Study on the diagnosis of gout with xanthine and hypoxanthine

The immune microenvironment related biomarker CCL18 for patients with gout by comprehensive analysis

In the present study, we uncovered and validated potential biomarkers related to gout, characterized by the accumulation of sodium urate crystals in different joint and non-joint structures. The data set GSE160170 was obtained from the GEO database. We conducted differential gene expression analysis, GO enrichment assessment, and KEGG pathway analysis to understand the underlying processes. The overlap of 66 methodologies was visualized through UpSetR (v1.3.3). We used Cytoscape's cytoHubba to detect pivotal genes and mapped out protein-protein interaction (PPI) networks. The overlapping targets among upregulated, downregulated, and key genes were depicted using a Venn diagram. CIBERSORT was employed to ascertain the composition of 22 immune cell types in tissue samples. Subsequently, CCL18 levels in serum samples were quantified using enzyme-linked immunosorbent assay (ELISA) and served as a biomarker evaluation metric. The DEG analysis revealed 1000 genes with varied expression (with an even split of 500 upregulated and 500 downregulated genes) when contrasting gout patients with healthy counterparts. The GO enrichment findings revealed a predominant association with small molecule degradation, positive regulatory catabolic mechanism, organelle division, signal transduction, and axon formation. KEGG assay associated the DEGs predominantly with conditions such as systemic lupus erythematosus, pathways such as tumor necrosis factor (TNF) signaling, as well as alcohol dependency and necroptosis. Intersections were visualized using UpSetR, resulting in the identification of 20 hub genes. A Venn representation highlighted five upregulated genes and three downregulated genes. CIBERSORT analysis revealed a noticeable increase in the number of gamma delta T cells and regulatory T cells. The PPI network analysis revealed CC Chemokine ligand 18 (CCL18) as a critical gene. Gout-afflicted samples exhibited a heightened CCL18 expression compared to healthy ones (P < 0.01). Altogether, CCL18 is a promising biomarker for patients with gout and is suitable for predicting of gout.

Metabolic signatures of metabolites of the purine degradation pathway in human plasma using HILIC UHPLC-HRMS

The metabolic disorders in the purine degradation pathway have proven to be closely associated with several human diseases. However, the etiology is not yet fully understood. Profile assay of purine intermediates and uric acid involved in the metabolic pathway can provide additional insight into the nature and severity of related diseases. Purine metabolites are endogenous chemicals with high hydrophilicity, polarity, and similar structures, thus there is a great need for a specific method to quantify them directly in biological fluids with a short running time. Herein, eight purine degradation pathway metabolites, including xanthine, hypoxanthine, guanine, xanthosine, inosine, guanosine, adenosine and uric acid, in human plasma were quantitatively measured using hydrophilic interaction chromatography-tandem high-resolution mass spectrometry (HILIC-HRMS) in a short running time of 10 min. The method was systematically validated for specificity, linearity of the calibration curve, the limit of detection, the limit of quantification, the lower limit of quantification, precision, accuracy, extraction recovery, matrix effect, and stability. The results showed that the method was linear (R2 > 0.99), accurate (the intra- and inter-day recoveries of all analytes ranged from 90.0 % to 110.0 %), and precise (the intra- and inter-day precisions were less than 6.7 % and 8.9 %, respectively) with the lower limits of quantification ranging from 3 to 10,000 ng/mL. The extraction recoveries and matrix effects were repeatable and stable. All the analytes were stable in the autosampler and could be subject to three freeze-thaw cycles. The developed method was ultimately applied to 100 plasma specimens from healthy individuals. The results showed that the concentrations of different purine metabolites varied dramatically in plasma specimens. Diet and body mass index (BMI) were the most significant factors determining purine levels, followed by drinking and sex. Age, smoking and bedtime showed a very weak correlation with purine metabolism. The findings of the present work reveal the characteristics of purine metabolism in human plasma under non-pathological conditions. The results also highlight the factors that can cause changes in purine metabolism, which are useful in developing effective treatment strategies for metabolic disorders of purines, particularly for those caused by lifestyle factors.

Green manufacturing of a hypoxanthine enzyme sensor for fish freshness based on modified nitrocellulose surface with chito-oligosaccharide

Hypoxanthine (Hx), produced by adenosine triphosphate (ATP) metabolism, is a valuable indicator that determines the quality and degradation status of meat products and is also an important biochemical marker to certain diseases such as gout. The rapid emergence of paper-based enzyme biosensors has already revolutionized its on-site determination. But it is still limited by the complex patterning and fabrication, unstable enzyme and uneven coloration. This work aims to develop an eco-friendly method to construct engineered paper microfluidic, which seeks to produce reaction and non-reaction zones without any patterning procedure. Chito-oligosaccharide (COS), derived from shrimp shells, was used to modify nitrocellulose membranes and immobilize xanthine oxidase (XOD) and chromogenic agent of nitro blue tetrazolium chloride (NBT). After modification, micro fluids could converge into the modification area and Hx could be detected by XOD-catalyzed conversion. Due to the positively charged cationic basic properties of COS, the enzyme storage stability and the color homogeneity could be greatly strengthened through the electrostatic attraction between COS and XOD and formazan product. The detection limit (LOD) is 2.30 μM; the linear range is 0.05-0.35 mM; the complete test time can be as short as 5 min. The COS-based biosensor shows high specificity and can be used directly for Hx in complex samples such as fish and shrimp samples, and different broths. This biosensor is eco-friendly, nontechnical, economical and therefore a compelling platform for on-site or home-based detection of food freshness.

Highly sensitive detection for xanthine by combining single-band red up-conversion nanoparticles and cycle signal amplification strategy based on internal filtration effect

Up-conversion nanoparticles (UCNPs), especially single-band bright red UCNPs, have better penetration of biological tissues, absorb less lost energy, and have higher sensitivity and accuracy in the determination of actual biological samples in the field of biosensing. Here, a novel colorimetric and fluorescent dual-channel method based upon an internal filtration effect (IFE) quenching mechanism was proposed for the quantitative analysis of xanthine (XA) by using red UCNPs as fluorescence indicator and 3,3',5,5' -tetramethylbenzidine (TMB) as chromogenic substrate. The sensitivity of the detection system was also enhanced by a cycle signal amplification strategy based on the Fenton reaction. Under the best conditions, the detection limits of XA by fluorescent and colorimetric methods were 0.58 μM and 1.19 μM, respectively. The developed method was applied to the detection of XA in actual serum samples, and the recoveries of the spiked samples by fluorescent and colorimetric methods were in the range of 96.3-104.3 % and 94.3-105.4 %, respectively. In addition, the commercial ELISA method was used to verify the application of the proposed method and the test results of XA were close to those obtained by fluorescent and colorimetric methods, indicating that the accuracy of the developed nanosensing system was acceptable.

Determination of tryptophan and its indole metabolites in follicular fluid of women with diminished ovarian reserve

Tryptophan (TRP) and its indole metabolites exhibit numerous biological effects, especially their antioxidant properties. This study used untargeted metabolomics in conjunction with targeted metabolomics to investigate the differential expression of tryptophan and its indole metabolites in follicular fluid (FF) of diminished ovarian reserve (DOR) and normal ovarian reserve (NOR) populations. This study included patients with DOR (n = 50) and females with NOR (n = 35) who received in vitro fertilization and embryo transfer. Untargeted metabolomics suggests that diminished ovarian reserve affects the metabolic profile of FF, TRP and indole metabolites were significantly down-regulated in the DOR group. Targeted metabolomics quantification revealed that the levels of TRP, IPA and IAA in the FF of the DOR group were significantly lower than those of the NOR group (P < 0.01). The concentration of TRP in FF is positively correlated with the available embryo rate in NOR females. These results provide data support to explore the pathogenesis of DOR and to look for new biomarkers and ovarian protectors. Additionally, alterations in TRP and its indole metabolites in FF may indirectly reflect the interaction between intestinal flora and the follicular microenvironment.

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.

Distribution of serum uric acid concentration and its association with lipid profiles: a single-center retrospective study in children aged 3 to 12 years with adenoid and tonsillar hypertrophy

BACKGROUND

Presently, there is no consensus regarding the optimal serum uric acid (SUA) concentration for pediatric patients. Adenoid and tonsillar hypertrophy is considered to be closely associated with pediatric metabolic syndrome and cardiovascular risk and is a common condition in children admitted to the hospital. Therefore, we aimed to evaluate the relationship between SUA and dyslipidemia and propose a reference range for SUA concentration that is associated with a healthy lipid profile in hospitalized children with adenoid and tonsillar hypertrophy.

METHODS

Preoperative data from 4922 children admitted for elective adenoidectomy and/or tonsillectomy surgery due to adenoid and tonsillar hypertrophy were collected. SUA concentrations were scaled to standard deviation (SD), and SUA deviations were expressed as SD from the mean SUA of children without dyslipidemia.

RESULTS

The mean SUA concentration of the participants was 4.27 ± 1.01 mg/dL, and the prevalence of hyperuricemia was 1.6% when it was defined using an SUA of ≥ 7.0 mg/dL. Participants with dyslipidemia (856, 17.4%) had a higher prevalence of hyperuricemia (3.4% vs. 1.2%, P < 0.001) and higher SUA concentrations (4.51 ± 1.15 vs. 4.22 ± 0.97 mg/dL, P < 0.001) than those with ortholiposis. The circulating lipid status of participants with SUAs < 1 SD below the mean value for the participants with ortholiposis (range 1.80-3.28 mg/dL) was more normal. Each 1-SD increase in SUA was associated with a 27% increase in the risk of dyslipidemia (OR = 1.270, 95% CI, 1.185-1.361). Adjustment for a number of potential confounders reduced the strength of the relationship, but this remained significant (OR = 1.125, 95% CI, 1.042-1.215). The higher risk of dyslipidemia was maintained for participants with SUAs > 1 SD above the mean value of the participants with ortholiposis.

CONCLUSIONS

SUA was independently associated with dyslipidemia in children with adenoid and tonsillar hypertrophy, and an SUA < 1 SD below the mean value for patients with ortholiposis was associated with a healthy lipid profile.

Hypouricemic and nephroprotective effects of palmatine from Cortex Phellodendri Amurensis: A uric acid modulator targeting Keap1-Nrf2/NLRP3 axis

ETHNOPHARMACOLOGICAL RELEVANCE

Palmatine (Pal) is a major bioactive alkaloid originated from ancient Chinese herbal medicine Cortex Phellodendri Amurensis (CPA), which has long been applied to treat hyperuricemia (HUA)-related diseases. Pal possesses potent anti-inflammatory and anti-oxidant effects against metabolic diseases. However, its potential beneficial effect against PO (potassium oxonate)/HX (hypoxanthine)-induced HUA remains elusive.

AIM OF THE STUDY

This study aimed to investigate the potential pharmacological effect and mechanism of Pal on PO/HX-induced HUA in mice.

MATERIAL AND METHODS

A mouse model of HUA was established by co-administration of PO/HX once daily for 7 consecutive days. The HUA mice were orally given three doses (25, 50 and 100 mg/kg) of Pal daily for a week. Febuxostat (Feb, 5 mg/kg) was given as a positive control. At the scheduled termination of the experiment, the whole blood, liver and kidney were collected for subsequent analyses. The concentrations of uric acid (UA), creatinine (CRE) and blood urea nitrogen (BUN), and activities of adenosine deaminase (ADA) and xanthine oxidase (XOD) were evaluated. Histopathological alterations of the kidney were detected by H&E staining. The inflammatory and oxidative stress status was detected by assay kits. Additionally, key proteins involved in the urate transporter, Keap1-Nrf2 and TXNIP/NLRP3 signaling pathways were evaluated by immunohistochemistry and Western blotting. Finally, molecular docking was employed to probe the binding characteristics of Pal and target proteins Keap1, NLRP3, URAT1 and HO-1.

RESULTS

Administration of Pal substantially decreased the elevated kidney weight, lowered UA, CRE and BUN levels, and attenuated abnormal histopathological alterations. Meanwhile, treatment with Pal also dramatically lowered hepatic XOD and ADA activities. Besides, Pal treatment effectively mitigated the renal inflammatory and oxidative stress markers. Further mechanistic investigation indicated Pal distinctly downregulated the protein levels of GLUT9 and URAT1, while up-regulated the expression levels of OAT1 and ABCG2. Pal also restored Nrf2 activation, promoted subsequent expression of anti-oxidative enzymes, and downregulated the expressions of TXNIP, NLRP3, apoptosis-associated speck-like (ASC), caspase-1, IL-1β and IL-18. Molecular docking analysis also indicated Pal firmly bound with Keap1, NLRP3, URAT1 and HO-1.

CONCLUSIONS

These findings indicated that Pal exhibited favorable anti-HUA effect via modulating the expressions of transporter-related proteins and suppressing XOD activity. Furthermore, Pal also alleviated HUA-induced kidney injury, which was at least partially related to restoring Keap1-Nrf2 pathway and inhibiting TXNIP/NLRP3 inflammasome. Our investigation was envisaged to provide experimental support for the traditional application of CPA and CPA-containing classical herbal formulas in the management of HUA-related diseases and might provide novel dimension to the clinical application of Pal.

Oxyberberrubine, a novel liver microsomes-mediated secondary metabolite of berberine, alleviates hyperuricemic nephropathy in mice

BACKGROUND

Berberrubine (BRB), one of the major metabolites of berberine (BBR), exerts an anti-hyperuricemic effect even superior to BBR. Liver is an important location for drug transformation. Nevertheless, there are few studies on the bioactivities and metabolites of BRB.

PURPOSE

We investigated whether oxyberberrubine (OBR), a liver metabolite of BRB, exerted urate-lowering and reno-protective effects in hyperuricemic mice.

METHODS

Liver microsomes were used to incubate BRB for studying its biotransformation. We isolated and identified its new metabolite OBR, and investigated its anti-hyperuricemic and reno-protective effects. In this work, the hyperuricemic mice model was established by receiving potassium oxonate (PO) and hypoxanthine (HX) for 7 consecutive days. 1 h after modeling, different dosages of OBR (5, 10 and 20 mg/kg), BRB (20 mg/kg) or febuxostat (Fex, 5 mg/kg) were given mice by gavage.

RESULTS

Results showed that OBR possessed potent anti-hyperuricemic and reno-protective effects in hyperuricemic mice. Serum uric acid (UA) level was lowered, and the activities of xanthine oxidase (XOD) as well as adenosine deaminase (ADA) in the liver were suppressed after treatment with OBR. Hepatic expressions of XOD were remarkably decreased at mRNA and protein levels by OBR treatment. In addition, OBR prominently alleviated renal injury, embodied in markedly reduced serum creatinine and blood urea nitrogen (BUN) levels, decreased inflammatory mediators (TNF-α, IL-1β, IL-6 and IL-18) levels, mRNA expression of CYP27B1 and repairment of renal tissues damage. Besides, OBR down-regulated renal expression of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), NOD-like receptor 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC), and caspase-1 at mRNA and protein levels.

CONCLUSIONS

In short, our study indicated that OBR possessed superior anti-hyperuricemic and reno-protective effects, at least in part, through the inhibition of XOD, URAT1, GLUT9 and NLRP3 inflammasome signaling pathway in the kidney.

A universal sensing platform based on iron and nitrogen co-doped carbon dots for detecting hydrogen peroxide and related metabolites in human fluid by ratiometric fluorometry and colorimetry

A universal ratiometric fluorescence and colorimetric dual-mode sensing platform for detecting hydrogen peroxide (H₂O₂) and related metabolites in human fluid was constructed based on iron and nitrogen co-doped carbon dots (Fe/N-CDs). As a fluorescent nanomaterial with peroxidase-like property, Fe/N-CDs emits fluorescence at 449 nm (F₄₄₉) under excitation of incident ultraviolet light, and can catalyze the oxidation of o-phenylenediamine (OPD) by H₂O₂ for generating 2,3-diaminophenazine (oxOPD) that exhibits obvious absorption at 420 nm (A₄₂₀) and fluorescence emission at 555 nm (F₅₅₅). The Förster resonance energy transfer (FRET) between Fe/N-CDs and oxOPD would result in the fluorescence quenching Fe/N-CDs and the fluorescence enhancement of oxOPD, which facilitates the quantitation of oxOPD by ratiometric fluorometry. Since the amount of generated oxOPD is determined by the amount of H₂O₂ consumed during the oxidation reaction, the detection of H₂O₂ and related metabolites can be realized by monitoring both ratiometric fluorescent (F₅₅₅/F₄₄₉) and colorimetric (absorption, A₄₂₀) signals of oxOPD. This dual-mode sensing platform exhibits excellent selectivity and sensitivity toward with H₂O₂, xanthine and uric acid in both human serum and urine samples, demonstrating its good potential for monitoring H₂O₂ and metabolites involved in H₂O₂ metabolism in human body. The detection limits (LODs) of H₂O₂, xanthine and uric acid obtained by this sensing platform were 0.07, 0.15, and 0.14 μM for ratiometric fluorescence mode, and 0.12, 0.52, and 0.47 μM for colorimetric mode, respectively. By utilizing appropriate oxidases in this universal sensing platform, the determination of other metabolites involved with producing H₂O₂ can also be realized facilely.

Identification of Inflammation-Related Biomarker Pro-ADM for Male Patients With Gout by Comprehensive Analysis

Objective

Gout is a local inflammatory disease caused by the deposition of monosodium urate (MSU) crystals in joints or adjacent tissues. When some gout occurs without hyperuricemia, or its clinical symptoms and signs are not typical, the diagnosis of gout will be delayed, so there is an urgent need to find a new biomarker to predict and diagnose of gout flare. Our research attempts to find the key genes and potential molecular mechanisms of gout through bioinformatics analysis, and collected general data and blood biochemical samples of patients with gout and healthy, then analyzed and compared the expression of factors regulated by key genes.

Method

GSE160170 were downloaded from GEO database for analysis. The data were normalized to identify the differentially expressed genes (DEGs), then GO and KEGG enrichment analysis were applied. Protein-protein interaction (PPI) networks and hub genes between DEGs were identified. Then collect general information and blood samples from male patients with acute gout, hyperuricemia and healthy. ELISA method was used to detect pro-ADM levels of different groups, and the data was input into SPSS statistical software for analysis.

Result

We identified 266 DEGs (179 up-regulated and 87 down-regulated) between gout patients and healthy controls. GO analysis results show that DEGs are mostly enriched in inflammatory response, growth factor activity, cytokine activity, chemokine activity, S100 protein binding and CXCR chemokine receptor binding. KEGG pathway analysis showed that DEGs are mainly related to Chemokine signaling pathway and Cytokine-cytokine receptor interaction. ADM, CXCR1, CXCR6, CXCL3, CCL3, CCL18, CCL3L3, CCL4L1, CD69, CD83, AREG, EREG, B7RP1, HBEGF, NAMPT and S100B are the most important hub genes in the PPI network. We found that the expression of pro-ADM in the gout group and hyperuricemia group was higher than that in the healthy group, and the difference was statistically significant.

Conclusion

In this study, a series of bioinformatics analyses were performed on DEGs to identify key genes and pathways related to gout. Through clinical verification, we found that pro-ADM can be used as an inflammation-related biomarker for acute attacks of gout, providing new ideas for the diagnosis and treatment of gout.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Review on recent advances in fabrication of enzymatic and chemical sensors for hypoxanthine

Hypoxanthine is an important product of the nucleotide degradation pathway. It has been considered as a potential marker for assessing meat freshness and clinical diagnosis. In the review, we focus on advancement made in the fabrication of hypoxanthine sensors. Several traditional methods are being utilized for the detection of hypoxanthine, but these methods are expensive, complex, require pretreatment of the sample which is time-consuming and trained persons to operate. Sensors have emerged as simple, rapid, economic, disposable, and portable tools for hypoxanthine detection in biological samples. In particular, the review describes the significant role of hypoxanthine in clinical and food applications. Classification of sensors into enzymatic and non-enzymatic sensors along with the different methods used for xanthine oxidase immobilization and type of transducers used for hypoxanthine detection are briefly explained.

An update of genetics, co-morbidities and management of hyperuricaemia

Hyperuricaemia (HU) caused by disorders of purine metabolism is a metabolic disease. A number of epidemiological reports have confirmed that HU is correlated with multiple disorders, such as chronic kidney diseases, cardiovascular disease and gout. Recent studies showed that the expression and functional changes of uric acid transporters, including URAT1, GLUT9 and ABCG2, were associated with HU. Moreover, a large number of genome-wide association studies have shown that these transporters' dysfunction leads to HU. In this review, we describe the recent progress of aetiology and related transporters of HU, and we also summarise the common co-morbidities possible mechanisms, as well as the potential pharmacological and non-pharmacological treatment methods for HU, aiming to provide new ideas for the treatment of HU.

Sensitive ratiometric fluorescence assay for detecting xanthine in serum based on the inner filter effect of enzyme-catalyzed oxidation products to silicon nanoparticles

A new type of fluorescent silicon nanoparticles (SiNPs) were prepared via a facile one-pot hydrothermal method by using N-[3-(trimethoxysilyl)propyl]-ethylenediamine (DAMO) and glucose as reagents, and were subsequently applied to construct a ratiometric fluorescence assay for sensitive and rapid determination of xanthine in human serum. Two catalytic oxidation reactions were employed to induce a fluorescence response of the testing system towards xanthine. Under the catalysis of xanthine oxidase (XOD), xanthine in serum samples was oxidized and produced hydrogen peroxide (H2O2). By utilizing o-phenylenediamine (OPD) as the substrate for horseradish peroxidase (HRP) in the presence of H2O2, fluorescent 2,3-diaminophenazine (DAP) was finally generated. A ratiometric fluorescence assay for xanthine was established by determining the ratio of the green-yellow fluorescence emission of DAP and the blue fluorescence emitted from SiNPs under the inner filter effect (IFE) of DAP. Instead of traditional multi-step procedures for adding reacting reagents to the testing solution, all the reaction reagents were mixed with serum samples in a single step for this assay to shorten the total reaction time. This assay demonstrates superiority over a solo DAP fluorescence-based assay as well as other reported methods, with excellent sensitivity and reduced testing time. The strategies proposed in this work for both synthesis and application of fluorescent SiNPs can be used in future fabrication of novel fluorescent probes, especially for sensing biological metabolites involved in H2O2-generation or consumption reactions.

Improved ultra-high performance liquid chromatographic method for simultaneous determination of five gout-related metabolites in human serum

Creatinine and purines are gout-related metabolites commonly quantified by liquid chromatography coupled with ultraviolet and mass spectrometry. However, the high cost of liquid chromatography coupled with mass spectrometry hindered its extensive use in ordinary hospitals and clinical laboratories. Using the traditional liquid chromatography method, the full separation of these metabolites in complex biological samples is still not achieved. In this study, an improved ultra-high-performance liquid chromatography with ultraviolet spectroscopy method was reported for quantitative determination of five gout-related metabolites (i.e., creatinine, uric acid, hypoxanthine, xanthine, and inosine) in human serum within 10 min. A UHPLC system equipped with a hydrophilic C18 column was used to improve separation, shorten analysis time, and increase analysis throughput. The performance of the method was validated by evaluating linearity (squared correlation coefficient > 0.9991), recovery (92.8-100.0%, with relative standard deviation < 4.7%), accuracy (relative errors < 14.6%), precision (0.2-4.1% for intraday and 2.1-7.3% for interday) and stability (-14.1 to 8.3% in autosampler for 12 h and -13.3 to 2.2% for freeze-thaw cycles). This method was successfully applied to quantify gout-related metabolites in serum samples of healthy controls and gout patients, which was expected to be used in the clinical investigation of gout at different stages.

Quantification of serum purine metabolites for distinguishing patients with hepatitis B from hepatocellular carcinoma

Aim: In order to differential diagnosis of chronic hepatitis B (HBV-I) and hepatocellular carcinoma (HCC), a UPLC-MS/MS method for measuring purine metabolites was developed. Methodology & results: serum samples from 26 HBV-I and 35 HCC patients were collected. Ten purine metabolites were simultaneously quantified by UPLC-MS/MS with tubercidin and uric acid-1,3-¹⁵N₂ as internal standards. The method was validated to meet the requirements of clinical sample analysis. A logistic equation was established for differential diagnosis of HBV-I and HCC by combination of xanthosine and guanine with the area under the receiver operating characteristic curve of 0.885. Conclusion: Guanine and xanthosine are intermediates in the metabolism of purine, which play an important role in gene synthesis, and metabolism regulation. The alteration of serum purine metabolite may contribute to differential diagnosis of HBV-I and HCC.

Study on the diagnosis of gout with xanthine and hypoxanthine

BACKGROUND

Hyperuricemia is the only biochemical index in the classification of acute gouty arthritis in American Rheumatism Association 1977 and the main basis of clinical diagnosis for most doctors. However, nearly half of the time gout occurs without hyperuricemia, especially in an acute attack，which leads to an urgent need to find a new substitute diadynamic criteria of gout. Xanthine and hypoxanthine, as precursors of uric acid, have been reported to be high in gout patients with hyperuricemia and presumed to be gout biomarkers.

OBJECTIVES

To further explore the possibility of xanthine and hypoxanthine to be gout biomarkers as substitutes for uric acid.

METHODS

A reversed-phase HPLC-UV method was employed for simultaneous quantitative detection of uric acid (UA), xanthine (X), and hypoxanthine (HX) in gout patients' (with and without hyperuricemia) and healthy persons' serum.

RESULTS

The xanthine and hypoxanthine concentrations in gout patients with hyperuricemia and without hyperuricemia are higher than in healthy persons with a P < 0.001.

CONCLUSIONS

This study supplements previous researches by confirming that xanthine and hypoxanthine are significantly elevated in gout patients' serum especially in patients' with normouricemia, which supported xanthine and hypoxanthine may have clinical application for the diagnosis of gout.