Neuroprotective effects of two selenium-containing peptides, TSeMMM and SeMDPGQQ, derived from selenium-enriched rice protein hydrolysates on Pb2+-induced oxidative stress in HT22 cells

A novel neuroprotective peptide YVYAETY identified and screened from Flammulina velutipes protein hydrolysates attenuates scopolamine-induced cognitive impairment in mice

Flammulina velutipes protein hydrolysates are known for their abundant amino acids and excellent developmental values. This study aimed to identify and screen neuroprotective peptides from F. velutipes protein hydrolysates in vitro and validate the protective effects of YVYAETY on memory impairment in scopolamine-induced mice. The F. velutipes protein was hydrolyzed by simulated gastrointestinal digestion, followed by purification through ultrafiltration and gel chromatography. The fraction exhibiting the strongest neuroprotective activity was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The main identified peptides (SDLKPADF, WNDHYY, YVYAETY, and WFHPLF) effectively mitigated excessive ROS production by increasing SOD and GSH-px activities while inhibiting cell apoptosis and mitochondrial membrane potential (MMP) collapse against oxidative stress in Aβ25-35-induced HT22 cells. By molecular docking, the interaction between peptides and the active site of the Keap1-Kelch domain reveals their capacity to regulate the Keap1/Nrf2/HO-1 pathway. In vitro, the peptide YVYAETY had the best effect and can be further validated in vivo. The behavioral tests showed that YVYAETY improved scopolamine-induced cognitive impairment in mice. YVYAETY also alleviated neuron damage including neuron vacuolation and pyknotic nuclei in the hippocampus. Furthermore, it significantly inhibited oxidative stress and suppressed the activation of the Nrf2 pathway. Therefore, this study revealed that YVYAETY had the potential to serve as a novel neuroprotective agent.

Bridging neurotrophic factors and bioactive peptides to Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder. As the demographic shifting towards an aging population, AD has emerged as a prominent public health concern. The pathogenesis of AD is complex, and there are no effective treatment methods for AD until now. In recent years, neurotrophic factors and bioactive peptides including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), irisin, melatonin, have been discovered to exert neuroprotective functions for AD. Bioactive peptides can be divided into two categories based on their sources: endogenous and exogenous. This review briefly elaborates on the pathogenesis of AD and analyzes the regulatory effects of endogenous and exogenous peptides on the pathogenesis of AD, thereby providing new therapeutic targets for AD and a theoretical basis for the application of bioactive peptides as adjunctive therapies for AD.

Identification and preparation of selenium-containing peptides from selenium-enriched Pleurotus eryngii and their protective effect on lead-induced oxidative damage in NCTC1469 hepatocytes

BACKGROUND

Lead (Pb) is a highly toxic and persistent substance that easily accumulates in living organisms, eliciting cellular toxicity and oxidative stress. Some selenium-containing proteins and peptides prepared from plant extracts are beneficial for protecting the body's health and resisting external disturbances. In the present study, selenium-containing peptide species were prepared from selenium-enriched Pleurotus eryngii protein hydrolysates and to evaluate the benefits of selenium-containing peptides on Pb-induced oxidative stress in NCTC1469 hepatocytes.

RESULTS

Trypsin was selected as primary enzyme to hydrolyze the selenium-enriched protein (SPH). The optimal hydrolysis conditions were: hydrolysis time, 1.5 h; initial pH 8.0. The SPH was digested by trypsin and then purified by ultrafiltration, gel filtration chromatography and reversed-phase HPLC to obtain the selenium-containing peptides SPH-I-2. Furthermore, SPH-I-2 was analyzed and a number of total 12 selenium-containing peptides were identified by liquid chromatography-tandem mass spectroscopy. The NCTC1469 cell culture study showed that selenium-containing peptides were capable of reducing reactive oxygen species levels and regulating the Keap1/Nrf2 pathway by upregulating Nrf2, HO-1, GCLC, GCLM and NQO1 genes and downregulating Keap1 genes. Moreover, selenium-containing peptides were also able to suppress Pb-induced elevated levels of nitric oxide (NO), lactate dehydrogenase (LDH), malondialdehyde (MDA), increase antioxidant enzyme activity and alleviate cell apoptosis.

CONCLUSION

The present study indicated that the selenium-containing peptides could protect cells from Pb²⁺ -induced oxidative stress. © 2023 Society of Chemical Industry.

Selenium-enriched foods and their ingredients: As intervention for the vicious cycle between autophagy and overloaded stress responses in Alzheimer's disease

Dysfunctional autophagy induced by excessive reactive oxygen species (ROS) load and inflammation accelerates the development of Alzheimer's disease (AD). Recently, there has been an increasing interest in selenium-enriched ingredients (SEIs), such as selenoproteins, selenoamino acids and selenosugars, which could improve AD through antioxidant and anti-inflammation, as well as autophagy modulating effects. This review indicates that SEIs eliminate excessive ROS by activating the nuclear translocation of nuclear factor erythroid2-related factor 2 (Nrf2) and alleviate inflammation by inhibiting the mitogen-activated protein kinases (MAPKs)/nuclear factor kappa-B (NF-κB) pathway. Furthermore, they can activate the adenosine 5'-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, and subsequently promote amyloid beta (Aβ) clearance and reduce memory impairments. SEIs are ubiquitous in many plants and microorganisms, such as Brassicaceae vegetables, yeast, and mushroom. Enzymatic hydrolysis, as well as physical processing, such as thermal, high pressure and microwave treatment, are the main techniques to modify the properties of dietary selenium. This work highlights the fact that SEIs can inhibit inflammation and oxidative stress and provides evidence that supports the potential use of these dietary materials to be a novel strategy for improving AD.

Uptake, distribution, and elimination of selenite in earthworm Eisenia fetida at sublethal concentrations based on toxicokinetic model

Natural and anthropogenic causes have promoted the rapid increase in environmental selenium (Se) levels, and the complex Se metabolism and dynamic in organisms make it challenging to evaluate the toxicity and ecological risks. In this study, the kinetics of selenite in earthworm Eisenia fetida were investigated based on toxicokinetic (TK) model (uptake-elimination phases: 14-14 days). The results showed the highest sub-tissue Se concentrations in pre-clitellum (PC), post-clitellum (PoC) parts, and total earthworms were 95.71, 70.40, and 79.94 mg/kg, respectively, which indicates the distinctive Se uptake capacities of E. fetida. Se kinetic rates in PCs were faster than that of the total E. fetida for both uptake (K_us = 0.30-0.80 mg/kg/day) and elimination phases (K_ee = 0.024-0.056 mg/kg/day). Longer half-life times (LT_1/2) were observed in the total earthworms (17.85-47.15 d) than PCs (12.28-29.22 d), while non-significant difference was found for the kinetic Se bioaccumulation factor (BAF_k) in PC and total earthworms (12-19), which demonstrates that Se can be efficiently bioaccumulated and eliminated in earthworm PC part. Besides, the significant increase Se concentration in PoC with rapid elimination in PC also illustrates that earthworms can alleviate the Se stress by the transformation strategy of Se from the head to tail tissues. In conclusion, the investigation of Se kinetic accumulation and elimination characteristics in this study is helpful for understanding the metabolism and detoxification processes of Se in earthworms, and also providing a theoretical basis for further Se risk assessment using TK model.

A Review of Plant Selenium-Enriched Proteins/Peptides: Extraction, Detection, Bioavailability, and Effects of Processing

As an essential trace element in the human body, selenium (Se) has various physiological activities, such as antioxidant and anticancer activity. Selenium-enriched proteins/peptides (SePs/SePPs) are the primary forms of Se in plants and animals, and they are the vital carriers of its physiological activities. On the basis of current research, this review systematically describes the extraction methods (aqueous, alkaline, enzymatic, auxiliary, etc.) and detection methods (HPLC-MS/MS, GC-ICP-MS, etc.) for SePs/SePPs in plants. Their bioavailability and bioactivity, and the effect of processing are also included. Our review provides a comprehensive understanding and theoretical guidance for the utilization of selenium-enriched proteins/peptides.

Soluble Protein Hydrolysate Ameliorates Gastrointestinal Inflammation and Injury in 2,4,6-Trinitrobenzene Sulfonic Acid-Induced Colitis in Mice

Inflammatory bowel diseases (IBD) are chronic, recurring gastrointestinal diseases that severely impair health and quality of life. Although therapeutic options have significantly expanded in recent years, there is no effective therapy for a complete and permanent cure for IBD. Well tolerated dietary interventions to improve gastrointestinal health in IBD would be a welcome advance especially with anticipated favorable tolerability and affordability. Soluble protein hydrolysate (SPH) is produced by the enzymatic hydrolysis of commercial food industry salmon offcuts (consisting of the head, backbone and skin) and contains a multitude of bioactive peptides including those with anti-oxidant properties. This study aimed to investigate whether SPH ameliorates gastrointestinal injury in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mouse colitis model. Mice were randomly assigned to four groups: Control (no colitis), Colitis, Colitis/CP (with control peptide treatment), and Colitis/SPH (with SPH treatment). Colitis was induced by cutaneous sensitization with 1% TNBS on day −8 followed by 2.5% TNBS enema challenge on day 0. Control peptides and SPH were provided to the mice in the Colitis/CP or Colitis/SPH group respectively by drinking water at the final concentration of 2% w/v daily from day −10 to day 4. Then, the colon was harvested on day 4 and examined macro- and microscopically. Relevant measures included disease activity index (DAI), colon histology injury, immune cells infiltration, pro- and anti-inflammatory cytokines and anti-oxidative gene expression. It was found that SPH treatment decreased the DAI score and colon tissue injury when compared to the colitis-only and CP groups. The protective mechanisms of SPH were associated with reduced infiltration of CD4⁺ T, CD8⁺ T and B220⁺ B lymphocytes but not macrophages, downregulated pro-inflammatory cytokines (tumor necrosis factor-α and interleukin-6), and upregulated anti-inflammatory cytokines (transforming growth factor-β1 and interleukin-10) in the colon tissue. Moreover, the upregulation of anti-oxidative genes, including ferritin heavy chain 1, heme oxygenase 1, NAD(P)H quinone oxidoreductase 1, and superoxide dismutase 1, in the colons of colitis/SPH group was observed compared with the control peptide treatment group. In conclusion, the protective mechanism of SPH is associated with anti-inflammatory and anti-oxidative effects as demonstrated herein in an established mice model of colitis. Clinical studies with SPH as a potential functional food for the prevention or as an adjuvant therapy in IBD may add an effective and targeted diet-based approach to IBD management in the future.

Selenium biofortification in Pleurotus eryngii and its effect on lead adsorption of gut microbiota via in vitro fermentation

It is of great significance to develop safe and efficient dietary selenium sources to improve lead toxicity. In this study, selenate, selenite, SeMet and Se-yeast were supplied to investigate the Se biofortification and bioaccessibility in Pleurotus eryngii. The effects of Se-enriched P. eryngii on lead binding bacteria were investigated via in vitro fermentation. With 40 mg/kg Se in the substrate, the total Se contents of P. eryngii treated with selenite and Se-yeast were 145.22 ± 8.00 mg/kg and 90.01 ± 7.01 mg/kg, respectively. Compared with selenite, Se-yeast treatment significantly increased the organic Se proportion in P. eryngii (SeCys₂ 2.85 ± 0.17%, MeSeCys 2.33 ± 0.21% and SeMet 78.19 ± 1.58%), which led to higher bioaccessibility. With 1 mg/L lead treatment during in vitro fermentation, Se-enriched P. eryngii promoted the growth of Desulfovibrio, which contributed to the increase of gut microbiota lead adsorption. Se-enriched P. eryngii cultivated with Se-yeast could be used as dietary Se sources for lead toxicity improvement.

Selenium nanoparticles impart robust neuroprotection against deltamethrin-induced neurotoxicity in male rats by reversing behavioral alterations, oxidative damage, apoptosis, and neuronal loss

This study investigated the neuroprotective role of selenium nanoparticles (SeNPs) on deltamethrin-induced neurotoxicity in rats. A total of 32 adult male Wister rats were allocated into the following four groups: 1) control, 2) deltamethrin (0.6 mg/kg), 3) SeNPs (0.5 mg/kg), and 4) deltamethrin + SeNPs. All agents were administered orally three times per week for 2 months. Locomotor behavior, anxiety-like behavior, biochemical parameters, including brain oxidative damage biomarkers (Malondialdehyde (MDA) and reduced glutathione (GSH)), brain acetylcholinesterase (AChE), and brain genotoxicity were evaluated. The gene expression levels of IGF-1 and Bcl₂ were also determined. Moreover, a brain histopathological examination associated with the immunohistochemical determination of Bax in brain tissue was performed. Deltamethrin-intoxicated rats showed a reduction in the locomotor activity associated with a highly anxious state. They also displayed a disturbance in the brain redox state with a decrease in the brain AChE levels and a high DNA fragmentation percentage. Furthermore, they showed a decrement in the immunohistochemical GFAP levels as well as IGF-1 and Bcl₂ gene expression levels with an increase in the immunohistochemical Bax levels. All these changes were confirmed by brain histopathology. Interestingly, SeNPs ameliorated all these changes and restored the normal brain architecture. In conclusion. SeNPs possess a potent medicinal activity due to their antioxidant and anti-inflammatory activity. Therefore, SeNPs can be a potential agent in ameliorating deltamethrin-induced neurotoxicity.

A review on selenium-enriched proteins: preparation, purification, identification, bioavailability, bioactivities and application

Selenium (Se) deficiency can cause many diseases and thereby affect human health. Traditional inorganic Se supplements have disadvantages of toxicity and low bioavailability. Se-Enriched proteins exhibit good bio-accessibility and high biological activities. This review provides a comprehensive overview of the preparation, purification, identification, bioavailability, bioactivities and application of Se-enriched proteins. The method of extracting Se-enriched proteins from animals, microorganisms and plants mainly includes solvent extraction (water, salt, ethanol and alkali solution extraction) and novel extraction technologies (ultrasound-assisted and pulsed electric field assisted extraction). Se-Enriched proteins and their hydrolysates exhibit good bioactivities, mainly including antioxidant activity, immune regulation, neuroprotective activity, and inhibition of hyperglycemic activity, among others. Future research should focus on the relationship between Se-enriched protein metabolism and the selenium regulatory protein metabolic pathway by using multi-omics technology. In addition, it is necessary to comprehensively study the structure-activity relationship of Se-enriched proteins/hydrolysates from different sources, to further clarify their bioactive mechanism and to verify their health benefits in vivo.

Effect of ultrasonic treatment on the stability and release of selenium-containing peptide TSeMMM-encapsulated nanoparticles in vitro and in vivo

Rice selenium-containing peptide TSeMMM (T) with immunomodulatory functions was isolated from selenium-enriched rice protein hydrolysates. However, its biological activity is difficult to be protected in complex digestive environments. In this study, T was encapsulated within zein and gum arabian (GA) through ultrasound treatment to improve its bioactivity and bioavailability. The zein@T/GA nanoparticles were formed using ultrasonic treatment at 360 W for 5 min with a 59.9% T-encapsulation efficiency. In vitro digestion showed that the cumulative release rate of zein@T/GA nanoparticles reached a maximum of 80.69% after 6 h. In addition, short-term animal studies revealed that the nanoparticles had an effect on the levels of tissue glutathione and improved peptides' oral bioavailability. Conclusively, these findings suggest that the ultrasonicated polysaccharide/protein system is suitable for encapsulating active small molecular peptides. Furthermore, it provides a novel foundation for studying the bioavailability of active substances in functional foods.

Distribution of Pb and Se in mouse brain following subchronic Pb exposure by using synchrotron X-ray fluorescence

Lead (Pb) is a well-known neurotoxicant and environmental hazard. Recent experimental evidence has linked Pb exposure with neurological deterioration leading to neurodegenerative diseases, such as Alzheimer's disease. To understand brain regional distribution of Pb and its interaction with other metal ions, we used synchrotron micro-x-ray fluorescence technique (μ-XRF) to map the metal distribution pattern and to quantify metal concentrations in mouse brains. Lead-exposed mice received oral gavage of Pb acetate once daily for 4 weeks; the control mice received sodium acetate. Brain tissues were cut into slices and subjected for analysis. Synchrotron μ-XRF scans were run on the PETRA III P06 beamline (DESY). Coarse scans of the entire brain were performed to locate the cortex and hippocampus, after which scans with higher resolution were run in these areas. The results showed that: a) the total Pb intensity in Pb-exposed brain slices was significantly higher than in control brain; b) Pb typically deposited in localized particles of <10 um2 in both the Pb-exposed and control brain slices, with more of these particles in Pb-exposed samples; c) selenium (Se) was significantly correlated with Pb in these particles in the cortex and hippocampus/corpus callosum regions in the Pb-exposed samples, and the molar ratio of the Se and Pb in these particles is close to 1:1. These results indicated that Se may play a crucial role in Pb-induced neurotoxicity. Our findings call for further studies to investigate the relationship between Pb exposure and possible Se detoxification responses, and the implication in the etiology of Alzheimer's disease.

Protective effects of selenium in tacrolimus-induced lung toxicity: potential role of heme oxygenase 1

The present study aimed to evaluate the protective effects of selenium (Sel) administration against tacrolimus (Tac) - induced lung toxicity and to assess the relation between heme oxygenase 1 (HO-1) and these effects. The study was conducted on 36 Wistar male albino rats equally divided into four groups: (i) normal control; (ii) Sel (0.1 mg/kg per day p.o. for four weeks); (iii) TAC 3 mg/mL as single oral dose on 27th day; and (iv) Tac + Sel. Lung tissues, lung homogenate, and bronchoalveolar lavage of the sacrificed animals were investigated biochemically and histopathologically, by immunohistochemistry or by PCR. The Tac group showed significantly lower expression of HO-1. Administration of Sel was associated with increased HO-1 expression. Oxidative (malondialdehyde, reduced glutathione, superoxide dismutase, myeloperoxidase, and glutathione peroxidase activity) and nitrosative stress (nitric oxide) markers and markers of inflammation (interleukin 1β (IL-1β), IL-6, and IL-10) showed changes corresponding to HO-1 levels in rat groups. Tac group showed the highest expression of caspase-3. Sel exerted a protective role against Tac-induced lung toxicity.

Selenium in cereals: Insight into species of the element from total amount

Selenium (Se) is a trace mineral micronutrient essential for human health. The diet is the main source of Se intake. Se-deficiency is associated with many diseases, and up to 1 billion people suffer from Se-deficiency worldwide. Cereals are considered a good choice for Se intake due to their daily consumption as staple foods. Much attention has been paid to the contents of Se in cereals and other foods. Se-enriched cereals are produced by biofortification. Notably, the gap between the nutritional and toxic levels of Se is fairly narrow. The chemical structures of Se compounds, rather than their total contents, contribute to the bioavailability, bioactivity, and toxicity of Se. Organic Se species show better bioavailability, higher nutritional value, and less toxicity than inorganic species. In this paper, we reviewed the total content of Se in cereals, Se speciation methods, and the biological effects of Se species on human health. Selenomethionine (SeMet) is generally the most prevalent and important Se species in cereal grains. In conclusion, Se species should be considered in addition to the total Se content when evaluating the nutritional and toxic values of foods such as cereals.

Research progress on separation of selenoproteins/Se-enriched peptides and their physiological activities

Selenium (Se) is an essential nutrient associated with several physiological processes in humans and has raised interest because of its antioxidant and immune properties. Se deficiency is related to a variety of diseases and dysfunctions in humans. Due to its higher bioavailability and lower toxicity, organic Se is more recommendable than inorganic Se in the frame of a balanced diet. Se is present in 25 identified selenoproteins that commonly occur in human organisms. As part of selenocysteine (SeC), Se becomes co-translationally incorporated into the polypeptide chain and involved in the regulation of oxidative stress, redox mechanisms, and other crucial cellular processes responsible for innate and adaptive immune responses. This review presents the current information regarding the presence of selenoproteins in the human body, and the separation of selenoproteins and selenopeptides from various plants and their physiological roles in the immune and oxidation systems of humans. In general, the application of selenoproteins and Se-enriched peptides are practically important for the clinical arena, whereby it can be used for exploring new healthy foods.

Dietary intake of mixture coarse cereals prevents obesity by altering the gut microbiota in high-fat diet fed mice

Functional components including β-glucan, dietary fiber, resistant starch and polyphenols extracted from various coarse cereals have been reported to prevent high-fat diet (HFD) induced obesity via modulating gut microbiota. In this study, millet, maize, oat, soybean, and purple potato were ultrafine comminuted, mixed, and then extruded for the preparation of puffed mixture coarse cereals. HFD was used to investigate the effects of mixture coarse cereals on obesity and gut microbiota in mice. The results showed that dietary intake of mixture coarse cereals could decrease body weight gain and fat accumulation, improve the blood glucose tolerance and serum lipids levels, reduce the systemic inflammation, and down-regulate the expression of hepatic lipogenic genes. In addition, the levels of SCFAs and the composition of gut microbiota were investigated. The results indicated that mixture coarse cereals could promote the release of SCFAs, enhance the diversity of gut microbiota, and increase the relative abundance of Lactobacillus and Bifidobacterium, which might contribute to the anti-obesity activity. Present work suggested that the mixture coarse cereals could be developed as a nutraceutical for the prevention of HFD-induced obesity.