From hyperuricaemia to gout: what are the missing links?

Early-onset gout

Early-onset gout (EOG) is characterized by the occurrence of the first symptoms of gout at an unusually young age, usually <40 years. The aim of this review is to provide an overview of the epidemiology, clinical presentation and prognosis, association with comorbidities and specific management of EOG. A particularly high proportion of patients with EOG come from ethnic groups with stronger genetic factors, such as populations in the Pacific and Taiwan, who therefore have the highest prevalence of gout overall. The clinical presentation and severity of gout are broadly similar between EOG and common gout, although a longer disease duration exacerbates the disease, which more often tends to become polyarticular. Patients suffering from EOG develop metabolic comorbidities commonly associated with gout earlier in life, although those tend to be less frequent at the time of diagnosis. Some international guidelines recommend early treatment of EOG patients with urate-lowering therapies.

The potential influence of high uric acid exposure on surface and corrosion susceptibility of pure titanium

This study investigated the corrosion susceptibility of pure titanium under uric acid exposure for 7 days based on surface analysis. The prepared pure titanium specimens, exposed to different concentrations of uric acid, were examined for surface microstructure, surface element composition and surface wettability using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and static contact angle measurement, respectively. The corrosion behaviors of titanium specimens were measured by open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The titanium ion release from the prepared specimens, which were immersed in Hank's balanced salt solution (HBSS) containing different amount of uric acid, was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). More irregular pitting holes were observed on titanium surfaces exposed to a high concentration of uric acid, and XPS analyses revealed that the amount of titanium dioxide (TiO₂) decreased. Titanium surfaces pre-treated with high uric acid became more hydrophobic. Furthermore, the results of OCP and potentiodynamic polarization tests showed increased corrosion susceptibility of titanium samples, while EIS data indicated more active corrosion behavior of titanium materials. The high concentration of uric acid also induced titanium ion release. High concentration of uric acid negatively influenced the surface characteristics and corrosion properties of titanium materials, which destroyed the titanium oxide film barrier. High uric acid exposure increased corrosion susceptibility of pure titanium specimens and accelerated titanium ion release. Graphical abstract.

Lactic acid bacteria strains relieve hyperuricaemia by suppressing xanthine oxidase activity via a short-chain fatty acid-dependent mechanism

Globally, the incidence of hyperuricaemia is steadily increasing. The evidence increasingly suggests an association between hyperuricaemia and the gut microbiota, which may enable the development of a novel therapeutic approach. We studied the effects of treatment with lactic acid bacteria (LAB) on hyperuricaemia and their potential underlying mechanisms. A mouse model of hyperuricaemia was generated by oral gavage with hypoxanthine and intraperitoneal injections of potassium oxonate for 2 weeks. The anti-hyperuricaemic activities of 10 LAB strains relative to allopurinol as a positive drug control were investigated in the mouse model. Lactobacillus rhamnosus R31, L. rhamnosus R28-1 and L. reuteri L20M3 effectively reduced the uric acid (UA) concentrations in serum and urine and the xanthine oxidase (XOD) activity levels in serum and hepatic tissue in mice with hyperuricaemia. These strains also reversed the elevated lipopolysaccharide (LPS) concentration, hepatic inflammation and slight renal injury associated with hyperuricaemia. A correlation analysis revealed that UA-reducing LAB strains promoted short-chain fatty acid (SCFA) production to suppress serum and hepatic XOD activity by increasing the abundances of SCFA production-related gut bacterial taxa. However, the UA-reducing effects of LAB strains might not be mediated by purine degradation. In summary, L. rhamnosus R31, L. rhamnosus R28-1 and L. reuteri L20M3 relieved hyperuricaemia in our mouse model by promoting SCFA production in a purine degradation-independent manner. Our findings suggest a novel therapeutic approach involving LAB strains for hyperuricaemia.

Hyperuricemia and Its Associated Factors Among Adult Staff Members of the Ethiopian Public Health Institute, Ethiopia

Background

Hyperuricemia is related not only to an increased risk of gouty arthritis but also to an increased risk of cardiovascular diseases, resistant hypertension, insulin resistance and progression of type 2 diabetes mellitus. However, to the best of our knowledge, the prevalence of hyperuricemia and its associated factors have rarely been assessed in Ethiopian populations. Therefore, this study aimed to determine the prevalence of hyperuricemia and its associated factors among adult staff members of the Ethiopian Public Health Institute.

Methods

An institution-based cross-sectional study was conducted from July 1 to October 28, 2018. A total of 402 study participants were selected using a simple random sampling technique. An interviewer-administered questionnaire was used to collect the data. A blood sample of approximately 5 mL was collected from each study participant after overnight fasting through standardized methods for biochemical tests, and analyses were carried out with an automated COBAS 6000 analyzer. Data analysis was performed by SPSS version 20 software. The factors associated with the outcome variable were identified by bivariable and multivariable logistic regression analyses, and a p value <0.05 was used to declare statistical significance.

Results

The mean age of the study participants was 37.13±10.5 (mean ± SD), and 51.5% of the participants were male. The overall prevalence of hyperuricemia (>5.7 mg/dL for females and >7 mg/dL for males) was found to be 31.0%. The multivariable logistic analysis revealed that age (AOR=1.59, 95% CI 1.01–2.78), sex (AOR=1.66, 95% CI 1.02–2.70), cigarette smoking (AOR=2.05, 95% CI 1.01–4.19) and serum low-density lipoprotein (LDL) (AOR=1.70, 95% CI 1.01–2.87) were significantly associated with hyperuricemia.

Conclusion

The prevalence of hyperuricemia was relatively high compared to similar studies. Early screening for hyperuricemia in the general population, especially in those who are smokers, of older age and with high serum LDL levels, is vital to control its adverse effects at an early stage.

Effect modification of hyperlipidemia and hypertension on the association between type 2 diabetes and gout

AIMS

We evaluated the association between type 2 diabetes and gout by a retrospective cohort study.

METHODS

Data of 17,259 male and 18,318 female patients with type 2 diabetes were retrieved for the 1998-2010 period. These patients were matched to a comparison group (n=34,518 and n=36,636, respectively) in a 1:2 ratio by age and region.

RESULTS

We found that patients with type 2 diabetes after adjustment for hyperlipidemia and hypertension had a lower risk of incident gout than the matched population (incidence rate ratio, men: 0.39 [95% CI: 0.36-0.42]; women: 0.78 [0.72-0.84]). Specifically, type 2 diabetes alone without hyperlipidemia and hypertension was associated with a reduced risk of incident gout in men (adjusted relative risk [RR]: 0.29, 95% CI: 0.22-0.39), but not in women (0.86, 95% CI: 0.55-1.36). We found that insulin users with hyperlipidemia and hypertension associated with risk of incident gout and no sex-specific differences were noted (adjusted RR, men: 1.28 [95% CI: 1.11-1.48]; women: 1.32 [95% CI: 1.14-1.53]). Specifically, insulin users alone without hyperlipidemia and hypertension were not statistically significantly associated with gout risk (P≥.0954).

CONCLUSIONS

The results of this study indicated that hyperlipidemia and hypertension modified the association between type 2 diabetes and gout.

Toll-Like receptor 4 (TLR4) polymorphism rs2149356 and risk of gout in a Spanish cohort

Gout is the most common arthritis and it is associated to urate monosodium crystals deposits in articulations, kidney and soft tissue. The urate monosodium crystals deposit initiates an inflammatory response; mediated by NLRP3 inflammasome, with the release of interleukin 1β. Toll-like receptor 4 (TLR4) is involved in this response. Although serum urate level is a strong predictor of incident gout, only about half of those with serum urate concentrations ≥10mg/dL develop clinically evident gout over 15 years. Therefore, it has been postulated that other factors, including genetic or immunity related factors, seems to be necessary to the apparition of the acute gout flare beside hyperuricemia. The association of TLR4 single nucleotide polymorphism (SNP) rs2149356 and gout risk is controversial with different results according to different populations.Methods: We have analyzed rs2149356 polymorphism of TLR4 gene in DNA extracted from 125 well characterized Caucasian gouty patients and 300 Caucasian health controls, by automated DNA sequencing.Results: Allele frequency distribution in control samples were CC: 0.467 (140); CA 0.437 (131); and AA 0.097 (29).Allele distribution in gouty patients were CC: 0.512 (64); CA: 0.392 (49); and AA: 0.096 (12). No significant association was found between TRL4 rs2149356 polymorphism and risk of gout in the analyzed population.Conclusions: Allele frequency for rs2149356 in our population was similar to other population of European ancestry, and in these populations; the polymorphism was not related to gouty risk.

Increased urinary glucose excretion is associated with a reduced risk of hyperuricaemia

AIM

To investigate the association of urinary glucose excretion with levels of serum uric acid in adults with newly diagnosed diabetes.

METHODS

A total of 597 people with newly diagnosed diabetes, confirmed in an oral glucose tolerance test, were included in the present study. The participants were divided into two groups: 142 participants with low urinary glucose excretion and 455 with high urinary glucose excretion. Demographic characteristics and clinical variables were evaluated. The association of urinary glucose excretion with uric acid was analysed using multivariable regression analysis.

RESULTS

The low urinary glucose excretion group had a significantly higher prevalence of hyperuricaemia than the high urinary glucose excretion group. Moreover, urinary glucose excretion was negatively associated with uric acid level. The correlation remained significant after adjusting for potential confounders, including gender, age, fasting plasma glucose, 2-h plasma glucose and BMI. The results also showed that participants with high urinary glucose excretion were at decreased risk of hyperuricaemia (odds ratio 0.47, 95% CI 0.27-0.80; P = 0.006).

CONCLUSION

Urinary glucose excretion was independently associated with uric acid level in participants with newly diagnosed diabetes. In addition to lowering blood glucose, promoting urinary glucose excretion may also be an effective approach to reducing serum uric acid levels, especially for people with diabetes complicated with hyperuricaemia.

How should we manage asymptomatic hyperuricemia?

The definition of asymptomatic hyperuricemia remains unclear, as no consensus exists about the serum urate cutoff or the relevance of ultrasound findings. Comorbidities associated with hyperuricemia have increased in frequency over the past two decades. Hyperuricemia (and/or gout) may be a cause or a consequence of a comorbidity. Whereas epidemiological studies suggest that hyperuricemia may be linked to cardiovascular, metabolic, and renal comorbidities, Mendelian randomization studies have not provided proof that these links are causal. Discrepancies between findings from observational studies and clinical trials preclude the development of recommendations about the potential benefits of urate-lowering therapy (ULT) in individual patients with asymptomatic hyperuricemia. The risk/benefit ratio of ULT is unclear. The risk of developing gout, estimated at 50%, must be weighed against the risk of cutaneous and cardiovascular side effects of xanthine oxidase inhibitors. The need for optimal comorbidity management, in contrast, is universally accepted. Medications for comorbidities that elevate urate levels should be discontinued and replaced with medications that have the opposite effect. Therapeutic lifestyle changes, weight loss as appropriate, and sufficient physical activity are useful for improving general health. Whether ULT has beneficial effects on comorbidities will be known only when well-powered interventional trials with relevant primary endpoints are available.