Plastein reaction mechanisms and the alteration of its product properties have been studied for decades. This study investigated the plastein-mediated modifications in silver carp protein hydrolysate (SCPH) from both mechanistic and functional perspectives. Unlike prior research, this investigation uncovered that hydrogen bonding supplemented the dominant hydrophobic interactions in plastein's mechanism for the first time, as supported by peptide concentrations, molecular weight, amino acids, chemical forces, and peptide sequence by LC-MS/MS. This innovative reaction mechanism cascaded into the enhancement of SCPH functional attributes. Plastein induced increased COOH in SCPH's side-chain groups significantly enhanced Fe2+ (from 4.49 to 14.12 %) and Zn2+ (from 53.53 to 64.47 %) chelation. Moreover, the elevated DPPH (17.56 %-23.97 %) and hydroxyl radical (68.49 %-79.32 %) scavenging power indicated a broader improvement in SCPH with plastein. In SCPH, plastein elucidated reaction intricacies and enhanced its utility, propelling SCPH into a realm of extended potential.

AbstractThe intricate causes of Alzheimer's disease (AD) hinder effective, lasting treatment. Although the dietary modulation of the brain–gut axis was explored for AD therapy, the exact mechanism remains unclear. This study suggested that 140 days of the whey protein hydrolysate (WPH) intake could attenuate the AD pathologic symptoms in APP/PS1 transgenic mice via a bidirectional action of the gut microbe–SCFA (short‐chain fatty acid)–brain axis. Behavioral tests demonstrated that high‐dose WPH (WPH‐H, 100 mg/kg body weight [bw]) improved passive and recognition memory in mice. Furthermore, WPH‐H significantly reduced amyloid beta 1–42 (Aβ1–42) levels in serum (p < .05) and brain (p < .001) while enhancing serum superoxide dismutase (SOD) activity (p < .01). Brain acetylcholinesterase (p < .01) activity and pro‐inflammatory factors in serum were also reduced. Notably, WPH‐H remodeled gut microbiota composition by increasing Dubosiella and decreasing Bacteroides and norank_f__Ruminococcaceae while stimulating SCFA production. Proteomics indicated that WPH enhanced neurotoxic Aβ autophagy, synaptogenesis, neurotransmitter delivery, and antioxidative stress response via regulated protein expression. Correlation analysis revealed strong links between modified gut microbiota, elevated SCFA levels, and hippocampal protein up‐regulation (Atg4b, Nsfl1c, Tcf20, Nr2f1, and Trappc9) and down‐regulation (Krt1). Overall, the amelioration of memory deficits in APP/PS1 mice through WPH‐H consumption can be attributed to the interconnected interactions among gut microbes, SCFAs, and brain. Our study illuminated the intricate interplay between nutrition, gut health, and memory function, emphasizing WPH's potential in alleviating AD symptoms.

Grass carp (Ctenopharyngodon idella) are used as raw material for conventional surimi products in Southern China. However, endogenous serine proteases deteriorated the texture of the surimi gel. To unlock the mechanism behind, the present study isolated the crude myofibril-bound serine protease (cMBSP) in grass carp and studied its effects on surimi gel. The cMBSP activity was the highest at 40 degrees C and pH 8.0, and it remained stable at 20-55 degrees C neutral pH. Additionally, it was susceptible to serine protease inhibitors and high concentrations of Na+. The maximum degradation of myosin heavy chain by cMBSP was observed at 50 degrees C. Protein unc-45 homolog B (a myosin chaperone) is one of the apparent degradation products according to mass spectrometry. The cMBSP caused lower water holding capacity and deteriorated texture in the surimi gel. This study expanded insights about the mechanism of surimi gel degradation by cMBSP, which provided theoretical basis for enhancing surimi quality.

To develop food flavorings with a delicious taste and an anti-oxidation effect, in this study, the glucose Maillard reaction was used for hydrolysates of Urechis unicinctus. The various biological activities of Maillard reaction products (MRPs) and their antioxidant capacity were evaluated. The results showed that the unique fishy odor substances of seafood in MRPs were reduced, indicating that the Maillard reaction improved the flavor of the hydrolysate of Urechis unicinctus. Meanwhile, MRPs exhibited more competitive radical scavenging activities compared to the hydrolysate. Moreover, MRPs demonstrated a considerable potential to protect against 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AAPH)-induced oxidative stress in a cell model in vitro and in a zebrafish model in vivo. Finally, a novel food flavoring was produced with MRPs as raw material, while the sensory qualities were deemed acceptable. In consequence, during industrial production, MRPs of Urechis unicinctus hydrolysate act as a high-quality raw material for functional flavorings and provide an effective way for the utilization of marine resources.

AbstractThe degradation of frozen sturgeon surimi can be attributed to the endogenous serine protease. This study was first to examine the impact of egg whites on the frozen sturgeon surimi's gel properties from the perspective of inhibiting endogenous serine protease. The protease activity of egg whites group (CA + EW group, consisting of 4% egg whites and cryoprotectants) was 45.15% lower than that of cryoprotectants group (CA group, consisting of 3% sucrose, 3% sorbitol, and 0.3% sodium tripolyphosphate) at 12 weeks. From the results of inhibition kinetics, serine protease was inhibited by both anticompetitive and noncompetitive inhibition modes. Molecular docking analysis indicated that egg white achieves this inhibitory effect through ionic interactions and hydrogen bonding with serine protease. However, this inhibitory effect was absent when the freezing period was extended to 24 weeks. Compared with CA group, the CA + EW group exhibited 54.76% and 4.59% increase in gel strength and water‐holding capacity, and 32.42% reduction in cooking loss after 24 weeks of freezing. Egg whites also impeded water migration and enhanced the density and smoothness of the gel microstructure, reducing protein aggregation. These results indicated that egg whites serve a dual function: inhibiting serine protease and filling the gel network within 12 weeks, mitigating protein aggregation and ice crystal formation over 24 weeks. This study elucidated the mechanism underlying the impact of egg white on endogenous serine protease in sturgeon surimi during long‐term freezing, laying a theoretical foundation for the industrialization of sturgeon surimi.

Our previous studies have highlighted the potential of silver carp hydrolysate (SCH) in managing chronic diseases. Unfortunately, its fishy smell and bitter taste limited consumer acceptance. Prebiotic oligosaccharides are often used as dietary supplements, ignoring their role as carbonyl ligands in the Maillard reaction to enhance food's sensory and antioxidant properties. This study aimed to improve SCH's sensory attributes and investigate its physicochemical properties and antioxidant activities using prebiotic oligosaccharides via the Maillard reaction. The results showed that xylo-oligosaccharide (XOS) had the highest reactivity among the oligosaccharides tested, and it greatly enhanced the taste and flavor of SCH, as well as its antioxidant activities (0.45 to 16.5 times). Specifically, XOS effectively reduced the fishy smell and bitter taste, imparting a caramel-like flavor and overall acceptability to SCH. The improved flavor profile was attributed to the increased presence of sulfur-containing and nitrogen oxide volatile flavor compounds, such as benzothiazole, methional, and furans, which also contributed to antioxidant effects. Sensory evaluation results indicated that SCH obtained from papain exhibited a stronger bitter taste than that obtained from alcalase. Additionally, XOS imparted a reddish-brown color to SCH due to the higher browning intensity. This study is the first to demonstrate that XOS in the Maillard reaction can effectively improve the undesirable flavor and taste of SCH while enhancing its antioxidant activities, providing a theoretical basis for developing SCH as a market-acceptable functional food ingredient. The sensory properties and antioxidant activities of SCH can be improved by using prebiotic oligosaccharides via the Maillard reaction, providing a theoretical basis for the development of new functional foods, and more possibilities for the sustainable development of the silver carp industry.

The oxidative modification of myofibrillar proteins (MPs) has been identified as a crucial factor affecting meat quality during processing. We compared the effects of 4-hydroxy-2-nonenal (HNE) and lipoxygenase (LOX)-catalyzed linoleic acid (LA) oxidation products on the digestibility and gel properties in MPs from bighead carp. Both treatments resulted in decreased free amino acid content, reduced digestibility, and loss of amino acids in MPs. The HNE treatment enhanced gel strength by increasing hydrophobic interactions within the gel matrix. Conversely, the LOX-catalyzed LA oxidation enhanced disulfide bonds, leading to an agglomerated microstructure. Reduced myofibrillar protein (MP) solubility, primarily due to protein aggregation, was observed in the LA group but not in the HNE group. This distinction suggests that the impact on MP functionality is predominantly influenced by the protein aggregation induced by LOX-catalyzed LA oxidation rather than by HNE alone.

The degradation of structural proteins during fish postmortem storage is a critical factor affecting meat quality, leading to economic losses in the seafood industry. The complex interplay between caspase-3 and structural protein stability during fish postmortem storage remains largely unexplored. By treating grass carp fillets with a caspase-3 inhibitor, we establish a model for inhibiting apoptosis, delineating the role of caspase-3 in protein degradation. The effect of caspase-3 on grass carp proteins following postmortem storage and its cascade interaction with calpain and cathepsin L was further investigated. The result demonstrated that the destabilization of the mitochondrial membrane during apoptosis led to modifications in the B-cell lymphoma (Bcl) family proteins, subsequently triggered the activation of caspase-9/caspase-3. Additionally, caspase-3 reduced the expression of the calpastatin and lysosomal membrane protein 1 (LAMP-1) gene, resulting in increased calpain and cathepsin L activity. SDS-PAGE and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis indicated that caspase-3 inhibitor treatment reduced actin fractures and preserved critical structural proteins. This investigation unveils the molecular mechanisms through which caspase-3 affects protein degradation in fish fillets during storage, providing valuable insights into the postmortem degradation processes.

BackgroundPigs serve as a crucial source of protein in the human diet and play a fundamental role in ensuring food security. However, infectious diseases caused by bacteria or viruses are a major threat to effective global pig farming, jeopardizing human health. Peripheral blood mononuclear cells (PBMCs) are a mixture of immune cells that play crucial roles in immunity and disease resistance in pigs. Previous studies on the gene expression regulation patterns of PBMCs have concentrated on a single immune stimulus or immune cell subpopulation, which has limited our comprehensive understanding of the mechanisms of the pig immune response.ResultsHere, we integrated and re-analyzed RNA-seq data published online for porcine PBMC stimulated by lipopolysaccharide (LPS), polyinosinic acid (PolyI:C), and various unknown microorganisms (EM). The results revealed that gene expression and its functional characterization are highly specific to the pathogen, identifying 603, 254, and 882 pathogen-specific genes and 38 shared genes, respectively. Notably, LPS and PolyI:C stimulation directly triggered inflammatory and immune-response pathways, while exposure to mixed microbes (EM) enhanced metabolic processes. These pathogen-specific genes were enriched in immune trait-associated quantitative trait loci (QTL) and eGenes in porcine immune tissues and were implicated in specific cell types. Furthermore, we discussed the roles of eQTLs rs3473322705 and rs1109431654 in regulating pathogen- and cell-specific genes CD300A and CD93, using cellular experiments. Additionally, by integrating genome-wide association studies datasets from 33 complex traits and diseases in humans, we found that pathogen-specific genes were significantly enriched for immune traits and metabolic diseases.ConclusionsWe systematically analyzed the gene expression profiles of the three stimulations and demonstrated pathogen-specific and cell-specific gene regulation across different stimulations in porcine PBMCs. These findings enhance our understanding of shared and distinct regulatory mechanisms of genetic variants in pig immune traits.

The integrity of myofibrillar proteins during the initial post-mortem storage phase critically determines the shelflife of fish, profoundly affecting consumer acceptance and market value. This research investigates the degradation of grass carp muscle texture and structure triggered by caspase-3-induced apoptosis, a key factor influencing early storage quality deterioration. By inhibiting endogenous caspase-3, the study tracks changes in apoptosis levels, muscle texture, microstructural integrity, protein organizational structure, and amino acid profiles. Apoptosis was found to peak between 48 and 72h post-mortem, during which caspase-3 activity led to significant muscle softening. This softening is attributed to disruptions in crucial structural components such as the Z-line and M-line, culminating in extensive degradation of myofibrillar proteins. Furthermore, protein structure modeling demonstrated that caspase-3 cleavage at ASP187 critically destabilizes the alpha-helix structure, underlining the enzyme's pivotal role in the early post-mortem softening of fish muscle. These insights provide a foundational understanding of the biochemical processes that underpin early quality loss in stored fish, offering potential targets for interventions aimed at enhancing fish storage outcomes and extending shelf life in the aquaculture industry.

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Neurodegeneration is most prevalent in the elderly, resulting in memory loss or even dementia, and it places a considerable strain on society and the economy. The hydrolysate from whey protein, a natural byproduct of cheese-making, exhibits potent bioactivity and thus can serve as a potential strategy to slow down neurological aging. This research aimed to ascertain the neuroprotective effect of the whey protein hydrolysate (WPH) against age-related memory decline and further explore the underlying mechanisms. Our results indicated that a high dose (100 mg/kg) of the WPH could improve the behavioral performance of middle-aged mice and adjust the morphology and organization of hippocampal cells. Moreover, WPH-treated mice showed decreased levels of inflammation and oxidative stress and considerably reduced levels of amyloid beta 1-42 (A beta 1-42) and AchE in brain tissue. Hippocampus proteomic analysis revealed that differentially expressed proteins were mainly related to A beta plaque, neurogenesis, and cAMP signaling pathways, such as Mdk, Mff, Pde2a, and Chrm1. After 20 weeks of the WPH intervention, the gut microbiomes associated with SCFA production and gut homeostasis were increased in mice. Our study provided evidence supporting the WPH as a candidate for functional ingredients in preventing cognitive deficits.

The search for cryoprotectants has garnered significant attention due to the susceptibility of myofibrillar proteins (MP) to freezing denaturation during frozen storage, leading to the degradation of surimi quality. In this study, we investigated the effects of fistular onion stalk polysaccharide (FOSP), a byproduct of dry fistular onion leaves, on the physicochemical properties of frozen surimi derived from bighead carp during storage at-20 degrees C for 150 days. FOSP-3, the primary constituent of FOSP, possesses a molecular weight (MW) greater than 4 kDa and consists of galactose (Gal), arabinose (Ara), glucuronic acid (GlcA), and glucose (Glc) in a molar ratio of 0.71:0.15:0.04:0.10. Our results from texture profile analysis (TPA) reveal that the addition of FOSP (4% and 8%) improves the gel strength, chewiness, and springiness of the surimi gel, with the most significant effect observed at FOSP (4%). Furthermore, the storage modulus G' (Pa) of the surimi/FOSP composite gel surpasses that of the control group (CK), indicating the superior springiness of the composite gel. Moreover, the inclusion of FOSP reduces centrifugal loss, suggesting an enhanced water-holding capacity of the surimi gel. Importantly, the presence of FOSP delays the decline of Ca2+-ATPase activity and the increase of carbonyls, while stabilizing the secondary structure of MP. Therefore, FOSP emerges as a potential cryoprotectant for the frozen surimi industry, offering promising advantages in enhancing the quality and stability of surimi during frozen storage.

Whey protein and its hydrolysates are ubiquitously applied in the food system. However, their effect on cognitive impairment remains unclear. This study aimed to investigate the potential ability of whey protein hydrolysate (WPH) to ameliorate cognitive degeneration. WPH intervention in Crl:CD1 (ICR, Institute for cancer research) mice and aged C57BL/6J mice in a scopolamine-induced cognitive impairment model for 10 days were evaluated. Behavioral tests indicated that WPH intervention improved the cognitive abilities in ICR and aged C57BL/6J mice (p < 0.05). Scopolamine enhanced the Aβ1-42 level in the brain tissue, and the WPH intervention exhibited a similar therapeutic effect to donepezil in ICR mice. A noticeable reduction occurred in serum Aβ1-42 level of aged mice treated with WPH. The histopathological study of the hippocampus showed that WPH intervention alleviates neuronal damage. Hippocampus proteomic analysis suggested possible mechanisms of WPH action. The relative abundance of Christensenellaceae, a gut microbe related to Alzheimer's disease, was altered by WPH intervention. This study demonstrated that short-term WPH intake protected against memory impairment induced by scopolamine and aging.

ABSTRACTPreadipocytes become mature adipocytes after proliferation and differentiation, and although many genes and microRNAs have been identified in intramuscular fat, their physiological function and regulatory mechanisms remain largely unexplored. miR-26a-5p has been reported to be related to fat deposition, but its effect on porcine preadipocyte differentiation has not been explored. In this study, bioinformatics analysis and luciferase reporter assay identified that miR-26a-5p binds to the 3ʹUTR of Acyl-CoA synthetase long-chain family member 3 (ACSL3) mRNA. The model for porcine intramuscular preadipocyte differentiation was established to explore the function of miR-6a-5p-ACSL3 on adipocyte differentiation. ACSL3 knockdown markedly reduced the triglycerides (TG) content of cells, as well as the mRNA levels of adipogenic marker genes (PPAR-γ and SREBP-1c). The number of lipid droplets in cells transfected with a miR-26a-5p mimic is significantly reduced, consistent with ACSL3 knockdown results, while the miR-26a-5p inhibitor resulted in opposite results. Taken together, miR-26a-5p is a repressor of porcine preadipocyte differentiation and plays a vital role in ACSL3-mediated adipogenesis.

Intramuscular fat (IMF) content is an important factor in porcine meat quality. Previously, we showed that miR-34a was less abundant in liver tissue from pigs with higher backfat thickness, compared to pigs with lower backfat thickness. The purpose of this present study was to explore the role of miR-34a in adipogenesis. Bioinformatics analysis identified Acyl-CoA synthetase long chain family member 4 (ACSL4) as a putative target of miR-34a. Using a luciferase reporter assay, we verified that miR-34a binds the ACSL4 mRNA at the 3’UTR. To examine the role of the miR-34a-ACSL4 interaction in IMF deposition in the pig, mRNA and protein expression of the ACSL4 gene was measured in primary intramuscular preadipocytes transfected with miR-34a mimic and inhibitor. Our results showed that ACSL4 is expressed throughout the entire differentiation process in pig preadipocytes, similar to the lipogenesis-associated genes PPARγ and aP2. Transfection with miR-34a mimic reduced lipid droplet formation during adipogenesis, while miR-34a inhibitor increased lipid droplet accumulation. Transfection with miR-34a mimic also reduced the mRNA and protein expression of ACSL4 and lipogenesis genes, including PPARγ, aP2, and SREBP-1C, but increased the expression of steatolysis genes such as ATGL and Sirt1. In contrast, the miR-34a inhibitor had the opposite effect on gene expression. Further, knockdown of ACSL4 decreased lipid droplet accumulation. Our results support the hypothesis that miR-34a regulates intramuscular fat deposition in porcine adipocytes by targeting ACSL4.