Evaluation of Renal Function in Obese Children and Adolescents Using Serum Cystatin C Levels, Estimated Glomerular Filtration Rate Formulae and Proteinuria: Which is most Useful?

Application of Physiologically Based Pharmacokinetic Modeling to Characterize the Effects of Age and Obesity on the Disposition of Levetiracetam in the Pediatric Population

BACKGROUND

Levetiracetam is an antiseizure medication used for several seizure types in adults and children aged 1 month and older; however, due to a lack of data, pharmacokinetic (PK) variability of levetiracetam is not adequately characterized in certain populations, particularly neonates, children younger than 2 years of age, and children older than 2 years of age with obesity.

OBJECTIVE

This study aimed to address the gap by leveraging PK data from two prospective standard-of-care pediatric trials (n = 88) covering an age range from 1 month to 19 years, including those with obesity (64%), and applying a physiologically based PK (PBPK) modeling framework.

METHODS

A published PBPK model of levetiracetam for children aged 2 years and older was extended to pediatric patients younger than 2 years of age and patients older than 2 years of age with obesity by accounting for the obesity and age-related changes in PK using PK-Sim® software. The prospective pediatric data, along with the literature data for neonates and children younger than 2 years of age, were used to evaluate the extended PBPK models.

RESULTS

Overall, 82.4% of data fell within the 90% interval of model-predicted concentrations, with an average fold error within twofold of the accepted criteria. PBPK modeling revealed that children with obesity had lower weight-normalized clearances (0.053 L/h/kg) on average than children without obesity (0.063 L/h/kg). The effect of maturation was well-characterized, resulting in comparable PBPK-simulated, weight-normalized clearances for neonates and children younger than 2 years of age reported from the literature.

CONCLUSIONS

PBPK modeling simulations revealed that the current US FDA-labeled pediatric dosing regimen listed in the prescribing information can produce the required exposure of levetiracetam in these target populations with dose adjustments for children with obesity aged 4 years to younger than 16 years.

Neutralizing MIP3α Reduces Renal Immune Cell Infiltration and Progressive Renal Injury in Young Obese Dahl Salt-Sensitive Rats

Recently, we reported that the early progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant (SSLepRmutant) rats was associated with increased macrophage inflammatory protein 3-α (MIP3α) expression prior to puberty. Therefore, this study tested the hypothesis that MIP3α plays a role in recruiting immune cells, thereby triggering renal inflammation and early progressive renal injury in SSLepRmutant rats prior to puberty. Four-week-old Dahl salt-sensitive (SS) and SSLepRmutant rats either served as control (IgG; intraperitoneal, every other day) or received MIP3α-neutralizing antibody (MNA; 100 µg/kg) for 4 weeks. MNA reduced circulating and renal MIP3α levels and proinflammatory immune cells by 50%. Although MNA treatment did not affect blood glucose and plasma cholesterol levels, MNA markedly decreased insulin resistance and triglyceride levels in SSLepRmutant rats. We observed no differences in mean arterial pressure (MAP) between SS and SSLepRmutant rats, and MNA had no effect on MAP in either strain. Proteinuria was significantly increased in SSLepRmutant rats versus SS rats over the course of the study. Treatment with MNA markedly decreased proteinuria in SSLepRmutant rats while not affecting SS rats. Also, MNA decreased glomerular and tubular injury and renal fibrosis in SSLepRmutant rats while not affecting SS rats. Overall, these data indicate that MIP3α plays an important role in renal inflammation during the early progression of renal injury in obese SSLepRmutant rats prior to puberty. These data also suggest that MIP3α may be a novel therapeutic target to inhibit insulin resistance and prevent progressive proteinuria in obese children. SIGNIFICANCE STATEMENT: Childhood obesity is increasing at an alarming rate and is now being associated with renal disease. Although most studies have focused on the mechanisms of renal injury associated with adult obesity, few studies have examined the mechanisms of renal injury involved during childhood obesity. In the current study, we observed that the progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant rats was associated with an increase in MIP3α, a chemokine, before puberty, and inhibition of MIP3α markedly reduced renal injury.

Lipid metabolism and renal function markers in obese adolescents

AIM OF THE STUDY

To investigate the relationship of renal function markers and lipid metabolism parameters in obese adolescents.

MATERIAL AND METHODS

The study comprised 76 children aged 11-17 years, hospitalised due to: obesity (group I - 19 children) or obesity accompanied by obesity-induced hypertension (group II - 30 children) or normosthenic children with a diagnosed tension headaches (control group - 27 children). A subgroup with metabolic syndrome (MS - 16 children) was also separated. Renal function was assessed on the basis of: serum creatinine concentration, glomerular filtration rate estimated using Schwartz eqation (eGFR), determination of plasma and urinary neutrophil gelatinase-associated lipocalin and cystatin C. On the basis of statistical analysis, it was checked whether renal function markers depend on lipid metabolism parameters.

RESULTS

In the study groups mean creatinine concentrations were significantly higher and eGFR values significantly lower than in the control group, but they remained within norm. Differences in plasma and urinary neutrophil gelatinase-associated lipocalin concentrations were not significant. Mean cystatin C concentrations were significantly higher in the group of obese children. Multiple linear regression analysis showed that the most important predictor was: LDL-C for urinary neutrophil gelatinase-associated lipocalin (R2 = 0.42) and TG for eGFR (R2 = 0.44) concentrations in group I; cholesterol for creatinine concentrations in MS group (R2 = 0.44).

CONCLUSIONS

Renal function of the obese adolescents included in the study was normal and the associations with lipid metabolism were poorly expressed.

Novel insights in classic versus relative glomerular hyperfiltration and implications on pharmacotherapy

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) assessment and its estimation (eGFR) is a long-lasting challenge in medicine and public health. Current eGFR formulae are indexed for standardized body surface area (BSA) of 1.73 m2, ignoring persons and populations wherein the ratio of BSA or metabolic rate to nephron number might be different, due to increased BSA, increased metabolic rate or reduced nephron number. These equations are based on creatinine, cystatin C or a combination of the two, which adds another confounder to eGFR assessment. Unusually high GFR values, also known as renal hyperfiltration, have not been well defined under these equations.

RECENT FINDINGS

Special conditions such as solitary kidney in kidney donors, high dietary protein intake, obesity and diabetes are often associated with renal hyperfiltration and amenable to errors in GFR estimation. In all hyperfiltration types, there is an increased intraglomerular pressure that can be physiologic, but its persistence over time is detrimental to glomerulus leading to progressive glomerular damage and renal fibrosis. Hyperfiltration might be underdiagnosed due to BSA standardization embedded in the formula. Hence, timely intervention is delayed. Reducing intraglomerular pressure in diabetes can be achieved by SGLT2 inhibitors or low protein diet to reverse the glomerulopathy process.

SUMMARY

Accurate identification of glomerular hyperfiltration as a pre-CKD condition needs accurate estimation of GFR in the above normal range should establish a threshold for timely intervention.

Early childhood fluoride exposure and preadolescent kidney function

BACKGROUND

Early-life renal maturation is susceptible to nephrotoxic environmental chemicals. Given the widespread consumption of fluoride and the global obesity epidemic, our main aim was to determine whether childhood fluoride exposure adversely affects kidney function in preadolescence, and if adiposity status modifies this association.

METHODS

Our study included 438 children from the PROGRESS cohort. Urinary fluoride (uF) was assessed at age 4 by diffusion analysis; outcomes studied included estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), selected kidney proteins and blood pressure measured at age 8-12 years. We modeled the relationship between uF and outcomes, and adjusted for body mass index (BMI), age, sex, and socioeconomic status.

RESULTS

The median uF concentration was 0.67 μg/mL. We observed null associations between 4-year uF and preadolescent eGFR, although effect estimates were in the expected inverse direction. A single unit increase in ln-transformed uF was associated with a 2.2 mL/min decrease in cystatin C-based eGFR (95% CI: 5.8, 1.4; p = 0.23). We observed no evidence of sex-specific effects or effect modification by BMI status. Although uF was not associated with BMI, among children with obesity, we observed an inverse association (β: 4.8; 95% CI: 10.2, 0.6; p = 0.08) between uF and eGFR.

CONCLUSIONS

Low-level fluoride exposure in early childhood was not associated with renal function in preadolescence. However, given the adverse outcomes of chronic fluoride consumption it is possible that the preadolescent age was too young to observe any effects. Longitudinal follow-up in this cohort and others is an important next step.

Assessment of Cystatin-C level in Newly Diagnosed Iraqi Children with Nephritic Syndrome

BACKGROUND: Nephritic syndrome (NS) is a common kidney disease in children that causes protein leakage from the blood into the urine due to glomerular injury. AIM: The aim of this research was to determine the level of Cystatin-C (CysC) and other biochemical parameters in newly diagnosed NS children in Iraq. PATIENTS AND METHODS: Ninety Iraqi children divided into: 50 children with newly diagnosed NS (28 boys and 22 girls) aged between (4 and 16) years, and 40 healthy control children (20 boys and 20 girls) aged between (5 and 16) years, who were attending Al-Yarmouk Teaching Hospital, Baghdad. RESULTS: There was a significant increase in blood urea, serum total cholesterol (S.TC), and serum low density lipoprotein (S.LDL) and a significant decreased of serum creatinine (S. creatinine), protein/creatinine ratio, serum total bilirubin, serum albumin, and serum high density lipoprotein, while a highly significant increased (p < 0.001) of CysC levels in children with newly diagnosed NS when compared with control group. A significant positive correlation between CysC level versus systolic blood pressure, body mass index, diastolic blood pressure, S.TC, S. LDL cholesterol (S.LDL-C), S. Total Bilirubin, S. Albumin, S. Total protein, and B. urea, while a significant negative correlation was found between CysC level versus serum low density lipoprotein cholesterol and estimated glomerular filtration rate in children with newly diagnosed NS. CONCLUSION: It may come to the conclusion that CysC can be the best predictor of overall efficacy than creatinine and in the diagnosis of any damage to the kidney in children with NS.

Urinary phthalate metabolites mixture, serum cytokines and renal function in children: A panel study

Epidemiological evidence regarded the relations of phthalates with children's renal function and its underlying mechanism were largely unknown. We conducted a panel study using 287 paired urine-blood samples by repeated measurements of 103 children (4-13 years) across 3 seasons to explore effects of urinary phthalate metabolites on estimated glomerular filtration rate (eGFR) and the potential role of multiple cytokines. We found that mono-ethyl phthalate (MEP), monobutyl phthalate (MBP), mono-benzyl phthalate (MBzP) and mono-n-octyl phthalate (MOP) were significantly associated with eGFR reduction. Compared with the lowest quartile, MBP, MBzP and MEP in the third and fourth quartiles exhibited a graded decrease in eGFR. Meanwhile, weighted quantile sum regression analyses showed an inverse association of metabolites mixture with eGFR, to which MEP, MBzP, MOP were the major contributors. MEP also remained robust in multiple-phthalate model. Age and weight status might modify such relationships with significant interactions. Furthermore, eGFR related phthalate metabolites were associated with increased multiple cytokines, and CCL27, CXCL1 might be potential mediators between MEP and eGFR with mild mediated proportions. Accordingly, urinary phthalate metabolites were related to eGFR reduction in dose-response manner and multiple cytokines elevation, of which CCL27 and CXCL1 might partly mediate phthalate-associated decreased renal function among children.

Cystatin C relates to metabolism in healthy, pubertal adolescents

INTRODUCTION

The cystatin C (CysC) serum level is a marker of glomerular filtration rate and depends on age, gender, and pubertal stage. We hypothesize that CysC might overall reflect energy homeostasis and be regulated by components of the endocrine system and metabolites in pubertal adolescents.

METHODS

Serum CysC levels and further possible effector parameters in 5355 fasting, morning venous blood samples from 2035 healthy participants of the LIFE Child cohort study (age 8 to 18 years) were analyzed. Recruitment started in 2011, with probands followed up once a year. Linear univariate and stepwise multivariate regression analyses were performed.

RESULTS

Annual growth rate, serum levels of thyroid hormones, parathyroid hormone, insulin-like growth factor 1, hemoglobin A1c (HbA1c), uric acid, and alkaline phosphatase show relevant and significant associations with CysC serum concentrations (p <0.001). Furthermore, male probands' CysC correlated with the body mass index and testosterone among other sexual hormones. Multivariate analyses revealed that uric acid and HbA1c are associated variables of CysC independent from gender (p <0.001). In males, alkaline phosphatase (p <0.001) is additionally significantly associated with CysC. Thyroid hormones show significant correlations only in multivariate analyses in females (p <0.001).

CONCLUSIONS

The described associations strongly suggest an impact of children's metabolism on CysC serum levels. These alterations need to be considered in kidney diagnostics using CysC in adolescents. Additionally, further studies are needed on CysC in children.

Creatinine-based GFR-estimating equations in children with overweight and obesity

BACKGROUND

With the increasing prevalence of childhood obesity and related development of chronic kidney disease (CKD), there is a critical need to understand how best to assess kidney function in children with obesity. Since serum creatinine (SCr) is recommended as marker of first choice for GFR estimation, we evaluated and compared creatinine-based GFR equations in children with overweight and obesity.

METHODS

Six hundred children with overweight and obesity (53.5% female; mean age 12.20 ± 3.28 years; mean BMI z-score 3.31 ± 0.75) were included from the Centre for Overweight Adolescent and Children's Healthcare (COACH).

RESULTS

Serum creatinine (SCr), normalized using Q-age polynomials obtained from reference values, results in median and mean SCr/Q value close to "1" for all age groups, and 96.5% of the children have a SCr/Q within the reference band [0.67-1.33], corresponding to the 2.5th and 97.5th percentile. eGFR CKiD (bedside Schwartz equation) and Schwartz-Lyon decreased with age, whereas eGFR EKFC and modified CKD-EPI40 showed no age-dependency, but the distribution of eGFR values was not symmetrical. eGFR CKiD under 25 (CKiDU25) demonstrated no age-dependency but major sex differences were observed. eGFR FAS age, FAS height, and adjusted-creatinine revised Lund-Malmö (LMR18) showed a relatively symmetrical distribution and no age-dependency.

CONCLUSIONS

Serum creatinine (SCr) values of children with overweight and obesity are mostly within the reference range for children. Normalization of SCr using reference Q-age polynomials works very well in this cohort. After evaluation of the different equations, we suggest that FAS age, FAS height, and LMR18 are the preferred creatinine-based GFR-estimating equations in children with overweight and obesity.

CLINICALTRIAL

gov; Registration Number: NCT02091544. A higher resolution version of the Graphical abstract is available as Supplementary information.

Cystatin and Glomerular Filtration Rate in Obese Versus Non-obese Adolescents

Background: Obesity is well known as an independent risk factor for chronic kidney disease. Thus meticulous assessment of renal function is more essential in obese individuals. Glomerular filtration rate (GFR) is commonly estimated based on serum creatinine (Cr).  However, using Cr as marker of kidney function has some limitations and Cystatin C has been reported as an alternative marker. Aim of work: This study was designed to assess renal function using both GFR and cystatin in obese adolescents. Methods: This case-control study enrolled ninety Egyptian adolescents aged between 10 and 18 years old who were divided equally into two groups according to body mass index (obese and non-obese).  Each participant was subjected to full medical history taking, anthropometric measures, and Laboratory investigation including CBC, serum Cr, estimated GFR and cystatin C. Results:  Serum Cr level was significantly higher in obese adolescents compared to non-obese mean value (0.94) and (0.79) resepectively. Also, eGFR based on Cr was significantly lower in obese group compared to controls (73.1) and ( (85.30)respectively. Cystatin C showed non-significant higher levels in obese group versus controls with mean value (2.28) and (1.85)respectively. Cystatin C at Cut-off value of 1.525 and 95% CI showed sensitivity of 47.2% and specificity of 63.9% for evaluation of kidney affection in obese children and adolescences. Conclusion: GFR is affected in obese adolescence with elevation of serum creatinine and unexpected non significant elevation of cystatin C in obese adolescence when compared by control group. Keywords: Cystatin, Creatinine, Pediatric obesity, GFR, renal function.

Relation of glomerular filtration to insulin resistance and related risk factors in obese children

BACKGROUND AND OBJECTIVE

Childhood obesity is associated with later development of significant renal morbidity. We evaluated the impact of the degree of insulin sensitivity on estimated glomerular filtration rate (eGFR) and determined the factors associated with eGFR in obese children. We further tested the relation of eGFR to clinical outcomes such as blood pressure and microalbuminuria.

MATERIALS AND METHODS

We evaluated the relation of whole body insulin sensitivity and estimated glomerular filtration rate (eGFR) across the spectrum of obesity in children and adolescents. eGFR was calculated using the iCARE formula, which has been validated in obese children with varying glucose tolerance.

RESULTS

1080 children and adolescents with overweight and obesity (701 females and 379 males) participated. Insulin sensitivity was a strongly negatively associated with (B = -2.72, p < 0.001) eGFR), even after adjustment for potential confounders. Male sex emerged to be significantly associated with eGFR with boys having greater values than girls (B = 18.82, p < 0.001). Age was a positively associated (B = 2.86, p < 0.001) with eGFR. Whole body and hepatic insulin sensitivity decreased across eGFR quartiles. Adjusted eGFR was tightly positively associated with systolic blood pressure (B = 0.09, p = 0.003) and negatively associated with the presence of microalbuminuria (B = -2.18, p = 0.04).

CONCLUSIONS

eGFR tends to increase with greater degrees of insulin resistance in children and adolescents representing hyperfiltration and is associated with cardiovascular risk factors. Longitudinal studies are needed to determine the natural history of childhood insulin resistance related hyperfiltration in regards to future kidney disease.

Assessment of renal function in obese and overweight children with NGAL and KIM-1 biomarkers

Introduction

Aim and background: the incidence of obesity has increased among children, and obesity has been considered an independent risk factor for chronic kidney disease. We aimed to determine the degree of kidney function impairment by evaluating urine neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) levels. Materials and methods: in total, 15 obese, 26 overweight, and 26 control adolescents aged 10 to 16 years were enrolled into the study. Urine samples were evaluated for NGAL and KIM-1 levels using enzyme-linked immunosorbent assay kits. We investigated the association between obesity and related comorbidities with urinary NGAL and KIM-1 excretion. Results: no significant differences were noted between the obese, overweight, and control groups in urinary NGAL and KIM-1 excretion (p = 0.327 and p = 0.917, respectively). In the obese and overweight groups urinary NGAL levels were 50.39 [30.88-74.22] in females and 26.67 [23.24-45.59] in males (p = 0.013). Also, urinary NGAL levels were increased in obese and overweight adolescents with LDL dyslipidemia at 64.12 [30.98-114.32] as compared to those without LDL dyslipidemia: 39.51 [25.59.56.37] (p = 0.024). Furthermore, a correlation was observed between insulin and homeostasis model assessment of insulin resistance levels with the NGAL/creatinine ratio in the overweight group (r = 0.515; p = 0.008, and r = 0.483; p = 0.014, respectively). Such correlation was not found in the obese group. Conclusion: the effect of obesity on renal function could not be determined in children. A longer exposure may be required for obesity-induced disruption of renal function in children. Renal function may be disrupted by dyslipidemia in obese adolescents. Furthermore, obesity impaired renal function in female adolescents. The normalization of these urinary markers as related to urine creatinine should be discussed.

Microalbuminuria and Serum Cystatin C in Prediction of Early-Renal Insufficiency in Children with Obesity

OBJECTIVE

Serum cystatin-C (SCysC) and microalbuminuria are well-recognized early markers of renal damage. This study aims to assess whether these early markers are elevated in children with obesity and normal serum creatinine (SCr).

METHODS

Pediatric patients diagnosed with obesity were included (n = 105, ages 4-18 y) in this study. The patients were divided into three groups as follows: solely obese, metabolic syndrome and type 2 diabetes. Serum cystatin-C, 24-h microalbuminuria, SCr and glomerular filtration rate (GFR) were evaluated in all patients. All patients were examined with history, physical examination, laboratory analysis and ultrasonography evaluation.

RESULTS

The findings showed that renal function, GFR and SCr levels were normal in all patients. There was microalbuminuria in six patients and SCysC was elevated in eight patients. There were also both elevated SCysC and microalbuminuria in eight patients. Significant elevations of both microalbuminuria and SCysC were detected in cases with type 2 diabetes (p < 0.05).

CONCLUSIONS

The findings suggest that SCysC may have a diagnostic value in early-renal insufficiency. Although there was not any statistically significant difference between groups in GFR, significant elevations for both microalbuminuria and SCysC in patients with type 2 diabetes were detected. This suggests that the risk factors of diabetes may have a direct relation with renal damage. Regarding renal function in type 2 diabetic and obese pediatric patients, microalbuminuria and SCysC may be screened to observe early-renal damage, even in cases with normal GFR and SCr levels.

Personal exposure to fine particulate matter and renal function in children: A panel study

There is a lack of evidence regarding the association of short-term exposure to fine particulate matter (PM_2.5) with renal function in children and its underlying mechanism. We included 105 children aged 4-13 years from a panel study conducted in Wuhan, China with up to 3 repeated visits across 3 seasons from October 9, 2017 to June 1, 2018. We measured personal real-time PM_2.5 exposure concentration continuously for 72 h preceding each round of health examinations that included serum creatinine and cytokines. Linear mixed-effects models were performed to estimate the effects of PM_2.5 on estimated glomerular filtration rate (eGFR) over various lag times, and a mediation analysis was applied for the role of cytokines in association between PM_2.5 and eGFR. Results showed that personal exposure to PM_2.5 was dose-responsive related to decreased eGFR within lag 2 days. The effect was the strongest at lag 0 day with estimation of -1.69% [95% confidence interval (CI): -2.27%, -1.10%] in eGFR by a 10-μg/m³ increase in PM_2.5, and reached peak at lag 3 h, then declined over time. Such inverse relationships were more evident among children aged 4-6 years, or boys or those who lived proximity to major roadways <300 m. Notably, eGFR still held on to decrease even when PM_2.5 was below Class II Chinese ambient air quality standard at lag 0 day. Moreover, the effect of PM_2.5 on eGFR was significantly reduced in children with high and medium levels of serum chemokine ligand 27 (CCL27), but not in those with low CCL27. Furthermore, CCL27 was positively relevant to PM_2.5, and mediated proportion of CCL27 ranged from 3.75% to 6.61% in relations between PM_2.5 and decreased eGFR over various lag times. In summary, short-term PM_2.5 exposure might be dose-responsive associated with reduced eGFR whereby a mechanism partly involving CCL27 among healthy children.

Association of glomerular hyperfiltration with serum chemokine levels and metabolic features in prepubertal children with overweight/obesity

BACKGROUND AND AIMS

Glomerular hyperfiltration (GH) is proposed as one of the earliest events in obesity (OB)-associated renal disease. Children with GH and type-1 diabetes showed increased chemokine levels. Chemokine associations with glomerular filtration rate (GFR) and metabolic features in prepubertal children with overweight (OW)/OB are unknown.

METHODS AND RESULTS

Cross-sectional study. 75 prepubertal children (aged: 9.0 ± 1.7 years) with OW/OB were studied. Clinical and metabolic characteristics (including non-esterified fatty acids, NEFA) and GFR (combined Zappitelli equation) were assessed. GH was defined as GFR >135 ml/min.1.73 m². Serum levels of regulated on activation, normal T cell expressed and secreted (RANTES)/CCL5, interleukin-8 (IL-8)/CXCL8 and monokine-induced by interferon-γ (MIG)/CXCL9 were measured by ELISA. Age- and sex-adjusted correlations and differences were tested. 48% of the cohort was female and 13% were OW, 54% OB and 33% severe OB. Prepubertal children with GH showed lower z-BMI (-12%), NEFA (-26%) and uric acid (-22%) than those without GH (all p < 0.05). Similarly to high sensitivity C-reactive protein (hsCRP), there were no differences in serum chemokines between children with GH or not (all p > 0.05). Adjusted correlations were significant for RANTES and z-BMI (r = 0.26; p < 0.05) and for MIG with z-BMI (r = -0.26; p < 0.05) and with NEFA (r = 0.27; p < 0.05).

CONCLUSION

GH was not associated with higher chemokine levels in prepubertal children with OW/OB. Decreased rather than elevated GFR values were correlated with obesity and worse metabolic profiles. Chemokines levels in children with severe OB suggest a regulation of the immune response. Follow-up studies are needed to address the clinical implications of these findings.