Structure-function relationship analysis of fucoidan from sea cucumber (Holothuria tubulosa) on ameliorating metabolic inflammation

A comprehensive review of sulfated fucan from sea cucumber: Antecedent and prospect

Sulfated fucan from sea cucumber is mainly consists of L-fucose and sulfate groups. Recent studies have confirmed that the structure of sulfated fucan mainly consists of repeating units, typically tetrasaccharides. However, there is growing evidence indicating the presence of irregular domains with heterogeneous units that have not been extensively explored. Moreover, as a key contributor to the nutritional benefits of sea cucumbers, sulfated fucan demonstrates a range of biological activities, such as anti-inflammatory, anticancer, hypolipidemic, anti-hyperglycemic, antioxidant, and anticoagulant properties. These biological activities are profoundly influenced by the structural features of sulfated fucan including molecular weight and distribution patterns of sulfate groups. The latest research indicates that sulfated fucan is dispersed in the extracellular matrix of the body wall of sea cucumbers. This article aimed to review the research progress on the in-situ distribution, structures, structural elucidation strategies, functions, and structure-activity relationships of sulfated fucan, especially in the last decade. It also provided insights into the major challenges and potential solutions in the research and development of sulfated fucan. Moreover, the fucanase and carbohydrate binding modules are anticipated to play pivotal roles in advancing this field.

Modulation of Glucose Consumption and Uptake in HepG2 Cells by Aqueous Extracts from the Coelomic Fluid of the Edible Holothuria tubulosa Sea Cucumber

The cell-free aqueous extract from the coelomic fluid of Holothuria tubulosa was prepared and examined for its glucose-lowering effect on HepG2 cells in vitro. In particular, employing a combination of cytochemical, flow cytometric, PCR, and protein blot techniques, we evaluated its role on glucose internalization and storage and on the upregulation and surface translocation of the two glucose transporters GLUT-2 and -4. The changes in expression, synthesis, and/or activation of the GLUT2-related transcription factor hepatocyte nuclear factor-1 alpha (HNF1α) and the GLUT-4-translocation regulatory factors insulin receptor substrate-1 (IRS-1) and AKT were also studied. Our results showed the improved glucose response by HepG2 cells, leading to an evident increase in glucose consumption/uptake and glycogen storage upon exposure. Moreover, the extract induced molecular reprogramming involving the upregulation of (i) IRS1 gene expression, (ii) the transcription and translation levels of HNF1α, AKT, and GLUT-4, (iii) the phosphorylation level of AKT, (iv) the synthesis of GLUT-2 protein, and (v) the translocation of GLUT-2 and -4 transporters onto the plasma membrane. Cumulatively, our results suggest that the coelomic fluid extract from H. tubulosa can be taken into consideration for the development of novel treatment agents against diabetes mellitus.

Recent advances in the extraction, purification, structural-property correlations, and antiobesity mechanism of traditional Chinese medicine-derived polysaccharides: a review

Traditional Chinese medicine (TCM) has displayed preventive and therapeutic effects on many complex diseases. As natural biological macromolecules, TCM-derived antiobesogenic polysaccharides (TCMPOs) exhibit notable weight-loss effects and are seen to be a viable tactic in the fight against obesity. Current studies demonstrate that the antiobesity activity of TCMPOs is closely related to their structural characteristics, which could be affected by the extraction and purification methods. Therefore, the extraction, purification and structural-property correlations of TCMPOs were discussed. Investigation of the antiobesity mechanism of TCMPOs is also essential for their improved application. Herein, the possible antiobesity mechanisms of TCMPOs are systematically summarized: (1) modulation of appetite and satiety effects, (2) suppression of fat absorption and synthesis, (3) alteration of the gut microbiota and their metabolites, and (4) protection of intestinal barriers. This collated information could provide some insights and offer a new therapeutic approach for the management and prevention of obesity.

Natural polysaccharides protect against diet-induced obesity by improving lipid metabolism and regulating the immune system

Unhealthy dietary patterns-induced obesity and obesity-related complications pose a great threat to human health all over the world. Accumulating evidence suggests that the pathophysiology of obesity and obesity-associated metabolic disorders is closely associated with dysregulation of lipid and energy metabolism, and metabolic inflammation. In this review, three potential anti-obesity mechanisms of natural polysaccharides are introduced. Firstly, natural polysaccharides protect against diet-induced obesity directly by improving lipid and cholesterol metabolism. Since the immunity also affects lipid and energy metabolism, natural polysaccharides improve lipid and energy metabolism by regulating host immunity. Moreover, diet-induced mitochondrial dysfunction, prolonged endoplasmic reticulum stress, defective autophagy and microbial dysbiosis can disrupt lipid and/or energy metabolism in a direct and/or inflammation-induced manner. Therefore, natural polysaccharides also improve lipid and energy metabolism and suppress inflammation by alleviating mitochondrial dysfunction and endoplasmic reticulum stress, promoting autophagy and regulating gut microbiota composition. Specifically, this review comprehensively summarizes underlying anti-obesity mechanisms of natural polysaccharides and provides a theoretical basis for the development of functional foods. For the first time, this review elucidates anti-obesity mechanisms of natural polysaccharides from the perspectives of their hypolipidemic, energy-regulating and immune-regulating mechanisms.

Fucoidan mitigates gastric ulcer injury through managing inflammation, oxidative stress, and NLRP3-mediated pyroptosis

This study aimed to elucidate the gastro-protective effect of fucoidan against ethanol-induced gastric ulcer mediated via NLRP3-induced pyroptosis as an underlying mechanism, not yet assessed in prior research. Forty-eight male Albino mice were divided into six groups: Group I (normal control), group II (Ulcer/ethanol control), group III (Omeprazole + ethanol), group IV (fucoidan 25 mg + ethanol), group V (fucoidan 50 mg + ethanol) and group VI (fucoidan only). Fucoidan was administered orally for seven consecutive days followed by ulcer induction by a single oral dose of ethanol. Using colorimetric analysis, ELISA, qRT-PCR, histological assessment, and immunohistochemical studies, the results revealed that ethanol-induced ulcer exhibited an ulcer score of 42.5 ± 5.1 and a significant increase (p < 0.05) in malondialdehyde (MDA), nuclear factor kappa B (NF-κB), and interleukin 6 (IL-6) with a significant decrease in the gastro-protective mediators, prostaglandin E2 (PGE2), superoxide dismutase (SOD) and glutathione (GSH), accompanied with an increase in NLRP3, interleukin 1β (IL-1β), interleukin 18 (IL-18), caspase 1, caspase 11, gasdermin D, and toll-like receptor 4 (TLR4), compared with the normal control. Pre-treatment with fucoidan showed a comparable result with omeprazole. Additionally, pre-treatments elevated the levels of the gastro-protective mediators and lessened oxidative stress, relative to the positive control findings. Conclusively, fucoidan has a promising gastro-protective role by inhibiting inflammation and pyroptosis.

Sea cucumber-derived compounds for treatment of dyslipidemia: A review

Dyslipidemias are disorders of plasma levels of lipids, such as elevated levels of total cholesterol and triglyceride, that are associated with various human diseases including cardiovascular disease (CVD) and non-alcoholic fatty liver disease (NAFLD). Statins are the first-line drugs for treatment of dyslipidemia. However, a substantial proportion of patients cannot reach the recommended LDL-c level even with the highest tolerated doses of statins, and there is no available drug specifically for NAFLD therapy. Sea cucumbers are one of the widely distributed invertebrates, and are an important resource of food and medicine. Sea cucumbers have many valuable nutrients including saponins, fatty acids, phospholipids, cerebrosides, sulfated polysaccharides, as well as proteins and peptides. In recent years, these natural products derived from sea cucumbers have attracted attentions for treatment of CVD and NAFLD because of their lipid-lowering effect and low toxicity. However, the hypolipidemic mechanisms of action and the structure-activity relationship of these bioactive components have not been well-documented in literature. This review article summarizes the signaling pathways and the potential structure-activity relationship of sea cucumber-derived bioactive compounds including saponins, lipids, carbohydrates as well as peptides and proteins. This article will provide information useful for the development of sea cucumber-derived lipid-lowering compounds as well as for investigation of hypolipidemic compounds that are derived from other natural resources.

Cytotoxic capability and the associated proteomic profile of cell-free coelomic fluid extracts from the edible sea cucumber Holothuria tubulosa on HepG2 liver cancer cells

Hepatocellular carcinoma (HCC) is an aggressive cancer histotype and one of the most common types of cancer worldwide. The identification of compounds that might intervene to restrain neoplastic cell growth appears imperative due to its elevated overall mortality. The marine environment represents a reservoir rich in bioactive compounds in terms of primary and secondary metabolites produced by aquatic animals, mainly invertebrates. In the present study, we determined whether the water-soluble cell-free extract of the coelomic fluid (CFE) of the edible sea cucumber Holothuria tubulosa could play an anti-HCC role in vitro by analyzing the viability and locomotory behavior, cell cycle distribution, apoptosis and autophagy modulation, mitochondrial function and cell redox state of HepG2 HCC cells. We showed that CFE causes an early block in the cell cycle at the G2/M phase, which is coupled to oxidative stress promotion, autophagosome depletion and mitochondrial dysfunction ultimately leading to apoptotic death. We also performed a proteomic analysis of CFE identifying a number of proteins that are seemingly responsible for anti-cancer effects. In conclusion, H. tubulosa's CFE merits further investigation to develop novel promising anti-HCC prevention and/or treatment agents and also beneficial supplements for formulation of functional foods and food packaging material.

Application of fucoidan as treatment for cardiovascular and cerebrovascular diseases

Fucoidan is a marine polysaccharide. In recent years, fucoidan has attracted wide-scale attention from the pharmaceutical industries due to its diverse biological activities such as lipid-lowering, anti-atherosclerosis, and anticoagulation. This review clarifies the pharmacological effects of fucoidan in the treatment of human cardiovascular and cerebrovascular diseases. Fucoidan exerts a hypolipidemic effect by increasing the reverse transport of cholesterol, inhibiting lipid synthesis, reducing lipid accumulation, and increasing lipid metabolism. Inflammation, anti-oxidation, and so on have a regulatory effect in the process of atherosclerosis endothelial cells, macrophages, smooth muscle cells, and so on; fucoidan can not only prevent thrombosis through anticoagulation and regulate platelet activation, but also promote the dissolution of formed thrombi. Fucoidan has a neuroprotective effect, and also has a positive effect on the prognosis of the cardiovascular and cerebrovascular. The prospects of applying fucoidan in cardio-cerebrovascular diseases are reviewed to provide some theoretical bases and inspirations for its full-scale development and utilization.

Low Molecular Weight, 4-O-Sulfation, and Sulfation at Meta-Fucose Positively Promote the Activities of Sea Cucumber Fucoidans on Improving Insulin Resistance in HFD-Fed Mice

Fucoidans from sea cucumber (SC-FUC) have been proven to alleviate insulin resistance in several species. However, there are few studies that clarify the relationship between their structure and bioactivity. The present study evaluated the influence of molecular weight (Mw), sulfation concentrations (Cs), and sulfation position on improving insulin resistance using SC-FUC. Results showed that fucoidans with lower Mw exerted stronger effects. Having a similar Mw, Acaudina molpadioides fucoidans (Am-FUC) with lower Cs and Holothuria tubulosa fucoidans with higher Cs showed similar activities. However, Isostichopus badionotus fucoidans (higher Cs) activity was superior to that of low-Mw Thelenota ananas fucoidans (Ta-LFUC, lower Cs). Eliminating the effects of Mw and Cs, the bioactivity of Am-FUC with sulfation at meta-fucose exceeded that of Ta-FUC with sulfation at ortho-position. Moreover, the effects of Pearsonothuria graeffei fucoidans with 4-O-sulfation were superior to those of Am-LFUC with 2-O-sulfation. These data indicate that low Mw, 4-O-sulfation, and sulfation at meta-fucose contributed considerably to insulin resistance alleviation by SC-FUC, which could accelerate the development of SC-FUC as a potential food supplement to alleviate insulin resistance.

Utilizing heterologously overexpressed endo-1,3-fucanase to investigate the structure of sulfated fucan from sea cucumber (Holothuria hilla)

Sea cucumber sulfated fucan (SC-FUC) attracted increasing interests in the recent decades. Endo-1,3-fucanase has been employed in the structural clarification and structure-function relationship investigations of SC-FUC. Nevertheless, the preparation of wild-type endo-1,3-fucanase is costly and time-consuming, which hinders its further utilization. In this study, a heterologously overexpressed endo-1,3-fucanase (FunA) was introduced into structural identification of SC-FUC. FunA was efficiently prepared within one day and utilized in the investigation of sulfated fucan from sea cucumber Holothuria hilla (Hh-FUC). By using enzymatic degradation, glycomics and NMR analysis, the major structure of Hh-FUC was identified to be composed of a tetrasaccharide repeating unit →3-α-l-Fucp-1 → 3-α-l-Fucp2,4(OSO3-)-1 → 3-α-l-Fucp2(OSO3-)-1 → 3-α-l-Fucp2(OSO3-)-1→. Due to the efficient acquisition of enzyme and the superior oligosaccharide recovery, 0.6 mL of E. coli broth and 10 mg of Hh-FUC were sufficient for the structural identification. The results demonstrated the superiority of heterologously overexpressed fucanase over its wild-type enzyme in structural investigation of sulfated fucan.

Diversity, enzyme production and antibacterial activity of Bacillus strains isolated from sesame-flavored liquor Daqu

Daqu provides enzymes and precursors for liquor fermentation, and is the core of liquor fermentation. In this study, 11 Bacillus strains were isolated from sesame-flavored liquor Daqu, which can not only produce protease and amylase, but also have antagonistic effects on common pathogens Escherichia coli and Staphylococcus aureus. According to the gyrA gene phylogeny analysis, these 11 Bacillus strains belong to three species, B1, Y14, Y15, and YPDW9 belong to Bacillus mojavensis, W7, W13, YPDW6, and YPDW12 belong to Bacillus subtilis, and W14, Y5, and YPDW1 belong to Bacillus velezensis. According to the results of random amplified polymorphic DNA (RAPD) typing, there are three strains in Bacillus mojavensis, among which Y14 and Y15 are the same ones. All four Bacillus subtilis strains and three Bacillus velezensis strains are different. The specific primers were used to randomly amplify the biological control genes expressing lipopeptide antibiotics (bioA, bmyB, ituC, fenD, srfAA, srfAB, yngG,and yndJ), and the results showed that antagonistic genes other than fenD gene were amplified in four Bacillus mojavensis strains; Bacillus subtilis amplification was significantly different, but srfAA, bmyB and yndJ genes were all present; All genes were amplified in Bacillus velezensis except YPDW1 without ituC. This research provides new ideas for strengthening Daqu and lays a foundation for improving the quality of liquor.