Heat-induced amyloid-like aggregation of β-lactoglobulin regulated by glycation: A comparison of five kinds of reducing saccharides

Fish oil emulsions stabilized by enzymatic hydrolysis, glycation, and fibrillation of β-Lg: Stability and EPA/DHA bioaccessibility

This study investigated the stabilization mechanism, storage stability, and in vitro digestion characteristics of oil-in-water fish oil emulsions stabilized by β-Lg modified through enzymatic hydrolysis, glycation, and fibrillation. The stabilization mechanism was elucidated by comparing droplet size, ζ-potential, interfacial protein thickness, and microstructure. Results showed that β-Lg modified through these combined processes formed a three-dimensional network, providing superior stabilization, while other modified proteins stabilized emulsions via surface adsorption. Emulsion stabilized by combined modified β-Lg maintained z-average particle sizes below 550 nm, delayed the peroxide value peak by 3 days, reduced TBARS content by 0.5 μg/mL, and remained unstratified for up to 50 days. During simulated in vitro digestion, emulsions exhibited greater stability in the gastric phase but destabilized in the intestinal phase, leading to 10.46 % higher EPA/DHA bioaccessibility than those emulsions stabilized by untreated β-Lg.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Micellar delivery systems of bioactive compounds for precision nutrition

Rapid changes in lifestyle and the increasingly hectic pace of life have led to a rise in chronic diseases, such as obesity, inflammatory bowel disease, liver disease, and cancer, posing significant threats to public health. In response to these challenges, precision nutrition (PN) has emerged as a secure and effective intervention aiming at human health and well-being. Bioactive compounds (bioactives), including carotenoids, polyphenols, vitamins, and polyunsaturated fatty acids, exhibit a range of beneficial properties, e.g., antioxidant and anti-inflammatory effects. These properties make them promising candidates for preventing or treating chronic diseases and promoting human health. However, bioactives might have different challenges when incorporated into food matrices and oral administration, including low water solubility, poor physiochemical stability, and low absorption efficiency. This limits them to achieve the health benefits in the body. Numerous strategies have been developed and utilized to encapsulate and deliver bioactives. Micellar delivery systems, due to their unique core-shell structure, play a pivotal role in improving the stability, solubility, and bioavailability of these bioactives. Moreover, through innovative design strategies, micellar delivery systems can be tailored to offer targeted and controlled release, thus maximizing the potential of bioactives in PN applications. This chapter reveals details about the preparation methods and properties of micelles and highlights the strategies to modulate the properties of polymeric micelles. Afterwards, the application of polymeric micelles in the delivery of bioactives and the corresponding PN, including controlled release, organ-targeting ability, and nutritional intervention for chronic disease are summarized.

Changes in glycated myofibrillar proteins conformation on the formation of Nε-carboxymethyllysine under gradient thermal conditions

N^ε-carboxymethyllysine (CML), a frequently used marker of advanced glycation end products (AGEs) in food, was generated in food processing easily and caused changes in myofibrillar proteins (MPs) characterization. The relevance between glycosylated MPs structure alternation and CML formation under thermal conditions have been reported. However, the correlation mechanism was not clear yet. In this work, the influence of gradient heating (50℃, 60℃, 70℃, 80℃, and 90℃) on the different degrees of glycated MPs, which determined the correlation with CML formation in protein structural changes of MPs. In the rising stage of the CML level, glycation accelerated the fibrillation and aggregation behavior of MPs during heating and increased surface hydrophobicity and particle size. The protein cross-linking affected the protein modification caused by heating and glycation. This work highlights the substantial influences of glycosylation and thermal treatments on MPs, which transformed the MPs structural characteristics and CML level.

Glycation of Whey Proteins Increases the Ex Vivo Immune Response of Lymphocytes Sensitized to β-Lactoglobulin

Glycation is a spontaneous reaction accompanying the thermal processing and storage of food. It can lead to changes in the allergenic and immunogenic potential of protein. This study aimed to evaluate the effect of the glycation of α-lactalbumin and β-lactoglobulin (β-lg) on the ex vivo response of β-lg sensitized lymphocytes. C57BL/6 mice were immunized intragastrically (i-g) or intraperitoneally (i-p) with β-lg. The humoral response of the groups differed only with respect to the IgE level of the i-p group. Cellular response was studied after stimulation with antigen variants. The lymphocytes from the i-g/group mesenteric lymph nodes, stimulated with β-lg before and after glycation, presented a higher percentage of CD4 and CD8 T cells compared to the i-p/group. The cytokine profile of the i-p/group splenocytes stimulated with antigens showed elevated levels of pro-inflammatory IL-17A regardless of protein modification. In conclusion, the ex vivo model proved that the glycation process does not reduce protein immunogenicity.

Nanofibrils of food-grade proteins: Formation mechanism, delivery systems, and application evaluation

Due to the high aspect ratio, appealing mechanical characteristics, and various adjustable functional groups on the surface proteins, food-grade protein nanofibrils have attracted great research interest in the field of food science. Fibrillation, known as a process of peptide self-assembly, is recognized as a common attribute for food-grade proteins. Converting food-grade proteins into nanofibrils is a promising strategy to broaden their functionality and applications, such as improvement of the properties of gelling and emulsifying, especially for constructing various delivery systems for bioactive compounds. Protein source and processing conditions have a great impact on the size, structure, and morphology of nanofibrils, resulting in extreme differences in functionality. With this feature, it is possible to engineer nanofibrils into four different delivery systems, including gels, microcapsules, emulsions, and complexes. Construction of nanofibril-based gels via multiple cross-linking methods can endow gels with special network structures to efficiently capture bioactive compounds and extra mechanical behavior. The adsorption behavior of nanofibrils at the interface is highly complex due to the influence of several intrinsic factors, which makes it challenging to form stabilized nanofibril-based emulsion systems. Based on electrostatic interactions, microcapsules and complexes prepared using nanofibrils and polysaccharides have combined functional properties, resulting in adjustable release behavior and higher encapsulation efficiency. The bioactive compounds delivery system based on nanofibrils is a potential solution to enhance their absorption in the gastrointestinal tract, improve their bioavailability, and deliver them to target organs. Although food-grade protein nanofibrils show unknown toxicity to humans, further research can contribute to broadening the application of nanofibrils in delivery systems.

Receptor Mediated Effects of Advanced Glycation End Products (AGEs) on Innate and Adaptative Immunity: Relevance for Food Allergy

As of late, evidence has been emerging that the Maillard reaction (MR, also referred to as glycation) affects the structure and function of food proteins. MR induces the conformational and chemical modification of food proteins, not only on the level of IgG/IgE recognition, but also by increasing the interaction and recognition of these modified proteins by antigen-presenting cells (APCs). This affects their biological properties, including digestibility, bioavailability, immunogenicity, and ultimately their allergenicity. APCs possess various receptors that recognize glycation structures, which include receptor for advanced glycation end products (RAGE), scavenger receptors (SRs), galectin-3 and CD36. Through these receptors, glycation structures may influence the recognition, uptake and antigen-processing of food allergens by dendritic cells (DCs) and monocytes. This may lead to enhanced cytokine production and maturation of DCs, and may also induce adaptive immune responses to the antigens/allergens as a result of antigen uptake, processing and presentation to T cells. Here, we aim to review the current literature on the immunogenicity of AGEs originating from food (exogenous or dietary AGEs) in relation to AGEs that are formed within the body (endogenous AGEs), their interactions with receptors present on immune cells, and their effects on the activation of the innate as well as the adaptive immune system. Finally, we review the clinical relevance of AGEs in food allergies.

Milk Processing Affects Structure, Bioavailability and Immunogenicity of β-lactoglobulin

Bovine milk is subjected to various processing steps to warrant constant quality and consumer safety. One of these steps is pasteurization, which involves the exposure of liquid milk to a high temperature for a limited amount of time. While such heating effectively ameliorates consumer safety concerns mediated by pathogenic bacteria, these conditions also have an impact on one of the main nutritional whey constituents of milk, the protein β-lactoglobulin. As a function of heating, β-lactoglobulin was shown to become increasingly prone to denaturation, aggregation, and lactose conjugation. This review discusses the implications of such heat-induced modifications on digestion and adsorption in the gastro-intestinal tract, and the responses these conformations elicit from the gastro-intestinal immune system.

Effect of reaction temperature on the protein structure and the ability to encapsulate β-carotene of WPI-dextran conjugates

In this paper, we studied the effect of glycosylation reaction on the molecular structure and functional properties of whey protein isolate (WPI), and studied the effect of reaction temperature (50 to 90 °C) on the molecular structure and functional properties of WPI-dextran conjugates (WPI-D). The results of the extent of glycation (EG) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the formation of WPI-D. Circular dichroism (CD), Fourier transform infrared spectrum, and fluorescence spectroscopy indicated that the molecular structure of WPI was changed after glycosylation-the β-sheet content was decreased and the tryptophan content was increased. The emulsifying properties and the ability to encapsulate β-carotene of WPI-D were improved compared with WPI (P < 0.05). When the reaction temperature was 70 and 80 °C, the EG and the ability to encapsulate β-carotene of WPI-D were better (P < 0.05), which was related to protein unfolding. However, due to the polymerization between the WPI molecules, the emulsion activity index of WPI-D and the ability to encapsulate β-carotene were lowered at 90 °C (P < 0.05). Therefore, the glycosylation reaction can change the molecular structure and functional properties of WPI; the emulsifying properties and the ability to encapsulate β-carotene of WPI-D can be changed by controlling the reaction temperature of glycosylation. PRACTICAL APPLICATION: The glycosylation reaction can change the molecular structure and functional properties of Whey protein isolate; the emulsifying properties and the ability to encapsulate β-carotene of WPI-dextran conjugates can be changed by controlling the reaction temperature of glycosylation.

Heat-induced amyloid-like aggregation of β-lactoglobulin affected by glycation by α-dicarbonyl compounds in a model study

BACKGROUND

α-Dicarbonyl compounds are widely generated in the Maillard reaction, caramelization and oil oxidation during heat treatment. These compounds can readily react with lysine and arginine residues of a protein, whereas the influence of these compounds on protein structure and quality has seldom been revealed. This study compared influence of glycation by glucose and α-dicarbonyl compounds on amyloid-like aggregation of β-lactoglobulin (β-LG), both fibrillation kinetics and conformation of aggregates were studied.

RESULTS

Compared with glycation by glucose, the glycation by α-dicarbonyl compounds resulted in faster reduction of free amino group, sulfydryl group, and the relative content of β-sheet secondary structure, according to the ultraviolet (UV) spectra or circular dichroism (CD) spectra results. Based on the analysis of fibrillation kinetics using thioflavin T (ThT) binding assay, the glycation by α-dicarbonyls were more efficient in suppressing the growth of fibrillar aggregates. In addition, glycation by α-dicarbonyl resulted in amorphous oligomers, which were compared with the amyloid-like aggregates in control and glucose-glycated samples, based on the transmission electron microscopy (TEM) observation.

CONCLUSIONS

Glycation by α-dicarbonyl compounds induced larger decline in the β-sheet structure of β-LG than glycation by glucose, and thus largely suppressed the amyloid-like aggregation of β-LG and changed the morphology of aggregates. © 2019 Society of Chemical Industry.

Characteristics and influencing factors of amyloid fibers in S. mutans biofilm

There are signs that amyloid fibers exist in Streptococcus mutans biofilm recently. However, the characteristics of amyloid fibers and fibrillation influencing factors are unknown. In this study, we firstly used transmission electron microscopy (TEM) and atomic force microscopy (AFM) to observe the morphology of amyloid fibers in S. mutans. Then the extracted amyloid fibers from biofilm were studied for their characteristics. Further, the influencing factors, PH, temperature and eDNA, were investigated. Results showed there were mainly two morphologies of amyloid fibers in S. mutans, different in width. Amyloid fibers inhibitor-EGCG obviously destroyed biofilm at different stages, which is dose-dependent. The amount of amyloid fibers positively correlated with biofilm biomass in clinical isolates. Acidic pH and high temperature obviously accelerated amyloid fibrillation. During amyloid fibrillation, amyloid growth morphologies were observed by TEM and results showed two growth morphologies. Amyloid fibers formed complex with eDNA, which we call (a)eDNA. The molecular weight of (a)eDNA was similar to genomic DNA, greatly larger than that of eDNA in matrix. Combined use of DNase I and EGCG was more efficiently in inhibiting amyloid fibers and biofilm biomass. In conclusion, amyloid fibers are the crucial structures for S. mutans biofilm formation, showing two types of morphology. Acidic pH and temperature can obviously accelerate amyloid fibrillation. Amyloid fibers form complex with (a)eDNA and combined use of DNase and amyloid fiber inhibitor is more efficiently in inhibiting S. mutans biofilm formation.