Update on Uric Acid and the Kidney

Xanthine oxidase driven bio-Fenton system for advanced pollutant degradation in sustainable wastewater treatment

Advanced oxidation processes such as the Fenton reaction are critical for degrading recalcitrant pollutants in wastewater but face operational bottlenecks. The classical Fenton process relies on hazardous exogenous H₂O₂, inefficient Fe2+/Fe3+ cycling, and stringent acidic pH, limiting scalability. To address these limitations, this study introduces a sustainable hybrid system integrating human xanthine oxidase (Hu-XO) with Fenton chemistry, enabling self-sufficient H₂O₂ generation, Fe redox cycling, and pH modulation. The Hu-XO-driven hypoxanthine/xanthine oxidation produced H₂O₂ and superoxide radicals, synergizing with Fe2+ to amplify hydroxyl radical generation. When optimized via response surface methodology (95 % model accuracy), the system achieved 91.8 % biochemical oxygen demand (BOD) and 86.0 % chemical oxygen demand (COD) reduction in tannery wastewater. The antimicrobial assay using Escherichia coli and Bacillus subtilis demonstrated a removal rate of up to 106 CFU/mL. Posttreatment toxicity assays revealed an 80 % decrease in Aliivibrio fischeri luminescence inhibition and restored seed germination rates for Vigna mungo, Vigna radiata, and Cicer arietinum. This work establishes a self-sustaining Fenton-based system that eliminates exogenous H₂O₂ dependence and strict pH requirements and integrates pollutant degradation with antimicrobial action, offering a scalable, eco-friendly strategy for industrial wastewater remediation.

Unraveling the impact of miRNAs on gouty arthritis: diagnostic significance and therapeutic opportunities

Gouty arthritis is a prevalent inflammatory illness. Gout attacks begin when there is an imbalance in the body's uric acid metabolism, which leads to urate buildup and the development of the ailment. A family of conserved, short non-coding RNAs known as microRNAs (miRNAs) can regulate post-transcriptional protein synthesis by attaching to the 3' untranslated region (UTR) of messenger RNA (mRNA). An increasing amount of research is pointing to miRNAs as potential players in several inflammatory diseases, including gouty arthritis. miRNAs may influence the progression of the disease by regulating immune function and inflammatory responses. This review mainly focused on miRNAs and how they contribute to gouty arthritis. It also looked at how miRNAs could be used as diagnostic, prognostic, and potential therapeutic targets.

Transcriptomic and Metabolomic Analysis Reveals the Impact of Autophagy Regulation on Purine Content in Mutton

BACKGROUND

Excessive purine intake increases the risk of hyperuricemia and gout. This study investigates the relationship between purine content in mutton and meat quality traits and explores the regulatory mechanism of purine metabolism through transcriptomic and metabolomic analyses.

METHODS

Thirty-six-month-old hybrid sheep (Australian White × Small-tail Han) were selected. Purine content and meat quality traits, including inosine monophosphate (IMP), intramuscular fat (IMF), shear force, pH, cooking loss, and meat color, were measured. Transcriptomic sequencing and metabolomic analysis were performed on muscle samples with high (3895.70 ± 107.03 mg/kg) and low (2751.72 ± 175.29 mg/kg) purine contents (n = 6 per group). Differentially expressed genes were validated by quantitative PCR and Western blot. In vivo autophagy regulation experiments were performed on mice using rapamycin (activator) and chloroquine (inhibitor).

RESULTS

No significant correlation was found between purine content and meat quality traits, suggesting that reducing purine content does not negatively affect mutton quality. An autophagy-related gene, LAPTM5 (lysosomal-associated protein transmembrane 5), was identified as a key gene negatively regulating purine content. In vivo autophagy regulation experiments demonstrated that autophagy affects purine metabolism by modulating key enzymes such as xanthine dehydrogenase (XDH) and hypoxanthine-guanine phosphoribosyltransferase 1 (HPRT).

CONCLUSIONS

This study reveals the role of autophagy in regulating purine metabolism through the key enzymes XDH and HPRT, providing new insights for improving mutton quality in the future.

The association of RBP4 with chronic kidney diseases in southern Chinese population

Background

Retinol binding protein 4 (RBP4), as a novel adipokine, has been proven to be highly related to insulin resistance, obesity, diabetes, hypertension, hyperuricemia and other metabolic diseases, which are all risk factors for chronic kidney disease (CKD). However, there is a lack of sufficient studies to explore the relationship between RBP4 and CKD, and no reports have described the predictive value of RBP4 for CKD. This study was designed to clarify the relationship between RBP4 and CKD and its potential predictive value.

Methods

Our team has conducted a large-scale cross-sectional survey that contained 2117 individuals on the southern coast of China. Correlation test, logistic regression analysis were used to evaluate the association between RBP4 and CKD. Receiver operating characteristic (ROC) were used to evaluate the optimal cut-off and predictive value of RBP4 for predicting CKD.

Results

By using the quartile grouping method, the population was divided into four groups according to the RBP4 level. As the RBP4 level increased, the prevalence of CKD also gradually increased among different groups. RBP4 was also correlated with various metabolic risk factors, such as blood glucose, blood lipids, blood pressure, waist circumference, uric acid, and with kidney function indicators such as creatinine, urine protein. Logistic regression analysis found that after adjusting for confounders, RBP4 remained significantly associated with CKD, independent of metabolic risk factors. ROC analysis showed that RBP4 as a single index, AUC (0.666) was superior to Scr, FBG, Log HOMA-IR, WC, TG, VLDL-C, UA, HDL-C, LDL-C, and that combining RBP4 indicator and other common risk factors of CKD can improve the accuracy for predicting CKD.

Conclusion

This study found that the RBP4 was strongly correlated with CKD, RBP4 may become a valuable marker and have strong power for predicting CKD.

Potassium sodium hydrogen citrate intervention on gut microbiota and clinical features in uric acid stone patients

The high recurrence rate of renal uric acid stone (UAS) poses a significant challenge for urologists, and potassium sodium hydrogen citrate (PSHC) has been proven to be an effective oral dissolution drug. However, no studies have investigated the impact of PSHC on gut microbiota and its metabolites during stone dissolution therapy. We prospectively recruited 37 UAS patients and 40 healthy subjects, of which 12 patients completed a 3-month pharmacological intervention. Fasting vein blood was extracted and mid-stream urine was retained for biochemical testing. Fecal samples were collected for 16S ribosomal RNA (rRNA) gene sequencing and short chain fatty acids (SCFAs) content determination. UAS patients exhibited comorbidities such as obesity, hypertension, gout, and dyslipidemia. The richness and diversity of the gut microbiota were significantly decreased in UAS patients, Bacteroides and Fusobacterium were dominant genera while Subdoligranulum and Bifidobacterium were poorly enriched. After PSHC intervention, there was a significant reduction in stone size accompanied by decreased serum uric acid and increased urinary pH levels. The abundance of pathogenic bacterium Fusobacterium was significantly downregulated following the intervention, whereas there was an upregulation observed in SCFA-producing bacteria Lachnoclostridium and Parasutterella, leading to a significant elevation in butyric acid content. Functions related to fatty acid synthesis and amino acid metabolism within the microbiota showed upregulation following PSHC intervention. The correlation analysis revealed a positive association between stone pathogenic bacteria abundance and clinical factors for stone formation, while a negative correlation with SCFAs contents. Our preliminary study revealed that alterations in gut microbiota and metabolites were the crucial physiological adaptation to PSHC intervention. Targeted regulation of microbiota and SCFA holds promise for enhancing drug therapy efficacy and preventing stone recurrence. KEY POINTS: • Bacteroides and Fusobacterium were identified as dominant genera for UAS patients • After PSHC intervention, Fusobacterium decreased and butyric acid content increased • The microbiota increased capacity for fatty acid synthesis after PSHC intervention.

Risk factors of disease activity and renal damage in patients with systemic lupus erythematosus

PURPOSE

To evaluate the clinical features of patients with Systemic Lupus Erythematosus (SLE) and explore the risk factors of disease activity and renal damage.

METHODS

A retrospective study involving 194 patients were performed. Patients were divided into lupus nephritis (LN) group (63.40%) and non-LN group (36.60%), different disease activity group, and different renal function group according to the clinical data. Multivariate logistic regression analysis showed that albumin (ALB), uric acid (UC), total cholesterol (TC), and anti-dsDNA antibodies were the influencing factors of LN in patients with SLE (P < 0.05); ALB, UC, and complement 3(C3) were the influencing factors of lupus disease activity (P < 0.05); UC, C3, and hemoglobin (HB) were the influencing factors of abnormal renal function in SLE patients.

RESULTS

The results of the ROC curve showed that ALB, UA, and TC had certain predictive value for combined LN in patients with SLE, and the predictive value of ALB was greater than that of TC (P < 0.05); ALB, UA, and C3 being predictors of the activity of patients with SLE; BUN, UA, and HB all had certain predictive value for the abnormal renal function in patients with LN. SLE patients have the high incidence of renal impairment.

CONCLUSION

The results of this study suggest that patients with SLE should regularly monitor the levels of ALB, UA, TC, C3, and HB, as well as pay attention to the intervention of hyperlipidemia and hyperuricemia in patients with SLE to better control disease progression.

Association between gout and kidney stone: results from mendelian randomization and the NHANES study

BACKGROUND

Kidney stones are a common urologic disease with an increasing incidence year by year, and there are similar influences between gout status and kidney stone incidence. Therefore the contribution of gout status to the incidence of kidney stones is unclear. The aim of this study was to investigate the relationship between gout status and kidney stones and to further explore the causal relationship by Mendelian randomization (MR) analysis.

METHOD

An epidemiologic study of 49,693 participants in the 2009-2018 National Health and Nutrition Examination Survey (NHANES) was conducted to examine the association between the two. The causal relationship between gout status and kidney stones was assessed by Mendelian randomization analysis of data from the GWAS database.

RESULT

A total of 28,742 participants were included in the NHANES analysis. We found that gout status was associated with an increased risk of kidney stones [odds ratio (OR) = 1.45 (95%CI, 1.243-1.692); p < 0.001]. In the MR analysis, we found a causal relationship between gout status and the risk of developing kidney stones (OR = 1.047, 95%CI, 1.011-1.085, p = 0.009).

CONCLUSION

There may be an association between gout status and kidney stone risk. This finding requires further large-sample studies and adequate follow-up.

Self-control study of multi-omics in identification of microenvironment characteristics in urine of uric acid stone

The aim of this study is to perform proteomic and metabolomic analyses in bilateral renal pelvis urine of patients with unilateral uric acid kidney stones to identify the specific urinary environment associated with uric acid stone formation. Using cystoscopy-guided insertion of ureteral catheters, bilateral renal pelvis urine samples are collected. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is employed to identify differentially expressed proteins and metabolites in the urine environment. Differentially expressed proteins and metabolites are further analyzed for their biological functions and potential metabolic pathways through Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In the urine from the stone-affected side, eight differential proteins were significantly upregulated, and six metabolites were dysregulated. The uric acid stone urinary environment showed an excess of α-ketoisovaleric acid and 3-methyl-2-oxovaleric acid, which may contribute to the acidification of the urine. Functional and pathway analyses indicate that the dysregulated metabolites are mainly associated with insulin resistance and branched chain amino acid metabolism.

Hyperuricemia Increases the Risk of Postoperative Recurrence in Chinese Patients with Chronic Rhinosinusitis

Background

Elevated serum uric acid is crucial in the pathophysiology of chronic inflammatory diseases. However, its impact on chronic rhinosinusitis (CRS) recurrence risk is unknown. This study investigates the association between elevated serum uric acid and the risk of CRS recurrence.

Methods

A retrospective cohort study was conducted on 1004 CRS patients (including 638 males and 366 females) who received functional endoscopic sinus surgery. All patients were followed up for more than 2 years, and categorized into subgroups based on phenotype, gender, and postoperative recurrence. Cox regression analysis was performed to evaluate the associations between serum uric acid and the risk of CRS recurrence.

Results

After categorization, 104 males had hyperuricemia, and 54 females presented hyperuricemia. The rate of recurrent CRS in the hyperuricemia group was significantly higher compared to the non-hyperuricemia group in both males and females (P<0.05). In both male and female patients, the rate of hyperuricemia and uric acid levels were elevated in the recurrent CRS group in comparison with the non-recurrent CRS group (P<0.05). Unadjusted and adjusted Cox regression analysis demonstrated that serum uric acid was an independent risk factor for CRS recurrence (P<0.05). The receiver operator characteristic curve showed that serum uric acid was a potential biomarker for predicting the recurrence of CRS and its phenotypes in both genders (P<0.05).

Conclusion

There is a close relationship between elevated serum uric acid and the recurrence risk of CRS and its phenotypes, suggesting that serum uric acid may be a novel biomarker for predicting recurrent CRS.

Association between gout and the risk of osteoporosis and fractures: a meta-analysis

OBJECTIVE

The relationship between gout and osteoporosis is poorly clarified, and the association between gout and fractures incidence remains controversial. Hence, in the present study, we aimed to comprehensively evaluate the available literature to elucidate whether gout is associated with an increased risk of both osteoporosis and fractures.

MATERIALS AND METHODS

We conducted an exhaustive search of pertinent literature published until 20 March 2023, in well-recognized databases, namely Medline, Embase and Cochrane Library, focusing on examining the association between gout and the risk of osteoporosis or fracture. Meta-analysis was performed to aggregate the relative risks (RR) using random- or fixed-effects models. Sensitivity analyses were conducted iteratively, whereby each study was removed sequentially to gauge its impact on the overall outcome. Publication bias was assessed using Egger's and Begg's tests. This study was registered with PROSPERO (registry number: CRD42022376822).

RESULTS

Herein, we included 10 observational studies comprising a total of 1,606,095 participants. An independent population sample of four studies validated the significant association between gout and osteoporosis (RR = 1.25, 95% confidence interval [CI] 1.05-1.48), with the results demonstrating robustness. However, our analysis did not detect any association between gout and fracture risk when compared with the control group (RR = 1.09, 95%CI 0.99-1.19), along with high heterogeneity (p for heterogeneity = 0.000; I2 = 79.7%). Further subgroup analysis revealed that gout is positively associated with fracture risk in the Chinese population (RR = 1.17, 95%CI 1.14-1.21), with no evidence of heterogeneity (p for heterogeneity = 0.420; I2 = 0.00%).

CONCLUSION

Our meticulous evaluation of the available literature indicates that gout has no discernible impact on fracture incidence, although it is positively associated with an enhanced risk of osteoporosis. Therefore, it is imperative to prioritize preventive measures to prevent osteoporotic complications in individuals diagnosed with gout.

Decline in measured glomerular filtration rate is associated with simple renal cyst in Chinese patients with type 2 diabetes

AIMS/INTRODUCTION

Simple renal cysts (SRC) are associated with age, hypertension and hyperuricemia, which are risk factors of renal impairment. This study aimed to investigate the prevalence of SRC and its association with measured glomerular filtration rate (mGFR) in patients with type 2 diabetes mellitus in China.

METHODS

A total of 3,552 patients with type 2 diabetes mellitus admitted to Shanghai Sixth People's Hospital from January 2012 to December 2016 were investigated. All participants were diagnosed as SRC by color Doppler, and all participants were measured for GFR by using dynamic renal scintigraphy with technetium-99m-diethylene triamine peta-acetic acid.

RESULTS

The prevalence of SRC was 17.4% (619 cases). Participants with SRC had significantly lower mGFR values than those without SRC (86.16 ± 26.20 vs 94.88 ± 23.98 mL/min/1.73 m2 , P < 0.001). In 478 participants with unilateral renal cyst, the mGFR of the kidney affected by SRC was significantly lower than that of the unaffected kidney (43.32 ± 13.74 vs 44.18 ± 13.34 mL/min/1.73 m2 , P = 0.014). The participants were divided into four groups according to the quartiles of mGFR level (≥109.50, 93.80-109.49, 76.90-93.79 and <76.90 mL/min/1.73 m2 ). The prevalence of SRC gradually increased with decreasing mGFR level (12.9, 13.9, 16.6 and 27.8%, respectively; P trend <0.01). After adjusting for age, sex, duration of diabetes, hypertension and other potential confounders, the logistic regression showed that SRC was an independent risk factor for impaired GFR (<60 mL/min/1.73 m2 ; odds ratio 1.656; 95% confidence interval 1.451-1.890, P < 0.001).

CONCLUSION

SRC is an independent risk factor for the decrease of mGFR in Chinese diabetes patients, and could affect the renal GFR measured by dynamic renal scintigraphy on the SRC side.

The potential relationship between uric acid and the recovery in sudden sensorineural hearing loss

OBJECTIVE

Serum uric acid is proven to be associated with chronic hearing loss, but its effect on Sudden Sensorineural Hearing Loss (SSNHL) is unclear. This study aims to evaluate the prognostic values of serum uric acid levels in SSNHL patients.

METHODS

The clinical records of SSNHL patients were retrospectively reviewed. Patients were divided into different groups based on hearing recovery and audiogram type, and uric acid levels were compared. Based on uric acid levels, patients were categorized into normouricemia and hyperuricemia groups, and clinical features and hearing recovery were evaluated. Univariate and multivariate analyses were performed to identify prognostic factors.

RESULTS

In total, 520 SSNHL patients were included in this study, including 226 females and 294 males. In female patients, 186 patients were included in the normouricemia group, and 40 patients were enrolled in the hyperuricemia group. Significant differences were observed in uric acid levels, Total Cholesterol (TC), rate of complete recovery, and slight recovery between the two groups. In male patients, 237 subjects were categorized into the normouricemia group, and 57 patients were included in the hyperuricemia group. The rate of complete recovery and slight recovery was lower in the hyperuricemia group compared to the normouricemia group. All patients were further divided into good recovery and poor recovery groups based on hearing outcomes. The uric acid levels, initial hearing threshold, rate of hyperuricemia, and TC were lower in the good recovery group than the poor recovery group both in female and male patients. Binary logistic regression results showed that uric acid levels, initial hearing threshold, and hyperuricemia were associated with hearing recovery.

CONCLUSION

Hyperuricemia might be an independent risk factor for hearing recovery in SSNHL patients. Serum uric acid and initial hearing threshold possibly affected the hearing outcome in males and females with SSNHL.

LEVEL OF EVIDENCE

Level 4.

Efficacy and safety of tart cherry supplementary citrate mixture on gout patients: a prospective, randomized, controlled study

BACKGROUND

Low urine pH, which may be mediated by metabolic syndrome (MetS), is common in gout. Tart cherries are shown to improve MetS symptoms and possess anti-inflammatory properties. However, the efficacy of tart cherry supplements on urine pH has yet to be studied.

OBJECTIVES

This study aimed to investigate the efficacy and safety of tart cherry supplementary citrate (TaCCi) mixture on urine pH, serum urate (sUA), C-reactive protein (CRP), and gout flares in gout patients initiating urate-lowering therapy (ULT), in comparison to citrate mixture and sodium bicarbonate.

METHODS

A prospective, randomized (1:1:1), open-label, parallel-controlled trial was conducted among 282 men with gout and fasting urine pH ≤ 6, who were initiating ULT with febuxostat (initially 20 mg daily, escalating to 40 mg daily if serum urate ≥ 360 μmol/L). Participants were randomized to groups taking either sodium bicarbonate, citrate mixture, or TaCCi mixture. All participants were followed every 4 weeks until week 12. Urine pH and sUA were co-primary outcomes, with various biochemical and clinical secondary endpoints.

RESULTS

Urine pH increased to a similar extent in all three groups. SUA levels declined in all three groups as well, with no significant differences observed between the groups. At week 12, the TaCCi mixture group exhibited a greater reduction in the urine albumin/creatinine ratio (UACR) compared to the other two groups (p < 0.05). Participants taking TaCCi mixture or citrate mixture experienced fewer gout flares than those in the sodium bicarbonate group over the study period (p < 0.05). Additionally, the TaCCi mixture group had a lower CRP level at week 12 relative to the other two groups (p < 0.01). Adverse events were similar across all three groups.

CONCLUSION

The TaCCi mixture had similar efficacy and safety on urine alkalization and sUA-lowering as the citrate mixture and sodium bicarbonate in patients with gout. However, the TaCCi mixture resulted in greater improvements in UACR and CRP, which suggests that tart cherry supplements may provide additional benefits for renal protection and reduce inflammation in gout, particularly when starting ULT.

TRIAL REGISTRATION

This project was registered in ChiCTR ( www.chictr.org.cn ), with the registration number: ChiCTR2100050749.

Analysis of Metabolites in Gout: A Systematic Review and Meta-Analysis

(1) Background: Many studies have attempted to explore potential biomarkers for the early detection of gout, but consistent and high levels of evidence are lacking. In this study, metabolomics was used to summarize the changes of metabolites in the literature and explore the potential value of metabolites in predicting the occurrence and development of gout. (2) Methods: We searched the databases including the EMBASE, the Cochrane Library, PubMed, Web of Science, VIP Date, Wanfang Data, and CNKI, and the screening was fulfilled on 30 July 2022. The records were screened according to the inclusion criteria and the risk of bias was assessed. Qualitative analysis was performed for all metabolites, and meta-analysis was performed for metabolite concentrations using random effects to calculate the Std mean difference and 95% confidence interval. (3) Results: A total of 2738 records were identified, 33 studies with 3422 participants were included, and 701 metabolites were identified. The qualitative analysis results showed that compared with the healthy control group, the concentration of 56 metabolites increased, and 22 metabolites decreased. The results of the meta-analysis indicated that 17 metabolites were statistically significant. (4) Conclusions: Metabolites are associated with gout. Some specific metabolites such as uric acid, hypoxanthine, xanthine, KYNA, guanosine, adenosine, creatinine, LB4, and DL-2-Aminoadipic acid have been highlighted in the development of gout.

Longitudinal Association between Uric Acid and Incident Sarcopenia

BACKGROUND

Sarcopenia has emerged as a significant public health concern. Uric acid (UA), as a metabolite with excellent antioxidant capacity, has been found to be associated with sarcopenia. However, the casual effects of UA on incident sarcopenia still remain unclear. Our study aimed to explore the longitudinal association between UA and incident sarcopenia among middle-aged and older adults.

METHOD

A total of 5086 participants aged ≥45 years old without sarcopenia at baseline were included from the China Health and Retirement Longitudinal Study (CHARLS). Due to the sex differences, the UA levels were analyzed by categorizing into sex-specific quartiles or by using UA levels as a continuous variable (per 1 mg/dL). The longitudinal association between UA and incident sarcopenia was evaluated using Cox proportional hazards regression models.

RESULTS

During the 4-year follow-up period, 552 (10.85%) participants with incident sarcopenia were identified, of which 370 cases were males and 182 cases were females. Compared to the first quartile (Q1) UA levels, the Q3 and Q4 UA levels were significantly associated with lower risk of incident sarcopenia in males (Q3: adjusted hazard ratio (HR), 0.72; 95% CI (confidence interval), 0.54-0.97; Q4: HR, 0.57; 95% CI, 0.41-0.80). When UA was as a continuous variable (per 1 mg/dL), the association in males remained significant (HR: 0.87; 95% CI: 0.79-0.97). No significant association was observed in females.

CONCLUSION

Our findings indicated that UA was negatively associated with incident sarcopenia in males but not in females among middle-aged and older Chinese.

Association between Serum Klotho and Kidney Stones in US Middle-Aged and Older Individuals with Diabetes Mellitus: Results from 2007 to 2016 National Health and Nutrition Survey

INTRODUCTION

Kidney stones (KSs) are associated with hematuria and renal failure and pose a significant clinical and public health concern. Diabetes is associated with a higher risk of KSs. In addition, α-Klotho (Klotho), as a novel antiaging protein, is associated with kidney disease, diabetes, and complications and may participate in the pathological mechanism of KSs. However, studies that used large population-based database research are limited. Therefore, this study aimed to investigate whether or not KS prevalence is associated with serum Klotho levels in diabetic adults in the USA.

METHODS

This nationally representative cross-sectional study used data on diabetic adults in the USA aged 40-79 years from the National Health and Nutrition Examination Survey 2007-2016 cycles. Multivariate logistic regression models were used to calculate the association between Klotho and KS. Restricted cubic splines were used to further test for linearity and explore the shape of the dose-response association. Moreover, we performed stratified and interaction analyses to see if the relationship was stable in different subgroups.

RESULTS

Among the 3,537 diabetic patients included in this study (mean age of 61.4 years, consisting of 51.3% males), 543 participants (15.4%) suffered from KS. In the fully adjusted model, Klotho was negatively associated with KS (OR = 0.72; 95% CI: 0.54-0.96; p = 0.027). A negative relationship was observed between the occurrence of KS and Klotho (nonlinear: p = 0.560). Some differences in the association between Klotho and KS were found in stratified analyses; however, these differences lacked statistical significance.

CONCLUSIONS

Serum Klotho was negatively associated with the incidence of KS; when ln-transformed Klotho concentration increased by 1 unit, the risk of KS was 28% lower.

A new application of papain: As a peroxidase-like catalyst for fluorometric detection of uric acid

Papain, as a classical cysteine protease, has been widely used in the food, pharmaceutical, chemical, and cosmetic fields. However, there are few information about the peroxidase-like activity of papain catalyzed substrate to produce fluorescence. In this study, we found that papain can catalyze H₂O₂ to convert o-phenylenediamine (OPD), and generate fluorescence emission at 550 nm under 430 nm excitation. Based on this foundation, we report a papain/OPD/H₂O₂ system for fluorescence detection of uric acid. The method exhibits a wide linear range of 10-1000 μM with a limit-of-detection of 4.6 μM, and has been successfully used to detect uric acid in human serum. This study paves the way for the application of papain as catalyst for fluorescence detection of different target biomolecules, such as cholesterol, glucose, lactate, for which H₂O₂ is a product of oxidoreductase enzymes.

Epidemiology of Kidney Stones

In the past two decades, major breakthroughs that improve our understanding of the pathophysiology and therapy of kidney stones (KS) have been lacking. The disease continues to be challenging for patients, physicians, and healthcare systems alike. In this context, epidemiological studies are striving to elucidate the worldwide changes in the patterns and the burden of the disease and identify modifiable risk factors that contribute to the development of kidney stones. Our expanding knowledge of the epidemiology of kidney stones is of paramount importance and largely upgrades the modern management of the disease. In this paper, we review the variables affecting prevalence and incidence, including age, gender, race, ethnicity, occupation, climate, geography, systemic diseases, diabetes, vascular disease, chronic kidney disease, and dietary risk factors relevant to kidney stones.

Rapid identification of early renal damage in asymptomatic hyperuricemia patients based on urine Raman spectroscopy and bioinformatics analysis

Objective: The issue of when to start treatment in patients with hyperuricemia (HUA) without gout and chronic kidney disease (CKD) is both important and controversial. In this study, Raman spectroscopy (RS) was used to analyze urine samples, and key genes expressed differentially CKD were identified using bioinformatics. The biological functions and regulatory pathways of these key genes were preliminarily analyzed, and the relationship between them as well as the heterogeneity of the urine components of HUA was evaluated. This study provides new ideas for the rapid evaluation of renal function in patients with HUA and CKD, while providing an important reference for the new treatment strategy of HUA disease. Methods: A physically examined population in 2021 was recruited as the research subjects. There were 10 cases with normal blood uric acid level and 31 cases with asymptomatic HUA diagnosis. The general clinical data were collected and the urine samples were analyzed by Raman spectroscopy. An identification model was also established by using the multidimensional multivariate method of orthogonal partial least squares discriminant analysis (OPLS-DA) model for statistical analysis of the data, key genes associated with CKD were identified using the Gene Expression Omnibus (GEO) database, and key biological pathways associated with renal function damage in CKD patients with HUA were analyzed. Results: The Raman spectra showed significant differences in the levels of uric acid (640 cm^-1), urea, creatinine (1,608, 1,706 cm^-1), proteins/amino acids (642, 828, 1,556, 1,585, 1,587, 1,596, 1,603, 1,615 cm^-1), and ketone body (1,643 cm^-1) (p < 0.05). The top 10 differentially expressed genes (DEGs) associated with CKD (ALB, MYC, IL10, FOS, TOP2A, PLG, REN, FGA, CCNA2, and BUB1) were identified. Compared with the differential peak positions analyzed by the OPLS-DA model, it was found that the peak positions of glutathione, tryptophan and tyrosine may be important markers for the diagnosis and progression of CKD. Conclusion: The progression of CKD was related to the expression of the ALB, MYC, IL10, PLG, REN, and FGA genes. Patients with HUA may have abnormalities in glutathione, tryptophan, tyrosine, and energy metabolism. The application of Raman spectroscopy to analyze urine samples and interpret the heterogeneity of the internal environment of asymptomatic HUA patients can be combined with the OPLS-DA model to mine the massive clinical and biochemical examination information on HUA patients. The results can also provide a reference for identifying the right time for intervention for uric acid as well as assist the early detection of changes in the internal environment of the body. Finally, this approach provides a useful technical supplement for exploring a low-cost, rapid evaluation and improving the timeliness of screening. Precise intervention of abnormal signal levels of internal environment and energy metabolism may be a potential way to delay renal injury in patients with HUA.

Urinary Risk Profile, Impact of Diet, and Risk of Calcium Oxalate Urolithiasis in Idiopathic Uric Acid Stone Disease

The role of diet in the pathogenesis of uric acid (UA) nephrolithiasis is incompletely understood. This study investigated the effect of dietary intervention on the risk of UA stone formation under standardized conditions. Twenty patients with idiopathic UA stone disease were included in the study. Dietary intake and 24 h urinary parameters were collected on the usual diet of the patients and a standardized balanced mixed diet. Although urinary UA excretion did not change, the relative supersaturation of UA decreased significantly by 47% under the balanced diet primarily due to the significant increase in urine volume and pH. Urinary pH was below 5.8 in 85% of patients under the usual diet, and in 60% of patients under the balanced diet. The supersaturation of calcium oxalate declined significantly under the balanced diet due to the significant decrease in urinary calcium and oxalate excretion and the increase in urine volume. Dietary intervention is a key component in the management of UA nephrolithiasis. Urinary calcium and oxalate excretion should also be monitored in patients with pure UA calculi to reduce the risk of mixed stone formation with calcium oxalate. Lower urinary pH in UA stone patients can only be partially explained by diet.

Changes in aging-induced kidney dysfunction in mice based on a metabolomics analysis

Kidney dysfunction is particularly important in systemic organ injuries caused by aging. Metabolomics are utilized in this study to explore the mechanism of kidney dysfunction during aging by the identification of metabolites and the characterization of metabolic pathways. We analyzed the serum biochemistry and kidney histopathology of male Kunming mice aged 3 months and 24 months and found that the aged mice had inflammatory lesions, aggravated fibrosis, and functional impairment. A high-resolution untargeted metabolomics analysis revealed that the endogenous metabolites in the kidneys and urine of the mice were significantly changed by 25 and 20 metabolites, respectively. A pathway analysis of these differential metabolites revealed six key signaling pathways, namely, D-glutamine and D-glutamate metabolism, purine metabolism, the citrate cycle [tricarboxylic acid (TCA) cycle], histidine metabolism, pyruvate metabolism, and glyoxylate and dicarboxylate metabolism. These pathways are involved in amino acid metabolism, carbohydrate metabolism, and nucleotide metabolism, and these can lead to immune regulation, inflammatory responses, oxidative stress damage, cellular dysfunction, and bioenergy disorders, and they are closely associated with aging and kidney insufficiency. We also screened nine types of sensitive metabolites in the urine as potential biomarkers of kidney dysfunction during the aging process to confirm their therapeutic targets in senior-induced kidney dysfunction and to improve the level of risk assessment for senile kidney injury.