Uric acid levels, kidney function, and cardiovascular mortality in US adults: National Health and Nutrition Examination Survey (NHANES) 1988-1994 and 1999-2002

The Role of Uric Acid and Methyl Derivatives in the Prevention of Age-Related Neurodegenerative Disorders

High uric acid (UA levels have been correlated with a reduced risk of many neurodegenerative diseases through mechanisms involving chelating Fenton reaction transitional metals, antioxidant quenching of superoxide and hydroxyl free radicals, and as an electron donor that increases antioxidant enzyme activity (e.g. SOD. However, the clinical usefulness of UA is limited by its' low water solubility and propensity to form inflammatory crystals at hyperuricemic levels. This review focuses on the role of UA in neuroprotection, as well as potential strategies aimed at increasing UA levels in the soluble range, and the potential therapeutic use of more water-soluble methyl-UA derivatives from the natural catabolic end-products of dietary caffeine, theophylline, and theobromine.

SGLT2 Inhibitors and Cardiovascular Risk: Lessons Learned From the EMPA-REG OUTCOME Study

Although cardiovascular (CV) mortality is the principal cause of death in individuals with type 2 diabetes (T2DM), reduction of plasma glucose concentration has little effect on CV disease (CVD) risk. Thus, novel strategies to reduce CVD risk in T2DM patients are needed. The recently published BI 10773 (Empagliflozin) Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME) study demonstrated that in T2DM patients with high CVD risk empagliflozin reduced the primary major adverse cardiac event end point (CV death, nonfatal myocardial infarction, nonfatal stroke) by 14%. This beneficial effect was driven by a 38% reduction in CV mortality with no significant decrease in nonfatal myocardial infarction or stroke. Empagliflozin also caused a 35% reduction in hospitalization for heart failure without affecting hospitalization for unstable angina. Although sodium-glucose cotransporter 2 inhibitors exert multiple metabolic benefits (decreases in HbA1c, body weight, and blood pressure and an increase in HDL cholesterol), all of which could reduce CVD risk, it is unlikely that the reduction in CV mortality can be explained by empagliflozin's metabolic effects. More likely, hemodynamic effects, specifically reduced blood pressure and decreased extracellular volume, are responsible for the reduction in CV mortality and heart failure hospitalization. In this Perspective, we will discuss possible mechanisms for these beneficial effects of empagliflozin and their implications for the care of T2DM patients.

A causal relationship between uric acid and diabetic macrovascular disease in Chinese type 2 diabetes patients: A Mendelian randomization analysis

BACKGROUND

As the association between uric acid and macrovascular disease has been heavily debated, we aimed to confirm whether there is a causal relationship between uric acid and diabetic macrovascular disease through Mendelian randomization analysis.

METHODS

In 3207 type 2 diabetes patients, seventeen SNPs (single nucleotide polymorphisms) related to uric acid were genotyped. A weighted GRS (genetic risk score) was calculated using selected SNPs and the strength of their effects on uric acid levels. Diabetic macrovascular disease was diagnosed through vascular ultrasound, magnetic resonance imaging or other clinical evidence. Associations of diabetic macrovascular disease with uric acid and weighted GRS were evaluated separately.

RESULTS

In total participants and among females, the prevalence of diabetic macrovascular disease was significantly higher in hyperuricemic group than in normouricemic group, and uric acid was associated with diabetic macrovascular disease (OR=1.068, p=0.0349; OR=1.122, p=0.0158). The prevalence of diabetic macrovascular disease increased with the weighted GRS in a J-shaped manner for the females. The weighted GRS was positively correlated with uric acid in total population, male patients and female patients (β=0.203, p<0.0001; β=0.255, p<0.0001; β=0.142, p<0.0001, respectively). The weighted GRS was significantly associated with diabetic macrovascular disease in female patients (OR=1.184, p=0.0039). Among females, the observed association between weighted GRS and diabetic macrovascular disease was greater than predicted.

CONCLUSIONS

Using the uric acid-related weighted GRS as an instrumental variable for Mendelian randomization analysis, our study provided an evidence for causal relationship between uric acid and diabetic macrovascular disease in Chinese females with type 2 diabetes mellitus.

Uricase alkaline enzymosomes with enhanced stabilities and anti-hyperuricemia effects induced by favorable microenvironmental changes

Enzyme therapy is an effective strategy to treat diseases. Three strategies were pursued to provide the favorable microenvironments for uricase (UCU) to eventually improve its features: using the right type of buffer to constitute the liquid media where catalyze reactions take place; entrapping UCU inside the selectively permeable lipid vesicle membranes; and entrapping catalase together with UCU inside the membranes. The nanosized alkaline enzymosomes containing UCU/(UCU and catalase) (ESU/ESUC) in bicine buffer had better thermal, hypothermal, acid-base and proteolytic stabilities, in vitro and in vivo kinetic characteristics, and uric acid lowering effects. The favorable microenvironments were conducive to the establishment of the enzymosomes with superior properties. It was the first time that two therapeutic enzymes were simultaneously entrapped into one enzymosome having the right type of buffer to achieve added treatment efficacy. The development of ESU/ESUC in bicine buffer provides valuable tactics in hypouricemic therapy and enzymosomal application.

Latent association between low urine pH and low body weight in an apparently healthy population

Low urine pH, a plausible predictor for chronic kidney disease and metabolic disorders, is often observed in obese individuals. However, the association between low urine pH and low body weight is equivocal. We examined clinical parameters including urine pH and body mass index (BMI) in a cross-sectional study of 3629 apparently healthy Japanese adults aged 25-80 years who underwent a health-screening check-up. Urine pH was lower and the prevalence of proteinuria was significantly higher in subjects with BMI of ≥ 27.0 kg/m(2) compared with those with BMI of 21.0-22.9 kg/m(2). By contrast, hematuria was more prevalent in subjects with BMI of ≤ 20.9 kg/m(2). Logistic regression analysis showed that BMI of ≥ 27.0 kg/m(2) was significantly associated with low urine pH (≤ 5.5), which remained significant after adjustment for relevant confounders including age, sex, proteinuria, estimated glomerular filtration rate, urine density, hematuria, smoking status, and daily alcohol drinking. However, the association disappeared after further adjustment for serum uric acid. In contrast, the association between low urine pH and BMI of ≤ 19.0 kg/m(2) was significant after adjustment for age and sex and rather strengthened by the further adjustment for serum uric acid. In conclusion, low urine pH may be independently associated with low BMI. However, the underlying mechanisms of low urine pH in low body weight may differ from those in high body weight.

Serum Urate and Incident Cardiovascular Disease: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

OBJECTIVE

There is controversy about whether serum urate (sUA) predicts future cardiovascular disease (CVD) independently of classical risk factors, and the age at which any prediction starts. We studied the sUA-CVD association among generally healthy adults.

METHODS

CARDIA recruited 5115 black and white individuals aged 18-30 years in 1985-1986 (year-0). Fatal and nonfatal CVD events by year 27 (n = 164) were ascertained during annual contacts and classified using medical records. The association with sUA (year-0, 10, 15 and 20) was modeled using Cox proportional hazards regression, pooling over gender-specific quartiles.

RESULTS

Mean sUA concentration was higher in men than women, but increased over time in both genders. Those with elevated sUA had worse metabolic profiles that substantially deteriorated over time. Adjusting for demographic and lifestyle factors (the minimal model), baseline sUA concentration was positively associated with incident CVD (hazard ratio (HR) per mg/dL = 1.21; 95% confidence interval: 1.05, 1.39; P = 0.005). This positive association attenuated to nonsignificance in the full model accounting simultaneously for classical CVD risk factors (HR = 1.09; 0.94, 1.27; P = 0.24). Both the minimal and full models appeared to show stronger associations (than year-0 sUA) between year-10 sUA and incident CVD (HR = 1.27 and 1.12, respectively), but sUA was not statistically significant in the full model. Despite fewer events, year-15 sUA showed a significant sUA-CVD association pattern, with minimal model association magnitude comparable to year-10, and remained significant in the full model (HR = 1.19; 1.02, 1.40; P = 0.03). Hyperuricemia at year-15 strongly predicted CVD risk (HR = 2.11; 1.34, 3.33; P = 0.001), with some attenuation in the full model (HR = 1.68; P = 0.04).

CONCLUSIONS

sUA may be an early biomarker for CVD in adults entering middle age. The prediction of CVD by sUA appeared to strengthen with aging. The potential complex relation of sUA with deterioration of a cluster of metabolic abnormalities warrants future exploration.

Uric Acid as a Marker of Kidney Disease: Review of the Current Literature

Uric acid has been implicated in the pathophysiology of renal disease; however renal clearance makes a causal relationship difficult to prove. We examine the current literature to support a potential role of uric acid in the development of kidney disease and to determine the potential to use uric acid as a marker for future renal decline. After review, we conclude that uric acid is definitively linked to the development of chronic kidney disease and can be a poor prognostic factor for the development of acute renal failure, as well. However, further human research is needed before predictive models utilizing uric acid can be developed and used in the clinical setting.

Uric acid level has a U-shaped association with loss of kidney function in healthy people: a prospective cohort study

BACKGROUND

The relationship between hyperuricemia and chronic kidney disease (CKD) has been found in various observational studies. Although hypouricemia is associated with cardiovascular events, it has not been established as a risk factor for CKD. We investigated the relationship between serum uric acid level and the loss of kidney function and incident CKD in healthy people.

MATERIALS AND METHODS

Healthy people were enrolled in this community-based prospective cohort study, the Saitama Cardiometabolic Disease and Organ Impairment Study, Japan. The analysis was conducted on 4188 subjects followed up for at least 3 years, 3102 for 6 years and 1052 for 9 years. Their data including glomerular filtration rate (eGFR) decline were examined every three years. The outcome event was incident CKD or the decrease in eGFR by more than 25% in three years. Multivariate statistical models were adjusted for the baseline characteristics.

RESULTS

The following data was obtained: mean ± SD age, male, 39.6 ± 10.4 years, female 38.4 ± 10.8 years; eGFR, male, 81.9 ± 16.4 ml/min/1.73 m2, female, 82.1 ± 17.5 ml/min/1.73 m2; serum uric acid level, male, 5.8 ± 1.2 mg/dl, female, 4.1 ± 0.9 mg/dl. Both low and high serum uric acid levels were associated with the outcome and eGFR decline in males (multivariate logistic additional additive models, linear p = 0.0001, spline p = 0.043; generalized additive models, linear p = 0.0001, spline p = 0.012). In subjects with low serum uric acid levels (male, <5 mg/dl; female, <3.6 mg/dl), multivariate linear mixed models showed that low serum uric acid levels were associated with eGFR decline in a time-dependent manner (male, p = 0.0001; female, p = 0.045).

CONCLUSION

This study showed that low as well as high levels of uric acid are associated with the loss of kidney function. Hypouricemia is a candidate predictor of kidney function decline in healthy people.

High serum uric acid is associated with increased cardio-ankle vascular index (CAVI) in healthy Japanese subjects: a cross-sectional study

OBJECTIVE

To investigate the association of serum uric acid (SUA) with arterial stiffness assessed by cardio-ankle vascular index (CAVI).

METHODS

We analyzed the cross-sectional data from 27,360 healthy Japanese subjects (12,910 males and 14,450 females) aged between 20 and 74 years without a past history of heart disease, stroke, hypertension, diabetes, nephritis or gout. We investigated whether SUA was independently associated with CAVI in a gender-specific manner.

RESULTS

BMI, CAVI, systolic/diastolic BP, GOT, GPT, γ-GTP, triglyceride (TG), creatinine and SUA were higher and HDL-C was lower in males than in females. Next, they were stratified by SUA into 3 groups: lower tertile (T1), middle tertile (T2) and upper tertile (T3) and by gender. CAVI increased progressive with increasing SUA tertile, after adjusting for age, BMI and systolic BP (sBP) identified in multiple regression analysis for CAVI. Multivariate analysis showed that the odds ratios (95% CI) relative to T1 for high CAVI (≥90(th) percentile) were 1.233 (0.928-1.638) in T2 and 1.352 (1.031-1.773) in T3 for males, and 1.133 (0.984-1.303) in T2 and 1.361 (1.098-1.687) in T3 for females, after adjusting for confounders. Furthermore, increase in adjusted CAVI was observed in a lower SUA range in females compared to that observed in males.

CONCLUSION

We demonstrated an independent correlation between SUA and CAVI, and observed gender difference in the SUA range for increase in CAVI. These results may suggest the need to set different target SUA levels for men and women in anti-hyperuricemic treatment for atherosclerosis prevention.

Allopurinol and progression of CKD and cardiovascular events: long-term follow-up of a randomized clinical trial

BACKGROUND

Asymptomatic hyperuricemia increases renal and cardiovascular (CV) risk. We previously conducted a 2-year, single-blind, randomized, controlled trial of allopurinol treatment that showed improved estimated glomerular filtration rate and reduced CV risk.

STUDY DESIGN

Post hoc analysis of a long-term follow-up after completion of the 2-year trial.

SETTING & PARTICIPANTS

113 participants (57 in the allopurinol group and 56 in the control group) initially followed up for 2 years and 107 participants followed up to 5 additional years.

INTERVENTION

Continuation of allopurinol treatment, 100mg/d, or standard treatment.

OUTCOME

Renal event (defined as starting dialysis therapy and/or doubling serum creatinine and/or ≥50% decrease in estimated estimated glomerular filtration rate) and CV events (defined as myocardial infarction, coronary revascularization or angina pectoris, congestive heart failure, cerebrovascular disease, and peripheral vascular disease).

RESULTS

During initial follow-up, there were 2 renal and 7 CV events in the allopurinol group compared with 6 renal and 15 CV events in the control group. In the long-term follow-up period, 12 of 56 participants taking allopurinol stopped treatment and 10 of 51 control participants received allopurinol. During long-term follow-up, an additional 7 and 9 participants in the allopurinol group experienced a renal or CV event, respectively, and an additional 18 and 8 participants in the control group experienced a renal or CV event, respectively. Thus, during the initial and long-term follow-up (median, 84 months), 9 patients in the allopurinol group had a renal event compared with 24 patients in the control group (HR, 0.32; 95% CI, 0.15-0.69; P=0.004; adjusted for age, sex, baseline kidney function, uric acid level, and renin-angiotensin-aldosterone system blockers). Overall, 16 patients treated with allopurinol experienced CV events compared with 23 in the control group (HR, 0.43; 95% CI, 0.21-0.88; P=0.02; adjusted for age, sex, and baseline kidney function).

LIMITATIONS

Small sample size, single center, not double blind, post hoc follow-up and analysis.

CONCLUSIONS

Long-term treatment with allopurinol may slow the rate of progression of kidney disease and reduce CV risk.

Serum Uric Acid, Gender, and Low Ankle Brachial Index in Adults With High Cardiovascular Risk

Uric acid (UA) has been reported to be associated with cardiovascular disease (CVD) in caucasians. However, it is unclear whether this association remains significant in a Chinese population. The present study aimed to investigate the association between UA and low ankle brachial index (ABI), a measurement of peripheral arterial disease, in Chinese patients. A total of 6262 hospital-based patients with high CVD risk were enrolled. Low ABI was defined as ABI ≤0.9 in either side. Low ABI was detected in 1390 (22.2%) patients. Higher UA was significantly associated with higher risk of low ABI and modified by gender (P = .0045). After adjusting for age, body mass index, total cholesterol, triglyceride, low-density lipoprotein, high-density lipoprotein, fasting glucose, hypertension, and smoking, participants in the highest quartile of UA exhibited 37% (odds ratio [OR]:1.37, 95% confidence interval [CI]: 1.03-1.82) higher risk of low ABI compared to those in the lowest quartile in men, while OR (95% CI) was 1.69 (1.29-2.22) for women. However, when kidney function was further adjusted, the associations were attenuated in both men and women and were significant only in women. The results were suggestive of higher UA associating with higher risk of low ABI in women, and the association was largely driven by kidney function, especially in men.

Switching from allopurinol to febuxostat for the treatment of hyperuricemia and renal function in patients with chronic kidney disease

Hyperuricemia is a frequent complication of chronic kidney disease (CKD). Febuxostat is a novel xanthine oxidase inhibitor that is metabolized by many metabolic pathways in the kidney and the liver. We performed a 1-year cohort study of 73 hyperuricemic patients who had an estimated glomerular filtration rate (eGFR) below 45 ml/min and were being treated with urate-lowering therapy. In 51 patients, treatment was changed from allopurinol to febuxostat, and the other 22 patients were continued on allopurinol. The serum levels of uric acid (UA) level, creatinine, and other biochemical parameters were measured at baseline and after 3, 6, 9, and 12 months of treatment. The serum UA levels significantly decreased from 6.1 ± 1.0 to 5.7 ± 1.2 mg/dl in the febuxostat group and significantly increased from 6.2 ± 1.1 to 6.6 ± 1.1 mg/dl in the allopurinol group. The eGFR decreased 27.3 to 25.7 ml/min in the febuxostat group and from 26.1 to 19.9 ml/min in the allopurinol group. The switch from allopurinol to febuxostat was significantly associated with the changes in eGFR according to a multiple regression analysis (β = −0.22145, P < 0.05). Febuxostat reduced the serum UA levels and slowed the progression of renal disease in our CKD cohort in comparison with allopurinol.