Angiotensin I-converting enzyme inhibitory properties of whey protein digests: concentration and characterization of active peptides

An Integrated Comprehensive Peptidomics and In Silico Analysis of Bioactive Peptide-Rich Milk Fermented by Three Autochthonous Cocci Strains

Bioactive peptides (BPs) are molecules of paramount importance with great potential for the development of functional foods, nutraceuticals or therapeutics for the prevention or treatment of various diseases. A functional BP-rich dairy product was produced by lyophilisation of bovine milk fermented by the autochthonous strains Lactococcus lactis subsp. lactis ZGBP5-51, Enterococcus faecium ZGBP5-52 and Enterococcus faecalis ZGBP5-53 isolated from the same artisanal fresh cheese. The efficiency of the proteolytic system of the implemented strains in the production of BPs was confirmed by a combined high-throughput mass spectrometry (MS)-based peptidome profiling and an in silico approach. First, peptides released by microbial fermentation were identified via a non-targeted peptide analysis (NTA) comprising reversed-phase nano-liquid chromatography (RP nano-LC) coupled with matrix-assisted laser desorption/ionisation-time-of-flight/time-of-flight (MALDI-TOF/TOF) MS, and then quantified by targeted peptide analysis (TA) involving RP ultrahigh-performance LC (RP-UHPLC) coupled with triple-quadrupole MS (QQQ-MS). A combined database and literature search revealed that 10 of the 25 peptides identified in this work have bioactive properties described in the literature. Finally, by combining the output of MS-based peptidome profiling with in silico bioactivity prediction tools, three peptides (75QFLPYPYYAKPA86, 40VAPFPEVFGK49, 117ARHPHPHLSF126), whose bioactive properties have not been previously reported in the literature, were identified as potential BP candidates.

Ahrné L, Cardoso DR. UV-C light promotes the reductive cleavage of disulfide bonds in β-Lactoglobulin and improves in vitro gastric digestion

β-Lactoglobulin (β-Lg) is the main protein in whey and is known for its allergenicity and resistance to the digestion of pepsin and trypsin. The UV-C photoinduced cleavage of disulfide bonds in β-Lactoglobulin, as promoted by excitation of tryptophan residues (Trp), is shown to induce changes in the protein's secondary structure, significantly reducing the protein's resistance to pepsin digestion. The UV-C light-induced changes in the protein secondary structure are marked by an increase in the contribution of β-sheet and α-helix structures with a concomitantly smaller contribution of the β-turn structural motif. The photoinduced cleavage of disulfide bonds in β-Lg has an apparent quantum yield of ф = 0.0015 ± 0.0003 and was shown by transient absorption laser flash photolysis to arise by two different pathways: a) the reduction of the disulfide bond Cys₆₆Cys₁₆₀ occurs by direct electron transfer from the triplet-excited ³Trp to the disulfide bond due to the existence of a CysCys/Trp triad (Cys₆₆Cys₁₆₀/Trp₆₁) and b) the reduction of the buried Cys₁₀₆Cys₁₁₉ disulfide bond involves a reaction with a solvated electron originated by the photoejection of electrons from the triplet-excited ³Trp decay. The in vitro gastric digestion index for UV-C-treated β-Lg is revealed to have increased significantly by 36 ± 4 % and 9 ± 2 % under simulated elderly and young adult digestive conditions, respectively. When compared to the native protein, the peptide mass fingerprint profile of digested UV-C-treated β-Lg shows a higher content and variety of peptides, including the production of some exclusive bioactive peptides such as PMHIRL and EKFDKALKALPMH.

Higher Intake of Dairy Is Associated with Lower Cardiometabolic Risks and Metabolic Syndrome in Asian Indians

There is conflicting evidence about the association between dairy products and cardiometabolic risk (CMR). We aimed to assess the association of total dairy intake with CMR factors and to investigate the association of unfermented and fermented dairy intake with CMR in Asian Indians who are known to have greater susceptibility to type 2 diabetes and cardiovascular diseases compared to white Europeans. The study comprised 1033 Asian Indian adults with normal glucose tolerance chosen from the Chennai Urban Rural Epidemiological Study (CURES). Dietary intake was assessed using a validated open-ended semi-quantitative food frequency questionnaire. Metabolic syndrome (MS) was diagnosed based on the new harmonising criteria using central obesity, dyslipidaemia [low high-density lipoprotein cholesterol (HDL) and increased serum triglycerides (TG)], hypertension and glucose intolerance. Increased consumption of dairy (≥5 cups per day of total, ≥4 cups per day of unfermented or ≥2 cups per day of fermented dairy) was associated with a lower risk of high fasting plasma glucose (FPG) [hazards ratio (HR), 95% confidence interval (CI): 0.68, 0.48−0.96 for total dairy; 0.57, 0.34−0.94 for unfermented dairy; and 0.64, 0.46−0.90 for fermented dairy; p < 0.05 for all] compared to a low dairy intake (≤1.4 cups per day of total dairy; ≤1 cup per day of unfermented dairy; and ≤0.1 cup per day of fermented dairy). A total dairy intake of ≥5 cups per day was also protective against high blood pressure (BP) (HR: 0.65, 95% CI: 0.43−0.99, p < 0.05), low HDL (HR: 0.63, 95% CI: 0.43−0.92, p < 0.05) and MS (HR: 0.71, 95% CI: 0.51−0.98, p < 0.05) compared to an intake of ≤1.4 cups per day. A high unfermented dairy intake (≥4 cups per day) was also associated with a lower risk of high body mass index (BMI) (HR: 0.52, 95% CI: 0.31−0.88, p < 0.05) compared to a low intake (≤1 cup per day), while a reduced risk of MS was observed with a fermented dairy intake of ≥2 cups per day (HR: 0.71, 95% CI: 0.51−0.98, p < 0.05) compared to an intake of ≤0.1 cup per day. In summary, increased consumption of dairy was associated with a lower risk of MS and components of CMR.

Manufacture of Whey Protein Hydrolysates Using Plant Enzymes: Effect of Processing Conditions and Simulated Gastrointestinal Digestion on Angiotensin-I-Converting Enzyme (ACE) Inhibitory Activity

Hydrolysis of proteins leads to the release of bioactive peptides with positive impact on human health. Peptides exhibiting antihypertensive properties (i.e., inhibition of angiotensin-I-converting enzyme) are commonly found in whey protein hydrolysates made with enzymes of animal, plant or microbial origin. However, bioactive properties can be influenced by processing conditions and gastrointestinal digestion. In this study, we evaluated the impact of three plant enzymes (papain, bromelain and ficin) in the manufacture of whey protein hydrolysates with varying level of pH, enzyme-to-substrate ratio and time of hydrolysis, based on a central composite design, to determine the degree of hydrolysis and antihypertensive properties. Hydrolysates made on laboratory scales showed great variation in the type of enzyme used, their concentrations and the pH level of hydrolysis. However, low degrees of hydrolysis in papain and bromelain treatments were associated with increased antihypertensive properties, when compared to ficin. Simulated gastrointestinal digestion performed for selected hydrolysates showed an increase in antihypertensive properties of hydrolysates made with papain and bromelain, which was probably caused by further release of peptides. Several peptides with reported antihypertensive properties were found in all treatments. These results suggest plant enzymes used in this study can be suitable candidates to develop ingredients with bioactive properties.

Positive Effects of α-Lactalbumin in the Management of Symptoms of Polycystic Ovary Syndrome

To date, the involvement of α-Lactalbumin (α-LA) in the management of polycystic ovary syndrome (PCOS) refers to its ability to improve intestinal absorption of natural molecules like inositols, overcoming the inositol resistance. However, due to its own aminoacidic building blocks, α-LA is involved in various biological processes that can open new additional applications. A great portion of women with PCOS exhibit gastrointestinal dysbiosis, which is in turn one of the triggering mechanisms of the syndrome. Due to its prebiotic effect, α-LA can recover dysbiosis, also improving the insulin resistance, obesity and intestinal inflammation frequently associated with PCOS. Further observations suggest that altered gut microbiota negatively influence mental wellbeing. Depressive mood and low serotonin levels are indeed common features of women with PCOS. Thanks to its content of tryptophan, which is the precursor of serotonin, and considering the strict link between gut and brain, using α-LA contributes to preserving mental well-being by maintaining high levels of serotonin. In addition, considering women with PCOS seeking pregnancy, both altered microbiota and serotonin levels can induce later consequences in the offspring. Therefore, a deeper knowledge of potential applications of α-LA is required to transition to preclinical and clinical studies extending its therapeutic advantages in PCOS.

Whey Protein Hydrolysates of Sheep/Goat Origin Produced by the Action of Trypsin without pH Control: Degree of Hydrolysis, Antihypertensive Potential and Antioxidant Activities

Tryptic WPHs with considerable residual whey protein content intact were developed from two sheep/goat WPCs (65% and 80% protein) without pH control. Pasteurization was used to avoid denaturation. Changes in non-protein nitrogen (DH_TCASN), free amino groups (DH_TNBS), and major whey proteins were used to investigate the degree and extent of hydrolysis. Antihypertensive potential (ACE-IA), radical scavenging (DPPH-RSA), and iron chelation (Fe-CA) were assessed. No statistically significant changes in pH (5.84−6.29) were observed during hydrolysis and storage. At the start of hydrolysis, DH_TCASN was ≅11% for both substrates whereas DH_TNBS was >10% and >5% for WP65 and WP80, respectively. After one-hour hydrolysis, DH_TCASN was ≅17% for both substrates and DH_TNBS was ≅15% and ≅11% for WP65 and WP80, respectively. The β-lactoglobulin, α-lactalbumin, and caseinomacropeptide of WP65 were hydrolyzed by 14 ± 1.3%, 73.9 ± 2.6% and 37 ± 2.6%. The respective values for WP80 were 14.9 ± 1.7%, 79.9 ± 1%, and 32.7 ± 4.8%. ACE-IA of the hydrolysates of both substrates was much higher (>80%) than that of controls (<10%). Hydrolysis, substrate type, and storage did not affect the DPPH-RSA (45−54%). Fe-CA of the WP65 and WP80 hydrolysates were ≅40% and ≅20%, respectively; a similar outcome was found in the respective controls. Refrigerated storage for 17 h did not affect the degree of hydrolysis and biofunctional activities.

Angiotensin-I-Converting Enzyme Inhibitory Activity of Protein Hydrolysates Generated from the Macroalga Laminaria digitata (Hudson) JV Lamouroux 1813

Seaweeds have a long history of use as both food and medicine, especially in Asian cultures. Moreover, there is growing interest in the use of seaweed ingredients and bioactive compounds in pharmaceutical and nutraceutical products. One ailment that seaweed bioactive compounds may impact is hypertension caused by the enzyme Angiotensin Converting Enzyme 1 (ACE-1; EC 3.4.15.1), found within the Renin-Angiotensin Aldosterone System (RAAS), which causes vasoconstriction of blood vessels, including veins and arteries. The aim of this paper is to generate bioactive peptide containing protein hydrolysates from the brown seaweed Laminaria digitata (Hudson) JV Lamouroux 1813. Proteins were extracted from this seaweed by disrupting the seaweed cell wall using a combination of carbohydrases and proteolytic enzymes. Bioactive peptide containing permeates were generated from L. digitata protein hydrolysates, and both hydrolysates and permeates were screened for their ability to inhibit the enzyme ACE-1. The protein content of the permeate fractions was found to be 23.87% compared to the untreated seaweed, which contained 15.08% protein using LECO analysis. Hydrolysis and filtration resulted in a “white” protein powder, and the protein content of this powder increased by 9% compared to the whole seaweed. The total amino acid (TAA) content of the L. digitata protein permeate was 53.65 g/100 g of the sample, and contains over 32% essential amino acids (EAA). Furthermore, the L. digitata permeate was found to inhibit the ACE-1 enzyme by 75% when compared to the commercial drug Captopril© when assayed at a concentration of 1 mg/mL. The inhibition of ACE-1 (the IC₅₀ value) of 590 µg/mL for the L. digitata permeate compares well with Captopril©, which had 100% inhibition of ACE-1, with an IC₅₀ value of 500 µg/mL. This study indicates that there is potential to develop protein powders with ACE-1 inhibitory bioactivities from the brown seaweed L. digitata using enzymatic hydrolysis as a cell disruption and protein extraction/hydrolysate generation procedure.

Development and sensory test of a dairy product with ACE inhibitory and antioxidant peptides produced at a pilot plant scale

A scale-up process was carried out to obtain potent bioactive peptides from whey protein through a simple hydrolysis process. The scale-up was satisfactory, with results similar to those obtained at lab scale: a fraction of peptides < 1 kDa with ACE inhibitory activity of 18.44 ± 2.47 μg/mL, a DPPH value of 69.40 ± 0.44%, and an ORAC value of 3.37 ± 0.03 μmol TE/mg protein. The peptide sequences responsible for the ACE inhibitory activity were also similar to those identified at lab scale: PM, LL, LF, HFKG and PT. The hydrolysate was used as a functional ingredient in a low-fat yoghurt. The consumer sensory taste panel found no significant difference (p > 0.05) between the bitterness of the control and the functional yoghurt, and about 50% of consumers would buy it. The hydrolysate maintained its bioactivities for 4 months at -20 °C (after thawing and pasteurisation), and for 1 week in yoghurt at 4 °C.

Conventional and Novel Technologies in the Production of Dairy Bioactive Peptides

Background

In recent years, researchers have focused on functional ingredients, functional foods, and nutraceuticals due to the rapidly increasing interest in bioactive components, especially in bioactive peptides. Dairy proteins are a rich and balanced source of amino acids and their derived bioactive peptides, which possess biological and physiological properties. In the dairy industry, microbial fermentation and enzymatic hydrolysis are promising methods for producing bioactive peptides because of their rapid efficiency, and mild reaction conditions. However, these methods utilize less raw material, take long reaction time, result in low yields, and low activity products when used alone, which pose industry to seek for novel methods as pretreatments to increase the yield of bioactive peptides.

Scope and Approach

This review emphasizes the production of peptides from the dairy proteins and discusses the potential use of novel technologies as pretreatments to conventional methods of bioactive peptides production from dairy proteins, including the mechanisms of novel technologies along with respective examples of use, advantages, limitations, and challenges to each technology.

Key Findings and Conclusion

Noteworthily, hydrolysis of dairy proteins liberate wide-range of peptides that possess remarkable biological functions to maintain human health. Novel technologies in the dairy industry such as ultrasound-assisted processing (UAP), microwave-assisted processing (MAP), and high pressure processing (HPP) are innovative and environmentally friendly. Generally, novel technologies are less effectual compared to conventional methods, therefore used in combination with fermentation and enzymatic hydrolysis, and are promising pretreatments to modify peptides’ profile, improve the yields, and high liberation of bioactive peptides as compared to conventional technologies. UAP is an innovative and most efficient technology as its mechanical effects and cavitation change the protein conformation, increase the biological activities of enzymes, and enhance enzymatic hydrolysis reaction rate.

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.

Antioxidant and Antimicrobial Peptides Derived from Food Proteins

Recently, the demand for food proteins in the market has increased due to a rise in degenerative illnesses that are associated with the excessive production of free radicals and the unwanted side effects of various drugs, for which researchers have suggested diets rich in bioactive compounds. Some of the functional compounds present in foods are antioxidant and antimicrobial peptides, which are used to produce foods that promote health and to reduce the consumption of antibiotics. These peptides have been obtained from various sources of proteins, such as foods and agri-food by-products, via enzymatic hydrolysis and microbial fermentation. Peptides with antioxidant properties exert effective metal ion (Fe2+/Cu2+) chelating activity and lipid peroxidation inhibition, which may lead to notably beneficial effects in promoting human health and food processing. Antimicrobial peptides are small oligo-peptides generally containing from 10 to 100 amino acids, with a net positive charge and an amphipathic structure; they are the most important components of the antibacterial defense of organisms at almost all levels of life-bacteria, fungi, plants, amphibians, insects, birds and mammals-and have been suggested as natural compounds that neutralize the toxicity of reactive oxygen species generated by antibiotics and the stress generated by various exogenous sources. This review discusses what antioxidant and antimicrobial peptides are, their source, production, some bioinformatics tools used for their obtainment, emerging technologies, and health benefits.

Antihypertensive activity of orally consumed ACE-I inhibitory peptides

Food proteins are sources for ACE-I inhibitory peptides that can be extracted by enzymatic hydrolysis exhibiting anti-hypertensive activity. However, these peptides are prone to further degradation by gastrointestinal enzymes during oral consumption. Bio-activity of these peptides is dependent on the resultant peptide post gastrointestinal digestion. To exhibit the bio-activity, they need to be absorbed in intact form. Although studies suggest di and tri-peptides show better ACE-I inhibitory activity, few peptides show altered IC₅₀ values under simulated gastrointestinal digestion. Moreover, ACE-I inhibitory peptides with low IC₅₀ values have not shown effective anti-hypertensive activity in spontaneously hypertensive rats when administered orally. Few ACE-I inhibitory peptides have reported effective reduction in systolic blood-pressure when administered through intravenously. During oral consumption of such peptides, the actual peptide sequence responsible for reducing blood-pressure is a result of breakdown in gastrointestinal tract. The fate of targeted peptides during digestion depends on amino acid sequence of the protein containing the specific site for cleavage where the action of digestive enzymes takes place. Therefore, this review attempts to explain the factors that affect the anti-hypertensive activity of ACE-I inhibitory peptides during oral consumption. It also highlights subsequent absorption of ACE-I inhibitory peptides after gastrointestinal digestion.

Bioactive Peptides from Liquid Milk Protein Concentrate by Sequential Tryptic and Microbial Hydrolysis

Recently, bioactive peptides as a health-promoting agent have come to the forefront of health research; however, industrial production is limited, possibly due to the lack of the required technological knowledge. The objective of the investigation was to prepare bioactive peptides with hypoallergenic properties from liquid milk protein concentrate (LMPC), through sequential enzymatic and microbial hydrolysis. LMPC was produced from ultra-heat-treated (UHT) skimmed cow’s milk using a nanofiltration membrane. The effect of the concentration of trypsin (0.008–0.032 g·L−1) on the hydrolysis of LMPC was studied. Subsequently, the hydrolysis of tryptic-hydrolyzed LMPC (LMPC-T) with lactic acid bacteria was performed, and the effect of glucose in microbial hydrolysis was studied. Aquaphotomic analysis of the hydrolysis of LMPC was performed using the spectral range of 1300–1600 nm (near-infrared spectra). Changes in antioxidant capacity, anti-angiotensin-converting enzyme activity, and antibacterial activity against Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes were noted after the sequential tryptic and microbial hydrolysis of LMPC. Allergenicity in LMPC was reduced, due to sequential hydrolysis with 0.016 g·L−1 of trypsin and lacteal acid bacteria. According to the aquaphotomic analysis result, there was a dissociation of hydrogen bonds in compounds during the initial period of fermentation and, subsequently, the formation of compounds with hydrogen bonds. The formation of compounds with a hydrogen bond was more noticeable when microbial hydrolysis was performed with glucose. This may support the belief that the results of the present investigation will be useful to scale up the process in the food and biopharmaceutical industries.

Potential applications of ficin in the production of traditional cheeses and protein hydrolysates

Using proteolytic enzymes extracted from plant materials is a promising way to ensure the sustainability of the food industry. This is particularly true for the dairy industry, especially in cheesemaking and the production of different milk protein hydrolysates for special food applications, particularly nutrition for infants, older adults, and people with food allergies. Ficin, a cysteyl protease isolated from the latex of the fig tree (Ficus carica), is characterized by strong enzymatic activity and can be used for milk clotting and protein hydrolysis for application in different foods. In particular, it can be used for milk protein hydrolysis to produce ingredients with reduced or eliminated allergenicity and improved bioavailability. Ficin can also be used as an active and effective replacement for calf rennet in cheesemaking, such as in traditional Cacioricotta and Teleme cheeses. It can also be used to produce protein hydrolysates with low or no allergenicity for application in infant formula and geriatric nutrition. This work provides an overview of ficin, a plant-derived protease, with an emphasis on its potential application in the production of some traditional cheeses and milk protein hydrolysates for special food applications.

Production of whey protein hydrolyzates and its incorporation into milk

Abstract

Whey proteins provide an excellent source of low-molecular-weight bioactive peptides with important functional properties and bioactivities like antihypertensive, opioid, and antimicrobial effects. Presence of peptide molecules with lower molecular weight has a great role in food for health promotion. In this investigation, the release of low-molecular-weight peptides from whey protein concentrate was attempted by using enzymatic digestion. The hydrolyzate was then incorporated into milk to obtain enriched milk (EM) with low-molecular-weight peptides. Based on sensory analysis of EM, electrophoretic and RP-HPLC studies, hydrolyzates of 10% protein (degree of hydrolysis 5%; enzyme/ substrate E/S, 1:50) were finally incorporated into milk at 20% (v/v) to develop an acceptable product enriched with low-molecular-weight peptides. EM had higher protein content, viscosity and emulsifying properties than control milk with 3% fat. It is recommended that EM should not be sterilized as it results in coagulation, but can be safely pasteurized and spray dried without any undesirable effects. Maximum ACE-inhibition activity was obtained in hydrolyzate, followed by EM. This study is expected to boost the opportunity for the dairy industry to venture further into the nutraceutical dairy market.

Graphical abstract

Dual-enzyme hydrolysis for preparation of ACE-inhibitory peptides from sesame seed protein: Optimization, separation, and identification

To prepare and identify ACE-inhibitory peptides originated from sesame seed protein, peptides with strong ACE-inhibitory activities were obtained via the optimization of protease and hydrolysis conditions, and these peptides were purified and identified by membrane separation, gel filtration, and liquid chromatography-mass spectrometry. Results showed that the dual-enzyme comprised alcalase and trypsin with the enzyme activity ratio of 3:7 was suitable to produce ACE-inhibitory peptides. The highest ACE-inhibitory activity of 98.10 ± 0.26% was obtained at the following parameters, pH 8.35, E/S ratio of 6,145 U/g, and hydrolysis time of 4.4 hr. ISGAQPSLR and VVISAPSK ranked the first and second ACE-inhibitory activity among 15 identified ACE-inhibitory peptides. Both peptides influenced ACE via binding with the S1 pocket, S2 pocket, and Zn²⁺ ion. ISGAQPSLR even impacted the S1' pocket. ISGAQPSLR and VVISAPSK acted as a competitive and noncompetitive inhibitor, respectively. ACE-inhibitory peptides derivated from sesame seed protein have potential applications in functional food. PRACTICAL APPLICATIONS: Although sesame seed protein is proven as the precursor of ACE-inhibitory peptide, preparing ACE-inhibitory peptide from sesame seed protein is still suffering from insufficient information on hydrolysis condition and the peptide sequence. Therefore, the performance of the typical protease on preparing ACE-inhibitory peptide from sesame seed protein has been evaluated, the effect of the amino acid composition of sesame seed protein and cleavage specificity of protease on the generation of ACE-inhibitory peptide has been investigated, hydrolysis conditions have been optimized, the peptide sequence has been identified to illuminate the effect of sesame seed protein fraction on the formation of ACE-inhibitory peptide and discuss the structural characteristics. ACE-inhibitory peptides originating from sesame seed protein could apply in functional food. It is promising for dual-enzyme hydrolysis to utilize in preparation of high-value bioactive peptides.

Thermal or membrane processing for Infant Milk Formula: Effects on protein digestion and integrity of the intestinal barrier

Infant Milk Formula (IMF) is designed as a breastmilk substitute to satisfy the nutritional requirements during the first months of life. This study investigates the effects of two IMF processing technologies on cow milk protein digestion using an infant static in vitro gastrointestinal model. The degree of protein hydrolysis at the end of the gastric phase was 3.7-fold higher for IMF produced by high temperature (IMF-HT), compared to IMF produced by cascade membrane filtration (IMF-CMF), as assessed by free N-terminal group analysis. The processing type also influenced the panel of bioavailable peptides detected in basolateral compartments of Caco-2 monolayers exposed to gastrointestinal digested IMFs. In addition, IMF-CMF significantly increased tight junction protein, claudin 1, whilst IMF-HT significantly reduced tight junction integrity. In conclusion, producing IMF by CMF may preserve intestinal barrier integrity and can deliver its own unique inventory of bioavailable peptides with potential bioactivity.

Development of Antioxidant and Antihypertensive Properties during Growth of Lactobacillus helveticus, Lactobacillus rhamnosus and Lactobacillus reuteri on Cow's Milk: Fermentation and Peptidomics Study

Bioactive peptides derived from milk proteins are an active research area. Exhibiting numerous positive physiological effects on digestive, cardiovascular, immune and nervous systems, these peptides thought to be one of the most promising ingredients for functional food. Generally, these peptides are inactive within the parent proteins and can be liberated during milk fermentation by the specific proteolytic systems of various Lactobacillus spp. Here we present the study of milk fermentation by Lactobacillus helveticus NK1, Lactobacillus rhamnosus F and Lactobacillus reuteri LR1 strains. It was demonstrated that the antioxidant activity of the milk fermented by these strains concomitantly increased with the strains’ proteolytic activity. For the angiotensin I-converting enzyme (ACE) inhibitory activity, the same tendency was not observed. Although the proteolytic activity of L. helveticus NK1 was two times higher than that of L. rhamnosus F, the milk fermented by these strains showed comparable ACE inhibition. The analysis of the peptide profiles of the fermented milk samples allowed us to hypothesize that some previously unreported peptides can be produced by L. rhamnosus F. In addition, it was demonstrated that these potential ACE-inhibiting peptides originated from the C-terminus of α_S2-casein.

Addition of Anionic Polysaccharide Stabilizers Modulates In Vitro Digestive Proteolysis of a Chocolate Milk Drink in Adults and Children

There is a need to better understand the possible anti-nutritional effect of food stabilizers on the digestibility of important macronutrients, like proteins. This study hypothesized that the anionic nature of κ-, ι-, λ-, Carrageenan (CGN) and xanthan gum directs their interactions with food proteins leading to their subsequent attenuated digestive proteolysis. Model chocolate milk drinks were tested for their colloidal properties, viscosity and proteolytic breakdown in adults and children using in vitro digestion models coupled with proteomic analyses. SDS-PAGE analyses of gastro-intestinal effluents highlight stabilizers hinder protein breakdown in adults and children. Zeta potential and colloidal particle size were the strongest determinants of stabilizers’ ability to hinder proteolysis. LC-MS proteomic analyses revealed stabilizer addition significantly reduced bioaccessibility of milk-derived bioactive peptides with differences in liberated peptide sequences arising mainly from their location on the outer rim of the protein structures. Further, liberation of bioactive peptides emptying from a child stomach into the intestine were most affected by the presence of ι-CGN. Overall, this study raises the notion that stabilizer charge and other properties of edible proteins are detrimental to the ability of humans to utilize the nutritional potential of such formulations. This could help food professionals and regulatory agencies carefully consider the use of anionic stabilizers in products aiming to serve as protein sources for children and other liable populations.

High protein yogurt with addition of Lactobacillus helveticus: Peptide profile and angiotensin-converting enzyme ACE-inhibitory activity

In order to evaluate differences in the peptide profile and bioactive potential in dairy products, by increasing the protein content and using proteolytic bacteria strain to enable the release of bioactive peptides, a high-protein yogurt with adjunct culture was developed. The effect of protein content, the addition of Lactobacillus helveticus LH-B02, and storage time were evaluated. The qualitative analysis of peptide profile was performed using a mass spectrometry approach (MALDI-ToF-MS), and the potential bioactivity evaluated by ACE inhibition activity. Protein content did not affect the peptide profile in yogurts, and the addition of Lactobacillus helveticus LH-B02 favored the formation of peptides recognized as bioactive, such as α_S1-CN f(24-32) and β-CN f(193-209). Increased protein content and adjunct culture addition increased the ACE inhibitory activity. The combination of both factors had no additional effect on the bioactive potential of yogurts.

Association of dairy intake with weight change in adolescents undergoing obesity treatment

BACKGROUND

The role of dairy products in obesity treatment for adolescents is unclear. The study purpose was to assess the association between dairy intake and changes in BMI z-score (zBMI) during adolescent obesity treatment.

METHODS

Observational study nested within a randomized control trial. Linear mixed-effects regression models were adjusted for important non-lifestyle factors then further adjusted for dietary and physical activity variables. In total, 91 adolescents were studied.

RESULTS

Each serving of total dairy (β = -0.0054, P < 0.01), unflavored milk (β = -0.012, P < 0.01), reduced fat (β = -0.0078, P < 0.05), and low fat/fat-free products (β = -0.0149, P < 0.01) was associated with a decrease in zBMI over 12 months. These associations were no longer significant after adjustment for other dietary and physical activity factors. Sugar-sweetened beverage intake was inversely associated with intake of total dairy (β = -0.186, P = 0.001), unflavored milk (β = -0.115, P = 0.003) and low fat/fat-free dairy (β = -0.125, P = 0.001).

CONCLUSIONS

Intakes of total dairy, unflavored milk, reduced fat dairy and low fat/fat-free dairy products are associated with improved obesity treatment outcomes among adolescents. This could be due to co-occurring healthy lifestyle behaviors or to replacement of other food and beverages associated with obesity, such as sugar-sweetened beverages, by dairy products.

Coexistence of metabolic syndrome and osteopenia associated with social inequalities and unhealthy lifestyle among postmenopausal women in South Korea: the 2008 to 2011 Korea National Health and Nutritional Examination Survey (KNHANES)

OBJECTIVE

The prevalence of metabolic syndrome (MetS) and osteoporosis (OP) among postmenopausal women has been rapidly increasing. We examined the associations between socioeconomic status-related factors, unhealthy lifestyle, and the coexistence of MetS and osteopenia or OP.

METHODS

One thousand nine hundred ninety-one postmenopausal women aged 45 to 65 years were used to select a representative sample of the civilian, noninstitutionalized South Korean population from the 2008 to 2011 Korea National Health and Nutrition Examination Survey data. Women were grouped as neither MetS nor OP (normal), MetS, OP, and both MetS and OP (MetS + OP). Socioeconomic status (education, household income, place of residence, employment status), health-related behaviors (physical activity, alcohol consumption, smoking), and diet-related factors (intake of nutrients and food groups, eating habits, food insecurity) were obtained. Logistic regression models were used to examine the odds ratio (OR) and 95% confidence interval (CI).

RESULTS

The prevalence of MetS + OP was 32.5%. The average number of MetS risk factors in MetS + OP was 3.5, higher than that of normal and OP groups (P < 0.001). Bone mineral density at all sites was significantly lower in MetS + OP than normal and MetS groups (P < 0.001). Also, calcium, phosphorus, vitamin A, riboflavin, and niacin levels were lowest in the MetS + OP group compared with the three other groups (P < 0.05). After controlling for covariates, low-income and low-education women were more likely to have MetS + OP (OR 1.97, 95% CI 1.04-3.72); high-income and high-education group was 70% less likely to have MetS + OP (OR 0.30, 95% CI 0.10-0.86) compared with the middle-income and middle-education group.

CONCLUSIONS

Social inequalities might be powerful contributors in Korean postmenopausal women with coexistence of MetS and OP. Therefore, social and political perspective approaches are required in this population for prevention and treatment of MetS and OP. Future studies should explore to find controllable factors and thereby improve health status in postmenopausal women.

In Vitro Characterisation of the Antioxidative Properties of Whey Protein Hydrolysates Generated under pH- and Non pH-Controlled Conditions

Bovine whey protein concentrate (WPC) was hydrolysed under pH-stat (ST) and non pH-controlled (free-fall, FF) conditions using Debitrase (DBT) and FlavorPro Whey (FPW). The resultant whey protein hydrolysates (WPHs) were assessed for the impact of hydrolysis conditions on the physicochemical and the in vitro antioxidant and intracellular reactive oxygen species (ROS) generation in oxidatively stressed HepG2 cells. Enzyme and hydrolysis condition dependent differences in the physicochemical properties of the hydrolysates were observed, however, the extent of hydrolysis was similar under ST and FF conditions. Significantly higher (p < 0.05) in vitro and cellular antioxidant activities were observed for the DBT compared to the FPW-WPHs. The WPHs generated under ST conditions displayed significantly higher (p < 0.05) oxygen radical absorbance capacity (ORAC) and Trolox equivalent antioxidant capacity (TEAC) values compared to the FF-WPHs. The impact of hydrolysis conditions was more pronounced in the in vitro compared to the cellular antioxidant assay. WPH peptide profiles (LC-MS/MS) were also enzyme and hydrolysis conditions dependent as illustrated in the case of β-lactoglobulin. Therefore, variation in the profiles of the peptides released may explain the observed differences in the antioxidant activity. Targeted generation of antioxidant hydrolysates needs to consider the hydrolysis conditions and the antioxidant assessment method employed.

In vitro gastrointestinal simulation of tempe prepared from koro kratok (Phaseolus lunatus L.) as an angiotensin-converting enzyme inhibitor

This study investigated the formation of angiotensin-converting enzyme (ACE) inhibitory peptides from koro kratok beans tempe during gastrointestinal digestion. The absorption of bioactive peptides was also investigated in this study. Koro kratok was fermented by commercial culture including Rhizopus oligosporus for 48 h. Gastrointestinal digestion was simulated sequentially by hydrolysis of tempe protein extract with pepsin and pancreatin for 240 min. The peptide content, degree of hydrolysis, molecular weight distribution, and ACE inhibitory activity were analyzed. The absorption of ACE inhibitory peptides was evaluated using the inverted gut sac of Sprague Dawley rats. Results showed that some amino acids, such as Arg, Lys, Asp, Glu, Phe, and Leu, were predominantly found in tempe. After the hydrolysis process, cooked tempe exhibited the highest ACE inhibitory activity (90.05%). Although the ACE inhibitory activity of nonfermented koro kratok was lower than that of tempe, the increase in its inhibitory activity was too large (23.03%). The ACE inhibitory peptides from tempe showed a predominance of peptides with a molecular weight of < 1 kDa and could inhibit ACE activity by 84.34%. The majority of ACE inhibitory peptides from tempe was absorbed in the jejunum and exhibited an ACE inhibitory activity of 81.59%. Based on these results, it can be concluded that the fermentation and boiling process of koro kratok beans improved the release of ACE inhibitory peptides during the gastrointestinal digestion process and had an impact on its absorption.

Differences in peptide generation following in vitro gastrointestinal digestion of yogurt and milk from cow, sheep and goat

Fermentation of milk is commonly used throughout the world to produce a variety of foods with different health benefits. We hypothesised that due to differences in physicochemical properties and protein sequences among milk from different species and their fermented yogurt samples, their protein digestion and resulting peptide profiles would differ. Cow, goat and sheep milk and yogurt were compared at designated timepoints throughout in vitro gastric and intestinal digestion for differences in peptide profiles and peptide bioactivities. The results showed that most proteins in all milk and yogurt samples were digested within the early phase of gastric digestion. β-Lg and β-CN were digested faster in yogurt than milk, which was most evident for sheep products. Regardless of species, in vitro gastric and intestinal digestion released a higher concentration of specific peptides, particularly anti-hypertensives, from yogurt compared with their milk counterparts.

Structure-Based Identification and Design of Angiotensin Converting Enzyme-Inhibitory Peptides from Whey Proteins

Besides their nutritional value, whey protein (WP) peptides are food components retaining important pharmacological properties for controlling hypertension. We herein report how the use of complementary experimental and theoretical investigations allowed the identification of novel angiotensin converting enzyme inhibitory (ACEI) peptides obtained from a WP hydrolysate and addressed the rational design of even shorter sequences based on molecular pruning. Thus, after bromelain digestion followed by a 5 kDa cutoff ultrafiltration, WP hydrolysate with ACEI activity was fractioned by RP-HPLC; 2 out of 23 collected fractions retained ACEI activity and were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the face of 128 identified peptides, molecular docking was carried out to prioritize peptides and to rationally guide the design of novel shorter and bioactive sequences. Therefore, 11 peptides, consisting of 3-6 amino acids and with molecular weights in the range from 399 to 674 Da, were rationally designed and then purchased to determine the IC₅₀ value. This approach allowed the identification of two novel peptides: MHI and IAEK with IC₅₀ ACEI values equal to 11.59 and 25.08 μM, respectively. Interestingly, we also confirmed the well-known ACEI IPAVF with an IC₅₀ equal to 9.09 μM. In light of these results, this integrated approach could pave the way for high-throughput screening and identification of new peptides in dairy products. In addition, the herein proposed ACEI peptides could be exploited for novel applications both for food production and pharmaceuticals.

Integrated approach for obtaining bioactive peptides from whey proteins hydrolysed using a new proteolytic lactic acid bacteria

In this study, we investigated the ability of Enterococcus faecalis 2/28, isolated from artisan cheese, to release biopeptides from whey proteins. We used an in silico approach for predicting the bioactivities of peptides generated by E. faecalis. The results of the in vitro study showed that the whey protein hydrolysates (WPHs) obtained had angiotensin-I-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities, with inhibition of ACE being stronger than that of DPP-IV. To identify peptides that may be potential inhibitors of ACE, WPH with the highest ACE inhibitory activity was analysed using Sephadex G-75 gel filtration chromatography, Superdex peptide 10/300 GL size exclusion chromatography, and liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS). Among the identified peptides were ACE-inhibitory peptides (LDAQSAPLR, LKGYGGVSLPEW, and LKALPMH), antimicrobial peptides (AASDISLLDAQSAPLR, IIAEKTKIPAVF, IDALNENK, and VLVLDTDYK), DPP-IV-inhibitory peptides (LKALPMH, LKPTPEGDLEIL, LKGYGGVSLPE, LKPTPEGDLE, ILDKVGINY, and VLVLDTDYK), proliferation stimulating peptide (IDALNENK), and cytotoxic peptide (LIVTQTMK).

Fermented soybean meal extract improves oxidative stress factors in the lung of inflammation/infection animal model

Context

Fermented soybean products have been used in various ways, and more research is being conducted on them to reveal their benefit.

Objective

The objective of this study was to evaluate the antioxidative activity of fermented soybean meal extract by Lactobacillus plantarum in vitro and in vivo tests.

Materials and methods

A Lactobacillus plantarum strain RM10 was selected through plate and fermentation experiment, which increased the degree of protein hydrolysis (1.015 μg/mL) and antioxidant activity in soybean meal fermented by selected bacteria (FSBM). In vivo study was done on septic rats as an inflammation/infection model, and then the trial groups were treated with different concentrations of fermented soybean meal extracts (FSBM, 5, 10, and 20%).

Results

DPPH radical-scavenging and ferrozine ion-chelating activity enhanced (P < 0.05) after fermentation of soybean meal compared to control group. Reduced (P < 0.05) expression of inflammatory genes and enzymes was detected in the lungs of rats treated with fermented soybean meal extract.

Discussion and conclusions

These results demonstrated that a diet containing fermented soybean meal extract improved extreme inflammatory response in an infectious disease like sepsis by reducing inflammatory factors.

What Do We Know about Diet and Markers of Cardiovascular Health in Children: A Review

Chronic diseases such as cancer, diabetes, and cardiovascular diseases (CVD) are the main health concerns in the 21st century, with CVD as the number one cause of mortality worldwide. Although CVD hard endpoints such as stroke or heart attack do not usually occur in children, evidence shows that the manifestation of CVD risk factors begins in childhood, preceding clinical complications of CVD in adulthood. Dietary intake is a modifiable risk factor that has been shown to make a substantial contribution to the risk of CVD in adulthood. However, less is known about the association between dietary intake and markers of cardiovascular health in children. This review summarises the current evidence on the relationship between dietary intake and markers of cardiovascular health including traditional CVD risk factors, physical fitness, and indices of arterial stiffness and wave reflection in children. Original research published in English, between January 2008 and December 2018 fulfilling the objective of this review were screened and included. Findings show that adaptation of a healthy lifestyle early in life can be beneficial for reducing the risk of CVD later in life. Furthermore, keeping arterial stiffness low from a young age could be a potential CVD prevention strategy. However, limited studies are available on diet-arterial stiffness relationship in children, and future research is required to better understand this association to aid the development and implementation of evidence-based strategies for preventing CVD-related complications later in life.

Identification of new bioactive peptides from Kefir milk through proteopeptidomics: Bioprospection of antihypertensive molecules

Kefir, a probiotic beverage prepared from fermented milk, has been associated with antihypertensive activity. However, the bioactive molecules responsible for this activity still remain unclear. Therefore, in this study we aim to evaluate the mechanisms of the antihypertensive effects of Kefir in the two-kidney one-clip hypertension model, and to bioprospect for bioactive peptides identified by proteomic methodologies. Treatment with Kefir was performed via gavage, and resulted in a 37 mmHg reduction in systolic arterial pressure and 19% inhibition of angiotensin converting enzyme (ACE) activity. For the proteopeptidomic study, the protein extract of Kefir beverage and non-fermented bovine milk were analysed by MALDI-TOF mass spectrometry, and their tryptic digestion products sequenced via Shotgun proteomics (Q-Exactive mass spectrometer). A list of 35 peptides with potential hypertensive activity due to ACE inhibition were identified. These results demonstrate the benefits of Kefir products, and may guide the design of new antihypertensive drugs.

Identification of angiotensin converting enzyme and dipeptidyl peptidase-IV inhibitory peptides derived from oilseed proteins using two integrated bioinformatic approaches

Angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) play critical roles in the development of hypertension and type 2 diabetes, respectively. Inhibiting ACE and DPP-IV activity using peptides has become part of new therapeutic strategies for supporting medicinal treatment of both diseases. In this study, oilseed proteins, including soybean, flaxseed, rapeseed, sunflower and sesame are evaluated for the possibility of generating ACE and DPP-IV inhibitory peptides using different integrated bioinformatic approaches (UniProt knowledgebase, ProtParam, BLAST, BIOPEP, PeptideRanker, Pepsite2 and ToxinPred), and three bovine proteins (β-lactoglobulin, β-casein and κ-casein) as comparisons. Compared with bovine proteins, the potency indices of ACE and DPP-IV inhibitory peptides, calculated using the BIOPEP database, suggest that oilseed proteins may be considered as good precursors of ACE inhibitory peptides but generate a relative lower yield of DPP-IV inhibitory peptides following subtilisin, pepsin (pH = 1.3) or pepsin (pH > 2) hydrolysis. Average scores aligned using PeptideRanker confirmed oilseed proteins as significant potential sources of bioactive peptides: over 105 peptides scored over 0.8. Pepsite2 predicted that these peptides would largely bind via Gln281, His353, Lys511, His513, Tyr520 and Tyr523 of ACE to inhibit the enzyme, while Trp629 would be the predominant binding site of peptides in reducing DPP-IV activity. All peptides were capable of inhibiting ACE and DPP-IV whilst 65 of these 105 peptides are not currently recorded in BIOPEP database. In conclusion, our in silico study demonstrates that oilseed proteins could be considered as good precursors of ACE and DPP-IV inhibitory peptides as well as so far unexplored peptides that potentially have roles in ACE and DPP-IV inhibition and beyond.

A critical review of the role of milk and other dairy products in the development of obesity in children and adolescents

Existing reviews suggest that milk and other dairy products do not play a role in the development of obesity in childhood, but they do make an important contribution to children’s nutrient intake. It is thus curious that public health advice on the consumption of dairy products for children is often perceived as unclear. The present review aimed to provide an overview of the totality of the evidence on the association between milk and other dairy products, and obesity and indicators of adiposity, in children. Our search identified forty-three cross-sectional studies, thirty-one longitudinal cohort studies and twenty randomised controlled trials. We found that milk and other dairy products are consistently found to be not associated, or inversely associated, with obesity and indicators of adiposity in children. Adjustment for energy intake tended to change inverse associations to neutral. Also, we found little evidence to suggest that the relationship varied by type of milk or dairy product, or age of the children, although there was a dearth of evidence for young children. Only nine of the ninety-four studies found a positive association between milk and other dairy products and body fatness. There may be some plausible mechanisms underlying the effect of milk and other dairy products on adiposity that influence energy and fat balance, possibly through fat absorption, appetite or metabolic activity of gut microbiota. In conclusion, there is little evidence to support a concern to limit the consumption of milk and other dairy products for children on the grounds that they may promote obesity.

PAAP: a web server for predicting antihypertensive activity of peptides

AIM

Hypertension is associated with development of cardiovascular disease and has become a significant health problem worldwide. Naturally-derived antihypertensive peptides have emerged as promising alternatives to synthetic drugs.

MATERIALS & METHODS

This study introduces predictor of antihypertensive activity of peptides constructed using random forest classifier as a function of various combinations of amino acid, dipeptide and pseudoamino acid composition descriptors.

RESULTS

Classification models were assessed via independent test set that demonstrated accuracy of 84.73%. Feature importance analysis revealed the preference of proline and hydrophobic amino acids at the C-terminal as well as the preference of short peptides for robust activity.

CONCLUSION

Model presented herein serves as a useful tool for predicting and analysis of antihypertensive activity of peptides.

Interaction between porous silica gel microcarriers and peptides for oral administration of functional peptides

Functional peptides, peptides that have biological activities, have attracted attention as active ingredients of functional foods and health foods. In particular, for food applications, because orally ingested peptides are degraded by digestive enzymes in the stomach, novel oral administration methods that can prevent peptide degradation and successfully deliver them intestinally are desired. In the present study, we focused on porous silica gel, which has many useful characteristics, such as large surface area, pH responsive functional groups, size controllable pores, and approval as food additives. We investigated the possibility of using porous silica gel as a peptide degradation protective microcarrier. As a result, we found that heat treatment of the silica gel at 600 °C for 2 h remarkably enhanced the adsorbed amount of many peptides under acidic conditions, and negatively charged and highly hydrophobic peptides had suitable characteristics for oral intestinal delivery with silica gel. Finally, we demonstrated the degree of protection from pepsin degradation and found that the protection of DFELEDD peptide was 57.1 ± 3.9% when DFELEDD was mixed with the heat-treated silica gel. These results indicated that the heat-treated silica gel is promising for efficient oral intestinal delivery of hydrophobic negatively charged peptides.

Processing Optimization and Characterization of Angiotensin-Ι-Converting Enzyme Inhibitory Peptides from Lizardfish (Synodus macrops) Scale Gelatin

Hypertension can cause coronary heart disease. Synthetic angiotensin-converting enzyme (ACE) inhibitors are effective antihypertensive drugs but often cause side effects. The aim of this study was to prepare potential ACE inhibitors from scales. Gelatin was extracted from lizardfish scales. Then, scale gelatin was enzymolyzed to prepare ACE inhibitory peptides using response surface methodology. Proteolytic conditions after optimization were as follows: pH 7.0, enzyme substrate ratio 3.2%, temperature 47 °C, and proteolysis lasting 2 h and 50 min. The experimental ACE inhibitory activity under optimal conditions was 86.0 ± 0.4%. Among the 118 peptides identified from gelatin hydrolysates, 87.3% were hydrophilic and 93.22% had a molecular weight <2000 Da. Gelatin peptides had high stability upon exposure to high temperature and pH as well as gastrointestinal tract enzymes. Gelatin peptides showed an antihypertensive effect in spontaneously hypertensive rats at a dosage of 2 g/kg in the long-term experiments. A new ACE inhibitory peptide was isolated from gelatin hydrolysates, and was identified as AGPPGSDGQPGAK with an IC₅₀ value of 420 ± 20 μM. In this way, ACE inhibitory peptides derived from scale gelatin have the potential to be used as healthy ACE-inhibiting drug raw materials.