Production Inhibition and Excretion Promotion of Urate by Fucoidan from Laminaria japonica in Adenine-Induced Hyperuricemic Mice

Uptake and Biotransformation of Guvermectin in Three Crops after In Vivo and In Vitro Exposure

Guvermectin, as a novel nucleoside-like biopesticide, could increase the rice yield excellently, but the potential environmental behaviors remain unclear, which pose potential health risks. Therefore, the uptake and biotransformation of guvermectin in three types of crops (rice, lettuce, and carrot) were first evaluated with a hydroponic system. Guvermectin could be rapidly absorbed and reached equilibrium in roots (12-36 h) and shoots (24-60 h) in three plants, and guvermectin was also vulnerable to dissipation in roots (t1/2 1.02-3.65 h) and shoots (t1/2 9.30-17.91 h). In addition, 8 phase I and 2 phase II metabolites, transformed from guvermectin degradation in vivo and in vitro exposure, were identified, and one was confirmed as psicofuranine, which had antibacterial and antitumor properties; other metabolites were nucleoside-like chemicals. Molecular simulation and quantitative polymerase chain reaction further demonstrated that guvermectin was metabolized by the catabolism pathway of an endogenous nucleotide. Guvermectin had similar metabolites in three plants, but the biotransformation ability had a strong species dependence. In addition, all the metabolites exhibit neglectable toxicities (bioconcentration factor <2000 L/kg b.w., LC50,rat > 5000 mg/kg b.w.) by prediction. The study provided valuable evidence for the application of guvermectin and a better understanding of the biological behavior of nucleoside-like pesticides.

Bi Xie Fen Qing Yin decoction alleviates potassium oxonate and adenine induced-hyperuricemic nephropathy in mice by modulating gut microbiota and intestinal metabolites

This study aimed to evaluate the preventive effect of Bi Xie Fen Qing Yin (BXFQY) decoction on hyperuricemic nephropathy (HN). Using an HN mouse model induced by oral gavage of potassium oxonate and adenine, we found that BXFQY significantly reduced plasma uric acid levels and improved renal function. Further study shows that BXFQY suppressed the activation of the NLRP3 inflammasome and decreased the mRNA expressions of pro-inflammatory and fibrosis-associated factors in renal tissues of HN mice. Also, BXFQY prevented the damage to intestinal tissues of HN mice, indicative of suppressed colonic inflammation and increased gut barrier integrity. By 16 S rDNA sequencing, BXFQY significantly improved gut microbiota dysbiosis of HN mice. On the one hand, BXFQY down-regulated the abundance of some harmful bacteria, like Desulfovibrionaceae, Enterobacter, Helicobacter, and Desulfovibrio. On the other hand, BXFQY up-regulated the contents of several beneficial microbes, such as Ruminococcaceae, Clostridium sensu stricto 1, and Streptococcus. Using gas or liquid chromatography-mass spectrometry (GC/LC-MS) analysis, BXFQY reversed the changes in intestinal bacterial metabolites of HN mice, including indole and BAs. The depletion of intestinal flora from HN or HN plus BXFQY mice confirmed the significance of gut microbiota in BXFQY-initiated treatment of HN. In conclusion, BXFQY can alleviate renal inflammation and fibrosis of HN mice by modulating gut microbiota and intestinal metabolites. This study provides new insight into the underlying mechanism of BXFQY against HN.

Insights into the molecular mechanism of dextran sulfate inhibiting DNA digestion by pepsin: a crucial role of sulfate group on the binding to DNA

Sulfate polysaccharides can inhibit DNA digestion in simulated gastric juice in vitro, which is important for regulating dietary nucleic acids metabolism, but the mechanism of inhibition is unclear. This study used dextran sulfate (DS) with different sulfate groups and molecular weights to explore the effect of DS on DNA digestion. Molecular interactions between DS and DNA were investigated by biolayer interferometry (BLI), isothermal titration calorimetry (ITC) and molecular dynamics simulations. Results indicated that DS with higher molecular weight and sulfate group content showed stronger inhibitory effect of DNA digestion. ITC results showed that the combined Kd value of DNA and DS was about 2.53 mM. The main reason for inhibition of DNA digestion is that the formation of hydrogen bonds between the sulfate group of DS and DNA bases hinders the binding of DNA to pepsin. This finding will facilitate new strategies for nucleic acid metabolism and oral drug delivery.Communicated by Ramaswamy H. Sarma.

Mining Xanthine Oxidase Inhibitors from an Edible Seaweed Pterocladiella capillacea by Using In Vitro Bioassays, Affinity Ultrafiltration LC-MS/MS, Metabolomics Tools, and In Silico Prediction

The prevalence of gout and the adverse effects of current synthetic anti-gout drugs call for new natural and effective xanthine oxidase (XOD) inhibitors to target this disease. Based on our previous finding that an edible seaweed Pterocladiella capillacea extract inhibits XOD, XOD-inhibitory and anti-inflammatory activities were used to evaluate the anti-gout potential of different P. capillacea extract fractions. Through affinity ultrafiltration coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS), feature-based molecular networking (FBMN), and database mining of multiple natural products, the extract's bioactive components were traced and annotated. Through molecular docking and ADMET analysis, the possibility and drug-likeness of the annotated XOD inhibitors were predicted. The results showed that fractions F4, F6, F4-2, and F4-3 exhibited strong XOD inhibition activity, among which F4-3 reached an inhibition ratio of 77.96% ± 4.91% to XOD at a concentration of 0.14 mg/mL. In addition, the P. capillacea extract and fractions also displayed anti-inflammatory activity. Affinity ultrafiltration LC-MS/MS analysis and molecular networking showed that out of the 20 annotated compounds, 8 compounds have been previously directly or indirectly reported from seaweeds, and 4 compounds have been reported to exhibit anti-gout activity. Molecular docking and ADMET showed that six seaweed-derived compounds can dock with the XOD activity pocket and follow the Lipinski drug-like rule. These results support the value of further investigating P. capillacea as part of the development of anti-gout drugs or related functional foods.

Fucoidan from Saccharina japonica Alleviates Hyperuricemia-Induced Renal Fibrosis through Inhibiting the JAK2/STAT3 Signaling Pathway

Fucoidan is a native sulfated polysaccharide mainly isolated from brown seaweed, with diverse pharmacological activities, such as anti-inflammatory and antifibrosis. Hyperuricemia (HUA) is a common metabolic disease worldwide and mainly causes hyperuricemic nephropathy, including chronic kidney disease and end-stage renal fibrosis. The present study investigated the protective function of fucoidan in renal fibrosis and its pharmacological mechanism. The renal fibrotic model was established with the administration of potassium oxonate for 10 weeks. The protein levels of related factors were assessed in HUA mice by an enzyme-linked immunosorbent assay (ELISA) and western blotting. The results showed that fucoidan significantly reduced the levels of serum uric acid, blood urea nitrogen (BUN), α-smooth muscle actin (α-SMA), and collagen I, and improved kidney pathological changes. Furthermore, renal fibrosis had been remarkably elevated through the inhibition of the epithelial-to-mesenchymal transition (EMT) progression after fucoidan intervention, suppressing the Janus kinase 2 (JAK2) signal transducer and activator of transcription protein 3 (STAT3) signaling pathway activation. Together, this study provides experimental evidence that fucoidan may protect against hyperuricemia-induced renal fibrosis via downregulation of the JAK2/STAT3 signaling pathway.

Acanthopanax senticosus Harms improves Parkinson's disease by regulating gut microbial structure and metabolic disorders

Parkinson's disease (PD) is the second most common neurodegenerative disease, with an increasing prevalence as the population ages, posing a serious threat to human health, but the pathogenesis remains uncertain. Acanthopanax senticosus (Rupr. et Maxim.) Harms (ASH) (aqueous ethanol extract), a Chinese herbal medicine, provides obvious and noticeable therapeutic effects on PD. To further investigate the ASH's mechanism of action in treating PD, the structural and functional gut microbiota, as well as intestinal metabolite before and after ASH intervention in the PD mice model, were examined utilizing metagenomics and fecal metabolomics analysis. α-syn transgenic mice were randomly divided into a model and ASH groups, with C57BL/6 mice as a control. The ASH group was gavaged with ASH (45.5 mg/kg/d for 20d). The time of pole climbing and autonomous activity were used to assess motor ability. The gut microbiota's structure, composition, and function were evaluated using Illumina sequencing. Fecal metabolites were identified using UHPLC-MS/MS to construct intestinal metabolites. The findings of this experiment demonstrate that ASH may reduce the climbing time of PD model mice while increasing the number of autonomous movements. The results of metagenomics analysis revealed that ASH could up-regulated Firmicutes and down-regulated Actinobacteria at the phylum level, while Clostridium was up-regulated and Akkermansia was down-regulated at the genus level; it could also recall 49 species from the phylum Firmicutes, Actinobacteria, and Tenericutes. Simultaneously, metabolomics analysis revealed that alpha-Linolenic acid metabolism might be a key metabolic pathway for ASH to impact in PD. Furthermore, metagenomics function analysis and metabolic pathway enrichment analysis revealed that ASH might influence unsaturated fatty acid synthesis and purine metabolism pathways. These metabolic pathways are connected to ALA, Palmitic acid, Adenine, and 16 species of Firmicutes, Actinobacteria, and Tenericutes. Finally, these results indicate that ASH may alleviate the movement disorder of the PD model, which may be connected to the regulation of gut microbiota structure and function as well as the modulation of metabolic disorders by ASH.

Fucoidan alleviates the hepatorenal syndrome through inhibition organic solute transporter α/β to reduce bile acids reabsorption

The high levels of bile acids are a critical factor in hepatorenal syndrome. Organic solute transporter α/β (Ostα/β) participate in bile acids reabsorption in the kidney. Fucoidan has the great potential in protecting against liver and kidney injury. However, whether Ostα/β increase bile acids reabsorption in bile duct ligature (BDL)-induced hepatorenal syndrome and the blockade of fucoidan are still not clear. Male mice that received BDL were given to fucoidan (at 12.5, 25 and 50 ​mg/kg) through intraperitoneal injection once daily for three weeks. The serum, liver and kidney samples of these experimental mice were collected to carry out biochemical, pathological and Western blot analysis. In this study, fucoidan significantly lowered serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), decreased serum levels of uric acid, creatinine and uric nitrogen, restored the deregulation of the renal urate transporter 1 (URAT1), organic anion transporter 1 (OAT1), and organic cation/carnitine transporter 1/2 (OCTN1/2), consistence with alleviation BDL-induced liver and kidney dysfunction, inflammation and fibrosis in mice. Furthermore, fucoidan significantly hampered Ostα/β and reduced bile acids reabsorption in BDL-induced mice, protected against AML12 and HK-2 ​cells injury in vitro. These results demonstrate that fucoidan alleviates BDL-induced hepatorenal syndrome through inhibition Ostα/β to reduce bile acids reabsorption in mice. Therefore, suppression of Ostα/β by fucoidan may be a novel strategy for attenuating hepatorenal syndrome.

Anti-Hyperuricemic, Nephroprotective, and Gut Microbiota Regulative Effects of Separated Hydrolysate of α-Lactalbumin on Potassium Oxonate- and Hypoxanthine-Induced Hyperuricemic Mice

SCOPE

This study aims to investigate the anti-hyperuricemic and nephroprotective effects and the potential mechanisms of the separated gastrointestinal hydrolysates of α-lactalbumin on hyperuricemic mice.

METHODS AND RESULTS

The gastrointestinal hydrolysate of α-lactalbumin, the hydrolysate fraction with molecular weight (MW) < 3 kDa (LH-3k), and the fragments with smallest MW among LH-3K harvested through dextran gel chromatography (F5) are used. Hyperuricemia mice are induced via daily oral gavage of potassium oxonate and hypoxanthine. F5 displays the highest in vitro xanthine oxidase (XO) inhibition among all the fractions separated from LH-3k. Oral administration of F5 significantly reduces the levels of serum uric acid (UA), creatinine, and urea nitrogen. F5 treatment could ameliorate kidney injury through alleviating oxidative stress and inflammation. F5 alleviates hyperuricemia in mice by inhibiting hepatic XO activity and regulating the expression of renal urate transporters. Gut microbiota analysis illustrates that F5 administration increases the abundance of some SCFAs producers, and inhibits the growth of hyperuricemia and inflammation associated genera. LH-3k exhibits similar effects but does not show significance as those of the F5 fraction.

CONCLUSION

The anti-hyperuricemia and nephroprotective functions of F5 are mediated by inhibiting hepatic XO activity, ameliorating oxidative stress and inflammation, regulating renal urate transporters, and modulating the gut microbiota in hyperuricemic mice.

Metabolomic and transcriptomic exploration of the uric acid-reducing flavonoids biosynthetic pathways in the fruit of Actinidia arguta Sieb. Zucc

Flavonoids from Actinidia arguta Sieb. Zucc. can reduce uric acid in mice. However, the molecular basis of its biosynthesis is still unclear. In this paper, we used a combination of extensively targeted metabolomics and transcriptomics analysis to determine the types and differences of flavonoids in the fruit ripening period (August to September) of two main cultivated varieties in northern China. The ethanol extract was prepared, and the potential flavonoids of Chrysin (Flavone1), Rutin (Flavone2), and Daidzein (Flavone3) in Actinidia arguta Sieb. Zucc. were separated and purified by HPD600 macroporous adsorption resin and preparative liquid chromatography. The structure was identified by MS-HPLC, and the serum uric acid index of male Kunming mice was determined by an animal model test.125 flavonoids and 50 differentially regulated genes were identified. The contents of UA (uric acid), BUN (urea nitrogen), Cr (creatinine), and GAPDH in mouse serum and mouse liver glycogen decreased or increased in varying degrees. This paper reveals the biosynthetic pathway of uric acid-reducing flavonoids in the fruit of Actinidia arguta Sieb. Zucc., a major cultivar in northern China, provides valuable information for the development of food and drug homologous functional foods.

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.

Engineered Escherichia coli Nissle 1917 with urate oxidase and an oxygen-recycling system for hyperuricemia treatment

Hyperuricemia is the second most prevalent metabolic disease to human health after diabetes. Only a few clinical drugs are available, and most of them have serious side effects. The human body does not have urate oxidase, and uric acid is secreted via the kidney or the intestine. Reduction through kidney secretion is often the cause of hyperuricemia. We hypothesized that the intestine secretion could be enhanced when a recombinant urate-degrading bacterium was introduced into the gut. We engineered an Escherichia coli Nissle 1917 strain with a plasmid containing a gene cassette that encoded two proteins PucL and PucM for urate metabolism from Bacillus subtilis, the urate importer YgfU and catalase KatG from E. coli, and the bacterial hemoglobin Vhb from Vitreoscilla sp. The recombinant E. coli strain effectively degraded uric acid under hypoxic conditions. A new method to induce hyperuricemia in mice was developed by intravenously injecting uric acid. The engineered Escherichia coli strain significantly lowered the serum uric acid when introduced into the gut or directly injected into the blood vessel. The results support the use of urate-degrading bacteria in the gut to treat hyperuricemia. Direct injecting bacteria into blood vessels to treat metabolic diseases is proof of concept, and it has been tried to treat solid tumors.

The Emerging Evidence for a Protective Role of Fucoidan from Laminaria japonica in Chronic Kidney Disease-Triggered Cognitive Dysfunction

This study aimed to explore the mechanism of fucoidan in chronic kidney disease (CKD)-triggered cognitive dysfunction. The adenine-induced ICR strain CKD mice model was applied, and RNA-Seq was performed for differential gene analysis between aged-CKD and normal mice. As a result, fucoidan (100 and 200 mg kg-1) significantly reversed adenine-induced high expression of urea, uric acid in urine, and creatinine in serum, as well as the novel object recognition memory and spatial memory deficits. RNA sequencing analysis indicated that oxidative and inflammatory signaling were involved in adenine-induced kidney injury and cognitive dysfunction; furthermore, fucoidan inhibited oxidative stress via GSK3β-Nrf2-HO-1 signaling and ameliorated inflammatory response through regulation of microglia/macrophage polarization in the kidney and hippocampus of CKD mice. Additionally, we clarified six hallmarks in the hippocampus and four in the kidney, which were correlated with CKD-triggered cognitive dysfunction. This study provides a theoretical basis for the application of fucoidan in the treatment of CKD-triggered memory deficits.

Laminaria japonica fucoidan ameliorates cyclophosphamide-induced liver and kidney injury possibly by regulating Nrf2/HO-1 and TLR4/NF-κB signaling pathways

BACKGROUND

During clinical practice, cyclophosphamide (CTX) can lead to liver and kidney injury in vivo. In this study, we established a liver and kidney injury model by injecting CTX (80 mg kg-1  d-1 ) into male ICR mice, and then mice were treated with saline and fucoidan (20 or 40 mg kg-1 ), respectively. Subsequently, the liver and kidney toxicity indices, the expression levels of malonic dialdehyde (MDA), inflammatory factors, and the main protein levels of the Nrf2/HO-1 and TLR4/NF-κB pathways were determined.

RESULTS

Our results indicated that fucoidan could significantly decrease serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CRE), and urea (BUN) in the test group compared to the model group. Fucoidan administration caused reductions in MDA, interleukin-6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNF-α) levels and improved superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities in the liver and kidney of CTX-induced mice. Fucoidan up-regulated the Nrf2/HO-1 pathway and enhanced the protein levels of Nrf2, HO-1, GCLM, and NQO1. Moreover, fucoidan down-regulated the TLR4/NF-κB pathway, as indicated by decreased levels of TLR4, NF-κB p65, NF-κB p50, and increased IκBα level in liver and kidney tissues.

CONCLUSION

Our studies suggest that fucoidan can ameliorate CTX-induced liver and kidney injury, potentially via up-regulating the Nrf2/HO-1 pathway and inhibiting the TLR4/NF-κB pathway. © 2021 Society of Chemical Industry.

Purine-Induced IFN-γ Promotes Uric Acid Production by Upregulating Xanthine Oxidoreductase Expression

OBJECTIVE

Limiting purine intake, inhibiting xanthine oxidoreductase (XOR) and inhibiting urate reabsorption in proximal tubule by uricosuric drugs, to reduce serum uric acid (UA) levels, are recognized treatments for gout. However, the mechanism of increased how XOR expression and activity in hyperuricemia and gout remains unclear. This study aims to explore whether exogenous purines are responsible for increased XOR expression and activity.

METHODS

HepG2 and Bel-7402 human hepatoma cells were stimulated with exogenous purine, or were exposed to conditioned growth medium of purine-stimulated Jurkat cells, followed by measurement of XOR expression and UA production to determine the effect of lymphocyte-secreted cytokines on XOR expression in hepatocytes. The expression of STAT1, IRF1 and CBP and their binding on the XDH promoter were detected by western blotting and ChIP-qPCR. The level of DNA methylation was determined by bisulfite sequencing PCR. Blood samples from 117 hyperuricemia patients and 119 healthy individuals were collected to analyze the correlation between purine, UA and IFN-γ concentrations.

RESULTS

Excess of purine was metabolized to UA in hepatocyte metabolism by XOR that was induced by IFN-γ secreted in the conditioned growth medium of Jurkat cells in response to exogenous purine, but it did not directly induce XOR expression. IFN-γ upregulated XOR expression due to the enhanced binding of STAT1 to IRF1 to further recruit CBP to the XDH promoter. Clinical data showed positive correlation of serum IFN-γ with both purine and UA, and associated risk of hyperuricemia.

CONCLUSION

Purine not only acts as a metabolic substrate of XOR for UA production, but it induces inflammation through IFN-γ secretion that stimulates UA production through elevation of XOR expression.

Isorhamnetin, the xanthine oxidase inhibitor from Sophora japonica, ameliorates uric acid levels and renal function in hyperuricemic mice

Hyperuricemia is a metabolic condition closely linked to xanthine oxidase (XOD) function, which is involved in the production of uric acid (UA). In this study, XOD was used as a target to construct an in vitro and in vivo activity screening and verification system. The XOD inhibition ability of the main components from the water extract of Sophorae Flos (WSF), an unopened dry flower bud of Sophora japonica, was screened by HPLC. Isorhamnetin (IRh) was identified as a major flavonoid XOD inhibitor from WSF, and we characterized its effects and potential mechanism in ameliorating UA levels and renal function in hyperuricemia model mice. Hyperuricemia was induced by oral administration of potassium oxonate (PO) and hypoxanthine to mice for 7 days. The biochemical index results showed that treatments with low, medium, and high doses of IRh (50, 100, and 150 mg kg^-1) significantly reduced serum UA levels and inhibited XOD activity in serum and in the liver. Additionally, IRh effectively decreased the levels of serum creatinine and blood urea nitrogen, suggesting that it possessed nephroprotective effects in hyperuricemic mice. Furthermore, histopathological results showed that nuclear lesions and renal tubule dilatation in the kidneys of IRh-treated hyperuricemic mice were reduced, suggesting that IRh may alleviate renal injury. Molecular docking results showed that IRh combined well with XOD and is an effective XOD inhibitor. In conclusion, IRh from Sophora japonica may reduce the UA levels and alleviate renal injury by inhibiting XOD activity. It potentially functions as a therapeutic drug and dietary supplement to treat hyperuricemia.

Anti-Inflammatory Mechanisms of Fucoidans to Treat Inflammatory Diseases: A Review

Fucoidans are sulfated heteropolysaccharides found in the cell walls of brown seaweeds (Phaeophyceae) and in some marine invertebrates. Generally, fucoidans are composed of significant amounts of L-fucose and sulfate groups, and lesser amounts of arabinose, galactose, glucose, glucuronic acid, mannose, rhamnose, and xylose. In recent years, fucoidans isolated from brown seaweeds have gained considerable attention owing to their promising bioactive properties such as antioxidant, immunomodulatory, anti-inflammatory, antiobesity, antidiabetic, and anticancer properties. Inflammation is a complex immune response that protects the organs from infection and tissue injury. While controlled inflammatory responses are beneficial to the host, leading to the removal of immunostimulants from the host tissues and restoration of structural and physiological functions in the host tissues, chronic inflammatory responses are often associated with the pathogenesis of tumor development, arthritis, cardiovascular diseases, diabetes, obesity, and neurodegenerative diseases. In this review, the authors mainly discuss the studies since 2016 that have reported anti-inflammatory properties of fucoidans isolated from various brown seaweeds, and their potential as a novel functional material for the treatment of inflammatory diseases.

Sonneratia apetala seed oil attenuates potassium oxonate/hypoxanthine-induced hyperuricemia and renal injury in mice

Sonneratia apetala seeds are considered as prospective nutraceuticals with a high content of unsaturated fatty acids (UFAs) which are mainly distributed in the oil. It is well-known that UFAs could exhibit urate-lowering potency and protect against renal injury, indicating that S. apetala seed oil (SSO) may possess hypouricemic and nephroprotective effects. Consequently, the present work attempted to probe into the effects and mechanisms of SSO on potassium oxonate/hypoxanthine-induced hyperuricemia and associated renal injury. The results indicated that SSO treatment prominently inhibited the increase of serum uric acid (UA), creatinine (CRE), and urea nitrogen (BUN) levels and hepatic xanthine oxidase (XOD) activity in hyperuricemia mice. Kidney indexes and histopathological lesions were also remarkably ameliorated. Additionally, SSO treatment improved the renal anti-oxidant status in hyperuricemia mice by significantly reversing the increase in ROS and MDA levels as well as the decline in SOD, CAT and GSH-Px activities. SSO dramatically downregulated the expression and secretion of pro-inflammatory factors involving MCP-1, IL-1β, IL-6, IL-18 and TNF-α elicited by hyperuricemia. Furthermore, after SSO treatment, increased protein expressions of GLUT9, URAT1 and OAT1 in the hyperuricemia mice were obviously reversed. SSO treatment enormously restored Nrf2 activation and subsequent translation of related anti-oxidative enzymes in the kidneys. TXNIP/NLRP3 inflammasome activation was also obviously suppressed by SSO. In conclusion, SSO exerted favorable hypouricemic effects owing to its dual functions of downregulating the XOD activity and modulating the expressions of renal urate transport-associated proteins, and it also could alleviate hyperuricemia-induced renal injury by restoring the Keap1-Nrf2 pathway and blocking the TXNIP/NLRP3 inflammasome activation.

Antihyperuricemic Effect of Green Alga Ulva lactuca Ulvan through Regulating Urate Transporters

A novel polysaccharide from Ulva lactuca (ULP) was purified using a Sepharose CL-4B column. Fourier transform infrared spectroscopy, high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy were employed to analyze the structure of ULP. It consisted of rhamnose (Rha), glucuronic acid (GluA), galactose (Gal), and xylose (Xyl) at a molar ratio of 32.75:22.83:1.07:6.46 with the molecular weight of 2.24 × 10⁵ Da. The four major glycosidic residues found in ULP were →2,3)-α-l-Rhap-(1→, →4)-β-d-GlcpA-(1→, →2,6)-β-d-Galp-(1→, and →4)-β-d-Xylp-(1→. The antihyperuricemic activity of ULP was exhibited by detecting related biochemical indexes, urate transporter gene expressions, renal histopathology, and intestinal microbiota shifts. ULP obviously decreased the levels of serum uric acid (UA), blood urea nitrogen, and creatinine, while inhibited serum and hepatic xanthine oxidase activities as well as improved renal injury in hyperuricemic mice. Furthermore, the upregulation of UA excretion genes ABCG2/OAT1 and downregulation of UA resorption genes URAT1 and GLUT9 were detected. In addition, ULP exerted its antihyperuricemic effect through regulating the intestinal microbiome, characterized by elevating the helpful microbial abundance, meanwhile declining the harmful bacterial abundance and restoring the gut microbiome homeostasis. This study demonstrates the antihyperuricemic activity of ULP and its potential effect for the treatment of hyperuricemia-related diseases.

Type 2 diabetic mice enter a state of spontaneous hibernation-like suspended animation following accumulation of uric acid

Hibernation is an example of extreme hypometabolic behavior. How mammals achieve such a state of suspended animation remains unclear. Here we show that several strains of type 2 diabetic mice spontaneously enter into hibernation-like suspended animation (HLSA) in cold temperatures. Nondiabetic mice injected with ATP mimic the severe hypothermia analogous to that observed in diabetic mice. We identified that uric acid, an ATP metabolite, is a key molecular in the entry of HLSA. Uric acid binds to the Na⁺ binding pocket of the Na⁺/H⁺ exchanger protein and inhibits its activity, acidifying the cytoplasm and triggering a drop in metabolic rate. The suppression of uric acid biosynthesis blocks the occurrence of HLSA, and hyperuricemic mice induced by treatment with an uricase inhibitor can spontaneously enter into HLSA similar to that observed in type 2 diabetic mice. In rats and dogs, injection of ATP induces a reversible state of HLSA similar to that seen in mice. However, ATP injection fails to induce HLSA in pigs due to the lack of their ability to accumulate uric acid. Our results raise the possibility that nonhibernating mammals could spontaneously undergo HLSA upon accumulation of ATP metabolite, uric acid.

A brief review of urate transporter 1 (URAT1) inhibitors for the treatment of hyperuricemia and gout: Current therapeutic options and potential applications

Hyperuricemia is a common metabolic condition, cause by increased levels of serum urate (SUA). Reduced excretion of uric acid is reported as the key factor of primary hyperuricemia, accounting for approximately 90% of the cases. Urate transporter 1 (URAT1) is a major protein involved in uric acid reabsorption (about 90%). Therefore, URAT1 inhibitors are considered to be a highly effective and promising class of uricosuric agents for treating hyperuricemia. This review summarizes the development of URAT1 inhibitors for the treatment of hyperuricemia, including approved URAT1 inhibitors, URAT1 inhibitors under development in clinical trials, substances with URAT1 inhibitory effects from derivatives and natural products, and conventional drugs with new uses. This review provides new ideas regarding research on URAT1 inhibitors by introducing the structure, properties, and side effects of chemical drugs, as well as the sources and categories of natural drugs. We also discuss new mechanisms of classic drugs, which may provide guidance to many practicing clinicians. The research and discovery of new inhibitors remain in full swing, and tremendous developments are expected in the field.

Effects of Macroporous Resin Extract of Dendrobium officinale Leaves in Rats with Hyperuricemia Induced by Fructose and Potassium Oxonate

AIM AND OBJECTIVE

Fructose, as a ubiquitous monosaccharide, can promote ATP consumption and elevate circulating uric acid (UA) levels. Our previous studies confirmed that the macroporous resin extract of Dendrobium officinale leaves (DoMRE) could reduce the UA level of rats with hyperuricemia induced by a high-purine diet. This study aimed to investigate whether DoMRE had a UA-lowering effect on rats with hyperuricemia caused by fructose combined with potassium oxonate, so as to further clarify the UA-lowering effect of DoMRE, and to explore the UA-lowering effect of DoMRE on both UA production and excretion.

MATERIALS AND METHODS

Rats with hyperuricemia induced by fructose and potassium oxonate were administered with DoMRE and vehicle control, respectively, to compare the effects of the drugs. At the end of the experiment, the serum uric acid (SUA) and creatinine (Cr) levels were measured using an automatic biochemical analyzer, the activities of xanthine oxidase (XOD) were measured using an assay kit, and the protein expression of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), and ATP-binding cassette superfamily G member 2 (ABCG2) were assessed using immunohistochemical and western blot analyses. Hematoxylin and eosin staining was used to assess the histological changes in the kidney, liver, and intestine.

RESULTS

Rats with hyperuricemia were induced by fructose and potassiumFructose and potassium induced hyperuricemia in rats. Meanwhile, the activities of XOD were markedly augmented, the expression of URAT1 and GLUT9 was promoted, and the expression of ABCG2 was reduced, which were conducive to the elevation of UA. However, exposure to DoMRE reversed these fructose- and potassium oxonate-induced negative alternations in rats. The activities of XOD were recovered to the normal level, reducing UA formation; the expression of URAT1, ABCG2, and GLUT9 returned to the normal level, resulting in an increase in renal urate excretion.

CONCLUSION

DoMRE reduces UA levels in rats with hyperuricemia induced by fructose combined with potassium oxonate by inhibiting XOD activity and regulating the expression of ABCG2, URAT1, and GLUT9. DoMRE is a potential therapeutic agent for treating hyperuricemia through inhibiting UA formation and promoting UA excretion.

Fucoidan from Laminaria japonica Inhibits Expression of GLUT9 and URAT1 via PI3K/Akt, JNK and NF-κB Pathways in Uric Acid-Exposed HK-2 Cells

This work aimed to investigate the effect of fucoidan (FPS) on urate transporters induced by uric acid (UA). The results showed that UA stimulated the expression of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) in HK-2 cells, and FPS could reverse the effect. Moreover, UA could activate NF-κB, JNK and PI3K/Akt pathways, but both pathway inhibitors and FPS inhibited the UA-induced activation of these three pathways. These data suggested that FPS effectively inhibited the expression induction of reabsorption transporters URAT1 and GLUT9 by UA, through repressing the activation of NF-κB, JNK and PI3K/Akt signal pathways in HK-2 cells. The in vitro research findings support the in vivo results that FPS reduces serum uric acid content in hyperuricemia mice and rats through inhibiting the expression of URAT1 and GLUT9 in renal tubular epithelial cells. This study provides a theoretical basis for the application of FPS in the treatment of hyperuricemia.

Preventive Effects of Three Polysaccharides on the Oxidative Stress Induced by Acrylamide in a Saccharomyces cerevisiae Model

Saccharomyces cerevisiae was used as a model to explore the preventive effect of two marine polysaccharides separately derived from Sepia esculenta ink (SIP) and Laminaria japonica (FL) as well as one terrestrial polysaccharides from Eleocharis tuberosa peel (WCPP) on toxic injury induced by acrylamide (AA). The growth of yeast was evaluated by kinetics indexes including doubling time, lag phase and maximum proliferation density. Meanwhile, intracellular redox state was determined by contents of MDA and GSH, and SOD activity. The results showed that AA inhibited yeast growth and destroyed the antioxidant defense system. Supplement with polysaccharides, the oxidative damage of cells was alleviated. According to the growth recovery of yeast, FL and WCPP had similar degree of capacity against AA associated cytotoxicity, while SIP was 1.5~2 folds as strong as FL and WCPP. SIP and FL significantly reduced production of MDA by AA administration. Moreover, SIP, FL and WCPP increased SOD activity and repressed GSH depletion caused by AA.

Comparisons of protective effects between two sea cucumber hydrolysates against diet induced hyperuricemia and renal inflammation in mice

Differences in the anti-hyperuricemic and anti-inflammation effects between two sea cucumber hydrolysates in diet induced hyperuricemic mice.

Renoprotective Effect of Laminaria japonica Polysaccharide in Adenine-Induced Chronic Renal Failure

Chronic renal failure (CRF) is a major public health problem worldwide. In this work, we investigated the effects of a purified Laminaria japonica polysaccharide (LJP61A) on renal function using an adenine-induced CRF mice model. Results exhibited that adenine treatment caused serious renal pathological damages and elevation of serum creatinine and blood urea nitrogen of mice. However, these changes could be significantly reversed by the administration of LJP61A in a dose-dependent manner. Additionally, LJP61A could dramatically reduce weight loss, improve the urine biochemical index, and regulate the electrolyte disturbance of CRF mice. These results suggest that the renal function of adenine-induced CRF mice can be improved by LJP61A, which might be developed into a potential therapeutic agent for CRF patients.