Wheat Gliadin Research Articles

Gluten Is Not Gluten.

Wheat gluten is responsible for the unique baking properties of wheat flour, but it also causes wheat-related disorders in predisposed individuals. Different commercially available gluten materials are commonly used for a variety of assays, but a detailed characterization of their composition is missing in many cases. This is why we aimed to provide an in-depth analysis of three commonly used gliadin and gluten materials from two different batches using gel electrophoretic and chromatographic techniques. The gliadin material did not show the typical qualitative and quantitative protein composition and does not appear to be representative of wheat gliadin. The two gluten materials had the expected protein composition, but both showed large batch-to-batch variability regarding total protein content. Since these variations result in different biochemical, immunological, and functional behaviors, it is important to analyze at least the total protein content of each material and each batch.

Wheat gliadin/xanthan gum intermolecular complexes: Interaction mechanism and structural characterization

In this study, the interactions between wheat gliadin (GL) and xanthan gum (XG) were investigated to design new systems with potential applications as a gluten-free substitute product. Combining spectral with morphological and molecular docking methods allowed the establishment of the complexation mechanism between globular hydrophobic GL and the hydrophilic XG with an extended and partially disordered backbone. GL maintains intact its hydrophobic core even at high GL/XG ratios and organizes into small aggregate–type assemblies. The stable and uniform complexes have a low GL content, based on intermolecular hydrogen bonds and hydrophobic interactions. The GL/XG combining ratio influences the size, structure and interaction mechanism of the microparticles. The preferred sites of interaction and the binding affinities were determined by molecular docking on GL libraries and XG models. This research may provide significant knowledge for the development of low-GL wheat food products using a dietary fiber polysaccharide as a functional compound.

In Vitro Protective Effect of Pea-Derived Peptides (PPs) via the Keap1/Nrf2 Signaling Pathway on Alpha-Gliadin-Sensitizing Peptide Induced Cacao-2 Cells.

Celiac disease (CD) is an allergic intestinal disease caused mainly by gliadin in wheat, which is widespread in the population and currently lacks effective treatment. α-Gliadin peptides cause cellular damage by substantially increasing cellular reactive oxygen species (ROS) levels. This study investigates the protective effect of 11 pea-derived peptides (PPs) on ɑ-gliadin peptide (P31-43) treated Caco-2 cells. Results show that cells treated with PP2, PP5, and PP6 peptides significantly reduce the cell mortality caused by P31-43. Three PPs significantly reduce the P31-43-induced decrease in ROS levels to control levels, and there is no difference between them and the vitamin C (Vc) group. The results in terms of antioxidant-related enzymes show that PPs significantly decrease superoxide dismutase activity (SOD), glutathione reductases (GR), and glutathione (GSH)/oxidized glutathione (GSSG) levels, thus significantly enhancing the antioxidant level of cells. By studying the key proteins of the Kelch-like ECH-associated protein 1 (Keap1)/NF-E2-related factor 2 (Nrf2) pathway, it is found that PPs activate the Keap1/Nrf2 signaling pathway. The study finds that peptides from peas can effectively alleviate ɑ-gliadin peptide-induced cell damage. The discovery of these food-derived peptides provides novel potential solutions for the prevention and treatment of CD.

Amyloid-like Aggregation of Wheat Gluten and Its Components during Cooking: Mechanisms and Structural Characterization.

Amyloid-like aggregation widely occurs during the processing and production of natural proteins, with evidence indicating its presence following the thermal processing of wheat gluten. However, significant gaps remain in understanding the underlying fibrillation mechanisms and structural polymorphisms. In this study, the amyloid-like aggregation behavior of wheat gluten and its components (glutenin and gliadin) during cooking was systematically analyzed through physicochemical assessment and structural characterization. The presence of amyloid-like fibrils (AFs) was confirmed using X-ray diffraction and Congo red staining, while Thioflavin T fluorescence revealed different patterns and rates of AFs growth among wheat gluten, glutenin, and gliadin. AFs in gliadin exhibited linear growth curves, while those in gluten and glutenin showed S-shaped curves, with the shortest lag phase and fastest growth rate (t1/2 = 2.11 min) observed in glutenin. Molecular weight analyses revealed AFs primarily in the 10-15 kDa range, shifting to higher weights over time. Glutenin-derived AFs had the smallest ζ-potential value (-19.5 mV) and the most significant size increase post cooking (approximately 400 nm). AFs in gluten involve interchain reorganization, hydrophobic interactions, and conformational transitions, leading to additional cross β-sheets. Atomic force microscopy depicted varying fibril structures during cooking, notably longer, taller, and stiffer AFs from glutenin.

Interactions of gliadins with flavonoids and their glycosides studied with application of FT-Raman spectroscopy

FT-Raman spectroscopy was applied to study interactions between wheat gliadins and three flavonoids and their glycosides. Complexes gliadins-flavonoids/glycosides were extracted from the model wheat dough. As flavonoids were used quercetin, naringenin, hesperetin and their glycosides rutin, naringin, hesperidin in the amount of 0.05%, 0.1% and 0.2%. The analysis of the FT-Raman spectra showed that the tested compounds caused changes in the secondary and tertiary structure of gliadins. In the case of gliadins, these changes concerned mainly α-helices. Quercetin induced a different type of structural changes compared to naringenin and hesperetin, which was probably due to the presence of a double bond on the C ring and an additional OH group on the B ring in the structure of this molecule. On the other hand, the interactions of glycosides with gliadins were affected by the place of attachment of the sugar part in the structure of the glycoside. Flavonoids/glycosides significantly increased the content of disulfide bridges in the g-g-g conformation. Changes in the amino acid microenvironment (tyrosine and tryptophan) indicate the formation of a more ordered structure in gliadins.

High Fat Diet-Wheat Gliadin Interaction and its Implication for Obesity and Celiac Disease Onset: In Vivo Studies.

The intestinal immune system plays a crucial role in obesity and insulin resistance. An altered intestinal immunity is associated with changes to the gut microbiota, barrier function, and tolerance to luminal antigens. Lipid metabolism and its unbalance can also contribute to acute and chronic inflammation in different conditions. In celiac disease (CD), the serum phospholipid profile in infants who developed CD is dramatically different when compared to that of infants at risk of CD not developing the disease. In a mouse model of gluten sensitivity, oral wheat gliadin challenge in connection with inhibition of the metabolism of arachidonic acid, an omega-6 polyunsaturated fatty acid, specifically induces the enteropathy. Recent evidence suggests that gluten may play a role also for development of life-style related diseases in populations on a high fat diet (HFD). However, the mechanisms behind these effects are not yet understood. Exploratory studies in mice feed HFD show that wheat gliadin consumption affects glucose and lipid metabolic homeostasis, alters the gut microbiota, and the immune cell profile in liver.

Impact of Endogenous Lipids on Mechanical Properties of Wheat Gluten Fractions, Gliadin and Glutenin, under Small, Medium, and Large Deformations

The individual viscoelastic responses of gluten proteins and their lipid-removed counterparts were studied under mixing deformations and small, medium, and large deformations selected in the Large Amplitude Oscillatory Shear (LAOS) sweeps. During Farinograph mixing, gliadin reached the 500 BU consistency line after 3.6 ± 0.4 min, while the highest consistency recorded for lipid-removed gliadin was 268 ± 8.4 BU, suggesting a reduction in the water absorption of gliadin in the absence of lipids. The affinity of glutenin to water increased in the absence of lipids, as development time was reached 11 min earlier for lipid-removed glutenin. Under small LAOS strains, tanδ of gliadin remained constant with the removal of lipids, while glutenin’s elasticity decreased (tanδ increased) in the absence of lipids at high frequencies. Intracycle strain-stiffening behavior (e3/e1 > 0) of gliadin increased under medium deformations with high frequency and decreased under low-frequency large deformations as lipids were removed, while this response decreased for glutenin with the removal of lipids only under high-frequency medium and large deformations. Under large LAOS strains, the clockwise rotation of the Lissajous–Bowditch curves for gliadin in the absence of lipids suggested higher intercycle strain-softening and shear-thinning, while the counter-clockwise rotation of the curves for glutenin in the absence of lipids suggested lower intercycle strain-softening and shear-thinning. These results revealed the influence of endogenous lipids on the viscous-dominated response of gliadin and to the elastic-dominated response of glutenin, while balancing the intracycle strain-stiffening behaviors of these gluten proteins especially under large deformations.

The changes induced by hydrodynamic cavitation treatment in wheat gliadin and celiac-toxic peptides.

The online version contains supplementary material available at 10.1007/s13197-024-05973-7.

Wheat gliadin hydrolysates based nano-micelles for hydrophobic naringin: Structure characterization, interaction, and in vivo digestion

In this study, enzymatic hydrolysis was used to fabricate wheat gliadin hydrolysates (WGHs) for the encapsulation and protection of naringin. The exposure of hydrophilic amino acids decreased the critical micelle concentration (from 0.53 ± 0.02 mg/mL to 0.35 ± 0.03 mg/mL) and improved solubility, which provided amphiphilic conditions for the delivery of naringin. The hydrolysates with a degree of hydrolysis (DH) of 9 % had the strongest binding affinity with naringin, and exhibited the smallest particle size (113.7 ± 1.1 nm) and the highest encapsulation rate (83.2 ± 1.3 %). The storage, heat and photochemical stability of naringin were improved via the encapsulation of micelles. Furthermore, the micelles made up of hydrolysates with a DH of 12 % significantly enhanced the bioavailability of naringin (from 19.4 ± 4.3 % to 46.8 ± 1.4 %). Our experiment provides theoretical support for the utilization of delivery systems based on water-insoluble proteins.

Omega-5-gliadin-specific immunoglobulin E-positive, but wheat-specific immunoglobulin E-negative wheat allergy dependent on augmentation factors—a frequent presentation

Aim: Most patients with wheat allergy dependent on augmentation factors (WALDA) show specific immunoglobulin E (sIgE) to ω5-gliadin. However, some WALDA patients may show negative results when testing for sIgE to total wheat extract. This is the first study to investigate potential clinical and serological differences in patients with ω5-gliadin-positive, challenge-confirmed WALDA dependent on their sensitization to total wheat extract. Methods: Clinical and serological characteristics of patients with challenge-confirmed, ω5-gliadin-positive WALDA were analyzed based on the absence or presence of sIgE to wheat (cut-off 0.35 kUA/L). Results: Thirty-six patients with challenge-confirmed WALDA were included (19 female; median age 50.5 years; median sIgE to ω5-gliadin 6.5 kUA/L). SIgE levels to grass pollen were related to the presence of any atopic comorbidity (P < 0.001) and showed a correlation with sIgE to wheat (P = 0.003), but not to the gluten-related allergens [all not significant (ns)]. Thirty-nine percent of patients (n = 14) showed sIgE levels to wheat lower than 0.35 kUA/L; in 19.4% (n = 7) levels were even below the detection limit of 0.01 kUA/L. WALDA patients without sIgE to wheat showed lower levels of total immunoglobulin E (IgE) and sIgE to wheat gluten, gliadins, and ω5-gliadin (all P < 0.001) as well as to grass pollen (P = 0.03). No significant differences in clinical characteristics like delay until diagnosis, the presence of an atopic condition, reaction severity, or threshold in the oral challenge test were observed. Conclusions: SIgE to wheat extract was associated not only with sensitization against gluten allergens but also reflected total IgE production and concomitant grass pollen allergy, making it an insensitive and unspecific biomarker for WALDA. There were no clinical divergences between WALDA patients without or with sIgE to wheat. SIgE to total wheat extract does not appear to be clinically relevant and remains negative in a significant proportion of WALDA patients.

Changes in the structure and aggregation behavior of wheat glutenin and gliadin induced by the combined action of heat treatment and wheat bran dietary fiber

The effects of different levels of wheat bran dietary fiber (WBDF) on the structure and aggregation behavior of glutenin and gliadin during heating were studied. With increasing temperature, the tanδ value increased from 0.23 to 0.51 in the WBDF-glutenin system (P < 0.05) and decreased from 1.31 to 0.31 in the WBDF-gliadin system (P < 0.05). In the WBDF-gliadin system, the amount of free –SH increased from 0.46 to 5.18 μmol/g with increasing WBDF levels and temperature (P < 0.05). WBDF was involved in the rearrangement of the molecular forces of glutenin and gliadin during heating. WBDF enhanced the hydrophobic interaction between glutenin and gliadin at 25 °C and 60 °C, and weakened this interaction at 95 °C and 130 °C. Overall, WBDF addition had a greater effect than temperature for the induction of significant structural changes in glutenin and gliadin. This study provides a more comprehensive theoretical basis for the quality improvement of high-fiber flour products.

Determination and Analysis of Composition, Structure, and Properties of Teff Protein Fractions.

To develop teff-based food products with acceptable quality, the composition, structure, and properties of teff protein fractions should be better understood. In this study, teff proteins were extracted, and their protein composition, structure, and properties were calculated, analyzed, and compared with those of wheat gliadin and glutenin. Results showed that teff flour contained 9.07% protein, with prolamin as its main protein fraction. The isoelectric points of albumin, globulin, prolamin, and glutelin were at pH 3.6, 3.0, 4.4, and 3.4, respectively. Teff prolamin and glutelin showed a significant difference in amino acids and free energy of hydration compared to wheat gliadins and glutenins. The protein chain length of teff prolamins was smaller than that of wheat gliadins, and teff glutelins lacked high molecular weight glutelin subunits. Teff prolamin had the highest α-helices content (27.08%), whereas no random coils were determined, which is different from wheat gliadin. Teff glutelin had a lower content of β-turn than wheat glutenin, and no α-helices were determined in it. Teff prolamin and glutelin had lower disulfide bond content and surface hydrophobicity. Teff prolamin had significantly higher thermal stability than wheat gliadin, whereas the thermal stability of teff glutelin was significantly lower than that of wheat glutenin.

A label-free electrochemical immunosensor based on AuNPs/Zn/Ni-ZIF-8-800@graphene for the detection of wheat gliadin

A label-free electrochemical immunosensor based on AuNPs/Zn/Ni-ZIF-8-800@graphene for the detection of wheat gliadin

Unraveling the celiac disease-related immunogenic complexes in a set of wheat and tritordeum genotypes: implications for low-gluten precision breeding in cereal crops.

The development of low-gluten immunogenic cereal varieties is a suitable way to fight the increment of pathologies associated with the consumption of cereals. Although RNAi and CRISPR/Cas technologies were effective in providing low-gluten wheat, the regulatory framework, particularly in the European Union, is an obstacle to the short- or medium-term implementation of such lines. In the present work, we carried out a high throughput amplicon sequencing of two highly immunogenic complexes of wheat gliadins in a set of bread and durum wheat, and tritordeum genotypes. Bread wheat genotypes harboring the 1BL/1RS translocation were included in the analysis and their amplicons successfully identified. The number of CD epitopes and their abundances were determined in the alpha- and gamma-gliadin amplicons, including 40k-γ-secalin ones. Bread wheat genotypes not containing the 1BL/1RS translocation showed a higher average number of both alpha- and gamma-gliadin epitopes than those containing such translocation. Interestingly, alpha-gliadin amplicons not containing CD epitopes accounted for the highest abundance (around 53%), and the alpha- and gamma-gliadin amplicons with the highest number of epitopes were present in the D-subgenome. The durum wheat and tritordeum genotypes showed the lowest number of alpha- and gamma-gliadin CD epitopes. Our results allow progress in unraveling the immunogenic complexes of alpha- and gamma-gliadins and can contribute to the development of low-immunogenic varieties within precision breeding programs, by crossing or by CRISPR/Cas gene editing.

Comparison of intrinsic allergenicity potentials of gliadins from durum and soft white wheats in an adjuvant-free mouse model

Abstract Wheat is one of the major allergenic foods capable of eliciting life-threatening anaphylaxis. Discovering potential hypo/hyper-allergenic wheat classes is imperative to advance our knowledge and manage wheat allergy. Durum wheat (genome AABB) and soft white wheat (genome AABBDD) are two commonly consumed wheats. However, whether there are differences in the intrinsic allergenicity potential between them is unknown. Here, we tested the hypothesis that gliadins extracted from durum and soft white wheats will differ in their intrinsic allergenicity in an adjuvant-free mouse model that uses skin sensitization followed by intraperitoneal (IP) allergen challenge. Balb/c female mice were produced and maintained on a plant protein-free diet during this study. Groups of mice (n=5–10/group) were exposed to gliadins or vehicle via the skin once a week for 9 weeks. IgE responses were analyzed by ELISA to determine sensitization. Systemic anaphylaxis upon IP challenge was quantified by hypothermic shock response (HSR); mucosal mast cell response (MMCR) was quantified by measuring MMCP-1 in the blood. Our results suggest that mice exhibited robust, but comparable levels of specific IgE antibody responses after skin exposures to both wheat gliadins elicited. HSRs induced upon IP challenges with gliadins from the two wheats displayed strikingly similar kinetics. Interestingly, soft white wheat gliadin was significantly more potent in eliciting MMCR compared to the durum wheat gliadin. We demonstrate for the first-time the similarities and differences in intrinsic allergenicity potentials of gliadins obtained from the two wheats. Supported by grants from USDA/NIFA Hatch Project MICL02486 (Accession Number: 1012322)

The survey of prolamin and gluten content in beers produced in Central Europe – The biochemical characterization of immunoreactive protein fractions

Prolamins (gliadin-related proteins) are cereal proteins which are a source of polypeptides that are toxic to people showing intolerance or allergy to gluten. Therefore, serious safety concerns regarding occasional and routine beer consumption emerge due to the presence of immunoreactive amino acid sequences of cereal origin that remain in the final product. The aim of the study was to investigate the presence of prolamins and gluten in samples of beers (72 commercially available beverages) produced in Central Europe. A competitive ELISA and immunoblotting methods were applied to analyze the presence and concentration of immunoreactive proteins/peptides. Gluten level in the studied beers ranged from 10 to over 6000 mg/kg. Approximately 30% beers could be regarded as gluten-free, around 40% were very low gluten and only 25% beers contained considerable amounts of gluten. The highest level of prolamin content was detected in wheat beers. We demonstrated that these high concentrations of prolamins are probably derived from residues of non-degraded wheat gliadins.

Impact of chitosan and/or transglutaminase treatment on the colloidal stability and air-water interfacial properties of gliadin based nanoparticles

Wheat gliadin nanoparticles (GNPs) hold great potential as food ingredients. However, they have limited stability in aqueous systems as they precipitate rapidly in the presence of salt or at certain pH values. GNP modification strategies can increase their applicability in food systems. In this work, GNPs and hybrid gliadin-chitosan nanoparticles (GCNPs) were produced by liquid anti-solvent precipitation. For the first time ever, the impact of chitosan addition, both as such and in combination with microbial transglutaminase (TG) treatment to covalently conjugate protein and chitosan, on gliadin based NP stability and foaming properties was investigated. GCNPs had excellent colloidal stability over the course of 17 days of storage and in the presence of 1.5 M NaCl. This was attributed to the high chitosan-induced surface charge of GCNPs. Size exclusion HPLC revealed that TG treatment resulted in gliadin-chitosan conjugation, although no additional positive impact on GCNP stability was noted. At pH 4.5, the addition of charged chitosan resulted in worse GNP foaming properties, and TG had only a limited positive impact on the functionality. The worse foaming properties were attributed to the chitosan charged groups reducing mutual interactions of nanoparticle constituents resulting in a weaker adsorbed interfacial film. Even though GCNPs possessed poor foaming properties, they still hold great potential due to their excellent colloidal stability under food-system relevant conditions.

Effect of ultraviolet irradiation on immunoreactivity and other protein characteristics of wheat gliadin in flour and flatbread

Pulsed light (PL) was investigated for reducing the immunoreactivity of gliadin of wheat flour, however, the obstacle with using PL light was that the food temperature was highly increased with a short treatment time. Therefore, ultraviolet (UV) irradiation was used to study its effects on immunoreactivity of gliadin, free sulfhydryl groups, gluten, and molecular weight of wheat proteins in wheat flour and flatbread samples. Also, the effect of heat treatment combined with UV light treatment on some protein features were studied. The immunoreactivity of gliadin was highly reduced, 60%, of flour treated with only UV, while the reduction was not obvious for flour treated with infrared light along with UV light and for flatbread samples. The free sulfhydryl groups were 3030, 3878, 4372, and 4784 µmol.g-1 after zero, 30, 60, and 120 min of UV light respectively. While the free sulfhydryl groups were reduced for flatbread samples treated by UV light. SDS-PAGE results showed that there was a clear reduction of the gliadin bands of flour treated with UV light compared to other treatments. In conclusion, thermal treatment along with or before UV light treatment reduced the effect of UV light on the immunoreactivity of wheat gliadin.

Wheat quality: A review on chemical composition, nutritional attributes, grain anatomy, types, classification, and function of seed storage proteins in bread making quality.

Wheat (Triticum aestivum L.) belonging to one of the most diverse and substantial families, Poaceae, is the principal cereal crop for the majority of the world's population. This cereal is polyploidy in nature and domestically grown worldwide. Wheat is the source of approximately half of the food calories consumed worldwide and is rich in proteins (gluten), minerals (Cu, Mg, Zn, P, and Fe), vitamins (B-group and E), riboflavin, niacin, thiamine, and dietary fiber. Wheat seed-storage proteins represent an important source of food and energy and play a major role in the determination of bread-making quality. The two groups of wheat grain proteins, i.e., gliadins and glutenins, have been widely studied using SDS-PAGE and other techniques. Sustainable production with little input of chemicals along with high nutritional quality for its precise ultimate uses in the human diet are major focus areas for wheat improvement. An expansion in the hereditary base of wheat varieties must be considered in the wheat breeding program. It may be accomplished in several ways, such as the use of plant genetic resources, comprising wild relatives and landraces, germplasm-assisted breeding through advanced genomic tools, and the application of modern methods, such as genome editing. In this review, we critically focus on phytochemical composition, reproduction growth, types, quality, seed storage protein, and recent challenges in wheat breeding and discuss possible ways forward to combat those issues.

Gliadin Nanoparticles Containing Doxorubicin Hydrochloride: Characterization and Cytotoxicity.

Doxorubicin hydrochloride (DOX) is a well-known antitumor drug used as first line treatment for many types of malignancies. Despite its clinical relevance, the administration of the compound is negatively affected by dose-dependent off-target toxicity phenomena. Nanotechnology has helped to overcome these important limitations by improving the therapeutic index of the bioactive and promoting the translation of novel nanomedicines into clinical practice. Herein, nanoparticles made up of wheat gliadin and stabilized by polyoxyethylene (2) oleyl ether were investigated for the first time as carriers of DOX. The encapsulation of the compound did not significantly affect the physico-chemical features of the gliadin nanoparticles (GNPs), which evidenced a mean diameter of ~180 nm, a polydispersity index < 0.2 and a negative surface charge. The nanosystems demonstrated great stability regarding temperature (25−50 °C) and were able to retain high amounts of drug, allowing its prolonged and sustained release for up to a week. In vitro viability assay performed against breast cancer cells demonstrated that the nanoencapsulation of DOX modulated the cytotoxicity of the bioactive as a function of the incubation time with respect to the free form of the drug. The results demonstrate the potential use of GNPs as carriers of hydrophilic antitumor compounds.