Serum uric acid and ambulatory blood pressure in children with primary hypertension

Trends in serum uric acid levels among Korean children and adolescents between 2016 and 2020: a nationwide study

The aim of this study was to examine trends in serum uric acid (SUA) levels over a recent 5-year period according to age, sex, obesity, and abdominal obesity among Korean children and adolescents. We conducted a serial cross-sectional analysis using nationally representative data from the Korea National Health and Nutritional Examination Survey from 2016 to 2020. The study outcome was trends in SUA levels. SUA trends were analyzed by survey-weighted linear regression analysis considering the survey year as a continuous variable. SUA trends were also analyzed for subgroups based on age, sex, abdominal obesity, or obesity. This study included 3,554 children and adolescents aged 10-18 years. SUA increased significantly over the study period in boys (p for trend = 0.043), but not in girls (p for trend = 0.300). In age-specific analyses, SUA increased significantly in the 10-12 years group (p for trend = 0.029). After adjusting for age, SUA increased significantly in the obese group of both boys (p for trend = 0.026) and girls (p for trend = 0.023), but not in the overweight, normal, or under-weight groups of either sex. After adjusting for age, SUA increased significantly in the abdominal obesity group of boys (p for trend = 0.017) and girls (p for trend = 0.014), but not in the non-abdominal obesity group of either sex.   Conclusion: In the current study, SUA levels significantly increased in both boys and girls with obesity or abdominal obesity. Further studies of the effect of SUA on health outcomes in boys and girls with obesity or abdominal obesity are needed. What is Known: • High serum uric acid (SUA) is a risk factor for various metabolic diseases, including gout, hypertension, and type 2 diabetes. What is New: • SUA levels increased in boys and the 10-12 years group of Korean children and adolescents. • SUA levels increased significantly in Korean children and adolescents with obesity or central obesity.

Uricaemia and associated health determinants in a paediatric population in Mexico

BACKGROUND AND AIM

Uric acid (UA) is a product of the catabolism of purines, and its increase in blood may be related to the development of cardiometabolic diseases. Whether UA is the result or causal determinant of the appearance of risk factors for cardiometabolic disease is not yet known. UA levels among the young student population in San Luis Potosi have increased in recent years, which may be indicative of a serious future public health concern. Therefore, the objective of this study was to evaluate the association of sociodemographic, lifestyle and cardiometabolic determinants with UA levels in children and adolescents in San Luis Potosí.

METHODS AND RESULTS

A total of 730 students (54.1% female and 45.9% male, 6-19 years old) participated in the study. The subjects attended one of five public schools located in San Luis Potosí. Venous blood samples were collected, blood serum was separated by centrifugation, and UA concentrations were measured with an automated analytical platform. UA was associated with most of the independent variables studied. It presented a positive correlation with body mass index (r = 0.363, p < 0.01). Male sex, socioeconomic status, total screen time, exercise, adequate sleep, systolic blood pressure, total cholesterol, and high-density lipoprotein cholesterol explained 23%-39% (p < 0.001) of the variability of plasma concentrations of UA in children and adolescents.

CONCLUSION

Early detection of these determinants will prevent future diseases. Moreover, it will help with the implementation of preventive strategies that could improve the health of this population.

The relationship between anthropometric factors and hyperuricemia in adolescent athletes

PURPOSE

Hyperuricemia has been increasingly prevalent and linked to future cardio-metabolic risks in adolescent population. The study aims to explore the relationship between anthropometric indices and hyperuricemia among adolescent athletes.

METHODS

This was a cross-sectional study of 387 student athletes (218 males and 169 females; mean age, 17.4 ± 1.3 years) in Northern Taiwan in 2013-2015. We exhibited the prevalence of hyperuricemia among this population, and tested the association of serum uric acid levels with different anthropometric parameters in males and females respectively.

RESULTS

A total of 59 (27.1%) male and 37 (21.8%) female adolescent athletes had hyperuricemia. Both in male and female adolescents, several obesity-related anthropometric parameters were significantly higher in hyperuricemia groups than in non-hyperuricemia groups. The odds of having hyperuricemia significantly increased with increasing BMI, BMI z-score, waist circumference and waist-to-height ratio in logistic regression analysis. There was a U-shaped association between uric acid level and body fat percentage (BF%) in both genders. Subjects whose BF% in lowest-body-fat-percentage quintile (quintile 1) and highest-body-fat-percentage quintile (quintile 5) had higher mean serum uric acid level than subjects whose BF% in the middle three quintiles. In both genders, the odds ratio (OR) of having hyperuricemia in subjects whose BF% in quintile 1 remained significantly higher than the OR in the middle three quintiles (the reference) after adjusting for age and BMI z-score.

CONCLUSIONS

In addition to the positive association between obesity and hyperuricemia, there is a U shape association between BF% and prevalence of hyperuricemia among adolescent athletes of both genders.

Elevated serum uric acid is associated with incident hypertension in the health according to various contemporary blood pressure guidelines

BACKGROUND AND AIMS

Elevated serum uric acid (SUA) is associated with hypertension according to its traditional definition. We investigated the association between SUA and incident hypertension according to the European Society of Cardiology (ESC) and American Society of Cardiology (ACC) guidelines.

METHODS AND RESULTS

In this retrospective cohort study, we enrolled 10,537 healthy individuals ≥30 years old who underwent a routine annual health examination with office blood pressure recorded at our hospital in 2016; of the participants, 7349 repeated the exam in 2017. According to the ESC and ACC guidelines, hypertension was defined as office BP ≥ 140/90 mmHg or ≥130/80 mmHg. Hyperuricemia (HUA) was defined as SUA ≥7 mg/dL in men and ≥6 mg/dL in women. The hypertension incidence was 5.8% among 6378 individuals in the ESC cohort and 19% among 4330 individuals in the ACC cohort. Incident hypertension was significantly more common in the hyperuricemic group than in the normouricemic group (ESC: 8.6% vs. 4.7%, P < 0.001; ACC: 25.5% vs. 16.9%, P < 0.001). In the fully adjusted multivariate logistic regression analyses, each increase in SUA was associated with an increase in incident hypertension risk (ESC: adjusted OR: 1.167, 95% CI: 1.061-1.284, P = 0.001; ACC: adjusted OR: 1.125, 95% CI: 1.044-1.213, P = 0.002). The association can be explained by a significant correlation of baseline SUA with the BP in the following year (r = 0.24, P < 0.001 for baseline SUA and SBP in the following year; r = 0.239, P < 0.001 for baseline SUA and DBP in the following year).

CONCLUSION

Elevated SUA was associated with incident hypertension in healthy individuals according to various contemporary BP guidelines (ClinicalTrials.gov: NCT03473951).

CLINICAL TRIALS

ClinicalTrials.gov with the identification number of NCT03473951.

Association of serum uric acid concentration with components of pediatric metabolic syndrome: A systematic review and meta-analysis

Background:

Hyperuricemia is implicated in the pathogenesis of inflammatory diseases and metabolic disorders. Metabolic syndrome (MetS) in childhood is one of the most important causes of different noncommunicable diseases in adulthood. This study aimed to systematically review the association between serum uric acid (UA) concentration and components of pediatric MetS.

Materials and Methods:

In this meta-analysis and systematic review, related articles were gathered by searching English databases including PubMed, Web of Science, Scopus, and Google Scholar. We used the following keywords: uric acid, metabolic syndrome, hypertension, fasting blood sugar (FBS), hyperglycemia; the search was limited to English language and included observational and cohort studies performed among children or adolescents. Pooled relative risks (odds ratio [OR]) and corresponding 95% confidence interval (95% CI) were extracted. A random-effect model was used.

Results:

On the basis of 34 eligible studies, the pooled correlation between UA with metabolic components including FBS (r = 0.24, 95% CI = 0.09–0.40), fasting insulin (r = 0.26, 95% CI = 0.15–0.37), and hyperglycemia (r for triglyceride and UA = 0.23, 95% CI = 0.19–0.38) (r for high-density lipoprotein and UA = −0.28, 95% CI = −0.37 to −0.20) was statistically significant. The association of both diastolic blood pressure (DBP) and systolic blood pressure (SBP) was statistically significant with UA (r for SBP and UA = 0.34, 95% CI = 0.24–0.43; r for DBP and UA = 0.18, 95% CI = 0.11–0.25). The OR between risk of abdominal obesity with UA was statistically significant (OR = 2.62, 95% CI = 1.41–3.84).

Conclusion:

Serum UA concentration is associated with major components of the pediatric MetS. Its measurement and control should be underscored in at-risk children and adolescents.

The association of urinary uric acid excretion with ambulatory blood pressure values in patients with chronic kidney disease

BACKGROUND

To analyze the association between hypertension and urinary uric acid excretion in patients with chronic kidney disease (CKD).

METHODS

We screened 87 patients who had been admitted at the Dept of Nephrology, Huadong hospital between April 2017 to April 2019 who had completed 24-h ambulatory blood pressure monitoring and retained 24-h urine biochemical test specimens, thirty adult patients (age ≤ 65 years) with CKD 1-2 stages were recruited in the study. Pearson's correlation analysis and multiple linear regression analysis were used to study the correlation of urinary uric acid excretion with ambulatory blood pressure values and the association of morning mean diastolic pressure (mMDP), night mean diastolic pressure (nMDP) and CV of dMSP (coefficient of variation of day mean systolic pressure) with fractional excretion of uric acid (FEua) and uric acid clearance rate (Cur). Independent T test was used to compare the differences of blood pressure values in FEua1 (FEua< 6.0%) and FEua2 (FEua≥6.0%) or Cur1 (Cur < 6.2 ml/min/1.73 m2) and Cur2 (Cur ≥ 6.2 ml/min/1.73m2) groups according to the median of FEua or Cur, respectively.

RESULTS

After adjusting for confounding factors, multiple linear regression analysis showed that FEua was positively associated with the mMDP and nMDP, Cur was positively associated with CV of dMSP. Levels of mMDP and nMDP in FEua1 group was lower than that in FEua2 group (both P < 0.05), level of CV of dMSP in Cur2 group were higher than that in Cur1 group (P < 0.01).

CONCLUSIONS

We demonstrated that there is a positive correlation of FEua with morning and night mean diastolic pressure separately and Cur is positively related to CV of dMSP in CKD population. Monitoring the trend of urinary uric acid, may have a role in the early detection for hypertension or relative risks in the population of CKD.

Influence of muscle mass on the serum uric acid levels in children and adolescents

BACKGROUND AND AIM

Uric acid (UA) is an end-product of purine catabolism and its increase in blood is a risk factor for several diseases. UA levels in men are usually higher than in women. This difference is partially due to sex hormones. We sought to investigate the onset of sexual difference in UA levels during pubertal development and the determinants of UA levels in children and adolescents.

METHODS AND RESULTS

The muscle mass and fat mass were measured by multi-frequency bioelectrical impedance in a cross-sectional study involving 823 children and adolescents (both sexes; 6-18 years). Serum UA was determined using a commercially available kit. UA levels started to become higher in boys (5.0 ± 1.0 mg/dL) than in girls (4.1 ± 0.9 mg/dL) around 13 years. Boys in the highest quartile of muscle mass presented higher UA levels (5.2 ± 0.7 mg/dL) when compared with the third (4.2 ± 0.7 mg/dL), second (3.7 ± 0.9 mg/dL) and first (3.4 ± 0.9 mg/dL). Similarly, girls in the highest quartile of muscle mass presented higher UA levels (4.2 ± 0.7 mg/dL) when compared with the second (3.8 ± 0.9 mg/dL) and first (3.3 ± 0.9 mg/dL). Muscle mass explained 43.0% and 7.7% of the variability of UA in boys and girls, respectively.

CONCLUSION

Sexual differences in serum UA levels begin at puberty and partially result from a direct influence of muscle mass.

Association between pre-and postnatal growth and longitudinal trends in serum uric acid levels and blood pressure in children aged 3 to 7 years

Background

Uric acid has been identified as an important factor in the development of hypertension. If low birth weight (LBW) combined with catch-up growth (CUG) is associated with continuously elevated serum uric acid levels (SUA) level trajectories, LBW children who experience CUG may have an increased risk of hypertension later in life. Therefore, this cohort study analyzed longitudinal trends in SUA levels and changes in blood pressure in relation to pre- and postnatal growth over an extended follow-up period.

Methods

This prospective cohort study of 364 children from the Ewha Birth and Growth Cohort assessed the effects of pre- and postnatal growth status on SUA at 3, 5, and 7 years of age using a linear mixed model and the change in blood pressure over the 7-year follow-up period using a generalized linear model (analysis of covariance). CUG was defined as a change in weight (between birth and age 3) with a z-score > 0.67 for LBW subjects. The multivariate model considered sex, gestational age, and uric acid, height, and weight at 3 years of age.

Results

Children with LBW and CUG had higher SUA for the first 7 years of life compared to the normal birth weight group. This trend was particularly evident when comparing LBW children at term to children with normal birth weight. Within the group with LBW at term, children with greater CUG had higher SUA than children with normal birth weight, and this difference increased with age. Changes in the systolic blood pressure between 3 and 7 years of age were higher by 7.9 mmHg in children who experienced LBW and CUG compared with those who had a normal birth weight after adjusting for sex, gestational age, and height, weight, and uric acid at 3 years of age (p-value = 0.08).

Conclusions

The uric acid levels and changes in systolic blood pressure were consistently higher among LBW children who experienced CUG compared with NBW children for the first 7 years of life. LBW children who experienced greater weight gain from birth to age 3 had even higher uric acid levels compared with NBW children.

Hyperuricemia in Children and Adolescents: Present Knowledge and Future Directions

Recent evidence suggests that hyperuricemia is an important condition in children and adolescents, particularly in association with noncommunicable diseases. This review aims to summarize our current understanding of this condition in pediatric patients. An analysis of serum uric acid reference values in a healthy population indicates that they increase gradually with age until adolescence, with differences between the sexes arising at about 12 years of age. This information should be taken into consideration when defining hyperuricemia in studies. Gout is extremely rare in children and adolescents, and most patients with gout have an underlying disease. The major causes of hyperuricemia are chronic conditions, including Down syndrome, metabolic or genetic disease, and congenital heart disease, and acute conditions, including gastroenteritis, bronchial asthma (hypoxia), malignant disorders, and drug side effects. The mechanisms underlying the associations between these diseases and hyperuricemia are discussed, together with recent genetic information. Obesity is a major cause of hyperuricemia in otherwise healthy children and adolescents. Obesity is often accompanied by metabolic syndrome; hyperuricemia in obese children and adolescents is associated with the components of metabolic syndrome and noncommunicable diseases, including hypertension, insulin resistance, dyslipidemia, and chronic kidney disease. Finally, strategies for the treatment of hyperuricemia, including lifestyle intervention and drug administration, are presented.

Novel Insights in the Metabolic Syndrome in Childhood and Adolescence

Metabolic syndrome (MetS) is recognized as an escalating major health risk in adults as well as in children and adolescents. Its prevalence ranges from 6 to 39% depending on the applied definition criteria. To date, there is no consensus on a MetS definition for children and adolescents. However, most authors agree on essential components such as glucose intolerance, central obesity, hypertension, and dyslipidemia; each representing a risk for cardiovascular disease. Recently, associations between MetS and non-alcoholic fatty liver disease, hyperuricemia, and sleep disturbances have emerged. Biomarkers like adipocytokines are a subject of current research as they are implicated in the pathogenesis of the MetS. Epigenetics and gestational programming, especially the role of microRNA, comprise a novel, rapidly developing and promising research focus on the topic of MetS. MicroRNAs are increasingly valued for potential roles in the diagnosis, stratification, and therapeutics of MetS. Early detection of risk factors, screening for metabolic disturbances, and the identification of new therapies are major aims to reduce morbidity and mortality related to MetS. Dietary modification and physical activity are currently the only adopted treatment approaches. Pharmacological therapies and bariatric surgery are still contradictory and, therefore, are only recommended in selected high-risk cases.

Effects of serum uric acid on blood-pressure lowering treatment

If hyperuricemia is an independent risk factor in blood-pressure control, urate-lowering therapy should be used to reduce cardiovascular risk. It may also act as a prognostic marker of other abnormalities. This review presents current evidence on the relationship between hyperuricemia and hypertension.

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.

Household fear of deportation in Mexican-origin families: Relation to body mass index percentiles and salivary uric acid

OBJECTIVE

Fear of deportation (FOD) is a prevalent concern among mixed-status families. Yet, our understanding of how FOD shapes human health and development is in its infancy. To begin to address this knowledge gap, we examined the relationship between household FOD, body mass index (BMI) percentiles and salivary uric acid (sUA), a biomarker related to oxidative stress/hypertension/metabolic syndrome, among 111 individuals living in Mexican-origin families.

METHODS

Participants were 65 children (2 months-17 years, 49% female) and 46 adults (20-58 years, 71% female) living in 30 Mexican-origin families with at least one immigrant parent in Phoenix, AZ. We recruited families using cluster probability sampling of 30 randomly selected census tracts with a high proportion of Hispanic/Latino immigrants. The head of household completed a survey containing demographic, FOD, and psychosocial measures. All family members provided saliva (later assayed for sUA) and anthropometric measures. Relationships between household FOD, BMI percentile, and sUA levels were estimated using multilevel models.

RESULTS

Higher levels of household FOD were associated with lower BMI percentiles and lower sUA levels between families, after controlling for social support and socioeconomic proxies.

CONCLUSION

Key features of the social ecology in which mixed-status families are embedded are associated with individual differences in biological processes linked to increased risk for chronic disease.

The Role of Uric Acid in Hypertension of Adolescents, Prehypertension and Salt Sensitivity of Blood Pressure

Uric acid is the end product of purine metabolism. Metabolic disorders of uric acid are associated with many disease states. Substantial evidence suggests the possible role of uric acid as a mediator of high blood pressure. Elevated uric acid is closely associated with new onset essential hypertension in adolescents and prehypertension; and urate-lowering agents can significantly improve these early stages of hypertension. Uric acid also influences salt sensitivity of blood pressure through two phases. Local renin-angiotensin-aldosterone system activation initiates renal damage, arteriolopathy, and endothelium dysfunction, which is followed by the dysregulation of sodium homeostasis, thereby leading to increased salt sensitivity. In this review we summarize the available evidence to contribute to a better understanding of the casual relationship between uric acid and early or intermediate stages of hypertension. We hope our review can contribute to the prevention of hypertension or provide new insights into a treatment that would slow the progression of hypertension.

Association between body mass index and salivary uric acid among Mexican-origin infants, youth and adults: Gender and developmental differences

Uric acid (UA) is the end product of the metabolic breakdown of purine nucleotides. Recent studies have measured UA in saliva in relation to obesity and chronic disease risk. Given the increasing prevalence of metabolic syndrome among Latino youth, we examined gender and age differences in salivary uric acid (sUA) and weight in a sample of Mexican-origin children (n = 65, 2 months to 18 years, 49% female) and adults (n = 46, 19-58 years, 72% female). We measured weight, height, waist, and hip circumference and collected saliva samples (later assayed for sUA). Structural equation models estimated the relationship between age, developmental stage, and weight outcomes in relation to sUA levels between genders, while controlling for race. Results demonstrate that increased sUA levels were related to higher BMI percentiles in females of all ages (β = 0.43, p < .001). There were significant differences in sUA levels between developmental stages for girls, with female toddlers having the highest sUA levels (β = .28, p = .02). In an interaction between BMI z-score and gender between youth and adults, BMI has a larger effect on increasing sUA levels among younger girls (β = 0.27, p < .03) and adult women (β = 0.33, p = .02). Levels of sUA may be gender-specific in relation to BMI and developmental stage.

Novelty in hypertension in children and adolescents: focus on hypertension during the first year of life, use and interpretation of ambulatory blood pressure monitoring, role of physical activity in prevention and treatment, simple carbohydrates and uric acid as risk factors

The present article intends to provide an update of the article "Focus on prevention, diagnosis and treatment of hypertension in children and adolescents" published in 2013 (Spagnolo et al., Ital J Pediatr 39:20, 2013) in this journal. This revision is justified by the fact that during the last years there have been several new scientific contributions to the problem of hypertension in pediatric age and during adolescence. Nevertheless, for what regards some aspects of the previous article, the newly acquired information did not require substantial changes to what was already published, both from a cultural and from a clinical point of view. We felt, however, the necessity to rewrite and/or to extend other parts in the light of the most recent scientific publications. More specifically, we updated and extended the chapters on the diagnosis and management of hypertension in newborns and unweaned babies, on the use and interpretation of ambulatory blood pressure monitoring, and on the usefulness of and indications for physical activity. Furthermore, we added an entirely new section on the role that simple carbohydrates (fructose in particular) and uric acid may play in the pathogenesis of hypertension in pediatric age.

Hyperuricemia and Progression of CKD in Children and Adolescents: The Chronic Kidney Disease in Children (CKiD) Cohort Study

BACKGROUND

Hyperuricemia is associated with essential hypertension in children. No previous studies have evaluated the effect of hyperuricemia on progression of chronic kidney disease (CKD) in children.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

Children and adolescents (n=678 cross-sectional; n=627 longitudinal) with a median age of 12.3 (IQR, 8.6-15.6) years enrolled at 52 North American sites of the CKiD (CKD in Children) Study.

PREDICTOR

Serum uric acid level (<5.5, 5.5-7.5, and >7.5mg/dL).

OUTCOMES

Composite end point of either >30% decline in glomerular filtration rate (GFR) or initiation of renal replacement therapy.

MEASUREMENTS

Age, sex, race, blood pressure status, GFR, CKD cause, urine protein-creatinine ratio (<0.5, 0.5-<2.0, and ≥2.0mg/mg), age- and sex-specific body mass index > 95th percentile, use of diuretics, and serum uric acid level.

RESULTS

Older age, male sex, lower GFR, and body mass index > 95th percentile were associated with higher uric acid levels. 162, 294, and 171 participants had initial uric acid levels < 5.5, 5.5 to 7.5, or >7.5 mg/dL, respectively. We observed 225 instances of the composite end point over 5 years. In a multivariable parametric time-to-event analysis, compared with participants with initial uric acid levels < 5.5mg/dL, those with uric acid levels of 5.5 to 7.5 or >7.5mg/dL had 17% shorter (relative time, 0.83; 95% CI, 0.62-1.11) or 38% shorter (relative time, 0.62; 95% CI, 0.45-0.85) times to event, respectively. Hypertension, lower GFR, glomerular CKD cause, and elevated urine protein-creatinine ratio were also associated with faster times to the composite end point.

LIMITATIONS

The study lacked sufficient data to examine how use of specific medications might influence serum uric acid levels and CKD progression.

CONCLUSIONS

Hyperuricemia is a previously undescribed independent risk factor for faster progression of CKD in children and adolescents. It is possible that treatment of children and adolescents with CKD with urate-lowering therapy could slow disease progression.

Preterm Birth Is Associated with Higher Uric Acid Levels in Adolescents

OBJECTIVE

To compare serum uric acid levels in adolescents born prematurely and adolescents born at term and to assess the correlation between serum uric acid and blood pressure (BP) in those born prematurely.

STUDY DESIGN

In this observational cohort study, 124 adolescents born prematurely and 44 adolescents born at term were studied at 14 years of age. Multivariate analyses were used to describe the relationship of premature birth to serum uric acid while adjusting for confounding variables. Pearson correlation was used to describe the relationship between uric acid and systolic BP among those born prematurely.

RESULTS

Adjusting for race, sex, maternal hypertension, and fetal growth, we found that preterm adolescents had greater serum uric acid levels than adolescents born at term (adjusted mean difference 0.46, 95% CI 0.10-0.81 mg/dL; 27.4, 6-48.2 μmol/L; P = .012). Among those born prematurely, uric acid was positively correlated with systolic BP (Pearson correlation coefficient: 0.29, 0.12-0.44; P = .0013).

CONCLUSIONS

Serum uric acid levels are greater in adolescents born prematurely than in those born at term, and this difference could contribute to greater BP among individuals born prematurely.

Serum uric acid and cardiovascular risk among Portuguese adolescents

PURPOSE

The aim of the study was to investigate the association between serum uric acid (SUA) and cardiovascular risk classes (CRCs) in adolescents using a cluster-based approach.

METHODS

A cross-sectional evaluation was carried out in the 2007-2008 school year, including adolescents born in 1990 and enrolled in the schools of Porto, Portugal. The analysis included 1,286 adolescents. To identify CRC, a normal mixture model was performed including several biological cardiovascular risk factors. A multinomial logistic regression model was applied to explore the association between SUA and each CRC.

RESULTS

Three classes were extracted using model-based cluster analysis (low, medium, and high CRC). The high CRC accounted for the smallest proportion of participants (5.6%) and represented the adolescents with higher waist circumference, systolic and diastolic blood pressures, total cholesterol, triglycerides, and insulin levels. Adolescents at increased risk of cardiovascular disease had significantly higher mean concentrations of SUA compared with adolescents at low cardiovascular risk (55.0 vs. 51.5 mg/L in males and 41.9 vs. 37.6 mg/L in females). After adjustment and considering low CRC as reference, SUA was positively associated with high CRC in both sexes (odds ratio, 1.04; 95% confidence interval, 1.00-1.07 in males; and odds ratio, 1.04; 95% confidence interval, 1.01-1.07 in females).

CONCLUSIONS

Among 17-year-old adolescents, SUA increases were positively associated with higher CRC.

Serum uric acid concentrations and SLC2A9 genetic variation in Hispanic children: the Viva La Familia Study

BACKGROUND

Elevated concentrations of serum uric acid are associated with increased risk of gout and renal and cardiovascular diseases. Genetic studies in adults have consistently identified associations of solute carrier family 2, member 9 (SLC2A9), polymorphisms with variation in serum uric acid. However, it is not known whether the association of serum uric acid with SLC2A9 polymorphisms manifests in children.

OBJECTIVE

The aim was to investigate whether variation in serum uric acid is under genetic influence and whether the association with SLC2A9 polymorphisms generalizes to Hispanic children of the Viva La Familia Study.

DESIGN

We conducted a genomewide association study with 1.1 million genetic markers in 815 children.

RESULTS

We found serum uric acid to be significantly heritable [h(2) ± SD = 0.45 ± 0.08, P = 5.8 × 10(-11)] and associated with SLC2A9 variants (P values between 10(-16) and 10(-7)). Several of the significantly associated polymorphisms were previously identified in studies in adults. We also found positive genetic correlations between serum uric acid and BMI z score (ρG = 0.45, P = 0.002), percentage of body fat (ρG = 0.28, P = 0.04), fat mass (ρG = 0.34, P = 0.02), waist circumference (ρG = 0.42, P = 0.003), and waist-to-height ratio (ρG = 0.46, P = 0.001).

CONCLUSIONS

Our results show that variation in serum uric acid in Hispanic children is under considerable genetic influence and is associated with obesity-related phenotypes. As in adults, genetic variation in SLC2A9 is associated with serum uric acid concentrations, an important biomarker of renal and cardiovascular disease risk, in Hispanic children.

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.

Survival impact of serum uric acid levels in children and adolescents

Evidence is limited on the association between hyperuricaemia and mortality in children and adolescents. This study was to investigate this association in the paediatric population. The study included children and adolescents who had undergone serum uric acid (SUA) measurement at the Chang Gung Memorial Hospital between 1997 and 2008. The survival status and cause of death of the included were ascertained by examining the National Death Registry of Taiwan. Hyperuricaemia was defined as a SUA level greater than 7.0 mg/dL. We included 13,241 patients (male, n = 7,454; female, n = 5,787) of mean age 14.3 ± 4.9 years. During the 82,800 person-years of follow-up, 455 deaths were identified, which corresponded to a crude mortality rate of 5.50 deaths per 1,000 person-years. Compared with individuals with a SUA <6.0 mg/dL, those with a SUA of 6.0-8.9, 9.0-11.9 and ≥12 mg/dL had an age- and sex-adjusted HR (95% CI) of 1.02 (0.82-1.26), 1.48 (1.08-2.02) and 4.73 (2.67-8.37). After adjustment for age, sex and history of diabetes mellitus and hypertension, hyperuricaemia was found to be associated with a HR (95% CI) of 1.38 (1.13-1.69; p < 0.001) for all-cause mortality. Hyperuricaemia was associated with an increased risk of mortality due to cardiovascular diseases (HR, 5.0; 95% CI 1.79-13.94; p = 0.001) and kidney diseases (11.71; 3.13-43.78; p < 0.001). Paediatric patients with hyperuricaemia were at increased risk of mortality, especially due to kidney and cardiovascular diseases.

Ambulatory blood pressure monitoring in children: imperfect yet essential

There has been increasing emphasis on hypertension and early cardiovascular disease in the pediatric age group over the past decade as a result of various factors, including the obesity epidemic and publication of new clinical guidelines. A key component of identifying children and adolescents with definite or potential hypertension is proper blood pressure (BP) measurement. While ambulatory blood pressure monitoring (ABPM) offers the potential for improved detection of youths at increased cardiovascular risk, it has not been widely adopted. This commentary highlights the crucial role of ABPM in the context of current trends, while at the same time identifying the current barriers to more widespread application of this technique. Chief among these is the lack of a robust, universally applicable database of pediatric ABPM normative values. Even in the absence of ideal normative data, ABPM can and should be widely applied, and a potential algorithm for such an approach is presented.

Impact of different adiposity measures on the relation between serum uric acid and blood pressure in young adults

Serum uric acid (SUA) concentration is independently associated with blood pressure (BP) in adults. We examined this association in young adults at an age where anti-hypertension treatment, other potential confounding factors and co-morbidity are unlikely to occur. We assessed BP, anthropometric variables including weight, height, waist circumference (WC), body fat percent (using bioimpedance), lifestyle behaviors, SUA and blood lipids in 549 participants aged 19-20 years from a population-based cohort study (Seychelles Child Development Study). Mean (s.d.) SUA was higher in males than females, 0.33 (0.08) and 0.24 (0.07) mmol l(-1), respectively. Body mass index (BMI) was higher in females than males but BP was markedly higher in males than in females. SUA was associated with both systolic and diastolic BP. However, the magnitude of the linear regression coefficients relating BP and SUA decreased by up to 50% upon adjustment for BMI, WC or body fat percent. The association between SUA and BP was not altered upon further adjustment for alcohol intake, smoking, triglycerides or renal function. In fully adjusted models, SUA remained associated with BP (P<0.05) in females. In conclusion, adiposity substantially decreased the association between SUA and BP in young adults, and BP was independently associated with SUA in females. These findings suggest a role of adiposity in the link between hyperuricemia and hypertension.

Current and future therapeutic options for the management of gout

The incidence of gout and the clinical manifestation of hyperuricemia continue to rise. In addition to painful acute attacks, chronic gout can lead to the development of crystal arthropathy, tophi, and renal lithiasis, coincidental with declines in quality of life. As a greater appreciation for the associations between hyperuricemia, gout, and certain comorbidities, such as renal impairment and cardiovascular diseases, grows, so does the search for new therapeutic options to both alleviate the painful symptoms of acute gout attacks and reduce the underlying hyperuricemia. This manuscript reviews the pathophysiology of hyperuricemia and gout, and associated comorbidities, and then discusses traditional therapeutic options, newly available agents, and future targets for pharmacologic management.

Gender-specific association of serum uric acid with metabolic syndrome and its components in juvenile obesity

BACKGROUND

Hyperuricemia has been implicated in the pathogenesis of obesity and related metabolic abnormalities. Studies on the association between serum uric acid (sUA) and metabolic syndrome (MetS) in juvenile obesity are scant. The effect of gender has not been evaluated.

METHODS

sUA (uricase method), anthropometric and biochemical indices were measured in gender-stratified children/adolescents consisting of 113 overweight/obese and 71 lean individuals.

RESULTS

In males, sUA was significantly elevated in overweight as well as obese patients. sUA was strongly associated with obesity indices and reflected sexual development, decreases in high density lipoprotein-cholesterol, and moderately, the number of MetS components. Waist circumference (WC) and Tanner stage explained 40% of sUA variability. Controlling for body mass index (BMI) and other MetS components, sUA was associated with abdominal obesity, explaining 30% of variability in WC. In females, sUA was significantly increased in obesity, high blood pressure (BP), and MetS and corresponded with the number of MetS components, indices of glucose metabolism, triglycerides (TG), and the atherogenecity index. Insulin-resistance (IR) (homeostasis model assessment; HOMA) and high BP explained 29% of sUA variability, whereas sUA, while controlling for BMI, age, and other MetS components, was associated with hypertriglyceridemia, hyperglycemia, high BP, and abdominal obesity. IR mediated the associations with high TG and glucose.

CONCLUSIONS

The association between sUA and MetS components in juvenile obesity is gender-specific, with females being related more closely and to more metabolic abnormalities. It may explain why, despite its lower concentrations, sUA is an independent predictor of mortality from all causes and from vascular diseases exclusively in females. Our findings may help in identifying metabolic abnormalities which may possibly be targeted by reducing sUA in males and females.

High-sensitivity C-reactive protein and mean platelet volume in paediatric hypertension

The purpose of the study was to investigate serum uric acid (SUA), high-sensitivity C-reactive protein (hs-CRP) and mean platelet volume (MPV) in pre-hypertensive (PH) and hypertensive (HT) children and adolescents. The study group consisted of 80 patients aged 10-19 years subdivided into PH and HT groups according to mean daytime or night-time systolic or diastolic blood pressure (BP) levels (> 90th percentile, but < 95th percentile and > or = 95th percentile, respectively). The control group (C) contained 25 normotensive subjects. Serum hs-CRP level was determined by a nephelometric method (Behring); platelets (PLTs) were counted, and MPV was assessed by a Coulter Analyzer MAXM. SUA was measured with an Hitachi instrument. The median SUA and hs-CRP levels in PH and HT subjects were significantly higher than those of the controls (P < 0.01) and were higher in the HT group than in the PH group (P < 0.05). An increase in SUA above 5.5 mg/dl was associated with an increase in hs-CRP [odds ratio (OR) 4.8; confidence interval (CI) 1.3-17.4; P < 0.01]. MPV values in the PH group did not differ from those of the controls (P > 0.05), but it was significantly higher in HT patients (P < 0.01). Serum hs-CRP and MPV concentrations were positively correlated with all BP measurements except night-time diastolic blood pressure (DBP). We demonstrated that, in HT children and adolescents, increased SUA with a parallel increase in hs-CRP and PLTs with MPV is observed. Although large, multicentre, prospective studies are needed to confirm this observation, hyperuricaemia seems to be associated with an increase in hs-CRP in PH and HT patients.

Association between serum uric acid levels and cardiometabolic risk factors among Japanese junior high school students

BACKGROUND

The present study was designed to examine whether serum uric acid (SUA) levels were associated with cardiometabolic risk factors and to determine optimal cut-offs for SUA to identify multiple risk factors among Japanese junior high school students.

METHODS AND RESULTS

A total of 958 students (518 boys and 440 girls, aged 12.1-15.0 years) who were enrolled between April 2005 and June 2008 were divided into 4 groups according to SUA quartiles. Compared with the lowest quartile of SUA, prevalence of abdominal obesity, hypertension, and dyslipidemia was significantly increased in the highest quartile in boys and that of abdominal obesity was increased in the highest quartile in girls. The adjusted odds ratios (95% confidence interval) of the highest quartile of SUA for 2 or more cardiometabolic risk factors were 2.59 (1.16-5.79) for boys and 1.54 (0.43-5.56) for girls. Receiver operating characteristic curve analysis demonstrated that the most appropriate cut-offs for SUA to identify multiple cardiometabolic risk factors were 6.4 mg/dl for boys and 4.9 mg/dl for girls.

CONCLUSIONS

SUA was strongly associated with the prevalence of cardiometabolic risk factors among male Japanese junior high school students. The present study may provide insights into the role of SUA in the school screening system for the development of educational programs on prevention of lifestyle-related diseases among school children.

Hypertension in children: new trends and challenges

Childhood HTN (hypertension) has become a widely investigated topic within the last decade due to its increasing prevalence. In the present review, we examine new developments and trends that have significantly contributed to aetiology, diagnosis, evaluation and management of childhood HTN. Many recent reports document an increasing prevalence of HTN, mainly essential HTN, in children worldwide. This is probably related to the increase of childhood obesity, although obesity is not the only factor. Evidence has been accumulating to suggest a rather complex interplay between obesity, uric acid level, dietary sodium intake, inflammation, inheritance and other factors, which lead to increased risk of developing HTN in childhood and adulthood. The detection and monitoring of HTN has significantly improved with the use of ABPM (ambulatory blood pressure monitoring), which allows not only for a more accurate classification and staging of HTN, but also for the calculation of more sophisticated parameters such as the AASI (ambulatory arterial stiffness index). Measurement of arterial stiffness enables assessment of arterial dysfunction, which may precede structural vascular changes evaluated by carotid intima media thickness. Sustained HTN eventually leads to end-organ damage [LVH (left ventricular hypertrophy), central nervous system], which in turn increases the risk of cardiovascular morbidity and mortality. New developments in childhood HTN, as outlined in the present review, will hopefully contribute to better screening and management of HTN in children.