Systemic Urate Deposition: An Unrecognized Complication of Gout?

Controversies and practical management of patients with gout and chronic kidney disease

Uric acid is a toxin retained with advancing kidney disease. Clinical manifestations of hyperuricemia include gout and systemic inflammation that are associated with increased risk for cardiovascular mortality. As many as one third of all patients with chronic kidney disease (CKD) have a history of gout, yet <25% of these patients are effectively treated to target serum urate levels of ≤6 mg/dL. A major reason for ineffective management of gout and hyperuricemia is the complexity in managing these patients, with some medications contraindicated, others requiring special dosing, potential drug interactions, and other factors. Consequently, many nephrologists do not primarily manage gout despite it being a common complication of CKD, leaving management to the primary physician or rheumatologist. We believe that kidney specialists should consider gout as a major complication of CKD and actively manage it in their patients. Here, we present insights from nephrologists and rheumatologists on a team approach to gout management that includes the nephrologist.

Animal models to study cognitive impairment of chronic kidney disease

Mild cognitive impairment (MCI) is common in people with chronic kidney disease (CKD), and its prevalence increases with progressive loss of kidney function. MCI is characterized by a decline in cognitive performance greater than expected for an individual age and education level but with minimal impairment of instrumental activities of daily living. Deterioration can affect one or several cognitive domains (attention, memory, executive functions, language, and perceptual motor or social cognition). Given the increasing prevalence of kidney disease, more and more people with CKD will also develop MCI causing an enormous disease burden for these individuals, their relatives, and society. However, the underlying pathomechanisms are poorly understood, and current therapies mostly aim at supporting patients in their daily lives. This illustrates the urgent need to elucidate the pathogenesis and potential therapeutic targets and test novel therapies in appropriate preclinical models. Here, we will outline the necessary criteria for experimental modeling of cognitive disorders in CKD. We discuss the use of mice, rats, and zebrafish as model systems and present valuable techniques through which kidney function and cognitive impairment can be assessed in this setting. Our objective is to enable researchers to overcome hurdles and accelerate preclinical research aimed at improving the therapy of people with CKD and MCI.

Associations of serum uric acid with hypertension status, stages, phenotypes and progressions among Chinese middle-aged and elderly

BACKGROUND AND AIMS

No consensus has been reached on the association between serum uric acid (SUA) and hypertension. This study aimed to investigate the associations between SUA and hypertension, including its status, stages, phenotypes and progressions, among middle-aged and older Chinese.

METHODS AND RESULTS

Data were obtained from the China Health and Retirement Longitudinal Study 2011-2015. Binary logistic regression was used to evaluate the association between SUA and hypertension status. Multinomial logistic regression was used to explore the associations of SUA with hypertension stages, phenotypes and hypertension status progressions. Models were adjusted for potential confounders and stratified by sex. A total of 7931 individuals aged ≥45 years were included, with 39.16 % of hypertension. Significant associations were found of SUA with stage2 and above hypertension (quartile 4 [Q4] vs quartile 1 [Q1]: odds ratio 1.78, 95 % confidence interval 1.31-2.42, P < 0.001), and systolic diastolic hypertension (SDH) (Q4 vs Q1: 1.53, 1.14-2.06, P = 0.005). In sex stratification, significant associations were found between SUA and stage2 and above hypertension and SDH only for men. Moreover, higher quartiles of baseline SUA showed increased risks of maintained hypertension from 2011 to 2015 (Q3 vs Q1: 1.23, 1.03-1.48, P = 0.024; Q4 vs Q1: 1.73, 1.43-2.10, P < 0.001).

CONCLUSION

Higher SUA was associated with hypertension and maintained hypertension among Chinese middle-aged and elderly. Sex-specific associations of SUA with hypertension stages and phenotypes were observed. Regular measurement of SUA in clinical practice may indicate hypertension and its progression, particularly among men.

Crystal Diseases of the Spine

Gout, calcium pyrophosphate deposition disease, and apatite calcifications, the three main crystal disorders, may involve the spine. These disorders can be completely asymptomatic or associated with various clinical symptoms, such as acute flares and more chronic manifestations. This article presents the typical and more unusual imaging features encountered in these disorders.

Pegloticase in Uncontrolled Gout: The Infusion Nurse Perspective

Infused biologics, such as pegloticase, are a core component of managing uncontrolled gout, which is increasing in prevalence. Pegloticase is often the last line of therapy for patients with uncontrolled gout; therefore, achieving a successful course of treatment is critical. The infusion nurse's role in patient education, serum uric acid monitoring, and patient medication compliance is essential for ensuring patient safety and maximizing the number of patients who benefit from a full treatment course of pegloticase. Infusion nurses are on the front lines with patients and need to be educated on potential negative effects associated with the medications they infuse, such as infusion reactions, as well as risk management methods like patient screening and monitoring. Further, patient education provided by the infusion nurse plays a large role in empowering the patient to become their own advocate during pegloticase treatment. This educational overview includes a model patient case for pegloticase monotherapy, as well as one for pegloticase with immunomodulation and a step-by-step checklist for infusion nurses to refer to throughout the pegloticase infusion process. A video abstract is available for this article at http://links.lww.com/JIN/A105.

Impact of Dual-Energy Computed Tomography (DECT) Postprocessing Protocols on Detection of Monosodium Urate (MSU) Deposits in Foot Tendons of Cadavers

OBJECTIVE

To evaluate two different dual-energy computed tomography (DECT) post-processing protocols for the detection of MSU deposits in foot tendons of cadavers with verification by polarizing light microscopy as the gold standard.

MATERIAL AND METHODS

A total of 40 embalmed cadavers (15 male; 25 female; median age, 82 years; mean, 80 years; range, 52-99; SD ± 10.9) underwent DECT to assess MSU deposits in foot tendons. Two postprocessing DECT protocols with different Hounsfield unit (HU) thresholds, 150/500 (=established) versus 120/500 (=modified). HU were applied to dual source acquisition with 80 kV for tube A and 140 kV for tube B. Six fresh cadavers (4 male; 2 female; median age, 78; mean, 78.5; range 61-95) were examined by DECT. Tendon dissection of 2/6 fresh cadavers with positive DECT 120 and negative DECT 150 studies were used to verify MSU deposits by polarizing light microscopy.

RESULTS

The tibialis anterior tendon was found positive in 57.5%/100% (DECT 150/120), the peroneus tendon in 35%/100%, the achilles tendon in 25%/90%, the flexor halluces longus tendon in 10%/100%, and the tibialis posterior tendon in 12.5%/97.5%. DECT 120 resulted in increased tendon MSU deposit detection, when DECT 150 was negative, with an overall agreement between DECT 150 and DECT 120 of 80% (p = 0.013). Polarizing light microscope confirmed MSU deposits detected only by DECT 120 in the tibialis anterior, the achilles, the flexor halluces longus, and the peroneal tendons.

CONCLUSION

The DECT 120 protocol showed a higher sensitivity when compared to DECT 150.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Uric acid is independently associated with interleukin‐1β levels in tear fluid of hyperuricemia and gout patients

Objectives

To explore pro‐inflammatory cytokines status in the tear fluid of patients with hyperuricemia and gout and its association with uric acid level.

Methods

A total of 58 control subjects, 58 hyperuricemia patients including 40 asymptomatic hyperuricemia and 18 gout participants were recruited in this study. For tear analysis, each patient's tears were collected using capillary action microcaps after stimulation. Tear uric acid levels were measured using chemiluminescence. Tear and serum interleukin‐1beta (IL‐1β) and tumor necrosis factor‐alpha (TNF‐α) levels were measured using enzyme‐linked immunosorbent assay. The correlation of serum and tear uric acid levels with IL‐1β and TNF‐α were determined.

Results

Tear uric acid levels were significantly higher in hyperuricemia group (98.2 ± 51.5 vs. 42.7 ± 24.0 µmol/L, p < .001) than in controls group. IL‐1β concentrations were significantly higher in hyperuricemia eyes compared to control eyes (210.2 ± 113.9 vs. 142.6 ± 29.8 pg/mL, p < .001). Multiple linear regression analysis showed that tear uric acid levels were independently positively associated with tear IL‐1β concentrations (B = 0.192, p < .001). However, no significant correlations were found between serum or tear uric acid and TNF‐α level. Moreover, there were no statistically differences of tear IL‐1β and TNF‐α levels between the asymptomatic hyperuricemia and gout groups.

Conclusions

Tear uric acid levels were higher in patients with hyperuricemia and gout than in controls. There was a significant positive correlation between tear uric acid value and tear IL‐1β level, implying an interaction between hyperuricemia and ocular inflammation responses.

Urate Transporter ABCG2 Function and Asymptomatic Hyperuricemia: A Retrospective Cohort Study of CKD Progression

RATIONALE & OBJECTIVE

Treatment of asymptomatic hyperuricemia is not commonly implemented. However, it is unclear whether urate deposition that begins during asymptomatic hyperuricemia can induce nephropathy. Dysfunction of ATP-binding cassette subfamily G member 2 (ABCG2), a urate efflux transporter, leads to elevated serum uric acid concentration (SUA). We investigated the association between asymptomatic hyperuricemia and decreased estimated glomerular filtration rate (eGFR), and the impact of ABCG2 on this relationship.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

1,885 Japanese adults undergoing routine health care follow-up between 2007 and 2017 who had eGFR ≥60 mL/min/1.73 m², of which 311 had asymptomatic hyperuricemia (SUA >7.0 mg/dL). Study participants were classified into 3 categories of estimated ABCG2 function (full, 75%, and ≤50% function).

PREDICTORS

Baseline SUA and estimated ABCG2 function.

OUTCOME

Change in eGFR over time.

ANALYTICAL APPROACH

Linear mixed-effect models were used to analyze the relationship between asymptomatic hyperuricemia, ABCG2 function, and eGFR decline.

RESULTS

Asymptomatic hyperuricemia was negligibly associated with eGFR decline overall. However, among those with eGFR 60-89 mL/min/1.73 m² and ≤50% ABCG2 function, eGFR decline was associated with asymptomatic hyperuricemia (P = 0.03). ABCG2 was not associated with eGFR reductions when the SUA was <6.0 mg/dL. Among participants with SUA ≥6.0 mg/dL and eGFR 60-89 mL/min/1.73 m², ≤50% ABCG2 function was associated with approximately 1.2-fold faster eGFR decline compared with fully functional ABCG2 (P = 0.02). Among the participants with SUA ≥6.0 mg/dL and eGFR 60-89 mL/min/1.73 m², the adjusted eGFR slopes (given as mean ± standard error of the mean, in mL/min/1.73 m² per year) were -0.946 ± 0.049, -1.040 ± 0.046, and -1.148 ± 0.069 for full, 75%, and ≤50% ABCG2 function, respectively.

LIMITATIONS

Lack of measurement of urinary urate and uremic toxins that are known to be transported by ABCG2, and no independent validation cohort.

CONCLUSIONS

Asymptomatic hyperuricemia was not associated with eGFR decline, except when in the presence of ≤50% ABCG2 function.

PLAIN-LANGUAGE SUMMARY

The urate transporter ABCG2 is a protein that regulates serum urate concentrations; when dysfunctional, it can lead to elevated serum concentrations of this compound (ie, hyperuricemia). Although persistent hyperuricemia induces gout and kidney injury, the effects on organs during the asymptomatic phase have yet to be established. Therefore, to clarify the relationship between ABCG2, asymptomatic hyperuricemia, and kidney function, we conducted a retrospective cohort study of 1,885 healthy participants, including 311 participants with asymptomatic hyperuricemia. We found that the coexistence of asymptomatic hyperuricemia and severe ABCG2 dysfunction was associated with the age-dependent decline in kidney function. We concluded that asymptomatic hyperuricemia represents a risk factor for chronic kidney disease, at least in individuals with highly dysfunctional ABCG2. This new finding highlights the potential importance of ABCG2 in the pathogenesis of hyperuricemia-induced kidney injury.

Uric Acid and Chronic Kidney Disease: Still More to Do

Gout and hyperuricemia are present in 25% and 60% of patients with chronic kidney disease (CKD), respectively. Despite the common association, the role of uric acid in the progression of kidney disease and in metabolic complications remains contested. Some authorities argue that the treatment of asymptomatic hyperuricemia in CKD is not indicated, and some have even suggested hyperuricemia may be beneficial. Here, we review the various arguments both for and against treatment. The weight of the evidence suggests asymptomatic hyperuricemia is likely injurious, but it may primarily relate to subgroups, those who have systemic crystal deposits, those with frequent urinary crystalluria or kidney stones, and those with high intracellular uric acid levels. We recommend carefully designed clinical trials to test if lowering uric acid in hyperuricemic subjects with cardiometabolic complications is protective.

Surgical Treatment of Hand and Foot Gout Stone and Influence Factors on Prognosis

Purpose

To explore the technique of surgical treatment of hand and foot gout stone by using 3D CT reconstruction images and influence factors on prognosis.

Method

48 cases of hand and foot gout were treated surgically and retrospective analyzed. Before operation, we used 3D CT reconstruction images to check the accurate site and amount of uric acid (white chalk foam) deposition. Different surgical methods were applied depending on the different deposition site of urine acid stone. The frequency of gout attack and blood uric acid was compared before and after surgery. Patients were followed up to observe the recovery and recurrence and then analyzed the reason of unsuccessful healing.

Result

Sutures were removed 2 weeks after operation in all cases. The frequency of gout attack and blood uric acid of patients 3 months after operation was lower than those before operation, and the differences were statistically significant. Follow-up ranged from 1 to 3 years, with an average of 1.8 years. Three cases were not followed up. The remaining 45 cases were healed in the first stage. 40 cases had improved joint function, increased range of motion, and relieved discomfort after movement. 5 cases had no improvement in joint function after operation, and 3 of them had gout stone recurrence (nonoperative area) and were treated by second hospital operation.

Conclusion

Surgical treatment of gout stone in hand and foot under the guidance of three-dimensional CT reconstruction image can effectively alleviate the local symptoms of gout stone and improve the function of hand and foot. Deep tissue can be thoroughly washed by the pressure of pulse gun after resection of the lesion, which can reduce the incidence of gout stone. Malnutrition, hypoproteinemia, and residual urine acid in the wound are the main reasons for unsuccessful healing.

Monosodium urate deposition in the lumbosacral spine of patients with gout compared with non-gout controls: A dual-energy CT study

BACKGROUND

Gout is the most common cause of inflammatory arthritis in adults. Gout predominantly affects the peripheral joints, but an increasing number of published cases report gout affecting the spine. We used dual-energy CT (DECT) to assess the prevalence of monosodium urate (MSU) deposition in the spine of gout patients compared to controls, and to investigate whether gout or spinal MSU deposition is associated with low back pain.

METHODS

25 controls and 50 gout subjects (non-tophaceous and tophaceous) were enrolled. Demographics, gout history, Aberdeen back pain score, serum urate (sU), ESR and CRP were ascertained. Subjects underwent DECT of the lumbosacral spine, which was analyzed using manufacturer's default post-processing algorithm for MSU deposition as well as a maximally-specific algorithm to exclude potential artifact.

FINDINGS

72 subjects were analyzed (25 control, 47 gout). Gout subjects had greater BMI, serum creatinine, sU, CRP, and ESR versus controls. Using the default algorithm, MSU-coded volumes in the lumbosacral spines were significantly higher among the gout subjects vs controls (p = 0.018). 34% of gout subjects vs 4% of controls had spinal MSU-coded deposition (p = 0.0036). Applying the maximally-specific DECT post-processing algorithm, 18% of gout patients vs 0% of controls continued to demonstrate spinal MSU-coded deposition (p = 0.04). Non-tophaceous and tophaceous subjects did not differ in spinal MSU-coded deposition or sU. Gout patients had more back pain than controls.

INTERPRETATION

A significant subpopulation of gout patients have spinal MSU-coded lesions. Default and maximally-specific MSU post-processing algorithms yielded different absolute MSU-coded volumes, but similar patterns of results. Gout patients had more back pain than controls. Spinal MSU deposition in gout patients may have implications for clinical picture and treatment.

Prevalence of Monosodium Urate (MSU) Deposits in Cadavers Detected by Dual-Energy Computed Tomography (DECT)

Background: Dual-energy computed tomography (DECT) allows direct visualization of monosodium urate (MSU) deposits in joints and soft tissues. Purpose: To describe the distribution of MSU deposits in cadavers using DECT in the head, body trunk, and feet. Materials and Methods: A total of 49 cadavers (41 embalmed and 8 fresh cadavers; 20 male, 29 female; mean age, 79.5 years; SD ± 11.3; range 52–95) of unknown clinical history underwent DECT to assess MSU deposits in the head, body trunk, and feet. Lens, thoracic aorta, and foot tendon dissections of fresh cadavers were used to verify MSU deposits by polarizing light microscopy. Results: 33/41 embalmed cadavers (80.5%) showed MSU deposits within the thoracic aorta. 11/41 cadavers (26.8%) showed MSU deposits within the metatarsophalangeal (MTP) joints and 46.3% of cadavers demonstrated MSU deposits within foot tendons, larger than and equal to 5 mm. No MSU deposits were detected in the cranium/intracerebral vessels, or the coronary arteries. Microscopy used as a gold standard could verify the presence of MSU deposits within the lens, thoracic aorta, or foot tendons in eight fresh cadavers. Conclusions: Microscopy confirmed the presence of MSU deposits in fresh cadavers within the lens, thoracic aorta, and foot tendons, whereas no MSU deposits could be detected in cranium/intracerebral vessels or coronary arteries. DECT may offer great potential as a screening tool to detect MSU deposits and measure the total uric acid burden in the body. The clinical impact of this cadaver study in terms of assessment of MSU burden should be further proven.

Anti-inflammatory and Antioxidant Effect of Poly-gallic Acid (PGAL) in an In Vitro Model of Synovitis Induced by Monosodium Urate Crystals

Gout is a chronic and degenerative disease that affects the joints and soft tissues because of the crystalline deposit of monosodium urate. The interaction between monosodium urate crystals (MSU) and synoviocytes generates oxidative and inflammatory states. These physiological characteristics have promoted the study of poly-gallic acid (PGAL), a poly-oxidized form of gallic acid reported to be effective in in vitro models of inflammation. The effect of PGAL in an in vitro model of oxidation and synovial inflammation induced by MSU was evaluated after 24 h of stimulation through the morphological changes, the determination of oxidative stress (OS), IL-1β, and the phagocytosis of the MSU. A 20% reduction in synovial viability and the generation of vesicles were observed when they were exposed to MSU. When PGAL was used at 100 and 200 µg/ml, cell death was reduced by 30% and 17%, respectively. PGAL both doses reduce the vesicles generated by MSU. OS generation in synoviocytes exposed to 100 µg/ml and 200 µg/ml PGAL decreased by 1.28 and 1.46 arbitrary fluorescence units (AFU), respectively, compared to the OS in synoviocytes exposed to MSU (1.9 AFU). PGAL at 200 µg/ml inhibited IL-1β by 100%, while PGAL at 100 µg/ml inhibited IL-1β by 66%. The intracellular MSU decreased in synoviocytes stimulated with 100 µg/ml PGAL. The PGAL has a cytoprotective effect against damage caused by MSU in synoviocytes and can counteract the oxidative and inflammatory response induced by the crystals probably because it exerts actions at the membrane level that prevent phagocytosis of the crystals.

Update on Uric Acid and the Kidney

PURPOSE OF REVIEW

In this review, we report on new findings regarding associations of uric acid with kidney health. We discuss kidney stones, effects of uric acid in chronic kidney disease (CKD), and management of gout in CKD. Recent studies on neuroprotective effects of raising uric acid provide interesting data regarding nephrolithiasis.

RECENT FINDINGS

Elevated urate levels have been implicated in the progression of chronic kidney disease (CKD), but the results from PERL and CKD-FIX studies did not demonstrate that allopurinol slowed CKD progression. The SURE-PD3 sought to determine if increasing uric acid would slow the progression of Parkinson's disease. Results ultimately did not support this hypothesis, but high urinary uric acid levels caused uric acid stones, not calcium stones. Low urinary pH remains the key to the formation of uric acid stones. Thiazolidinediones improve insulin resistance, which is associated with an increase in urine pH. The most recent research has not supported the hypothesis that lowering serum uric acid levels will slow the progression of CKD or provide neuroprotection in Parkinson's disease. It is still unclear as to why uric acid stone formers have a high net acid excretion. The STOP-GOUT trial demonstrates that there was a lack of significant adverse events with higher urate-lowering dosages of allopurinol and febuxostat, despite patients' kidney function. This may push other studies to administer higher dosages per ACR guidelines. Future studies could then demonstrate decreased progression of CKD.

Enhancing the Response Rate to Recombinant Uricases in Patients with Gout

Refractory, or uncontrolled, gout is a chronic, progressive, inflammatory arthropathy resulting from continued urate deposition after failed attempts to lower serum uric acid below the therapeutic threshold with oral urate-lowering therapies such as allopurinol and febuxostat. Recombinant uricase is increasingly being used to treat refractory gout; however, the immunogenicity of uricase-based therapies has limited the use of these biologic therapies. Antidrug antibodies against biologic therapies, including uricase and PEGylated uricase, can lead to loss of urate-lowering response, increased risk of infusion reactions, and subsequent treatment failure. However, co-therapy with an immunomodulator can attenuate antidrug antibody development, potentially increasing the likelihood of sustained urate lowering, therapy course completion, and successful treatment outcomes. This review summarizes evidence surrounding the use of immunomodulation as co-therapy with recombinant uricases.

Improved joint and patient-reported health assessments with pegloticase plus methotrexate co-therapy in patients with uncontrolled gout: 12-month exploratory outcomes of the MIRROR open-label trial

BACKGROUND

Uncontrolled/refractory gout patients are recalcitrant/intolerant to oral urate-lowering therapies (ULTs), experiencing frequent gout flares, functionally limiting tophi, and low quality of life. Pegloticase lowers urate, but anti-pegloticase antibodies limit urate-lowering efficacy and increase infusion reaction (IR) risk. Immunomodulator + pegloticase co-administration may improve treatment response rates, with 79% of MIRROR open-label trial (MIRROR-OL, pegloticase + oral methotrexate) participants meeting 6-month response criteria. Exploratory outcomes from MIRROR-OL are described here.

METHODS

Adults with uncontrolled gout (serum urate [SU] ≥ 6 mg/dL and ULT-intolerance/recalcitrance or functionally limiting tophi) were included. Oral methotrexate (15 mg/week) was administered 4 weeks before and during pegloticase treatment (biweekly 8 mg infusion, ≤ 52 weeks). Exploratory outcomes included change from baseline (CFB) in number of affected joints, Health Assessment Questionnaires (HAQs), and Gout Global Assessments.

RESULTS

Fourteen patients received ≥ 1 pegloticase infusion, with 13 included in 52-week analyses (1 enrolled before treatment-extension amendment, exited at 24 weeks). Three patients prematurely exited due to SU rise; 10 completed 52-week evaluations (8 completed 52 weeks of co-therapy, 2 completed 24 weeks [met treatment goals]). At 52 weeks, SU averaged 1.1 ± 2.5 mg/dL, with improvements in HAQ pain and health (CFB: - 33.6 and - 0.7, respectively), Patient and Physician Global Assessments (CFB: - 4.6 and - 5.7, respectively), and joint involvement (CFB: - 5.6, - 8.4, - 6.0 tender, swollen, tophi-affected joints, respectively). Two patients underwent dual-energy computed tomography, showing concomitant monosodium urate volume reductions. All patients had ≥ 1 AE, with 92.9% experiencing acute flare. One mild IR ("cough") occurred and no new safety signals were identified.

CONCLUSION

Pegloticase + methotrexate co-therapy resulted in sustained SU-lowering with meaningful improvements in clinical measures, urate burden, and patient-reported outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03635957).

Tear Function Alterations and Conjunctival Impression Cytology Findings in Patients With Gout

OBJECTIVES

The aim of this study was to evaluate the tear functions and conjunctival impression cytology (CIC) findings of patients with gout and compare them with healthy controls.

METHODS

Thirty-four patients with gout (group 1) and 32 age-matched and gender-matched healthy individuals (group 2) were included in this cross-sectional study. Schirmer 1 test, tear breakup time (TBUT), Ocular Surface Disease Index (OSDI) score, and CIC grade were evaluated and compared between the groups.

RESULTS

There was no significant difference between the groups in gender and age (P=0.923 and P=0.078, respectively). The mean of Schirmer 1 test result was significantly lower in group 1 (9.74±6.03 mm) than that in group 2 (17.16±9.33 mm) (P<0.001). The TBUT was also significantly lower in group 1 (7.00±2.09 seconds) than that in group 2 (12.75±5.25 seconds) (P<0.001). The OSDI score (20.04±12.92) was significantly higher in group 1 than that in group 2 (6.19±10.07) (P<0.001). Although 10 patients (29.4%) in group 1 had the CIC grade of 2 to 3, none of the controls had CIC grade 2 to 3. The mean CIC grade in group 1 (1.15±0.89) was significantly higher than that in group 2 (0.47±0.51) (P<0.001).

CONCLUSIONS

The results of this study suggest that ocular surface alterations assessed by CIC and tear function abnormalities are more common in patients with gout.

Mini Review: Reappraisal of Uric Acid in Chronic Kidney Disease

Hyperuricemia predicts the development of chronic kidney disease (CKD) and metabolic complications, but whether it has a causal role has been controversial. This is especially true given the 2 recently conducted randomized controlled trials that failed to show a benefit of lowering uric acid in type 1 diabetes-associated CKD and subjects with stage 3-4 CKD. While these studies suggest that use of urate-lowering drugs in unselected patients is unlikely to slow the progression of CKD, there are subsets of subjects with CKD where reducing uric acid synthesis may be beneficial. This may be the case in patients with gout, hyperuricemia (especially associated with increased production), and urate crystalluria. Here, we discuss the evidence and propose that future clinical trials targeting these specific subgroups should be performed.

Management of gout in chronic kidney disease: a G-CAN Consensus Statement on the research priorities

Gout and chronic kidney disease (CKD) frequently coexist, but quality evidence to guide gout management in people with CKD is lacking. Use of urate-lowering therapy (ULT) in the context of advanced CKD varies greatly, and professional bodies have issued conflicting recommendations regarding the treatment of gout in people with concomitant CKD. As a result, confusion exists among medical professionals about the appropriate management of people with gout and CKD. This Consensus Statement from the Gout, Hyperuricemia and Crystal-Associated Disease Network (G-CAN) discusses the evidence and/or lack thereof for the management of gout in people with CKD and identifies key areas for research to address the challenges faced in the management of gout and CKD. These discussions, which address areas for research both in general as well as related to specific medications used to treat gout flares or as ULT, are supported by separately published G-CAN systematic literature reviews. This Consensus Statement is not intended as a guideline for the management of gout in CKD; rather, it analyses the available literature on the safety and efficacy of drugs used in gout management to identify important gaps in knowledge and associated areas for research.

Simple metabolic markers associated with tophaceous gout

INTRODUCTION

The relationship between tophaceous gout and metabolic markers is not well understood. The aim of this study was to compare the correlations between different metabolic markers and tophi and evaluate their potential predictive values for tophus.

METHOD

We analysed the data of gout patients in Beijing Jishuitan Hospital from 2013 to 2020. Ten laboratory indicators (UA, eGFR, underexcretion, GLU, TRIG, HDL-C, ALT, TBIL, γ-GT and UPH) were included to evaluate the relationship between tophaceous gout and metabolic markers.

RESULTS

Tophi was present in 14.7% (119/808) of gout patients. UA, eGFR, ALT and γ-GT were independently related to the development of tophi; UA and γ-GT were positively correlated. The γ-GT/ALT ratio and UA/eGFR ratio showed a positive correlation with tophi, with (rho, P) of (0.305, < 0.001) and (0.195, < 0.001), respectively. The γ-GT/ALT ratio showed the best classificatory performance (AUC = 0.749, P < 0.001) for tophi among the four positive correlation indicators. With increasing integer γ-GT/ALT ratio, the incidence of tophi (4.9%, 9.7%, 22.3% and 38.4%, P < 0.001), chronic kidney disease (2.5%, 5.2%, 12.3% and 19.2%, P < 0.001) and hyperuricemia over 10 years (6.6%, 10.7%, 18.5% and 26.4%, P < 0.001) showed a progressive increase. The γ-GT/ALT ratio was positively correlated with the number of tophi and duration of hyperuricemia, negatively correlated with eGFR.

CONCLUSIONS

UA, eGFR, γ-GT and ALT were independently associated with tophi. The γ-GT/ALT ratio may be used as a predictor or monitor of tophi.

Identification and characterization of peripheral vascular color-coded DECT lesions in gout and non-gout patients: The VASCURATE study

OBJECTIVE

To characterize peripheral vascular plaques color-coded as monosodium urate (MSU) deposition by dual-energy computed tomography (DECT) and assess their association with the overall soft-tissue MSU crystal burden.

METHODS

Patients with suspected crystal arthropathies were prospectively included in the CRYSTALILLE inception cohort to undergo baseline knees and ankles/feet DECT scans; treatment-naive gout patients initiating treat-to-target urate-lowering therapy (ULT) underwent repeated DECT scans with concomitant serum urate level measurements at 6 and 12 months. We determined the prevalence of DECT-based vascular MSU-coded plaques in knee arteries, and assessed their association with the overall DECT volumes of soft-tissue MSU crystal deposition and coexistence of arterial calcifications. DECT attenuation parameters of vascular MSU-coded plaques were compared with dense calcified plaques, control vessels, control soft tissues, and tophi.

RESULTS

We investigated 126 gout patients and 26 controls; 17 ULT-naive gout patients were included in the follow-up study. The prevalence of DECT-based vascular MSU-coded plaques was comparable in gout patients (24.6%) and controls (23.1%; p=0.87). Vascular MSU-coded plaques were strongly associated with coexisting arterial calcifications (p<0.001), but not with soft-tissue MSU deposition. Characterization of vascular MSU-coded plaques revealed specific differences in DECT parameters compared with control vessels, control soft tissues, and tophi. During follow-up, vascular MSU-coded plaques remained stable despite effective ULT (p=0.64), which decreased both serum urate levels and soft-tissue MSU volumes (p<0.001).

CONCLUSION

Our findings suggest that DECT-based MSU-coded plaques in peripheral arteries are strongly associated with calcifications and may not reflect genuine MSU crystal deposition. Such findings should therefore not be a primary target when managing gout patients.

Urate Crystals; Beyond Joints

Gout is the most common inflammatory arthropathy caused by the deposition of monosodium urate (MSU) crystals. The burden of gout is substantial with increasing prevalence of gout globally. The prevalence of Gout in the United States has increased by over 7% in the last two decades. Initially, it was believed that MSU crystal deposits occur only in the joints with the involvement of the periarticular soft tissues, but recent studies have shown the presence of MSU crystal deposition in extra-articular sites as well. Human plasma becomes supersaturated with uric acid at 6.8 mg/dl, a state called hyperuricemia. Beyond this level, uric acid crystals precipitate out of the plasma and deposit in soft tissues, joints, kidneys, etc. If left untreated, hyperuricemia leads to chronic gout characterized by the deposition of tophi in soft tissues such as the joints, tendons, and bursae. With the advent of newer imaging techniques such as DECT, MSU crystals can be visualized in various extra-articular sites. Extra-articular deposition of MSU crystals is believed to be the causative factor for the development of multiple comorbidities in gout patients. Here, we review the literature on extra-articular deposition of urate crystals and the role of dual-energy computed tomography (DECT) in elucidating multi-organ involvement. DECT has emerged as an invaluable alternative for accurate and efficient MSU crystal deposition detection. Future studies using DECT can help determine the clinical consequences of extra-articular deposition of MSU in gout patients.

Uric Acid and Hypertension: Prognostic Role and Guide for Treatment

The relationship between serum uric acid (SUA) and hypertension has been a subject of increasing interest since the 1870 discovery by Frederick Akbar Mahomed. Several epidemiological studies have shown a strong association between high SUA levels and the presence or the development of hypertension. Genetic analyses have found that xanthine oxidoreductase (XOR) genetic polymorphisms are associated with hypertension. However, genetic studies on urate transporters and Mendelian randomization studies failed to demonstrate a causal relationship between SUA and hypertension. Results from clinical trials on the role of urate-lowering therapy in the management of patients with hypertension are not uniform. Our study sought to analyze the prognostic and therapeutic role of SUA in the hypertensive disease, from uric acid (UA) biology to clinical trials on urate-lowering therapies.