Novel Peptides Derived from Sea Cucumber Intestine Promotes Osteogenesis by Upregulating Integrin-Mediated Transdifferentiation of Growth Plate Chondrocytes to Osteoblasts

Joint technique "parallel peptide synthesis & de novo sequencing" development for the structure verification and high-throughput activity screening of biological peptides from sea cucumber (Stichopus japonicus) intestinal hydrolysate

This study introduces a novel joint technique combining "parallel peptide synthesis" and "de novo sequencing", which facilitates the high-throughput screening and structure validation of biological peptides derived from food and traditional Chinese medicine (TCM). Sea cucumber (Stichopus japonicus) was used as a model organism, undergoing simulated gastrointestinal digestion followed by de novo sequencing to predict potential peptides. Subsequently, cost-effective filter pipette tips were innovatively employed as parallel reaction vessels, enabling efficient peptide synthesis through the microfluidic flow of amino acid solutions over the loaded resin. After high-throughput biological activity screening, peptide YPGQLT was identified as the most potent antioxidant and acetylcholinesterase (AChE) inhibitor. It was then subjected to a molecular docking study to further explore its potential ligand-receptor interactions. This synergistic effect highlights peptide YPGQLT as a promising candidate for Alzheimer's disease (AD) treatment, thereby enhancing the potential biomedical application of sea cucumber. Notably, de novo predicted sequences can be further verified by comparing their characteristics, such as retention time and MS/MS spectrum, with those from the standard reference synthesized using this parallel synthesis protocol.

Technological and biofunctional potential of sea cucumber-derived macromolecular carbohydrates and proteins - A review

The craving for biodegradable sea biopolymers is growing as a result of ecological concerns over the use of non-renewable resources. Sea biopolymers are becoming more popular as sustainable alternatives across multiple industry sectors, covering the food sector. Sea cucumbers are a peculiar and remarkable aquatic animal species that have been extensively studied for the presence of these sustainable biopolymers, proteins, and polysaccharides, for instance. Biopolymers derived from sea cucumbers have significant biological advantages, such as anti-aging, anti-cancer, anti-inflammatory, and wound-healing properties. They are also biocompatible and biodegradable. Researchers have been investigating techniques for extracting and purifying biopolymers produced from sea cucumbers due to their excellent nutraceutical, medicinal, and cosmeceutical properties linked to their biopolymeric potential. The biotechnological and food-pharma sectors benefit from sea cucumber species, in the supply of natural chemicals for antibiotic resistance. A life cycle assessment evaluates sea cucumbers' environmental impact, recommending sustainable practices, energy-efficient processing, and waste management. This article provides a thorough and up-to-date update on sea cucumber-derived biopolymers, including sea cucumber-derived proteins (SCPt) and sea cucumber-derived polysaccharides (SCPs), as well as their uses as novel functional foods and therapeutic agents.

Isolation and Identification of a Novel Antioxidant Peptide from Fermented Sea Cucumber (Stichopus japonicus) Intestine and Its Protective Effects on HepG2 Cells from Oxidative Damage

The development of antioxidant peptides that can benefit both human health and the environment is a major focus in antioxidant research. The study aimed to isolate and identify antioxidant peptides from fermented sea cucumber intestines and evaluate their cytoprotective effects against H2O2-induced oxidative damage in HepG2 cells. A new peptide AAAFEGKW (AP3) was obtained through liquid chromatography-tandem mass spectrometry and virtual molecular docking screening. Synthetic peptide AP3 (1000 μmol/L) demonstrated significant antioxidant activity, with 1,1-diphenyl-2-picrylhydrazyl, superoxide anion, and hydroxyl radical scavenging capacities of 52.99 ± 1.05, 65.10 ± 0.70, and 54.17 ± 0.85%, respectively. Cytoprotective analysis revealed that the peptide AP3 protected oxidatively damaged HepG2 cells by activating the Keap1/Nrf2 pathway, enhancing the activities of endogenous antioxidant enzymes, and reducing the levels of reactive oxygen species and malondialdehyde. Thus, AP3 exhibits strong potential as a novel antioxidant, making it suitable for applications in functional foods and food preservation.

Effect of Enterococcus hirae GS22 Fermentation-Assisted Extraction on the Physicochemical and Bioactivities of Sea Cucumber Intestinal Polysaccharides

The sea cucumber intestine (SI), a secondary product from sea cucumber processing, contains polysaccharides as one of its active ingredients, and fermentation is an effective method for extracting bioactive substances from food by-products. In this study, to explore the effect of Enterococcus hirae GS22 fermentation on the extraction of SI polysaccharides, the polysaccharides were extracted through the SI with and without Enterococcus hirae GS22 fermentation, and the obtained polysaccharides were designated as SC-PF and SC-P. The extraction yield, the structural characteristics, and the biological functions of the polysaccharides were then evaluated. The results indicated that Enterococcus hirae GS22 could grow well using SI as the substrate and that fermentation could improve the extraction yield of the polysaccharide from 0.48% to 0.63%, decrease the molecular weight (Mw), and change the monosaccharide composition. The diameter of SC-PF was smaller than SC-P, and the absolute value of the zeta potential of SC-PF was found to be lower than SC-P. Fermentation does not change the functional group or the thermal ability of the polysaccharide. SC-PF had better antioxidant ability than SC-P; the DPPH and superoxide anion scavenging ability were 96.3% and 36.5%, respectively. SC-PF also showed nearly 1.3- and 1.1-fold higher inhibition of α-glucosidase and α-amylase as compared to SC-P. The current results showed that E. hirae GS22 fermentation has the potential to extract SI polysaccharides with better prebiotic abilities.

Novel peptides from sea cucumber intestines hydrolyzed by neutral protease alleviate exercise-induced fatigue via upregulating the glutaminemediated Ca2+ /Calcineurin signaling pathway in mice

Sea cucumber intestines are considered a valuable resource in the sea cucumber processing industry due to their balanced amino acid composition. Studies have reported that peptides rich in glutamate and branched-chain amino acids have anti-fatigue properties. However, the function of the sea cucumber intestine in reducing exercise-induced fatigue remains unclear. In this study, we enzymatically hydrolyzed low molecular weight peptides from sea cucumber intestines (SCIP) and administered SCIP orally to mice to examine its effects on exercise-induced fatigue using swimming and pole-climbing exhaustion experiments. The results revealed that supplementation with SCIP significantly prolonged the exhaustion time of swimming in mice, decreased blood lactate and urea nitrogen levels, and increased liver and muscle glycogen levels following a weight-loaded swimming test. Immunofluorescence analysis indicated a notable increase the proportion of slow-twitch muscle fiber and a significant decrease the proportion of fast-twitch muscle fiber following SCIP supplementation. Furthermore, SCIP upregulated mRNA expression levels of Ca2+ /Calcineurin upstream and downstream regulators, thereby contributing to the promotion of skeletal muscle fiber type conversion. This study presents the initial evidence establishing SCIP as a potential enhancer of skeletal muscle fatigue resistance, consequently providing a theoretical foundation for the valuable utilization of sea cucumber intestines.

Adsorption characteristics of V-type starch for off-odors of sea cucumber intestinal peptides in solid-phase environment

With the concern of the strong fishy odor of sea cucumber intestinal peptides, the deodorization potential of V-type starch with a flexible cavity was investigated. By gas chromatography-mass spectrometry and electronic nose, it was confirmed that V-type starch effectively deodorized key off-odor compounds (isobutyric acid, butanoic acid, 1-octen-3-ol, nonanal, and trimethylamine), and the optimum deodorization performance (adsorption ratio of 92.45%) was achieved after 8 h adsorption at the sea cucumber intestinal peptide to starch ratio of 1:15 (w/w). In the Fourier transform infrared spectrum of the V-type starch inclusion complexes, a new characteristic peak was observed at 1563 cm-1 when the sea cucumber intestinal peptide to starch ratio was 1:1 (w/w). The presence of this peak was attributed to the complexation between V-type starch and trimethylamine. For the first time, we demonstrated that the V-type starch could deodorize aquatic products, and this study contributes to the application of starch materials.

Preparation of Novel Sea Cucumber Intestinal Peptides to Promote Tibial Fracture Healing in Mice by Inducing Differentiation of Hypertrophic Chondrocytes to the Osteoblast Lineage

SCOPE

Hypertrophic chondrocytes have a decisive regulatory role in the process of fracture healing, and the fate of hypertrophic chondrocytes is not only apoptosis. However, the mechanism of sea cucumber (Stichopus japonicus) intestinal peptide (SCIP) on fracture promotion is still unclear. This study aims to investigate the effect of sea cucumber intestinal peptide on the differentiation fate of hypertrophic chondrocytes in a mouse tibial fracture model.

METHODS AND RESULTS

Mice are subjected to open fractures of the right tibia to establish a tibial fracture model. The results exhibit that the SCIP intervention significantly promotes the mineralization of cartilage callus, decreases the expression of the hypertrophic chondrocyte marker Col X, and increases the expression of the osteoblast marker Col I. Mechanically, SCIP promotes tibial fracture healing by promoting histone acetylation and inhibiting histone methylation, thereby upregulating pluripotent transcription factors induced the differentiation of hypertrophic chondrocytes to the osteoblast lineage in a manner distinct from classical endochondral ossification.

CONCLUSION

This study is the first to report that SCIP can promote tibial fracture healing in mice by inducing the differentiation of hypertrophic chondrocytes to the osteoblast lineage. SCIP may be considered raw material for developing nutraceuticals to promote fracture healing.

Research progress on the chemical components and biological activities of sea cucumber polypeptides

Owing to their unique physical and chemical properties and remarkable biological activities, marine biological resources are emerging as important sources of raw materials for producing health products, food, and cosmetics. Collagen accounts for approximately 70% of the sea cucumber body wall, and its hydrolysis produces small-molecule collagen polypeptides with diverse biological functions, such as anticancer, antihypertensive, immune-enhancing, memory-enhancing, and cartilage tissue repairing effects. Notably, the potential of sea cucumber polypeptides in combination with anticancer therapy has garnered considerable attention. Determining the composition and structure of sea cucumber polypeptides and exploring their structure-activity relationships will aid in obtaining an in-depth understanding of their diverse biological activities and provide scientific insights for the development and utilization of these polypeptides. Therefore, this review focuses on the amino acid structures and activities of sea cucumber polypeptides of varying molecular weights. This study also provides an overview of the biological activities of various sea cucumber polypeptides and aims to establish a scientific basis for their development.

Whey Protein Hydrolysate Ameliorated High-Fat-Diet Induced Bone Loss via Suppressing Oxidative Stress and Regulating GSK-3β/Nrf2 Signaling Pathway

Long-term hypercaloric intake such as a high-fat diet (HFD) could act as negative regulators on bone remodeling, thereby inducing bone loss and bone microarchitecture destruction. Currently, food-derived natural compounds represent a promising strategy to attenuate HFD-induced bone loss. We previously prepared a whey protein hydrolysate (WPH) with osteogenic capacity. In this study, we continuously isolated and identified an osteogenic and antioxidant octapeptide TPEVDDA from WPH, which significantly promoted the alkaline phosphatase activities on MC3T3-E1 cells and exerted DPPH radical scavenging capacity. We then established an HFD-fed obese mice model with significantly imbalanced redox status and reduced bone mass and further evaluated the effects of different doses of WPH on ameliorating the HFD-induced bone loss and oxidative damages. Results showed that the administration of 2% and 4% WPH for 12 weeks significantly restored perirenal fat mass, improved serum lipid levels, reduced oxidative stress, and promoted the activity of antioxidant enzymes; meanwhile, WPH significantly preserved bone mass and bone mechanical properties, attenuated the degradation of trabecular microstructure, and regulated serum bone metabolism biomarkers. The protein levels of Runx2, Nrf2, and HO-1, as well as the phosphorylation level of GSK-3β in tibias, were notably activated by WPH. Overall, we found that the potential mechanism of WPH on ameliorating the HFD-induced bone loss mainly through its antioxidant and osteogenic capacity by activating Runx2 and GSK-3β/Nrf2 signaling pathway, demonstrating the potential of WPH to be used as a nutritional strategy for obesity and osteoporosis.