Effect of Serum Urate Lowering With Allopurinol on Blood Pressure in Young Adults: A Randomized, Controlled, Crossover Trial.

OBJECTIVE: To determine whether serum urate reduction with allopurinol lowers blood pressure (BP) in young adults and the mechanisms mediating this hypothesized effect. METHODS: We conducted a single-center, randomized, double-blind, crossover clinical trial. Adults ages 18-40 years with baseline systolic BP ≥120 and <160 mm Hg or diastolic BP ≥80 and <100 mm Hg, and serum urate ≥5.0 mg/dl for men or ≥4.0 mg/dl for women were enrolled. Main exclusion criteria included chronic kidney disease, gout, or past use of urate-lowering therapies. Participants received oral allopurinol (300 mg daily) or placebo for 1 month followed by a 2-4 week washout and then were crossed over. Study outcome measures were change in systolic BP from baseline, endothelial function estimated as flow-mediated dilation (FMD), and high-sensitivity C-reactive protein (hsCRP) levels. Adverse events were assessed. RESULTS: Ninety-nine participants were randomized, and 82 completed all visits. The mean ± SD age was 28.0 ± 7.0 years, 62.6% were men, and 40.4% were African American. In the primary intent-to-treat analysis, systolic BP did not change during the allopurinol treatment phase (mean ± SEM -1.39 ± 1.16 mm Hg) or placebo treatment phase (-1.06 ± 1.08 mm Hg). FMD increased during allopurinol treatment periods compared to placebo treatment periods (mean ± SEM 2.5 ± 0.55% versus -0.1 ± 0.42%; P < 0.001). There were no changes in hsCRP level and no serious adverse events. CONCLUSION: Our findings indicate that urate-lowering therapy with allopurinol does not lower systolic BP or hsCRP level in young adults when compared with placebo, despite improvements in FMD. These findings do not support urate lowering as a treatment for hypertension in young adults.

CYP3A5 genotype affects time to therapeutic tacrolimus level in pediatric kidney transplant recipients.

BACKGROUND: Optimal management of immunosuppression in kidney transplantation requires a delicate balance of efficacy and toxicity. Tacrolimus (TAC) dose requirements are significantly impacted by genetic variation in CYP3A5 polymorphisms, however the impact that genotype has on clinical outcomes in the pediatric kidney transplant population remains unclear. METHODS: We evaluated a retrospective cohort of 98 pediatric kidney transplant recipients. The primary exposure was CYP3A5 genotype, which classified each recipient into the expresser (at least one CYP3A5*1 allele) or non-expresser group (only CYP3A5*3 alleles). The primary outcome was time to achieve a steady therapeutic TAC concentration. Secondary outcomes include incidence of early allograft rejection and calcineurin inhibitor (CNI) nephrotoxicity during the first year post-transplant. RESULTS: The study cohort included 55 (56%) expressers and 43 (44%) non-expressers of the CYP3A5*1 allele. Expressers had a significantly longer time to achieve a steady therapeutic TAC concentration than non-expressers (log rank, P = 0.03). Expressers had a trend for higher incidence of early allograft rejection (29.1% vs 16.3%, log rank, P = 0.16). Early biopsy-proven CNI nephrotoxicity was seen in 60% of recipients, with no differences in the rate between expressers and non-expressers. CONCLUSIONS: Pediatric kidney transplant recipients with the CYP3A5*1 allele (expressers) take a longer time to achieve therapeutic TAC levels than those with the CYP3A5*3 allele (non-expressers). However, we observed no significant differences in acute rejection or CNI nephrotoxicity based on CYP3A5 genotype. Thus CYP3A5 genotype was not observed to have an immediate impact on early transplant outcomes.

Hyperfiltration during early childhood precedes albuminuria in pediatric sickle cell nephropathy.

BACKGROUND: In patients with diabetes mellitus, hyperfiltration precedes the development of albuminuria. Pediatric sickle cell anemia (SCA) patients have a high prevalence of hyperfiltration and albuminuria during early childhood and adolescence. We tested the hypothesis that hyperfiltration precedes the development of albuminuria in a longitudinal pediatric SCA cohort. METHODS: We identified 91 participants with HbSS or SB0 thalassemia 5-21 years of age enrolled in a longitudinal sickle cell nephropathy cohort study who had a cystatin C measured during early childhood (4-10 years of age). Early hyperfiltration was defined as a mean eGFR >180 mL/min/1.73m2 using cystatin C obtained from 4 to 10 years of age. Persistent albuminuria was defined as an albumin to creatinine ratio > 30 mg/g on two of three untimed urine specimens. Time to event analysis estimated survival curves for participants with and without hyperfiltration using Kaplan-Meier curves and used logrank test for categorical variables to assess the association with time to development of the first episode persistent albuminuria. RESULTS: Persistent albuminuria occurred more often and at an earlier age in participants with early hyperfiltration compared to those without early hyperfiltration (log-rank, P = .004). Participants who developed albuminuria have a significant increase in their eGFR during childhood (P = .003) as compared to participants who have not yet progressed to albuminuria (P = .26). For every 1 g/dL increase in hemoglobin, the hazard ratio for developing persistent proteinuria decreased by 0.56 (95% CI: 0.3, 1.06, P = .07). CONCLUSION: Hyperfiltration precedes the development of persistent proteinuria in pediatric SCA patients. Intervention strategies should target lowering eGFR during early childhood.

Subclinical inflammation phenotypes and long-term outcomes after pediatric kidney transplantation.

The implementation of surveillance biopsies in pediatric kidney transplantation remains controversial. Surveillance biopsies detect subclinical injury prior to clinical dysfunction, which could allow for early interventions that prolong allograft survival. We conducted a single-center retrospective cohort study of 120 consecutive pediatric kidney recipients, of whom 103 had surveillance biopsies ≤6 months posttransplant. We tested the hypothesis that subclinical inflammation (borderline or T cell-mediated rejection without clinical dysfunction) is associated with a 5-year composite endpoint of acute rejection and allograft failure. Overall, 36% of subjects had subclinical inflammation, which was associated with increased hazard for the composite endpoint (adjusted hazard ratio 2.89 [1.27, 6.57]; P < .01). Subjects with treated vs untreated subclinical borderline rejection had a lower incidence of the composite endpoint (41% vs 67%; P < .001). Subclinical vascular injury (subclinical inflammation with Banff arteritis score > 0) had a 78% incidence of the composite endpoint vs 11% in subjects with no major surveillance abnormalities (P < .001). In summary, we showed that subclinical inflammation phenotypes were prevalent in pediatric kidney recipients without clinical dysfunction and were associated with increased acute rejection and allograft failure. Once prospectively validated, our data would support implementation of surveillance biopsies as standard of care in pediatric kidney transplantation.

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.

Evaluating risk factors for chronic kidney disease in pediatric patients with sickle cell anemia.

BACKGROUND: Patients with sickle cell anemia (SCA) have an increased prevalence of nephropathy and mortality from chronic kidney disease (CKD). METHODS: We evaluated the association of hyperuricemia and nocturnal hypertension with lower estimated glomerular filtration rate (eGFR) using cystatin-C in patients aged 10-21 years with the HbSS or HbSB0 form of the disease during a non-acute clinic visit. eGFR and uric acid measurements were obtained in 83 and 81 participants, respectively, and 24-h ambulatory blood pressure monitoring (ABPM) was performed in 44 participants. Annual testing included vital signs, complete blood count, comprehensive metabolic panel, medications, urine microalbumin/creatinine, and lactate dehydrogenase measurements. Hyperuricemia was defined as a uric acid level of ≥5.5 mg/dL. Nocturnal hypertension was defined as >25% of nocturnal readings at >95th percentile according to norms established by the American Heart Association Statement on ABPM in children and adolescents. RESULTS: The mean eGFR was statistically significantly lower in patients with hyperuricemia than in those with normal uric acid levels (143 vs. 161 mL/min/1.73 m2, respectively). Of the 44 participants for whom ABPM data were available, 14 (32%) had systolic nocturnal hypertension and 12 (27%) had diastolic nocturnal hypertension. The mean eGFR was statistically significantly lower in participants with nocturnal systolic and diastolic hypertension than in those with normal nocturnal blood pressure. In a regression model, nocturnal hypertension and hyperuricemia were associated with a lower eGFR. CONCLUSIONS: Two risk factors for CKD, i.e., nocturnal hypertension and hyperuricemia, were associated with lower eGFR in older children and adolescent patients with SCA. Long-term studies on their association with progression to CKD in this population are warranted. KEY POINT: Nocturnal hypertension and hyperuricemia are established risk factors for nephropathy in other diseases and may play a role in SCA nephropathy.

Added Sugars and Cardiovascular Disease Risk in Children: A Scientific Statement From the American Heart Association.

BACKGROUND: Poor lifestyle behaviors are leading causes of preventable diseases globally. Added sugars contribute to a diet that is energy dense but nutrient poor and increase risk of developing obesity, cardiovascular disease, hypertension, obesity-related cancers, and dental caries. METHODS AND RESULTS: For this American Heart Association scientific statement, the writing group reviewed and graded the current scientific evidence for studies examining the cardiovascular health effects of added sugars on children. The available literature was subdivided into 5 broad subareas: effects on blood pressure, lipids, insulin resistance and diabetes mellitus, nonalcoholic fatty liver disease, and obesity. CONCLUSIONS: Associations between added sugars and increased cardiovascular disease risk factors among US children are present at levels far below current consumption levels. Strong evidence supports the association of added sugars with increased cardiovascular disease risk in children through increased energy intake, increased adiposity, and dyslipidemia. The committee found that it is reasonable to recommend that children consume ≤25 g (100 cal or ≈6 teaspoons) of added sugars per day and to avoid added sugars for children <2 years of age. Although added sugars most likely can be safely consumed in low amounts as part of a healthy diet, few children achieve such levels, making this an important public health target.

The effects of urate lowering therapy on inflammation, endothelial function, and blood pressure (SURPHER) study design and rationale.

BACKGROUND: The association between hyperuricemia and hypertension is controversial. Animal models, epidemiological data, and small clinical trials have favored a causative role for hyperuricemia in hypertension but more studies are necessary to elucidate putative mechanisms, population susceptibility, and potential for urate-lowering therapies (ULT) to decrease blood pressure (BP). PURPOSE: To describe the background and design of the Serum Urate Reduction to Prevent Hypertension (SURPHER) study. METHODS: SURPHER is a single center, double-blinded, crossover trial in which participants are randomly assigned to allopurinol (300mg) or placebo. Enrollment focused on adults 18-40years old with baseline systolic blood pressure≥120 and <160mmHg or diastolic blood pressure≥80 and <100mmHg, and serum urate ≥5.0mg/dL or ≥4.0mg/dL for men or women, respectively. SURPHER recruitment targets participants without chronic kidney disease (estimated glomerular filtration rate>60mL/min/1.73m2), and without prior diagnosis of gout or use of ULT to treat gout. The primary outcome is change from baseline in blood pressure assessed by 24hour ambulatory blood pressure monitoring and mechanistic outcomes include changes in endothelial function as measured by flow-mediated dilation, as well as C-reactive protein levels. RESULTS: Since June 16, 2014 until present, SURPHER is recruiting participants in the city of Birmingham, Alabama. LIMITATIONS: The study aims to enroll otherwise healthy young adults for a pharmacological intervention study with multiple study-related procedures. Challenges related to recruitment are anticipated and multiple strategies for increasing recruitment and retention are planned if necessary.

Serum uric acid and the risk of hypertension and chronic kidney disease.

PURPOSE OF REVIEW: To discuss the evolving data regarding uric acid as a potential cause of hypertension and progressive renal dysfunction and its clinical and research implications. RECENT FINDINGS: The potential mechanisms by which uric acid could cause vasoconstriction and a progressive ateriolopathy were established in animal models between 1999 and 2004. Since then, there has been a growing interest in the topic and numerous retrospective and prospective observational studies. The preponderance of data support the hypothesis that serum uric acid is a cause or exacerbating factor of hypertension and progressive kidney disease. Over the last couple of years clinical intervention trials, including randomized controlled trials in the young have supported this mechanistic role. SUMMARY: Current evidence supports the role of uric acid as marker and mediator of risk for both hypertension and progressive decline in renal function. Data on the impact of xanthine oxidase inhibitors or uricosurics on clinical hypertension and chronic kidney disease are suggestive but inconclusive. Considerably, more data will be required to determine if uric acid lowering therapy will become a mainstay of management in diseases other than gout and tumor lysis syndrome.

Uric acid reduction rectifies prehypertension in obese adolescents.

Epidemiologic studies, animal models, and preliminary clinical trials in children implicate uric acid in the development of essential hypertension. Controversy remains as to whether the observations indicate a general mechanism or a surrogate phenomenon. We sought to determine whether uric acid is a causative mediator of increased blood pressure (BP) and impaired vascular compliance. We report a randomized, double-blinded, placebo-controlled trial comparing 2 mechanisms of urate reduction with placebo in prehypertensive, obese, adolescents, aged 11 to 17 years. Subjects were randomized to the xanthine oxidase inhibitor, allopurinol, uricosuric, probenecid, or placebo. Subjects treated with urate-lowering therapy experienced a highly significant reduction in BP. In clinic systolic BP fell 10.2 mm Hg and diastolic BP fell 9.0 mm Hg in treated patients compared with a rise of 1.7 mm Hg and 1.6 mm Hg systolic and diastolic BP, respectively in patients on placebo. Urate-lowering therapy also resulted in significant reduction in systemic vascular resistance. These data indicate that, at least in adolescents with prehypertension, uric acid causes increased BP that can be mitigated by urate lowering therapy.

Uric acid and hypertension: cause or effect?

Uric acid was first associated with primary hypertension in 1874, yet its role in this condition remains unclear. Historically, uric acid was thought to be a secondary response to hypertension or its associated conditions. However, more recent experimental and clinical studies suggest that uric acid could have a contributory role in the pathogenesis of elevated blood pressure. More studies are needed to help dissect the potential mechanisms by which uric acid could initiate this response. It remains possible that uric acid is a marker for xanthine oxidase-associated oxidants and that the latter could be driving the hypertensive response. However, the weight of the evidence suggests that uric acid is a true modifying and possibly causal factor for human primary hypertension. Hence, early management of hyperuricemia might delay the development of essential hypertension.

Minimal change disease with IgM+ immunofluorescence: a subtype of nephrotic syndrome.

Immunoglobulin (Ig) M nephropathy is defined by electron-dense mesangial deposits and mesangial IgM visible by immunofluorescence (IF) without other histopathologic and immunofluorescent microscopic abnormalities. Certain patients have only immuno-positive (IgM+) IF. Children presenting with steroid-dependent or steroid-resistant nephrotic syndrome have a high prevalence of IgM+ IF with or without electron-dense deposits. We reviewed the clinical course of children with steroid-dependent or steroid-resistant nephrotic syndrome who underwent renal biopsy at Texas Children's Hospital from 1989 to 2006 to further characterize IgM+ IF in children with nephrotic syndrome. Of the 55 children with steroid-resistant or -dependent minimal change disease (MCD), 23 had IgM+ IF. Of these 23 children, 61% had microscopic hematuria at presentation, 48% (11/23) were steroid-dependent, and 48% (11/23) steroid-resistant (one underwent biopsy prior to steroid therapy). We compared the efficacy of adjuvant treatment with cyclophosphamide and cyclosporine: 18% initially treated with cyclophosphamide obtained remission, while 55% had no response; 83% obtained subsequent remission with cyclosporine. Of those initially treated with cyclosporine, 88% obtained complete or partial remission. IgM+ IF may be surrogate marker for the severity of MCD. Based on our results, children with MCD and IgM+ IF have a better response to cyclosporine than cyclophosphamide.

Effect of allopurinol on blood pressure of adolescents with newly diagnosed essential hypertension: a randomized trial.

CONTEXT: Hyperuricemia is a predictor for the development of hypertension and is commonly present in new-onset essential hypertension. Experimentally increasing uric acid levels using a uricase inhibitor causes systemic hypertension in animal models. OBJECTIVE: To determine whether lowering uric acid lowers blood pressure (BP) in hyperuricemic adolescents with newly diagnosed hypertension. DESIGN, SETTING, AND PATIENTS: Randomized, double-blind, placebo-controlled, crossover trial (September 2004-March 2007) involving 30 adolescents (aged 11-17 years) who had newly diagnosed, never-treated stage 1 essential hypertension and serum uric acid levels > or = 6 mg/dL. Participants were treated at the Pediatric Hypertension Clinic at Texas Children's Hospital in Houston. Patients were excluded if they had stage 2 hypertension or known renal, cardiovascular, gastrointestinal tract, hepatic, or endocrine disease. INTERVENTION: Allopurinol, 200 mg twice daily for 4 weeks, and placebo, twice daily for 4 weeks, with a 2-week washout period between treatments. The order of the treatments was randomized. MAIN OUTCOME MEASURES: Change in casual and ambulatory blood pressure. RESULTS: For casual BP, the mean change in systolic BP for allopurinol was -6.9 mm Hg (95% confidence interval [CI], -4.5 to -9.3 mm Hg) vs -2.0 mm Hg (95% CI, 0.3 to -4.3 mm Hg; P = .009) for placebo, and the mean change in diastolic BP for allopurinol was -5.1 mm Hg (95% CI, -2.5 to -7.8 mm Hg) vs -2.4 (95% CI, 0.2 to -4.1; P = .05) for placebo. Mean change in mean 24-hour ambulatory systolic BP for allopurinol was -6.3 mm Hg (95% CI, -3.8 to -8.9 mm Hg) vs 0.8 mm Hg (95% CI, 3.4 to -2.9 mm Hg; P = .001) for placebo and mean 24-hour ambulatory diastolic BP for allopurinol was -4.6 mm Hg (-2.4 to -6.8 mm Hg) vs -0.3 mm Hg (95% CI, 2.3 to -2.1 mm Hg; P = .004) for placebo. Twenty of the 30 participants achieved normal BP by casual and ambulatory criteria while taking allopurinol vs 1 participant while taking placebo (P < .001). CONCLUSIONS: In this short-term, crossover study of adolescents with newly diagnosed hypertension, treatment with allopurinol resulted in reduction of BP. The results represent a new potential therapeutic approach, although not a fully developed therapeutic strategy due to potential adverse effects. These preliminary findings require confirmation in larger clinical trials. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00288184.

Recent advances in the diagnosis and treatment of pheochromocytoma in children.

BACKGROUND: The purpose of this study was to analyze the effects of changes in the diagnosis and treatment of pheochromocytoma in a pediatric population. METHODS: We reviewed the medical records of all children who had resection of pheochromocytoma or paraganglioma at a major children's hospital since 1968. RESULTS: Fifteen children underwent surgery at 11.9 +/- 4.2 years of age. Presenting symptoms included headache, hypertension, and sweating. Three children had a mutation of the succinate dehydrogenase enzyme, and 1 child had nonsyndromic, familial pheochromocytoma. The most sensitive diagnostic modalities included 24-hour urinary and plasma norepinephrine and 24-hour urinary total metanephrines, magnetic resonance imaging, and 123I-meta-iodobenzylguanidine scintigraphy. Laparoscopic cortical-sparing adrenalectomy was performed in 3 patients with von Hippel-Lindau disease. Compared with those with open procedures (n = 7), patients who had laparoscopic resection (n = 5) had a statistically shorter hospital length of stay, and time to eating ambulation. CONCLUSIONS: The addition of 123I-meta-iodobenzylguanidine scanning, genetic testing, and laparoscopic surgery has changed the diagnosis and treatment of pheochromocytoma in children. Laparoscopic cortical-sparing adrenalectomy can be accomplished safely and is the preferred treatment for children at risk for multifocal disease.