Fucoidan from Ascophyllum nodosum Suppresses Postprandial Hyperglycemia by Inhibiting Na+/Glucose Cotransporter 1 Activity

Fucoidan from Ascophyllum nodosum and Undaria pinnatifida attenuate SARS-CoV-2 infection in vitro and in vivo by suppressing ACE2 and alleviating inflammation

The global healthcare challenge posed by COVID-19 necessitates the continuous exploration for novel antiviral agents. Fucoidans have demonstrated antiviral activity. However, the underlying structure-activity mechanism responsible for the inhibitory activity of fucoidans from Ascophyllum nodosum (FUCA) and Undaria pinnatifida (FUCU) against SARS-CoV-2 remains unclear. FUCA was characterized as a homopolymer with a backbone structure of repeating (1 → 3) and (1 → 4) linked α-l-fucopyranose residues, whereas FUCU was a heteropolysaccharide composed of Fuc1-3Gal1-6 repeats. Furthermore, FUCA demonstrated significantly higher anti-SARS-CoV-2 activity than FUCU (EC50: 48.66 vs 69.52 μg/mL), suggesting the degree of branching rather than sulfate content affected the antiviral activity. Additionally, FUCA exhibited a dose-dependent inhibitory effect on ACE2, surpassing the inhibitory activity of FUCU. In vitro, both FUCA and FUCU treatments downregulated the expression of pro-inflammatory cytokines (IL-6, IFN-α, IFN-γ, and TNF-α) and anti-inflammatory cytokines (IL-10 and IFN-β) induced by viral infection. In hamsters, FUCA demonstrated greater effectiveness in attenuating lung and gastrointestinal injury and reducing ACE2 expression, compared to FUCU. Analysis of the 16S rRNA gene sequencing revealed that only FUCU partially alleviated the gut microbiota dysbiosis caused by SARS-CoV-2. Consequently, our study provides a scientific basis for considering fucoidans as poteintial prophylactic food components against SARS-CoV-2.

Ascophyllum nodosum (Linnaeus) Le Jolis from Arctic: Its Biochemical Composition, Antiradical Potential, and Human Health Risk

Ascophyllum nodosum is a brown seaweed common in Arctic tidal waters. We have collected A. nodosum samples from the Barents Sea (BS), Irminger Sea (IS), and Norwegian Sea (NS) in different reproductive stages and have evaluated their biochemical composition, radical scavenging potential, and health risks. The total content of dominating carbohydrates (fucoidan, mannitol, alginate, and laminaran) ranged from 347 mg/g DW in NS to 528 mg/g DW in BS. The proportion of two main structural monosaccharides of fucoidan (fucose and xylose) differed significantly between the seas and reproductive phase, reaching a maximum at the fertile phase in the BS sample. Polyphenols and flavonoids totals were highest in NS A. nodosum samples and increased on average in the following order: BS < IS < NS. A positive correlation of free radical scavenging activity for seaweed extracts with polyphenols content was observed. The concentration of elements in A. nodosum from the Arctic seas region was in the following order: Ca > Mg > Sr > Fe > Al > Zn > As total > Rb > Mn > Ba > Cu > Co. Seaweeds from BS had the lowest metal pollution index (MPI) of 38.4. A. nodosum from IS had the highest MPI of 83. According to the calculated target hazard quotient (THQ) and hazard index (HI) values, Arctic A. nodosum samples pose no carcinogenic risk to adult and child health and are safe for regular consumption. Our results suggest that the Arctic A. nodosum has a remarkable potential for food and pharmaceutical industries as an underestimated source of polysaccharides, polyphenols, and flavonoids.

Lowering glycemic levels via gastrointestinal tract factors: the roles of dietary fiber, polyphenols, and their combination

Dietary fiber (DF) and polyphenols (DP) are typical blood sugar-lowering components, and both play distinct yet interconnected roles in exerting their blood sugar-lowering effects. We comprehensively summarized the single and combined effects of DF and DP on blood glucose homeostasis through regulating the relevant factors in the upper gastrointestinal tract (UGT) and lower gastrointestinal tract (LGT). In the UGT, DF slowed down glucose metabolism by enhancing digesta viscosity and hindering enzyme-substrate interaction. DP primarily targeted enzymes and substrates. When combined, DP enhanced the adsorption capacity of DF for glucose. DF weakened DP's inhibitory effect on enzymes. Both DF and DP disrupted glucose intestinal uptake via physical or genomic modulation, but the co-consumption of DF and DP demonstrated a lower inhibitory effect on glucose uptake than DP alone. In the LGT, DF and DP showed synergistic or antagonistic effects on gut microbiota. Remarkably, whole foods exhibited potent prebiotic effects due to their compound-rich matrix, potentially enhancing glucose homeostasis and expanding dietary options for glucose regulation research.

Production of high- and low-molecular weight fucoidan fragments with defined sulfation patterns and heightened in vitro anticancer activity against TNBC cells using novel endo-fucanases of the GH107 family

Fucoidans are complex fucose-containing sulfated polysaccharides with pronounced anticancer effects. Their structure-anticancer activity relationships are difficult to determine due to fucoidans' complex, often irregularities-including structures. Fucoidan-active enzymes can be used for this propose. We have investigated two new recombinant endo-fucanases FWf3 and FWf4 from the marine bacterium Wenyingzhuangia fucanilytica CZ1127^T that belong to the 107 family of glycoside hydrolases (GH). Both enzymes cleaved α-(1→4)-glycosidic bonds but in fucoidan fragments with different sulfation patterns. FWf3 is the first characterized endo-fucanase that cleaves glycosidic bonds between 2O- and 2,4diO-sulfated L-fucose residues. The obtained endo-fucanases were used to produce low- and high-molecular weight fucoidan derivatives with different sulfate group locations. Low- and high-molecular weight fucoidan derivatives rich with 2,4diO-sulfation were shown to inhibit MDA-MB-231 cell colony formation more efficiently than the native fucoidan and the derivatives sulfated otherwise. Such derivatives effectively suppressed the mitochondrial membrane potential of MDA-MB-231 cells and reduced the expression of the glucose transporter 1 (GLUT1). Co-treatment of MDA-MB-231 cells with the fucoidan derivatives and oligomycin (an OXPHOS inhibitor) resulted in a synergistic anticancer effect. The data obtained demonstrate, that fucoidan and its 2,4diO-sulfated derivatives can be an effective adjunct in TNBC therapy targeting cell metabolism.

Structure and Metabolically Oriented Efficacy of Fucoidan from Brown Alga Sargassum muticum in the Model of Colony Formation of Melanoma and Breast Cancer Cells

This work reports the detailed structure of fucoidan from Sargassum miticum (2SmF2) and its ability to potentiate the inhibitory effect of glycolysis inhibitor 2-deoxy-d-glucose (2-DG). 2SmF2 was shown to be sulfated and acetylated galactofucan containing a main chain of alternating residues of 1,3- and 1,4-linked α-l-fucopyranose, fucose fragments with monotonous 1,3- and 1,4-type linkages (DP up to 3), α-d-Gal-(1→3)-α-L-Fuc disaccharides, and 1,3,4- and 1,2,4-linked fucose branching points. The sulfate groups were found at positions 2 and 4 of fucose and galactose residues. 2SmF2 (up to 800 µg/mL) and 2-DG (up to 8 mM) were not cytotoxic against MDA-MB-231 and SK-MEL-28 as determined by MTS assay. In the soft agar-based model of cancer cell colony formation, fucoidan exhibited weak inhibitory activity at the concentration of 400 µg/mL. However, in combination with low non-cytotoxic concentrations of 2-DG (0.5 or 2 mM), 2SmF2 could effectively inhibit the colony formation of SK-MEL-28 and MDA-MB-231 cells and decreased the number of colonies by more than 50% compared to control at the concentration of 200 µg/mL. Our findings reveal the metabolically oriented effect of fucoidan in combination with a glycolysis inhibitor that may be beneficial for a therapy for aggressive cancers.

The Combined Metabolically Oriented Effect of Fucoidan from the Brown Alga Saccharina cichorioides and Its Carboxymethylated Derivative with 2-Deoxy-D-Glucose on Human Melanoma Cells

Melanoma is the most aggressive and treatment-resistant form of skin cancer. It is phenotypically characterized by aerobic glycolysis that provides higher proliferative rates and resistance to cell death. The glycolysis regulation in melanoma cells by means of effective metabolic modifiers represents a promising therapeutic opportunity. This work aimed to assess the metabolically oriented effect and mechanism of action of fucoidan from the brown alga Saccharina cichorioides (ScF) and its carboxymethylated derivative (ScFCM) in combination with 2-deoxy-D-glucose (2-DG) on the proliferation and colony formation of human melanoma cell lines SK-MEL-28, SK-MEL-5, and RPMI-7951. The metabolic profile of melanoma cells was determined by the glucose uptake and Lactate-GloTM assays. The effect of 2-DG, ScF, ScFCM, and their combination on the proliferation, colony formation, and activity of glycolytic enzymes was assessed by the MTS, soft agar, and Western blot methods, respectively. When applied separately, 2-DG (IC50 at 72 h = 8.7 mM), ScF (IC50 at 72 h > 800 µg/mL), and ScFCM (IC50 at 72 h = 573.9 μg/mL) inhibited the proliferation and colony formation of SK-MEL-28 cells to varying degrees. ScF or ScFCM enhanced the inhibiting effect of 2-DG at low, non-toxic concentrations via the downregulation of Glut 1, Hexokinase II, PKM2, LDHA, and pyruvate dehydrogenase activities. The obtained results emphasize the potential of the use of 2-DG in combination with algal fucoidan or its derivative as metabolic modifiers for inhibition of melanoma SK-MEL-28 cell proliferation.

Fucoidan from Fucus vesiculosus prevents the loss of dopaminergic neurons by alleviating mitochondrial dysfunction through targeting ATP5F1a

Parkinson's disease is a neurodegenerative disease that is characterized by the loss of dopaminergic neurons. Fucoidan, which has emerged as a neuroprotective agent, is a marine-origin sulfated polysaccharide enriched in brown algae and sea cucumbers. However, variations in structural characteristics exist among fucoidans derived from different sources, resulting in a wide spectrum of biological effects. It is urgent to find the fucoidan with the strongest neuroprotective effect, and the mechanism needs to be further explored. We isolated and purified four different fucoidan species with different chemical structures and found that Type II fucoidan from Fucus vesiculosus (FvF) significantly improved mitochondrial dysfunction, prevented neuronal apoptosis, reduced dopaminergic neuron loss, and improved motor deficits in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Further mechanistic investigation revealed that the ATP5F1a protein is a key target responsible for alleviating mitochondrial dysfunction of FvF to exert neuroprotective effects. This study highlights the favorable properties of FvF for neuroprotection, making FvF a promising candidate for the treatment of PD.

Interaction of High-Molecular Weight Fucoidan from Laminaria hyperborea with Natural Functions of the Retinal Pigment Epithelium

Fucoidans are polysaccharides and constituents of cell walls of brown algae such as Laminaria hyperborea (LH). They exhibit promising effects regarding age-related macular degeneration (AMD). However, the safety of this compound needs to be assured. The focus of this study lies on influences of an LH fucoidan on the retinal pigment epithelium (RPE). The high-molecular weight LH fucoidan Fuc1 was applied to primary porcine RPE cells, and a tetrazolium (MTT) cell viability assay was conducted. Further tests included a scratch assay to measure wound healing, Western blotting to measure expression of retinal pigment epithelium-specific 65 kDa protein (RPE65), as well as immunofluorescence to measure uptake of opsonized fluorescence beads into RPE cells. Lipopolysaccharide was used to proinflammatorily activate the RPE, and interleukin 6 (IL-6) and interleukin 8 (IL-8) secretion was measured. RPE/choroid cultures were used to assess vascular endothelial growth factor (VEGF) secretion. Real-time polymerase chain reaction (real-time PCR) was performed to detect the gene expression of 91 different genes in a specific porcine RPE gene array. Fuc1 slightly reduced wound healing, but did not influence cell viability, phagocytosis or RPE65 expression. Fuc1 lowered IL-6, IL-8 and VEGF secretion. Furthermore, Fuc1 did not change tested RPE genes. In conclusion, Fuc1 does not impair RPE cellular functions and shows antiangiogenic and anti-inflammatory activities, which indicates its safety and strengthens its suitability concerning ocular diseases.

Structure and hypoglycemic effect of a neutral polysaccharide isolated from sea cucumber Stichopus japonicus

In addition to its high nutritious value, sea cucumber has been recognized by folk medicine for a long time. This study investigated the structure and hyperglycemic activity of a neutral polysaccharide (NPsj) from sea cucumber Stichopus japonicus, whose molecular weight was determined as 301.75 kDa by HPGPC method. Monosaccharide composition analysis indicated that NPsj is a glucan. The structure of NPsj was obtained by combining the analysis of methylation analysis, FTIR, NMR, periodate oxidation, Smith degradation and ESI-MS, which is mainly composed of (1 → 4)-α-d-glucoses with β-d-glucose(1→) branches substituted at O-6 every 7-9 of 1,4 linked glucoses. An in vitro insulin resistance Hep G2 cells model and a 3 T3-L1 cells model were established, and the NPsj has significant effect to increase glucose consumption with no toxicity at 10-100 μg/mL. Furthermore, NPsj upregulates the phosphorylation of Akt1 and down-regulated GSK3β, and then reduces the phosphorylation of GS, indicating its mechanism of ameliorating insulin resistance via Akt/GSK3β/GS signaling pathway.

Protective effects of fucoidan against kidney diseases: Pharmacological insights and future perspectives

Chronic kidney disease (CKD) is a major public health concern that costs millions of lives worldwide. Natural products are consistently being explored for the development of novel therapeutics in the management of CKD. Fucoidan is a sulfated polysaccharide predominantly extracted from brown seaweed, which has multiple pharmacological benefits against various kidney problems, including chronic renal failure and diabetic nephropathy. This review aimed at exploring literature to update the renoprotective effects of fucoidan, to get an understanding of pharmacological mechanisms, and to highlight the recent progress of fucoidan-based therapeutic development. Evidence shows that fucoidan is effective against inflammation, oxidative stress, and fibrosis in kidney. Fucoidan targets multiple signaling systems, including Nrf2/HO-1, NF-κB, ERK and p38 MAPK, TGF-β1, SIRT1, and GLP-1R signaling that are known to be associated with CKD pathobiology. Despite these pharmacological prospects, the application of fucoidan is limited by its larger molecular size. Notably, low molecular weight fucoidan has shown therapeutic promise in some recent studies. However, future research is warranted to translate the outcome of preclinical studies into clinical use in kidney patients.

Targeting Glucose Transport Proteins for Diabetes Management: Regulatory Roles of Food-Derived Compounds

With the rapid rise in prevalence, diabetes mellitus is one of the leading causes of mortality worldwide. Impaired cellular glucose transport is a major contributor to diabetes progression and, thus, an important target for treatment. Functional foods are a rich source of antidiabetic agents. These compounds target multiple physiological contributors to diabetes with lower risk for side effects. This perspective highlights recent advances in food-derived compounds that regulate the gene expression or activity of glucose transport proteins (SGLT1, SGLT2, GLUT1, GLUT2, and GLUT4) and provides insights for future research on targeting the transporters as a promising antidiabetic mechanism of nutraceutical compounds.

Fucoidan ameliorates glucose metabolism by the improvement of intestinal barrier and inflammatory damage in type 2 diabetic rats

It has been reported that fucoidan possesses anti-diabetic activities by inhibiting α-glucosidase activity, improving β-cell dysfunction, and enhancing insulin sensitivity. However, as a macromolecular carbohydrate, fucoidan is rarely absorbed and indigestible in gastrointestinal tract. The study aimed to explore whether the fucoidan can regulate glucose metabolism by improving intestinal barrier and inflammation in type 2 diabetes mellitus (T2DM) rats. A high-fat diet combined with streptozotocin was used to induce T2DM rats. Different doses of fucoidan (50, 100 and 200 mg/kg) were administered respectively by lavage to T2DM rats for 8 weeks and saline was given to controls. The results showed that in addition to hyperglycemia and hyperlipidemia, T2DM rats were also characterized by increased intestinal permeability and proinflammatory cytokines. Notably, fucoidan reduced fasting blood glucose and insulin resistance index along with alleviated the accumulation of proinflammatory cytokines in T2DM rats. Furthermore, fucoidan repaired the intestinal barrier function, which was accompanied by the up-regulation of tight junction proteins and the improvement of intestinal inflammation via inhibiting TLR4/NF-κB signaling. Meanwhile, fucoidan also mitigated the liver damage, and alleviated insulin resistance by activating PI3K/AKT signaling. Collectively, these findings supported the potential of fucoidan to be used as a functional ingredient to prevent T2DM.

Regulation of the unfolded protein response transducer IRE1α by SERPINH1 aggravates periodontitis with diabetes mellitus via prolonged ER stress

The hyperglycemic microenvironment induced by diabetes mellitus aggravates the inflammatory response, in which the IRE1α signal transduction pathway of the unfolded protein response (UPR) participates. However, the mechanism by which hyperglycemia regulates the IRE1α signaling pathway and affects endoplasmic reticulum (ER) homeostasis in human gingival epithelium in periodontitis with diabetes mellitus remains unknown. Our current data provide evidence that diabetes mellitus causes a hyperinflammatory response in the gingival epithelium, which accelerates periodontal inflammation. Next, we assessed UPR-IRE1α signaling in periodontitis with diabetes mellitus by examining human clinical gingival epithelium samples from healthy subjects, subjects with periodontitis and subjects with periodontitis with diabetes mellitus and by in vitro challenge of human epithelial cells with a hyperglycemic microenvironment. The results showed that a hyperglycemic microenvironment inhibited the IRE1α/XBP1 axis, decreased the expression of a UPR target gene (GRP78), and ultimately impaired the UPR, causing ER stress to be prolonged or more severe in human gingival epithelium. Subsequently, RNA sequencing (RNA-seq) data was analyzed to investigate the expression of ER-related genes in human gingival epithelium. Experiments verified that the mechanism by which periodontitis is aggravated in individuals with diabetes mellitus may involve decreased SERPINH1 expression. Furthermore, experiments in SERPINH1-knockdown and SERPINH1-overexpression models established in vitro indicated that SERPINH1 might act as an activator of IRE1α, maintaining human gingival epithelium homeostasis and reducing proinflammatory cytokine expression by preventing prolonged ER stress induced by high-glucose conditions. In conclusion, regulation of the UPR transducer IRE1α by SERPINH1 alleviates periodontitis with diabetes mellitus by mitigating prolonged ER stress. This finding provides evidence for the further study of periodontitis with diabetes mellitus.

Fucoidan protects pancreas and improves glucose metabolism through inhibiting inflammation and endoplasmic reticulum stress in T2DM rats

It is important to maintain the normal function of pancreas in the prevention and intervention of type 2 diabetes mellitus (T2DM). This study was undertaken to explore the protective effects...

Fucoidans as Scientifically and Commercially Important Algal Polysaccharides

As a highly bioactive seaweed substance with many promising physiological activities, fucoidan has attracted attention from many industries all over the world [...].