Evaluation of limited-sampling strategies to calculate AUC(0-24) and the role of CYP3A5 in Chilean pediatric kidney recipients using extended-release tacrolimus.

Background: Kidney transplantation (KTx) requires immunosuppressive drugs such as Tacrolimus (TAC) which is mainly metabolized by CYP3A5. TAC is routinely monitored by trough levels (C0) although it has not shown to be a reliable marker. The area-under-curve (AUC) is a more realistic measure of drug exposure, but sampling is challenging in pediatric patients. Limited-sampling strategies (LSS) have been developed to estimate AUC. Herein, we aimed to determine AUC(0-24) and CYP3A5 genotype in Chilean pediatric kidney recipients using extended-release TAC, to evaluate different LSS-AUC(0-24) formulas and dose requirements. Patients and methods: We analyzed pediatric kidney recipients using different extended-release TAC brands to determine their trapezoidal AUC(0-24) and CYP3A5 genotypes (SNP rs776746). Daily TAC dose (TAC-D mg/kg) and AUC(0-24) normalized by dose were compared between CYP3A5 expressors (*1/*1 and *1/*3) and non-expressors (*3/*3). We evaluated the single and combined time-points to identify the best LSS-AUC(0-24) model. We compared the performance of this model with two pediatric LSS-AUC(0-24) equations for clinical validation. Results: Fifty-one pharmacokinetic profiles were obtained from kidney recipients (age 13.1 ± 2.9 years). When normalizing AUC(0-24) by TAC-D significant differences were found between CYP3A5 expressors and non-expressors (1701.9 vs. 2718.1 ng*h/mL/mg/kg, p < 0.05). C0 had a poor fit with AUC(0-24) (r 2 = 0.5011). The model which included C0, C1 and C4, showed the best performance to predict LSS-AUC(0-24) (r 2 = 0.8765) and yielded the lowest precision error (7.1% ± 6.4%) with the lowest fraction (9.8%) of deviated AUC(0-24), in comparison to other LSS equations. Conclusion: Estimation of LSS-AUC(0-24) with 3 time-points is an advisable and clinically useful option for pediatric kidney recipients using extended-release TAC to provide better guidance of decisions if toxicity or drug inefficacy is suspected. The different CYP3A5 genotypes associated with variable dose requirements reinforce considering genotyping before KTx. Further multi-centric studies with admixed cohorts are needed to determine the short- and long-term clinical benefits.

Long-term outcome of early steroid withdrawal in pediatric renal transplantation.

BACKGROUND: Steroid use in renal transplant is related to multiple adverse effects. Long-term effects of early withdrawal steroids in pediatric renal transplant were assessed. METHODS: Renal transplant children with low immunological risk treated on basiliximab, tacrolimus, and mycophenolate with steroid withdrawal or steroid control were evaluated between 2003 and 2019. Clinical variables, treatment adherence, acute rejection, graft loss, and death were analyzed through hazard ratios, and Kaplan-Meier and multivariate analyses. RESULTS: The study included 152 patients, 71.1% steroid withdrawal, mean follow-up 8.5 years, 64.5% structural abnormalities, and 81.6% deceased donor. At 12 years of transplant, event-free survival analysis for graft loss or death showed no significant difference between steroid withdrawal and control steroid treatment (85.9% vs. 80.4%, p = .36) nor in acute rejection at 10 years (18.5% vs. 20.5%, p = .78) or in donor-specific antibody appearance (19.6% vs. 21.4%, p = .98). Delta height Z-score was increased in the steroid withdrawal group (p < .01). The main predictor of graft loss or death was non-adherence to treatment (p = .001; OR: 17.5 [3.3-90.9]). CONCLUSIONS: Steroid withdrawal therapy was effective and safe for low-risk pediatric renal transplant in long-term evaluation. Non-adherence was the main predictor of graft loss or death.

CYP3A5 and UGT1A9 Polymorphisms Influence Immunosuppressive Therapy in Pediatric Kidney Transplant Recipients.

Background: Tacrolimus (TAC) and mycophenolic acid (MPA) are the main immunosuppressive drugs used in pediatric kidney transplantation. Single nucleotide polymorphisms (SNPs) in metabolizing enzymes and transporters might influence plasma levels of these drugs. Herein, we sought to determine the influence of SNPs on CYP3A5, MRP2 and UGT1A9 genes in Chilean pediatric kidney recipients using TAC and MPA. Patients and Methods: A prospective study was performed on 104 pediatric kidney recipients that used TAC and MPA for immunosuppression. The median age at the time of transplantation was 8.1 years [Q1-Q3 4.5-11.6 years] and the main clinical diagnosis was a structural anomaly. In a subgroup of patients, a complete steroid withdrawal was made at day 7. The CYP3A5 polymorphism (ancestral allele *1; variant allele *3) was determined in the entire cohort, while MRP2 -24G > A, UGT1A9 -275T > A, and UGT1A9 -2152C > T polymorphisms were determined in 53 patients. Genotypes were associated with trough drug concentrations (C0), dose requirements normalized by weight (TAC-D mg/kg) or body surface (MPA-D mg/m2), trough levels normalized by dose requirements (C0/D), and area under the curve in 12 h normalized by dose requirements (AUC0-12h/D). Results: The frequencies of the variant alleles CYP3A5*3, MRP2-24A, UGT1A9-275A, and UGT1A9-2152T were 76.9, 22.1, 6.6, and 2.9%, respectively. AUC0-12h/TAC-D were 1.6-fold higher in CYP3A5*3/*3 patients than in CYP3A5*1 carriers (CYP3A5*1/*3 and CYP3A5*1/*1). When analyzing patients with steroid withdrawal, CYP3A5*3/*3 patients had 1.7-fold higher AUC0-12h/TAC-D than the other genotypes. Patients carrying the CYP3A5*3/*3 genotype had higher TAC-C0, lower TAC-D and higher TAC-C0/D, consistently in a 6-months follow-up. Creatinine clearance was stable during the follow-up, regardless of the genotype. No significant differences between MRP2 and UGT1A9 genotypes were observed in MPA-C0, MPA-D or MPA-C0/D. However, patients carrying the UGT1A9-275A allele had lower AUC0-12h/MPA-D than those carrying the UGT1A9-275T ancestral allele. Conclusions: These results support that CYP3A5 and UGT1A9 genotyping in pediatric recipients might be useful and advisable to guide TAC and MPA dosing and monitoring in children that undergo kidney transplantation.

[Blood hypertension in children. Guideliness for diagnosis and treatment. Part 2 Pediatric Nephrology Branch, Chilean Pediatric Society]. / Hipertensión arterial en la infancia. Recomendaciones para su diagnóstico y tratamiento. Parte 2 Rama de Nefrología Infantil, Sociedad Chilena de Pediatría.

Hypertension (HTN) in children and adolescents is an important pathology, of, guarded prognosis, associated with modifiable and non-modifiable factors. The estimated prevalence is around 3.5% which increases progressively with age. The ideal method for its diagnosis is the measurement of blood pressure (BP) with auscultatory instruments. According to the American Academy of Pedia trics (AAP), BP should be measured in children older than three years of age once a year, and in children younger than three years of age if they present risk factors. Once the HTN is confirmed, the evaluation should be directed towards the detection of a causative disease and/or the search for risk factors associated with a primary HTN. The objective of treating primary and secondary HTN in pediatrics is to achieve a BP level that decreases the risk of target organ damage. Therapeutic op tions include treatment according to specific etiology, non-pharmacological and pharmacological one. This paper presents the position of the Chilean Society of Pediatrics Nephrology Branch with the aim of guiding pediatricians and pediatric nephrologists in the correct management of HTN in childhood. In this second part, recommendations on antihypertensive treatment are presented with an emphasis on lifestyle changes.

Hipertensión arterial en la infancia: recomendaciones para su diagnóstico y tratamiento. Parte 2 Rama de Nefrología Infantil, Sociedad Chilena de Pediatría / Blood hypertension in children: guideliness for diagnosis and treatment. Part 2 Pediatric Nephrology Branch, Chilean Pediatric Society

Resumen: La hipertensión arterial (HTA) en niños y adolescentes es una importante patología, de reservado pronóstico, asociada a factores modificables y no modificables. La prevalencia estimada es de apro ximadamente un 3,5%, la cual va aumentando progresivamente con la edad. El método ideal para su diagnóstico es la medición de la presión arterial (PA) con instrumentos auscultatorios. De acuerdo a la Academia Americana de Pediatría (AAP) la PA debe ser medida en niños mayores de 3 años una vez al año, y en niños menores de 3 años, si presentan factores de riesgo. Una vez confirmada la HTA, la evaluación debe dirigirse hacia la detección de una enfermedad causal y/o a la búsqueda de factores de riesgo asociados a una HTA primaria. El objetivo del tratamiento de la HTA primaria y secundaria en pediatría es lograr un nivel de PA que disminuya el riesgo de daño de los órganos blanco. Las opciones terapéuticas incluyen: tratamiento según etiología específica, no farmacológico y farmacológico. En esta Guia se presenta la posición de la Rama de Nefrología de la Sociedad Chile na de Pediatría con el objetivo de orientar a pediatras y nefrólogos infantiles en correcto manejo de la HTA en la infancia. En esta segunda parte se presentan las recomendaciones sobre el tratamiento antihipertensivo, haciendo énfasis en los cambios de estilo de vida.

Abstract: Hypertension (HTN) in children and adolescents is an important pathology, of, guarded prognosis, associated with modifiable and non-modifiable factors. The estimated prevalence is around 3.5% which increases progressively with age. The ideal method for its diagnosis is the measurement of blood pressure (BP) with auscultatory instruments. According to the American Academy of Pedia trics (AAP), BP should be measured in children older than three years of age once a year, and in children younger than three years of age if they present risk factors. Once the HTN is confirmed, the evaluation should be directed towards the detection of a causative disease and/or the search for risk factors associated with a primary HTN. The objective of treating primary and secondary HTN in pediatrics is to achieve a BP level that decreases the risk of target organ damage. Therapeutic op tions include treatment according to specific etiology, non-pharmacological and pharmacological one. This paper presents the position of the Chilean Society of Pediatrics Nephrology Branch with the aim of guiding pediatricians and pediatric nephrologists in the correct management of HTN in childhood. In this second part, recommendations on antihypertensive treatment are presented with an emphasis on lifestyle changes.

[Blood hypertension in childrens. Guideliness for diagnosis and treatment. Part 1. Pediatric Nephrology Branch, Chilean Pediatric Society]. / Hipertensión arterial en la infancia. Recomendaciones para su diagnóstico y tratamiento. Parte 1. Rama de Nefrología Infantil, Sociedad Chilena de Pediatría.

Hypertension (HT) in children and adolescents is an important pathology, associated with modi fiable and non-modifiable factors. In the pediatric, the prevalence of HT is around 3.5%, and it in creases progressively with age. The ideal method for diagnosis is the measurement of blood pressure (BP) with auscultatory instruments. As published by the American Academy of Pediatrics (AAP), BP should be measured in children over 3 years of age once a year, and in children under 3 years of age, if it presents risk factors. Once HT has been confirmed, the evaluation should be directed towards the detection of a causative disease and the search for risk factors associated with primary HTN. The goal of treating primary and secondary HTN in pediatrics is to achieve a level of BP that decreases the risk of target organ damage. The therapeutic options include: treatment according to specific etiology, non-pharmacological and pharmacological. This document is the product of a collaborative effort of the Nephrology Branch of the Chilean Society of Pediatrics with the aim of helping pediatricians and pediatric nephrologists in the diagnosis and treatment of hypertension in childhood. In this first part, the recommendations of the diagnosis and study are presented.

Hipertensión arterial en la infancia: recomendaciones para su diagnóstico y tratamiento. Parte 1. Rama de Nefrología Infantil, Sociedad Chilena de Pediatría / Blood hypertension in childrens: guideliness for diagnosis and treatment. Part 1. Pediatric Nephrology Branch, Chilean Pediatric Society

Resumen: La hipertensión arterial (HTA) en niños y adolescentes es una patología importante, asociada a fac tores modificables y no modificables. En la edad pediátrica, la prevalencia de la HTA es de alrededor de un 3,5%, y va aumentando progresivamente con la edad. El método ideal para su diagnóstico es la medición de la presión arterial (PA) con instrumentos auscultatorios. Según lo publicado por la Academia Americana de Pediatría (AAP) la PA debe ser medida en niños mayores de 3 años una vez al año, y en niños menores de 3 años, si presenta factores de riesgo. Una vez confirmada la HTA, la evaluación debe dirigirse hacia la detección de una enfermedad causal y a la búsqueda de factores de riesgo asociados a una HTA primaria. El objetivo del tratamiento de la HTA primaria y secundaria en pediatría es lograr un nivel de PA que disminuya el riesgo de daño de órgano blanco. Las opcio nes terapéuticas incluyen: tratamiento según etiología específica, no farmacológico y farmacológico. Este documento es producto de un esfuerzo colaborativo de la Rama de Nefrología de la Sociedad Chilena de Pediatría con el objetivo de ayudar a los pediatras y nefrólogos infantiles en el diagnóstico y tratamiento de la HTA en la infancia. En esta primera parte, se presentan las recomendaciones del diagnóstico y estudio.

Abstract: Hypertension (HT) in children and adolescents is an important pathology, associated with modi fiable and non-modifiable factors. In the pediatric, the prevalence of HT is around 3.5%, and it in creases progressively with age. The ideal method for diagnosis is the measurement of blood pressure (BP) with auscultatory instruments. As published by the American Academy of Pediatrics (AAP), BP should be measured in children over 3 years of age once a year, and in children under 3 years of age, if it presents risk factors. Once HT has been confirmed, the evaluation should be directed towards the detection of a causative disease and the search for risk factors associated with primary HTN. The goal of treating primary and secondary HTN in pediatrics is to achieve a level of BP that decreases the risk of target organ damage. The therapeutic options include: treatment according to specific etiology, non-pharmacological and pharmacological. This document is the product of a collaborative effort of the Nephrology Branch of the Chilean Society of Pediatrics with the aim of helping pediatricians and pediatric nephrologists in the diagnosis and treatment of hypertension in childhood. In this first part, the recommendations of the diagnosis and study are presented.

Impaired phosphorylation of JAK2-STAT5b signaling in fibroblasts from uremic children.

BACKGROUND: Chronic kidney disease (CKD) in children is characterized by severe growth failure. The growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis in uremic animals shows a post-receptor impaired phosphorylation of Janus kinase 2/signal transducer and activator of transcription (JAK-STAT) proteins. The objective of our study was to characterize the intracellular phosphorylation of JAK-STAT signaling in fibroblasts from children with CKD on chronic peritoneal dialysis (PD). METHODS: Serum GH-binding protein (GHBP), IGF-1 and IGFBP3 were measured in 15 prepubertal CKD stage-5 children on PD. Cytoplasmic JAK2, cytoplasmic/nuclear STAT5b and nuclear IGFBP3, acid-labile subunit (ALS) and IGF-1 mRNA expression were quantified in fibroblasts obtained from skin biopsies before and after stimulation with 200 ng/ml recombinant human growth hormone (rhGH). Phosphorylation activity at both the cytoplasmic and nuclear level was expressed as the ratio phosphorylated (p)/total (t) abundance of the product (p/t) at 30 and 60 min. Fifteen healthy children were recruited as the control group. Values were expressed in arbitrary units (AU) and normalized for comparison. Significance was defined as p < 0.05. RESULTS: Thirty minutes after rhGH stimulus, the cytoplasmic (p/t) JAK2 ratio was significantly lower in patients than in controls [median and interquartile range (IQR): 7.4 (4.56) vs. 20.5 (50.06) AU]. At 60 min after rhGH stimulation, median JAK2 phosphorylation activity was still significantly lower in the patients [7.14 (IQR 3.8) vs. 10.2 (IQR 29.8) AU; p < 0.05]. The increase in the cytoplasmic (p/t) STAT5b/ß-actin ratio was lower at both measurement points in the patients compared to the controls, without reaching statistical significance between groups. Median IGFBP3 mRNA abundance was significantly decreased in fibroblasts from uremic patients 24 h after rhGH stimulation compared to the healthy controls [1.27 (IQR 0.83) vs. 2.37 (IQR 0.80) AU]. Median ALS and IGF-1 mRNA expression changed in response to rhGH stimuli at 24 and 48 h. CONCLUSION: In this study, children with CKD undergoing PD therapy showed an impaired phosphorylation of JAK2/STAT5b signaling in fibroblasts after GH stimulation, as well as impaired IGFBP3 mRNA abundance. Both impairments may be partially responsible for the observed resistance to the growth-promoting actions of GH in chronic kidney failure.

Longitudinal FGF23 and Klotho axis characterization in children treated with chronic peritoneal dialysis.

BACKGROUND: Fibroblast Growth Factor-23 (FGF23) and cofactor Klotho are key regulators of mineral metabolism in chronic kidney disease (CKD), but little is known about the mechanisms that regulate their production. This study evaluates longitudinal changes of FGF23 and Klotho levels and their regulatory factors in children on chronic peritoneal dialysis (PD). METHODS: FGF23, Klotho, 25(OH) vitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone (PTH) plasma concentrations were measured during 1 year of follow-up in PD children. Anthropometric and dialytical parameters were evaluated in addition to mineral metabolism variables. RESULTS: Thirty-one patients under chronic PD were followed for 12 months. FGF23 mean plasma levels at Month 1 were significantly increased compared with controls, 215.1 ± 303.6 versus 9.4 ± 5.7 pg/mL, respectively (P < 0.001). Baseline Klotho levels were 41% lower in patients compared with controls, 132.1 ± 58 versus 320 ± 119.4 pg/mL, respectively (P < 0.001), and did not correlate with FGF23 and phosphorus levels. At Month 12, FGF23 (195 ± 300 pg/mL) and Klotho levels (130 ± 34 pg/mL) remained similar to baseline values. Log-FGF23 correlated significantly with height/age Z score (r= -0.38) and residual renal function (r = -0.44), but no correlation was found with serum phosphorus, phosphate intake, PTH and vitamin D levels. The log-FGF23 strongly correlated with calcium levels at Months 1, 6 and 12, however, this relationship was blunted if serum phosphorus was >6 mg/dL. By multiple regression analysis, calcium was the strongest variable determining FGF23 levels. CONCLUSIONS: In this longitudinal study, FGF23 levels are markedly increased, and Klotho levels are reduced in PD children compared with controls. FGF23 levels appeared to be regulated primarily by serum calcium, showing a significant correlation at each time of measurement. This relationship was lost in patients with phosphorus >6 mg/dL. These observations may have important consequences to the therapeutic management of phosphate homeostasis in CKD patients.

The mini-PET in pediatric peritoneal dialysis: a useful tool to predict volume overload?

BACKGROUND: Cardiovascular disease (CVD) in patients on chronic peritoneal dialysis (PD) is a major cause of death and is closely linked to hypertension and volume overload. The mini-Pet has been proposed as a useful tool to evaluate free-water transport (FWT) and characterize ultrafiltration across the peritoneum. Knowledge regarding FWT could be of great value to predict volume overload in PD patients. Our objective in this study was to characterize FWT through the peritoneum in children on PD. METHODS: We studied clinically stable patients with >2 months on PD. Exclusion criteria were a peritonitis episode up to 2 months prior to entrance into the study and active nephrotic syndrome. A 1-h mini-peritoneal equilibration test (mini-PET) was performed with 3.86 % glucose. Calculations (see text for full definitions) were: Dip Na (Na dial min60 - Na dial min1), Dip D/PNa (D/PNa60 - D/PNa1), total Na removal (NaR = total Na dial60 - Na dial1), ultrafiltration small pores [(UFSP = NaR × 1,000)/Nap], and FWT (UF-UFSP). Peritoneal equilibration test (PET), left ventricular mass index (LVMI, g/m(2)), daily UF, and residual renal function were evaluated. Pearson's correlation coefficient was used to establish correlation between variables. RESULTS: Sixteen patients were included, with a mean age of 11.8 ± 3.8 years. Free water transport normalized to body surface area (BSA) (FWTn) was 133.9 ± 85.7 ml/m(2); creatinine dialysate-to-plasma (D/P) and glucose dialysate at X dwell time-to-0 dwell time (Dx/D0) ratios were 0.38 ± 0.1 and 0.65 ± 0.09, respectively. LVMI was 46.6 ± 14.8 g/m(2); 2-h creatinine D/P and glucose Dx/D0 showed no correlation with FWTn, UF, and LVMI. FWTn showed a significant inverse correlation with LVMI (r 0.58, p 0.02). CONCLUSIONS: This study characterized FWT in PD children through the mini-PET. Left ventricular hypertrophy showed a high prevalence in this group, and a significant correlation between LVMI and FWT was found. FWT could be a useful tool to evaluate UF in PD children.