Walnut Protein: A Rising Source of High-Quality Protein and Its Updated Comprehensive Review

Effect of succinylation-assisted glycosylation on the structural characteristics, emulsifying, and gel properties of walnut glutenin

In this study, we examined the effects of various sodium alginate (ALG) concentrations (0.2%-0.8%) on the functional and physicochemical characteristics of succinylated walnut glutenin (GLU-SA). The results showed that acylation decreased the particle size and zeta potential of walnut glutenin (GLU) by 122- and 0.27-fold, respectively. In addition, the protein structure unfolded, providing conditions for glycosylation. After GLU-SA was combined with ALG, the surface hydrophobicity decreased and the net negative charge and disulfide bond content increased. The protein structure was analyzed by FTIR, Endogenous fluorescence spectroscopy, and SEM, and ALG prompted GLU-SA cross-linking to form a stable three-dimensional network structure. The results indicated that dual modification improved the functional properties of the complex, especially its potential protein gel and emulsifying properties. This research provide theoretical support and a technical reference for expanding the application of GLU in the processing of protein and oil products.

Modulation of cecal microbiota and fecal metabolism in mice by walnut protein

Walnut meal is a by-product of walnut oil pressing, in which the protein content is more than 40%, which is an excellent food raw material, but at present, it is basically used as animal feed or discarded, which results in a great waste of resources, and its modulating effect on the intestinal microbiota is not clear. In this study, we used supercritically extracted walnut meal as a raw material, prepared walnut meal isolate protein (WP) by alkaline extraction and acid precipitation, and systematically analyzed its structure by Fourier infrared spectroscopy (FTIR), Raman spectroscopy (Raman), and scanning electron microscopy (SEM); meanwhile, we explored the effects of WP on the cecal bacterial flora and fecal metabolites of mice by microbiological and metabolomic techniques. The results showed that the protein content of WP prepared using alkaline extraction and acid precipitation was as high as 83.7%, in which arginine and glutamic acid were abundant, and it has the potential to be used as a raw material for weight-loss meal replacement food; FTIR and Raman analyses showed that the absorption peaks of WP's characteristic functional groups were obvious, and that the content of the α-helix and β-fold in the secondary structure was greater than 30%, which indicated that it was structurally stable; differential scanning calorimetry (DSC) and SEM analyses showed that WP is a typical spherical particle, its denaturation temperature is 73.6 °C, and it has good thermal stability. Supplementation of WP significantly altered the composition of the intestinal flora in mice, with an increase in beneficial bacteria and a decrease in harmful bacteria; the strongest modulation of the intestinal flora was achieved by altering the composition of the intestinal flora and by increasing the number of Akkermansia (p < 0.01), which consequently affects the function of the microbiota. Based on LC-MS metabolomic results, we identified a total of 87 WP-regulated metabolites, mainly enriched in the bile secretion pathway, which had the highest relevance, followed by benzoxazine biosynthesis. In summary, walnut protein is an important plant protein and has a positive impact on intestinal health, which may provide new ideas for the development of functional foods.

Walnut peptide alleviates obesity, inflammation and dyslipidemia in mice fed a high-fat diet by modulating the intestinal flora and metabolites

Introduction

Obesity is a chronic disease in which the body stores excess energy in the form of fat, and intestinal bacterial metabolism and inflammatory host phenotypes influence the development of obesity. Walnut peptide (WP) is a small molecule biopeptide, and the mechanism of action of WP against metabolic disorders has not been fully elucidated. In this study, we explored the potential intervention mechanism of WP on high-fat diet (HFD)-induced obesity through bioinformatics combined with animal experiments.

Methods

PPI networks of Amino acids and their metabolites in WP (AMWP) and "obesity" and "inflammation" diseases were searched and constructed by using the database, and their core targets were enriched and analyzed. Subsequently, Cytoscape software was used to construct the network diagram of the AMWP-core target-KEGG pathway and analyze the topological parameters. MOE2019.0102 was used to verify the molecular docking of core AMWP and core target. Subsequently, an obese Mice model induced by an HFD was established, and the effects of WP on obesity were verified by observing weight changes, glucose, and lipid metabolism levels, liver pathological changes, the size of adipocytes in groin adipose tissue, inflammatory infiltration of colon tissue, and intestinal microorganisms and their metabolites.

Results

The network pharmacology and molecular docking showed that glutathione oxide may be the main active component of AMWP, and its main targets may be EGFR, NOS3, MMP2, PLG, PTGS2, AR. Animal experiments showed that WP could reduce weight gain and improve glucose-lipid metabolism in HFD-induced obesity model mice, attenuate hepatic lesions reduce the size of adipocytes in inguinal adipose tissue, and reduce the inflammatory infiltration in colonic tissue. In addition, the abundance and diversity of intestinal flora were remodeled, reducing the phylum Firmicutes/Bacteroidetes (F/B) ratio, while the intestinal mucosal barrier was repaired, altering the content of short-chain fatty acids (SCFAs), and alleviating intestinal inflammation in HFD-fed mice. These results suggest that WP intervenes in HFD-induced obesity and dyslipidemia by repairing the intestinal microenvironment, regulating flora metabolism and anti-inflammation.

Discussion

Our findings suggest that WP intervenes in HFD-induced obesity and dyslipidemia by repairing the intestinal microenvironment, regulating flora metabolism, and exerting anti-inflammatory effects. Thus, WP may be a potential therapeutic strategy for preventing and treating metabolic diseases, and for alleviating the intestinal flora disorders induced by these diseases. This provides valuable insights for the development of WP therapies.