Hyperuricemia and Associated Diseases

Prunus mume Alleviates Hyperuricemic Renal Injury: Insights From Network Pharmacology and Experimental Models

Prunus mume (PM), the dried flower bud of a Rosaceae plant, has a long history of use for its liver-soothing, depression-relieving, and appetite-stimulating effects. Recently, PM has gained attention for its anti-inflammatory, antioxidant, and uric acid-lowering properties. The chemical composition of PM was analyzed using network pharmacology and liquid chromatography-mass spectrometry (LC-MS). The therapeutic potential of PM for hyperuricemia-induced kidney damage was evaluated in a quail model. Antioxidant activity in an HK-2 cell model of hyperuricemia was assessed by measuring the levels of MDA, SOD, and GSH. Additionally, the anti-inflammatory potential was examined using ELISA to measure TNF-α and IL-6 levels. Western blotting was employed to study the effects on URAT1, GLUT9, and the PI3K/AKT pathway. LC-MS identified 284 compounds in PM, with 35 predicted active ingredients. The quail model demonstrated PM's protective effects on the kidneys under hyperuricemic conditions. In vitro, PM reduced oxidative stress and lowered TNF-α and IL-6 levels. It also modulated URAT1 and GLUT9 expression and influenced the PI3K/AKT pathway. PM shows promise in protecting kidneys from hyperuricemia-induced damage, likely through its anti-inflammatory and antioxidant activities, as well as the regulation of urate transport proteins and the PI3K/AKT pathway.

Covalent Coupling-Regulated rGO/VN Nanocomposite Enabling Nitrogen Defects to Remarkably Boost the Peroxidase-Like Catalytic Efficiency for the Ultrasensitive Colorimetric Assay of Uric Acid

It remains challenging to rationally design superior nanozymes and understand the underlying mechanism. Herein, a facile covalent coupling-modulated nitrogen defect is reported for significantly boosting peroxidase (POD)-like activity. Vanadium nitride (VN) nanoparticles are grown on graphene oxide (GO) via C-N bonding to form VN/rGO nanocomposites by varying with the VOx/GO ratio. The initial increasing GO amount enables formation of the C-N bond, dramatically boosting POD-like activity. Nevertheless, with a higher GO amount, the nitrogen defects decrease due to forming mainly V2O3. The defect-rich VN/rGO nanocomposite with 20 wt % GO (VG-2) exhibits the best catalytic efficiency (Vmax/Km = 0.0187 s-1), which is 778-fold higher than that of natural horseradish peroxidase. Theoretical calculations and structure characterization reveal that the rich-N defects originate from VN covalent binding onto rGO with an rich-electron structure, impeding VN agglomeration, which greatly reduces the energy barrier of the rate-determining step of the catalytic reaction. Finally, coupling urate oxidase with VG-2 as an enzyme cascade, an ultrasensitive and selective colorimetric detection was developed for uric acid (UA), one of the indicators of kidney function or gout attacks, with a linear detection ranging 1-100 μM and 0.1-2.5 mM with a limit of detection of 0.24 μM UA (S/N = 3). The proposed method was applicable to detecting UA in human serum samples satisfactorily. This work could inspire more effective insights into designing other robust nanozymes through covalent coupling for a variety of biochemical analysis and biocatalysis applications.

Rational design of Ag-doped MnFe2O4/HNTs for peroxidase-mimicking activity and colorimetric sensing of uric acid in human serum

Mimicking enzyme have significantly advanced sensing assays by replicating native enzyme functions, yet achieving both high catalytic activity and easy recyclability remains a challenge. In this study, Ag-doped MnFe2O4/halloysite nanotubes (HNTs) were rationally designed as a novel nanozyme by depositing in-situ Ag and MnFe2O4 nanoparticles onto HNTs. The resulting nanocomposite exhibited excellent peroxidase-like activity along with magnetic properties. Leveraging these features, a highly efficient and sensitive colorimetric system for detecting uric acid (UA) was developed. The Ag-doped MnFe2O4/HNTs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2, causing a color change from colorless to blue. The system showed a linear absorbance response to UA concentrations ranging from 1 to 20 μM, with a detection limit of 59 nM. Mechanistic studies revealed that reactive oxygen species intermediates (1O2) were generated through the decomposition of H2O2, leading to peroxidase-like activity in the Ag-doped MnFe2O4/HNTs. The assay was successfully applied to detect UA in human serum with recoveries over 99.68 %. This study indicates the successful application of Ag-doped MnFe2O4/HNTs for colorimetric UA detection in human serum. This research introduces a novel approach for designing recyclable, high-performance mimicking enzyme and establishes an effective colorimetric sensing platform for UA detection in human serum.

Periodontal disease and serum uric acid levels in the absence of metabolic syndrome: is there a link? A study on a sample of Cameroonian adults

BACKGROUND

The relationship between serum uric acid level (SUA) and periodontal diseases (PD) is still controversial, and few studies have been carried out in population with no element of metabolic syndrome especially in sub-Saharan Africa. The aim of this study was to assess the relationship between PD and SUA in Cameroonian adults not suffering from metabolic syndrome.

METHODS

We carried out a cross-sectional study including Cameroonians aged over 18 years recruited in the general population and free of metabolic syndrome elements. They were assessed for frequency of consumption of purine-rich foods, periodontal indices (plaque index, gingival index, calculus index, pocket depth and clinical loss of attachment), and SUA. The diagnosis of PD was based on the American Academy of Periodontology criteria revised in 2015, and hyperuricemia was defined for values exceeding 70 and 60mg/L in men and women respectively. Comparison of SUA means was performed with the ANOVA test. Association between hyperuricemia and PD were evaluated using Fischer's exact test. The threshold of significance was 0.05.

RESULTS

One hundred and seventy-four participants were included (57.5% women, mean age 29 (10.39) years). The frequencies of PD were 75.9%, gingivitis (59.1%) and periodontitis (40.1%). Hyperuricemia was found in 20.45% of people with PD, with no difference in frequency comparing with those without PD. The frequency of consumption of purine-rich foods was similar in individuals with and without PD. Serum uric acid levels were not different in individuals with and without PD, and differed among periodontal indices only for calculus index, where SUA were higher in participants with the highest score (p=0.026). We found no association between hyperuricemia and PD.

CONCLUSION

In individuals without elements of metabolic syndrome, hyperuricemia affects one in five people with PD. There appears to be no link between SUA and overall periodontal status in this population. Further studies are needed to better understand the salivary interaction between uric acid and periodontium in our population.

Supramolecular-platform-assisted selective recognition of uric acid with high sensitivity via microenvironment modulation of a self-assembled probe

This report demonstrates a unique route for translating a non-responsive fluorophore into a responsive one to optically recognize uric acid (UA) in physiological-mimicking conditions. The explicit 'turn ON-turn OFF' fluorescence switching upon sequential disaggregation-reaggregation of the self-aggregated 3,3'-bisindolyl(phenyl)methane molecules materializes a straightforward, trouble-free supramolecular UA sensing platform.

Bariatric Surgery and Its Metabolic Echo Effect on Serum Uric Acid Levels

Bariatric surgery (BS) has been a significant means of reducing weight in obese individuals. The metabolic changes after bariatric surgery are crucial as they extend its advantages beyond weight loss. As its name implies, "metabolic surgery" also addresses obesity-related metabolic concerns. Bariatric surgery has always been associated with lessened serum uric acid (SUA) levels. In this review, we examined current studies to understand how surgical therapies impact serum uric acid levels. Strongly minded on the extent and timing of changes in the level of serum uric acid after bariatric surgeries. We conducted a comprehensive search for relevant current studies in PubMed, Google Scholar, JAMA, and the Cochrane Library until February 1, 2024. We aimed to analyze the metabolic advantages of bariatric surgery, focusing on its function in treating hyperuricemia and lowering the risk of associated disorders. Our review elaborates on factors contributing to decreased serum uric acid levels after bariatric surgery, such as alterations in renal function, insulin sensitivity, and inflammatory markers.

Pathology, target discovery, and the evolution of XO inhibitors from the first discovery to recent advances (2020-2023)

Hyperuricemia, a disease characterized by elevation of serum uric acid level beyond 6 mg/dL. This elevation led to appearance of symptoms from joint pain to gout and from gout to difficulty in mobility of the patient. So, in this review, we have summarized the pathology of hyperuricemia, discovery of target and discovery of first XO inhibitor. At last, this review provides in-sights about the recently discovered as natural XO inhibitors, followed by design, structure activity relationship and biological activity of synthetic compounds as XO inhibitors discovered between 2020 and 2023 years. At last, the pharmacophores generated in this study will guide new researchers to design and modify the structure of novel XO inhibitors.

Effect of Hydroxytyrosol Derivatives of Donepezil on the Activity of Enzymes Involved in Neurodegenerative Diseases and Oxidative Damage

Monoamine oxidase and xanthine oxidase inhibitors represent useful multi-target drugs for the prevention, attenuation, and treatment of oxidative damage and neurodegenerative disorders. Chimeric molecules, constituted by naturally derived compounds linked to drugs, represent lead compounds to be explored for the discovery of new synthetic drugs acting as enzyme inhibitors. We have previously reported that seven hydroxytyrosol-donepezil hybrid compounds play a protective role in an in vitro neuronal cell model of Alzheimer's disease. In this work, we analyzed the effects exerted by the hybrid compounds on the activity of monoamine oxidase A (MAO-A) and B (MAO-B), as well as on xanthine oxidase (XO), enzymes involved in both neurodegenerative disorders and oxidative stress. The results pointed to the identification, among the compounds tested, of selective inhibitors between the two classes of enzymes. While the 4-hydroxy-3-methoxyphenethyl 1-benzylpiperidine-4-carboxylate- (HT3) and the 4-hydroxyphenethyl 1-benzylpiperidine-4-carboxylate- donepezil derivatives (HT4) represented the best inhibitors of MAO-A, with a scarce effect on MAO-B, they were almost ineffective on XO. On the other hand, the 4,5-dihydroxy-2-nitrophenethyl 1-benzylpiperidine-4-carboxylate donepezil derivative (HT2), the least efficient MAO inhibitor, acted like the best XO inhibitor. Therefore, the differential enzymatic targets identified among the hybrid compounds synthesized enhance the possible applications of these polyphenol-donepezil hybrids in neurodegenerative disorders and oxidative stress.

A cross-sectional analysis of the relationship between ischemic stroke and uric acid in young people in highland areas

Objective

To investigate the relationship between serum uric acid (SUA) levels and ischemic stroke in young patients in the Ganzi Tibetan plateau area.

Methods

A cross-sectional survey was undertaken from January 2020 to June 2023 involving young patients (age: 15-45 years) diagnosed with ischemic stroke. The survey was conducted at the Department of Internal Medicine of the People's Hospital of Derong County, Ganzi Prefecture. The participants underwent a comprehensive assessment, including questionnaire surveys, physical examinations, laboratory tests, and head computed tomography (CT) examinations. Based on the tertiles of serum uric acid (SUA) levels, the patients were stratified into three groups. Furthermore, stroke severity was classified into mild (1-4 points), moderate (5-15 points), and severe (>15 points) categories using the National Institute of Health Stroke Scale.

Results

The severe stroke group exhibited higher levels of age, glucose, systolic blood pressure, serum triglyceride, low-density lipoprotein cholesterol, and serum uric acid (SUA) compared to the mild stroke group (P < 0.05). Furthermore, the likelihood of male sex, advanced age, smoking, and a family history of stroke, diabetes mellitus, and heart disease were significantly elevated in the severe stroke group compared to the moderate stroke group (P < 0.05). Multivariate logistic regression analysis conducted on young adults residing in highland areas revealed a significant association between SUA levels and the risk of stroke.

Conclusion

Elevated SUA levels serve as a distinct risk factor for the development of a major stroke in young patients in highland areas. At SUA levels of 320.56 mol/L, the risk of a moderate-to-severe stroke is noticeably elevated.

Estimated excretion and clearance of uric acid as optimal surrogate indices for daily urinary uric acid excretion

OBJECTIVES

Daily uric acid excretion (Eua) is an essential index for patients with gout/hyperuricaemia. We identified alternative indices most correlated with 24-hour uric acid clearance (Cua 24 h) and 24-hour Eua (Eua 24 h) using data from the reference interval of urinary clearance and excretion of urate study.

METHODS

The subjects were indoor workers aged 20-65 years who met the Clinical and Laboratory Standards Institute Guidelines C28-A3c. Alternative indices using spot urine were urine uric acid creatinine ratio, Cua-creatinine clearance ratio (Cua/Ccr), Eua-CCr ratio (Eua/Ccr), estimated Cua (eCua), and estimated Eua (eEua). eCua and eEua are the values obtained by multiplying Cua/Ccr and Eua/Ccr with the estimated glomerular filtration rate.

RESULTS

The final number of subjects analysed was 739. Among the indices using spot urine, eCua and eEua showed the highest correlation with Cua 24 h and Eua 24 h, respectively. Compared with Cua 60 min and Eua 60 min obtained from 60-min urine collection, eCua and eEua showed lower root means squared error, lower bias, and significantly higher accuracy of within 30% and within 15%.

CONCLUSIONS

The newly proposed eCua and eEua may be appropriate from a practical perspective.

Review on Uric Acid Recognition by MOFs with a Future in Machine Learning

Uric acid (UA) is produced from purine metabolism and serves as a prevalent biomarker for multiple diseases including cancer. Hyperuricemia or hypouricemia can cause multiple dysfunctions throughout the biological processes. Consequently, there is a pressing need for monitoring UA concentration in body fluid. While clinical methods are known, the availability of a point-of-care testing (PoCT) kit remains conspicuously absent. In the case of electrochemical recognition of UA, the oxidation potential of ascorbic acid closely aligns with that of UA and thus it hinders the detection process, which eventually may result in false positive signals. Several chemosensors are known in the field of supramolecular chemistry, and metal-organic frameworks (MOFs) are one of the best-performing contenders due to their robustness, stability, and versatile structures. In this review, we tried to unbox the up-to-date development of UA sensing by MOFs. We delve into the state of UA recognition by MOFs, exploring both electrochemical and fluorometric pathways and drawing comparisons with structurally similar probes like covalent organic frameworks (COFs) to understand/establish the advantages of MOFs specifically in UA sensing. In the absence of a PoCT kit, we have provided the conceptual outlook for designing a PoCT device termed a "Urimeter" via electrochemical operation. For the first time, we have proposed different methods of how UA sensing can be tied up with artificial intelligence and machine learning (AI-ML).

Discovery and Characterization of Moracin C as an Anti-Gouty Arthritis/Hyperuricemia Candidate by Docking-Based Virtual Screening and Pharmacological Evaluation

In the present study, a natural product database of compounds associated with herbs traditionally verified to treat gout/hyperuricemia/arthritis was constructed. 3D-shape and docking-based virtual screening was conducted. To identify potential xanthine oxidase (XOD) inhibitors in the database, eight compounds with commercial availability were identified as high 3D-shape similarity with febuxostat (1), a known XOD inhibitor. Docking was used to further predict the possible interactions between XOD and these compounds. Moracin C (2), moracin D (3), and isoformononetin (8) exhibited higher docking scores and binding energies than other compounds. In vitro, 2 inhibited XOD with an IC50 value of 0.25 ± 0.14 μM, which is similar to that of 1 (0.16 ± 0.08 μM). In a hyperuricemic mouse model, 5-20 mg/kg 2 exhibited satisfying urate-lowering and XOD inhibitory effects. Compound 2 also exhibited antiarthritis activities. In RAW264.7 cells, 2 at 1-10 μM inhibited the expression of IL-1β and TNF-α induced by MSU. In an acute gouty arthritis model in SD rats, 5-20 mg/kg 2 significantly alleviated the toe swelling, inflammatory response, and dysfunction disorder caused by monosodium urate (MSU). Compound 2 inhibited serum IL-1β and TNF-α cytokines as well as reduced the expression of the NLRP3/ASC/caspase-1 inflammasome in joints. In summary, 2 was an effective compound for the treatment of hyperuricemia/gouty arthritis.

Novel Reversible Inhibitors of Xanthine Oxidase Targeting the Active Site of the Enzyme

Xanthine oxidase (XO) is a flavoprotein catalysing the oxidation of hypoxanthine to xanthine and then to uric acid, while simultaneously producing reactive oxygen species. Altered functions of XO may lead to severe pathological diseases, including gout-causing hyperuricemia and oxidative damage of tissues. These findings prompted research studies aimed at targeting the activity of this crucial enzyme. During the course of a virtual screening study aimed at the discovery of novel inhibitors targeting another oxidoreductase, superoxide dismutase, we identified four compounds with non-purine-like structures, namely ALS-1, -8, -15 and -28, that were capable of causing direct inhibition of XO. The kinetic studies of their inhibition mechanism allowed a definition of these compounds as competitive inhibitors of XO. The most potent molecule was ALS-28 (Ki 2.7 ± 1.5 µM), followed by ALS-8 (Ki 4.5 ± 1.5 µM) and by the less potent ALS-15 (Ki 23 ± 9 µM) and ALS-1 (Ki 41 ± 14 µM). Docking studies shed light on the molecular basis of the inhibitory activity of ALS-28, which hinders the enzyme cavity channel for substrate entry consistently with the competitive mechanism observed in kinetic studies. Moreover, the structural features emerging from the docked poses of ALS-8, -15 and -1 may explain the lower inhibition power with respect to ALS-28. All these structurally unrelated compounds represent valuable candidates for further elaboration into promising lead compounds.

A Dual-Function Wearable Electrochemical Sensor for Uric Acid and Glucose Sensing in Sweat

Simultaneous detection of uric acid and glucose using a non-invasive approach can be a promising strategy for related diseases, e.g., diabetes, gout, kidney disease, and cardiovascular disease. In this study, we have proposed a dual-function wearable electrochemical sensor for uric acid and glucose detection in sweat. The sensor with a four-electrode system was prepared by printing the ink on a common rubber glove. CV and chronoamperometry were used to characterize the prepared sensor's electrochemical sensing performance. The sensors exhibited the linear range from 0 to 1.6 mM and 0 to 3.7 mM towards uric acid and glucose electrochemical sensing in phosphate-buffered solution, with the corresponding limit of detection of 3.58 μM and 9.10 μM obtained, respectively. Moreover, the sensors had shown their feasibility of real sample sensing in sweat. The linear detection range for uric acid (0 to 40 μM) and glucose (0 to 1.6 mM) in the sweat can well cover their concentration range in physiological conditions. The prepared dual-function wearable electrochemical sensor features easy preparation, fast detection, high sensitivity, high selectivity, and the practical application potential in uric acid and glucose sensing.

Discovery of novel benzbromarone analogs with improved pharmacokinetics and benign toxicity profiles as antihyperuricemic agents

Benzbromarone (BM) is a potent URAT1 inhibitor approved for the treatment of gout. However, the low URAT1-selectivity and hepatotoxcity limit its clinical use. To solve these problems, we rationally designed and synthesized a series of BM derivatives by chemotype hybridization and bioisosteric replacement. Most compounds exhibited potent inhibitory activities against URAT1 with IC₅₀ values ranging from 5.83 μM to 0.80 μM. Among them, JNS4 exhibited the highest URAT1 inhibitory activity with an IC₅₀ of 0.80 μM, comparable to that of BM (IC₅₀ = 0.53 μM). Molecular dynamic simulations showed that JNS4 formed π-cation interaction with R477, the same as BM. Different from BM, JNS4 bound to W357 and H245 via π-π interactions and formed a hydrogen bond with S35, which might contribute to the high URAT1 binding affinity of JNS4. JNS4 hardly inhibited GLUT9 (IC₅₀ > 20 μM), another urate reabsorption transporter. In addition, JNS4 showed little inhibitory effects against OAT1 and ABCG2 with IC₅₀ of 4.04 μM and 10.16 μM, respectively. Importantly, JNS4 displayed higher in vivo urate-lowering effects at doses of 1-4 mg/kg in a mouse model of hyperuricemia, as compared to BM and lesinurad. Furthermore, JNS4 possessed favorable pharmacokinetic properties with an oral bioavailability of 55.28%, significantly higher than that of BM (36.11%). Moreover, JNS4 demonstrated benign toxicity profiles (no cytotoxicities against HepG2 and HK2 cells; no hepatic and renal toxicities observed in vivo). Collectively, these results suggest that JNS4 represents a novel, safe and selective URAT1 inhibitor with excellent druggabilities and is worthy of further investigation as an anti-hyperuricemic agent.

Serum uric acid levels and diabetic kidney disease in patients with type 2 diabetes mellitus: A dose-response meta-analysis

OBJECTIVE

Our study aimed to assess the existing evidence on whether serum uric acid (SUA) levels are associated with diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

We conducted a systematic search of articles up to October 2021 in Medline, Embase, The Cochrane Library and Web of Science that estimated DKD by SUA levels in patients with T2DM. Pooled relative risks with 95% CI were calculated using random effects models RESULTS: A total of eight cohort studies involving 25,741 T2DM patients were included. Meta-analysis showed that compared the highest with the lowest category of SUA level, the summary risk ratios were 2.04 (95%CI 1.43-2.92, P < 0.001). The linear dose-response analysis revealed that the risk of DKD increased by 24% for each 1 mg/dl increase of SUA. The non-linear dose-response analysis also showed a significant relevance between SUA and the risk of DKD in patients with type 2 diabetes mellitus (P < 0.001).

CONCLUSIONS

Serum uric acid is associated with an increased risk of diabetic kidney disease in patients with type 2 diabetes mellitus. Serum uric acid level could be a good indicator for predicting diabetic kidney disease in patients with type 2 diabetes mellitus.

Liquid crystal-based sensitive and selective detection of uric acid and uricase in body fluids

The abnormal levels of uric acid (UA) in body fluids are associated with gout, type (II) diabetes, leukemia, Lesch-Nyhan syndrome, uremia, kidney damage, and cardiovascular diseases. Also, the presence of uricase (UOx) symbolizes genetic disorders and corresponding complications. Therefore, the detection of UA and UOx in the body fluids is significant for clinical diagnosis. 4-Cyano-4'-pentylbiphenyl (5CB, a nematic liquid crystal (LC)) was doped with octadecyl trimethylammonium bromide (OTAB, a cationic surfactant), which formed a self-assembled monolayer at the aqueous/5CB interface. The UOx-catalyzed oxidation of UA yielded H₂O₂, releasing the single-strand deoxyribonucleic acid (ssDNA) from the nanoceria/ssDNA complex. The interaction of the released ssDNA with OTAB disrupted the monolayer at the aqueous/5CB interface, which resulted in a dark to bright change when observed through a polarized optical microscope. The LC-based sensor allowed the detection of UA with a linear range of 0.01-10 μM and a limit of detection (LOD) of 0.001 μM. The UA detection was also performed in human urine samples and the results were comparable to that of a standard commercial colorimetric method. Similarly, the detection of UOx was performed, with a noted linear range of 20-140 μg/mL. The LOD was as low as 0.34 μg/mL. The detection of UOx was also demonstrated in human serum samples with excellent performance. This method provides a robust sensing platform for the detection of UA and UOx and has potential for applications in clinical analysis.

Single-atom Nanozymes for Biomedical Applications： Recent Advances and Challenges

Nanozymes have received extensive attention in the fields of sensing and detection, medical therapy, industry, and agriculture thanks to the combination of the catalytic properties of natural enzymes and the physicochemical properties of nanomaterials, coupled with superior stability and ease of preparation. Despite the promise of nanozymes, conventional nanozymes are constrained by their oversized size and low catalytic capacity in sophisticated practical application environments. single-atom nanozymes (SAzymes) were characterized as nanozymes with high catalytic efficiency by uniformly distributed single atoms as catalysis sites, thus effectively addressing the defects of conventional nanozymes. This paper reviews the activity improvement scheme and catalytic mechanism of SAzymes and highlights the latest research progress of SAzymes in the fields of biomedical sensing and therapy. Eventually, the challenges and future directions of SAzymes are discussed in this paper.

Discovery of novel verinurad analogs as dual inhibitors of URAT1 and GLUT9 with improved Druggability for the treatment of hyperuricemia

Verinurad (RDEA3170) is a selective URAT1 inhibitor under investigation for the treatment of gout and hyperuricemia. In an effort to further improve the pharmacodynamics/pharmacokinetics of verinurad and to increase the structural diversity, we designed novel verinurad analogs by introducing a linker (e.g. aminomethyl, amino or oxygen) between the naphthalene and the pyridine ring to increase the flexibility. These compounds were synthesized and tested for their in vitro URAT1-inhibitory activity. Most compounds exhibited potent inhibitory activities against URAT1 with IC₅₀ values ranging from 0.24 μM to 16.35 μM. Among them, compound KPH2f exhibited the highest URAT1-inhibitory activity with IC₅₀ of 0.24 μM, comparable to that of verinurad (IC₅₀ = 0.17 μM). KPH2f also inhibited GLUT9 with an IC₅₀ value of 9.37 ± 7.10 μM, indicating the dual URAT1/GLUT9 targeting capability. In addition, KPH2f showed little effects on OAT1 and ABCG2, and thus was unlikely to cause OAT1/ABCG2-mediated drug-drug interactions and/or to neutralize the uricosuric effects of URAT1/GLUT9 inhibitors. Importantly, KPH2f (10 mg/kg) was equally effective in reducing serum uric acid levels and exhibited higher uricosuric effects in a mice hyperuricemia model, as compared to verinurad (10 mg/kg). Furthermore, KPH2f demonstrated favorable pharmacokinetic properties with an oral bioavailability of 30.13%, clearly better than that of verinurad (21.47%). Moreover, KPH2f presented benign safety profiles without causing hERG toxicity, cytotoxicity in vitro (lower than verinurad), and renal damage in vivo. Collectively, these results suggest that KPH2f represents a novel, safe and effective dual URAT1/GLUT9 inhibitor with improved druggabilities and is worthy of further investigation as an anti-hyperuricemic drug candidate.

High-level uric acid in asymptomatic hyperuricemia could be an isolated risk factor of cardio-cerebrovascular diseases: A prospective cohort study

BACKGROUND AND AIMS

Whether the asymptomatic hyperuricemia (AH) raise the cardiovascular disease risk with or without hyperuricemia-related comorbidities still remains contentious. Our study was aimed to quantitatively access the incidence risk of coronary heart disease (CHD) and stroke associated with AH.

METHODS AND RESULTS

In this prospective cohort study, multivariate-adjusted Cox regression models were applied to evaluate the risk of cardiovascular disease (CVD). Baseline serum uric acid beyond normouricemia (357 mmol/L) was quarterly stratified based on the distribution of healthy populations without CVD onset. 1062 CVD first-attack cases were collected among the 29,974 study population (age range: 18-91, mean age: 47.2 ± 13.9 years-old) with a mean follow-up duration of 5.78 ± 0.83 years. The AH showed overall non-association with the CVD incident. However, significantly increased adjusted hazard ratio (HR) of CVD with 95% confidence interval (CI) were observed when the fourth quartile compared with normouricemia stratum in the total cohort population (CHD: 1.42, 1.21-1.68; stroke: 1.27, 1.06-1.41), male (CHD: 1.26, 1.12-1.55), female (CHD: 1.34, 1.04-2.02; stroke: 2.06, 1.13-3.77) and aged over 50 years-old population. Meanwhile, the age-standardized incidence rate of CVD in the fourth quartile was 2-3 times higher than the normouricemia population. After excluded 14,464 baseline population with diabetes, dyslipidemia, and hypertension, consistent results were also observed in the AH population in absence of comorbidities (CHD: 1.51, 1.22-2.25; stroke: 1.68, 1.13-2.39).

CONCLUSION

Asymptomatic hyperuricemia patients exposed to a higher level of uric acid (>=428 mmol/L) could significantly increase the incidence risk of CHD and stroke, with or without hyperuricemia-related comorbidities.

Dietary Acid Load Is Positively Associated with the Incidence of Hyperuricemia in Middle-Aged and Older Korean Adults: Findings from the Korean Genome and Epidemiology Study

Hyperuricemia has been associated with a number of chronic diseases, such as type 2 diabetes mellitus, hypertension, and cardiovascular diseases. Dietary acid load plays a key role in regulating uric acid levels. We hypothesized that potential renal acid load (PRAL) and net endogenous acid production (NEAP) score would be positively associated with the incidence of hyperuricemia. Data from the Health Examinees study, a part of the Korean Genome and Epidemiology Study were used. The PRAL and NEAP scores were calculated to evaluate the dietary acid load. Hyperuricemia was defined as follows: >7.0 mg/dL and >6.0 mg/dL of serum uric acid levels in men and women, respectively. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of hyperuricemia. We identified 2500 new cases of hyperuricemia during a mean follow-up of 5.0 years (223,552 person years). The participants in the highest quartiles of the PRAL and NEAP score had 21% (HR: 1.21, 95% CI: 1.07–1.35, p for trend <0.0001) and 17% (HR: 1.17, 95% CI: 1.04–1.31, p for trend <0.0001) higher risks for hyperuricemia, respectively, than those in the lowest quartiles, after adjusting for covariates. In this prospective cohort study, a higher dietary acid load was positively associated with a higher incidence of hyperuricemia in Korean adults. This suggests that an alkaline diet may be an effective strategy to reduce the future risk of elevated uric acid levels.

Association of urate-lowering drugs with the risk of future urolithiasis in patients with gout: A population-based nested case-control study

BACKGROUND

Patients with gout have an increased risk of urolithiasis and usually need urate-lowering therapy (ULT) for the prevention of disease progression. However, there is a paucity of clinical data regarding the risk of future urolithiasis in ULT users.

METHODS

This nested case-control study was performed using the Taiwan National Health Insurance Research Database. The aim of this study was to examine whether ULT (xanthine oxidase inhibitors [XOIs] or uricosuric agents) is associated with risk of future urolithiasis in patients with gout. Data were collected from January 2000 to December 2012.

RESULTS

This study included 2307 case patients and 2307 matched controls. Case patients had gout that developed into urolithiasis, and control patients had gout but were not diagnosed with urolithiasis during the study period. Patients had a mean age of 56.3 years at diagnosis of gout, and 83.2% were male patients. No association was detected between use of XOIs or uricosuric agents and risk of future urolithiasis. Furthermore, there was no significant difference in the risk of future urolithiasis in patients exposed to various cumulative days of XOI or uricosuric prescriptions.

CONCLUSION

The present study provides evidence that neither XOIs nor uricosuric agents are associated with risk of future urolithiasis in patients with gout. Before the availability of more clinical evidence, ensuring high fluid intake and prospective monitoring of urolithiasis development are still important for uricosuric agent users.

Differentially expressed microRNA in testicular tissues of hyperuricaemia rats

This study is to identify the differentially expressed miRNAs in testicular tissues of rats with hyperuricaemia-induced male infertility. We found that the hyperuricaemia model group had significantly increased serum uric acid, while significantly decreased sperm concentration and motile sperm percentage than normal group (p < .05). A total of 39 differentially expressed miRNAs were identified in the testicular tissues of hyperuricaemia rats compared with the control rats, ten of which were validated by real-time PCR. The target mRNAs of 7 differentially expressed miRNAs (miR-10b-5p, miR-26a-5p, miR-136-5p, miR-151-3p, miR-183-5p, miR-362-3p and miR-509-5p) from 3'-untranslated region binding perspective were enriched in signalling pathways of Wnt, Jak-STAT, mTOR and MAPK. The target mRNAs of 6 differentially expressed miRNAs (miR-136-5p, miR-144-3p, miR-99a-5p, miR-509-5p, miR-451-5p and miR-362-3p) from coding sequence binding perspective were enriched in signalling pathways of Calcium, Notch and MAPK. The functions of miRNAs in testicular tissues of rats with hyperuricaemia were revealed by the differentially expressed miRNAs (miR-183-5p, miR-99a-5p, miR-10b-5p, miR-151-3p, miR-26a-5p, miR-451-5p, miR-362-3p, miR-136-5p, miR-144-3p and miR-509-5p)-mRNAs interaction network. The differentially expressed miRNAs in the testicular tissues of hyperuricaemia rats might shed light on the mechanism of hyperuricaemia-induced male infertility.

Urate-lowering Therapy and Chronic Kidney Disease Development in Patients with Gout

Objectives: Chronic kidney disease (CKD) has emerged as a global health concern. Many studies have identified an association between hyperuricemia and CKD, and some studies have revealed that urate-lowering therapy (ULT) can attenuate CKD progression. However, only a few studies have explored the role of ULT in the prevention of new onset CKD. Methods: To compare the risk of incident CKD between users and nonusers of ULT in patients with gout, we conducted a 13-year population-based retrospective cohort study. Overall incidence of CKD was compared between 7126 ULT users and 7126 matched ULT nonusers. Results: The CKD incidence rate for both the users and nonusers of ULT was 1.7 per 100 person-years, after adjusting for sex, age, region of residence, comorbidities, and medications used. No significant difference in CKD risk (adjusted hazard ratio [aHR]: 0.97; 95% confidence interval [CI]: 0.88-1.07) was noted between the ULT users and nonusers. In the subgroup of patients with diabetes mellitus (DM) and without hypertension (HT), ULT tended to be associated with lower risk of incident CKD (aHR: 0.52; 0.95% CI: 0.28-0.97). Compared with the risk of new onset CKD in patients receiving xanthine oxidase inhibitors, those receiving uricosuric agents seemed to have a lower risk of developing CKD (aHR: 0.81, 95% CI: 0.67-0.99). Conclusion: This population-based cohort study indicated that ULT is not associated with lower risk of CKD development. However, in the subgroup of patients with DM and without HT, ULT is associated with significantly lower risk of incident CKD.

Cardiovascular events in hyperuricemia population and a cardiovascular benefit-risk assessment of urate-lowering therapies: a systematic review and meta-analysis

BACKGROUND

Hyperuricemia and gout have become public health concerns; many important guidelines have recommended xanthine oxidase inhibitors (XOIs) as the first-line urate-lowering therapies (ULTs) to treat chronic gout with hyperuricemia. However, whether treating hyperuricemia and gout with ULTs modifies cardiovascular risks remains controversial. The aim of this study was to assess the incident risk of cardiovascular (CV) events (CVE) in hyperuricemia population, assess the cardiovascular benefit-risk of ULTs in hyperuricemia patients with or without gout in diverse cardiovascular risk sub-groups, and specify the safety of different ULTs.

METHODS

We searched PubMed, Embase, the Cochrane Library, Wanfang, Chongqing VIP (CQVIP, en.cqvip.com), and China National Knowledge Infrastructure Database for prospective cohort studies and randomized controlled trials (RCTs) in English and Chinese. Potential medications included XOIs, and uricosurics. RCTs were divided into sub-groups analysis based on blinding status and patients' history of CV diseases. Risk ratios (RRs) were calculated and were reported with corresponding 95% confidence intervals (CIs) by fixed-effects or random-effects model.

RESULTS

Seven prospective cohort studies and 17 RCT studies were included. The risks of both major adverse cardiovascular events (MACE) (RR = 1.72, 95% CI 1.28-2.33) and CVE (RR = 1.35, 95% CI 1.12-1.62) were higher in the hyperuricemia population than non-hyperuricemia one. In seven RCT studies where XOIs were compared with no-treatment or placebo, the results of five low CV risk studies showed that XOIs lowered the risks of both MACE (RR = 0.35, 95% CI 0.20-0.62) and CVE (RR = 0.61, 95% CI 0.44-0.85); whereas two high CV risk studies showed that XOIs lowered the risk of CVE (RR = 0.69, 95% CI 0.54-0.88) rather than MACE (RR = 0.62, 95% CI 0.29-1.35). In nine RCT studies where the cardiovascular safety between febuxostat and allopurinol were compared, no statistical difference was found in the risk of MACE or CVE.

CONCLUSIONS

The hyperuricemia population does have a higher incidence of CVE, and the results suggested that XOIs might reduce the incidence of MACE and total CVE. In addition, from the perspective of cardiovascular safety, febuxostat equaled allopurinol in our meta-analysis.

Plasma and water fluoride levels and hyperuricemia among adolescents: A cross-sectional study of a nationally representative sample of the United States for 2013-2016

Exposure to excessive fluoride has been associated with a number of adverse health outcomes; however, there is a lack of evidence on the relation between fluoride exposure and serum uric acid levels, especially in human populations. The present study examined a potential relationship between fluoride exposure, measured as both plasma and water fluoride concentrations, and uric acid levels in an adolescent population. A nationally representative subsample of 1933 adolescents, aged 12-19 years, in the 2013-2016 National Health and Nutrition Examination Survey was analyzed for the association of fluoride concentrations with serum uric acid levels using multivariate general linear and logistic regression models, adjusting for potential confounders. Since uric acid levels change during development, hyperuricemia was defined in this study as over the mean plus one standard deviation for each sex and age group of adolescents. Of the study participants, 276 adolescents (weighted prevalence, 16.56%) had hyperuricemia. A significant and dose-dependent increase in prevalence of hyperuricemia was seen among the participants cross increasing quartiles of plasma fluoride (p-trend = 0.0017). After adjusting for potential confounders, we found that adolescents in the higher quartiles of plasma fluoride (≥0.32 µmol/L) and in the highest quartile of water fluoride (≥0.73 mg/L) had significantly increased odds of hyperuricemia compared with those in the lowest quartile. A 1.95-fold increased odds (95% CI: 1.37, 2.77) of hyperuricemia was also observed when analyzing plasma fluoride concentrations as continuous variable. A general linear model revealed that a 1 µmol/L increase in ln-plasma fluoride was associated with a 0.212 mg/dL (p < 0.0001) increased serum uric acid level. Furthermore, a positive relationship was observed between water and plasma fluoride concentrations (β = 0.1907; p < 0.0001). Our study demonstrates a potential relation between fluoride exposure and hyperuricemia in adolescents. Further studies are warranted to overcome the limitations of this study to examine the impact of long-term exposure to low levels of fluoride during development on hyperuricemia and its related health outcomes.

A new uricase from Bacillus cereus SKIII: Characterization, gene identification and genetic improvement

Twenty-five microbial isolates were investigated for uricase production on uric acid medium. All isolates were obtained from Jeddah, Saudi Arabia. The highest uricase producer was identified as Bacillus cereus SKIII. Using glucose peptone broth at pH 7.5, incubation temperature 30 °C for 3 days with shaking of 150 rpm were the best conditions for maximum enzyme production. Glucose and peptone were the best carbon and nitrogen sources. The molecular weight of the purified enzyme was34.5 KDa, and isoelectric point was 7.9. The optimum pH and temperature were pH 8.0 and 35 °C, respectively. It was stable at 35 °C for 60 min, but thermally inactivated at 60 °C after 60 min Its enzymatic activity was enhanced by Mg²⁺, Ca²⁺,Fe²⁺, Mn^2+, Zn²⁺ions and inhibited by Co²⁺, Na⁺, Hg²⁺, Ag⁺ ions and EDTA at 1 mM. Uricase production was enhanced using UV mutation and the obtained mutant produced six times higher than the original isolate. An amplicon 900 bp of uricase gene (Pucl) was sequenced (accession number MF417635). No remarkable difference was noticed in B. cereus SKIII and SKm mutant nucleotide sequences. In conclusion, SKIII and SKm are promising strains in uricase production for biotechnological applications.

Single-Atom Cobalt-Based Electrochemical Biomimetic Uric Acid Sensor with Wide Linear Range and Ultralow Detection Limit

Uric acid (UA) detection is essential in diagnosis of arthritis, preeclampsia, renal disorder, and cardiovascular diseases, but it is very challenging to realize the required wide detection range and low detection limit. We present here a single-atom catalyst consisting of Co^(II) atoms coordinated by an average of 3.4 N atoms on an N-doped graphene matrix (A-Co-NG) to build an electrochemical biomimetic sensor for UA detection. The A-Co-NG sensor achieves a wide detection range over 0.4-41,950 μM and an extremely low detection limit of 33.3 ± 0.024 nM, which are much better than previously reported sensors based on various nanostructured materials. Besides, the A-Co-NG sensor also demonstrates its accurate serum diagnosis for UA for its practical application. Combination of experimental and theoretical calculation discovers that the catalytic process of the A-Co-NG toward UA starts from the oxidation of Co species to form a Co³⁺-OH-UA*, followed by the generation of Co³⁺-OH + ^*UA_H, eventually leading to N-H bond dissociation for the formation of oxidized UA molecule and reduction of oxidized Co³⁺ to Co²⁺ for the regenerated A-Co-NG. This work provides a promising material to realize UA detection with wide detection range and low detection limit to meet the practical diagnosis requirements, and the proposed sensing mechanism sheds light on fundamental insights for guiding exploration of other biosensing processes.

Xanthine oxidase inhibitory activity of a new isocoumarin obtained from Marantodes pumilum var. pumila leaves

BACKGROUND

In traditional Malay medicine, Marantodes pumilum (Blume) Kuntze (family Primulaceae) is commonly used by women to treat parturition, flatulence, dysentery, dysmenorrhea, gonorrhea, and bone diseases. Preliminary screening of some Primulaceae species showed that they possess xanthine oxidase inhibitory activity. Thus, this study aimed to investigate the xanthine oxidase inhibitory activity of three varieties of M. pumilum and their phytochemical compounds.

METHOD

Dichloromethane, methanol, and water extracts of the leaves and roots of M. pumilum var. alata, M. pumilum var. pumila, and M. pumilum var. lanceolata were tested using an in vitro xanthine oxidase inhibitory assay. Bioassay-guided fractionation and isolation were carried out on the most active extract using chromatographic techniques. The structures of the isolated compounds were determined using spectroscopic techniques.

RESULTS

The most active dichloromethane extract of M. pumilum var. pumila leaves (IC50 = 161.6 μg/mL) yielded one new compound, 3,7-dihydroxy-5-methoxy-4,8-dimethyl-isocoumarin (1), and five known compounds, viz. ardisiaquinone A (2), maesanin (3), stigmasterol (4), tetracosane (5), and margaric acid (6). The new compound was found to be the most active xanthine oxidase inhibitor with an IC50 value of 0.66 ± 0.01 μg/mL, which was not significantly different (p > 0.05) from that of the positive control, allopurinol (IC50 = 0.24 ± 0.00 μg/mL).

CONCLUSION

This study suggests that the new compound 3,7-dihydroxy-5-methoxy-4,8-dimethyl-isocoumarin (1), which was isolated from the dichloromethane extract of M. pumilum var. pumila leaves, could be a potential xanthine oxidase inhibitor.

Assessment of the efficacy of hemodialysis on uric acid clearance in a sub-Saharan African population at the end stage kidney disease

Background

Uricemia dramatically rises with the stage of chronic kidney disease (CKD) and correlates with its mortality. Hemodialysis (HD) being the most used treatment at the end stage in sub-Saharan Africa, we sought to evaluate its efficacy on the clearance of uric acid (UAc) when used alone and twice per week.

Methods

A cross-sectional study of all consenting patients with CKD stage 5 recruited at random during HD sessions in a reference Centre in Cameroon from January to April 2017. We collected socio-demographic data, relevant clinical information, HD related variables, and measured serum uric acid (SUA) levels before and after the dialysis to assess the uric acid clearance. A clearance between 65 and 80% and above 80% was considered as low and good efficacy of HD respectively. Statistical analysis was performed using SPSS version 21.0. Factors associated with HD efficacy were assessed using Fisher’s exact test and are presented with their odds ratios (OR) and 95% confidence levels.

Results

One hundred four patients (53 females) were included. The mean age was 49.9 ± 13.3 years. Hypertension (25%) and chronic glomerulonephritis (16%) were the main suspected etiologies of CKD. The median time on renal replacement therapy by HD was 3 years [1; 6]. The prevalence of hyperuricemia was 81.9%. The means of SUA levels were 78.8 ± 13.8 mg/L and 26.4 ± 6.6 mg/L respectively before and after dialysis. Mean SUA clearance was 66% ± 10%. The efficacy of HD on UAc was moderate in 92 (63.9%) and good in 2 (1.4%) patients. Excess weight (OR 0.4 [0.2; 0.9]) and Kt/Vurea < 1.2 (OR 0.1 [0.04; 0.2]) significantly reduces the efficacy of HD.

Conclusion

HD used alone for 2 sessions per week has a moderate efficacy on uric acid clearance in CKD. Therefore, we should improve the Kt/V (> 1.2), and combine HD to uric acid lowering drugs and diet modifications to increase its efficacy.

A Europium-based MOF Fluorescent Probe for Efficiently Detecting Malachite Green and Uric Acid

Lanthanide (such as Tb and Eu) metal-organic frameworks (MOFs) have been widely used in fluorescent probes because of their multiple coordination modes and brilliant fluorescence characteristic. Many lanthanide MOFs were applied in detecting metal ions, inorganic anions, and small molecules. However, it's rarely reported that Ln-MOF was devoted to detecting malachite green (MG) and uric acid (UA). We prepared a europium-based metal-organic framework (Eu-TDA) (TDA = 2,5-thiophenedicarboxylic acid group). Luminescence studies demonstrated that Eu-TDA can rapidly detect MG and UA with excellent selectivity and sensitivity, where individual quenching efficiency K_sv (MG: 5.8 × 10⁵ M^-1; UA: 4.15 × 10⁴ M^-1) and detection limit (MG: 0.0221 μM; UA: 0.689 μM) were regarded as the excellent MOF sensors for detecting MG and UA. The quenching of Eu-TDA's fluorescence emission by MG and UA was likely due to the spectral overlap, energy transfer, and competition. Among 11 metal cations and 14 anions, Eu-TDA can quickly and effectively recognize MG and UA with highly selective and sensitive properties. Our method possesses potential application in detecting UA in human blood and MG in the fishpond.

Purine-blended nanofiber woven flexible nanomats for SERS-based analyte detection

We report a fabricated nanocomposite as a flexible Surface-Enhanced Raman Scattering (SERS) substrate for uric acid detection up to 10⁻⁷ M (100 nM).

Molecular mechanistic insight into the anti-hyperuricemic effect of Eucommia ulmoides in mice and rats

CONTEXT

Eucommia ulmoides Oliver (Eucommiaceae) has various medicinal properties. Our previous studies revealed that Eucommia ulmoides has a protective effect on hyperuricaemia.

OBJECTIVE

This study investigates the effect of Eucommia ulmoides cortex ethanol extract (EU) on hyperuricaemia and explores the underlying mechanism in Kunming mice and Sprague-Dawley rats.

MATERIAL AND METHODS

Sixty mice and sixty rats were divided into normal control, hyperuricaemia, allopurinol (10 mg/kg) and three EU groups. The EU groups received intragastric EU at 80, 160, 320 mg/kg in mice and 100, 200, 400 mg/kg in rats for 7 days. Serum uric acid (SUA) was measured using a kit. mRNA and proteins were quantified by RT-qPCR and immunohistochemical assays (IHC), respectively.

RESULTS

The Maximal Tolerable Dose (MTD) of EU administered intragastrically was 18 g/kg in mice. The intermediate (160 mg/kg) and high (320 mg/kg) EU treatment significantly reduced (p < 0.05) SUA levels to 130.16 μmol/L and 109.29 μmol/L, respectively, and markedly elevated the mRNA expression of organic anion transporters 1 (OAT1) and organic anion transporters 3 (OAT3), while significantly deceasing the mRNA levels of glucose transporter 9 (GLUT9) and uric acid transporter 1 (URAT1) in the mouse kidney (p < 0.05). In hyperuricemic rats, high EU (400 mg/kg) significantly reduced SUA levels to 253.85 μmol/L, and increased OAT1 and OAT3 levels, but decreased URAT1 and GLUT9, compared to the hyperuricaemia group (p < 0.05).

DISCUSSION AND CONCLUSIONS

This study demonstrated the potential hyperuricaemia ameliorating effect of EU. Specific active ingredients in EU should be evaluated. These results are valuable for the development of antihyperuritic agents from EU.

Potential of a sensitive uric acid biosensor fabricated using hydroxyapatite nanowire/reduced graphene oxide/gold nanoparticle

In this study, a ternary nanocomposite consisting of gold nanoparticles (AuNPs), hydroxyapatite (HAP) nanowires, and reduced graphene oxide (rGO) is synthesized by a simple one-step hydrothermal method, which is used to modify glassy carbon electrode (GCE) for detecting uric acid. The nanocomposite is characterized through various methods such as scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Electrochemical measurements of the modified GCE are performed in a conventional three-electrode system. Experimental results show that the obtained HAP nanowire and rGO are mixed homogeneously, and the AuNPs are deposited into this matrix. The GCE modified by the nanocomposites have superior electrocatalytic activities for uric acid. The peak current intensities of UAO (uricase)/HAP-rGO/AuNPs sensing system linearly increase as the uric acid concentration increases substantially in a range of 1.95 × 10^-5 to 6.0 × 10^-3  M (R² = .9943), with a detection limit of 3.9 × 10^-6  M (S/N = 3) and analytical sensitivity of 13.86 mA/M. The biosensor performs well in determining uric acid concentration in human urine samples.

Serum Uric Acid - Risk Factor for Acute Ischemic Stroke and Poor Outcomes

Over the last decades several studies among the adult population have attempted to establish a correlation between the risk of stroke incidence and serum uric acid (SUA) concentration, and how these levels influence the patient’s neurological outcome after a stroke. But, to date, the results are conflicting. In this review, an extensive literature search was performed through PubMed for articles published until May 2019 to review the association. The study selection was narrowed by searching PubMed database using the Medical Subject Headings (MesH) and associated keywords. Only articles conducted in English and on human subjects were included. We considered an article for this review if it had statistics on either the incidence, stroke mortality or post-stroke functional outcomes along with serum uric acid levels in adults.

This review includes 21 articles with data of 33,580 cases of stroke and 1,100,888 participants. We can divide the articles reviewed into two separate cohorts of studies. One relates serum uric acid levels to stroke frequency and mortality, while the other is associated with serum uric acid and outcomes for stroke survivors. Based on our review, no significant relationship is observed with uric acid exhibiting protective effects on stroke outcome. Large clinical trials are advised to provide well-defined solutions to further assess the benefits of uric acid level lowering treatment in patients of vascular events, such as a stroke. However, we confidently report that increasing uric acid levels poses a higher risk for incidence of stroke.

Effect of Muntingia calabura L. Stem Bark Extracts on Uric Acid Concentration and Renal Histopathology in Diabetic Rats

Background and objectives: This study was designed to determine uric acid concentration and renal histopathology of Muntingia calabura L. stem bark extract in diabetic rats and to compare the natural product of M. calabura L. stem bark extract with allopurinol. Materials and Methods: A completely randomized design was used for the experiment, which consisted of six treatment groups, each consisting of four rats, as follows: 1) NR, normal rat; 2) KN, diabetic rat (negative control); 3) KP, diabetic rats given allopurinol 10 mg/kg body weight; 4) EM150, diabetic rats given the test extract 150 mg/kg body weight/day; 5) EM300, diabetic rats given the test extract 300 mg/kg body weight/day; and 6) EM450, diabetic rats given for extract 450 mg/kg body weight/ day. Results: The results showed that M. calabura L. stem bark extract decreased (p < 0.05) uric acid concentrations in diabetic rats and no specific damage to renal proximal tubular cells was seen. Conclusions: It was concluded that M. calabura L. stem bark extract has a potential as an antihyperuricemic in diabetic rats. The recommended dose was 300 mg/kg body weight to provide a significant effect on reducing the uric acid level in diabetic rats. Our results support the use of this plant for the treatment of degenerative and inflammatory diseases.

White blood cell count: an independent predictor of coronary heart disease risk in middle-aged and elderly population with hyperuricemia

Previous studies have shown that hyperuricemia is an independent risk factor for cardiovascular disease. The aim of the study was to examine the association between white blood cell (WBC) count and coronary heart disease (CHD) risk in middle-aged and elderly population with hyperuricemia.Data included in this analysis were from a population-based cross-sectional study, that is, the Xiangya Hospital Health Management Center Study. Hyperuricemia was defined as uric acid ≥416 μmol/L in male population and ≥360 μmol/L in female population. The WBC count was classified into 3 categories based on the tertile distribution of the study population. Framingham risk scores calculated by the Adult Treatment Panel III charts were used to estimate 10-year CHD risk for each participant. The relationship between WBC count and CHD risk in patients with hyperuricemia was examined using the multivariable logistic analysis.A total of 1148 hyperuricemia patients (855 males and 293 females) aged from 40 to 85 years were included and 418 (36.4%) of them were defined with relatively high 10-year CHD risk. Compared with the lowest tertile, the crude odds ratios (ORs) of high 10-year CHD risk were 1.43 (95% confidence interval [CI] 1.06-1.92) and 1.56 (95% CI 1.16-2.11) in the 2nd and 3rd tertiles of WBC count (P for trend = .004), and the multivariable adjusted ORs of high 10-year CHD risk were 1.39 (95% CI 1.03-1.89) and 1.47 (95% CI 1.08-2.00) in the 2nd and 3rd tertiles of WBC count (P for trend = .015).This study indicated that WBC count was associated with CHD risk in patients with hyperuricemia, suggesting that WBC count, an easily accessible biomarker, could probably predict CHD risk in middle-aged and elderly population with hyperuricemia.

Uric acid and incident chronic kidney disease in dyslipidemic individuals

BACKGROUND

Elevated uric acid (UA) is a recognized risk factor for chronic kidney disease (CKD). This study aimed to investigate whether this association exists in dyslipidemic patients receiving multifactorial treatment.

METHODS

An observational study conducted in Greece including 1,269 dyslipidemic individuals followed-up in a lipid clinic for ≥3 years. Estimated glomerular filtration rate (eGFR) was calculated by CKD-EPI equation and CKD was defined as ≤60 mL/min/1.73 m². The correlation was assessed between UA levels and the CKD risk after adjusting for potential confounding factors, after defining the following UA quartiles: Q1: < 4, Q2: 4-5, Q3: 5-6, and Q4: > 6 mg/dL.

RESULTS

After excluding patients with baseline eGFR <60 mL/min/1.73 m², gout and those taking UA-lowering drugs, 1,095 individuals were eligible; of those, 91% and 69% were treated with statins and anti-hypertensive drugs, respectively. During their follow-up (6 years; IQR = 4-10), 11.9% of the subjects developed CKD, whereas the median annual eGFR decline was 0.69 mL/min/1.73 m² (IQR = 0.45-2.33). Multivariate analysis showed that baseline UA levels (HR = 1.26; 95% CI = 1.09-1.45, p = .001), female gender (HR = 1.74; 95% CI = 1.14-2.65, p = .01), age (HR = 1.10; 95% CI = 1.07-1.12, p < .001), diabetes (HR = 1.67; 95% CI = 1.05-2.65, p = .03), cardiovascular disease (HR = 1.62; 95% CI = 1.02-2.58, p = .04), decreased baseline renal function (eGFR <90 mL/min/1.73 m²) (HR = 2.38; 95% CI = 1.14-4.81, p = .02), and low-density lipoprotein cholesterol reduction (HR = 0.995; 95% CI = 0.991-0.998, p = .01) were associated with incident CKD. Additionally, patients with UA ≥6 mg/dL exhibited a higher risk of incident CKD compared with those in the lowest UA quartile (HR = 2.01; 95% CI = 1.11-3.65, p = .02).

CONCLUSION

Higher UA levels are correlated with a higher risk of incident CKD in dyslipidemic individuals taking multifactorial treatment.

Structure-activity relationships of fraxamoside as an unusual xanthine oxidase inhibitor

Fraxamoside, a macrocyclic secoiridoid glucoside featuring a hydroxytyrosol group, was recently identified as a xanthine oxidase inhibitor (XOI) comparable in potency in vitro to the standard antigout drug allopurinol. However, this activity and its considerably higher value than its derivatives oleuropein, oleoside 11-methyl ester, and hydroxytyrosol are not explained by structure-activity relationships (SARs) of known XOIs. To exclude allosteric mechanisms, we first determined the inhibition kinetic of fraxamoside. The resulting competitive mechanism prompted a computational SAR characterization, combining molecular docking and dynamics, which fully explained the behavior of fraxamoside and its derivatives, attributed the higher activity of the former to conformational properties of its macrocycle, and showed a substantial contribution of the glycosidic moiety to binding, in striking contrast with glycoside derivatives of most other XOIs. Overall, fraxamoside emerged as a lead compound for a new class of XOIs potentially characterized by reduced interference with purine metabolism.

Effect of Febuxostat on Ambulatory Blood Pressure in Subjects With Hyperuricemia and Hypertension: A Phase 2 Randomized Placebo-Controlled Study

Background

Hyperuricemia is associated with hypertension, with elevated serum uric acid levels postulated to have a causal role in the development of hypertension. Consequently, serum uric acid reduction may help lower blood pressure (BP). A Phase 2, double‐blind, placebo‐controlled trial was conducted to assess the potential BP‐lowering effects of the xanthine oxidase inhibitor febuxostat in subjects with hypertension and hyperuricemia (serum uric acid ≥0.42 mmol/L [≥7.0 mg/dL]).

Methods and Results

Subjects (n=121) were randomized 1:1 to febuxostat 80 mg once daily or to placebo. The primary end point was change from baseline to Week 6 in 24‐hour mean ambulatory systolic BP (SBP). Additional end points included the following: change from baseline to Week 3 in 24‐hour mean SBP and changes from baseline to Weeks 3 and 6 in 24‐hour mean ambulatory diastolic BP, serum uric acid, mean daytime and nighttime ambulatory SBP/diastolic BP, and clinic SBP/diastolic BP. For the overall study population, there were no significant differences between febuxostat and placebo for changes from baseline to Weeks 3 or 6 in ambulatory, daytime or nighttime, or clinic SBP or diastolic BP. However, in a preplanned subgroup analysis, there was a significant decrease in SBP from baseline to Week 6 in subjects with normal renal function (estimated glomerular filtration rate ≥90 mL/min) treated with febuxostat versus placebo; least squares mean difference, −6.7; 95% confidence interval −13.3 to −0.0; P=0.049.

Conclusions

This study suggests that febuxostat may lower BP in hyperuricemic patients with hypertension and normal renal function; further studies should be conducted to confirm this finding.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01496469.

Asymptomatic hyperuricemia: is it time to intervene?

Whether to treat hyperuricemia uncomplicated by articular gout, urolithiasis, or uric acid nephropathy is an exercise in clinical judgment and universal agreement is lacking. Patients with coronary artery disease, chronic kidney disease, and early onset hypertension with persistent hyperuricemia are likely to be benefited with urate-lowering therapy. The paradigm of the causative association of hyperuricemia with cardiovascular and chronic kidney diseases seems to have progressed from skepticism to increasing evidence of a true relationship. Although such evidences are mounting, they are not enough to support pharmacotherapy for all patients with asymptomatic hyperuricemia. Further studies are needed to determine which patients are likely to get beneficial effects from pharmacotherapy and the minimum threshold of uric acid level required to experience clinical benefits.

Nanomolar Level Detection of Uric Acid in Blood Serum and Pest-Infested Grain Samples by an Amphiphilic Probe

A pyrene based amphiphilic receptor has been utilized in the nanomolar detection of uric acid at physiological pH in water. The compound shows a unique concentration-dependent modulation in optical response toward uric acid. In intramolecular/static excimer form (low concentration range), it displays a ratiometric response, while a "turn-off" sensing is observed specifically in the presence of intermolecular/dynamic excimer (high concentration range). The present protocol is then employed for the estimation of uric acid in blood serum samples of healthy individuals. Bland-Altman analysis in comparison to clinically approved uricase assay indicated the high accuracy of the present method. Additionally, the extent of insect infestation in stored grain samples was determined by measuring the uric acid content of their aqueous extracts. Low-cost color strips were developed for on-site detection of uric acid without involving any sophisticated instrument or trained personnel.

Camellia sinensis in asymptomatic hyperuricemia: A meta-analysis of tea or tea extract effects on uric acid levels

Flavanols of Camellia sinensis exhibit uric acid (UA) lowering effect, through the modulation of both xanthine oxidase and urate excretion. In order to investigate the potential benefit of Camellia Sinenis products in asymptomatic hyperuricemia, a meta-analysis of long-term Randomized Controlled Trials (RCT) with tea or tea extract has been conducted. From 20 human intervention studies selected only 5 RCT (13 interventions) were suitable for meta-analysis (n = 472). The current "normal" range set for hyperuricemia fails to identify patients with potential metabolic disorders. Therefore on the basis of the literature data, we fixed cut-off limits for UA baseline levels of 4.5 mg/dl for women, 6.1 mg/dl for men, and 5.5 mg/dl for studies involving mixed populations. Statistically significant effects were not found, but subgroup analysis revealed that the Pooled Estimate effect was different in subjects with baseline levels under [MD (95% CI): 0.1078 (-0.0528 to 0.2684)] and over the cut-off [MD (95% CI): -0.0239 (0.3311 to 0.2833)]. However, due to the low number of RCT and to the lack of data on bioavailability, it is difficult to draw any firm conclusion and more studies are needed to establish if tea flavanols could be useful in asymptomatic hyperuricemia treatment.

Uric Acid Induces Endothelial Dysfunction by Activating the HMGB1/RAGE Signaling Pathway

Uric acid (UA) is a risk factor for endothelial dysfunction, a process in which inflammation may play an important role. UA increases high mobility group box chromosomal protein 1 (HMGB1) expression and extracellular release in endothelial cells. HMGB1 is an inflammatory cytokine that interacts with the receptor for advanced glycation end products (RAGE), inducing an oxidative stress and inflammatory response, which leads to endothelial dysfunction. In this study, human umbilical vein endothelial cells (HUVECs) were incubated with a high concentration of UA (20 mg/dL) after which endothelial function and the expression of HMGB1, RAGE, nuclear factor kappa B (NF-κB), inflammatory cytokines, and adhesion molecules were evaluated. UA inhibited endothelial nitric oxide synthase (eNOS) expression and nitric oxide (NO) production in HUVECs, increased intracellular HMGB1 expression and extracellular HMGB1 secretion, and upregulated RAGE expression. UA also activated NF-κB and increased the level of inflammatory cytokines. Blocking RAGE significantly suppressed the upregulation of RAGE and HMGB1 and prevented the increase in DNA binding activity of NF-κB and the levels of inflammatory cytokines. It also blocked the decrease in eNOS expression and NO production induced by UA. Our results suggest that high concentrations of UA cause endothelial dysfunction via the HMGB1/RAGE signaling pathway.