The uric acid metabolism pathway as a therapeutic target in hyperuricemia related to metabolic syndrome

Analysis of uric acid and high-density lipoprotein levels in refractory posner-schlossman syndrome patients: a matched case-control study by the propensity score

BACKGROUND

Recent studies have indicated that oxidative stress is a crucial pathophysiological process in glaucoma. We hypothesized that Posner-Schlossman syndrome (PSS) is a vascular inflammation in the ciliary body due to oxidative stress and endothelial dysfunction. Thus, we investigated serum uric acid (UA) and lipid levels in patients with refractory PSS with the aim of providing basic evidence for the mechanism of PSS.

METHODS

This is a retrospective, case-control study. A total of 81 refractory PSS and 409 control participants were included in this study. Clinical and laboratory characteristics were reviewed using an electronic medical system. Propensity score-matched (PSM) analysis was performed to reduce demographic differences. The t-test, Mann-Whitney U test, and χ2 test were used to assess the differences between the PSS and control groups. Logistic regression analysis was used to identify the predictors of PSS.

RESULTS

The higher serum UA (364.14 ± 98.72µmol/L vs. 322.38 ± 72.09µmol/L), higher low-density lipoprotein (LDL) / High-density lipoprotein (HDL) ratio (2.50 ± 0.97 vs. 1.95 ± 0.72) and lower HDL (1.29 ± 0.32 mmol/L vs. 1.59 ± 0.38 mmol/L) can be noticed in refractory PSS than control group. Logistics regression identified UA > 420 µmol/L (OR = 4.461) and the HDL < 1.03 mmol/L (OR = 3.896) were the independent risk factors for refractory PSS.

CONCLUSIONS

Increasing serum UA and decreasing HDL levels were positively correlated with the incidence risk of refractory PSS. Further prospective longitudinal studies and animal models are needed.

L-shaped relationship between atherogenic index of plasma with uric acid levels and hyperuricemia risk

Background

Hyperuricemia is a major risk factor for cardiovascular disease. This study aimed to investigate the relationship between the atherogenic index of plasma (AIP) and serum uric acid (SUA) levels, as well as the risk of hyperuricemia.

Methods

Utilizing data from the National Health and Nutrition Examination Survey (NHANES), we conducted a cross-sectional study involving 9,439 participants aged 18 years and above with complete triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) data. AIP was calculated as the logarithm of the ratio of TG to HDL-C. Weighted linear regression, weighted logistic regression, subgroup analysis, generalized additive model, restricted cubic spline and two-part linear and logistic regression were utilized to examine the relationships between AIP and SUA levels and hyperuricemia risk.

Results

We identified a non-linear and L-shaped relationship between AIP and both SUA levels and hyperuricemia prevalence, with significant increasing observed up to a saturation point (0.588 for uric acid levels and 0.573 for hyperuricemia prevalence). Below these thresholds, the odds ratios (OR) for increased SUA and hyperuricemia were 0.854 (95% confidence interval [CI]: 0.762, 0.946) and 4.4 (95% CI: 3.528, 5.488), respectively (P<0.001). Beyond these points, the associations were not statistically significant.

Conclusion

Our findings suggest that AIP is significantly and non-linear associated with SUA levels and hyperuricemia risk, with a saturation effect observed beyond specific thresholds. These insights could inform clinical strategies for managing cardiovascular and metabolic risks associated with elevated AIP. Further longitudinal studies are warranted to confirm these associations and elucidate the underlying mechanisms.

Lowering the risk of hyperuricemia and gout is associated with ideal cardiovascular health

BACKGROUND

Hyperuricemia (HUA) and gout have been demonstrated as independent risk factors for cardiovascular disease. The relationship between the recently updated Life's Essentials 8 (LE8), which measures ideal cardiovascular health (CVH), and HUA and gout remains unclear. The aim of this study was to explore the relationship between CVH and the prevalence of HUA and gout among a nationally representative sample of US adults.

METHODS

This study utilized cross-sectional analysis of data from the National Health and Nutrition Examination Survey (NHANES) for the years 2007 to 2018. The CVH scores and their corresponding components were defined according to the guidelines established by the American Heart Association. The association between the LE8 score and both HUA and gout was assessed using weighted multivariable logistic and restricted cubic spline (RCS) models.

RESULTS

Among the 21,155 participants aged 20 years and older, the prevalence of HUA was 17.20% (95% CI, 16.05-18.36%), and the prevalence of gout was 3.58% (95% CI, 3.13-4.02%). After adjusting for potential confounders, compared to participants exhibiting low CVH, the multivariable adjusted odds ratio (OR) for HUA was 0.65 (95% CI, 0.56-0.75) in those with moderate CVH, and 0.25 (95% CI, 0.20-0.31) in those with high CVH. Additionally, compared to participants with low CVH, the multivariable adjusted OR for gout was 0.66 (95% CI, 0.53-0.81) in those with moderate CVH and 0.32 (95% CI, 0.20-0.50) in those with high CVH. The LE8 score exhibited a significant nonlinear negative association with HUA and linear negative correlation with gout. In subgroup analyses focusing on HUA, significant interactions were observed between LE8 score and age, sex, and CKD (P for interaction < 0.05). For gout, only a significant interaction between LE8 score and sex was observed (P for interaction < 0.05).

CONCLUSIONS

Among adults, there was a significant negative correlation between LE8 score and the prevalence of HUA and gout. Maintaining an ideal CVH may be beneficial in reducing the burden of HUA and gout.

Polysaccharides from Alpinia oxyphylla fruit prevent hyperuricemia by inhibiting uric acid synthesis, modulating intestinal flora and reducing renal inflammation

Hyperuricemia (HUA) is one of the most common chronic diseases today, with a prevalence exceeding 14 % in both the United States and China. Current clinical treatments for HUA focus on promoting uric acid (UA) excretion and inhibiting UA production, but often neglect the strain on the liver and kidneys. The fruit of Alpinia oxyphylla (A. oxyphylla) is known to improve renal function, regulate metabolism, and exhibit anti-inflammatory effects; however, its effectiveness and mechanisms in treating HUA are not well understood. In this study, HUA mice induced by potassium oxonate and adenine were treated with A. oxyphylla polysaccharide (AFP) for 21 days. The levels associated with HUA were quantified using assay kits to evaluate the impact of AFP on HUA. Serum metabolomics and 16S rRNA sequencing were used to investigate the mechanisms by which AFP ameliorates HUA. The results showed that AFP treatment reduced abnormal biochemical levels, including UA, blood urea nitrogen, and creatinine, in HUA mice. AFP inhibited UA synthesis by regulating pyrimidine metabolism and the metabolism of alanine, aspartate and glutamate, reduced kidney inflammation, and promoted UA excretion by regulating intestinal flora. Thus, AFP appears to be an effective agent for alleviating HUA symptoms.

The effect of metformin on urate metabolism: Findings from observational and Mendelian randomization analyses

AIM

To evaluate the effect of metformin on urate metabolism.

MATERIALS AND METHODS

Using the UK Biobank, we first performed association analyses of metformin use with urate levels, risk of hyperuricaemia and incident gout in patients with diabetes. To explore the causal effect of metformin on urate and gout, we identified genetic variants proxying the glycated haemoglobin (HbA1c)-lowering effect of metformin targets and conducted a two-sample Mendelian randomization (MR) utilizing the urate and gout genetic summary-level data from the CKDGen (n = 288 649) and the FinnGen cohort. We conducted two-step MR to explore the mediation effect of body mass index and systolic blood pressure. We also performed non-linear MR in the UK Biobank (n = 414 055) to show the results across HbA1c levels.

RESULTS

In 18 776 patients with type 2 diabetes in UK Biobank, metformin use was associated with decreased urate [β = -4.3 μmol/L, 95% confidence interval (CI) -7.0, -1.7, p = .001] and reduced hyperuricaemia risk (odds ratio = 0.87, 95% CI 0.79, 0.96, p = .004), but not gout. Genetically proxied averaged HbA1c-lowering effects of metformin targets, equivalent to a 0.62% reduction in HbA1c, was associated with reduced urate (β = -12.5 μmol/L, 95% CI -21.4, -4.2, p = .004). Body mass index significantly mediated this association (proportion mediated = 33.0%, p = .002). Non-linear MR results suggest a linear trend of the effect of metformin on urate reduction across various HbA1c levels.

CONCLUSIONS

The effect of metformin may reduce urate levels but not incident gout in the general population.

Effect of metformin use on clinical outcomes and serum urate in gout patients with diabetes mellitus: a retrospective cohort study

Objective

Gout and diabetes mellitus type 2 (DM) frequently co-exist. The pharmacological effects of metformin may include anti-inflammatory and urate lowering effects. The objective of this study was to test these effects in patients with gout starting uric acid lowering treatment (ULT) in secondary care.

Methods

Retrospective cohort study including patients with gout and DM starting ULT. Differences in the incidence density of gout flares, proportion of patients reaching target sUA in the first six months after starting ULT, and difference in mean allopurinol dose at sUA target were compared between users of metformin and users of other or no anti-diabetic drugs (control group). Correction for confounding was applied.

Results

A total of 307 patients were included, of whom 160 (52.1%) used metformin. The incidence of flares was 1.61 and 1.70 in the first six months for respectively the metformin group and control group. The incidence rate ratio for gout flares was not significant (0.95, 95% CI 0.78 to 1.14). At six months, 62.8% and 54.9% reached target sUA in the metformin and control group respectively, corrected odds ratio of 1.09 (95% CI 0.66 to 1.80). There was no difference in mean allopurinol dose at sUA target 266 mg for metformin users and 236 mg for the control group, difference 30 mg (95% CI − 4.7 to 65.5).

Conclusions

In conclusion we could not confirm a clinically relevant anti-inflammatory or urate lowering effect of metformin in patients starting ULT treatment and receiving usual care flare prophylaxis.

Prognostic value of hyperuricemia for patients with sepsis in the intensive care unit

This study evaluated the relationship between hyperuricemia at admission and the clinical prognosis of patients with sepsis. The data were obtained from the Intensive Care Medical Information Database III. The patients were divided into a normal serum uric acid group and a hyperuricemia group. The main outcome was 90-day mortality, and the secondary outcomes were hospital mortality, 30-day mortality, and acute kidney injury. Propensity score matching was used to balance the baseline characteristics of the groups. Our study retrospectively included 954 patients. Before and after propensity score matching, the incidence of AKI, the 30-day and 90-day mortality rates were significantly higher in the hyperuricemia group. Cox regression analysis showed that hyperuricemia was significantly associated with 90-day mortality (HR 1.648, 95% CI 1.215–2.234, p = 0.006), and hyperuricemia was significantly associated with the incidence of AKI (HR 1.773, 95% CI 1.107–2.841, p = 0.017). The Kaplan–Meier survival curve showed that the 90-day survival rate was significantly lower in the hyperuricemia group. In patients with sepsis in the intensive care unit, hyperuricemia was significantly associated with increased risk 90-day all-cause mortality and the incidence of AKI.

Limosilactobacillus fermentum JL-3 isolated from "Jiangshui" ameliorates hyperuricemia by degrading uric acid

Recent studies into the beneficial effects of fermented foods have shown that this class of foods are effective in managing hyperuricemia and gout. In this study, the uric acid (UA) degradation ability of Limosilactobacillus fermentum JL-3 strain, isolated from "Jiangshui" (a fermented Chinese food), was investigated. In vitro results showed that JL-3 strain exhibited high degradation capacity and selectivity toward UA. After oral administration to mice for 15 days, JL-3 colonization was continuously detected in the feces of mice. The UA level in urine of mice fed with JL-3 was similar with the control group mice. And the serum UA level of the former was significantly lower (31.3%) than in the control, further confirmed the UA-lowering effect of JL-3 strain. Limosilactobacillus fermentum JL-3 strain also restored some of the inflammatory markers and oxidative stress indicators (IL-1β, MDA, CRE, blood urea nitrogen) related to hyperuricemia, while the gut microbial diversity results showed that JL-3 could regulate gut microbiota dysbiosis caused by hyperuricemia. Therefore, the probiotic Limosilactobacillus fermentum JL-3 strain is effective in lowering UA levels in mice and could be used as a therapeutic adjunct agent in treating hyperuricemia.

Serum Uric Acid and Diabetes: From Pathophysiology to Cardiovascular Disease

Hyperuricemia, has been traditionally related to nephrolithiasis and gout. However, it has also been associated with the development of type 2 diabetes mellitus (T2DM) and cardiometabolic and cardiovascular diseases. Pathophysiologically, elevated serum uric acid (SUA) levels may be associated with abnormal lipid and glucose metabolism. In this narrative review, we consider the associations between hyperuricemia, hyperglycemia, atherosclerosis and thrombosis. Furthermore, we comment on the available evidence linking elevated SUA levels with the incidence and outcomes of coronary heart disease, stroke, peripheral artery disease and non-alcoholic fatty liver in subjects with T2DM. The effects of antidiabetic drugs (e.g. metformin, pioglitazone, sulfonylureas, dipeptidyl peptidase 4 inhibitors, glucagon-like peptide-1 receptor agonists, sodium-glucose cotransporter 2 inhibitors and insulin) on SUA concentrations are also reviewed.

Dose-response relationship between distinct serum uric acid trajectories and metabolic syndrome risk: A 5-year prospective cohort study

BACKGROUND AND AIMS

Although high serum uric acid (SUA) at baseline has been linked to increased risk for metabolic syndrome (MetS), the association of longitudinal SUA changes with MetS risk is unclear. We aimed to examine the effect of distinct SUA trajectories on new-onset MetS risk by sex in a Chinese cohort.

METHODS AND RESULTS

A total of 2364 women and 2770 men who were free of MetS in 2013 were enrolled in this study and followed up to 2018. Group-based trajectory modeling was applied to identify SUA trajectories. Cox proportional hazards model was used to evaluate the association between SUA trajectory and new-onset MetS. The dose-response relationship between SUA trajectories and MetS risk was examined by treating trajectory groups as a continuous variable. During a median follow-up of 48.0 months, 311 (13.16%) women and 950 (34.30%) men developed MetS. SUA trajectories (2013-2018) were defined as four distinct patterns in both women and men: "low", "moderate", "moderate-high", and "high". Compared with "low" SUA trajectory, the adjusted hazard ratio for incident MetS among participants with "moderate", "moderate-high" and "high" trajectory was in a dose-response manner: 1.75 (95% CI: 1.08-2.82), 1.94 (95% CI: 1.20-3.14), and 3.05 (95% CI: 1.81-5.13), respectively, for women; 1.20 (95% CI: 0.97-1.49), 1.48 (95% CI: 1.19-1.85), and 1.66 (95% CI: 1.25-2.21), respectively, for men.

CONCLUSIONS

Elevated SUA trajectories are associated with increased risk for new-onset MetS in women and men. Monitoring SUA trajectories may assist in identifying subpopulations at higher risk for MetS.

The Role of Oxidative Stress in Hyperuricemia and Xanthine Oxidoreductase (XOR) Inhibitors

Uric acid is the end product of purine metabolism in humans. Hyperuricemia is a metabolic disease caused by the increased formation or reduced excretion of serum uric acid (SUA). Alterations in SUA homeostasis have been linked to a number of diseases, and hyperuricemia is the major etiologic factor of gout and has been correlated with metabolic syndrome, cardiovascular disease, diabetes, hypertension, and renal disease. Oxidative stress is usually defined as an imbalance between free radicals and antioxidants in our body and is considered to be one of the main causes of cell damage and the development of disease. Studies have demonstrated that hyperuricemia is closely related to the generation of reactive oxygen species (ROS). In the human body, xanthine oxidoreductase (XOR) catalyzes the oxidative hydroxylation of hypoxanthine to xanthine to uric acid, with the accompanying production of ROS. Therefore, XOR is considered a drug target for the treatment of hyperuricemia and gout. In this review, we discuss the mechanisms of uric acid transport and the development of hyperuricemia, emphasizing the role of oxidative stress in the occurrence and development of hyperuricemia. We also summarize recent advances and new discoveries in XOR inhibitors.

Serum uric acid is associated with increased risk of posttransplantation diabetes in kidney transplant recipients: a prospective cohort study

BACKGROUND

Serum uric acid (SUA) is associated with fasting glucose in healthy subjects, and prospective epidemological studies have shown that elevated SUA is associated with increased risk of type 2 diabetes. Whether SUA is independently associated with higher risk of posttransplantation diabetes mellitus (PTDM) in kidney transplant recipients (KTR) remains unknown.

METHODS

We performed a longitudinal cohort study of 524 adult KTR with a functioning graft ≥1-year, recruited at a university setting (2008-2011). Multivariable-adjusted Cox proportional-hazards regression analyses were performed to assess the association between time-updated SUA and risk of PTDM (defined according the American Diabetes Association's diagnostic criteria).

RESULTS

Mean (SD) SUA was 0.43 (0.11) mmol/L at baseline. During 5.3 (IQR, 4.1-6.0) years of follow-up, 52 (10%) KTR developed PTDM. In univariate prospective analyses, SUA was associated with increased risk of PTDM (HR 1.75, 95% CI 1.36-2.26 per 1-SD increment; P < 0.001). This finding remained materially unchanged after adjustment for components of the metabolic syndrome, lifestyle, estimated glomerular filtration rate, immunosuppressive therapy, cytomegalovirus and hepatitis C virus infection (HR 1.89, 95% CI 1.32-2.70; P = 0.001). These findings were consistent in categorical analyses, and robust in sensitivity analyses without outliers.

CONCLUSIONS

In KTR, higher SUA levels are strongly and independently associated with increased risk of PTDM. Our findings are in agreement with accumulating evidence supporting SUA as novel independent risk marker for type 2 diabetes, and extend the evidence, for the first time, to the clinical setting of outpatient KTR.

The visceral fat area to leg muscle mass ratio is significantly associated with the risk of hyperuricemia among women: a cross-sectional study

BACKGROUND

A significant positive association was found in previous studies among obesity, visceral fat accumulation, and hyperuricemia. The purpose of this study was to explore the association between the ratio of visceral fat area to leg muscle mass (VFA-to-LMM) and hyperuricemia, and verify the role of gender differences in the association.

METHODS

A total of 3393 (43.3% are men) participants from Tianjin Union Medical Center-Health Management Center were recruited for this cross-sectional study. The VFA-to-LMM ratio was used as the independent variable. Hyperuricemia, a serum uric acid level ≥ 416 μmol/L in men and in menopausal women and ≥ 357 μmol/L in premenopausal women, was used as the dependent variable. Multiple logistic regression analysis was used to estimate the odds ratio and the 95% confidence interval between the VFA-to-LMM ratio and hyperuricemia.

RESULTS

The overall prevalence of hyperuricemia was 14.8% (8.9% in women, and 22.5% in men). After adjustment by age, smoking status (for males), menopause status (for females), drinking status, exercise frequency, blood pressure, alanine aminotransferase, fasting plasma glucose, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, creatinine, and history of diseases, a strong positive association was found between the VFA-to-LMM ratio and hyperuricemia in both men (4th vs. 1st quartile 1.60, 95%CI: 1.03-2.49) and women (4th vs. 1st quartile 5.22, 95%CI: 2.44-12.56). After additional adjustment by BMI, there was still a significant positive association in women (4th vs. 1st quartile 2.57, 95%CI: 1.06-6.77). The results of subgroup analysis showed that pre-menopausal women (4th vs. 1st quartile OR: 3.61) have a higher risk of hyperuricemia than postmenopausal women (4th vs. 1st quartile OR: 1.94) with the increase of the VFA-to-LMM ratio. Besides, the interaction analysis results showed the highest risk of hyperuricemia when VFA and LMM were both in the highest quantile (OR: 11.50; 95% CI: 4.86-31.98).

CONCLUSION

The VFA-to-LMM ratio was positively associated with the risk of hyperuricemia in women after adjustment by confounders. Pre-menopausal women have a higher risk of hyperuricemia than postmenopausal women with the increase of the VFA-to-LMM ratio. In addition, the highest risk of hyperuricemia was demonstrated when both VFA and LMM were at the highest quartile.

Impact of Alpha-Lipoic Acid Chronic Discontinuous Treatment in Cardiometabolic Disorders and Oxidative Stress Induced by Fructose Intake in Rats

Insulin resistance (IR) and cardiometabolic disorders are the main consequences of today’s alimentary behavior. This study evaluates the effects of a chronic-discontinuous treatment with alpha-lipoic acid (AL), an antioxidant substance that improves glycemic control associated with diabetes mellitus, on metabolic disorders and plasma oxidative stress induced by fructose intake, in rats. Sprague-Dawley rats (48 animals) were randomized into two series (n = 24): rats fed with standard chow or with standard chow supplemented with 60% fructose. In each of the two series, for 2 weeks/month over 12 weeks, a group of rats (n = 12) was intraperitoneally injected with NaCl 0.9%, and a second group (n = 12) received AL 50 mg/kg/day. Body weight, glycemia, and systolic blood pressure were monitored throughout the study. After 12 weeks, IR, plasma lipoproteins, uric acid, transaminase activities, and oxidative stress markers were assessed. The high fructose-enriched diet induced cardiometabolic disorders (hypertension, hyperglycemia, IR and dyslipidemia), an increase in uric acid concentration, transaminase activities and C-reactive protein level. This diet also enhanced plasma products of lipid and protein oxidation, homocysteine level, and decreased GSH/GSSG ratio. In this field, there is evidence to indicate that oxidative stress plays an important role in the etiology of diabetic complications. AL discontinuous treatment prevents the metabolic disorders induced by fructose intake, reduced plasma lipid and protein oxidation-products, and restored the GHS/GSSG ratio. Our study proves a promising potential of the chronic-discontinuous treatment of AL and highlights the pleiotropic effects of this antioxidant substance in metabolic disorders such as diabetes.

Advanced Age and Chronic Kidney Disease Modify the Association Between Metabolic Syndrome and Frailty Among Community-Dwelling Elderly

Metabolic syndrome (MetS) predisposes older adults to the development of frailty. However, previous studies have not explored factors that may influence the association between MetS and the risk of frailty in this population. Community-dwelling older adults (≥65 years of age) were prospectively identified and enrolled between 2013 and 2016. MetS and frailty were defined based on the American Association of Clinical Endocrinologists and Study of Osteoporotic Fractures criteria, respectively. Multiple logistic regression with frailty/prefrailty as the dependent variable was used to examine the relationship between MetS and frailty/prefrailty, supplemented by subgroup analyses of the influence of aging and chronic kidney disease (CKD). Among 2862 elderly (73.4 ± 6.7 years), 17.5% and 17.3%, respectively, had MetS and frailty/prefrailty, among whom 74 (2.6%) and 420 (14.7%) had frailty and prefrailty. The presence of MetS (odds ratio [OR] 2.53, p < 0.001), higher age (OR 1.05, p < 0.001), and CKD (OR 1.42, p = 0.006) were associated with a significantly higher risk of frailty/prefrailty. Furthermore, among those ≥80 years of age, the association between MetS and frailty/prefrailty disappeared (p = 0.329). Among those with CKD, the presence of MetS was significantly associated with a progressively higher risk of frailty/prefrailty (for stage 3 or higher and for stage 3b or higher, OR 6.4 and 12.4, p < 0.001 and = 0.009, respectively). In conclusion, aging and CKD modified the association between MetS and frailty. These findings may assist in devising case-specific care plans for elderly with MetS by refocusing our attention on those at high risk of developing frailty/prefrailty.

Metabolic syndrome and the decreased levels of uric acid by leflunomide favor redox imbalance in patients with rheumatoid arthritis

Oxidative stress plays a role in the pathophysiology of rheumatoid arthritis (RA). The aim of the present study was to verify the influence of metabolic syndrome (MetS) and disease-modifying antirheumatic drugs on nitrosative and oxidative biomarkers in patients with RA. A total of 177 patients with RA and 150 healthy volunteers participated in this study, which measured lipid hydroperoxides, advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), carbonyl protein, total radical-trapping antioxidant parameter (TRAP), uric acid (UA), and C-reactive protein (CRP). NOx and the NOx/TRAP ratio were significantly increased in RA, while no significant differences in lipid hydroperoxides, AOPP, UA, and TRAP levels were found between both groups. Treatment with leflunomide was associated with increased levels of carbonyl protein, and lowered levels in TRAP and UA, while the NOx/TRAP ratio further increased. NOx and the NOx/TRAP ratio were significantly higher in women than in men, while TRAP and UA were significantly lower in women. MetS was accompanied by increased AOPP and UA levels. RA was best predicted by increased NOx/TRAP ratio, CRP, and BMI. In conclusion, our data demonstrated that NOx and NOx/TRAP are strongly associated with RA physiopathology. Our findings suggest that inhibition of iNOS may become an interesting therapeutic approach for the treatment of RA. In addition, the presence of MetS and a decrease in levels of UA by leflunomide favor redox imbalance in RA patients. More studies are needed to evaluate the impact of antioxidant capacity reduction on RA progression.

Elevated serum uric acid levels are associated with endothelial dysfunction in HIV patients receiving highly-active antiretroviral therapy

BACKGROUND AND AIMS

Elevated serum uric acid (SUA) levels may be associated with endothelial dysfunction. Increased rates of metabolic syndrome (MS) and elevated SUA levels were described in human immunodeficiency virus (HIV) infected patients. We investigated whether SUA levels are associated with endothelial dysfunction in HIV positive patients receiving highly-active antiretroviral therapy (HAART) irrespective of MS.

METHODS

In this cross-sectional study of 250 HIV positive patients receiving stable HAART, we evaluated the relationship between MS, SUA levels and endothelial function. SUA levels and brachial artery flow-mediated dilation (bFMD) were measured. The relationship between logarithmic (LG)-transformed SUA levels and bFMD was evaluated after correction for MS.

RESULTS

MS was detected in 28.4% of patients and elevated SUA levels (≥6 mg/dL) in 25.2%. MS was associated with higher LG-SUA levels (age-, gender- and glomerular filtration rate-adjusted beta = 0.204, p = 0.001). The crude linear association between LG-SUA levels and LG-bFMD (beta = -0.166, p = 0.008) was abolished after correction for MS (beta = -0.089, p = 0.172). When SUA levels were used as a categorical variable (≥6 mg/dL or <6 mg/dL and SUA quartiles, respectively), the association between LG-SUA levels and LG-bFMD remained significant after adjustment for MS (beta = -0.142, p = 0.022 and beta = -0.163, p = 0.010, respectively).

CONCLUSIONS

MS significantly affects SUA levels in HAART-treated HIV infected patients. The negative association between SUA and bFMD is independent of MS only for elevated SUA levels.

Uric acid is associated with vascular dementia in Chinese population

OBJECTIVE

Mounting evidence suggests that oxidative stress is involved in the pathogenesis of vascular dementia (VD). Uric acid (UA) has long been implicated as a critical cause of cardiovascular disease. Nevertheless, UA was also expected to play an important role in antioxidant and neuroprotection recently. We hypothesized that UA may have a protective role against VD. The aim of this study was to investigate the link between serum UA and cognitive dysfunction in VD.

MATERIALS AND METHODS

There were altogether 127 VD subjects and 81 nondemented controls enrolled in our study. Serum UA, demographic, and clinical characteristics were recorded at baseline, and all participants underwent Mini-Mental State Examination (MMSE) at the beginning of the trial.

RESULTS

The VD group showed lower MMSE scores and serum UA levels than nondemented controls and there was significant statistical difference between the two groups (p < .05). Demographic and clinical characteristics such as age, gender, education, body mass index (BMI), total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), blood urea nitrogen (BUN), and serum creatinine (Scr) did not differ dramatically between groups (p > .05). In VD subjects, there was a positive correlation between serum UA and MMSE scores (r = .32, p < .05), and this correlation was independent of demographic and clinical characteristics (β = .272, p < .05).

CONCLUSIONS

VD subjects have dramatically lower serum UA levels in comparison to nondemented controls. Lower serum UA levels are linked to cognitive dysfunction and could serve as a potential predictor for VD.

SIRT1 prevents hyperuricemia via the PGC-1α/PPARγ-ABCG2 pathway

Silent information regulator T1 (SIRT1) plays several key roles in the regulation of lipid and glucose homoeostasis. In this study, we investigated the potential role of SIRT1 in hyperuricemia and explored possible mechanisms. Significant hyperuricemia was detected in C57BL/6 mice treated with oxonate and yeast polysaccharide. Resveratrol (RSV), a specific SIRT1 activator, was administered to the mice. SIRT1 suppressed the increased serum uric acid level but up-regulated the expression of urate transporter ATP-binding cassette subfamily G member 2 (ABCG2) in the ileum of hyperuricemic mice. In a human colon carcinoma cell line, SIRT1 promoted ABCG2 production through the deacetylation of peroxisome proliferator-activated receptor (PPAR) γ co-activator 1α (PGC-1α), which then activated the effectors of PPARγ. Interestingly, the SIRT1-induced up-regulation of ABCG2 was significantly inhibited when PGC-1α or PPARγ was blocked by siRNA transfection. Our data demonstrated that SIRT1 and its activator, RSV, have clear anti-hyperuricemia functions in this mouse model. One possible mechanism is the activation of ABCG2 in the ileum through the PGC-1α/PPARγ pathway.

Characterization and Activation of NLRP3 Inflammasomes in the Renal Medulla in Mice

BACKGROUND/AIMS

Recent studies have indicated that local inflammatory mediators are importantly involved in the regulation of renal function. However, it remains unknown how such local inflammation is triggered intracellularly in the kidney. The present study was designed to characterize the inflammasome centered by Nlrp3 in the kidney and also test the effect of its activation in the renal medulla.

METHODS AND RESULTS

By immunohistochemistry analysis, we found that inflammasome components, Nlrp3, Asc and caspase-1, were ubiquitously distributed in different kidney areas. The caspase-1 activity and IL-1β production were particularly high in the renal outer medulla compared to other kidney regions. Further confocal microscopy and RT-PCR analysis showed that Nlrp3, Asc and caspase-1 were particularly enriched in the thick ascending limb of Henle's loop. In anesthetized mice, medullary infusion of Nlrp3 inflammasome activator, monosodium urate (MSU), induced significant decreases in sodium excretion and medullary blood flow without changes in mean arterial blood pressure and renal cortical blood flow. Caspase-1 inhibitor, Ac-YVAD-CMK and deletion of Nlrp3 or Asc gene abolished MSU-induced decreases in renal sodium excretion and MBF.

CONCLUSION

Our results indicate that renal medullary Nlrp3 inflammasomes represent a new regulatory mechanism of renal MBF and sodium excretion which may not depend on classical inflammatory response.

Advanced oxidation protein products are more related to metabolic syndrome components than biomarkers of lipid peroxidation

Although advanced oxidation protein products (AOPPs) have been reported as the most appropriate parameter for determination of oxidative stress in patients with metabolic syndrome (MetS), a direct comparison between protein and lipid peroxidation has not been performed yet. The aim of this study was to compare protein peroxidation with lipid peroxidation measured by 2 different methodologies (tert-butyl hydroperoxide-initiated chemiluminescence and ferrous oxidation-xylenol orange assay). The hypothesis of this study was that AOPPs would be more related to MetS than to oxidative markers of lipid peroxidation. This cross-sectional study evaluated 76 patients with MetS and 20 healthy subjects. Prooxidant-antioxidant index (PAI) assessed as AOPP/total radical-trapping antioxidant parameter ratio progressively increased (P < .05) according to the number of MetS components, whereas AOPPs and total radical-trapping antioxidant parameter increased (P < .05) when 5 components were compared with 3 components. Spearman test showed a positive correlation between AOPPs and waist circumference (r = 0.318, P < .01), fasting glucose (r = 0.250, P < .05), homeostasis model assessment insulin resistance (r = 0.043, P < .01), triacylglycerol (r = 0.713, P < .0001), highly sensitive C-reactive protein (r = 0.275, P < .05), and uric acid (r = 0.356, P < .01), whereas there was an inverse correlation with high-density lipoprotein cholesterol (r = -0.399, P < .001). Prooxidant-antioxidant index demonstrated a positive correlation with waist circumference (r = 0.386, P < .01), fasting glucose (r = 0.388, P < .01), fasting insulin (r = 0.344, P < .05), homeostasis model assessment insulin resistance (r = 0.519, P < .001), triacylglycerol (r = 0.687, P < .0001), highly sensitive C-reactive protein (r = 0.278, P < .05), and uric acid (r = 0.557, P < .0001), whereas there was an inverse correlation with high-density lipoprotein cholesterol (r = -0.480, P < .0001). In conclusion, protein peroxidation determined by AOPPs, and especially by PAI, is more related to MetS components than lipid peroxidation. In addition, PAI progressively increased with the number of MetS components.

The significance of serum uric acid level in humans with acute paraquat poisoning

Hyperuricemia is a strong and independent predictor of all-cause mortality in cardiovascular disease and has been found to play a role in diseases exacerbated by oxidative stress and inflammation. This study aimed to evaluate whether serum uric acid (UA) level is an indicator of outcome in patients with acute paraquat poisoning. A total of 205 subjects who had attempted suicide by oral ingestion of paraquat were admitted to the emergency room between January 2009 and June 2014. Initial serum UA level and other laboratory parameters were measured. A total of 66 patients died during the 30 days after admission, corresponding to a 32.2% cumulative incidence of mortality. UA levels were higher in non-survivors than survivors (P < 0.001) and 30-day mortality increased with increasing baseline serum UA level (P < 0.001). In a prediction analysis for 30-day mortality, the serum UA level had a cut-off concentration of 284 µmol/L in female patients and 352 µmol/L in male patients. Multivariate Cox proportional hazards regression analyses showed that white blood cell counts and UA were independent prognostic factors. In conclusion, we showed that serum UA may be an independent predictor of 30-day mortality in patients with paraquat poisoning.

Changes of plasma concentration of osteoprotegerin and its association with endothelial dysfunction before and after hypouricemic therapy in patients with hyperuricemia

OBJECTIVE

Osteoprotegerin (OPG) is a secreted glycoprotein in the regulation of bone turnover. Recently, many studies showed that OPG acts as an important regulatory molecule in the vascular systems. Our objective was to examine the plasma OPG levels alteration and its association with endothelial function before and after hypouricemic therapy in patients with hyperuricemia.

METHODS

Thirty patients (28 males and 2 females, serum uric acid > 7.0 mg/dl) with hyperuricemia were selected. Thirty healthy individuals (28 males and 2 females) with normal serum uric acid were also selected as control. Patients were administered with hypouricemic therapy for 6 months. Plasma OPG concentration was measured in duplicate using a sandwich ELISA and high-resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia and after sublingual glyceryltrinitrate.

RESULTS

Plasma OPG levels in patients with hyperuricemia before hypouricemic therapy was significantly higher than those in controls (3.39 ± 0.25 vs. 2.05 ± 0.74 ng/L, p < 0.01). After hypouricemic therapy, OPG levels decreased markedly (2.54 ± 0.38 ng/L, p < 0.01). Flow-mediated dilation (FMD) in patients with hyperuricemia was 3.07 ± 1. 23%, which was significantly lower than that in control subjects (4.62 ± 0.69%, p < 0.01), and it improved significantly after hypouricemic therapy (3.91 ± 1.37%, p < 0.01). The absolute changes in OPG showed a significant positive correlation with the changes in serum uric acid (p < 0.05) and negative correlation with the changes in FMD (p < 0.01) in patients with hyperuricemia during the course of hypouricemic therapy.

CONCLUSION

The current study demonstrates that plasma OPG levels increased significantly in patients with hyperuricemia and decreased significantly after hypouricemic therapy, and are correlated with FMD. These findings support the growing concept that elevated plasma OPG levels may be involved with the development of endothelial dysfunction in patients with hyperuricemia.

Role of metabolic syndrome and antiretroviral therapy in adiponectin levels and oxidative stress in HIV-1 infected patients

OBJECTIVE

HIV-1 infection is accompanied by severe metabolic and immune dysfunction. The aim of this study was to evaluate the role of metabolic syndrome (MetS) and antiretroviral therapy (ART) utilization on the adiponectin levels and oxidative stress in patients infected with HIV-1.

METHODS

We allocated 285 patients into four groups: group 1: patients without MetS who were not using ART; group 2: patients without MetS using ART; group 3: patients with MetS who were not using ART; and group 4: patients with MetS using ART. Biochemical, immunologic, and oxidative stress parameters were measured.

RESULTS

Group 4 exhibited higher lipoperoxides when compared with group 1 (P < 0.0001) and higher advanced oxidation protein products (AOPP) compared with group 2 or group 1 (P < 0.0001). Group 3 also presented higher AOPP than group 2 (P < 0.05). Group 4 showed lower adiponectin levels compared with groups 1 or 2 (P < 0.0001). Similarly, group 3 presented lower adiponectin levels compared with group 2 (P < 0.05) or group 1 (P < 0.0001). Multivariate analysis showed that both an increase in AOPP and a decrease in total radical-trapping antioxidant parameter/uric acid were independently associated with MetS in HIV-1 patients. Regarding immunologic markers of HIV-1 disease progression and viral replication, group 4 exhibited significantly higher CD45(+), CD3(+), and CD4(+) T cells count compared with group 2 (P < 0.01).

CONCLUSION

HIV-1-infected patients with MetS exhibited hypoadiponectinemia and increased oxidative stress, and these findings were not influenced by ART use. The findings of the present study allow the suggestion that MetS and inflammation might be mainly responsible for the aforementioned features. More studies are needed to verify whether drugs or food, which yield increased adiponectinemia and decreased oxidative stress, could reduce cardiovascular risk in HIV-infected patients.

Comorbidities in patients with crystal diseases and hyperuricemia

Crystal arthropathies are among the most common causes of painful inflammatory arthritis. Gout, the most common example, has been associated with cardiovascular and renal disease. In recent years, evidence for these associations and those involving other comorbidities, such as the metabolic syndrome, have emerged, and the importance of asymptomatic hyperuricemia has been established. In this review, an update on evidence, both experimental and clinical, is presented, and associations between hyperuricemia, gout, and several comorbidities are described. Causality regarding calcium pyrophosphate arthropathy and associated comorbidities is also reviewed.

Fructus Gardenia Extract ameliorates oxonate-induced hyperuricemia with renal dysfunction in mice by regulating organic ion transporters and mOIT3

The potent anti-hyperuricemia activities of Fructus Gardenia Extract (FGE) have been well reported. The aim of this study was to evaluate the uricosuric and nephro-protective effects of FGE and explore its possible mechanisms of action in oxonate-induced hyperuricemic mice. FGE was orally administered to hyperuricemic and normal mice for 1 week. Serum and urinary levels of uric acid, creatinine and blood urea nitrogen (BUN), and fractional excretion of uric acid (FEUA) were measured. The mRNA and protein levels of mouse urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9), ATP-binding cassette, subfamily G, 2 (mABCG2), organic anion transporter 1 (mOAT1), mOAT3, oncoprotein induced transcript 3 (mOIT3), organic cation/carnitine transporters in the kidney were analyzed. Simultaneously, Tamm-Horsfall glycoprotein (THP) levels in urine and kidney were detected. FGE significantly reduced serum urate levels and increased urinary urate levels and FEUA in hyperuricemic mice. It could also effectively reverse oxonate-induced alterations in renal mURAT1, mGLUT9, mOAT1 and mOIT3 expressions, as well as THP levels, resulting in the enhancement of renal uric acid excretion. Moreover, FGE decreased serum creatinine and BUN levels, and up-regulated expression of organic cation/carnitine transporters, improving renal dysfunction in this model. Furthermore, FGE decreased renal mABCG2 expressions in hyperuricemic mice, contributing to its beneficial actions. However, further investigation is needed in clinical trials of FGE and its bioactive components.