Functions and Applications of Bioactive Peptides From Corn Gluten Meal

Corn Peptides Alleviate Nonalcoholic Fatty Liver Fibrosis in Mice by Inhibiting NLRP3 Inflammasome Activation and Regulating Gut Microbiota

This study aimed to investigate the effects of corn gluten-derived soluble epoxide hydrolase (sEH) inhibitory peptides on nonalcoholic fatty liver fibrosis induced by a high-fat diet and carbon tetrachloride in mice. Mice treated with corn peptides at doses of 500 or 1000 mg/kg/d for 4 weeks exhibited reduced sEH activity in serum and liver, enhanced lipid metabolism, and decreased lipid accumulation and oxidative stress. Corn peptides effectively downregulated the mRNA levels of Pro-IL-1β, Pro-IL-18, NOD-like receptor protein 3 (NLRP3), ASC, Pro-caspase-1, Caspase-1, and GSDMD in the liver. This hepatoprotective effect of corn peptides by inhibiting NLRP3 inflammasome activation was further validated in H2O2-induced HepG2 cells. Moreover, corn peptides restored the composition of the gut microbiota and promoted short-chain fatty acid production. This study provides evidence that corn-derived sEH inhibitory peptides have hepatoprotective activity against nonalcoholic fatty liver fibrosis by suppressing NLRP3 inflammasome activation and modulating gut microbiota.

Role of Corn Peptide Powder in Lipopolysaccharide-Induced Inflammatory Responses in 3T3-L1 Adipocytes

Corn peptide (CP) is a short, naturally occurring, and physiologically active peptide generated from corn-protease-catalyzed hydrolysis. CP plays a role in preventing obesity-related disorders, but its impact on reducing inflammation is unknown. Hence, this study examined the possible protective effects of corn peptide powder (CPP) against the harmful effects of lipopolysaccharide (LPS), with a particular emphasis on reducing oxidative damage and inflammation in adipocytes. Hence, mature 3T3-L1 adipocytes underwent exposure to 10 ng/mL LPS, with or without CPP (10 and 20 μg/mL). LPS stimulation increased reactive oxygen species and superoxide anion generation. However, this effect was reduced in a dose-dependent manner by pretreatment with CPP. CPP treatment elevated the mRNA expressions of the antioxidant enzymes manganese superoxide dismutase (mnSOD) and glutathione peroxidase 1 (Gpx1) while reducing the mRNA expressions of the cytosolic reactive oxygen species indicators p40 and p67 (NADPH oxidase 2). In addition, CPP inhibited the monocyte chemoattractant protein-1, tumor necrosis factor-alpha, Toll-like receptor 4, and nuclear factor kappa B mRNA expressions induced by LPS. These findings demonstrate that CPP may ameliorate adipocyte dysfunction by suppressing oxidative damage and inflammatory responses through a new mechanism known as Toll-like receptor 4/nuclear factor kappa B-mediated signaling.

Corn peptides attenuate non-alcoholic fatty liver disease via PINK1/Parkin-mediated mitochondrial autophagy

Background

Corn peptides, a novel food prepared from corn gluten meal (CGM) by enzymatic hydrolysis or microbial fermentation, have attracted considerable interest owing to their various bioactive properties. However, the underlying mechanism of corn peptides attenuate non-alcoholic fatty liver disease (NAFLD) remains unclear.

Objective

This study aimed to investigate the effect of corn peptides in NAFLD and to decipher the underlying mechanisms.

Design

NAFLD was induced by a high-fat diet (HFD) for 10 weeks. Corn peptides were administered during the period. Human hepatocellular carcinomas (HepG2) cells induced by free fatty acids were used for this mechanism study.

Results

Corn peptides alleviated HFD-induced histopathological changes, disorders of lipid metabolism, and mitochondrial damage. Moreover, corn peptides blocked mitophagy suppression by HFD based on the increased LC3, ATG7 expressions, as well as decreased P62 levels. Corn peptides increased the expression of proteins involved in fatty acid β-oxidation, such as PPARα and PGC-1α. Corn peptides also improved the Ser/Thr kinase PINK1 (PINK1) and the E3 ubiquitin ligase Parkin (Parkin) translocation to mitochondria, which is confirmed by immunofluorescence. Furthermore, stable knockdown of PINK1 by PINK1 SiRNA in HepG2 inhibited PINK1-Parkin-associated mitophagy and resulted in lipid accumulation.

Conclusion

Corn peptides improved cell injury and ameliorated mitochondrial dysfunction and lipid accumulation via PINK1/Parkin-mediated autophagy in NAFLD. Thus, corn peptides could be a promising nutritional molecule with natural functions for preventing NAFLD.

Nutritional, bioactive components and health properties of the milpa triad system seeds (corn, common bean and pumpkin)

The milpa system is a biocultural polyculture technique. Heritage of Mesoamerican civilizations that offers a wide variety of plants for food purposes. Corn, common beans, and pumpkins are the main crops in this agroecosystem, which are important for people's nutritional and food security. Moreover, milpa system seeds have great potential for preventing and ameliorating noncommunicable diseases, such as obesity, dyslipidemia, type 2 diabetes, among others. This work reviews and analyzes the nutritional and health benefits of milpa system seeds assessed by recent preclinical and clinical trials. Milpa seeds protein quality, vitamins and minerals, and phytochemical composition are also reviewed. Evidence suggests that regular consumption of milpa seeds combination could exert complementing effect to control nutritional deficiencies. Moreover, the combination of phytochemicals and nutritional components of the milpa seed could potentialize their individual health benefits. Milpa system seeds could be considered functional foods to fight nutritional deficiencies and prevent and control noncommunicable diseases.

In vitro and in silico studies for the identification of anti-cancer and antibacterial peptides from camel milk protein hydrolysates

Today, breast cancer and infectious diseases are very worrying that led to a widespread effort by researchers to discover natural remedies with no side effects to fight them. In the present study, we isolated camel milk protein fractions, casein and whey proteins, and hydrolyzed them using pepsin, trypsin, and both enzymes. Screening of peptides with anti-breast cancer and antibacterial activity against pathogens was performed. Peptides derived from whey protein fraction with the use of both enzymes showed very good activity against MCF-7 breast cancer with cell viability of 7.13%. The separate use of trypsin and pepsin to digest whey protein fraction yielded peptides with high antibacterial activity against S. aureus (inhibition zone of 4.17 ± 0.30 and 4.23 ± 0.32 cm, respectively) and E. coli (inhibition zone of 4.03 ± 0.15 and 4.03 ± 0.05 cm, respectively). Notably, in order to identify the effective peptides in camel milk, its protein sequences were retrieved and enzymatically digested in silico. Peptides that showed both anticancer and antibacterial properties and the highest stability in intestinal conditions were selected for the next step. Molecular interaction analysis was performed on specific receptors associated with breast cancer and/or antibacterial activity using molecular docking. The results showed that P3 (WNHIKRYF) and P5 (WSVGH) peptides had low binding energy and inhibition constant so that they specifically occupied active sites of protein targets. Our results introduced two peptide-drug candidates and new natural food additive that can be delivered to further animal and clinical trials.

Preparation and identification of a novel peptide with high antioxidant activity from corn gluten meal

The antioxidant activity of corn peptides is related to their molecular weight and structure. Corn gluten meal (CGM) was hydrolyzed using a combination of Alcalase, Flavorzyme and Protamex, and the hydrolysates were subjected to antioxidant activity analysis after further fractionation. Corn peptides with molecular weights less than 1 kDa (CPP1) exhibited excellent antioxidant activity. A novel peptide, Arg-Tyr-Leu-Leu (RYLL), was identified from CPP1. RYLL displayed preferable scavenging capacities for ABTS radicals and DPPH radicals, with IC₅₀ values of 0.122 mg/ml and 0.180 mg/ml, respectively. Based on quantum calculations, RYLL had multiple antioxidant active sites, and tyrosine was the main active site due to the highest energy of the highest occupied molecular orbit (HOMO). Moreover, the simple peptide structure and hydrogen bond network of RYLL contributed to the exposure of the active site. This study elucidated the antioxidant mechanism of corn peptides, which could provide an understanding for CGM hydrolysates as natural antioxidants.

Walnut (Juglans regia L.) Oligopeptides Alleviate Alcohol-Induced Acute Liver Injury through the Inhibition of Inflammation and Oxidative Stress in Rats

The study was aimed at investigating the effects of walnut oligopeptides (WOPs) on alcohol-induced acute liver injury and its underlying mechanisms. Male Sprague Dawley (SD) rats were randomly assigned to six groups: normal control, alcohol control, whey protein (440 mg/kg.bw), and three WOPs (220 mg/kg.bw, 440 mg/kg.bw, 880 mg/kg.bw) groups. After 30 days of gavage, ethanol with a volume fraction of 50%, administered at a dose of 7 g/kg.bw., caused acute liver injury. A righting reflex experiment and a blood ethanol concentration evaluation were then performed. Serum biochemical parameters, inflammatory cytokines, liver alcohol metabolism enzymes, oxidative stress biomarkers, liver nuclear factor-κB (NF-κB p65), and cytochrome P4502E1 expression were determined. The results revealed that the intervention of 440 mg/kg and 880 mg/kg WOPs could alleviate the degree of intoxication, decrease blood ethanol concentration, alleviate alcohol-induced hepatic steatosis, enhance the activity of hepatic ethanol metabolizing enzymes and antioxidant capacity, reduce lipid oxidation products and pro-inflammatory factor contents, and inhibit the expression of NF-κBp65 in the livers of rats. The outcomes of the study suggest that WOPs have beneficial effects on liver damage caused by acute ethanol binge drinking, with the high-dose WOPs (880 mg/kg.bw) exerting the most pronounced hepatoprotective effect.

Mycotoxin risk management in maize gluten meal

Maize gluten meal (MGM) is a by-product of maize starch and ethanol, produced by the wet milling process. Its high protein content makes it a preferred ingredient in feed. Given the high prevalence of mycotoxins in maize globally, they pose a significant challenge to use of MGM for feed: wet milling could concentrate certain mycotoxins in gluten components, and mycotoxin consumption affects animal health and can contaminate animal-source foods. To help confront this issue, this paper summarizes mycotoxin occurrence in maize, distribution during MGM production and mycotoxin risk management strategies for MGM through a comprehensive literature review. Available data emphasize the importance of mycotoxin control in MGM and the necessity of a systematic control approach, which includes: good agriculture practices (GAP) in the context of climate change, degradation of mycotoxin during MGM processing with SO2 and lactic acid bacteria (LAB) and the prospect of removing or detoxifying mycotoxins using emerging technologies. In the absence of mycotoxin contamination, MGM represents a safe and economically critical component of global animal feed. With a holistic risk assessment-based, seed-to-MGM-feed systematic approach to reducing and decontaminating mycotoxins in maize, costs and negative health impacts associated with MGM use in feed can be effectively reduced.

Relation of amino acid composition, hydrophobicity, and molecular weight with antidiabetic, antihypertensive, and antioxidant properties of mixtures of corn gluten and soy protein hydrolysates

New mixed Alcalase-hydrolysates were developed using corn gluten meal (CP) and soy protein (SP) hydrolysates, namely CPH, SPH, SPH30:CPH70, SPH70:CPH30, and SPH50:CPH50. Amino acid profile, surface hydrophobicity (H 0), molecular weight (MW) distribution, antioxidant activity, angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase inhibitory activities, and functional characteristics of hydrolysates were determined. Hydrolysis changed the amount of hydrophilic and hydrophobic amino acid composition and significantly increased the H 0 values of hydrolysates, especially for CPH. The DPPH radical scavenging activity (RSA) was higher for CPH, SPH30:CPH70, and SPH50:CPH50 than SPH and SPH70:CPH30. Moreover, SPH, SPH70:CPH30, and SPH50:CPH50 showed lower MW than CPH, and this correlated with the higher hydrophilicity, and ABTS and hydroxyl RSA values obtained for SPH and the mixed hydrolysates with predominantly SPH. SPH70:CPH30 exhibited higher ACE, α-glucosidase, and α-amylase inhibitory activities among all samples due to its specific peptides with high capacity to interact with amino acid residues located at the enzyme active site and also low binding energy. At 15% degree of hydrolysis, both SPH and CPH showed enhanced solubility at pH 4.0, 7.0 and 9.0, emulsifying activity, and foaming capacity. Taken together, SPH70:CPH30 displayed strong antioxidant, antihypertensive, and antidiabetic attributes, emulsifying activity and stability indexes, and foaming capacity and foaming stability, making it a promising multifunctional ingredient for the development of functional food products.

Development and Utilization of Corn Processing by-Products: A Review

As an important food crop, corn has an important impact on people's lives. The processing of corn produces many by-products, such as corn gluten meal, corn husk, and corn steep liquor, which are rich in protein, oil, carbohydrates, and other nutrients, all of which are inexpensive. Their accumulation in large quantities during the production process not only results in a burden on the environment but also the loss of potentially valuable food materials that can be processed. In fact, the by-products of corn processing have been partially used in functional foods, nutrients, feed, and other industries. There is no doubt that the secondary utilization of these by-products can not only solve the problem of waste pollution caused by them, but also produce high value-added products and improve the economic benefits of corn. This paper describes in detail the processing and higher-value utilization of the five main by-products: corn gluten meal, corn husks, corn steep liquor, corn germ, and fuel ethanol by-product. The utilization status of corn processing by-products was discussed roundly, and the development trend of corn processing by-products in China and other countries was analyzed, which provided the reference for the development of the corn deep processing industry.

Application of Solid-State Fermentation for the Improving of Extruded Corn Dry-Milling By-Products and Their Protein Functional Properties

In this study, the effect of solid-state fermentation (SSF) with Lactobacillus sakei MI401 and Pediococcus acidilactici PA-2 strains on functional properties of extruded (130 °C; 25 rpm) corn-milling by-products (CMB) and their albumin, globulin, and prolamin fractions was evaluated in order to produce stabilized and functionalized food/feed stock. Extrusion resulted in a considerable reduction of microbial contamination of CMB by five log cycles, increased damaged starch, water-absorption capacity, and lowered protein and fat contents by 12.4% and 37%, respectively. The application of SSF for the extruded CMB have been shown to improve the water absorption, foaming, and emulsifying capacity of albumins and globulins and also increased the digestibility and free radical scavenging activity of prolamins. The essential amino acid content (EAA) in CMB and antioxidant activity of prolamins was lowered after extrusion but significantly increased after SSF. The combination of the abovementioned treatments can be confirmed as a prospective functionalization of CMB, capable of potentially enhancing its safety and improving nutritional, biochemical, and technological properties of proteins.

The anti-fatigue activity of corn peptides and their effect on gut bacteria

BACKGROUND

Corn peptides (CPs) are rich in branched-chain amino acids such as leucine and have a variety of biological activities such as antioxidant and improved lipid distribution. In this article, we prepared CPs by enzymatic digestion of corn proteins and evaluated their anti-fatigue activity.

RESULTS

We evaluated the anti-fatigue effect of CPs through an exhaustive swimming experiment. The results showed that CPs were able to significantly reduce the rate of body weight gain and prolong the duration of exhaustive swimming. Besides, CPs reduced blood urea nitrogen (BUN) levels after exercise, while they significantly increased muscle glycogen and liver glycogen stores. They reduced muscle cell damage from exercise. In addition, CPs were effective in increasing AMPK, PGC-1α and PI3K protein expression levels and promoting Akt phosphorylation. Correlation analysis showed that CPs increased the abundance of probiotics such as Lactobacillus and Akkermansia in the gut microflora.

CONCLUSION

CPs, which enhanced exercise performance in mice and could modulate gut microbial composition, had significant anti-fatigue activity. © 2021 Society of Chemical Industry.

Corn peptides improved obesity-induced non-alcoholic fatty liver disease through relieving lipid metabolism, insulin resistance and oxidative stress

Non-alcoholic fatty liver disease (NAFLD) is increasingly threatening human health. The remarkable effects of corn peptides (CPs) as bioactive peptides on liver protection have attracted much attention. Nevertheless, the specific effect of CPs on NAFLD remains unclear. The present study was designed to investigate the efficacy of CPs in the prevention and auxiliary treatment of high-fat diet (HFD)-induced NAFLD in SD rats, and puerarin was used as the positive control. SD rats were fed a high-fat diet to establish the NAFLD rat model, and LO2 cells were treated with a high concentration of fructose to simulate the NAFLD cell model. NAFLD was comprehensively examined in terms of body weight, liver function markers, serum biochemistry and liver histology. Protein expression was determined using western blot analysis. The results of animal experiments showed that CPs could effectively inhibit the rate of weight gain, reduce the blood lipid level and liver index, and enhance glucose tolerance. The results of cell experiments showed that CPs could effectively reduce the accumulation of lipids in LO2 cells and inhibit the accumulation of reactive oxygen species (ROS). In addition, CPs could markedly reduce liver lipid accumulation in the liver cell and liver tissue, as further evidenced by the reduced expression of SREBP-1c in human non-tumour hepatic (LO2) cells. Meanwhile, the increased expression of SIRT1/PPAR-α and Nrf2/HO-1 pathways under the pretreatment of CPs in LO2 cells indicated that CPs could markedly relieve high fat-induced fatty liver injury, regulate insulin sensitivity, and reduce production of ROS. The results of in vivo and in vitro experiments demonstrated that CPs provided potential prevention and auxiliary treatment for NAFLD through reducing lipid accumulation, alleviating insulin resistance, and inhibiting oxidative stress. This study investigated the biological activity of CPs and laid the theoretical basis for the development of CP-based functional foods and dietary supplements.

Identification of a novel peptide that activates alcohol dehydrogenase from crucian carp swim bladder and how it protects against acute alcohol-induced liver injury in mice

Alcoholism is a severe threat to public health, and there are no adequate treatments for alcoholic liver disease. The aim of this study was to identify bioactive peptides derived from natural proteins that prevent acute alcohol-induced liver injury. We identified a peptide with the sequence Gly-Leu-hydroxyproline-Gly-Glu-Arg (GLpGER) from the hydrolysate of crucian carp swim bladder using size-exclusion chromatography and reversed-phase chromatography. The in vitro EC₅₀ value of GLpGER to activate alcohol dehydrogenase (ADH) was 137.9 ± 9 µM. Molecular docking experiments indicated that the mechanism by which GLpGER activates ADH may be related to the formation of stable complexes with ADH active pockets through hydrogen bonding, and electrostatic and hydrophobic interactions. Oral administration of GLpGER one hour before acute alcohol ingestion significantly increased alcohol metabolism, manifesting as reduced incidence of the loss of righting reflex, increased alcohol tolerance time, shortened sobering time, and decreased blood alcohol concentration level. GLpGER restored liver ADH activity, maintained the typical morphology of hepatocytes, and reduced serum levels of alanine aminotransferase and aspartate aminotransferase. These findings suggest that GLpGER might reduce acute alcohol-induced liver injury and may have the potential to be developed as an anti-inebriation ingredient.

Analytical Characterization of the Widely Consumed Commercialized Fermented Beverages from Russia (Kefir and Ryazhenka) and South Africa (Amasi and Mahewu): Potential Functional Properties and Profiles of Volatile Organic Compounds

In this study, four commercialized indigenous fermented beverages most highly consumed in Russia (kefir and ryazhenka) and South Africa (amasi and mahewu) were analyzed for their potential health-promoting properties and flavor-forming volatile organic compounds (VOC). The analysis of antioxidant capacity demonstrated superiority of dairy-based beverages (kefir, ryazhenka and amasi) over the corn-based mahewu; however, mahewu outperformed dairy-based beverages in terms of its potential antihypertensive effect (i.e., the ability to inhibit angiotensin I converting enzyme). The fatty acid (FA) content of kefir and ryazhenka were more diverse compared to that of amasi, but included a lesser amount of branched chain FA. In terms of calculated FA nutritional indices (e.g., indices of atherogenicity and thrombogenicity), kefir and ryazhenka performed similarly and significantly better than amasi. The agreement between beverages theoretical flavor profiles, which was obtained based on the flavors of individual VOC, and consumers’ flavor perception allow hypothesizing about the contribution of detected VOC to the overall products’ flavor. The obtained data expand current knowledge regarding traditional fermented beverages and their values in terms of national dietary recommendations. Additionally, reported VOC profiles will promote the inclusion of traditional fermented beverages into the rations based on the flavor pairing concept (which is controversial but widely applied).

Bacterial and fungal communities of traditional fermented Chinese soybean paste (Doujiang) and their properties

Soybean paste (Doujiang) is one of the traditional fermented foods from China, fermented by various microorganisms. However, the microflora of Doujiang keeps little known. In this study, the microbial communities of seven kinds of representative Doujiang samples were investigated by both culture-independent and culture-dependent methods. We found that core OTUs among seven Doujiang samples were mainly from Bacillus, Pseudomonas, Candida, and Aspergillus according to Illumina sequencing. Every type of Doujiang sample harbored a different composition of microbial community. Doujiang LSJ and LBJ had the highest bacterial and fungal richness and diversity, respectively. The structure of microbial community was remarkably correlated with Doujiang properties-pH, and the content of total protein, soluble protein, amino acid, and total sugar (p < .05). Bacillus spp. were most frequently isolated bacterial species. Fungi of Monascus, Candida, and Aspergillus were also isolated. Eleven microbial strains showed high protease activities to degrade corn proteins, which can form obvious transparent hydrolytic circles in corn gluten meal medium plates. Therefore, microbial communities were supposed to tightly connect to Doujiang type and properties. It is possible to apply potential protein-degrading microbial strains to corn byproducts for protein production in the future study.

Studies on vascular response to full superantigens and superantigen derived peptides: Possible production of novel superantigen variants with less vasodilation effect for tolerable cancer immunotherapy

Superantigens (SAgs) are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release and causing symptoms similar to sepsis, e.g. hypotension and subsequent hyporeactivity. We investigated the direct effect of SAgs on vascular tone using two recombinant SAgs, SEA and SPEA. The roles of Nitric Oxide (NO) and potentially hyperpolarization, which is dependent on the K⁺ channel activation, were also explored. The data show that SEA and SPEA have direct vasodilatory effects that were in part NO-dependent, but completely dependent on activation of K⁺ channels. Our work also identified the functional regions of one of the superantigens, SPEA, that are involved in causing the vasodilation and possible hypotension. A series of 20 overlapping peptides, spanning the entire sequence of SPEA, were designed and synthesized. The vascular response of each peptide was measured, and the active peptides were identified. Our results implicate the regions, (61-100), (101-140) and (181-220) which cause the vasodilation and possible hypotension effects of SPEA. The data also shows that the peptide 181-220 exert the highest vasodilation effect. This work therefore, demonstrates the direct effect of SAgs on vascular tone and identify the active region causing this vasodilation. We propose that these three peptides could be effective novel antihypertensive drugs. We also overexpressed, in E.coli, four superantigens from codon optimized genes.