The effect of one year lifestyle intervention on eGFR in children and adolescents with overweight, obesity and morbid obesity

The evaluation of kidney function estimation during lifestyle intervention in children with overweight and obesity

BACKGROUND

Children with overweight and obesity are at risk for developing chronic kidney disease (CKD). During lifestyle adjustment, the first step in the treatment of childhood obesity, body proportions are likely to change. The aim of this study was to examine how lifestyle intervention affects creatinine-based kidney function estimation in children with overweight and obesity.

METHODS

This longitudinal lifestyle intervention study included 614 children with overweight and obesity (mean age 12.17 ± 3.28 years, 53.6% female, mean BMI z-score 3.32 ± 0.75). Loss to follow-up was present: 305, 146, 70, 26, and 10 children were included after 1, 2, 3, 4, and 5 (about yearly) follow-up visits, respectively. Serum creatinine (SCr) was rescaled using Q-age and Q-height polynomials.

RESULTS

At baseline, 95-97% of the children had a SCr/Q-height and SCr/Q-age in the normal reference range [0.67-1.33]. SCr/Q significantly increased each (about yearly) follow-up visit, and linear mixed regression analyses demonstrated slopes between 0.01 and 0.04 (corresponding with eGFR FAS reduction of 1.1-4.1 mL/min/1.73 m2) per visit. BMI z-score reduced in both sexes and this reduction was significantly higher in males. No correlation between change in rescaled SCr and BMI z-score reduction could be demonstrated.

CONCLUSIONS

Rescaled serum creatinine (SCr/Q) slightly increases during multidiscipline lifestyle intervention in this cohort of children with overweight and obesity. This effect seems to be independent from change in BMI z-score. Whether this minor decrease in estimated kidney function has clinical consequences in the long term remains to be seen in trials with a longer follow-up period.

CLINICAL TRIAL REGISTRATION

ClinicalTrial.gov; Registration Number: NCT02091544.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Ambient particulate matter exposure plus a high-fat diet exacerbate renal injury by activating the NLRP3 inflammasome and TGF-β1/Smad2 signaling pathway in mice

BACKGROUND

Chronic kidney disease (CKD) is a public health problem of which the prevalence is increasing worldwide. Several studies have reported that ambient particulate matter (PM) causes kidney injury, which may be related to the risk of CKD. However, the underlying molecular mechanisms have not been fully clarified. In addition, whether a high-fat diet (HFD) could exacerbate ambient PM-induced nephrotoxicity has not been evaluated. This study aimed to investigate the combined effect of ambient PM and a HFD on renal injury.

METHODS AND RESULTS

Male C57BL/6 J mice were fed either a normal diet or a HFD and exposed to filtered air (FA) or particulate matter (PM) for 18 weeks. In the present study, we observed that renal function changed (serum blood urea nitrogen and serum creatinine), and exposure to PM and a HFD caused a synergistic effect on renal injury. Histopathological analysis showed that PM exposure induced renal fibrosis in mice, and combined exposure to PM and a HFD exacerbated these adverse effects. Moreover, ambient PM exposure activated the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome and increased the inflammatory response, as indicated by the increases in interleukin-1β, interleukin-6 and tumor necrosis factor-α in the serum and kidney, as well as the upregulation of specific renal fibrosis-related markers (transforming growth factor-β1 and p-Smad2) in the kidney tissues of mice. Furthermore, combined exposure to PM and a HFD augmented these changes in the kidney. In vitro, inhibition of the NLRP3 inflammasome by MCC950 (an inhibitor of NLRP3) reduced the levels of proinflammatory cytokines and the expression of transforming growth factor-β1 and p-Smad2 in HK-2 cells.

CONCLUSION

Taken together, our data indicated that PM exposure caused renal inflammation and induced profibrotic effects on the kidney, and combined exposure to ambient PM and a HFD exacerbated renal injury, which may involve activation of the NLRP3 inflammasome and the TGF-β1/Smad2 signaling pathway.

Glomerular hyperfiltration in morbid obesity: Role of the inflammasome signalling

AIM

Obesity is associated with glomerular hyperfiltration which may precede the development of overt renal damage. Few studies evaluated the link between inflammasome signalling and hyperfiltration. The aim is to evaluate the relationship between IL1-β/Caspase-1, insulin sensitivity and hyperfiltration in subjects with severe obesity, before and after weight loss.

METHODS

Forty-six patients with BMI > 35 kg/m² , without type-2-diabetes or hypertension, were evaluated at baseline and 6 months after bariatric surgery with oral glucose tollerance test, bioimpedance analysis and blood tests. The eGFR was calculated according to EPIcr-cys formula and insulin sensitivity by Oral Glucose Insulin Sensitivity. IL-1β/Caspase-1 were measured with the ELISA-kit. HF was defined as eGFR ≥ 140 ml/min (non-indexed for BSA).

RESULTS

Sixteen subjects at baseline had hyperfiltration, with a higher insulin resistance, BMI, lean mass and plasma levels of IL-1β/Caspase-1. After surgery, there was a reduction in BMI and improvement in insulin resistance in all patients. However, in 8 of 16 patients hyperfiltration persisted and IL-1β/Caspase-1 levels did not decrease (3.22 ± 0.79 vs. 3.13 ± 1.03 and 23.7 ± 12.1 vs. 20.6 ± 9.1, pre vs. post, pg/ml), while cytokines normalized in all the other patients in parallel with the eGFR. In a logistic regression model, correcting for the main covariates, lean mass and IL-1β before surgery (p = .01 and p = .03, respectively), were the only predictors of hyperfiltration.

CONCLUSION

Weight loss is effective in reducing hyperfiltration in most, but not all patients. Hyperfiltration remains unchanged in subjects who do not have a reduction in IL-1β/Caspase-1, suggesting a pathogenetic role of the inflammasome signalling in the early stages of nephropathy.

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.

Obesity Facts and Their Influence on Renal Function Across the Life Span

Obesity is a chronic disease, with a rapidly increasing prevalence worldwide. Body mass index (BMI) provides the most useful population-level measure of overweight and obesity. For adults, overweight is defined as a BMI (Kg/m²) ≥ 25, and obesity as a BMI ≥ 30, for non-Asians and ≥ 27.5 for Asians. Abdominal obesity can be defined as a waist circumference equal to or higher than 102 cm for men and ≥88 cm for women. The definition of children and adolescents BMI changes with age and sex. Obesity may be exogenous or endogenous obesity, the latter is multifactorial and predominantly manifested during childhood. Presently, overweight and obesity are linked to more deaths worldwide than underweight. The total kidney glomerular filtration rate (GFR) is determined by the sum of nephrons and the GFR within each nephron or single nephron GFR. In clinical practice, GFR is more frequently calculated by GFR estimating equations based upon the plasma levels of creatinine, cystatin C, or both. The measured value of plasma creatinine is strongly influenced by non-GFR factors, by its tubular and gastrointestinal secretion, and by the problems associated with the lack of standardization of creatinine's laboratory assay discrediting it as an ideal GFR biomarker. Unlike creatinine, cystatin C plasma levels are mainly determined by GFR. Obesity may affect the kidney, via development of systemic arterial hypertension and/or diabetes mellitus, or directly, by ectopic accumulation of adipose tissue in the kidney. As obesity is a clinical condition associated with altered body composition, creatinine may not be the ideal biomarker for GFR measurement in obese individuals.

Obesity Related Glomerulopathy in Adolescent Women: The Effect of Body Surface Area

Background

Adolescent obesity, a risk factor for cardiorenal morbidity in adulthood, has reached epidemic proportions. Obesity-related glomerulopathy (ORG) has an early reversible stage of hyperfiltration. Age-appropriate formulae for eGFR, which are standardized to ideal body surface area (BSA) and provide assessment of kidney function in ml/min/1.73 m², may underestimate prevalence of early ORG. We investigated whether adjusting eGFR to actual BSA more readily identifies early ORG.

Methods

We studied a cohort of 22,417 young individuals, aged 12-21 years, from a New York metropolitan multi-institutional electronic health records clinical database. eGFR was calculated in two ways: BSA-standardized eGFR, and absolute eGFR. Hyperfiltration was defined above a threshold of 135 ml/min per 1.73 m² or 135 ml/min, respectively. The prevalence of hyperfiltration according to each formula was assessed in parallel to creatinine clearance.

Results

Serum creatinine values and hyperfiltration prevalence according to BSA-standardized eGFR were similar, 13%-15%, across body mass index (BMI) groups. The prevalence of hyperfiltration determined by absolute eGFR differed across BMI groups: underweight, 2%; normal weight, 6%; overweight, 17%; and obese, 31%. This trend paralleled the rise in creatinine clearance across BMI groups.

Conclusions

Absolute eGFR more readily identifies early ORG than the currently used formulae, which are adjusted to a standardized BSA and are not representative of current population BMI measures. Using absolute eGFR in clinical practice and research may improve the ability to identify, intervene, and reverse early ORG, which has great importance with increasing obesity rates.

Glomerular Hyperfiltration Is Associated with Liver Disease Severity in Children with Nonalcoholic Fatty Liver Disease

OBJECTIVES

To determine the prevalence of renal impairment in a large cohort of youths with histologically confirmed nonalcoholic fatty liver disease (NAFLD), and to determine its association with liver disease severity.

STUDY DESIGN

Clinical, laboratory, and histology data were collected retrospectively in a pediatric cohort with biopsy-confirmed NAFLD at a tertiary care center between 2010 and 2017. Histological NAFLD severity was scored using validated criteria. Glomerular filtration rate (GFR) was calculated and categorized as low (<90 mL/min/1.73 m²), normal (90-136 mL/min/1.73 m²), or high (>136 mL/min/1.73 m²). Univariate and multivariate modeling were used to determine differences between the GFR groups and to control for confounders.

RESULTS

The cohort comprised 179 patients (82% non-Hispanic; median age; 14 years; IQR, 12-16 years). One-third of the patients had abnormal renal function, including 36 (20%) with glomerular hyperfiltration and 26 (15%) with low GFR. In multivariable logistic regression, compared with normal GFR, hyperfiltration was independently associated with higher NAFLD activity score (aOR, 2.96; 95% CI, 1.49-5.87; P = .002), after adjusting for age, sex, ethnicity, obesity severity, presence of type 2 diabetes mellitus, and medications.

CONCLUSIONS

In this large cohort with histologically confirmed NAFLD, renal impairment was highly prevalent and associated with liver disease severity, independent of obesity severity. Screening patients with confirmed NAFLD for renal complication is recommended.

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.