Protective effect and mechanism of fucoidan on intestinal mucosal barrier function in NOD mice

Alginate oligosaccharide improves 5-fluorouracil-induced intestinal mucositis by enhancing intestinal barrier and modulating intestinal levels of butyrate and isovalerate

Chemotherapy-induced mucositis (CIM) is the typical side effect of chemotherapy. This study investigates the potential of alginate oligosaccharide (AOS) in ameliorating CIM induced by 5-fluorouracil (5-FU) in a murine model and its underlying mechanisms. AOS effectively mitigated body weight loss and histopathological damage, modulated inflammatory cytokines and attenuated the oxidative stress. AOS restored intestinal barrier integrity through enhancing expression of tight junction proteins via MLCK signaling pathway. AOS alleviated intestinal mucosal damage by inhibiting TLR4/MyD88/NF-κB signaling pathway, downregulating the pro-apoptotic protein Bax and upregulating the anti-apoptotic protein Bcl-2. Moreover, AOS significantly enriched intestinal Akkermansiaceae and increased the production of short-chain fatty acids (SCFAs), most notably butyrate and isovalerate. Pre-treatment with butyrate and isovalerate also alleviated 5-FU-induced CIM. In conclusion, AOS effectively mitigated CIM through strenghthening intestinal barrier, attenuating inflammation, and modulating gut microbiota and intestianl levels of butyrate and isovalerate. These finding indicate that AOS could be potentially utilized as a supplemental strategy for prevention or mitigation of CIM.

Influence of intestinal microecology in the development of gout or hyperuricemia and the potential therapeutic targets

Gout and hyperuricemia are common metabolic diseases. Patients with purine metabolism disorder and/or decreased uric acid excretion showed increased uric acid levels in the blood. The increase of uric acid in the blood leads to the deposition of urate crystals in tissues, joints, and kidneys, and causes gout. Recent studies have revealed that imbalance of the intestinal microecology is closely related to the occurrence and development of hyperuricemia and gout. Disorder of the intestinal flora often occurs in patients with gout, and high purine and high fructose may induce the disorder of intestinal flora. Short-chain fatty acids and endotoxins produced by intestinal bacteria are closely related to the inflammatory response of gout. This article summarizes the characteristics of intestinal microecology in patients or animal models with hyperuricemia or gout, and explores the relationship between intestinal microecology and gout or hyperuricemia from the aspect of the intestinal barrier, intestinal microorganisms, intestinal metabolites, and intestinal immune system. We also review the current status of hyperuricemia treatment by targeting intestinal microecology.

Dendrobium officinale Polysaccharide Alleviates Type 2 Diabetes Mellitus by Restoring Gut Microbiota and Repairing Intestinal Barrier via the LPS/TLR4/TRIF/NF-kB Axis

Dendrobium officinale polysaccharide (DOP), the main active component, has a variety of bioactivities. In this study, a type 2 diabetes mellitus (T2DM) and antibiotic-induced pseudo-germ-free mouse models were used to investigate the hypoglycemic mechanisms of DOP. The findings showed that DOP ameliorated dysfunctional glucolipid metabolism, lipopolysaccharide (LPS) leakage, and metabolic inflammation levels in T2DM mice. Furthermore, DOP significantly upregulated the mRNA expression of tight junction proteins Claudin-1, Occludin, and ZO-1 and reduced intestinal inflammation and oxidative stress damage through the LPS/TLR4/TRIF/NF-κB axis to repair the intestinal barrier. Interestingly, pseudo-germ-free mouse experiments confirmed that the above beneficial effects of DOP were dependent on gut microbiota. 16S rRNA analysis showed that DOP strongly inhibited the harmful bacterium Helicobacter by 94.57% and facilitated the proliferation of probiotics Allobaculum, Bifidobacterium, and Lactobacillus by 34.96, 139.41, and 88.95%, respectively. Therefore, DOP is capable of rebuilding certain specific intestinal microbiota to restore intestinal barrier injury, which supports the utilization of DOP as a new type of prebiotic in functional foods for T2DM.

Research Progress on the Protective Effect of Brown Algae-Derived Polysaccharides on Metabolic Diseases and Intestinal Barrier Injury

In the human body, the intestine is the largest digestive and immune organ, where nutrients are digested and absorbed, and this organ plays a key role in host immunity. In recent years, intestinal health issues have gained attention and many studies have shown that oxidative stress, inflammation, intestinal barrier damage, and an imbalance of intestinal microbiota may cause a range of intestinal diseases, as well as other problems. Brown algae polysaccharides, mainly including alginate, fucoidan, and laminaran, are food-derived natural products that have received wide attention from scholars owing to their good biological activity and low toxic side effects. It has been found that brown algae polysaccharides can repair intestinal physical, chemical, immune and biological barrier damage. Principally, this review describes the protective effects and mechanisms of brown algae-derived polysaccharides on intestinal health, as indicated by the ability of polysaccharides to maintain intestinal barrier integrity, inhibit lipid peroxidation-associated damage, and suppress inflammatory cytokines. Furthermore, our review aims to provide new ideas on the prevention and treatment of intestinal diseases and act as a reference for the development of fucoidan as a functional product for intestinal protection.

Water Extract of Ecklonia cava Protects against Fine Dust (PM2.5)-Induced Health Damage by Regulating Gut Health

To confirm the therapeutic effect of the water extract from Ecklonia cava (WEE) against PM_2.5 induced systemic health damage, we evaluated gut health with a focus on the microbiota and metabolites. Systemic damage in mice was induced through PM_2.5 exposure for 12 weeks in a whole-body chamber. After exposure for 12 weeks, body weight and food intake decreased, and WEE at 200 mg/kg body weight (mpk) alleviated these metabolic efficiency changes. In addition, PM_2.5 induced changes in the length of the colon and fecal water content. The administration of the WEE at 200 mpk oral dose effectively reduced changes in the colon caused by PM_2.5 exposure. We also attempted to confirm whether the effect of the WEE is mediated via regulation of the microbiota-gut-brain axis in mice with PM_2.5 induced systemic damage. We examined changes in the fecal microbiota and gut metabolites such as short-chain fatty acids (SCFAs) and kynurenine metabolites. In the PM_2.5 exposed group, a decrease in the abundance of Lactobacillus (Family: Lactobacillaceae) and an increase in the abundance of Alistipes (Family: Rikenellaceae) were observed, and the administration of the WEE showed a beneficial effect on the gut microbiota. In addition, the WEE effectively increased the levels of SCFAs (acetate, propionate, and butyrate). Furthermore, kynurenic acid (KYNA), which is a critical neuroprotective metabolite in the gut-brain axis, was increased by the administration of the WEE. Our findings suggest that the WEE could be used as a potential therapeutic against PM_2.5 induced health damage by regulating gut function.

Porphyra tenera Protects against PM2.5-Induced Cognitive Dysfunction with the Regulation of Gut Function

To evaluate the biological effects of Porphyra tenera (P. tenera), we tried to confirm the possibility that the intake of P. tenera could modulate cognitive and intestinal functions in PM_2.5-induced cognitive decline mice. P. tenera attenuated PM_2.5-induced learning and memory impairment through antioxidant and anti-inflammatory effects by regulating the mitochondrial function and TLR-initiated NF-κB signaling. In addition, P. tenera effectively alleviated Aβ production/tau phosphorylation by inhibiting the JNK phosphorylation. Also, the bioactive constituents of P. tenera determined the sulfated galactan, mycosporine-like amino acids (MAAs), and chlorophyll derivatives. Moreover, the bioactive compounds of P. tenera by gut fermentation protected against gut dysbiosis and intestinal tight junction damage with a decrease in inflammatory response and short-chain fatty acid production. Based on these results, our findings suggest that P. tenera with sulfated galactan and MAAs is a potential material for cognitive function improvement.

Fucoidan Is Not Completely Dependent on Degradation to Fucose to Relieve Ulcerative Colitis

Recently, fucoidan has been proposed for use as a potential anti-inflammatory drug. The purpose of this study was to investigate the mechanism of fucoidan in the treatment of ulcerative colitis. We compared the anti-inflammatory effects of fucoidan and fucose induced by dextran sulfate sodium, and the effects of fucoidan and fucose on the gut microbiota of mice. Our results showed that low-dose fucoidan significantly improved weight loss, disease activity index scores, colonic shortening, colonic histopathological damage, intestinal fatty acid binding protein 2 levels, and the expression of Occludin, Claudin-4, and Claudin-1. However, both high-dose fucoidan and fucose did not perform as well as low-dose fucoidan as described above. In addition, 16S rDNA high-throughput sequencing showed that low-dose fucoidan significantly increased the abundance of Alloprevotella, and fucose significantly increased Ruminococcaceae, but neither significantly reversed the imbalance in the gut microbiota. Therefore, we inferred that the regulation of fucoidan on colitis has a unique and complex mechanism, and it is not completely dependent on degradation to fucose to relieve ulcerative colitis, nor is it achieved only by regulating the gut microbiota. The mechanism by which fucoidan treats colitis may also include reducing inflammatory cell infiltration and increasing intestinal barrier function.

Application of Fucoidan in Caco-2 Model Establishment

The Caco-2 model is a common cell model for material intestinal absorption in vitro, which usually takes 21 days to establish. Although some studies have shown that adding puromycin (PM) can shorten the model establishment period to 7 days, this still requires a long modeling time. Therefore, exploring a shorter modeling method can reduce the experimental costs and promote the development and application of the model. Fucoidan is an acidic polysaccharide with various biological activities. Our study showed that the transepithelial electrical resistance (TEER) value could reach 600 Ω·cm2 on the fourth day after the addition of fucoidan and puromycin, which met the applicable standards of the model (>500 Ω). Moreover, the alkaline phosphatase (AKP) activity, fluorescein sodium transmittance, and cell morphology of this model all met the requirements of model establishment. Fucoidan did not affect the absorption of macromolecular proteins and drugs. The results indicate that fucoidan can be applied to establish the Caco-2 model and can shorten the model establishment period to 5 days.

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.

Protective Effects of Natural Polysaccharides on Intestinal Barrier Injury: A Review

Owing to their minimal side effects and effective protection from oxidative stress, inflammation, and malignant growth, natural polysaccharides (NPs) are a potential adjuvant therapy for several diseases caused by intestinal barrier injury (IBI). More studies are accumulating on the protective effects of NPs with respect to IBI, but the underlying mechanisms remain unclear. Thus, this review aims to represent current studies that investigate the protective effects of NPs on IBI by directly maintaining intestinal epithelial barrier integrity (inhibiting oxidative stress, regulating inflammatory cytokine expression, and increasing tight junction protein expression) and indirectly regulating intestinal immunity and microbiota. Furthermore, the mechanisms underlying IBI development are briefly introduced, and the structure-activity relationships of polysaccharides with intestinal barrier protection effects are discussed. Potential developments and challenges associated with NPs exhibiting protective effects against IBI have also been highlighted to guide the application of NPs in the treatment of intestinal diseases caused by IBI.

The Role of Gut Microbiota in the Progression of Parkinson's Disease and the Mechanism of Intervention by Traditional Chinese Medicine

Parkinson's disease (PD) is a common degenerative disease of the nervous system that seriously affects the quality of life of the patients. The pathogenesis of PD is not yet fully clear. Previous studies have confirmed that patients with PD exhibit obvious gut microbiota imbalance, while intervention of PD by regulating the gut microbiota has become an important approach to the prevention and treatment of this disease. Traditional Chinese medicine (TCM) has been shown to be safe and effective in treating PD. It has the advantages of affecting multiple targets. Studies have shown TCM can regulate gut microbiota. However, the specific mechanism of action is still unclear. Therefore, this article will mainly discuss the association of the alteration of the gut microbiota and the incidence of PD, the advantages of TCM in treating PD, and the mechanism of regulating gut microbiota by TCM to treat PD. It will clarify the target and mechanism of TCM treating PD by acting gut microbiota and provided a novel methodology for the prevention and treatment of PD.

Hypoglycemic effect of polysaccharide from Astragalus membranaceus on type 2 diabetic mice based on “gut microbiota-mucosal barrier”

Astragalus membranaceus polysaccharide (APP), the main active constituent possesses numerous bioactivities. In this research, the T2DM model mice was combined with streptozotocin to study the hypoglycemic effect and mechanism of...

Protective effect of dexmedetomidine on intestinal mucosal barrier function in rats after cardiopulmonary bypass

Cardiopulmonary bypass can result in damage to the intestines, leading to the occurrence of systemic inflammatory response syndrome. Dexmedetomidine is reported to confer anti-inflammatory properties. Here, the purpose of this study is to investigate the effect of dexmedetomidine on the intestinal mucosa barrier damage in a rat model of cardiopulmonary bypass. It was observed that cardiopulmonary bypass greatly decreased the levels of hemodynamic parameters than SHAM group, whereas dexmedetomidine pretreatment in a cardiopulmonary bypass model rat prevented this reduction. Also, it showed that compared with control animals, cardiopulmonary bypass caused obvious mucosal damage, which was attenuated in dexmedetomidine + cardiopulmonary bypass group. The above findings were in line with that of dexmedetomidine pretreatment, which increased the expression of tight junction proteins, but it decreased the levels of DAO, D-LA, FABP2, and endotoxin. Moreover, the results demonstrated that due to pre-administration of dexmedetomidine, the level of pro-inflammatory factors was decreased, while the level of anti-inflammatory cytokine was increased. Also, it showed that dexmedetomidine suppressed TLR4/JAK2/STAT3 pathway that was activated by cardiopulmonary bypass. Together, these results revealed that dexmedetomidine pretreatment relieves intestinal microcirculation, attenuates intestinal damage, and inhibits the inflammatory response of cardiopulmonary bypass model rats, demonstrating that in CPB-induced damage of intestinal mucosal barrier function, dexmedetomidine pretreatment plays a protective role by inactivating TLR4/JAK2/STAT3-mediated inflammatory pathway.

Metabolic regulation mechanism of fucoidan via intestinal microecology in diseases

The intestinal microecology is an extremely complex ecosystem consisting of gut microbiota, intestinal mucosa and the intestinal immune system. The intestinal microecology performs several important functions and is considered to be an essential 'organ' because it plays an important role in regulating human metabolism. Fucoidan contains a large amount of fucose and galactose residues, as well as various other neutral and acidic monosaccharides. Fucoidan particularly effects tumors, inflammatory bowel disease, diabetes and obesity by repairing intestinal mucosal damage and improving the intestinal microecological environment. It has been proposed that fucoidan could be used as a prebiotic agent for pharmaceutical and functional foods. In this review, we elucidate the potential mechanisms of the metabolic regulation of fucoidan with respect to the intestinal microecology of diseases. © 2021 Society of Chemical Industry.

Aureusidin derivative CNQX inhibits chronic colitis inflammation and mucosal barrier damage by targeting myeloid differentiation 2 protein

Our previous study has found that aureusidin can inhibit inflammation by targeting myeloid differentiation 2 (MD2) protein. Structural optimization of aureusidin gave rise to a derivative named CNQX. LPS was used to induce inflammation in intestinal macrophages; flow cytometry, PI staining and Hoechst 33342 staining were used to detect the apoptotic level of macrophages; enzyme-linked immunosorbent assay (ELISA) was utilized to detect the expression level of inflammatory factors (including IL-1β, IL-18 and TNF-α); immunofluorescence staining was used to investigate the expression of MD2; Western blot was employed to measure the protein level of TLR4, MD2, MyD88 and p-P65. As a result, CNQX with IC50 of 2.5 μM can significantly inhibit the inflammatory damage of macrophages, decrease apoptotic level, reduce the expression level of inflammatory factors and simultaneously decrease the expression level of TLR4, MD2, MyD88 as well as p-P65. Caco-2 cell line was used to simulate the intestinal mucosal barrier in vitro, LPS was employed to induce cell injury in Caco-2 (to up-regulate barrier permeability), and CNQX with IC50 of 2.5 μl was used for intervention. Flow cytometry was used to detect the apoptotic level of Caco-2 cells, trans-epithelial electric resistance (TEER) was measured, FITC-D was used to detect the permeability of the intestinal mucosa, and Western blot was used to detect the expression levels of tight junction proteins (including occludin, claudin-1, MyD88, TLR4 and MD2). As a result, CNQX decreased the apoptotic level of Caco-2 cells, increased TEER value, decreased the expression levels of MyD88, TLR4 and MD2, and increased the protein levels of tight junction proteins (including occludin and claudin-1). C57BL/6 wild-type mice were treated with drinking water containing Dextran sulphate sodium (DSS) to establish murine chronic colitis model. After CQNX intervention, we detected the bodyweight, DAI score and H&E tissue staining to evaluate the life status and pathological changes. Immunohistochemistry (IHC) staining was used to detect the expression of MD2 protein, tight junction protein (including occludin and claudin-1). Transmission electron microscopy and FITC-D were used to detect intestinal mucosal permeability. Western blot was used to detect the expression levels of tight junction proteins (including occludin, claudin-1, MyD88, TLR4 and MD2) in the intestinal mucosa tissue. Consequently, CNQX can inhibit the intestinal inflammatory response in mice with colitis, inhibit the mucosal barrier injury, increase the expression of tight junction proteins (including occludin and claudin-1) and decrease the expression levels of MyD88, TLR4 and MD2. Mechanistically, pull-down and immunoprecipitation assays showed that CNQX can inhibit the activation of TLR4/MD2-NF-κB by binding to MD2 protein. Collectively, in this study, we found that CNQX can suppress the activation of TLR4 signals by targeting MD2 protein, thereby inhibiting inflammation and mucosal barrier damage of chronic colitis.