J-shaped curve for the association between serum uric acid levels and the prevalence of blood pressure abnormalities

J-shaped Association between Serum Uric Acid Levels and the Prevalence of a Reduced Kidney Function: A Cross-sectional Study Using Japanese Health Examination Data

Objective While an association between a reduced kidney function and hyperuricemia has been reported, its association with hypouricemia is not well understood. The present study therefore investigated this association. Methods Using a large Japanese health examination dataset, we performed a multivariable logistic regression analysis to assess the association between serum uric acid (SUA) levels and a reduced kidney function. The covariates included the age, body mass index, alcohol intake, and the presence of hypertension, dyslipidemia, or diabetes. Patients This study included 227,672 patients (104,854 men; 46.1%), and the analyses were performed separately for men and women. The patients were classified into 5 groups: hypouricemia (SUA ≤2.0 mg/dL) (1st) and four other (2nd-5th) groups with SUA levels of ≤2.0, 2.1-5.1, 5.2-5.9, 6.0-6.8, ≥6.9 mg/dL in men and ≤2.0, 2.1-3.7, 3.8-4.4, 4.5-5.1, ≥5.2 mg/dL in women, respectively. Results The characteristics of the study population were as follows: men, age 55.9±14.9 years old, SUA 5.9±1.3 mg/dL, estimated glomerular filtration rate (eGFR) 80.0±17.2 mL/min/1.73 m2, and a reduced kidney function (eGFR <60.0 mL/min/1.73 m2) 9.4%; women, age 57.3±15.0 years old, SUA 4.5±1.1 mg/dL, eGFR 81.2±18.0 mL/min/1.73 m2, and a reduced kidney function 9.4%. Compared with the 2nd group, the other 4 groups groups had a significantly higher prevalence of a reduced kidney function [odds ratio (OR), 2.58; 95% confidence interval (CI), 1.64-4.06 in men; OR, 1.66; 95% CI, 1.16-2.39 in women]. Conclusion The prevalence of a reduced kidney function was high in both men and women in the hypouricemia and high-SUA groups. SUA levels and the prevalence of a reduced kidney function showed a J-shaped association.

The protective effects of uric acid against myocardial ischemia via the Nrf2 pathway

Uric acid (UA) possesses both pro- and anti-oxidative properties in ischemic heart disease, but the underlying mechanism remains unclear. We aimed to investigate UA's protective effect on myocardial ischemia by examining its effects on ECG Ischemic Alterations (EIA) and H2O2-induced oxidative stress in H9C2 myocardial cells. The incidence of EIA decreased over time and was more prevalent among women than men. A U-shaped relationship was observed between UA levels and EIA incidence, with the third quartile exhibiting a protective association. Addition of 237.9 μmol/L UA improved cellular damage and oxidative stress in H2O2-treated H9C2 cells, as determined by cell viability, LDH release, ROS levels, and total antioxidant capacity assays. UA activated the Nrf2 pathway, evidenced by increased expression of Nrf2, GCLC, and HO-1 proteins. By reversing cell cycle blockage, promoting wound healing ability, improving colony-forming capacity, and increasing angiogenesis in H2O2-treated cells, UA exhibited positive effects on cardiomyocyte growth characteristics. Additionally, use of Nrf2 inhibitor ML385 confirmed the involvement of the Nrf2 pathway by negating UA's effects on oxidatively damaged cardiomyocytes. Our findings suggest that UA induces downstream antioxidant factors to ameliorate oxidative stress by activating the Nrf2 pathway, which could be one of the targets responsible for UA's beneficial effects in myocardial ischemia.

Dysuricemia-A New Concept Encompassing Hyperuricemia and Hypouricemia

The importance of uric acid, the final metabolite of purines excreted by the kidneys and intestines, was not previously recognized, except for its role in forming crystals in the joints and causing gout. However, recent evidence implies that uric acid is not a biologically inactive substance and may exert a wide range of effects, including antioxidant, neurostimulatory, proinflammatory, and innate immune activities. Notably, uric acid has two contradictory properties: antioxidant and oxidative ones. In this review, we present the concept of "dysuricemia", a condition in which deviation from the appropriate range of uric acid in the living body results in disease. This concept encompasses both hyperuricemia and hypouricemia. This review draws comparisons between the biologically biphasic positive and negative effects of uric acid and discusses the impact of such effects on various diseases.

The Association Between Hypouricemia and Cardiometabolic Diseases: Analyzing Nationwide Data From Medical Checkup and Health Insurance Records

OBJECTIVES

The aims of this study were to evaluate the association between hypouricemia and cardiometabolic diseases, such as hypertension, dyslipidemia, and reduced kidney function, and to explore the sex-specific optimal range for serum uric acid (sUA) associated with the lowest risk for these diseases.

METHODS

In this cross-sectional study, we identified individuals with sUA data between April 2018 and March 2019 and recorded the frequency of cardiometabolic comorbidities according to sUA. Univariable and multivariable logistic regression analyses were performed for the overall population and after classifying by sex to assess the association between sUA and cardiometabolic comorbidities.

RESULTS

Among 796,508 individuals, a J-shaped association was observed between the sUA level and cardiometabolic diseases in the overall population. The adjusted odds ratios (95% confidence interval) for hypertension, dyslipidemia, and reduced renal function in individuals with sUA ≤1.0 mg/dL compared with those with sUA ranging between 2.1 and 3.0 mg/dL were 1.38 (1.13-1.69), 1.52 (1.30-1.78), and 2.17 (1.47-3.20), respectively. A J-shaped association between sUA and hypertension was observed only in women. The optimal range of sUA associated with the lowest risk for hypertension was assumed to be <6 mg/dL in men and 1-4 mg/dL in women. A J-shaped association between the sUA and dyslipidemia and reduced renal function was observed in both men and women. The optimal range of sUA for dyslipidemia and reduced renal function was approximately 2-5 mg/dL in men and 1-4 mg/dL in women.

CONCLUSIONS

Excess and extremely low uric acid levels may be related to an increased cardiometabolic risk.

Sex-specific association of serum uric acid trajectories with risk of incident retinal arteriosclerosis in Chinese population: A population-based longitudinal study

Background

The impact of serum uric acid (SUA) trajectories on the development of retinal arteriosclerosis is uncertain. The purpose of this study was to identify adult SUA trajectories by sex and determine their association with risk of retinal arteriosclerosis.

Methods

In this longitudinal study, 4,324 participants who were aged between 18 and 60 years without retinal arteriosclerosis at or before baseline (from January 1, 2010, through December 31, 2010) were included. Group-based trajectory modeling was used to identify SUA trajectories during the exposure period (from January 1, 2006, through December 31, 2010). Cox proportional-hazards models were applied to evaluate the associations between SUA trajectories and the risk of incident retinal arteriosclerosis during the outcome period (from January 1, 2011, through December 31, 2019).

Results

4 distinct SUA trajectories were identified in both women and men: low, moderate, moderate-high, and high. During a median follow-up of 9.54 years (IQR 9.53-9.56), 97 women and 295 men had developed retinal arteriosclerosis. In the fully adjusted model, a significant association between the moderate-high SUA trajectory group and incidence of retinal arteriosclerosis was observed only in men (HR: 1.76, 95% CI: 1.17-2.65) compared with the low trajectory group, but not in women (HR: 0.77, 95% CI: 0.39-1.52). Also, the high SUA trajectory group had the highest risk with an adjusted HR of 1.81 (95% CI, 1.04-3.17) in men. However, they did not exhibit a substantially increased risk in women.

Conclusion

Higher SUA trajectory groups were significantly associated with an increased risk of incident retinal arteriosclerosis in men but not in women.

Update on Hypertension Research in 2021

In 2021, 217 excellent manuscripts were published in Hypertension Research. Editorial teams greatly appreciate the authors' contribution to hypertension research progress. Here, our editorial members have summarized twelve topics from published work and discussed current topics in depth. We hope you enjoy our special feature, "Update on Hypertension Research in 2021".

Impact of hyperuricemia on chronic kidney disease and atherosclerotic cardiovascular disease

Hyperuricemia is caused by reduced renal/extrarenal excretion and overproduction of uric acid. It is affected by genetic predisposition related to uric acid transporters and by visceral fat accumulation due to overnutrition. The typical symptomatic complication of hyperuricemia is gout caused by monosodium urate crystals. Accumulated evidence from epidemiological studies suggests that hyperuricemia is also a risk factor for hypertension, chronic kidney disease (CKD) and atherosclerotic cardiovascular disease (CVD). However, it remains to be determined whether urate-lowering therapy for asymptomatic patients with hyperuricemia is effective in preventing CKD or CVD progression. This mini review focuses mainly on recent papers investigating the relationship between hyperuricemia and CKD or CVD and studies of urate-lowering therapy. Accumulated studies have proposed mechanisms of renal damage and atherosclerosis in hyperuricemia, including inflammasome activation, decreased nitric oxide bioavailability and oxidative stress induced by uric acid, urate crystals and xanthine oxidoreductase (XOR)-mediated reactive oxygen species. Since patients with hyperuricemia are a heterogeneous population with complex pathologies, it may be important to assess whether an outcome is the result of decreasing serum uric acid levels or an inhibitory effect on XOR. To clarify the impact of hyperuricemia on CKD and CVD progression, high-quality and detailed clinical and basic science studies of hyperuricemia and purine metabolism are needed.

Seasonal variation in blood pressure: current evidence and recommendations for hypertension management

Blood pressure (BP) exhibits seasonal variation, with an elevation of daytime BP in winter and an elevation of nighttime BP in summer. The wintertime elevation of daytime BP is largely attributable to cold temperatures. The summertime elevation of nighttime BP is not due mainly to temperature; rather, it is considered to be related to physical discomfort and poor sleep quality due to the summer weather. The winter elevation of daytime BP is likely to be associated with the increased incidence of cardiovascular disease (CVD) events in winter compared to other seasons. The suppression of excess seasonal BP changes, especially the wintertime elevation of daytime BP and the summertime elevation of nighttime BP, would contribute to the prevention of CVD events. Herein, we review the literature on seasonal variations in BP, and we recommend the following measures for suppressing excess seasonal BP changes as part of a regimen to manage hypertension: (1) out-of-office BP monitoring, especially home BP measurements, throughout the year to evaluate seasonal variations in BP; (2) the early titration and tapering of antihypertensive medications before winter and summer; (3) the optimization of environmental factors such as room temperature and housing conditions; and (4) the use of information and communication technology-based medicine to evaluate seasonal variations in BP and provide early therapeutic intervention. Seasonal BP variations are an important treatment target for the prevention of CVD through the management of hypertension, and further research is necessary to clarify these variations.

Effect of febuxostat on left ventricular diastolic function in patients with asymptomatic hyperuricemia: a sub analysis of the PRIZE Study

Hyperuricemia is related to an increased risk of cardiovascular events from a meta-analysis and antihyperuricemia agents may influence to cardiac function. We evaluated the effect of febuxostat on echocardiographic parameters of diastolic function in patients with asymptomatic hyperuricemia as a prespecified endpoint in the subanalysis of the PRIZE study. Patients in the PRIZE study were assigned randomly to either add-on febuxostat treatment group or control group with only appropriate lifestyle modification. Of the 514 patients in the overall study, 65 patients (31 in the febuxostat group and 34 in the control group) who had complete follow-up echocardiographic data of the ratio of peak early diastolic transmitral flow velocity (E) to peak early diastolic mitral annular velocity (e') at baseline and after 12 and 24 months were included. The primary endpoint was a comparison of the changes in the E/e' between the two groups from baseline to 24 months. Interestingly, e' was slightly decreased in the control group compared with in the febuxostat group (treatment p = 0.068, time, p = 0.337, treatment × Time, p = 0.217). As a result, there were significant increases in E/e' (treatment p = 0.045, time, p = 0.177, treatment × time, p = 0.137) after 24 months in the control group compared with the febuxostat group. There was no significant difference in the serum levels of N-terminal-pro brain natriuretic peptide and high-sensitive troponin I between the two groups during the study period. In conclusions, additional febuxostat treatment in patients with asymptomatic hyperuricemia for 24 months might have a potential of preventable effects on the impaired diastolic dysfunction.