Recent advances on uric acid transporters

Elevating uric acid as an antimalarial target

Malaria causes hundreds of thousands of deaths each year in children, and many survivors are left with lasting neurological injury. While we have effective parasite-killing drugs, we need treatments that target disease mechanisms to improve outcomes. Bond et al. recently reported uric acid as a potential target for anti-disease therapy.

Ligusticum cycloprolactam ameliorates hyperuricemic nephropathy through inhibition of TLR4/NF-κB signaling

Hyperuricemia is a metabolic disease attributed to a sustained dysregulation of purine metabolism, manifesting as consistently elevated blood uric acid levels. Hyperuricemic nephropathy (HN) is a renal complication of hyperuricemia. It is characterized by the deposition of urate crystals, inflammatory cell infiltration and tubulointerstitial injury. Ligusticum cycloprolactam (LIGc) is a novel monomeric derivative of the active ingredient ligustilide (LIG) from Angelica sinensis (Oliv.). LIG demonstrates anti-inflammatory and antioxidant properties. Nevertheless, the therapeutic potential of LIGc to ameliorate HN required further investigation. Our study revealed that LIGc effectively reduced serum uric acid and attenuated HN in mice induced by co-administering potassium oxonate and hypoxanthine. Our research demonstrated that LIGc treatment improved renal function in mice with HN by regulating the expression of uric acid transporters. Histopathological analysis showed that LIGc treatment reduced tubular damage, inflammatory infiltration and interstitial collagen deposition. Mechanistically, LIGc alleviated renal injury by inhibiting the TLR4/NF-κB signaling pathway both in vivo and in vitro. Our study revealed that LIGc effectively mitigated HN by attenuating the inflammatory response through the TLR4/NF-κB signaling pathway, providing new perspectives for the treatment of HN.

The Association Between the Triglyceride Glucose Index and Hyperuricemia: A Dose-Response Meta-Analysis

Background: The triglyceride glucose (TyG) index has been correlated with all kinds of diseases. However, its association with hyperuricemia is still a subject of controversy. Methods: This meta-analysis encompassed relevant studies on the TyG index and hyperuricemia obtained from electronic databases, from the launch date until March 2025. The effect sizes and corresponding 95% confidence intervals (CIs) were obtained using a random effects model. Results: Twenty-six trials with 637,954 subjects were incorporated in this study. It was revealed that the TyG index was linked to hyperuricemia (OR = 2.67; 95% CI: 2.34, 3.04; p < 0.001). A dose-response analysis demonstrated that with each 1 mg/dL rise in the TyG index, the risk of being diagnosed with hyperuricemia increased by 2.07 times (OR = 2.07; 95% CI: 1.89, 2.25; p < 0.001). Conclusions: The TyG index has an association with hyperuricemia. Given the constraints identified in our meta-analysis, further cohort studies will be essential to confirm this correlation.

Flavonoid-rich extract of Paederia scandens (Lour.) Merrill improves hyperuricemia by regulating uric acid metabolism and gut microbiota

Paederia scandens (Lour.) Merrill flavonoid-rich extract (PSMF) has shown excellent xanthine oxidase (XOD) inhibitory activity in our previous study. However, the efficacy of PSMF in mitigating hyperuricemia (HUA) remains to be elucidated. In this study, we investigated the effects and mechanisms of PSMF on alleviating in HUA mice. The results showed that PSMF intervention reduced serum levels of uric acid (UA), creatinine (CRE), and blood urea nitrogen (BUN), and inhibited the activities of XOD and adenosine deaminase (ADA). In addition, PSMF treatment not only attenuated the inflammatory response and renal damage but also regulated the expression of UA synthesis genes and UA excretion genes. Finally, PSMF ameliorated gut microbiota dysbiosis in HUA mice by enriching the abundance of short-chain fatty acid (SCFA)-producing bacteria. In summary, PSMF appears to be a promising natural source for the prevention and treatment of HUA.

Uric Acid-Degrading Lacticaseibacillus paracasei CPU202306 Ameliorates Hyperuricemia by Regulating Uric Acid Metabolism and Intestinal Microecology in Mice

Hyperuricemia, characterized by elevated levels of uric acid in the blood, poses a significant health threat due to its association with various adverse health outcomes, and lactic acid bacteria from the gut microbiota may offer solutions. Our investigation focused on Lacticaseibacillus paracasei CPU202306, isolated from fermented pickles for its potent uric acid degradation and probiotic properties. This bacterium effectively reduced blood uric acid levels by breaking down uric acid and inhibiting hepatic xanthine oxidase (XOD) and adenosine deaminase (ADA) enzymes. Additionally, it stimulated the production of short-chain fatty acid (SCFAs) in the colon, enhancing the expression of uric acid secretion transport proteins (ATP-binding cassette sub-family G member 2 and organic anion transporter 3) while suppressing absorption transport proteins (glucose transporter 9 and uric acid transporter 1). This orchestrated process promoted uric acid excretion. L. paracasei CPU202306 also improved gut microbiota health by reinforcing tight junction proteins, shifting the microbiota to a healthier composition, and reducing harmful bacteria. This transformation inhibited kidney TLR4/MyD88/NF-κB inflammatory signaling, leading to a significant decrease in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines, mitigating kidney inflammation. Furthermore, the bacterium supported kidney health by influencing amino acid metabolic pathways linked to the gut-kidney axis. In summary, our study highlights the diverse mechanisms through which L. paracasei CPU202306 addresses hyperuricemia, showcasing its therapeutic potential for this condition.

Desmodium caudatum (Thunb.) DC. extract attenuates hyperuricemia-induced renal fibrosis via modulating TGF-β1 pathway and uric acid transporters: Evidence from in vitro and in vivo studies

ETHNOPHARMACOLOGICAL RELEVANCE

Desmodium caudatum (Thunb.) DC., a traditional Chinese medicinal herb, has been used to treat conditions such as rheumatic back pain, diarrhea, jaundice-related hepatitis, and abscesses; it also serves as an anthelmintic. The extract of Desmodium caudatum (Thunb.) DC. (DCE) is also known for its antioxidant and anti-inflammatory properties. However, its impact on kidney fibrosis remains unclear.

AIM OF THE STUDY

This study investigated whether DCE can alleviate hyperuricemia-induced kidney fibrosis by modulating the transforming growth factor-β1 (TGF-β1) pathway, activating epithelial-mesenchymal transition (EMT), and regulating uric acid transporters.

MATERIALS AND METHODS

NRK52E cells were exposed to uric acid (UA) followed by DCE and isovitexin (IV) for 24 h. Cell damage was assessed using an Oxidative Stress Kit, ELISA, Gelatin Zymography, and Western blotting. In parallel, adenine-induced C57BL/6 mice received DCE and IV treatment for 11 weeks. After sacrifice, renal injury was assessed through histopathological examination and protein expression analysis of fibrosis markers, EMT indicators, and uric acid transporters.

RESULTS

DCE reduced reactive oxygen species (ROS) accumulation in uric acid-induced NRK52E cells and inhibited EMT by suppressing TGF-β1 and Slug while restoring E-cadherin expression. DCE treatment reduced fibrosis-related proteins (CTGF, collagen I, fibronectin, and α-SMA) in UA-treated cells and modulated uric acid transporters by increasing ABCG2 and OAT3 while decreasing URAT1 and GLUT9. In adenine-induced hyperuricemic C57BL/6 mice, DCE administration reduced serum uric acid levels and xanthine oxidase activity. Histological analysis showed that DCE attenuated renal fibrosis through decreased glomerular atrophy, reduced collagen deposition, and diminished α-SMA and fibronectin expression.

CONCLUSION

Our study demonstrates that DCE exerts protective benefits against hyperuricemia-induced renal fibrosis. The potential mechanism may involve suppressing the TGF-β1 signaling pathway and regulating the uric acid transporter, thereby mitigating kidney injury.

Isorhamnetin ameliorates hyperuricemia by regulating uric acid metabolism and alleviates renal inflammation through the PI3K/AKT/NF-κB signaling pathway

Hyperuricemia is a chronic metabolic disease with high incidence, and it has become a severe health risk in modern times. Isorhamnetin is a natural flavonoid found in a variety of plants, especially fruits such as buckthorn. The in vivo hyperuricemia ameliorating effect of isorhamnetin and the specific molecular mechanism were profoundly investigated using a hyperuricemia mouse model in this study. Results indicated that isorhamnetin showed a significant uric acid-lowering effect in mice. Isorhamnetin was able to reduce uric acid production by inhibiting XOD activity. Furthermore, it reduced the expression of GLUT9 to inhibit uric acid reabsorption and enhanced the expression of ABCG2, OAT1, and OAT3 to promote uric acid excretion. Metabolomics analysis revealed that gavage administration of isorhamnetin restored purine metabolism and riboflavin metabolism disorders and thus significantly alleviated hyperuricemia in mice. Furthermore, the alleviating effect of isorhamnetin on hyperuricemia-induced renal inflammation and its specific mechanism were explored through network pharmacology and molecular validation experiments. Network pharmacology predicted that seven targets were enriched in the PI3K/AKT pathway (CDK6, SYK, KDR, RELA, PIK3CG, IGF1R, and MCL1) and four targets were enriched in the NF-κB pathway (SYK, PARP1, PTGS2, and RELA). Western blot analysis validated that isorhamnetin inhibited the phosphorylation of PI3K and AKT and down-regulated the expression of NF-κB p65. It indicated that isorhamnetin could inhibit the PI3K/AKT/NF-κB signaling pathway to reduce the levels of renal inflammatory factors (TNF-α, IL-β and IL-6) and ultimately ameliorate hyperuricemia-induced renal inflammation in mice. This study provides a comprehensive and strong theoretical basis for the application of isorhamnetin in the field of functional foods or dietary supplements to improve hyperuricemia.

Benzbromarone Analog SAR: Potent hURAT1 (SLC22A12) Inhibitors and Drug Transporter Interaction Studies

Purpose

There were two main purposes for this study. One, to report two benzbromarone analogs and test their in vitro activity in the URAT1 inhibition assay; and two, to probe the structure-activity relationship (SAR) of various benzbromarone analogs regarding other drug transporters that may play a role in the uric acid uptake/elimination interplay.

Methods

In brief, chemical synthesis of two benzbromarone analogs was prepared using methods analogous to those reported. Furthermore, drug transporter protein inhibition was investigated in vitro using oocytes expressing hURAT1, hURATv1 (GLUT9), hOAT1, hOAT3, hOAT10, hNPT4, OATP1B1, OATP1B3 and OATP2B1 prepared and utilized to conduct inhibition studies. In addition, one novel benzbromarone analog was studied via in vivo rat pharmacokinetic experiments to determine apparent oral bioavailability.

Results

Two analogs, 6-fluoro-benzbromarone (5) and 5,6-difluoro-benzbromarone (9), were synthetically prepared and 5 had a hURAT1 IC50 inhibition of 18 ± 4 nM, while analog (9) had an IC50 of 245 ± 64 nM. Analog (5) had good oral bioavailability (Fa) >0.6 in rat. Eadie-Hofstee plot and double-reciprocal plot of the Michaelis-Menten equation are summarized for benzbromarone (2) and its major Phase I metabolite 6-hydroxy-benzbromarone (3).

Conclusion

These results illustrate that the Km for [14C]UA uptake was not altered in the presence of 2 or 3, but rather the Vmax was reduced in the presence of inhibitors when added to the uptake solutions. As a result, these data support the notion that 2 and 3 inhibit [14C]UA uptake by non-competitive inhibition and not at the URAT1 binding site.

Contribution and expression of renal drug transporters in renal cell carcinoma

Renal cell carcinoma (RCC) is a common substantive tumor. According to incomplete statistics, RCC incidence accounts for approximately 90% of renal malignant tumors, and is the second most prevalent major malignant tumor in the genitourinary system, following bladder cancer. Only 10%-15% of chemotherapy regimens for metastatic renal cell carcinoma (mRCC) are effective, and mRCC has a high mortality. Drug transporters are proteins located on the cell membrane that are responsible for the absorption, distribution, and excretion of drugs. Lots of drug transporters are expressed in the kidneys. Changes in carrier function weaken balance, cause disease, or modify the effectiveness of drug treatment. The changes in expression of these transporters during cancer pathology results in multi-drug resistance to cancer chemotherapy. In the treatment of RCC, the study of drug transporters helps to optimize treatment regimens, improve therapeutic effects, and reduce drug side effects. In this review, we summarize advances in the role of renal drug transporters in the genesis, progression, and treatment of RCC.

The potential role of uric acid in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder among women of reproductive age and is associated with a variety of multi-system complications. The prevailing treatment strategy for PCOS is to individualize the interventions based on individual symptoms and patient complaints. However, optimal efficacy in treatment necessitates a focus on addressing the underlying pathogenic mechanisms. Uric acid (UA), the end product of purine metabolism, has been suggested to be involved in the development of several diseases, including PCOS. However, the precise mechanisms by which UA may affect PCOS remain incompletely understood. This literature review aims to investigate the correlation between UA and the various clinical presentations of PCOS, such as hyperandrogenism, insulin resistance (IR), ovulation disorders, obesity, and other related manifestations, through the analysis of epidemiological and clinical studies. The purpose of this study is to improve our comprehension of how UA contributes to each aspect of PCOS and their interrelationship, thus identifying the potential role of UA as a facilitator of PCOS. Furthermore, we explore potential pathways linking UA and PCOS, and propose therapeutic interventions based on these findings to optimize the management of this condition.

Integrated microbiome and metabolome analysis reveals the key role of taurohyocholate in the treatment of hyperuricemia with Lacticaseibacillus rhamnosus 2016SWU.05.0601

The incidence of hyperuricemia (HUA) is on the rise, posing a significant threat to human health. Several probiotics have shown potential in treating HUA; however, the critical role of intestinal metabolites in this therapy remains inadequately understood. Our study demonstrated that Lacticaseibacillus rhamnosus 2016SWU.05.0601 not only reduced the expression levels of xanthine dehydrogenase and the content and activity of xanthine oxidase in the liver but also regulated the uric acid transporters expression in the kidney, thereby attenuating HUA in mice. Additionally, L. rhamnosus 2016SWU.05.0601 modulated the gut microbiota and metabolite abundance in HUA mice. Correlation analysis revealed that the gut microbiota metabolite taurohyocholate played a vital role in the treatment of HUA by L. rhamnosus 2016SWU.05.0601, as confirmed in HUA cell models. Our research provides a significant theoretical basis for elucidating the mechanisms by which probiotics alleviate HUA and for developing functional ingredients for HUA treatment.

Characterization of Human Organic Anion Transporter 4 (hOAT4) and Mouse Oat5 (mOat5) As Functional Orthologs for Renal Anion Uptake and Efflux Transport

Organic anions (OAs) are compounds including drugs or toxicants that are negatively charged at physiologic pH and are typically transported by organic anion transporters (OATs). Human OAT4 (SLC22A11) is expressed in the apical membrane of renal proximal tubules. Although there is no rodent ortholog of hOAT4, rodents express Oat5 (Slc22a19), an anion exchanger that is also localized to the apical membrane of renal proximal tubule cells. The purpose of this study was to determine the functional similarity between mouse Oat5 and human OAT4. Chinese hamster ovary (CHO) cells expressing SLC22A11 or Slc22a19 were used to assess the transport characteristics of radiolabeled ochratoxin (OTA). We determined the kinetics of OTA transport; the resulting Michaelis constant (Kt) and maximal rate of mediated substrate transport (Jmax) values were very similar for both hOAT4 and mOat5: Kt 3.9 and 7.2 μM, respectively, and Jmax 4.4 and 3.9 pmol/cm2, respectively. For the profile of OTA inhibition by OAs, IC50 values were determined for several clinically important drugs and toxicants. The resulting IC50 values ranged from 9 μM for indomethacin to ∼600 μM for the diuretic hydrochlorothiazide. We measured the efflux of OTA from preloaded cells; both hOAT4 and mOat5 supported the efflux of OTA. These data support the hypothesis that OAT4 and Oat5 are functional orthologs and share selectivity for OTA both for reabsorption and secretion. SIGNIFICANCE STATEMENT: This study compares the selectivity profile between human organic anion transporter (OAT4) and mouse Oat5. Our data revealed a similar selectivity profile for ochratoxin A (OTA) reabsorption and secretion by these two transporters, thereby supporting the hypothesis that hOAT4 and mOat5, although not genetic orthologs, behave as functional orthologs for both uptake and efflux. These data will be instrumental in selecting an appropriate animal model when studying the renal disposition of anionic drugs and toxicants.

Interplay between the Redox System and Renal Tubular Transport

The kidney plays a critical role in maintaining the homeostasis of body fluid by filtration of metabolic wastes and reabsorption of nutrients. Due to the overload, a vast of energy is required through aerobic metabolism, which inevitably leads to the generation of reactive oxygen species (ROS) in the kidney. Under unstressed conditions, ROS are counteracted by antioxidant systems and maintained at low levels, which are involved in signal transduction and physiological processes. Accumulating evidence indicates that the reduction-oxidation (redox) system interacts with renal tubular transport. Redox imbalance or dysfunction of tubular transport leads to renal disease. Here, we discuss the ROS and antioxidant systems in the kidney and outline the metabolic dysfunction that is a common feature of renal disease. Importantly, we describe the key molecules involved in renal tubular transport and their relationship to the redox system and, finally, summarize the impact of their dysregulation on the pathogenesis and progression of acute and chronic kidney disease.

Molecular basis of the urate transporter URAT1 inhibition by gout drugs

Hyperuricemia is a condition when uric acid, a waste product of purine metabolism, accumulates in the blood1. Untreated hyperuricemia can lead to crystal formation of monosodium urate in the joints, causing a painful inflammatory disease known as gout. These conditions are associated with many other diseases and affect a significant and increasing proportion of the population2-4. The human urate transporter 1 (URAT1) is responsible for the reabsorption of ~90% of uric acid in the kidneys back into the blood, making it a primary target for treating hyperuricemia and gout5. Despite decades of research and development, clinically available URAT1 inhibitors have limitations because the molecular basis of URAT1 inhibition by gout drugs remains unknown5. Here we present cryo-electron microscopy structures of URAT1 alone and in complex with three clinically relevant inhibitors: benzbromarone, lesinurad, and the novel compound TD-3. Together with functional experiments and molecular dynamics simulations, we reveal that these inhibitors bind selectively to URAT1 in inward-open states. Furthermore, we discover differences in the inhibitor dependent URAT1 conformations as well as interaction networks, which contribute to drug specificity. Our findings illuminate a general theme for URAT1 inhibition, paving the way for the design of next-generation URAT1 inhibitors in the treatment of gout and hyperuricemia.

Food-derived bioactive peptides with anti-hyperuricemic activity: A comprehensive review

Hyperuricemia (HU) is a metabolic disorder caused by the overproduction or underexcretion of uric acid (UA) in the human body. Several approved drugs for the treatment of HU are available in the market; however, all these allopathic drugs exhibit multiple side effects. Therefore, the development of safe and effective anti-HU drugs is an urgent need. Natural compounds derived from foods and plants have the potential to decrease UA levels. Recently, food-derived bioactive peptides (FBPs) have gained attention as a functional ingredient owing to their biological activities. In the current review, we aim to explore the urate-lowering potential and the underlying mechanisms of FBPs. We found that FBPs mitigate HU by reducing blood UA levels through inhibiting key enzymes such as xanthine oxidase, increasing renal UA excretion, inhibiting renal UA reabsorption, increasing anti-oxidant activities, regulating inflammatory mediators, and addressing gut microbiota dysbiosis. In conclusion, FBPs exhibit strong potential to ameliorate HU.

Relationship between uric acid to high-density cholesterol ratio (UHR) and circulating α-klotho: evidence from NHANES 2007-2016

OBJECTIVE

To investigate the relationship between uric acid to high-density lipoprotein cholesterol ratio (UHR) and circulating α-klotho levels in U.S. adults.

METHODS

A cross-sectional study used data from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Circulating α-klotho was defined as the dependent variable and UHR was defined as the independent variable. Multivariable linear regression was performed to assess the relationship between the independent and dependent variables. The nonlinear relationship and effect size between UHR and α-klotho were evaluated using smooth curve fitting and threshold effect analysis. Subgroup analysis and sensitivity analysis were conducted to determine the stability of the results. The diagnostic performance of UHR and α-klotho in common elderly diseases was compared using ROC (Receiver Operating Characteristic) analysis.

RESULTS

Among 12,849 participants, there was a negative relationship between the UHR and circulating α-klotho. In the fully adjusted overall model, each unit increase in UHR was associated with a decrease of 4.1 pg/mL in α-klotho. The threshold effect analysis showed that before the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 15.0 pg/mL in α-klotho; beyond the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 2.8 pg/mL in α-klotho. Subgroup analyses and sensitivity analysis indicated that the relationship between UHR and α-klotho remained stable across most populations. The ROC diagnostic test indicated that the evaluative efficacy of UHR in diagnosing age-related diseases was comparable to that of α-klotho.

CONCLUSION

This study revealed that the UHR was associated with the circulating α-klotho concentration, with a negative association observed in most cases. This finding suggested that the UHR might be a promising indicator for evaluating circulating α-klotho levels.

Identification of Hyperuricemia Alleviating Peptides from Yellow Tuna Thunnus albacares

The development of food-derived antihyperuricemic substances is important for alleviating hyperuricemia (HUA) and associated inflammation. Here, novel peptides fromThunnus albacares (TAP) with strong antihyperuricemic activity were prepared. TAP was prepared by alkaline protease (molecular weight <1000 Da), with an IC50 value of xanthine oxidase inhibitory activity of 2.498 mg/mL, and 5 mg/mL TAP could reduce uric acid (UA) by 33.62% in human kidney-2 (HK-2) cells (P < 0.01). Mice were fed a high-purine diet and injected with potassium oxonate to induce HUA. Oral administration of TAP (600 mg/kg/d) reduced serum UA significantly by 42.22% and increased urine UA by 79.02% (P < 0.01) via regulating urate transporters GLUT9, organic anion transporter 1, and ATP-binding cassette subfamily G2. Meantime, TAP exhibited hepatoprotective and nephroprotective effects, according to histological analysis. Besides, HUA mice treated with TAP showed anti-inflammatory activity by decreasing the levels of toll-like receptor 4, nuclear factors-κB p65, NLRP3, ASC, and Caspase-1 in the kidneys (P < 0.01). According to serum non-targeted metabolomics, 91 differential metabolites between the MC and TAP groups were identified, and purine metabolism was considered to be the main pathway for TAP alleviating HUA. In a word, TAP exhibited strong antihyperuricemic activity both in vitro and in vivo.

Retinol dehydrogenase 12 (RDH12) knock out may cause hyperuricemia phenotype in mice

Hyperuricemia is a chronic metabolic disease caused by purine metabolism disorder. And several gene loci and transporter proteins that associated with uric acid transport functions have been identified. Retinol Dehydrogenase 12 (RDH12), recognized for its role in safeguarding photoreceptors, and our study investigated the potential impact of Rdh12 mutations on other organs and diseases, particularly hyperuricemia. We assessed Rdh12 mRNA expression levels in various tissues and conducted serum biochemical analyses in Rdh12-/- mice. Compared with the wild type, significant alterations in serum uric acid levels and kidney-related biochemical indicators have been revealed. Then further analysis, including quantitative RT-PCR of gene expression in the liver and kidney, highlighted variations in the expression levels of specific genes linked to hyperuricemia. And renal histology assessment exposed mild pathological lesions in the kidneys of Rdh12-/- mice. In summary, our study suggests that Rdh12 mutations impact not only retinal function but also contribute to hyperuricemia and renal disease phenotypes in mice. Our finding implies that individuals with Rdh12 mutations may be prone to hyperuricemia and gout, emphasizing the significance of preventive measures and regular examinations in daily life.

Overcoming Biological Barriers: Importance of Membrane Transporters in Homeostasis, Disease, and Disease Treatment 2.0

This editorial summarizes the seven scientific papers published in the Special Issue "Overcoming Biological Barriers: Importance of Membrane Transporters in Homeostasis, Disease, and Disease Treatment 2 [...].

Effects of stocking density on the homeostasis of uric acid and related liver and kidney functions in ducks

OBJECTIVE

Stocking density (SD) is an important issue in the poultry industry, which is related to the production performance, intestinal health and immune status. In the present study, the effects of SD on the metabolism and homeostasis of uric acid as well as the related functions of the liver and kidney in ducks were examined.

METHODS

A total of 360 healthy 56-day-old Shan-ma ducks were randomly divided into the low stocking density (n = 60, density = 5 birds/m2), medium stocking density (n = 120, density = 10 birds/m2) and high stocking density groups (HSD; n = 180, density = 15 birds/m2). Samples were collected in the 3rd, 6th, and 9th weeks of the experiment for analysis.

RESULTS

The serum levels of uric acid, lipopolysaccharide and inflammatory cytokines (interleukin-1β [IL-1β], IL-8, and tumor necrosis factor-α [TNF-α]) were increased significantly in the HSD group. Serious histopathological lesions could be seen in both the livers and kidneys in the HSD group in the 9th week. The mRNA expression levels of inflammatory cytokines (IL-8 and TNF-α) and related pathway components (toll-like receptor 4, myeloid differentiation primary response gene 88, and nuclear factor-κB) were increased significantly in both the livers and kidneys in the HSD group. The mRNA expression levels of enzymes (adenosine deaminase, xanthine oxidase, phosphoribosyl pyrophosphate amidotransferase, and phosphoribosyl pyrophosphate synthetase 1) related to the synthesis of uric acid increased significantly in the livers in the HSD group. However, the mRNA expression level of solute carrier family 2 member 9, which plays an important role in the excretion of uric acid by the kidney, was decreased significantly in the kidneys in the HSD group.

CONCLUSION

These results indicated that a higher SD could cause tissue inflammatory lesions in the liver and kidney and subsequently affect the metabolism and homeostasis of uric acid, and is helpful for guiding decisions related to the breeding and production of ducks.

Therapeutic potential of orally applied KB-R7943 in streptozotocin-induced neuropathy in rats

Both peripheral neuropathy and depression can be viewed as neurodegeneration's consequences of diabetes, at least in part coexisting with or resulting from sodium-calcium dysbalance. This study aims to assess the therapeutic potential of the orally applied reverse-mode inhibitor of the sodium-calcium exchanger (NCX) KB-R7943 in the streptozotocin (STZ) diabetes model in rats. A pilot pharmacokinetic (PK) study with high-performance liquid chromatography with high-resolution tandem mass spectrometric detection revealed higher drug exposure (AUC), lower volume of distribution (Vd) and clearance (Cl), and faster decline of the plasma concentration (ƛ) in rats with diabetes vs. controls. Brain and heart accumulation and urinary excretion of the unmetabolized KB-R7943 at least 24 h were also demonstrated in all rats. However, heart and hippocampus KB-R7943 penetration (AUCtissue/AUCplasma) was higher in controls vs. diabetic rats. The development of thermal, mechanical, and chemical-induced allodynia was assessed with the Cold plate test (CPT), Randall-Stiletto (R-S) test, and 0.5% formalin test (FT). Amitriptyline 10 mg/kg, KB-R7943 5 mg/kg, or 10 mg/kg p.o once daily was applied from the 28th to the 49th day. The body weight, coat status, CPT, R-S, and FT were evaluated on days (-5), 0, and 42. On day 41, a forced swim test and 24-h spontaneous physical activities were assessed. The chronic treatment effects were calculated as % of the maximum. A dose-depended amelioration of neuropathic and depression-like effects was demonstrated. The oral application of KB-R7943 for potentially treating neurodegenerative consequences of diabetes merits further studies. The brain, heart, and kidneys are essential contributors to the PKs of this drug, and their safety involvement needs to be further characterized.

Pharmacological inhibition of Src family kinases attenuates hyperuricemic nephropathy

Hyperuricemia is an independent risk factor for chronic kidney disease and contributes to renal fibrosis. This study aims to investigate the effect of Src family kinase (SFK) inhibition on the development of hyperuricemic nephropathy (HN) and the mechanisms involved. In a rat model of HN, feeding rats a mixture of adenine and potassium oxonate increased Src phosphorylation, severe glomerular sclerosis, and renal interstitial fibrosis, accompanied by renal dysfunction and increased urine microalbumin excretion. Administration of PP1, a highly selective SFK inhibitor, prevented renal dysfunction, reduced urine microalbumin, and inhibited activation of renal interstitial fibroblasts and expression of extracellular proteins. PP1 treatment also inhibited hyperuricemia-induced activation of the TGF-β1/Smad3, STAT3, ERK1/2, and NF-κB signaling pathways and expression of multiple profibrogenic cytokines/chemokines in the kidney. Furthermore, PP1 treatment significantly reduced serum uric acid levels and xanthine oxidase activity. Thus, blocking Src can attenuate development of HN via a mechanism associated with the suppression of TGF-β1 signaling, inflammation, and uric acid production. The results suggest that Src inhibition might be a promising therapeutic strategy for HN.

A Possible Therapeutic Application of the Selective Inhibitor of Urate Transporter 1, Dotinurad, for Metabolic Syndrome, Chronic Kidney Disease, and Cardiovascular Disease

The reabsorption of uric acid (UA) is mainly mediated by urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in the kidneys. Dotinurad inhibits URAT1 but does not inhibit other UA transporters, such as GLUT9, ATP-binding cassette transporter G2 (ABCG2), and organic anion transporter 1/3 (OAT1/3). We found that dotinurad ameliorated the metabolic parameters and renal function in hyperuricemic patients. We consider the significance of the highly selective inhibition of URAT1 by dotinurad for metabolic syndrome, chronic kidney disease (CKD), and cardiovascular disease (CVD). The selective inhibition of URAT1 by dotinurad increases urinary UA in the proximal tubules, and this un-reabsorbed UA may compete with urinary glucose for GLUT9, reducing glucose reabsorption. The inhibition by dotinurad of UA entry via URAT1 into the liver and adipose tissues increased energy expenditure and decreased lipid synthesis and inflammation in rats. Such effects may improve metabolic parameters. CKD patients accumulate uremic toxins, including indoxyl sulfate (IS), in the body. ABCG2 regulates the renal and intestinal excretion of IS, which strongly affects CKD. OAT1/3 inhibitors suppress IS uptake into the kidneys, thereby increasing plasma IS, which produces oxidative stress and induces vascular endothelial dysfunction in CKD patients. The highly selective inhibition of URAT1 by dotinurad may be beneficial for metabolic syndrome, CKD, and CVD.

Korean Red Ginseng Ameliorates the Level of Serum Uric Acid via Downregulating URAT1 and Upregulating OAT1 and OAT3

Hyperuricemia is caused by an imbalance of uric acid and is associated with many diseases. Although gout which is one of hyperuricemia-related diseases is curable with anti-hyperuricemic drugs some medications have side effects, such as hypersensitivity in patients with circulatory system disorders, flare reoccurrences, and increased cardiac risk. This study consisted of test tube (xanthine oxidase's inhibition) and animal study. Animal study using with ICR mice was composed of control, potassium oxonate-induced hyperuricemia, allopurinol, and 3 Korean red ginseng water extract (KRGWE) treatment groups (62.5; 125, and 500 mg/kg). We orally administered KRGWE once a day for 7 d to induce hyperuricemia and injected PO 2 h before the final KRGWE administration. We measured serum uric acid, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen, and creatinine and analyzed the genes such as organic anion transport (OAT)-1, OAT-3, and urate transport (URAT)-1. KRGWE dose-dependently controlled xanthine oxidase activity in the serum and completely inhibited serum uric acid. KRGWE affected both uric acid excretion-related and uric acid reabsorption-related gene expression. KRGWE stimulated uric acid excretion-related gene expressions, such as OAT-1 and OAT-3, but inhibited uric acid reabsorption-related gene expression, such as URAT-1. KRGWE improved liver and kidney functioning. KRGWE improved liver/kidney functioning and is promising anti-hyperuricemic agent which can control serum uric acid via downregulating URAT1 and upregulating OAT1 and OAT3.

Effectiveness and safety of different doses of febuxostat compared with allopurinol in the treatment of hyperuricemia: a meta-analysis of randomized controlled trials

BACKGROUND

The prevalence of hyperuricemia has increased steadily with the continuous improvement of living standards. Some studies have reported the clinical effectiveness and safety of different doses of febuxostat in comparison with allopurinol in hyperuricemia treatment, but the sample sizes of the studies have been small, and the results have been inconsistent. We designed this meta-analysis to evaluate the effectiveness and safety of different doses of febuxostat compared with allopurinol in the treatment of hyperuricemia.

METHODS

The Cochrane Library, Embase, PubMed, Web of Science and ClinicalTrials.gov databases were searched to identify randomized controlled trials (RCTs) comparing the use of febuxostat and allopurinol for the treatment of hyperuricemia. The effectiveness and safety of different doses of febuxostat and allopurinol in treating hyperuricemia were assessed using meta-analysis.

RESULTS

A total of 11 randomized controlled trials were included in the meta-analysis. The results of the meta-analysis showed that the percentage of patients achieving serum uric acid levels of 6.0 mg/dL or less was higher among patients taking febuxostat (80 mg/d) than among patients taking allopurinol (200-300 mg/d) [RR = 1.79, 95% CI (1.55, 2.08), P < 0.00001]. However, there was no statistically significant difference in the percentage of patients achieving serum uric acid levels of 6.0 mg/dL or less between febuxostat (40 mg/d) and allopurinol (200-300 mg/d) [RR = 1.10, 95% CI (0.93, 1.31), P = 0.25]. There was also no statistically significant difference in the incidence of gout between the febuxostat (40 mg/d) and allopurinol (200-300 mg/d) [RR = 0.97, 95% CI (0.64, 1.49), P = 0.91] or between the febuxostat (80 mg/d) and allopurinol (200-300 mg/d) [RR = 1.13, 95% CI (0.81, 1.58), P = 0.48].No significant difference in the incidence of major adverse reactions as observed between the febuxostat (40 mg/d) and allopurinol (200-300 mg/d) [RR = 1.16; 95% CI (0.43, 3.16), P = 0.77] or between the febuxostat (80 mg/d) and allopurinol (200-300 mg/d) [RR = 1.06; 95% CI (0.79, 1.42), P = 0.70]. The incidence of adverse cardiovascular events did not differ significantly between the febuxostat (40 mg/d) and allopurinol (200-300 mg/d) [RR = 1.30; 95% CI (0.57, 2.95), P = 0.53] or between the febuxostat (80 mg/d) and allopurinol (200-300 mg/d) [RR = 1.79; 95% CI (0.74, 4.32), P = 0.20].

CONCLUSIONS

Febuxostat (80 mg/d) was associated with a higher percentage of patients achieving serum uric acid levels of 6.0 mg/dL or less than allopurinol (200-300 mg/d), however, febuxostat (80 mg/d) did not exhibit better efficacy in reducing the incidence of gout. More attention should be devoted to the adverse reactions caused by an increase in febuxostat doses.

Understanding Hyperuricemia: Pathogenesis, Potential Therapeutic Role of Bioactive Peptides, and Assessing Bioactive Peptide Advantages and Challenges

Hyperuricemia is a medical condition characterized by an elevated level of serum uric acid, closely associated with other metabolic disorders, and its global incidence rate is increasing. Increased synthesis or decreased excretion of uric acid can lead to hyperuricemia. Protein peptides from various food sources have demonstrated potential in treating hyperuricemia, including marine organisms, ovalbumin, milk, nuts, rice, legumes, mushrooms, and protein-rich processing by-products. Through in vitro experiments and the establishment of cell or animal models, it has been proven that these peptides exhibit anti-hyperuricemia biological activities by inhibiting xanthine oxidase activity, downregulating key enzymes in purine metabolism, regulating the expression level of uric acid transporters, and restoring the composition of the intestinal flora. Protein peptides derived from food offer advantages such as a wide range of sources, significant therapeutic benefits, and minimal adverse effects. However, they also face challenges in terms of commercialization. The findings of this review contribute to a better understanding of hyperuricemia and peptides with hyperuricemia-alleviating activity. Furthermore, they provide a theoretical reference for developing new functional foods suitable for individuals with hyperuricemia.

Study on the mechanism of Orthosiphon aristatus (Blume) Miq. in the treatment of hyperuricemia by microbiome combined with metabonomics

ETHNOPHARMACOLOGICAL RELEVANCE

Growing evidence indicates that hyperuricemia is closely associated with gut microbiota dysbiosis. Orthosiphon aristatus (Blume) Miq. (O. aristatus), as a traditional Chinese medicine, has been widely used to treat hyperuricemia in China. However, the mechanism by which O. aristatus treats hyperuricemia has not been clarified.

AIM OF THE STUDY

In this study, we investigated whether the molecular mechanism underlying the anti-hyperuricemia effect of O. aristatus is related to the regulation of gut microbiota by 16S rDNA gene sequencing combined with widely targeted metabolomics.

MATERIALS AND METHODS

Hyperuricemia was induced in rats by administration of 10% fructose and 20% yeast, and the uricosuric effect was assessed by measuring the uric acid (UA) levels in serum and cecal contents. Intestinal morphology was observed by hematoxylin and eosin (HE) staining. To explore the effects of O. aristatus on the gut microbiota and its metabolites, we utilized 16S rDNA gene sequencing combined with widely targeted metabolomics. Furthermore, metabolic pathway enrichment analysis was performed on the screened differential metabolites. The real time quantitative polymerase chain reaction (RT-PCR) and western blotting (WB) were used to detect the expression of relevant proteins in the key pathway.

RESULTS

Our results indicated that O. aristatus intervention decreased serum UA levels and increased the UA levels in cecal contents in hyperuricemic rats. Additionally, O. aristatus improved intestinal morphology and altered the composition of the gut microbiota and its metabolites. Specifically, 16S rDNA revealed that O. aristatus treatment significantly reduced the abundance of unidentified-Ruminococcaceae and Lachnospiraceae-NK4A136-group. Meanwhile, widely targeted metabolomics showed that 17 metabolites, including lactose, 4-oxopentanoate and butyrate, were elevated, while 55 metabolites, such as flavin adenine dinucleotide and xanthine, were reduced. Metabolic pathway enrichment analysis found that O. aristatus was mainly involved in purine metabolism. Moreover, RT-PCR and WB suggested that O. aristatus could significantly up-regulate the expression of UA excretion transporter ATP-binding cassette subfamily G member 2 (ABCG2) in the intestine.

CONCLUSION

O. aristatus exerts UA-lowering effect by regulating the gut microbiota and ABCG2 expression, indicating that this herb holds great promise in the treatment of hyperuricemia.

Whey protein peptides PEW and LLW synergistically ameliorate hyperuricemia and modulate gut microbiota in potassium oxonate and hypoxanthine-induced hyperuricemic rats

Pro-Glu-Trp (PEW) and Leu-Leu-Trp (LLW) are peptides derived from whey protein digestive products; both peptides exhibit xanthine oxidase inhibitory activity in vitro. However, it remains unclear whether these peptides can alleviate hyperuricemia (HUA) in vivo. In this study, we investigated the roles of PEW and LLW, both individually and in combination, in alleviating HUA induced by potassium oxonate and hypoxanthine. Together, PEW and LLW exhibited synergistic effects in reducing the serum levels of uric acid (UA), creatinine, and blood urea nitrogen, as well as increasing the fractional excretion of UA. The combined treatment with PEW and LLW inhibited UA synthesis, promoted UA excretion, and restored renal oxidative stress and mitochondrial damage. Moreover, the combined treatment alleviated dysbiosis of the gut microbiota, characterized by increased helpful microbial abundance, decreased harmful bacterial abundance, and increased production of short-chain fatty acids. Taken together, these results indicate that the combination of PEW and LLW mitigate HUA and kidney injury by rebalancing UA synthesis and excretion, modulating gut microbiota composition, and improving oxidative stress.

Mammary gland, kidney and rumen urea and uric acid transporters of dairy cows differing in milk urea concentration

The milk urea concentration (MUC) serves as indicator of urinary nitrogen emissions, but at comparable crude protein (CP) intake, cows with high (HMU) and low (LMU) MUC excrete equal urea amounts. We hypothesized that urea and uric acid transporters and sizes of the kidney, mammary gland, and rumen account for these phenotypes. Eighteen HMU and 18 LMU Holstein dairy cows fed a low (LP) and normal (NP) CP diet were studied. Milk, plasma and urinary urea concentrations were greater with NP feeding, while plasma and urinary urea concentrations were comparable between phenotypes. Milk and plasma uric acid concentrations were higher with LP feeding but not affected by phenotype. The milk-urine uric acid ratio was greater in HMU cows. The mRNA expressions of the ruminal urea transporter SLC14A1 and AQP10, the mammary gland and rumen AQP3, and the mammary gland uric acid transporter ABCG2 were not affected by group or diet. Renal AQP10, but not AQP3, AQP7, and SLC14A2 expressions, and the kidney weights were lower in HMU cows. These data indicate that renal size and AQP10 limit the urea transfer from blood to urine, and that MUC determines if uric acid is more released with milk or urine.

Dieting alleviates hyperuricemia and organ injuries in uricase-deficient rats via down-regulating cell cycle pathway

Dieting is a basic treatment for lowering hyperuricemia. Here, we aimed to determine the optimal amount of dietary food that lowers serum uric acid (SUA) without modifying the dietary ingredients in rats. Increased SUA was found in food-deprived 45-day-old uricase-deficient rats (Kunming-DY rats), and the optimal amount of dietary food (75% dietary intake) to lower SUA was established by controlling the amount of food given daily from 25% to 100% for 2 weeks. In addition to lowering SUA by approximately 22.5 ± 20.5%, the optimal amount of dietary food given for 2 weeks inhibited urine uric acid excretion, lowered the uric acid content in multiple organs, improved renal function, lowered serum triglyceride, alleviated organ injuries (e.g., liver, kidney and intestinal tract) at the histological level, and down-regulated the Kyoto Encyclopedia of Genes and Genome (KEGG) pathway of the cell cycle (ko04110). Taken together, these results demonstrate that 75% dietary food effectively lowers the SUA level without modifying dietary ingredients and alleviates the injuries resulting from uricase deficiency or hyperuricemia, the mechanism of which is associated with the down-regulation of the cell cycle pathway.

Research progress on the prevention and treatment of hyperuricemia by medicinal and edible plants and its bioactive components

Hyperuricemia is another common metabolic disease, which is considered to be closely related to the development of many chronic diseases, in addition to the "three highs." Currently, although drugs show positive therapeutic effects, they have been shown to produce side effects that can damage the body. There is growing evidence that medicinal and edible plants and their bioactive components have a significant effect on hyperuricemia. In this paper, we review common medicinal and edible plants with uric acid-lowering effects and summarize the uric acid-lowering mechanisms of different bioactive components. Specifically, the bioactive components are divided into five categories: flavonoids, phenolic acids, alkaloids, polysaccharides, and saponins. These active substances exhibit positive uric acid-lowering effects by inhibiting uric acid production, promoting uric acid excretion, and improving inflammation. Overall, this review examines the potential role of medicinal and edible plants and their bioactive components as a means of combating hyperuricemia, with the hope of providing some reference value for the treatment of hyperuricemia.

Temporal relationship between hyperuricemia and hypertension and its impact on future risk of cardiovascular disease

BACKGROUND

Although hyperuricemia and hypertension are significantly correlated, their temporal relationship and whether this relationship is associated with risk of cardiovascular disease (CVD) are largely unknown. This study aimed to examine temporal relationship between hyperuricemia and hypertension, and its association with future risk of CVD.

METHODS

This study included 60,285 participants from the Kailuan study. Measurement of serum uric acid (SUA), systolic and diastolic blood pressure (SBP and DBP) were obtained twice at 2006 (baseline) and 2010. Cross-lagged and mediation analysis were used to examine the temporal relationship between hyperuricemia and hypertension, and the association of this temporal relationship with CVD events risk after 2010.

RESULTS

After adjusting for covariates, the cross-lagged path coefficients (β1) from baseline SUA to follow-up SBP and DBP were significantly greatly than path coefficients (β2) from baseline SBP and DBP to follow-up SUA (β1=0.041 versus β2=0.003; Pdifference<0.0001 for SBP; β1=0.040 versus β2=0.000; Pdifference<0.0001 for DBP). The path coefficients from baseline SUA to follow-up SBP and DBP in group with incident CVD were significantly greatly than that in group without incident CVD (Pdifference of β1 in the two groups was 0.0018 for SBP and 0.0340 for DBP). Furthermore, SBP and DBP partially mediated the effect of SUA on incident CVD, the mediation effect was 57.64% for SBP and 46.27% for DBP. Similar mediated results were observed for stroke and myocardial infarction.

CONCLUSION

Increased SUA levels probably precede elevated BP, and BP partially mediates the pathway from SUA to incident CVD.

Pharmacological evaluation of a novel skeleton compound isobavachin (4',7-dihydroxy-8-prenylflavanone) as a hypouricemic agent: Dual actions of URAT1/GLUT9 and xanthine oxidase inhibitory activity

Previously we discovered a novel natural scaffold compound, isobavachin (4', 7-dihydroxy-8-prenylflavanone), as a potent URAT1 inhibitor by shape and structure based on a virtue screening approach. In this study, further urate-lowering mechanism, pharmacokinetics and toxicities of isobavachin were conducted. Isobavachin inhibited URAT1 with an IC₅₀ value of 0.24 ± 0.06 μM, and residues S35, F365, I481 and R477 of URAT1 contributed to high affinity for isobavachin. Isobavachin also inhibited glucose transporter 9 (GLUT9), another pivotal urate reabsorption transporter, with an IC₅₀ value of 1.12 ± 0.26 μM. Molecular docking and MMGBSA results indicated that isobavachin might compete residues R171, L75 and N333 with uric acid, which leads to inhibition of uric acid transport of GLUT9. Isobavachin weakly inhibited urate secretion transporters OAT1 with an IC₅₀ value of 4.38 ± 1.27 μM, OAT3 with an IC₅₀ of 3.64 ± 0.62 μM, and ABCG2 with an IC₅₀ of 10.45 ± 2.17 μM. Isobavachin also inhibited xanthine oxidase (XOD) activity in vitro with an IC₅₀ value of 14.43 ± 3.56 μM, and inhibited the hepatic XOD activities at 5-20 mg/kg in vivo. Docking and MMGBSA analysis indicated that isobavachin might bind to the Mo-Pt catalyze center of XOD, which leads to inhibition of uric acid production. In vivo, isobavachin exhibited powerful urate-lowering and uricosuric effects at 5-20 mg/kg compared with the positive drugs morin (20 mg/kg) and RDEA3170 (10 mg/kg). Safety assessments revealed that isobavachin was safe and had no obvious toxicities. Isobavachin has little cell toxicity in HK2 cells as indicated by the MTT assay. In vivo, after treatment with 50 mg/kg isobavachin for 14 days, isobavachin had little renal toxicity, as revealed by serum CR/BUN levels, and no hepatotoxicity as revealed by ALT/AST levels. Further HE examination also suggests that isobavachin has no obvious kidney/liver damage. A pharmacokinetic study in SD rats indicated isobavachin had lower bioavailability (12.84 ± 5.13 %) but long half-time (7.04 ± 2.68 h) to maintain a continuous plasma concentration. Collectively, these results indicate that isobavachin deserves further investigation as a candidate anti-hyperuricemic drug with a novel mechanism of action: selective urate reabsorption inhibitor (URAT1/GLUT9) with a moderate inhibitory effect on XOD.

Kidney Drug Transporters in Pharmacotherapy

The kidney functions not only as a metabolite elimination organ but also plays an important role in pharmacotherapy. The kidney tubule epithelia cells express membrane carriers and transporters, which play an important role in drug elimination, and can determine drug nephrotoxicity and drug-drug interactions, as well as constituting direct drug targets. The above aspects of kidney transport proteins are discussed in the review.

Acute effect of fructose, sucrose, and isomaltulose on uric acid metabolism in healthy participants

Fructose is associated with hyperuricemia and gout development. Focusing on fructose and fructose-containing disaccharides, we investigated the effects of three different types of carbohydrates (fructose, sucrose, and isomaltulose) on uric acid metabolism and gene expression profiling in peripheral white blood cells. In a randomized crossover study, ten healthy participants ingested test drinks of fructose, sucrose, and isomaltulose, each containing 25 g of fructose. Plasma glucose, serum and urine uric acid, and xanthine/hypoxanthine concentrations were measured. Microarray analysis in peripheral white blood cells and real-time reverse transcription polymerase chain reaction were examined at 0 and 120 in after the intake of test drinks. Serum uric acid concentrations for group fructose were significantly higher than group sucrose at 30-120 min and were significantly higher than those for group isomaltulose at 30-240 min. Several genes involved in the "nuclear factor-kappa B signaling pathway" were markedly changed in group fructose. No significant differences in the mRNA expression levels of tumor necrosis factor, nuclear factor-kappa B, interleukin-1β, and interleukin-18 were noted. This study indicated that fructose intake (monosaccharide) elevated serum uric acid concentrations compared with disaccharide intake. Differences in the quality of carbohydrates might reduce the rapid increase of postprandial serum uric acid concentrations.

The Mechanism of Sodium-Glucose Cotransporter-2 Inhibitors in Reducing Uric Acid in Type 2 Diabetes Mellitus

Hyperuricemia is a common comorbidity in patients with type 2 diabetes mellitus (T2DM), as insulin resistance (IR) or hyperinsulinemia is associated with higher serum uric acid (SUA) levels due to decreased uric acid (UA) secretion, and SUA vice versa is an important risk factor that promotes the occurrence and progression of T2DM and its complications. Growing evidence suggests that sodium-glucose cotransporter 2 inhibitors (SGLT-2i), a novel anti-diabetic drug initially developed to treat T2DM, may exert favorable effects in reducing SUA. Currently, one of the possible mechanisms is that SGLT2i increases urinary glucose excretion, probably inhibiting glucose transport 9 (GLUT9)-mediated uric acid reabsorption in the collecting duct, resulting in increased uric acid excretion in exchange for glucose reabsorption. Regardless of this possible mechanism, the underlying comprehensive mechanisms remain poorly elucidated. Therefore, in the present review, a variety of other potential mechanisms will be covered to identify the therapeutic role of SGLT-2i in hyperuricemia.

Anti-hyperuricemia effect of hesperetin is mediated by inhibiting the activity of xanthine oxidase and promoting excretion of uric acid

Hesperetin is a natural flavonoid with many biological activities. In view of hyperuricemia treatment, the effects of hesperetin in vivo and in vitro, and the underlying mechanisms, were explored. Hyperuricemia models induced by yeast extract (YE) or potassium oxonate (PO) in mice were created, as were models based on hypoxanthine and xanthine oxidase (XOD) in L-O2 cells and sodium urate in HEK293T cells. Serum level of uric acid (UA), creatinine (CRE), and urea nitrogen (BUN) were reduced significantly after hesperetin treatment in vivo. Hesperetin provided hepatoprotective effects and inhibited xanthine oxidase activity markedly, altered the level of malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and catalase (CAT), downregulated the XOD protein expression, toll-like receptor (TLR)4, nucleotide binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, interleukin-18 (IL-18), upregulated forkhead box O3a (FOXO3a), manganese superoxide dismutase (MnSOD) in a uric acid-synthesis model in mice. Protein expression of organic anion transporter 1 (OAT1), OAT3, organic cationic transporter 1 (OCT1), and OCT2 was upregulated by hesperetin intervention in a uric acid excretion model in mice. Our results proposal that hesperetin exerts a uric acid-lowering effect through inhibiting xanthine oxidase activity and protein expression, intervening in the TLR4-NLRP3 inflammasome signaling pathway, and up-regulating expression of FOXO3a, MnSOD, OAT1, OAT3, OCT1, and OCT2 proteins. Thus, hesperetin could be a promising therapeutic agent against hyperuricemia.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2020-present)

INTRODUCTION

The urate transporter 1 (URAT1) is a membrane transporter located in the apical membrane of human renal proximal tubule epithelial cells, which mediates most of the reabsorption of urate. Hyperuricemia (HUA) is a common disease caused by metabolic disorders, which has been considered as the key factor of gout. Approximately 90% of patients suffer from hyperuricemia due to insufficient or poor uric acid excretion. Therefore, the drug design of URAT1 inhibitors targeting improve the renal urate excretion by reducing the reabsorption of urate anions represent a hot topic in searching for anti-gout drugs currently.

AREAS COVERED

In this review, we summarize URAT1 inhibitors patents reported since 2020 to present through the public database at https://worldwide.espacenet.com and some medicinal chemistry strategies employed to develop novel drug candidates.

EXPERT OPINION

Ligand-based drug design (LBDD) strategies have been frequently used developing new URAT1 inhibitors. Meanwhile, the discovery of dual drugs targeting both inhibition of xanthine oxidase (XOD) and URAT1 may be an emerging horizon for designing novel uric acid-lowering candidates in future. Furthermore, advanced techniques in the field of molecular biology and computer science can increase the chances to discover and/or optimize URAT1 inhibitors, contributing to the development of novel drug candidates.

Extract of Aster glehni ameliorates potassium oxonate-induced hyperuricemia by modulating renal urate transporters and renal inflammation by suppressing TLR4/MyD88 signaling

Recent studies suggest that Aster glehni extract (AGE) reduces hyperuricemia by preventing xanthine oxidase activity. However, its effect on renal urate transporters responsible for modulating urate excretion has not been examined. This study investigated whether AGE affects gene expressions of urate transporters using potassium oxonate (PO)-induced hyperuricemia rats. Furthermore, the underlying mechanisms of AGE were explored to ameliorate renal inflammation and injury by PO. AGE effectively restored PO-induced dysregulation of renal urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), ATP-binding cassette transporter subfamily G member 2 (ABCG2), organic anion transporter 1 (OAT1), and organic cation transporter 1 (OCT1), resulting in increasing urate excretion. Additionally, AGE suppressed toll-like receptor 4/myeloid differentiation factor 88 (TLR4/MyD88) signaling, phosphorylation of nuclear factor kappa B (NF-κB), and renal production of IFN-γ, IL-1β, TNF-α, and IL-6. These results suggest that AGE may ameliorate PO-induced hyperuricemia by modulating renal transporters, and further renal inflammation via inhibiting the TLR4/MyD88/NF-κB signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01153-5.

The Prevalence of Asymptomatic Hyperuricemia in Patients with or Without Psoriatic Arthritis is Associated with a Similar Cardiovascular Risk

Aim: To investigate the association between cardiovascular burden and monosodium urate (MSU) deposits in the joints of patients with asymptomatic hyperuricemia and no evidence of arthritis and subjects with psoriatic arthritis and hyperuricemia.

Patients and methods: A single-center, cross-sectional study including 52 individuals: 39 with asymptomatic hyperuricemia and 13 with psoriatic arthritis and hyperuricemia. All patients underwent ultrasound of the joints by which the presence or absence of MSU crystal deposits was assessed. Subjects underwent transthoracic echocardiography by which left ventricular mass index (LVMI) was estimated. Intima-media thickness (IMT) of the common carotid arteries was measured and the presence of atherosclerotic plaques was registered.

Results: We found no difference in the distribution of cardiovascular risk factors between the two groups. Further, no difference in their distribution was found between those who were not treated and those who were treated with urate-lowering medications. The frequency of articular MSU deposits was similar between non-allopurinol-treated and allopurinol-treated individuals (p = 0.554). There was no difference in the frequency of articular deposits between benzbromarone recipients and non-recipients (p = 0.396). We observed no connection between articular MSU deposits and LVMI (p = 0.625), IMT (p = 0.117) and atherosclerotic plaques (p = 0.102). Among untreated and treated with urate-lowering drugs there was no difference in LVMI (p = 0.063), IMT (p = 0.975) and plaque distribution (p = 1.000).

Conclusion: We can assume that in patients with asymptomatic hyperuricemia and no evidence of arthritis and in subjects with psoriatic arthritis and asymptomatic hyperuricemia, only the prescription of urate-lowering medications for reduction of urate load and cardiovascular risk is not sufficient.

Innovative approaches and recent advances in the study of ontogeny of drug metabolism and transport

The disposition of a drug is driven by various processes, such as drug metabolism, drug transport, glomerular filtration and body composition. These processes are subject to developmental changes reflecting growth and maturation along the paediatric continuum. However, knowledge gaps exist on these changes and their clinical impact. Filling these gaps may aid better prediction of drug disposition and creation of age-appropriate dosing guidelines. We present innovative approaches to study these developmental changes in relation to drug metabolism and transport. First, analytical methods such as including liquid chromatography-mass spectrometry for proteomic analyses allow quantitation of the expressions of a wide variety of proteins, e.g. membrane transporters, in a small piece of organ tissue. The latter is specifically important for paediatric research, where tissues are scarcely available. Second, innovative study designs using radioactive labelled microtracers allowed study-without risk for the child-of the oral bioavailability of compounds used as markers for certain drug metabolism pathways. Third, the use of modelling and simulation to support dosing recommendations for children is supported by both the European Medicines Agency and the US Food and Drug Administration. This may even do away with the need for a paediatric trial. Physiologically based pharmacokinetics models, which include age-specific physiological information are, therefore, increasingly being used, not only to aid paediatric drug development but also to improve existing drug therapies.

Research progress of risk factors and early diagnostic biomarkers of gout-induced renal injury

Gout renal injury has an insidious onset, no obvious symptoms, and laboratory abnormalities in the early stages of the disease. The injury is not easily detected, and in many cases, the patients have entered the renal failure stage at the time of diagnosis. Therefore, the detection of gout renal injury–related risk factors and early diagnostic biomarkers of gout renal injury is essential for the prevention and early diagnosis of the disease. This article reviews the research progress in risk factors and early diagnostic biomarkers of gout renal injury.

AMP-activated protein kinase α2 contributes to acute and chronic hyperuricemic nephropathy via renal urate deposition in a mouse model

Hyperuricemia can induce acute and chronic kidney damage, but the pathological mechanism remains unclear. The potential role of AMP-activated protein kinase (AMPK) α2 in hyperuricemia-induced renal injury was investigated in this study. Acute and chronic hyperuricemic nephropathy was induced by administering intraperitoneal injections of uric acid and oxonic acid to AMPK α2 knockout and wild-type mice. Changes in renal function, histopathology, inflammatory cell infiltration, renal interstitial fibrosis, and urate deposition were analyzed. In both acute and chronic hyperuricemic nephropathy mouse models, knockout of AMPK α2 significantly reduced serum creatinine levels and renal pathological changes. The tubular expression of kidney injury molecule-1 was also reduced in hyperuricemic nephropathy mice deficient in AMPK α2. In addition, knockout of AMPK α2 significantly suppressed the infiltration of renal macrophages and progression of renal interstitial fibrosis in mice with chronic hyperuricemic nephropathy. Knockout of AMPK α2 reduced renal urate crystal deposition, probably through increasing the expression of the uric acid transporter, multidrug resistance protein 4. In summary, AMPK α2 is involved in acute and chronic hyperuricemia-induced kidney injury and may be associated with increased urate crystal deposition in the kidney.

Differences of Uric Acid Transporters Carrying Extracellular Vesicles in the Urine from Uric Acid and Calcium Stone Formers and Non-Stone Formers

Background: Low urine pH and volume are established risk factors for uric acid (UA) stone disease (UASD). Renal tubular epithelial cells exposed to an acidic pH and/or UA crystals can shed extracellular vesicles (EVs) into the tubular fluid, and these EVs may be a pathogenic biomarker of UASD. Methods: Urinary EVs bearing UA transporters (SLC2A9, SLC17A3, SLC22A12, SLC5A8, ABCG2, and ZNF365) were quantified in urine from UA stone formers (UASFs), calcium stone formers (CSFs), and age-/sex-matched non-stone formers (NSFs) using a standardized and published method of digital flow cytometry. Results: Urinary pH was lower (p < 0.05) and serum and urinary UA were greater (p < 0.05) in UASFs compared with NSFs. Urinary EVs carrying SLC17A3 and SLC5A8 were lower (p < 0.05) in UASFs compared with NSFs. Urinary EVs bearing SLC2A9, SLC22A12, SLC5A8, ABCG2, and ZNF365 were lower (p < 0.05) in CSFs than UASFs, while excretion of SLC17A3-bearing EVs did not differ between groups. Conclusion: EVs bearing specific UA transporters might contribute to the pathogenesis of UASD and represent non-invasive pathogenic biomarkers for calcium and UA stone risk.

Traditional Chinese herbs and natural products in hyperuricemia-induced chronic kidney disease

Hyperuricemia is a common biochemical disorder, which resulted from both excessive uric acid (UA) production and/or absolute or relative impairment of urinary UA excretion. Growing evidence has indicated that hyperuricemia is an independent risk factor for the development and progression of chronic kidney disease (CKD), causing hyperuricemia-induced CKD (hyperuricemic nephropathy, HN). The therapeutic strategy of HN is managing hyperuricemia and protecting kidney function. Adverse effects of commercial drugs make persistent treatment of HN challenging. Traditional Chinese medicine (TCM) has exact efficacy in lowering serum UA without serious adverse effects. In addition, TCM is widely applied for the treatment of CKD. This review aimed to provide an overview of efficacy and mechanisms of traditional Chinese herbs and natural products in hyperuricemia-induced CKD.

Analysis of Purine Metabolism to Elucidate the Pathogenesis of Acute Kidney Injury in Renal Hypouricemia

Renal hypouricemia is a disease caused by the dysfunction of renal urate transporters. This disease is known to cause exercise-induced acute kidney injury, but its mechanism has not yet been established. To analyze the mechanism by which hypouricemia causes renal failure, we conducted a semi-ischemic forearm exercise stress test to mimic exercise conditions in five healthy subjects, six patients with renal hypouricemia, and one patient with xanthinuria and analyzed the changes in purine metabolites. The results showed that the subjects with renal hypouricemia had significantly lower blood hypoxanthine levels and increased urinary hypoxanthine excretion after exercise than healthy subjects. Oxidative stress markers did not differ between healthy subjects and hypouricemic subjects before and after exercise, and no effect of uric acid as a radical scavenger was observed. As hypoxanthine is a precursor for adenosine triphosphate (ATP) production via the salvage pathway, loss of hypoxanthine after exercise in patients with renal hypouricemia may cause ATP loss in the renal tubules and consequent tissue damage.

An evaluation method for uric acid uptake inhibition using primary human proximal tubule epithelial cells treated with insulin

The effects of uricosuric agents have been evaluated in vitro with indices of uric acid uptake into human urate transporter 1 (URAT1)-overexpressed oocytes or cells. In the present study, we evaluated a method using primary human renal proximal tubule epithelial cells (RPTECs). Pretreatment of RPTECs with insulin significantly increased the uptake of uric acid into these cells. The uric acid uptake was inhibited in a concentration-dependent manner by the URAT1 inhibitors benzbromarone and dotinurad. Therefore, effects of uricosuric agents can be evaluated by the novel method, which is closer to the physiological system compared with previous methods.