The health benefits of sweet lupin seed flours and isolated proteins

Enzymatic hydrolysis of lupin protein isolates-Changes in the molecular weight distribution, technofunctional characteristics, and sensory attributes

Enzymatic hydrolysis of lupin protein isolates (LPI; Lupinus angustifolius L.) was performed with nine different protease preparations to investigate their effect on technofunctionality, sensory properties, and the integrity of the proteins to estimate the reduction of the immunoreactivity. Alcalase 2.4 L, papain, and pepsin were most effective in the degradation of the α- and β-conglutin examined by SDS-PAGE analysis, although the degree of hydrolysis only slightly increased. The technofunctional properties of LPI-solubility, emulsifying, and foaming activity-were improved by most of the proteolytic enzymes with the most impressive increase from 980% foam activity for LPI up to 3,614% foam activity for pepsin hydrolysate. The formation of bitterness, most likely linked to generation of bitter peptides, was pronounced in the Alcalase hydrolysate, while the other hydrolysates did not show an extensive increase in bitterness compared to the LPI. Other sensory attributes of the hydrolysates-with the exception of Alcalase treatment-were also very similar to the LPI. The results of this study show the potential of enzymatic degradation of LPI to modify the IgE-reacting polypeptides and to improve the technofunctionality of the isolates and therefore their use as food ingredients.

Lupin seeds storage protein composition and their interactions with native flavonoids

BACKGROUND

Lupin-based food, due to the high content of functional proteins and phenolic compounds, are widely used in human nutrition. Unfortunately, proteins and phenolic compounds can easily interact with each other which results in formation of complexes that affect properties of both components. Therefore, in this study, composition of the seeds storage proteins isolated from Lupinus albus and L. angustifolius and their interactions with native flavonoids were investigated.

RESULTS

Based on the chromatographic separations, six proteins fractions of lupin seeds storage proteins were identified. The results indicate that two dominant fractions, α-conglutin and β-conglutin, constitute up to 80% of all proteins present in the seeds. Three flavonoids interacting with the proteins were identified as apigenin C-glycosides. The lowest flavonoids content was noted in the main storage proteins while in both lupin seeds species over 90% of flavonoids interacted with the proteins present in late-embryogenesis abundant (LEA) protein fraction.

CONCLUSIONS

Protein-phenolic compound complexes can affect the digestibility of proteins and bioavailability of phenolic compounds, and thus the functional and nutritional properties of products derived from lupin seeds can be changed. Therefore, a better understanding of factors affecting the nutritional value of lupin seeds proteins and flavonoids is necessary to optimize the biological use of this plant for human nutrition. © 2019 Society of Chemical Industry.

Soybean Peptides Exert Multifunctional Bioactivity Modulating 3-Hydroxy-3-Methylglutaryl-CoA Reductase and Dipeptidyl Peptidase-IV Targets in Vitro

This study was aimed at evaluating the cellular mechanism through which peptic (P) and tryptic (T) soybean hydrolysates modulate the targets involved in hypocholesterolemic pathways in HepG2 and antidiabetic pathways in Caco-2 cells. Both hydrolysates (tested in the concentration range of 0.5-2.5 mg/mL) inhibited the 3-hydroxy-3-methylglutaryl-CoA reductase activity in HepG2 cells. In addition, Soybean P increased LDLR protein levels on HepG2 membranes by 51.5 ± 11.6% and 63.0 ± 6.9% (0.5-1.0 mg/mL) whereas Soybean T increased them by 55.2 ± 9.7% and 85.8 ± 21.5% (0.5-1.0 mg/mL) vs the control, with a final improved HepG2 capacity in the uptake of extracellular LDL. Soybean P reduced in vitro the dipeptidyl peptidase-IV activity by 16.3 ± 3.0% and 31.4 ± 0.12% (1.0 and 2.5 mg/mL), whereas Soybean T reduced it by 15.3 ± 11.0% and 11.0 ± 0.30% (1.0 and 2.5 mg/mL) vs the control. Finally, both hydrolysates inhibited dipeptidyl peptidase-IV activity in situ in human intestinal Caco-2 cells. This investigation may help to explain the activities observed in experimental and clinical studies.

Inhibition of human 3-hydroxy-3-methylglutaryl CoA reductase by peptides leading to cholesterol homeostasis through SREBP2 pathway in HepG2 cells

In mammalian cells, human 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), a rate-limiting endoplasmic reticulum (ER) bonded enzyme, plays a central role in the cholesterol homeostasis via the negative feedback mechanism. The present study indicates that the interactions of novel peptides with the catalytic domain of HMGCR, provides an alternative therapeutic candidate for reducing cholesterol. The potential natural origin of HMGCR peptide inhibitors were filtered from the peptide library using the molecular docking, which revealed three strong candidates for inhibition. This information was used for synthesizing peptides, which were evaluated for inhibition against HMGCR. The stronger docking interactions were confirmed by experimental dissociation constant (K_D) values of 9.1 × 10^-9 M, 1.4 × 10^-8 M and 1.2 × 10^-8 M for peptides NALEPDNRIESEGG (Pep-1), NALEPDNRIES (Pep-2) and PFVKSEPIPETNNE (Pep-3) respectively. The immunological based interactions show a strong evidence of peptide-HMGCR complexes. The LDL uptake showed enhancements after treatments with peptides in the extracellular environment of HepG2 cells, which was further, corroborated through increase in the immunofluorescence signal of the localized LDL-R protein expression on the cell membrane. The results showed that the mRNA and protein expression of transcription factors were significantly up-regulated showing regulation of cholesterol biosynthesis in peptide treated HepG2 cells. The binding of transcription factors, sterol regulatory element (SRE) and cAMP-response element (CRE) on HMGCR promotor further confirms the cholesterol biosynthesis regulation. All the above results suggested a key role of peptide/s in alleviating cholesterol accumulation in tissue via inhibition of rate-limiting HMGCR enzyme.

Recent advances in developing PCSK9 inhibitors for lipid-lowering therapy

Cardiovascular disease is the major cause of death globally, with hypercholesterolemia being an important risk factor. The PCSK9 represents an attractive therapeutic target for hypercholesterolemia treatment and is currently in the spotlight of the scientific community. After autocatalytic activation in the hepatocyte endoplasmic reticulum, this convertase binds to the LDLR and channels it to the degradation pathway. This review gives an overview on the latest developments in the inhibition of PCSK9, including disruption of the protein-protein interaction (PPI) between PCSK9 and LDLR by peptidomimetics, adnectins and monoclonal antibodies and the suppression of PCSK9 expression by small molecules, siRNA and genome editing techniques. In addition, we discuss alternative approaches, such as anti-PCSK9 active vaccination and heparin mimetics.

Post-translational cleavage pattern of Lupinus angustifolius γ-conglutin

BACKGROUND

Protein post-translational modifications are a key element for the functional diversity of the proteome. The modifications generally refer to the addition of functional groups to certain proteins; however, proteolytic cleavage is also one of the relevant events during protein maturation. γ-Conglutin is a unique protein fraction present in lupin seeds that is marked by numerous unusual properties. This protein fraction undergoes very complex post-translational maturation. Unfortunately, the precise mechanism of γ-conglutin post-translational processing is not yet fully understood.

RESULTS

Two independent methods were used to study γ-conglutin post-translational cleavage processing. Edman N-terminal sequencing indicates that the signal peptide is processed at Tyr34, while α- and β-subunit cleavage takes place between Ser295 and Ser296. High-resolution mass spectrometry revealed a great diversity of N-terminal sequences of γ-conglutin α-subunit. However, most abundant peptides also began from Tyr34. Mass spectrometric analyses additionally confirmed the subunit cleavage position between two serine residues.

CONCLUSIONS

The results indicate that the proteolytic processing of γ-conglutin signal peptide is not precise. On the other hand, the post-translational cleavage between α- and β-subunits of γ-conglutin is very conserved. Interestingly, the results also indicate that proteolytic processing leading to the formation of two subunits of γ-conglutin is incomplete, leaving a certain amount of the protein in an uncut form. © 2018 Society of Chemical Industry.

Peptides derived from lupin proteins confer potent protection against oxidative stress

BACKGROUND

Lupin seeds are rich in proteins, which are utilized in the food industry. There is an increased interest in lupin research due to its association with health-related benefits, such as reduction of hypertension and hyperglycemia. However, studies on the peptides derived from lupin proteins are rare.

RESULTS

Lupin protein hydrolysates (LPHs) were prepared by proteolysis using alcalase, trypsin and pepsin, respectively. All the hydrolysates demonstrated higher antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities compared to lupin proteins. The hydrolysates were fractionated into three fractions based on molecular weight (MW), and the peptides with MW < 3 kDa (LPH3) had the highest antioxidant and ACE inhibitory activities compared to other fractions. Cell model study revealed that LPH3 fraction had the highest protection against the generation of reactive oxygen species in HepG2 cells, which was associated with increased activities of superoxide dismutase and glutathione peroxidase through upregulation of SOD1, GPX1, GCLM, SLC7A11 and SRXN1 expression.

CONCLUSIONS

The analysis of amino acid composition indicated that the peptides were characterized with high content of hydrophobic amino acids, which may be responsible for the greatest antioxidant activity. This study highlights the promising potential of lupin peptides as a functional ingredient in healthy foods. © 2018 Society of Chemical Industry.

First Food-Derived Peptide Inhibitor of the Protein-Protein Interaction between Gain-of-Function PCSK9D374Y and the Low-Density Lipoprotein Receptor

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is involved in cholesterol homeostasis, because it induces the low-density lipoprotein receptor (LDLR) degradation. This protein may carry some positive or negative mutations: PCSK9^D374Y is one of the most dangerous gain-of-function mutations. This paper reports the identification of the first food-derived peptide able to inhibit the protein-protein interaction (PPI) between PCSK9^D374Y and LDLR. In fact, T9 (GQEQSHQDEGVIVR), an absorbable peptide deriving from lupin β-conglutin, is able to impair the PPI between PCSK9^D374Y and the LDLR, with an IC₅₀ value equal to 285.6 ± 2.46 μM. The consequence of this inhibition is an increase of the protein level of the LDLR located on hepatic cell membranes up to 74.3 ± 4.4% and the restoration of the functional capability of HepG2 cells to uptake extracellular low-density lipoprotein up to 83.1 ± 1.6%. Finally, the putative binding mode of T9 to the LDLR binding site located on PCSK9^D374Y was postulated by in silico tools.

In vitro investigation of bioactivities of solid-state fermented lupin, quinoa and wheat using Lactobacillus spp

This study is an in-vitro investigation of the health-promoting properties of fermented whole-grain lupin, quinoa and wheat, using 72 h solid-state fermentation by Lactobacillus reuteri K777 and Lb. plantarum K779. Antiproliferative activity against Caco-2 and MCF-7 cancer cell lines (tumour cell lines of intestinal and mammary origin, respectively) was investigated, as well as α-amylase and α-glucosidase inhibition, antihypertensive, antioxidant and proteolytic activities. ABTS antioxidant activities of fermented lupin (FL, 55% w/v), quinoa (FQ, 55% w/v) and wheat (FW, 55% w/v) ranged from ∼12.0% to 55.0%, ∼17.6% to 73.0%, and ∼29.0% to 26.0%, respectively. Lupin, quinoa and wheat fermented by L. plantarum had pronounced antihypertensive activities (∼85%). The α-glucosidase inhibition in FL was higher than that of FQ and FW. The magnitude of the antiproliferative activities of FL was markedly greater (p < 0.05) than of FQ and FW by approximately three-fold and two-folds against Caco-2 and MCF-7 cell lines, respectively.

Phenolic contents and antioxidant capacities of wild and cultivated white lupin (Lupinus albus L.) seeds

The aim of this study was to compare the antioxidant capacities and phenolic compound profiles of wild and cultivated Lupinus albus L. seeds. The total phenolic content (TPC), radical scavenging activity, ferric-reducing antioxidant power (FRAP) and antioxidant activity in an β-carotene-linoleic acid emulsion were determined. Liquid chromatography-mass spectrometry was used to identify phenolics. The TPC of lupin seeds ranged from 4.36 to 7.24 mg gallic acid equivalent/g dry matter (d.m.). The dominant phenolics of all genotypes were two p-coumaric acid derivatives (0.74-1.61 and 0.66-1.63 mg/g d.m.) and apigenin-6,8-di-C-glucoside (1.13-1.31 mg/g d.m.). The results of antioxidant assays of wild lupin extracts were similar to or lower than those of the cultivated variety. FRAP and ABTS⁺ scavenging activity were correlated with the contents of the more polar p-coumaric acid derivative and apigenin-6,8-di-C-glucoside. Generally, significant differences between cultivated and wild L. albus seeds were not found in antioxidant capacities and phenolic compound contents.

Narrow-leafed lupin (Lupinus angustifoliusL.) seed β-conglutins reverse the induced insulin resistance in pancreatic cells

Narrow-leafed lupin β-conglutin proteins may help to prevent and treat insulin resistance through pleiotropic effects.

Nutraceutical approaches to metabolic syndrome

Metabolic Syndrome (MetS), affecting at least 30% of adults in the Western World, is characterized by three out of five variables, from high triglycerides, to elevated waist circumference and blood pressure. MetS is not characterized by elevated cholesterolemia, but is rather the consequence of a complex interaction of factors generally leading to increased insulin resistance. Drug treatments are of difficult handling, whereas well-characterized nutraceuticals may offer an effective alternative. Among these, functional foods, e.g. plant proteins, have been shown to improve insulin resistance and reduce triglyceride secretion. Pro- and pre-biotics, that are able to modify intestinal microbiome, reduce absorption of specific nutrients and improve the metabolic handling of energy-rich foods. Finally, specific nutraceuticals have proven to be of benefit, in particular, red-yeast rice, berberine, curcumin as well as vitamin D. All these can improve lipid handling by the liver as well as ameliorate insulin resistance. While lifestyle approaches, such as with the Mediterranean diet, may prove to be too complex for the single patient, better knowledge of selected nutraceuticals and more appropriate formulations leading to improved bioavailability will certainly widen the use of these agents, already in large use for the management of these very frequent patient groups. Key messages Functional foods, e.g. plant proteins, improve insulin resistance. Pro- and pre-biotics improve the metabolic handling of energy-rich foods. Nutraceutical can offer a significant help in handling MetS patients being part of lifestyle recommendations.

Effect of Germination and Fermentation on Carbohydrate Composition of Australian Sweet Lupin and Soybean Seeds and Flours

This study investigated the effect of germination and fermentation on the composition of carbohydrates in Australian sweet lupin. Specifically, the amount of sugars (sucrose, fructose, and glucose), starch, oligosaccharides (verbascose, stachyose, and raffinose), and dietary fiber were measured in germinated lupin seeds and fermented lupin flour, and compared with those in soy. High performance liquid chromatography coupled with refractive index was employed for quantitation of sugars, starch, and oligosaccharides, and gas chromatography coupled with a flame ionization detector was used for quantitation of simple sugars in total, and soluble, and insoluble dietary fiber. The enzyme activities of α-amylase and α-glucosidase were compared before and after germination or fermentation. The α-amylase activity in germinated lupin increased to  ∼17 nmol/mL/min/0.1 g and in germinated soy∼32; in fermented lupin, the activity increased to ∼52, while in fermented soy it decreased to ∼20. In general, germination or fermentation decreased the oligosaccharide content, and increased the total sugar in samples (p < 0.05). Total oligosaccharides in lupin after uncontrolled germination were reduced by 98% to 6 mg/g, and after controlled germination reduced by 44% to 86 mg/g. Fermentation with yogurt culture lowered the content of total oligosaccharides due to 94% decrease in stachyose. Total oligosaccharides in soy flour prior to fermentation were 180 mg/g and significantly decreased to ∼124 mg/g in fermented soy. Germination did not affect the starch content. There was no significant change in the amounts of total, soluble, and insoluble dietary fiber after germination or fermentation of lupin except for galactose, which was significantly reduced in germinated lupin seeds. Soluble dietary fiber in germinated soy significantly increased. Germination and fermentation are simple and effective techniques to reduce the oligosaccharides while maintaining the composition of dietary fibers.

Calcium, Iron, and Zinc Bioaccessibilities of Australian Sweet Lupin (Lupinus angustifolius L.) Cultivars

In this study, we aimed to determine the effect of the cultivar and dehulling on calcium, iron, and zinc bioaccessibilities of Australian sweet lupin (ASL). Ten ASL cultivars grown in 2011, 2012, and 2013 in Western Australia were used for the study. The bioaccessibilities of calcium, iron, and zinc in whole seed and dehulled lupin samples were determined using a dialysability method. The cultivar had significant effects on calcium, iron, and zinc contents and their bioaccessibilities. Average bioaccessibilities of 6% for calcium, 17% for iron, and 9% for zinc were found for whole seeds. Dehulled ASL had average calcium, iron, and zinc bioaccessibilities of 11%, 21%, and 12%, respectively. Compared to some other pulses, ASL had better iron bioaccessibility and poorer calcium and zinc bioaccessibilities. Dehulling increased calcium bioaccessibilities of almost all lupin cultivars. The effect of dehulling on iron and zinc bioaccessibilities depends on the ASL cultivar.

Correlation analysis of protein quality characteristics with gluten-free bread properties

Research demonstrates the correlation of protein technofunctional properties with gluten-free bread quality characteristics.

Bioactivities of alternative protein sources and their potential health benefits

Increasing the utilisation of plant proteins is needed to support the production of protein-rich foods that could replace animal proteins in the human diet so as to reduce the strain that intensive animal husbandry poses to the environment.

Peptides Derived from Soy and Lupin Protein as Dipeptidyl-Peptidase IV Inhibitors: In Vitro Biochemical Screening and in Silico Molecular Modeling Study

Dipeptidyl peptidase IV (DPP-IV) is a new molecular target correlated with the development of type 2 diabetes. Literature describes the identification of some inhibitory peptides from the hydrolysis of different food proteins. This article reports a study on six peptides from soybean and lupin proteins, i.e., Soy 1 (IAVPTGVA), Soy 2 (YVVNPDNDEN), Soy 3 (YVVNPDNNEN), Lup 1 (LTFPGSAED), Lup 2 (LILPKHSDAD), and Lup 3 (GQEQSHQDEGVIVR), which were screened for their capacity to inhibit the activity of DPP-IV, using an in vitro bioassay against human recombinant DPP-IV. Two peptides Soy 1 and Lup 1 resulted to be efficient inhibitors with IC50 values equal to 106 and 228 μM, respectively. A molecular docking analysis predicted the key molecular interactions, stabilizing the active peptides within DPP-IV enzyme. Soy and lupin proteins may be sources of DPP-IV inhibitory peptides potentially useful for the prevention of type 2 diabetes.

Hypocholesterolaemic Activity of Lupin Peptides: Investigation on the Crosstalk between Human Enterocytes and Hepatocytes Using a Co-Culture System Including Caco-2 and HepG2 Cells

Literature indicates that peptic and tryptic peptides derived from the enzymatic hydrolysis of lupin protein are able to modulate cholesterol metabolism in human hepatic HepG2 cells and that part of these peptides are absorbed in a small intestine model based on differentiated human Caco-2 cells. In this paper, a co-culture system, including Caco-2 and HepG2 cells, was investigated with two objectives: (a) to verify whether cholesterol metabolism in HepG2 cells was modified by the peptides absorption through Caco-2 cells; (b) to investigate how lupin peptides influence cholesterol metabolism in Caco-2 cells. The experiments showed that the absorbed peptides, not only maintained their bioactivity on HepG2 cells, but that this activity was improved by the crosstalk of the two cells systems in co-culture. In addition, lupin peptides showed a positive influence on cholesterol metabolism in Caco-2 cells, decreasing the proprotein convertase subtilisin/kexin type 9 (PCSK9) secretion.

Lupin Peptides Modulate the Protein-Protein Interaction of PCSK9 with the Low Density Lipoprotein Receptor in HepG2 Cells

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has been recently identified as a new useful target for hypercholesterolemia treatment. This work demonstrates that natural peptides, deriving from the hydrolysis of lupin protein and absorbable at intestinal level, are able to inhibit the protein-protein interaction between PCSK9 and the low density lipoprotein receptor (LDLR). In order to sort out the best potential inhibitors among these peptides, a refined in silico model of the PCSK9/LDLR interaction was developed. Docking, molecular dynamics (MD) simulations and peptide binding energy estimations, by MM-GBSA approach, permitted to select the two best candidates among tested peptides that were synthesized and evaluated for their inhibitory activity. The most active was P5 that induced a concentration dependent inhibition of the PCSK9-LDLR binding, with an IC₅₀ value equal to 1.6 ± 0.33 μM. Tested at a 10 μM concentration, this peptide increased by 66 ± 21.4% the ability of HepG2 cells to take up LDL from the extracellular environment.

Proteomic characterization of hempseed (Cannabis sativa L.)

This paper presents an investigation on hempseed proteome. The experimental approach, based on combinatorial peptide ligand libraries (CPLLs), SDS-PAGE separation, nLC-ESI-MS/MS identification, and database search, permitted identifying in total 181 expressed proteins. This very large number of identifications was achieved by searching in two databases: Cannabis sativa L. (56 gene products identified) and Arabidopsis thaliana (125 gene products identified). By performing a protein-protein association network analysis using the STRING software, it was possible to build the first interactomic map of all detected proteins, characterized by 137 nodes and 410 interactions. Finally, a Gene Ontology analysis of the identified species permitted to classify their molecular functions: the great majority is involved in the seed metabolic processes (41%), responses to stimulus (8%), and biological process (7%).

BIOLOGICAL SIGNIFICANCE

Hempseed is an underexploited non-legume protein-rich seed. Although its protein is well known for its digestibility, essential amino acid composition, and useful techno-functional properties, a comprehensive proteome characterization is still lacking. The objective of this work was to fill this knowledge gap and provide information useful for a better exploitation of this seed in different food products.