Is symmetric dimethylarginine a sensitive biomarker of subclinical kidney injury in children born with low birth weight?

Dimethylarginines in Children after Anti-Neoplastic Treatment

Background and Objectives: According to a recent Cochrane systematic review, renal impairment can develop in 0–84% of childhood cancer survivors in the future. The renal function impairment in this patient group can be related to nephrectomy, nephrotoxic agents therapy, abdominal radiotherapy, and combinations of these treatment methods. In this study, in a population of patients after anti-neoplastic therapy, with particular emphasis on patients after Wilms’ tumour treatment, we compared new substances which play role in the chronic kidney disease (CKD) pathogenesis (asymmetric dimethylarginine—ADMA, symmetric dimethylarginine—SDMA) with standard renal function markers (e.g., creatinine and cystatin C in serum, creatinine in urine, etc.) to assess the usefulness of the former. Materials and Methods: Eighty-four children, without CKD, bilateral kidney tumours, congenital kidney defects, or urinary tract infections, with a minimum time of 1 year after ending anti-neoplastic treatment, aged between 17 and 215 months, were divided into three groups: group 1—patients after nephroblastoma treatment (n = 21), group 2—after other solid tumours treatment (n = 44), and group 3—after lymphoproliferative neoplasms treatment (n = 19). The patients’ medical histories were taken and physical examinations were performed. Concentrations of blood urea nitrogen (BUN), creatinine, cystatin C, C-reactive protein (CRP), ADMA, and SDMA in blood and albumin in urine were measured, and a general urine analysis was performed. The SDMA/ADMA ratio, albumin–creatine ratio, and estimated glomerular filtration rate (eGFR) were calculated. eGFR was estimated by three equations recommended to the paediatric population by the KDIGO from 2012: the Schwartz equation (eGFR1), equation with creatinine and urea nitrogen (eGFR2), and equation with cystatin C (eGFR3). Results: Both the eGFR1 and eGFR2 values were significantly lower in group 1 than in group 3 (eGFR1: 93.3 (83.1–102.3) vs. 116.5 (96.8–126.9) mL/min/1.73 m², p = 0.02; eGFR2: 82.7 (±14.4) vs. 94.4 (±11.9) mL/min/1.73 m², p = 0.02). Additionally, there were weak positive correlations between SDMA and creatinine (p < 0.05, r = 0.24), and cystatin C (p < 0.05, r = 0.32) and weak negative correlations between SDMA and eGFR1 (p < 0.05, r = −0.25), eGFR2 (p < 0.05, r = −0.24), and eGFR3 (p < 0.05, r = −0.32). Conclusions: The usefulness of ADMA and SDMA in the diagnosis of renal functional impairment should be assessed in further studies. eGFR, calculated according to equations recommended for children, should be used in routine paediatric practice.

Serum symmetric dimethylarginine concentration in healthy neonatal Thoroughbred foals

BACKGROUND

Symmetric dimethylarginine (SDMA) is widely used in other species as a marker of renal dysfunction and is considered a more sensitive indicator of glomerular filtration rate than creatinine. Reference ranges are established in healthy adult horses (≤14 μg/dL) and concentrations are increased in horses with acute kidney injury (median 32 μg/dL; range 15-92).

OBJECTIVES

To establish the normal range of SDMA concentrations in neonatal Thoroughbreds.

STUDY DESIGN

Cross-sectional.

METHODS

Blood samples were collected from Thoroughbred foals <36 h old deemed healthy by physical examination. Exclusion criteria included foals from mares undergoing treatment for placentitis and foals that developed clinical disease or died/euthanised <2 weeks from birth. Biochemistry and serum SDMA concentrations were obtained.

RESULTS

Subjects included 120 foals. Median age was 13.5 h (range 1.0-34.0). Median and 95% confidence interval for SDMA concentration was 69.0 µg/dL (63.0, 75.0; range 35.0-376.0). A cut-off value of 168 µg/dL would include 95% of individuals and is therefore suggested. Serum SDMA concentration was correlated with age (R = -.3, P = .003), creatinine concentration (R = .6, P ≤ .001) and urea concentration (R = .3, P = .002).

MAIN LIMITATIONS

Limitations include a small sample size, no consideration of subclinical disease and a short follow-up period.

CONCLUSIONS

In equine neonates, SDMA concentration is higher than in adult horses, older foals and adults with acute kidney injury. Therefore, currently SDMA cannot be used as a marker of renal dysfunction in this age group. Further work is required to assess whether SDMA concentration is increased in neonates with renal disease and, if so, what cut-off should be used.

Serum symmetric dimethylarginine concentration in healthy horses and horses with acute kidney injury

BACKGROUND

There are limited options to diagnose acute kidney injury (AKI) in horses. Symmetric dimethylarginine (SDMA) is routinely used in human and small animal medicine. The aim of this study was to assess serum SDMA concentrations in healthy horses and horses with AKI. The objective of this study was to evaluate the association of: 1) age, 2) sex, 3) body weight and 4) serum creatinine and urea levels on serum SDMA concentrations. Fifty-three healthy horses, including 17 foals (2-6 months of age) and 36 adult horses (3-29 years of age), and 23 horses with AKI were included in the study based on history, physical examination, blood analysis, urinalysis and an ultrasonographic examination of the urinary tract. Serum SDMA concentrations were measured using a non-species specific commercial ELISA test.

RESULTS

In healthy adult horses, the value of SDMA was 0.53 ± 0.14 μmol/L. The value was higher in foals (1.5 ± 0.4 μmol/L, P < 0.001). Horses with AKI had significantly higher concentrations of SDMA compared to healthy horses (1.76 ± 1.05 μmol/L, P < 0.001). In the healthy adult horses, there was no association of sex, age or body weight on SDMA. However, a significant positive relationship was found between serum creatinine and SDMA concentrations.

CONCLUSIONS

Healthy adult horses had SDMA values similar to those of other species. Foals had higher SDMA values. Therefore, different reference values should be created for them. The study confirmed an increased SDMA in horses with AKI. This, as well as the low influence of extrarenal factors on the SDMA values, may confirm its usefulness in the diagnosis of kidney dysfunction. Higher SDMA values may also indicate a more advanced degree of kidney dysfunction. Further research is required to determine whether SDMA could be used to detect kidney dysfunction in the asymptomatic stage of AKI.

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.

•

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

•

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

•

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

•

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