The role of uric acid in the pathogenesis of hypertension in the young

Asymptomatic hyperuricemia: to treat or not a threat? A clinical and evidence-based approach to the management of hyperuricemia in the context of cardiovascular diseases

Asymptomatic hyperuricemia is defined by serum uric acid levels above 6.2 mg/dl in women and 7 mg/dl in men. In the presence of monosodium urate crystal formation and articular inflammation, hyperuricemia may become symptomatic (namely nephrolithiasis and gout). Uric acid results from purine catabolism and is at the centre of a complex metabolic interplay that involves oxidative stress, inflammation, renin-angiotensin-aldosterone system (RAAS) activation and insulin resistance. Uric acid levels present a continuous relation with conditions like hypertension and chronic kidney disease (CKD) and are reported to have an impact on risk of cardiovascular events. However, whether elevated uric acid is a causal agent and thus a possible therapeutic target is still uncertain and matter of further investigation. Treating symptomatic hyperuricemia involves lowering uric acid drugs and controlling inflammation. Urate-lowering agents are well tolerated but show minimal impact on cardiovascular events in patients with gout. Use of direct-acting urate-lowering agents in asymptomatic hyperuricemia associated with cardiovascular diseases does not warrant a clear benefit, whereas addressing cardiovascular issues with guideline-recommended therapies lowers uric acid and reduces the occurrence of cardiovascular events. Regular assessment of uric acid and clinical symptoms is advised before starting and renewing a urate-lowering treatment.

Efficacy and Safety of Allopurinol on Chronic Kidney Disease Progression: A Systematic Review and Meta-Analysis

OBJECTIVE

Hyperuricemia is associated with the progression of chronic kidney disease (CKD). Whether urate-lowering treatment with allopurinol can delay disease progression remains controversial.

METHODS

Relevant databases were searched. Randomized clinical trials comparing the efficacy and -safety of allopurinol in patients with CKD were selected. The primary outcomes were changes in serum uric acid concentration and estimated glomerular filtration rate (eGFR). Random-effects modeling was used to -calculate the standard mean difference (SMD) with 95% CIs.

RESULTS

Four trials enrolling 698 participants were included. All were 2-arm parallel trials with a mean duration follow-up of 22.5 months. Congenital anomalies of the kidney and urinary tract were the most common cause of CKD in children, whereas diabetes was the leading cause of CKD in adults. Allopurinol significantly increased the eGFR compared with control groups (SMD, 2.04; 95% CI, 0.60-3.49; p = 0.005; I2 = 98.23%). Allopurinol led to a significant decrease in serum uric acid concentration compared with the control group (SMD, -5.16; 95% CI, -8.31 to -2.01; p = 0.001; I2 = 98.80%). No significant difference in adverse effects was identified between treatment and control groups.

CONCLUSIONS

Allopurinol treatment in patients with CKD and hyperuricemia slows the decline in eGFR as compared with placebo, without risk of increased adverse effects.

Allopurinol and blood pressure variability following ischemic stroke and transient ischemic attack: a secondary analysis of XILO-FIST

Blood Pressure Variability (BPV) is associated with cardiovascular risk and serum uric acid level. We investigated whether BPV was lowered by allopurinol and whether it was related to neuroimaging markers of cerebral small vessel disease (CSVD) and cognition. We used data from a randomised, double-blind, placebo-controlled trial of two years allopurinol treatment after recent ischemic stroke or transient ischemic attack. Visit-to-visit BPV was assessed using brachial blood pressure (BP) recordings. Short-term BPV was assessed using ambulatory BP monitoring (ABPM) performed at 4 weeks and 2 years. Brain MRI was performed at baseline and 2 years. BPV measures were compared between the allopurinol and placebo groups, and with CSVD and cognition. 409 participants (205 allopurinol; 204 placebo) were included in the visit-to-visit BPV analyses. There were no significant differences found between placebo and allopurinol groups for any measure of visit-to-visit BPV. 196 participants were included in analyses of short-term BPV at week 4. Two measures were reduced by allopurinol: the standard deviation (SD) of systolic BP (by 1.30 mmHg (95% confidence interval (CI) 0.18-2.42, p = 0.023)); and the average real variability (ARV) of systolic BP (by 1.31 mmHg (95% CI 0.31-2.32, p = 0.011)). There were no differences in other measures at week 4 or in any measure at 2 years, and BPV was not associated with CSVD or cognition. Allopurinol treatment did not affect visit-to-visit BPV in people with recent ischemic stroke or TIA. Two BPV measures were reduced at week 4 by allopurinol but not at 2 years.

Uric Acid Is Not Associated With Cardiovascular Health in Youth With Type 1 Diabetes: SEARCH for Diabetes in Youth Study

CONTEXT

Uric acid's role in cardiovascular health in youth with type 1 diabetes is unknown.

OBJECTIVE

Investigate whether higher uric acid is associated with increased blood pressure (BP) and arterial stiffness over time in adolescents and young adults with type 1 diabetes and if overweight/obesity modifies this relationship.

METHODS

Longitudinal analysis of data from adolescents and young adults with type 1 diabetes from 2 visits (mean follow up 4.6 years) in the SEARCH for Diabetes in Youth multicenter prospective cohort study from 2007 to 2018. Our exposure was uric acid at the first visit and our outcome measures were the change in BP, pulse wave velocity (PWV), and augmentation index between visits. We used multivariable linear mixed-effects models and assessed for effect modification by overweight/obesity.

RESULTS

Of 1744 participants, mean age was 17.6 years, 49.4% were female, 75.9% non-Hispanic White, and 45.4% had a follow-up visit. Mean uric acid was 3.7 mg/dL (SD 1.0). Uric acid was not associated with increased BP, PWV-trunk, or augmentation index over time. Uric acid was marginally associated with PWV-upper extremity (β = .02 m/s/year, 95% CI 0.002 to 0.04). The magnitude of this association did not differ by overweight/obesity status.

CONCLUSION

Among adolescents and young adults with type 1 diabetes, uric acid was not consistently associated with increased BP or arterial stiffness over time. These results support findings from clinical trials in older adults with diabetes showing that lowering uric acid levels does not improve cardiovascular outcomes.

Assessment of Hypertensive Patients' Complex Metabolic Status Using Data Mining Methods

Cardiovascular diseases are among the leading causes of mortality worldwide. Hypertension is a preventable risk factor leading to major cardiovascular events. We have not found a comprehensive study investigating Central and Eastern European hypertensive patients' complex metabolic status. Therefore, our goal was to calculate the prevalence of hypertension and associated metabolic abnormalities using data-mining methods in our region. We assessed the data of adults who visited the University of Debrecen Clinical Center's hospital (n = 937,249). The study encompassed data from a period of 20 years (2001-2021). We detected 292,561 hypertensive patients. The calculated prevalence of hypertension was altogether 32.2%. Markedly higher body mass index values were found in hypertensive patients as compared to non-hypertensives. Significantly higher triglyceride and lower HDL-C levels were found in adults from 18 to 80 years old. Furthermore, significantly higher serum glucose and uric acid levels were measured in hypertensive subjects. Our study confirms that the calculated prevalence of hypertension is akin to international findings and highlights the extensive association of metabolic alterations. These findings emphasize the role of early recognition and immediate treatment of cardiometabolic abnormalities to improve the quality of life and life expectancy of hypertensive patients.

Exploring the Effects of Elevated Serum Uric Acid Levels on Hypertension: A Scoping Review of Hyperuricemia

Hypertension (HTN) is a global health concern due to its increasing prevalence and association with life-threatening complications. An intriguing area of investigation in HTN research is the relationship between HTN and hyperuricemia. In light of this, we conducted a review to summarize the relevant studies exploring the link between elevated serum uric acid (sUA) concentration and new-onset HTN. Through a comprehensive search of PubMed Central, MEDLINE, and PubMed databases, we identified 20 studies that met our inclusion criteria. The research encompassed various study designs, including cohort studies, cross-sectional studies, reviews, and clinical trials. Pathologically, the elevated sUA levels activate the renin-angiotensin system and also cause the formation of urate crystals, triggering inflammation in the kidneys. Additionally, direct effects on the endothelium contribute to inflammation, oxidative stress, nitric oxide depletion, and smooth muscle cell proliferation, ultimately leading to atherosclerosis. These diverse mechanisms collectively play a role in the pathogenesis of HTN. Interestingly, lowering sUA has been shown to reverse early-stage HTN dependent on uric acid. However, this effect is not observed in the uric acid-independent second stage of HTN. Various studies have demonstrated an independent and dose-dependent association between sUA levels and the prevalence of HTN across different populations and genders. The review highlights the potential role of uric acid-lowering drugs, like allopurinol, in the prevention and early-stage management of HTN. However, there is scarce research on the efficacy of other uric acid-lowering agents and combination therapies. We believe our review provides compelling evidence of the association between elevated sUA concentration and new-onset HTN. Identifying and managing hyperuricemia can provide a preventive approach to reducing the burden of HTN and its associated complications.

Association of hyperuricemia combined with sarcopenia on ASCVD risk

BACKGROUND

Hyperuricemia and sarcopenia are both strongly linked to an increased risk of atherosclerotic cardiovascular disease (ASCVD), and this study was designed to look into the interactive effects of hyperuricemia on ASCVD risk.

METHODS

This study collected information from patients (N = 2647) who underwent health check-ups at the Health Care Building of Wuhan Union Hospital between January 2019 and December 2020. Skeletal muscle mass was measured using bioelectrical impedance methods. The Asian Working Group on Sarcopenia diagnostic criteria were used to classify patients with sarcopenia. ASCVD risk was calculated using the Framingham Heart Study, and ASCVD risk ≥ 20% was considered high risk ASCVD. IBM SPSS 25.0 and GraphPad prism 8.0 software were used for data analysis and graphing.

RESULTS

The prevalence of hyperuricemia and sarcopenia was 23.57% and 15.34%, respectively. The occurrence of cardiovascular risk factors such as obesity, hypertension, diabetes mellitus, chronic kidney disease, and low HDL-Cemia was significantly higher in subjects with hyperuricemia combined with sarcopenia (OR = 1.734, 3.064, 1.61, 8.77 and 1.691 respectively, p < 0.05); Hyperuricemia and high-risk ASCVD were independently associated (OR = 1.355, 95% CI = 1.000-1.838, p = 0.04). Although there was no significant association between sarcopenia and high-risk ASCVD after controlling for confounders (OR = 1.274, 95% CI = 0.828-1.959, p = 0.271), sarcopenia combined with hyperuricemia significantly increased high-risk ASCVD (OR = 3.229, 95% CI 1.544-6.751, p = 0.002).

CONCLUSION

Hyperuricemia is independently associated with high-risk ASCVD; Sarcopenia and high-risk ASCVD did not show an independent relationship, but there was a synergistic effect of the two on ASCVD risk, which may imply that managing both hyperuricemia and sarcopenia may have a greater cardiovascular benefit.

Mechanism Investigation of Wuwei Shexiang Pills on Gouty Arthritis via Network Pharmacology, Molecule Docking, and Pharmacological Verification

Background

Gout is a common crystal-related arthritis caused by the deposition of monosodium urates (MSU). Tibetan medicine Wuwei Shexiang Pills (WSP) has been demonstrated to exhibit anti-inflammatory, antihyperuricemia, and antigout activities. However, the underlying mechanism is unknown.

Objectives

To explore the mechanisms of Wuwei Shexiang Pills on gouty arthritis via network pharmacology, molecule docking, and pharmacological verification.

Methods

The ingredients and targets of WSP were obtained by searching and screening in BATMAN-TCM and SwissADME. The targets involving the gout were acquired from public databases. The shared targets were put onto STRING to construct a PPI network. Furthermore, Metascape was applied for the GO and KEGG enrichment analysis to predict the biological processes and signaling pathways. And molecular docking was performed to validate the binding association between the key ingredients and the relative proteins of TNF signaling. Based on the serum pharmacology, the predicted antigout mechanism of WSP was validated in MSU-induced THP-1 macrophages. The levels of inflammatory cytokines and mRNA were measured by ELISA and qRT-PCR, respectively, and MAPK, NF-κB, and NLRP3 signaling-associated proteins were determined by western blot and immunofluorescence staining.

Results

48 bioactive ingredients and 165 common targets were found in WSP. The data showed that 5-Cis-Cyclopentadecen-1-One, 5-Cis-Cyclotetradecen-1-One, (-)-isoshyobunone, etc. were potential active ingredients. TNF signaling, HIF-1 signaling, and Jak-STAT signaling were predicted to be the potential pathways against gout. The molecule docking analysis found that most ingredients had a high affinity for p65, NLRP3, IL-1β, TNF-α, and p38. The data from in vitro experiment showed that WSP suppressed the production and gene expression of inflammatory cytokines. Furthermore, WSP could inhibit the activation of MAPK, NF-κB, and NLRP3 signaling pathways.

Conclusion

Our finding suggested that the antigout effect of WSP could be achieved by inhibiting MAPK, NF-κB, and NLRP3 signaling pathways. WSP might be a candidate drug for gouty treatment.

The Role of Urate in Cardiovascular Risk in Adolescents and Young Adults With Hypertension, Assessed by Pulse Wave Velocity

Background

Urate is increasingly recognized as a cardiovascular risk factor. It has been associated with hypertension, metabolic syndrome, obesity, chronic kidney disease and diabetes. Its prognostic role is less clear. The aim of our study was to evaluate the association between serum urate and pulse wave velocity, a measure of arterial stiffness in hypertensive adolescents and young adults.

Methods

269 adolescents and young adults with hypertension were included in the study. From all, anthropometric, blood pressure, pulse wave velocity and serum urate measurements were made. Variables were compared between sex, participants with or without obesity and with or without elevated urate.

Results

In multiple regression analysis for urate as dependent variable gender and diastolic pressure were found to be statistically significant. The difference between urate levels were found between boys and girls (p < 0.001), obese and non-obese (p < 0.001); however, pulse wave velocity did not differ between hyper- and eu-uricemic group (p = 0.162).

Conclusion

Associations between urate, gender, diastolic blood pressure and obesity were confirmed, however, no significant associations between pulse wave velocity and urate were detected.

Mediation effect of obesity on the association between triglyceride-glucose index and hyperuricemia in Chinese hypertension adults

The triglyceride glucose (TyG) index was regarded as a simple surrogate marker of insulin resistance (IR). It is confirmed that IR was significantly associated with hyperuricemia, and obesity was the risk factor for IR and hyperuricemia. However, the relationship between the TyG index and hyperuricemia and the potential role of obesity in Han Chinese hypertension are not entirely elucidated. A community‐based cross‐sectional study was conducted in 4551 hypertension patients aged 40–75 years with clinical and biochemical data. The TyG index was calculated as ln [fasting triglyceride (mg/dl) × fasting plasma glucose (mg/dl)/2]. Hyperuricemia was determined as serum uric acid ≥357μmol/L (6 mg/dl) for females and ≥417μmol/L (7 mg/dl) for males. Our study suggested that the TyG index was higher in patients with hyperuricemia than in those without (8.99±0.61, 8.70±0.59, p < .001). The prevalence of hyperuricemia in patients with the lowest (≤8.32), second (8.33–8.66), third (8.67–9.07) and the highest quartile (≥9.08) of the TyG index was 6.0%, 10.4%, 15.4%, 21.4%, respectively. Logistic regression analysis suggested that the higher quartile of TyG index was associated with increased hyperuricemia risk whether in crude or adjusted models (p < .05). Mediation analysis showed that all of our obesity indexes partially mediated the association between the TyG index and hyperuricemia to some extent. In Conclusions, the TyG index is significantly associated with hyperuricemia in hypertension patients among Han Chinese, obesity plays a partial mediation role in this relationship.

Early onset of hyperuricemia is associated with increased cardiovascular disease and mortality risk

BACKGROUND

Hyperuricemia is associated with cardiovascular mortality, but the association of the age at hyperuricemia onset with cardiovascular disease (CVD) and mortality is still unclear.

OBJECTIVE

The purpose of this study was to examine the associations of hyperuricemia onset age with CVD and all-cause mortality.

METHODS

A total of 82,219 participants free of hyperuricemia and CVD from 2006 to 2015 in the Kailuan study were included. The analysis cohort comprised 18,311 new-onset hyperuricemia patients and controls matched for age and sex from the general population. Adjusted associations were estimated using Cox models for CVD and all-cause mortality across a range of ages.

RESULTS

There were 1,021 incident cases of CVD (including 215 myocardial infarctions, 814 strokes) and 1459 deaths during an average of 5.2 years of follow-up. Patients with hyperuricemia onset at an age < 45 years had the highest hazard ratios (HRs) (1.78 (1.14-2.78) for CVD and 1.64 (1.04-2.61) for all-cause mortality relative to controls). The HRs of CVD and all-cause mortality were 1.32 (1.05-1.65) and 1.40 (1.08-1.81) for the 45-54 years age group, 1.23 (0.97-1.56) and 1.37 (1.11 to 1.72) for the 55-64 years age group, and 1.10 (0.88-1.39) and 0.88 (0.76-1.01) for the ≥ 65 years age group, respectively.

CONCLUSIONS

The age at hyperuricemia onset was identified as an important predictor of CVD and all-cause mortality risk, and the prediction was more powerful in those with a younger age of hyperuricemia onset. Early onset of hyperuricemia is associated with increased cardiovascular disease and mortality risk.

High serum uric acid within the normal range is a useful predictor of hypertension among Japanese community-dwelling elderly women

Background

The risk associated with serum uric acid (SUA) levels when within the normal range is unknown. This study aims to examine whether SUA within the normal range is a predictor of hypertension.

Methods

The subjects comprised 704 men aged 71 ± 9 (mean ± standard deviation) years and 946 women aged 70 ± 8 years recruited for a survey at the community based annual medical check-up. The main outcome was the presence of hypertension (antihypertensive medication and/or having SBP ≥140 mmHg and/or DBP ≥90 mmHg).

Results

At baseline, 467 (66.3%) men and 608 (64.3%) women had hypertension. Comparing to lowest quartile in women (SUA-1, uric acid < 4.1 mg/dL), the unadjusted odds ratios (ORs) [95% confidence interval (CI)] for hypertension of SUA-2 (4.1 to 4.7 mg/dL), SUA-3 (4.8 to 5.4 mg/dL), and SUA-4 (≥5.5 mg/dL) were 1.11 (0.78–1.59), 1.75 (1.20–2.55), and 1.89 (1.30–2.77), respectively. These associations were apparent even after adjustments for age, but ORs were attenuated after adjusting for all confounding factors. During a follow-up of 3.0 years, there were 35 (24.0%) hypertension cases in men and 51 (20.8%) in women. In women only, a significant association between increased SUA categories and incidence of hypertension was observed, and the multivariate-ORs (95% (CI) for incident hypertension of SUA-3 (4.5–5.2 mg/dL) and SUA-4 (≥5.3 mg/dL) were 2.23 (0.81–6.11) and 3.84 (1.36–10.8), respectively.

Conclusions

These results suggest that baseline SUA within the normal range could be an important predictor for incidence of hypertension in Japanese community-dwelling elderly women.

Ambulatory blood pressure in relation to interaction between dietary sodium intake and serum uric acid in the young

PURPOSE

We hypothesise that dietary sodium intake interacts with serum uric acid to influence blood pressure (BP) in children and adolescents. In the present study, we investigated ambulatory BP in relation to hyperuricaemia, dietary sodium intake and their interaction in children and adolescents with hypertension.

MATERIALS AND METHODS

A total of 616 study participants were 10-24 years old and had primary hypertension diagnosed after admission in a specialised inpatient ward. Ambulatory BP monitoring was performed during hospitalisation. 24-h urine was collected for measurements of electrolytes. Hyperuricaemia was defined as a serum uric acid of ≥327.25 μmol/L in patients <18 years old and of ≥420 and ≥360 μmol/L, respectively, in male and female patients ≥18 years old.

RESULTS

In adjusted analyses, patients with hyperuricaemia (n = 283), compared with those with normal serum uric acid, had similar 24-h systolic BP (131.7 mmHg, p = 0.54) and a significantly (p ≤ 0.005) lower 24-h diastolic BP (77.5 vs. 80.9 mmHg) and higher 24-h pulse pressure (54.2 vs. 51.7 mmHg). In similar adjusted analyses, 24-h ambulatory pulse pressure, but not systolic/diastolic BP (p ≥ 0.12), significantly differed across the quartile distributions of urinary sodium excretion (p for trend ≤ 0.04). Further adjusted analyses showed significant (p ≤ 0.04) interaction between serum uric acid and urinary sodium excretion in relation to 24-h systolic BP. In patients with hyperuricaemia (p = 0.04), but not those with normal serum uric acid (p = 0.13), 24-h systolic BP was significantly associated with urinary sodium excretion, with a 6.5 ± 2.1 mmHg difference between quartiles 4 and 1. Similar results were observed for daytime and night-time BP and pulse pressure.

CONCLUSIONS

Both hyperuricaemia and higher dietary sodium intake were associated with higher pulse pressure, and their interaction further heightened systolic BP.

Cardiovascular Risk in Children: Focus on Pathophysiological Aspects

Cardiovascular diseases are the leading cause of death, disability, and health care costs in industrialized countries. In general, cardiovascular diseases occur in adulthood, but cardiovascular damage, including stiffening of the arteries, begins very early. Already in the first decade of life, alterations that will favor the formation of atherosclerotic plaques may be present. Cardiovascular risk factors, associated with genetic predisposition, may trigger a sequence of pathophysiological changes which are associated with the progression of the atherosclerosis process. In this frame, the role of obesity has been increasingly emphasized. Different mechanisms linking obesity to cardiovascular disease have been postulated. Endothelial dysfunction and subclinical inflammation seem to be related to the worsening of cardiovascular risk factors in obese subjects and might have an essential role in the development of insulin resistance and the initiation and progression of atherosclerotic lesions. Excess weight, and in particular visceral adiposity, are associated with hypertrophy and hyperplasia of the adipocytes, increased secretion of adipokines and inflammatory cytokines and increase in serum uric acid levels. The list of obesity-related biomarkers associated with cardiovascular damage is rapidly expanding and their importance has already been described in children as well. Pathophysiological changes involved in determining early cardiovascular damage starting from childhood are discussed in this Special Issue.

Combined effects of dietary zinc at 3 years of age and obesity at 7 years of age on the serum uric acid levels of Korean children

BACKGROUND/OBJECTIVES

To assess the longitudinal associations of the antioxidant capacity of zinc and body mass index (BMI) with serum uric acid (SUA) in South Korean children.

SUBJECTS/METHODS

Using follow-up data from the Ewha Birth and Growth Cohort, we included subjects who were seen at 3 and 7 years of age (n = 183; 90 boys, 93 girls). Daily zinc intake and BMI were assessed at 3 and 7 years of age. SUA measured at 7 years was used as the outcome variable. Using a general linear model, the effects of dietary zinc intake and BMI on SUA were assessed. We also assessed the combined effect of early dietary zinc intake and BMI on SUA in children.

RESULTS

The dietary zinc intake at 3 years of age was negatively correlated (ρ = −0.18, P = 0.04), whereas the BMI at 7 years of age was positively correlated (r = 0.18, P = 0.01), with the SUA level at 7 years of age. The dietary zinc intake level at 3 years of age and the BMI level at 7 years of age were, together, significantly related to SUA in children at 7 years of age. SUA was lower in group 1 (normal-weight, high-zinc group) than in the other two groups (group 2: normal-weight, low-zinc and overweight, high-zinc group; and group 3: overweight, low-zinc group). Our results demonstrate the combined effect of zinc intake and BMI on SUA. The combined association remained significant in both the crude and adjusted models (P < 0.01).

CONCLUSIONS

SUA was related to combined BMI and dietary zinc intake, and increased zinc intake and normal body weight had a beneficial effect on reducing SUA in children.

Hyperuricemia and Hypertension, Coronary Artery Disease, Kidney Disease: From Concept to Practice

Since the publication of the Framingham Heart Study, which suggested that uric acid should no longer be associated with coronary heart disease after additional adjustment for cardiovascular disease risk factors, the number of publications challenging this statement has dramatically increased. The aim of this paper was to review and discuss the most recent studies addressing the possible relation between sustained elevated serum uric acid levels and the onset or worsening of cardiovascular and renal diseases. Original studies involving American teenagers clearly showed that serum uric acid levels were directly correlated with systolic and diastolic pressures, which has been confirmed in adult cohorts revealing a 2.21-fold increased risk of hypertension. Several studies involving patients with coronary artery disease support a role for serum uric acid level as a marker and/or predictor for future cardiovascular mortality and long-term adverse events in patients with coronary artery disease. Retrospective analyses have shown an inverse relationship between serum uric acid levels and renal function, and even a mild hyperuricemia has been shown to be associated with chronic kidney disease in patients with type 2 diabetes. Interventional studies, although of small size, showed that uric acid (UA)-lowering therapies induced a reduction of blood pressure in teenagers and a protective effect on renal function. Taken together, these studies support a role for high serum uric acid levels (>6 mg/dL or 60 mg/L) in hypertension-associated morbidities and should bring awareness to physicians with regards to patients with chronic hyperuricemia.

Higher Blood Uric Acid in Female Humans and Mice as a Protective Factor against Pathophysiological Decline of Lung Function

The oxidant/antioxidant imbalance plays a pivotal role in the lung. Uric acid (UA), an endogenous antioxidant, is highly present in lung tissue, however, its impact on lung function under pathophysiological conditions remains unknown. In this work, pharmacological and genetic inhibition of UA metabolism in experimental mouse models of acute and chronic obstructive pulmonary disease (COPD) revealed that increased plasma UA levels improved emphysematous phenotype and lung dysfunction in accordance with reduced oxidative stress specifically in female but not in male mice, despite no impact of plasma UA induction on the pulmonary phenotypes in nondiseased mice. In vitro experiments determined that UA significantly suppressed hydrogen peroxide (H₂O₂)-induced oxidative stress in female donor-derived primary human bronchial epithelial (NHBE) cells in the absence of estrogen, implying that the benefit of UA is limited to the female airway in postmenopausal conditions. Consistently, our clinical observational analyses confirmed that higher blood UA levels, as well as the SLC2A9/GLUT9 rs11722228 T/T genotype, were associated with higher lung function in elderly human females. Together, our findings provide the first unique evidence that higher blood UA is a protective factor against the pathological decline of lung function in female mice, and possibly against aging-associated physiological decline in human females.

Hyperuricemia is associated with a lower glomerular filtration rate in pediatric sickle cell disease patients

BACKGROUND

Sickle cell nephropathy (SCN) is a progressive disease that contributes significant morbidity and mortality in sickle cell disease (SCD), yet it remains poorly understood. Hyperuricemia negatively impacts renal function in the non-sickle cell population but is understudied in SCD.

METHODS

We performed a cross-sectional analysis of the first 78 pediatric SCD patients enrolled in a cohort study. The mechanism of development of hyperuricemia (defined, serum uric acid (UA) ≥ 5.5 mg/dL) was characterized as a result of either UA overproduction or inefficient renal excretion by the Simkin index and fractional clearance of urate (FCU) equations. Associations between hyperuricemia and albuminuria or estimated glomerular filtration rate (eGFR) were determined by linear regression.

RESULTS

The prevalence of hyperuricemia in this young population (mean age 11.6 ± 3.77 years) was 34.2%. Only 1 hyperuricemic participant overproduced UA by Simkin index, while 62.5% were inefficient renal excretors of UA (FCU < 4%). Hyperuricemia was associated with a significant decrease in average eGFR, -27 ml/min/1.73m² below normouricemia (mean eGFR 151.6 ± 40.32), p = 0.0122. Notably, the previously accepted association between decline of eGFR with age is significantly modified by hyperuricemia stratification, where hyperuricemia explains 44% of the variance in eGFR by age (R² = 0.44, p = 0.0004) and is nonsignificant in normouricemia (R² = 0.07, p = 0.0775).

CONCLUSION

These findings indicate that hyperuricemia may be associated with early eGFR decline in SCN. This association must be further characterized in prospective cohort studies in SCN, and hyperuricemia must be investigated as a potential therapeutic target for SCN.

Plasma levels of matrix metalloproteinase-9 are elevated in individuals with hypertensive crisis

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) participates in the degradation of components of the extracellular matrix and it is involved in vascular remodeling and vasomotor changes. The aim of this study was to investigate the plasma levels of MMP-9 in acute vascular alterations due to hypertensive crisis.

METHODS

This cross-sectional study was performed in 40 normotensive (NT) and 58 controlled hypertensive subjects (CHyp) followed up in outpatient clinic. Moreover, 57 patients with hypertensive emergency (HypEmerg) and 43 in hypertensive urgency (HypUrg), seen in emergency department, were also included. Hypertensive crisis was divided into HypEmerg, which was characterized by levels of systolic blood pressure (BP) ≥ 180 mmHg and/or diastolic BP ≥ 120 mmHg complicated with target-organ damage (TOD), and HypUrg, defined by BP elevation without TOD. Univariate and multivariate regression analysis was performed to identify the influence of independent variables on MMP-9 levels. A p-value < 0.05 was considered statistically significant.

RESULTS

The mean age was 43.5 years in the NT group (11 men); 57.7 years in the CHyp group (29 men); 59.4 years in the HypUrg group (21 men) and 62.4 years in the HypEmerg group (31 men). The age was statistically different in the NT group compared to other 3 groups. The mean BP was 116.5 ± 13.9/72.4 ± 10.6 mmHg for NT, 123.2 ± 12.6/79 ± 9.2 for CHyp, 194.1 ± 24.3/121.4 ± 17.3 for HypUrg and 191.6 ± 34.3/121.7 ± 18.8 mmHg for HypEmerg, respectively (p-value< 0.0001 between groups). MMP-9 levels were statistically different between the HypEmerg (2.31 ± 0.2 ng/mL) and HypUrg groups (2.17 ± 0.3 ng/mL) compared to the NT (1.94 ± 0.3 ng/mL) (p-value < 0.01 and p-value < 0.05, respectively) and CHyp groups (1.92 ± 0.2 ng/mL) (p-value < 0.01). Uric acid was the only independent variable for predicting MMP-9 levels (p-value = 0.001).

CONCLUSION

MMP-9 concentrations are significantly higher in the hypertensive crisis groups (urgency and emergency) compared to the control groups. Therefore, MMP-9 may be a biomarker or mediator of pathophysiologic pathways in cases of acute elevations of blood pressure.

A Randomized Study of the Effect of Replacing Sugar-Sweetened Soda by Reduced Fat Milk on Cardiometabolic Health in Male Adolescent Soda Drinkers

Soda consumption in adolescents has been linked to poorer metabolic outcomes. We tested whether replacing soda with reduced fat milk would improve features of atherogenic dyslipidemia and other cardiometabolic risk factors. Thirty overweight and obese adolescent boys who were habitual consumers of sugar-sweetened beverages were randomly assigned to consume 24 oz/day of sugar-sweetened soda or an energy equivalent of reduced fat (2%) milk for 3 weeks with crossover to the alternate beverage after a ≥ 2 weeks washout. Plasma lipids and lipoproteins and other laboratory measures were assessed after each beverage period. Lipid and lipoprotein measurements, C-reactive protein, and serum transaminases did not differ significantly between the soda and milk phases of the study. Systolic blood pressure z-score and uric acid concentration were significantly lower after consuming milk compared to soda. Milk consumption also significantly decreased plasma glucosyl ceramide (d18:1/C16:0) and lactosylceramides (d18:1/C16:0 and d18:1/C18:0). While no effects of replacing soda with milk on lipid and lipoprotein measurements were observed in these normolipidemic weight-stable adolescent boys, decreases in systolic blood pressure, uric acid, and glycosphingolipids suggest that an overall favorable effect on cardiometabolic risk can be achieved following a short-term dietary intervention.

Age-differential association between serum uric acid and incident hypertension

Increasing evidence suggests a positive association between the serum uric acid (SUA) level and incident hypertension. However, the association has been inconsistent based on age, sex, body mass index, and lipid profiles. Thus, we investigated whether there is an interaction between SUA and other risk factors on incident hypertension in the Korean general population. In this study, 808 participants aged 40-79 years were included. They were free of hypertension and major cardiovascular disease at baseline. Incident hypertension was defined as systolic blood pressure (SBP) ≥ 140 mmHg, diastolic blood pressure (DBP) ≥ 90 mmHg, or use of antihypertensive medication. To investigate whether the association between SUA and incident hypertension is modified by other risk factors for hypertension, a generalized linear model and Z test were used. During the mean follow-up of 3.3 years, 11.5% of men and 10.7% of women developed hypertension. The association between SUA and incident hypertension was inconsistent according to participant age (p for interaction = 0.009). The association between SUA level and incident hypertension was positively significant among people aged < 55 years (relative risk 1.74 per 1.0 mg/dL of SUA; p = 0.002), but there was no significant association among people aged ≥ 55 years (p = 0.894). In a secondary analysis, the SUA level was not associated with an increase in SBP, but positively associated with DBP. We observed an age-differential association between SUA level and incident hypertension among Koreans. An increased SUA level can be a trigger for hypertension through early vascular changes in the middle-aged population.

Physiology of Hyperuricemia and Urate-Lowering Treatments

Gout is the most common form of inflammatory arthritis and is a multifactorial disease typically characterized by hyperuricemia and monosodium urate crystal deposition predominantly in, but not limited to, the joints and the urinary tract. The prevalence of gout and hyperuricemia has increased in developed countries over the past two decades and research into the area has become progressively more active. We review the current field of knowledge with emphasis on active areas of hyperuricemia research including the underlying physiology, genetics and epidemiology, with a focus on studies which suggest association of hyperuricemia with common comorbidities including cardiovascular disease, renal insufficiency, metabolic syndrome and diabetes. Finally, we discuss current therapies and emerging drug discovery efforts aimed at delivering an optimized clinical treatment strategy.

Relation of uric acid level to rapid kidney function decline and development of kidney disease: The Jackson Heart Study

Whether elevated uric acid (UA) is an independent risk factor for chronic kidney disease (CKD) is not well established. The authors evaluated the relationship of UA with rapid kidney function decline (RKFD) and incident CKD among 3702 African Americans (AAs) in the Jackson Heart Study with serum UA levels measured at baseline exam (2000-2004). RKFD was defined as ≥ 30% eGFR loss and incident CKD as development of eGFR < 60 mL/min/1.73 m2 with a ≥ 25% decline in eGFR between baseline and exam 3 (2009-2013). RKFD and CKD were found in 11.4% and 7.5% of the participants, respectively. In a fully adjusted model, the odds of RKFD (OR, 1.8; 95% CI, 1.25-2.49) and incident CKD (OR, 2.00; 95% CI, 1.31-3.06) were significantly higher among participants in the top UA quartile vs bottom quartile. In the JHS, elevated UA was significantly associated with RKFD and incident CKD.

Uric acid and blood pressure: exploring the role of uric acid production in The Maastricht Study

OBJECTIVE

Accumulation of reactive oxygen species by increased uric acid production has been suggested as a possible underlying mechanism for the association between uric acid and high blood pressure (BP). We, therefore, investigated the association between serum uric acid concentration and 24-h urinary uric acid excretion, as proxy for uric acid production, with ambulatory 24-h blood pressure and hypertension.

METHODS

Cross-sectional analyses were conducted among 2555 individuals [52% men, mean age 60.0 ± 8.2 years; 27% type 2 diabetes (by design)] from The Maastricht Study. Multivariable regression analyses were performed to investigate the association of serum uric acid and 24-h urinary uric acid excretion with 24-h pulse pressure, 24-h mean arterial pressure (MAP), and hypertension.

RESULTS

After adjustment for traditional hypertension risk factors, serum uric acid concentration (per SD of 81 μmol/l) was associated with higher 24-h MAP [β 0.63 mmHg; confidence interval (CI) 0.27-1.00] and positively associated with hypertension (odds ratio 1.43; CI 1.27-1.61). Urinary uric acid excretion (per SD of 140 mg/day/1.73 m) was associated with higher 24-h MAP (β 0.79 mmHg; CI 0.46-1.12) and with hypertension (odds ratio 1.13; CI 1.02-1.25). There was no significant association between serum and 24-h urinary uric acid excretion with 24-h pulse pressure. There was no interaction with sex or age for the aforementioned associations.

CONCLUSION

Higher serum and urinary uric acid concentrations were associated with higher 24-h MAP and hypertension. These results suggest that serum and 24-urinary uric acid concentrations, the latter as proxy for uric acid production are, independent of each other, associated with BP and hypertension.

Assessment of cardiovascular risk profile based on measurement of tophus volume in patients with gout

Hyperuricemia and gout are associated with increased risk of cardiovascular disease and metabolic syndrome. The aim of this study was to evaluate the correlation of total tophus volumes, measured using dual-energy computed tomography, with cardiovascular risk and the presence of metabolic syndrome. Dual-energy computed tomography datasets from 91 patients with a diagnosis of gout were analyzed retrospectively. Patients who received urate lowering therapy were excluded to avoid the effect on tophus volume. The total volumes of tophaceous deposition were quantified using automated volume assessment software. The 10-year cardiovascular risk using the Framingham Risk Score and metabolic syndrome based on the Third Adult Treatment Panel criteria were estimated. Fifty-five and 36 patients with positive and negative dual-energy computed tomography results, respectively, were assessed. Patients with positive dual-energy computed tomography results showed significantly higher systolic blood pressure, diastolic blood pressure, fasting glucose, and higher prevalence of chronic kidney disease, compared with those with negative dual-energy computed tomography results. The total tophus volumes were significantly correlated with the Framingham Risk Score, and the number of metabolic syndrome components (r = 0.22 and p = 0.036 and r = 0.373 and p < 0.001, respectively). The total tophus volume was one of the independent prognostic factors for the Framingham Risk Score in a multivariate analysis. This study showed the correlation of total tophus volumes with cardiovascular risk and metabolic syndrome-related comorbidities. A high urate burden could affect unfavorable cardiovascular profiles.

Salivary uric acid and C-reactive protein associations with hypertension in Midwestern Latino preadolescents and their parents

Latino families face increased risk for hypertension. Serum-based uric acid and C-reactive protein have been linked to hypertension. However, a paucity of salivary biomarker data exists in this area for Latino families. Using salivary biomarkers enables less invasive options for biomedical and biosocial research, which is especially important among vulnerable populations facing increased health disparities. This study examined the associations between salivary uric (sUA) acid, salivary C-reactive protein (sCRP), and hypertension among 151 participants (57 children, 57 mothers, 37 fathers) from 57 Midwestern Latino families. Participants self-administered the salivary samples, and blood pressure was measured by researchers. Results showed sUA was associated across family members, and child hypertension was related to parents' hypertension. sCRP was only related to sUA in fathers. Findings highlight the family-level health connections, along with the importance for further investigations using salivary biomarkers with Latinos, and the need for a robust sUA cut-off for hyperuricemia.

Effect of Febuxostat on Ambulatory Blood Pressure in Subjects With Hyperuricemia and Hypertension: A Phase 2 Randomized Placebo-Controlled Study

Background

Hyperuricemia is associated with hypertension, with elevated serum uric acid levels postulated to have a causal role in the development of hypertension. Consequently, serum uric acid reduction may help lower blood pressure (BP). A Phase 2, double‐blind, placebo‐controlled trial was conducted to assess the potential BP‐lowering effects of the xanthine oxidase inhibitor febuxostat in subjects with hypertension and hyperuricemia (serum uric acid ≥0.42 mmol/L [≥7.0 mg/dL]).

Methods and Results

Subjects (n=121) were randomized 1:1 to febuxostat 80 mg once daily or to placebo. The primary end point was change from baseline to Week 6 in 24‐hour mean ambulatory systolic BP (SBP). Additional end points included the following: change from baseline to Week 3 in 24‐hour mean SBP and changes from baseline to Weeks 3 and 6 in 24‐hour mean ambulatory diastolic BP, serum uric acid, mean daytime and nighttime ambulatory SBP/diastolic BP, and clinic SBP/diastolic BP. For the overall study population, there were no significant differences between febuxostat and placebo for changes from baseline to Weeks 3 or 6 in ambulatory, daytime or nighttime, or clinic SBP or diastolic BP. However, in a preplanned subgroup analysis, there was a significant decrease in SBP from baseline to Week 6 in subjects with normal renal function (estimated glomerular filtration rate ≥90 mL/min) treated with febuxostat versus placebo; least squares mean difference, −6.7; 95% confidence interval −13.3 to −0.0; P=0.049.

Conclusions

This study suggests that febuxostat may lower BP in hyperuricemic patients with hypertension and normal renal function; further studies should be conducted to confirm this finding.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01496469.

The problem of cardio-renal diseases in patients with gout

BACKGROUNDS

Although evidence is mounting on the role of hyperuricemia in cardio-renal disease, continuing doubt remains as to whether hyperuricemia can be considered a major causal cardiovascular risk factor. In addition, available data suggest that treatment may be beneficial, even in the absence of overt gout, when hyperuricemia accompanies other clinical conditions, such as urate deposition, advanced chronic kidney disease, or cardiovascular risk factors.

METHODS AND RESULTS

Analysis of the literature suggests there would be sufficient evidence warranting clinical trials to determine whether lowering uric acid levels would be clinically beneficial in the prevention or treatment of cardiovascular and renal diseases.

CONCLUSION

Under a practical profile, it becomes progressively more important to investigate the possibility of reducing serum uric acid levels in the general population below the level of 5.0 mg/dL.

Untargeted Metabolomics Provides Insight into the Mechanisms Underlying Resistant Hypertension

BACKGROUND

Resistant hypertension (RH) affects about 15-20% of treated hypertensive patients worldwide. RH increases the risk of cardiovascular events such as myocardial infarction and stroke by 50%. The pathological mechanisms underlying resistance to treatment are still poorly understood.

OBJECTIVE

The main goal of this pilot study was to determine and compare plasma metabolomic profiles in resistant and non-resistant hypertensive patients.

METHODS

We applied untargeted metabolomic profiling in plasma samples collected from 69 subjects with RH and 81 subjects with controlled hypertension. To confirm patients' compliance to antihypertensive treatment, levels of selected drugs and their metabolites were determined in plasma samples with the LC-ESI-TOF/MS technique.

RESULTS

The results showed no statistically significant differences in the administration of antihypertensive drug in the compared groups. We identified 19 up-regulated and 13 downregulated metabolites in the RH.

CONCLUSION

The metabolites altered in RH are linked to oxidative stress and inflammation, endothelium dysfunction, vasoconstriction and cell proliferation. Our results may generate new hypothesis about RH development and progression.

Comparison of lercanidipine plus hydrochlorothiazide vs. lercanidipine plus enalapril on micro and macrocirculation in patients with mild essential hypertension

Dihydropyridine calcium channel blockers may possess antioxidant properties, and might improve micro and macrovascular structure and function. Combination treatment with an ACE inhibitor may have additional advantages, compared with a thiazide diuretic. The aim of the present study is to investigate the effects of a short-term treatment with lercanidipine, and to compare two combination treatments: lercanidipine + enalapril vs. lercanidipine + hydrochlorothiazide on structural alterations in retinal arterioles, on skin capillary density and on large artery distensibility. Thirty essential hypertension patients are included in the study, and treated for 4 weeks with lercanidipine 20 mg per day orally. Then, they were treated for 6 months with lercanidipine + enalapril (n = 15) or lercanidipine + hydrochlorothiazide (n = 15) combinations. Investigations were performed on basal condition, after appropriate wash out of previous treatments, after 4 weeks of lercanidipine monotherapy treatment, and at the end of the combination treatment. Non-invasive measurements of wall-to-lumen ratio (WLR) and other morphological parameters of retinal arterioles were performed using either scanning laser Doppler flowmetry or adaptive optics. Capillary density was evaluated by capillaroscopy, while pulse wave velocity was measured, and central blood pressures were assessed by pressure waveform analysis. A significant improvement of WLR and other indices of retinal artery structure is observed with both technical approaches after treatment with lercanidipine alone, with a further improvement after treatment with lercanidipine + enalapril, while after treatment with lercanidipine + hydrochlorothiazide, the improvement is partially blunted. Central systolic and diastolic blood pressures are similarly reduced by both therapeutic strategies. Capillary density is increased only after treatment with lercanidipine + enalapril. In conclusion, lercanidipine both in monotherapy and in combination with enalapril but not with hydrochlorothiazide is able to improve microvascular structure; on the other hand, a decrease in central blood pressure is observed with both therapeutic combinations.

Associations of plasma uric acid and purine metabolites with blood pressure in children: the KOALA Birth Cohort Study

OBJECTIVE

Elevated serum uric acid concentration has been associated with high blood pressure (BP) and hypertension. A putative underlying mechanism is the accumulation of reactive oxygen species when uric acid is generated by an increased enzyme activity of xanthine oxidase (XO). The aims of the present study were to investigate the associations between plasma uric acid concentration, purine metabolite ratios, as proxies for increased XO activity, and SBP and DBP in school-age children.

METHODS

Cross-sectional analyses were performed in 246 children (46% boys; mean age 7.1 years) from the Dutch KOALA Birth Cohort Study. Purine metabolites were determined with ultra-performance liquid chromatography-tandem mass spectrometry. During a home visit, a nurse collected a blood sample and measured BP three times; in addition, parents measured their child's BP on three consecutive days, in the morning and evening. Generalized estimating equations were used for analyses while controlling for variables such as sex, age, BMI, physical activity, and dietary intake.

RESULTS

In multivariable analysis, uric acid (per SD of 38 μmol/l) was associated with DBP z-scores [sβ 0.07; confidence interval (CI), 0.01-1.14], but not with SBP z-scores. Higher ratios of uric acid/xanthine (per SD of 138) (sβ 0.09; CI, 0.01-0.17) and xanthine/hypoxanthine (per SD of 321) (sβ 0.08; CI, 0.02-0.17) were associated with higher DBP z-scores, but not with SBP z-scores.

CONCLUSION

In school-age children, uric acid and the ratios of uric acid/xanthine and xanthine/hypoxanthine were significantly associated with DBP z-scores. Suggesting that, both uric acid concentration and increased XO activity are associated with BP.

Serum uric acid concentration is associated with hypertensive retinopathy in hypertensive chinese adults

BACKGROUND

This cross sectional investigation included 12,966 subjects with hypertension, a cohort of the China Stroke Primary Prevention Trial (CSPPT), a randomized, multicenter clinical trial. This study aimed to explore the correlation between serum uric acid (SUA) concentration and hypertensive retinopathy in hypertensive adults.

METHODS

Diagnosis of hypertensive retinopathy was determined by non-mydriatic fundus photography and classified with Keith-Wagener-Barker (KWB) system. The correlation of SUA levels with hypertensive retinopathy prevalence and severity was assessed by statistical analysis.

RESULTS

9848 (75.95%) subjects were diagnosed with hypertensive retinopathy with the following retinopathy grade distribution: grade 1: 58.80%, grade 2: 14.81%, and grade 3-4: 2.34%. SUA levels were significantly associated with hypertensive retinopathy prevalence. Patients with hypertensive retinopathy had higher SUA levels than those without hypertensive retinopathy. Patients in the highest uric acid quartile had an odds ratio for hypertensive retinopathy of 1.21 compared to patients in the lowest uric acid quartile (OR = 1.21, 95% CI: 1.05-1.40, P = 0.008). When compared to the non-hyperuricemia group, those in the hyperuricemia group had an odds ratio for hypertensive retinopathy of 1.18(OR = 1.18, 95% CI: 1.05-1.33, P = 0.004). Every 1 mg/dl increase in uric acid concentration was significantly associated with a 6% higher odds of hypertensive retinopathy (OR = 1.06, 95% CI: 1.02-1.10, P = 0.002).

CONCLUSIONS

The prevalence of hypertensive retinopathy was high (75.95%) among hypertensives in our patients cohort. In addition, SUA concentration was significantly associated with hypertensive retinopathy.

Effect of Uric Acid Lowering on Renin-Angiotensin-System Activation and Ambulatory BP: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Higher serum uric acid levels, even within the reference range, are strongly associated with increased activity of the renin-angiotensin system (RAS) and risk of incident hypertension. However, the effect of lowering serum uric acid on RAS activity in humans is unknown, although the data that lowering serum uric acid can reduce BP are conflicting.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a double-blind placebo-controlled trial conducted from 2011 to 2015, we randomly assigned 149 overweight or obese adults with serum uric acid ≥5.0 mg/dl to uric acid lowering with either probenecid or allopurinol, or to placebo. The primary endpoints were kidney-specific and systemic RAS activity. Secondary endpoints included mean 24-hour systolic BP, mean awake and asleep BP, and nocturnal dipping.

RESULTS

Allopurinol and probenecid markedly lowered serum uric acid after 4 and 8 weeks compared with placebo (mean serum uric acid in allopurinol, probenecid, and placebo at 8 weeks was 2.9, 3.5, and 5.6 mg/dl, respectively). The change in kidney-specific RAS activity, measured as change in the median (interquartile range) renal plasma flow response to captopril (in ml/min per 1.73 m2) from baseline to 8 weeks, was -4 (-25 to 32) in the probenecid group (P=0.83), -4 (-16 to 9) in the allopurinol group (P=0.32), and 1 (-21 to 17) in the placebo group (P=0.96), with no significant treatment effect (P=0.77). Similarly, plasma renin activity and plasma angiotensin II levels did not significantly change with treatment. The change in mean (±SD) 24-hour systolic BPs from baseline to 8 weeks was -1.6±10.1 with probenecid (P=0.43), -0.4±6.1 with allopurinol (P=0.76), and 0.5±6.0 with placebo (P=0.65); there was no significant treatment effect (P=0.58). Adverse events occurred in 9%, 12%, and 2% of those given probenecid, allopurinol, or placebo, respectively.

CONCLUSIONS

In contrast to animal experiments and observational studies, this randomized, placebo-controlled trial found that uric acid lowering had no effect on kidney-specific or systemic RAS activity after 8 weeks or on mean systolic BP. These data do not support the hypothesis that higher levels of uric acid are a reversible risk factor for increased BP.

Hyperuricemia, the kidneys, and the spectrum of associated diseases: a narrative review

Hyperuricemia (elevated serum uric acid) is prevalent, and an important mediator of gout, an increasingly common condition. In addition, hyperuricemia is associated with metabolic syndrome, diabetes, hypertension, and kidney and cardiovascular diseases. Although it remains controversial whether hyperuricemia is a causal factor for kidney disease, the kidneys play a major role in the regulation of serum uric acid levels. Approximately two-thirds of the uric acid produced in humans is excreted by the kidneys. The handling of urate in the renal proximal tubule is extensive, as uric acid undergoes filtration, reabsorption, and secretion. Variations in renal urate handling have been shown to influence the risk of gout. In observational studies, hyperuricemia has been shown to predict kidney disease onset and progression, with a variety of mechanisms implicated. Because of this close association between hyperuricemia and kidney disease, and due to limited studies on the topic, it is important to conduct future studies on the treatment of hyperuricemia to slow kidney disease progression and improve cardiovascular survival in patients with chronic kidney disease. Furthermore, it is important to monitor for gout in patients with kidney disease and to follow the guidelines for treatment of hyperuricemia in this group of patients. This narrative review provides an in-depth discussion of the link between serum uric acid levels, renal handling of uric acid, and diseases associated with dysfunction in uric acid homeostasis.

Serum uric acid as a predictor of future hypertension: Stratified analysis based on body mass index and age

BACKGROUND

Serum uric acid level is a predictor of future hypertension. However, its dependence on body mass index or age is unclear.

METHODS

We examined 26,442 Japanese males aged 18-60years free from hypertension or diagnosed cardiovascular disease at baseline followed up between 2000 and 2010. Participants were categorized into three groups according to the tertile of serum uric acid levels [mg/dL; 1st (reference): 0.1-5.3; 2nd: 5.4-6.2; 3rd: 6.3-11.6]. Incident hypertension was defined as newly detected blood pressure≥140/90mmHg and/or antihypertensive drugs initiation. Body mass index (<25kg/m(2) vs. ≥25kg/m(2)) and age (<40years vs. ≥40years) were stratified into two groups.

RESULTS

During a mean follow-up of 7.2years, there were 11,361 (43%) hypertension cases. Mean serum uric acid levels (mg/dL) at baseline in each group were 1st tertile, 4.6; 2nd tertile, 5.8; and 3rd tertile, 7.0. The cumulative incident hypertension rate was significantly higher in the 3rd tertile (50.8%) than in the 1st (37.4%). Multiple-adjusted hazard ratios (95% confidence interval) for incident hypertension compared with 1st tertile were 1.01 (0.96-1.05) and 1.15 (1.10-1.21) in the 2nd and 3rd tertile, respectively. There was a significant interaction between age and serum uric acid level (p for interaction=0.035). In subjects aged ≥40years, the 3rd serum uric acid group showed higher hazard ratios [1.48 (1.38-1.59)].

CONCLUSION

High serum uric acid level was associated with future hypertension in young and middle-aged Japanese males. This association was stronger among subjects ≥40years old.

Serum uric acid is an independent predictor for developing prehypertension: a population-based prospective cohort study

Although the prevalence of prehypertension is rapidly increasing in China, the medical community has paid little attention to its prevention. Prior studies have demonstrated that uric acid directly contributes to vascular remodelling and endothelial dysfunction. However, few prospective studies have assessed the relationship between serum uric acid and prehypertension. We therefore designed a larger-scale cohort study to examine whether uric acid level is a predictive factor for developing prehypertension in adults. Participants were recruited from Tianjin Medical University General Hospital-Health Management Centre. A prospective assessment (n=15 143) was performed. Participants without a history of hypertension or prehypertension were followed up for 2 to 6 years with a median follow-up duration of 2.8 years. Serum uric acid levels and blood pressure were assessed yearly during the follow-up. Adjusted Cox proportional hazards regression models were used to assess relationships between the quintiles of uric acid levels and the incidence of prehypertension. The incidence of prehypertension was 191 per 1000 person-years. In the final multivariate models, the hazard ratios (95% confidence interval) for prehypertension across uric acid quintiles were 1.00 (reference), 0.98 (0.90-1.07), 1.01 (0.93-1.10), 1.09 (1.001-1.20) and 1.17 (1.06-1.29) (P for trend <0.001), respectively. This population-based prospective cohort study has demonstrated that uric acid level is an independent predictor for developing prehypertension.

Role of Dietary Components in Modulating Hypertension

Hypertension is a major health issue, particularly in medically underserved populations that may suffer from poor health literacy, poverty, and limited access to healthcare resources. Management of the disease reduces the risk of adverse outcomes, such as cardiovascular or cerebrovascular events, vision impairment due to retinal damage, and renal failure. In addition to pharmacological therapy, lifestyle modifications such as diet and exercise are effective in managing hypertension. Current diet guidelines include the DASH diet, a low-fat and low-sodium diet that encourages high consumption of fruits and vegetables. While the diet is effective in controlling hypertension, adherence to the diet is poor and there are few applicable dietary alternatives, which is an issue that can arise from poor health literacy in at-risk populations. The purpose of this review is to outline the effect of specific dietary components, both positive and negative, when formulating a dietary approach to hypertension management that ultimately aims to improve patient adherence to the treatment, and achieve better control of hypertension.

Related factors of serum uric acid in patients with primary hypertension and hyperhomocysteinemia

OBJECTIVE

To investigate the related factors of serum uric acid in patients with primary hypertension and hyperhomocysteinemia.

METHODS

One hundred and ten patients with primary hypertension and hyperhomocysteinemia (homocysteine levels >10 μmol/L) were enrolled into this study, ages from 18 years to 75 years. They were divided into the normal serum uric acid group which contained 74 cases patients (41 cases of male and 33 cases of female) and the hyperuricemia group which contained 36 cases patients (20 cases of male and 16 cases of female). Plasma concentrations of homocysteine, serum uric acid, serum folic acid, blood sugar, triglyceride, total cholesterol, serum low density lipoprotein cholesterol, serum high density lipoprotein cholesterol, blood urea nitrogen, and creatinine were detected in these patients, and the deference of them between the two groups was compared. And then the risk factors of serum uric acid with univariate analysis and multivariate analysis by logistic regression analysis were analyzed.

RESULTS

The result of multivariate analysis showed that the incidence of serum uric acid in patients with primary hypertension and hyperhomocysteinemia had significant relationships with systolic blood pressure (OR [odds ratio]: 1.132, 95%CI [confidence interval]: 1.003~1.290, p = 0.043), diastolic blood pressure (OR: 1.353 95%CI: 1.023~1.789, p = 0.034, homocysteine (OR: 1.264, 95%CI: 1.016~1.573, p = 0.035), triglyceride (OR: 9.726, 95%CI: 1.288~73.466, p = 0.027), and creatinine (OR: 1.031, 95%CI: 1.005~1.508, p = 0.018).

CONCLUSION

The indices of systolic blood pressure, diastolic blood pressure, homocysteine, triglyceride, and creatinine were important risk factors of serum uric acid in patients with primary hypertension and hyperhomocysteinemia. It is of great significance to measure multiple risk factors in patients with primary hypertension and hyperhomocysteinemia.

Increased Serum Uric Acid Levels Blunt the Antihypertensive Efficacy of Lifestyle Modifications in Children at Cardiovascular Risk

Primary hypertension is a growing concern in children because of the obesity epidemic largely attributable to western lifestyles. Serum uric acid is known to be influenced by dietary habits, correlates with obesity, and could represent a risk factor for hypertension. Preliminary studies in children highlighted uric acid as a potentially modifiable risk factor for the prevention and treatment of hypertension. The effect of lifestyle changes (increase of physical activity and dietary modifications) on blood pressure values, weight status, and serum uric acid levels in a cohort of 248 children referred for cardiovascular risk assessment were evaluated over a mean 1.5-year follow-up. At baseline, 48% of children were obese and 50% showed blood pressure values >90th percentile. At follow-up, a significant improvement in weight class (24% obese;P<0.0001) and blood pressure category (22% >90th percentile;P<0.0001) was found. Systolic blood pressure z-score (P<0.0001), uric acid value (P=0.0056), and puberty at baseline (P=0.0048) were independently associated with higher systolic blood pressure z-score at follow-up, whereas a negative association was observed with body mass index z-score decrease during follow-up (P=0.0033). The risk of hypertension at follow-up was associated with body mass index (P=0.0025) and systolic blood pressure (P<0.0001) z-score at baseline and inversely related to delta body mass index (P=0.0002), whereas the risk of showing hypertension ≥99th percentile was more than doubled for each baseline 1 mg/dL increase of serum uric acid (P=0.0130). Uric acid is a powerful determinant of blood pressure over time, independent of lifestyle modifications.

Risk Factors in Adolescent Hypertension

Hypertension is a complex and multifaceted disease, with many contributing factors. While diet and nutrition are important influences, the confounding effects of overweight and obesity, metabolic and genetic factors, racial and ethnic predispositions, socioeconomic status, cultural influences, growth rate, and pubertal stage have even more influence and make diagnosis quite challenging. The prevalence of hypertension in adolescents far exceeds the numbers who have been diagnosed; studies have found that 75% or more go undiagnosed. This literature review summarizes the challenges of blood pressure classification in adolescents, discusses the impact of these confounding influences, and identifies actions that will improve diagnosis and treatment outcomes.

Elevated uric acid and obesity-related cardiovascular disease risk factors among hypertensive youth

BACKGROUND

Uric acid (UA) is associated with high blood pressure in adolescents and with left ventricular hypertrophy (LVH) and cardiovascular disease (CVD) in adults. We sought to determine if UA is independently associated with CVD risk factors and left ventricular mass (LVM) over time in hypertensive youth.

METHODS

This was a 1-year prospective observational study of hypertensive children aged 3-19 years. Cross-sectional and longitudinal associations of serum UA with CVD risk factors and LVM were explored.

RESULTS

Of the 49 children who completed both the baseline and 12-month assessments, at baseline the mean age was 13.8 years and mean UA was 5.5 mg/dL; 24% had elevated UA, 51% were overweight/obese and 39% had LVH. Measures of adiposity, low high-density lipoprotein cholesterol, high-sensitivity C-reactive protein, LVM and LVH were all significantly associated with elevated UA at baseline, but not with change over time. Each 1 mg/dL increase in baseline UA was associated with a 2.5 g/m(2.7) increase in the LVM index at follow-up (95% confidence interval 0.64, 4.39; p = 0.01); after adjustment for age, sex, race, body mass index z-score, change in UA, time, blood pressure and medication use, this association was no longer significant.

CONCLUSIONS

Hypertensive children with elevated UA have a higher prevalence of obesity-related CVD risk factors. Among hypertensive children, UA may be a marker of adiposity and not an independent CVD risk factor.

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.

ABCG2: the molecular mechanisms of urate secretion and gout

The human propensity for high levels of serum uric acid (SUA) is a trait that has defied explanation. Is it beneficial? Is it pathogenic? Its role in the human diseases like gout and kidney stones was discovered over a century ago [Richette P, Bardin T. Lancet 375: 318-328, 2010; Rivard C, Thomas J, Lanaspa MA, Johnson RJ. Rheumatology (Oxford) 52: 421-426, 2013], but today emerging new genetic and epidemiological techniques have revived an age-old debate over whether high uric acid levels (hyperuricemia) independently increase risk for diseases like hypertension and chronic kidney disease [Feig DI. J Clin Hypertens (Greenwich) 14: 346-352, 2012; Feig DI, Madero M, Jalal DI, Sanchez-Lozada LG, Johnson RJ. J Pediatr 162: 896-902, 2013; Feig DI, Soletsky B, Johnson RJ. JAMA 300: 924-932, 2008; Wang J, Qin T, Chen J, Li Y, Wang L, Huang H, Li J. PLoS One 9: e114259, 2014; Zhu P, Liu Y, Han L, Xu G, Ran JM. PLoS One 9: e100801, 2014]. Part of the mystery of the role uric acid plays in human health stems from our lack of understanding of how humans regulate uric acid homeostasis, an understanding that could shed light on the historic role of uric acid in human adaptation and its present role in human pathogenesis. This review will highlight the recent work to identify the first important human uric acid secretory transporter, ABCG2, and the identification of a common causal ABCG2 variant, Q141K, for hyperuricemia and gout.

Recent clinical and translational advances in pediatric hypertension

Epidemiological reports describe a child population increase in BP level and an increase in prevalence of hypertension, that is largely, but not entirely, driven by a concurrent increase in childhood obesity. Given current estimates, ≈10% of adolescents have hypertension or prehypertension. In addition to obesity, dietary salt intake and waist circumference, a marker of visceral obesity, are found to be independently associated with the rise in BP among children and adolescents. Dietary salt intake in urban children is well above recommended levels largely because of consumption of processed and fast foods. Childhood exposures, such as stress,52 salt, and fructose, as well as lifestyles, including food sources, sleep patterns, and reductions in physical activity may have a role in obesity-high BP associations. In addition, clinical and translational evidence is mounting that intrauterine exposures alter can effect changes in fetal development that have an enduring effect on cardiovascular and metabolic function later in life. These effects can be detected even in children who are products of a term otherwise normal pregnancy. Hypertension in childhood has been defined statistically (BP ≥ 95th percentile) because of lack of outcome data that links a BP level with heightened risk for future cardiovascular events. Therefore, primary hypertension had been considered a risk factor for later hypertension in adulthood. Intermediate markers of TOD, including cardiac hypertrophy, vascular stiffness, and increases in cIMT, are detectable in adolescents with primary hypertension. Evidence that vascular injury is present in the early phase of hypertension and even in prehypertension warrants consideration on the current definition of pediatric hypertension. With further studies on TOD and other risk factors in addition to high BP, it may be possible to shift from a statistical definition to a definition of childhood hypertension that is evidence based. Preventing or reducing childhood obesity would have substantial benefit in countering the documented increase in BP levels and prevalence of high BP in childhood. Weight control in overweight and obese children, along with dietary changes 53 and increases in physical activity,54 has benefit on BP levels in childhood. Prevention of childhood obesity and BP risk will require multiple levels of intervention, including public health, health policy, and attention to food supply to foster the necessary lifestyle changes to prevent and reduce childhood obesity.