Measurement of arginine derivatives in pediatric patients with chronic kidney disease using high-performance liquid chromatography-tandem mass spectrometry

Asymmetric and Symmetric Dimethylarginines as Renal Function Parameters in Paediatric Kidney Diseases: A Literature Review from 2003 to 2022

Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), inhibitors of nitric oxide synthase, play important roles in many processes in the body. Most data in the literature concern their importance in adult chronic kidney disease (CKD). According to them, SDMA well reflects the glomerular filtration rate (GFR), and higher ADMA concentrations are associated with hypertension and higher mortality. In addition, both substances are recognised cardiovascular risk factors in CKD. The purpose of this review was to summarise the studies on dimethylarginines in renal diseases in children, about which we have much fewer data. The review focuses specifically on dimethylarginine's relation to routinely used renal function parameters. Finally, we analysed 21 of the 55 articles published between 2003 and 2022 on dimethylarginines in kidney diseases in children (from birth to 18 years of age), obtained by searching PubMed/MEDLINE (search terms: "dimethylarginine" and "kidney").

Cardiovascular Risks of Hypertension: Lessons from Children with Chronic Kidney Disease

Hypertension is the most common complication of chronic kidney disease (CKD) in children, having a strong association with subsequential cardiovascular disease (CVD). In pediatric CKD, a considerable percentage of children with hypertension are undiagnosed or undertreated. Prior research has evaluated structural and functional markers of subclinical CVD and biomarkers in adults with CKD, while ideal biomarkers in pediatrics are still insufficiently studied. The ultimate goal of this review is to summarize what is currently known about state of hypertension, cardiovascular risk factors, and potential CVD markers/biomarkers in children with pre-dialysis CKD. We discuss omics-related biomarkers and the pathophysiologic processes of endothelial dysfunction, kidney injury, oxidative stress and inflammation that are classified by specific biomarkers. Moreover, we illustrate the existing challenges and highlight the paucity of pediatric CKD research to evaluate these CVD biomarkers for future clinical pediatric practice. Thus, achieving clinical utility of CVD biomarkers for use in pediatric CKD remains a significant challenge requiring additional efforts.

Asymmetric Dimethylarginine (ADMA) in Pediatric Renal Diseases: From Pathophysiological Phenomenon to Clinical Biomarker and Beyond

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, inhibits NO synthesis and contributes to the pathogenesis of many human diseases. In adults, ADMA has been identified as a biomarker for chronic kidney disease (CKD) progression and cardiovascular risk. However, little attention is given to translating the adult experience into the pediatric clinical setting. In the current review, we summarize circulating and urinary ADMA reported thus far in clinical studies relating to kidney disease in children and adolescents, as well as systematize the knowledge on pathophysiological role of ADMA in the kidneys. The aim of this review is also to show the various analytical methods for measuring ADMA and the issues tht need to be addressed before transforming to clinical practice in pediatric medicine. The last task is to suggest that ADMA may not only be suitable as a diagnostic or prognostic biomarker, but also a promising therapeutic strategy to treat pediatric kidney disease in the future.

Concentrations of representative uraemic toxins in a healthy versus non-dialysis chronic kidney disease paediatric population

Background

Chronic kidney disease (CKD) in childhood is poorly explained by routine markers (e.g. urea and creatinine) and is better depicted in adults by other uraemic toxins. This study describes concentrations of representative uraemic toxins in non-dialysis CKD versus healthy children.

Methods

In 50 healthy children and 57 children with CKD Stages 1-5 [median estimated glomerular filtration rate 48 (25th-75th percentile 24-71) mL/min/1.73 m2; none on dialysis], serum concentrations of small solutes [symmetric and asymmetric dimethyl-arginine (SDMA and ADMA, respectively)], middle molecules [β2-microglobuline (β2M), complement factor D (CfD)] and protein-bound solutes [p-cresylglucuronide (pCG), hippuric acid (HA), indole-acetic acid (IAA), indoxyl sulphate (IxS), p-cresyl sulphate (pCS) and 3-carboxy-4-methyl-5-propyl-furanpropionic acid (CMPF)] were measured. Concentrations in the CKD group were expressed as z-score relative to controls and matched for age and gender.

Results

SDMA, CfD, β2M, IxS, pCS, IAA, CMPF and HA concentrations were higher in the overall CKD group compared with controls, ranging from 1.7 standard deviations (SD) for IAA and HA to 11.1 SD for SDMA. SDMA, CfD, β2M, IxS and CMPF in CKD Stages 1-2 with concentrations 4.8, 2.8, 4.5, 1.9 and 1.6 SD higher, respectively. In contrast, pCS, pCG and IAA concentrations were only higher than controls from CKD Stages 3-4 onwards, but only in CKD Stage 5 for ADMA and HA (z-score 2.6 and 20.2, respectively).

Conclusions

This is the first study to establish reference values for a wide range of uraemic toxins in non-dialysis CKD and healthy children. We observed an accumulation of multiple uraemic toxins, each with a particular retention profile according to the different CKD stages.

Association of the -449GC and -1151AC polymorphisms in the DDAH2 gene with asymmetric dimethylarginine and erythropoietin resistance in Chinese patients on maintenance hemodialysis

We investigated the association of the -449G/C and -1151A/C polymorphisms in the DDAH2 gene with plasma asymmetric dimethylarginine (ADMA) concentration and erythropoietin resistance in 131 Chinese patients on maintenance hemodialysis (MHD). The -449G allele was in complete linkage disequilibrium with the -1151A allele and so were their corresponding C alleles. The -449GG/-1151AA genotype had the highest plasma ADMA concentration, erythropoietin resistance index (EPI) and serum malondialdehyde level, compared to either the -449GC/-1151AC or -449CC/-1151CC variation. The genetic effect on the ADMA and EPI was separately confirmed by multivariate regression analysis. Our findings suggested that complex genetic variations in the DDAH2 gene may influence the ADMA concentration and erythropoietin resistance in MHD patients, in which altered oxidative stress was likely involved.

Contribution of symmetric dimethylarginine to GFR decline in pediatric chronic kidney disease

BACKGROUND

In pediatric chronic kidney disease (pCKD), traditional factors (proteinuria, etiology, and race) do not fully explain disease progression. The levels of methylated arginine derivatives (MADs: asymmetric and symmetric dimethylarginine, respectively) rise in CKD and increase with CKD progression. The impact of MADs on glomerular filtration rate (GFR) decline has not been examined in pCKD. The aim of this study was to examine the additive impact of baseline (BL) levels of MADs on directly measured GFR (mGFR) decline per year (ml/min/1.73 m²/year) for a period of up to 4 years.

METHODS

Plasma and data, including mGFR by plasma iohexol clearance, were provided by the prospective, observational Chronic Kidney Disease in Children study. BL MADs were analyzed by high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

For 352 pCKD subjects, the median [interquartile range] BL mGFR was 45 [35, 57] ml/min/1.73 m². The levels of BL MADs were inversely related to the initial mGFR and its decline over time (p < 0.0005) but not to the rate of decline. Covariates, non-glomerulopathy and Tanner stage of ≥ 3 demonstrated weaker relationships between BL levels and beginning mGFR (p = 0.004 and p = 0.002, respectively).

CONCLUSIONS

In pCKD, higher concentrations of BL MADs were inversely related to BL mGFR. MADs did not affect the CKD progression rate. Quantification of this relationship is novel to the pCKD literature.

Asymmetric Dimethylarginine and Its Relation As a Biomarker in Nephrologic Diseases

It is encouraging to observe that a search for publications on "asymmetric dimethylarginine (ADMA)" in PubMed, as updated on June 2016, yielded >2500 items, 24 years after a splendid paper published by Vallance et al in which the authors proposed that ADMA accumulation could be a cardiovascular risk factor in chronic kidney diseases. ADMA is the endogenous inhibitor of nitric oxide synthase and is related to endothelial dysfunction, which plays an important role in vascular damage elicited by various cardiometabolic risk factors. Although current knowledge suggests that ADMA has critical central roles in renal diseases, there are still unexplained details. The present article aims to provide a review on ADMA and its relation as a biomarker in nephrologic diseases. We aimed to systematize articles in which ADMA levels were assessed in order to clarify its role in many diseases and establish its reference values in different populations.

Arginine dimethylation products in pediatric patients with chronic kidney disease

Background

arginine and its metabolites have been linked to pediatric chronic kidney disease (CKD). We aimed to estimate serum levels of argninine (Arg), asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) in pediatric CKD patients and its relation to altered kidney function.

Patients and methods

132 pediatric patients with CKD and 120 healthy age and sex matched controls were compared regarding; serum Arg, ADMA and SDMA levels.

Results

In comparison to their values in control subjects, serum Arg levels were significantly lower; serum ADMA levels were non-significantly higher, but serum SDMA levels were significantly higher in CKD patients (p values: < 0.000; = 0.054; <0.000, respectively).

Calculated Arg/ADMA and Arg/SDMA ratios were significantly higher in patients compared to controls (p values: 0.001, and <0.000, respectively). However ADMA/SDMA ratio was significantly lower in patients compared to controls (p = 0.001. Serum Arg levels showed positive significant correlation, while serum ADMA and SDMA levels showed negative significant correlation with eGFR. Moreover, Arg/ADMA ratio showed negative significant correlation, while ADMA/SDMA ratio showed positive significant correlation with eGFR of patients. Regression analysis defined high serum SDMA level as persistently significant predictor for low eGFR.

Conclusion

Disturbed serum levels of arginine and its dimethyl derivatives may underlie development and/or progression of CKD. Elevated serum SDMA level is strongly correlated with impaired kidney functions and could be considered as a predictor for kidney functions deterioration and CKD progression.

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The underlying pathogenic mechanisms for pediatric CKD are multiple and interlocking.

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Disturbed serum levels of Arg and its dimethyl derivatives may underlie development and/or progression of CKD.

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Elevated serum SDMA level is strongly correlated with impaired kidney functions.

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Elevated SDMA level can be a predictor for kidney functions deterioration and CKD progression.

Plasma concentrations of three methylated arginines, endogenous nitric oxide synthase inhibitors, in schizophrenic patients undergoing antipsychotic drug treatment

Plasma concentration of three methylated arginines, endogenous nitric oxide synthase inhibitors, is not studied in schizophrenic patients. The purpose of this study was to determine plasma concentrations of N(G)-monomethyl-L-arginine (l-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), N(G),N(G')-dimethyl-L-arginine (SDMA), and l-arginine in 56 male and 45 female schizophrenic patients undergoing antipsychotic drug treatment versus those of 39 male and 24 female healthy controls. Plasma concentrations of methylated arginines and l-arginine were measured using newly developed high performance liquid chromatography with fluorescence detection which we previously reported. Methylated arginine levels were slightly but significantly higher in schizophrenic patients. L-Arginine levels and the l-arginine/(ADMA+l-NMMA) ratio were higher in schizophrenic patients than in healthy controls. It is considered that pharmacological treatment of schizophrenic patients may lower methylated arginine levels that are increased by the disease, and increase L-arginine levels, eliciting an improvement in nitric oxide (NO) bioavailability.

Skin autofluorescence as a novel marker of vascular damage in children and adolescents with chronic kidney disease

BACKGROUND

Skin autofluorescence (sAF) was examined as a marker of the accumulation of advanced glycation end products (AGEs) in tissues of children with chronic kidney disease (CKD) in relation to renal function, dialysis modality and markers of endothelial inflammation and dysfunction.

METHODS

A total of 76 children with CKD were enrolled in the study, of whom 20 children were on hemodialysis (HD), 20 were on peritoneal dialysis (PD) and 36 were treated conservatively. A control group of 26 healthy subjects was also included in the study. In all children, sAF intensity, carotid intima-media (cIMT) thickness and plasma concentrations of sE-selectin, matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1), asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and plasminogen activator inhibitor type 1 (PAI-1) were measured.

RESULTS

Compared to the controls, children with CKD had significantly elevated sAF levels. sAF in the children with CKD was positively correlated with sE-selectin, MMP-9, TIMP-1, ADMA, SDMA and PAI-1 levels. In the predialysis group (conservative treatment) sAF levels were positively correlated with sE-selectin and ADMA levels and negatively correlated with glomerular filtration rate. Multiple regression analysis showed a significant association of sAF with sE-selectin and MMP-9 in CKD children.

CONCLUSIONS

The results reveal that AGEs were accumulated in the children with CKD. This accumulation was related to early vascular changes and a number of biochemical vascular risk markers. sAF measurement, as a noninvasive method, may be useful for identification of clinical risk factors of vascular disease in CKD children.

Asymmetric dimethylarginine, endothelial dysfunction and renal disease

l-Arginine (Arg) is oxidized to l-citrulline and nitric oxide (NO) by the action of endothelial nitric oxide synthase (NOS). In contrast, protein-incorporated Arg residues can be methylated with subsequent proteolysis giving rise to methylarginine compounds, such as asymmetric dimethylarginine (ADMA) that competes with Arg for binding to NOS. Most ADMA is degraded by dimethylarginine dimethyaminohydrolase (DDAH), distributed widely throughout the body and regulates ADMA levels and, therefore, NO synthesis. In recent years, several studies have suggested that increased ADMA levels are a marker of atherosclerotic change, and can be used to assess cardiovascular risk, consistent with ADMA being predominantly absorbed by endothelial cells. NO is an important messenger molecule involved in numerous biological processes, and its activity is essential to understand both pathogenic and therapeutic mechanisms in kidney disease and renal transplantation. NO production is reduced in renal patients because of their elevated ADMA levels with associated reduced DDAH activity. These factors contribute to endothelial dysfunction, oxidative stress and the progression of renal damage, but there are treatments that may effectively reduce ADMA levels in patients with kidney disease. Available data on ADMA levels in controls and renal patients, both in adults and children, also are summarized in this review.

Elevated preoperative serum asymmetrical dimethylarginine (ADMA) is associated with poor outcomes after pediatric cardiac surgery

PURPOSE

Asymmetrical dimethylarginine (ADMA), an endogenous competitive inhibitor of nitric oxide synthase, is elevated in vascular pathologies such as hypertension and chronic kidney disease. Children undergoing cardiac surgery are at high risk of poor hemodynamic and renal outcomes secondary to cardiopulmonary bypass (CPB). This study tested the hypothesis that elevated preoperative ADMA levels are associated with overall worse clinical outcomes after pediatric CPB.

METHODS

This was a prospective, observational study of 100 patients aged from 2 weeks to 18 years who underwent cardiac surgery involving CPB. Serum ADMA levels were obtained preoperatively and on postoperative days zero through four. Clinical outcomes measured included acute kidney injury (AKI) by pRIFLE criteria, low cardiac output syndrome (LCOS), length of mechanical ventilation, hospital and ICU length of stay, unplanned reoperation, and mortality.

RESULTS

The 29 patients with an elevated preoperative ADMA were more likely to have prolonged mechanical ventilation, increased ICU and hospital length of stay, unplanned reoperation, and LCOS than those with a normal preoperative level. ADMA levels inversely correlated with estimated glomerular filtration rate (eGFR), but did not differ between patients with and without AKI after CPB. Preoperative ADMA levels correlated with hospital length of stay (r(s) = 0.289), ICU length of stay (r(s) = 0.308), and length of mechanical ventilation (r(s) = 0.402); [all p < 0.05]. ADMA levels before surgery had good predictive power for prolonged mechanical ventilation (AUC-ROC 0.809; 95 % CI 0.704, 0.914; p < 0.001).

CONCLUSIONS

Patients with elevated ADMA before surgery were more likely to have prolonged mechanical ventilation, develop LCOS, require an extended length of stay, and require reoperation. ADMA levels inversely correlated with eGFR, but did not predict AKI. Preoperative serum ADMA appears to identify pediatric cardiac surgery patients at risk of poor postoperative outcomes following CPB.

Evaluation of asymmetric dimethylarginine, arginine, and carnitine metabolism in pediatric sepsis

OBJECTIVE

Increased plasma concentrations of the endogenous nitric oxide synthase inhibitor, asymmetric dimethylarginine, decreased arginine bioavailability, and mitochondrial dysfunction have been reported in adult sepsis. We studied whether asymmetric dimethylarginine, arginine, and carnitine metabolism (a measure of mitochondrial dysfunction) are altered in pediatric sepsis and whether these are clinically useful biomarkers.

DESIGN

: Prospective, observational study.

SETTING

Pediatric intensive care unit at an academic medical center.

PATIENTS

: Ninety patients ≤ 18 yrs old, 30 with severe sepsis or septic shock, compared with 30 age-matched febrile and 30 age-matched healthy control subjects.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma asymmetric dimethylarginine and whole blood arginine, citrulline, ornithine, and acylcarnitine:free carnitine ratio were measured daily for septic patients and once for control subjects using tandem mass spectrometry. Plasma asymmetric dimethylarginine concentration (median; interquartile range µmol/L) on day 1 was lower in severe sepsis and septic shock (0.38; 0.30-0.56) compared with febrile (0.45; 0.40-0.59) and healthy (0.60; 0.54-0.67) control subjects (p < .001), although decreased asymmetric dimethylarginine was predominantly found in neutropenic patients. Day 1 arginine was lower in septic (10; interquartile range, 7-20 µmol/L) compared with healthy patients (32; interquartile range, 23-40; p < .001), and the arginine:ornithine ratio was decreased in sepsis, indicating increased arginase activity (an alternative pathway for arginine metabolism). The arginine:asymmetric dimethylarginine and acylcarnitine:free carnitine ratios did not differ between septic and control patients. Asymmetric dimethylarginine was inversely correlated with organ dysfunction by Pediatric Logistic Organ Dysfunction score (r = -0.50, p = .009), interleukin-6 (r = -0.55, p = .01), and interleukin-8 (r = -0.52, p = .03) on admission. Arginine, arginine:asymmetric dimethylarginine, and acylcarnitine:free carnitine were not associated with organ dysfunction or outcomes.

CONCLUSIONS

Asymmetric dimethylarginine was decreased in pediatric sepsis and was inversely associated with inflammation and organ dysfunction. This suggests that inhibition of nitric oxide synthase by asymmetric dimethylarginine accumulation is unlikely to impact sepsis pathophysiology in septic children despite decreased arginine bioavailability. We did not find an association of asymmetric dimethylarginine with altered carnitine metabolism nor were asymmetric dimethylarginine, arginine, and acylcarnitine:free carnitine useful as clinical biomarkers.

Pilot study of the association of the DDAH2 -449G polymorphism with asymmetric dimethylarginine and hemodynamic shock in pediatric sepsis

Background

Genetic variability in the regulation of the nitric oxide (NO) pathway may influence hemodynamic changes in pediatric sepsis. We sought to determine whether functional polymorphisms in DDAH2, which metabolizes the NO synthase inhibitor asymmetric dimethylarginine (ADMA), are associated with susceptibility to sepsis, plasma ADMA, distinct hemodynamic states, and vasopressor requirements in pediatric septic shock.

Methodology/Principal Findings

In a prospective study, blood and buccal swabs were obtained from 82 patients ≤18 years (29 with severe sepsis/septic shock plus 27 febrile and 26 healthy controls). Plasma ADMA was measured using tandem mass spectrometry. DDAH2 gene was partially sequenced to determine the −871 6g/7g insertion/deletion and −449G/C single nucleotide polymorphisms. Shock type (“warm” versus “cold”) was characterized by clinical assessment. The −871 7g allele was more common in septic (17%) then febrile (4%) and healthy (8%) patients, though this was not significant after controlling for sex and race (p = 0.96). ADMA did not differ between −871 6g/7g genotypes. While genotype frequencies also did not vary between groups for the −449G/C SNP (p = 0.75), septic patients with at least one −449G allele had lower ADMA (median, IQR 0.36, 0.30–0.41 µmol/L) than patients with the −449CC genotype (0.55, 0.49–0.64 µmol/L, p = 0.008) and exhibited a higher incidence of “cold” shock (45% versus 0%, p = 0.01). However, after controlling for race, the association with shock type became non-significant (p = 0.32). Neither polymorphism was associated with inotrope score or vasoactive infusion duration.

Conclusions/Significance

The −449G polymorphism in the DDAH2 gene was associated with both low plasma ADMA and an increased likelihood of presenting with “cold” shock in pediatric sepsis, but not with vasopressor requirement. Race, however, was an important confounder. These results support and justify the need for larger studies in racially homogenous populations to further examine whether genotypic differences in NO metabolism contribute to phenotypic variability in sepsis pathophysiology.

Plasma asymmetric dimethylarginine and L-arginine levels in Chinese patients with essential hypertension without coronary artery disease

Objective:

To investigate the plasma asymmetric dimethylarginine (ADMA) levels and L-arginine in the essential hypertension (EH) patients without coronary artery disease.

Patients and Methods:

A total of 86 Chinese patients were enrolled in this study. All patients received coronary multidetector-row computed tomography to exclude distinct coronary stenosis and treadmill exercise testing to exclude microvascular angina pectoris. The patients with normal blood pressure (n = 26) were set as the control group. The EH patients were divided into three subgroups: the prehypertension group (n = 26), the stage 1 hypertension group (n = 26) and the stage 2 hypertension group (n = 8). The plasma ADMA and L-arginine concentrations were measured by a validated high-throughput liquid chromatographic tandem mass spectrometric assay.

Results:

There was a significantly higher ADMA level [0.028 (0.016) mmol/L vs. 0.021 (0.010) mmol/L, P = 0.002] and lower L-arginine to ADMA ratio [1.42 (0.58) vs. 2.01 (0.99), P < 0.001] in the EH group compared with the control group. Among the EH patients, the ADMA levels were increased by grades of hypertension [0.028 (0.011) mmol/L, 0.027 (0.014) mmol/L, 0.035 (0.024) mmol/L, respectively, P < 0.001]. The ADMA level was independently related to the systolic blood pressure (r = 1.047, P = 0.001).

Conclusion:

The plasma ADMA levels were significantly elevated with grades of hypertension in EH patients and were positively related to the systolic blood pressure levels.

Cardiovascular disease in children with CKD or ESRD

Cardiovascular disease accounts for 40% of all deaths among pediatric patients with end-stage renal disease (ESRD). ESRD has a particularly large influence on the cardiovascular system in children, as indicated by the more than 700-fold increased risk of cardiac death in affected individuals compared with healthy children of the same age. The prevalence of ESRD is low in children, however, and, consequently, few cardiac deaths occur. As a result, prospective follow-up studies of cardiac risk factors in the pediatric setting are lacking. Nevertheless, cross-sectional data on cardiac disease in children with ESRD have started to emerge. Arterial medial calcification is more prominent in children than classic atherosclerotic intimal calcification. Current data suggest that endothelial dysfunction appears early in renal failure in children, and is followed by arterial medial calcification. This calcification causes arterial wall stiffening and subsequently left ventricular hypertrophy. High systolic blood pressure and serum concentrations of intact parathyroid hormone, calcium and phosphate, as well as long-term dialysis, seem to be important risk factors for cardiovascular disease in pediatric patients with ESRD. These features are important targets for preventive intervention. This Review summarizes the currently available data on cardiovascular disease in children with renal failure.

Methylated arginine derivatives in children and adolescents with chronic kidney disease

Asymmetric dimethylarginine (ADMA), a methylated L: -arginine (Arg) derivative is associated with endothelial dysfunction, vasoconstriction, and hypertension in animals and humans. We examined the relationship between these derivatives, estimated glomerular filtration rate (eGFR), and awake (AW) and asleep (AS) blood pressure (BP) load in children and adolescents (n = 28) with stage 2-3 chronic kidney disease (CKD) and in matched intra-familial controls (n = 10). Plasma L: -Arg, ADMA, and symmetric dimethylarginine (SDMA) levels were measured by high-performance liquid chromatography-tandem mass spectrometry. Subjects wore a 24-hr ambulatory BP monitor with BP load >95th percentile. ADMA, SDMA/ADMA ratio and SDMA were 38-200% higher in CKD patients while L: -Arg/ADMA and L: -Arg/SDMA ratios and the L: -Arg level were 11-64% lower. The eGFR explained 42-60% of L: -Arg/SDMA, SDMA/ADMA, and SDMA variability (n = 38). Using linear regression, SDMA and SDMA/ADMA separately explained 15-38% of AW and AS systolic (S) BP and diastolic (D) BP load variability (p < 0.001-0.022). Using multivariate stepwise regression with eGFR held constant, SDMA/ADMA was a significant independent variable for AW DBP load (p = 0.03). In conclusion, BP load and a disproportionate elevation of SDMA are seen in children and adolescents with stage 2-3 (mild-moderate) CKD. SDMA is a strong marker for reduced eGFR and serves as a moderate but significant indicator of 24-hr BP load variability.