Recent advances in understanding and managing gout

Pathophysiology of hyperuricemia and its clinical significance - a narrative review

Hyperuricemia, i.e. increased serum uric acid (UA) concentration, is a common problem in clinical practice. While there are clear guidelines concerning management of symptomatic hyperuricemia in acute conditions such as gout, urolithiasis or acute urate nephropathy, less is known about their secondary prevention. Moreover, despite the ongoing debate on the role of UA in the pathogenesis of chronic kidney disease, hypertension, cardiovascular disease and heart failure, the management of asymptomatic hyperuricemia in patients with these chronic conditions is still mainly up to physicians' judgement. Individual considerations should always be taken into account when prescribing urate-lowering therapy. In this narrative review study, we attempt to present current trends concerning treatment of patients with either symptomatic or asymptomatic hyperuricemia in the light of the available knowledge on the role of hyperuricemia in the development of gout, renal, cardiovascular and other diseases.

Association Between Gout and Injury Risk: A National Retrospective Cohort Study

The association between gout and injury remains unclear. This study aimed to investigate the injury risk in patients with gout. Using the Longitudinal Health Insurance Database (LHID) from 2000 to 2010 in Taiwan, patients with gout (group CFG) and those without gout (group C) were enrolled for further analysis. The CFG group was separated into two subgroups (with and without medication) to determine whether the risk of injury was reduced with drug intervention. The follow-up period was defined as the time from the initial diagnosis of gout to the date of injury. A total of 257,442 individuals were enrolled in this study, with 85,814 people in group CFG and 171,628 people in group C. Using Cox regression analysis, group CFG showed a significant increase in the risk of injury. Traffic injuries, poisoning, falls, crushing/cutting/piercing injury, and suicides were prominent among these injuries. Furthermore, when urate-lowing drugs were used to treat the CFG group, there were no significant differences in the occurrence of injury. Patients with gout had an increased risk of injury overall, and drug intervention did not lower the risk of injury in these patients.

Patients Prescribed Anakinra for Acute Gout Have Baseline Increased Burden of Hyperuricemia, Tophi, and Comorbidities, and Ultimate All-Cause Mortality

Objective:

The interleukin-1 (IL-1) receptor antagonist anakinra is an effective, off-label option in acute gout flares, when conventional therapy options are narrowed. We performed a retrospective, randomized, case-controlled study to gain clinical insight on baseline factors for gout patients most likely to receive anakinra, and ultimate mortality of those who received anakinra.

Methods:

Of 1451 gout patients seen between January 2003 and January 2015 in a Veterans Affairs (VA) rheumatology group practice, under stringent managed care principles, 13 (100% male), who received anakinra at least once for flares, were compared with 1:4 age- and sex-matched gout controls. Each patient’s first rheumatology encounter was studied by factor analysis for variables associated with later anakinra.

Results:

At baseline, patients that received anakinra had higher urate burden (palpable tophi [10/13] vs controls [16/52], P = .003), serum urate ([10.6 mg/dL] vs controls [7.6 mg/dL], P < .0001), and East Asian descent ([7/13] vs [16/52], P = .041). The anakinra group had higher ultimate all-cause mortality ([6/13] vs controls [7/52], relative risk [RR] = 3.43, 95% confidence interval [CI] = 1.39-8.48, P = .0076). Factor analysis showed baseline visit palpable tophus and statin use to be most strongly associated with later anakinra use. Increased mortality of anakinra users, as per a factorial analysis, was linked more strongly to comorbidities than to anakinra.

Conclusions:

At baseline rheumatology gout encounter, higher urate, palpable tophi, statin prescription, and East Asian descent were associated with later anakinra use for flares. Mortality was more closely associated to the presence of comorbidities at baseline rheumatology visit than to anakinra prescription.

Toxicological Evaluation of Saposhnikoviae Radix Water Extract and its Antihyperuricemic Potential

Although the dried root of Saposhnikovia divaricata (Turcz.) Schischk. (Umbelliferae) is a popular medicinal plant in East Asia, there has been no systemic toxicological evaluation of a water extract of Saposhnikoviae Radix (SRE). In this experiment, an oral acute and 13-week subchronic toxicological evaluations of SRE (500–5,000 mg/ kg body weight) were performed in both sexes of Crl:CD(SD) rats. Based on the results from mortality, clinical signs, effects on body weight and organ weight, clinical biochemistry, hematology, urinalysis, and histopathology, significant acute, 4-week repeated dose range finding (DRF) and 13-week subchronic toxicity of SRE was not observed in either sex of rats; thus, the no observed adverse effect level (NOAEL) was 5,000 mg (kg/day). To identify anti-hyperuricemia potential of SRE, the suppressive effect of SRE was determined in mice challenged with potassium oxonate (PO; 250 mg/kg) via intraperitoneal injection for 8 days (each group; n = 7). SRE supplementation suppressed the uric acid level in urine through significant xanthine oxidase (XO) inhibitory activity. Kidney dysfunctions were observed in PO-challenged mice as evidenced by an increase in serum creatinine level. Whereas, SRE supplementation suppressed it in a dose-dependent manner. Collectively, SRE was safe up to 5,000 mg (kg/day) based on NOAEL found from acute and 13-week subchronic toxicological evaluations. SRE had anti-hyperuricemia effect and lowered the excessive level of uric acid, a potential factor for gout and kidney failure.

Freeze-Dried Self-Nanoemulsifying Self-Nanosuspension (SNESNS): a New Approach for the Preparation of a Highly Drug-Loaded Dosage Form

Febuxostat suffers from relatively low bioavailability owing to the poor drug solubility and hepatic first-pass effect. This study aimed to prepare highly drug-loaded self-nanoemulsifying self-nanosuspension systems (SNESNS). SNESNS were designed to improve febuxostat's oral bioavailability by enhancing its solubility. Different oil and surfactant/co-surfactant mixtures were used for the preparation of SNESNS. The prepared SNESNS were estimated for their particle size, in vitro drug release and transmission electron microscopy (TEM). Results revealed that the oil mixture of Capryol™ 90:Miglyol^® 812 (1:1 w/w) with surfactant/co-surfactant mixture of Cremophor^® RH 40/Transcutol^® HP loaded with drug in 4-fold greater concentration than its saturated solubility resulted in the formation of SNESNS by dilution under the effect of magnetic stirring. SNESNS were freeze-dried using trehalose as a cryoprotectant. TEM images and the bimodal particle size curve confirmed the formation of the biphasic nanosystems after dilution (nanoemulsion and nanosuspension). Higher C_max and AUC_0-48 values compared to those of the market product Feburic^® tablets confirmed the success of the SNESNS as a promising carrier for drugs suffering from poor water solubility like febuxostat.

Efficacy of uric acid-lowering therapy on hypercholesterolemia and hypertriglyceridemia in gouty patients

AIM

To investigate the effects on hypercholesterolemia and hypertriglyceridemia in gouty patients receiving uric acid-lowering therapy (UALT).

METHODS

A retrospective study was performed from January 2015 to December 2017 in gouty patients receiving UALT. A total of 124 gouty patients with hypercholesterolemia or hypertriglyceridemia who were administered UALT were monitored. Of the 124 patients with gout, 52 were treated with febuxostat, 29 were treated with allopurinol, and 43 were treated with benzbromarone. Cholesterol and triglyceride levels were recorded and analyzed following treatment for 8-10 weeks.

RESULTS

We compared the efficacy of febuxostat, allopurinol, and benzbromarone. All therapies mildly influenced serum cholesterol and triglyceride levels. Febuxostat significantly decreased cholesterol and triglyceride levels in patients who did not receive lipid-lowering therapy. Allopurinol and benzbromarone modestly decreased triglyceride levels, but cholesterol levels were unaffected.

CONCLUSION

Uric acid-lowering therapy benefits hyperlipidemia in gouty patients. Febuxostat effectively improved serum cholesterol and triglyceride levels compared to allopurinol and benzbromarone in patients with gout.

Pegloticase Treatment Significantly Decreases Blood Pressure in Patients With Chronic Gout

Serum urate is correlated with blood pressure (BP), and lowering urate may decrease BP, but a consistent effect has not been observed. Here, we evaluated whether pegloticase, a recombinant uricase conjugated to polyethylene glycol, which can lead to persistently low serum urate levels (<1 mg/dL), can modulate BP in subjects with chronic refractory gout. This post hoc analysis used results from two 6-month randomized clinical trials in which subjects were treated with 8 mg pegloticase every 2 or 4 weeks (q2w or q4w) or placebo. Responders in this study were defined as those individuals in whom a persistently low urate level (<6 mg/dL and usually <1 mg/dL) was maintained. Serial sitting BP was measured in 173 subjects, and estimated glomerular filtration rate was determined at baseline and after 3 and 6 months. Significant reductions in mean arterial pressure (MAP) from baseline to 6 months were noted in q2w responders ( P=0.0028), whereas reductions in MAP in other groups were not significant. Significant decreases in both systolic and diastolic BP paralleled the change in MAP. Of the 62% of q2w responders exhibiting persistent decreases in MAP, there were no significant differences in baseline age, sex, race, weight, body mass index, history of hypertension, hyperlipidemia, history of coronary artery disease, gout duration, MAP, serum urate, estimated glomerular filtration rate or urinary uric acid/creatinine ratio compared with those who did not lower MAP. No significant changes in estimated glomerular filtration rate occurred in any of the groups during the study. Responders to biweekly pegloticase who maintained a persistently lower serum urate level throughout the trial experienced significant reductions in both systolic and diastolic BP that were independent of changes in renal function. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00325195.

4-(2-(4-chlorophenyl)-1-((4-chlorophenyl)amino)ethyl)benzene-1, 3-diol is a potential agent for gout therapy as a dual inhibitor of XOD and NLRP3

BACKGOUND

Gout is an inflammatory arthritis characterized by abrupt self-limiting attacks of inflammation caused by precipitation of monosodium urate crystals (MSU) in the joint. Both anti-hyperuricemia and anti-inflammation could be gout therapeutic strategies, whereas ideal drugs for gout treatment are deficient.

PURPOSE

4-(2-(4-chlorophenyl)-1-((4-chlorophenyl)amino)ethyl)benzene-1, 3-diol (CBED) was obtained from a cluster of deoxybenzoins derivatives synthesized by our research group with potent anti-hyperuricemic and anti-inflammatory activities, which was expected to be a dual inhibitor of xanthine oxidase (XOD) and NOD-like receptor protein 3 (NLRP3). This study aimed to investigate effects of CBED on XOD and NLRP3 in vitro, as well as the possible mechanisms by which CBED improved gout in vivo.

METHODS

After molecular docking detection, inhibitory effects of CBED on XOD and NLRP3 were evaluated in vitro. Subsequently, hyperuricemia and acute gouty arthritis animal models were established by potassium oxonate or MSU, respectively. After CBED treatment, serum uric acid levels, synovial interleukin (IL)-1β concentrations, hepatic XOD activities, as well as synovial morphological changes were examined. More importantly, synovial expressions of NLRP3 inflammasome components including NLRP3, apoptosis-associated speck-like protein (ASC) and caspase-1 in rats were analyzed by immunofluorescence and western blot.

RESULTS

In vitro, CBED obviously inhibited XOD activity with an IC₅₀ value of 3.87 µM, moreover, it effectively inhibited MSU-induced NLRP3 inflammasome activation and IL-1β over-production in THP-1 cells. In addition, CBED dose-dependently decreased serum uric acid levels suppressed hepatic XOD activities in oxonate-induced hyperuricemic mice. On the other hand, CBED significantly improved MSU-induced ankle swelling and histopathological damage with elevated IL-1β. In addition, NLRP3 inflammasome activation could be blocked by CBED treatment in rats with acute gouty arthritis. Notbly, CBED exhibited no effects on all these indicators in normal animals, predicting its safety.

CONCLUSIONS

CBED might serve as a dual XOD and NLRP3 inhibitor for treatment of gout.

Impaired arterial responsiveness in untreated gout patients compared with healthy non-gout controls: association with serum urate and C-reactive protein

To determine whether arterial responsiveness is impaired among patients with gout, and whether arterial responsiveness inversely correlates with serum urate and inflammatory measures. This is a cross-sectional study of untreated gout subjects (n = 34) and non-gout healthy controls (n = 64). High-resolution dynamic ultrasound-measured flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) assessed endothelium-dependent and endothelium-independent arterial responsiveness respectively. Serum urate (sUA) and high-sensitivity C-reactive protein (hsCRP) were measured in the gout group, and correlated with FMD and NMD responses. Both FMD (2.20 ± 0.53 vs 3.56 ± 0.31, p = 0.021) and NMD (16.69 ± 1.54 vs 24.51 ± 0.90, p = 0.00002) were impaired in the gout versus control group. Stratification for individual comorbidities suggested that no single risk factor accounted for impaired FMD/NMD in the gout subjects. However, the degree of association between gout and FMD, but not NMD impairment, was dampened after multivariable adjustment (FMD unadjusted beta = - 1.36 (SE 0.58), p = 0.02; adjusted beta = - 1.16 (SE 0.78), p = 0.14 and NMD unadjusted beta = - 7.68 (SE 1.78), p < 0.0001; adjusted beta = - 5.33 (SE 2.46), p = 0.03). Within the gout group, there was an inverse correlation between FMD and sUA (R = - 0.5, p = 0.003), and between FMD and hsCRP (R = - 0.42, p = 0.017), but not between NMD and sUA or hsCRP. Compared with healthy controls, subjects with gout have reduced arterial function. Individual comorbidities are insufficient to account for differences between gout and control groups, but multiple comorbidities may collectively contribute to impairment in endothelium-dependent arterial responsiveness. Endothelial impairment is also related to sUA and hsCRP, markers of gout severity and inflammation respectively. Studies to determine whether gout therapy may improve arterial responsiveness are warranted.