recovery fraction compared to the initial hydrolysate, due to the improved content in bioactive peptides. Thus, this new hydrolysate is well-suited for the large-scale production of a peptide fraction with high bioactivities. Furthermore, what was achieved in this work came close to what could be achieved for the industrial production of a bioactive peptide fraction from whey proteins.

The Influence of Whey Protein Heating Parameters on Their Susceptibility to Digestive Enzymes and the Antidiabetic Activity of Hydrolysates

The inhibition of dipeptidyl peptidase-IV (DPP-IV) and the release of glucagon-like peptide-1 (GLP-1) could normalize blood glucose levels in diabetic patients. This study evaluated the susceptibility of whey proteins to enzyme hydrolysis and the antidiabetic properties of protein hydrolysates from β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) solutions compared with whey protein isolate (WPI) solution treated at different heating temperatures (65, 75, and 85 °C). α-LA hydrolysate provided the lowest degree of hydrolysis (DH). Those heating temperatures did not significantly affect the DH of all protein hydrolysates. α-LA hydrolysate significantly increased GLP-1 levels and DPP-IV inhibitory activity more than β-LG hydrolysate. WPI hydrolysate inhibited DPP-IV activity less than an α-LA hydrolysate, but they were no significant differences for GLP-1 release activity. Heat treatment could affect the antidiabetic properties of all protein hydrolysates. Heating at 75 °C resulted in greater inhibition of the activity of DPP-IV than at 65 and 85 °C. The highest increase in GLP-1 release was also observed by heating at 75 °C. The recently obtained information is useful for the utilization of α-LA, heated at 75 °C for 30 min, in the preparation of antidiabetic food supplements.

Discovery and functional mechanism of novel dipeptidyl peptidase Ⅳ inhibitory peptides from Chinese traditional fermented fish (Chouguiyu)

Dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides from fermented foods exhibit great potential to alleviate type 2 diabetes mellitus (T2DM). In this study, the DPP-IV inhibition activity of peptide extract from Chouguiyu was obviously enhanced after 4–8 d fermentation. A total of 125 DPP-IV inhibitory peptides in Chouguiyu were identified by peptidomics and were obtained from 46 precursor proteins, mainly including nebulin, titin, muscle-type creatine kinase, hemoglobin, and actin. After molecular docking with DPP-IV, four novel DPP-IV inhibitory peptides possessing the lowest docking energy were selected, including EPAEAVGDWR (D37), IPHESVDVIK (D22), PDLSKHNNHM (D35), and PFGNTHNNFK (D1). The DPP-IV inhibition activity of D37, D22, D35, and D1 were further verified after synthesis with the IC₅₀ of 0.10 mM, 2.69 mM, 3.88 mM, and 8.51 mM, respectively, in accordance with their docking energies. Energy interaction showed that the structures of EP-, IPH-, -NHM, and PF- in these peptides were easy to connect with DPP-IV enzyme through hydrogen bond, salt bridge, and alkyl. The surface force including the H-bond interaction, hydrophobicity, aromatic interaction, and SAS, played a major role in the interaction between DPP-IV enzyme and peptides. The peptides that possess high hydrophobicity and can form strong hydrogen bond and salt bridge are potential DPP-IV inhibitory peptides using for T2DM remission.

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DPP-Ⅳ inhibition activity of peptide extract in Chouguiyu increased by fermentation.

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The main precursor proteins of DPP-Ⅳ inhibitory peptides were nebulin and titin.

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Inhibition mechanism was explored by energy interaction and surface force.

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Docking energy was an effective index to select DPP-IV inhibitory peptides.

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DPP-IV inhibitory peptides formed hydrogen bond and salt bridge with DPP-IV.

Exploring the DPP-IV Inhibitory, Antioxidant and Antibacterial Potential of Ovine "Scotta" Hydrolysates

The aim of this work was to valorize the by-product derived from the ricotta cheese process (scotta). In this study, ovine scotta was concentrated by ultrafiltration and then subjected to enzymatic hydrolyses using proteases of both vegetable (4% E:S, 4 h, 50 °C) and animal origin (4% E:S, 4 h, 40 °C). The DPP-IV inhibitory, antioxidant, and antibacterial activities of hydrolysates from bromelain (BSPH) and pancreatin (PSPH) were measured in vitro. Both the obtained hydrolysates showed a significantly higher DPP-IV inhibitory activity compared to the control. In particular, BSPH proved to be more effective than PSPH (IC₅₀ 8.5 ± 0.2 vs. 13 ± 1 mg mL⁻¹). Moreover, BSPH showed the best antioxidant power, while PSPH was more able to produce low-MW peptides. BSPH and PSPH hydrolysates showed a variable but slightly inhibitory effect depending on the species or strain of bacteria tested. BSPH and PSPH samples were separated by gel permeation chromatography (GPC). LC-MS/MS analysis of selected GPC fractions allowed identification of differential peptides. Among the peptides 388 were more abundant in BSPH than in the CTRL groups, 667 were more abundant in the PSPH group compared to CTRL, and 97 and 75 of them contained sequences with a reported biological activity, respectively.

In vitro dipeptidyl peptidase IV inhibitory activity and in situ insulinotropic activity of milk and egg white protein digests

Dietary proteins are involved in the regulation of glucose homeostasis by different mechanisms. Food protein digestion products are reported to inhibit dipeptidyl peptidase IV (DPP-IV), induce incretin secretion or directly exert an insulinotropic effect in pancreatic β-cells. This study illustrates the DPP-IV inhibitory activity of gastric and intestinal digests of casein, whey and egg white proteins determined in vitro, using Gly-Pro-AMC, and in situ using non-differentiated Caco-2 cells. Comparable trends in the DPP-IV inhibitory profiles were obtained by these two methods although the extent of inhibition in situ was consistently lower than the inhibition observed in vitro. Casein intestinal digests and whey protein gastric and intestinal digests showed potent DPP-IV inhibitory activities in Caco-2 cells with IC₅₀ values ranging from 0.8 to 1.2 mg mL^-1. The absorbed fraction of the intestinal digests from whey and egg white protein induced insulin secretion in BRIN-BD11 cells when determined using a two-tiered cellular model (Caco-2 and BRIN-BD11). However, the gastric digests from the same substrates showed no insulin secretion. This may be related to limited trans-epithelial transport through the Caco-2 monolayer of the gastric digestion products. However, both, gastric and intestinal digests were able to induce insulin secretion in BRIN-BD11 cells when the monolayer was composed of a co-culture of STC-1 and Caco-2 cells. This result may be attributed to the activation of STC-1 cells and subsequent incretin secretion, induced by the gastric digest, as shown by an enhanced intracellular calcium uptake.

Effect of two-step enzymatic hydrolysis on the antioxidant properties and proteomics of hydrolysates of milk protein concentrate

Food protein and peptides are generally considered a source of dietary antioxidants. The antioxidant activity and peptide profiles of four extensive hydrolysates of milk protein concentrate (MPC) were examined using the two-step enzymatic method. The hydrolysis combinations were Alcalase-Flavourzyme (AE), Alcalase-ProteAXH (AH), Alcalase-Protamex (AX) and Alcalase-Protease A 2SD (AD). The results showed that highest degree of hydrolysis corresponded to the AE sample (20.41%). High-efficiency gel-filtration chromatography results indicated that the relative proportions of extensive hydrolysates with molecular weights < 3 kDa were 99.89%, 99.57%, 99.93%, and 99.89% for AX, AE, AD and AH, respectively. The hydrolysates of the MPC exhibited increased radical-scavenging capacity, as evidenced through an analysis with 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS), reducing power and hydroxyl-radical scavenging activity testing. The main bioactive peptides were identified through EASY-nLC-orbitrap MS/MS and bioinformatics. The study may provide useful information regarding the antioxidant properties of extensive hydrolysates of MPC.

Dipeptidyl Peptidase (DPP)-IV Inhibitors with Antioxidant Potential Isolated from Natural Sources: A Novel Approach for the Management of Diabetes

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia that is predominantly caused by insulin resistance or impaired insulin secretion, along with disturbances in carbohydrate, fat and protein metabolism. Various therapeutic approaches have been used to treat diabetes, including improvement of insulin sensitivity, inhibition of gluconeogenesis, and decreasing glucose absorption from the intestines. Recently, a novel approach has emerged using dipeptidyl peptidase-IV (DPP-IV) inhibitors as a possible agent for the treatment of T2DM without producing any side effects, such as hypoglycemia and exhaustion of pancreatic β-cells. DPP-IV inhibitors improve hyperglycemic conditions by stabilizing the postprandial level of gut hormones such as glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptides, which function as incretins to help upregulate insulin secretion and β-cell mass. In this review, we summarized DPP-IV inhibitors and their mechanism of inhibition, activities of those isolated from various natural sources, and their capacity to overcome oxidative stress in disease conditions.

Nutritional, antimicrobial and medicinal properties of Camel's milk: A review

Camel's milk is an important part of staple diet in several parts of the world, particularly in the arid and semi-arid zones. Camel's milk is rich in health-beneficial substances, such as bioactive peptides, lactoferrin, zinc, and mono and polyunsaturated fatty acids. These substances could help in the treatment of some important human diseases like tuberculosis, asthma, gastrointestinal diseases, and jaundice. Camel's milk composition is more variable compared to cow's milk. The effects of feed, breed, age, and lactation stage on milk composition are more significant in camel. Region and season significantly change the ratio of compounds in camel's milk. Camel's whey protein is not only composed of numerous soluble proteins, but also has indigenous proteases such as chymotrypsin A and cathepsin D. In addition to their high nutritional value, these whey proteins have unique characteristics, including physical, chemical, physiological, functional, and technological features that are useful in the food application. The hydrolysis of camel's milk proteins leads to the formation of bioactive peptides, which affect major organ systems of the body and impart physiological functions to these systems. The camel's milk has antioxidant, antimicrobial, angiotensin-I-converting enzyme (ACE)-inhibitory peptides, antidiabetic as well as anticholesterol activities.

Protease Inhibitors Purified from the Canola Meal Extracts of Two Genetically Diverse Genotypes Exhibit Antidiabetic and Antihypertension Properties

Valorization of vegetable oil waste residues is gaining importance due to their high protein and polyphenol contents. Protease inhibitors (PIs), proteins from these abundantly available waste residues, have recently gained importance in treating chronic diseases. This research aimed to use canola meal of genetically diverse Brassica napus genotypes, BLN-3347 and Rivette, to identify PIs with diverse functionalities in therapeutic and pharmacological applications. The canola meal PI purification steps involved: native PAGE and trypsin inhibition activity, followed by ammonium sulfate fractionation, anion exchange, gel filtration, and reverse-phase chromatography. The purified PI preparations were characterized using SDS-PAGE, isoelectric focusing (IEF), and N terminal sequencing. SDS-PAGE analysis of PI preparations under native reducing and nonreducing conditions revealed three polymorphic PIs in each genotype. The corresponding IEF of the genotype BLN-3347, exhibited three acidic isoforms with isoelectric points (pI) of 4.6, 4.0, and 3.9, while Rivette possessed three isoforms, exhibiting two basic forms of pI 8.65 and 9.9, and one acidic of pI 6.55. Purified PI preparations from both the genotypes displayed dipeptidyl peptidase-IV (DPP-IV) and angiotensin-converting enzyme (ACE) inhibition activities; the BLN-3347 PI preparation exhibited a strong inhibitory effect with lower IC₅₀ values (DPP-IV 37.42 µg/mL; ACE 129 µg/mL) than that from Rivette (DPP-IV 67.97 µg/mL; ACE 376.2 µg/mL). In addition to potential human therapy, these highly polymorphic PIs, which can inhibit damaging serine proteases secreted by canola plant pathogens, have the potential to be used by canola plant breeders to seek qualitative trait locus (QTLs) linked to genes conferring resistance to canola diseases.