Cystatin C, cardiometabolic risk, and body composition in severely obese children

New Markers of Early Kidney Damage in Children and Adolescents with Simple Obesity

The impact of obesity on kidney injury and the development of chronic kidney disease (CKD) is well documented. Unfortunately, the early stages of CKD are asymptomatic, leading to a delayed diagnosis and a worse prognosis. There is a need for more sensitive indicators of kidney damage than those currently used. We aimed to assess the usefulness of serum t-CAF, urinary netrin-1, α-GST, π-GST, calbindin, and calprotectin as biomarkers of early kidney damage in obese children and to investigate the relationship between these indicators and the degree of obesity. A total of 125 simple obese, normoalbuminuric children and 33 non-obese children as controls were selected. Patients were divided into 2 subgroups according to SDS BMI (I: 2 ≤ 4, II: >4). Serum t-CAF was significantly higher in the obese group compared to the controls, as were urinary α-GST, netrin-1, π-GST, and calprotectin. No difference was found between the two obese groups. In normoalbuminuric obese children and adolescents without significant metabolic disorders, serum t-CAF may be a new biomarker for the early detection of renal dysfunction, and urinary netrin-1, α-GST, π-GST, and calprotectin may be better indicators for the detection of early tubular damage, independent of the severity of obesity.

Serum Cystatin C Levels Are Associated With Obesity in Adolescents Aged 14-17 Years

BACKGROUND

The association between serum cystatin C levels and obesity has not been fully explored in adolescents. This study aimed to explore the association between serum cystatin C levels and obesity in adolescents of different sexes.

METHODS

We conducted a cross-sectional study including 481 adolescents aged 14-17 years. Cystatin C level was measured by immunoassay. Health examinations data, biochemical parameters, and questionnaire information were collected. The restricted cubic spline model analyzed the association between cystatin C levels and obesity in boys and girls.

RESULTS

Boys exhibited significantly higher cystatin C levels than girls, with a mean level of 0.97 ± 0.10 mg/L in boys and 0.86 ± 0.09 mg/L in girls (P < 0.001). The restricted cubic spline model suggested that low or high cystatin C levels were associated with an increased risk of obesity in boys, whereas only higher cystatin C levels were associated with an increased risk of obesity in girls.

CONCLUSIONS

A U-shaped correlation was observed between serum cystatin C levels and the risk of obesity in boys. However, in girls, the risk of obesity showed a trend of initially increase and then decrease with increasing cystatin C levels. Longitudinal studies should be conducted to further investigate the diagnostic potential of cystatin C in the progression of early obesity in adolescents of different sexes.

Cystatin C in adipose tissue and stimulation of its production by growth hormone and triiodothyronine in 3T3-L1 cells

Cystatin C (CysC) is a marker for estimation of glomerular filtration rate (GFR). CysC levels may depend not only on clearance/GFR but possibly also on changes in production. Our studies on tissue distribution of CysC protein in mice showed that adipose tissue expresses significant amounts of CysC, suggesting that adipocytes could contribute to circulating CysC levels in vivo. As growth hormone (GH) and triiodothyronine (T₃) increase both GFR and CysC (increased in acromegaly and hyperthyroidism) in vivo, we studied whether they could increase CysC production in 3T3-L1 adipocytes in vitro. CysC accumulated in culture media of 3T3-L1 adipocytes in a time-dependent fashion. GH and T₃ both (10 nmol/l) increased accumulation of CysC, to 373 ± 14 and 422 ± 20, respectively, vs 298 ± 10 ng per well over 4 days in controls. Thus, GH and T₃ enhance the production of CysC by adipocytes in vitro.

The association between creatinine versus cystatin C-based eGFR and cardiovascular risk in children with chronic kidney disease using a modified PDAY risk score

BACKGROUND

Children with chronic kidney disease (CKD) have a high prevalence of cardiovascular disease (CVD) risk factors which may contribute to the development of cardiovascular events in adulthood. Among adults with CKD, cystatin C-based estimates of glomerular filtration rate (eGFR) demonstrate a stronger predictive value for cardiovascular events than creatinine-based eGFR. The PDAY (Pathobiological Determinants of Atherosclerosis in Youth) risk score is a validated tool used to estimate the probability of advanced coronary atherosclerotic lesions in young adults.

OBJECTIVE

To assess the association between cystatin C-based versus creatinine-based eGFR (eGFR cystatin C and eGFR creatinine, respectively) and cardiovascular risk using a modified PDAY risk score as a proxy for CVD in children and young adults.

METHODS

We performed a cross-sectional study of 71 participants with CKD [median age 15.5 years; inter-quartile range (IQR) 13, 17], and 33 healthy controls (median age 15.1 years; IQR 13, 17). eGFR was calculated using age-appropriate creatinine- and cystatin C-based formulas. Median eGFR creatinine and eGFR cystatin C for CKD participants were 50 (IQR 30, 75) and 53 (32, 74) mL/min/1.73 m², respectively. For the healthy controls, median eGFR creatinine and eGFR cystatin were 112 (IQR 85, 128) and 106 mL/min/1.73m² (95, 123) mL/min/1.73 m², respectively. A modified PDAY risk score was calculated based on sex, age, serum lipoprotein concentrations, obesity, smoking status, hypertension, and hyperglycemia.

RESULTS

Modified PDAY scores ranged from -2 to 20. The Spearman's correlations of eGFR creatinine and eGFR cystatin C with coronary artery PDAY scores were -0.23 (p = 0.02) and -0.28 (p = 0.004), respectively. Ordinal logistic regression also showed a similar association of higher eGFR creatinine and higher eGFR cystatin C with lower PDAY scores. When stratified by age <18 or ≥18 years, the correlations of eGFR creatinine and eGFR cystatin C with PDAY score were modest and similar in children [-0.29 (p = 0.008) vs. -0.32 (p = 0.004), respectively]. Despite a smaller sample size, the correlation in adults was stronger for eGFR cystatin C (-0.57; p = 0.006) than for eGFR creatinine (-0.40; p = 0.07).

CONCLUSIONS

Overall, the correlation between cystatin C- or creatinine-based eGFR with PDAY risk score was similar in children. Further studies in children with CKD should explore the association between cystatin C and cardiovascular risk.

Childhood Estimates of Glomerular Filtration Rate Based on Creatinine and Cystatin C: Importance of Body Composition

BACKGROUND

Creatinine and cystatin C concentrations are commonly used to estimate glomerular filtration rate (eGFR) in clinical practice and epidemiological studies. To estimate the influence of different body composition measures on eGFR from creatinine and cystatin C blood concentrations, we compared the associations of different anthropometric and body composition measures with eGFR derived from creatinine (eGFRcreat) and cystatin C (eGFRcystC) blood concentrations.

METHODS

In a population-based cohort study among 4,305 children aged 6.0 years (95% range 5.7-8.0), we measured weight and height and calculated body mass index (BMI) and body surface area (BSA), and lean and fat mass using dual-energy X-ray absorptiometry. At the same age, we measured creatinine and cystatin C blood concentrations and estimated the GFR.

RESULTS

Correlation between eGFR based on creatinine and cystatin C concentrations was r = 0.40 (p value <0.01). Higher BMI was associated with lower eGFRcystC but not with eGFRcreat. Higher BSA was associated with higher eGFRcreat and lower eGFRcystC (p value <0.05). Lean and fat mass percentages were associated with eGFRcreat but not with eGFRcystC.

CONCLUSION

Our findings suggest that both eGFRcreat and eGFRcystC are influenced by BMI and BSA. eGFRcreat is more strongly influenced by body composition than eGFRcystC.

Cardiovascular metabolic risk factors and glomerular filtration rate: a rural Chinese population study

METHODS

A total of 2426 study subjects from rural China aged 35 years and above (934 men and 1492 women) were enrolled in a cross-sectional survey. The eGFR calculation was based on the Modification of Diet in Renal Disease (MDRD) equation. The strength of the association between cardiovascular metabolic risk factors and eGFR was analyzed using a linear regression model.

RESULTS

Cardiovascular metabolic risk factors, including age, body weight, waist circumference, fasting plasma glucose (FPG), creatinine (Cr), high-density lipoprotein-cholesterol (HDL-C), total cholesterol (TC), triglyceride (TG), systolic pressure, and diastolic pressure, were associated with eGFR. Additionally, the eGFR level gradually decreased and showed a linear trend with the increase in metabolic syndrome risk factors.

CONCLUSION

Metabolic risk factors are correlated with a reduction in renal function and CKD.

Decreased renal function in overweight and obese prepubertal children

BACKGROUND

Obesity is a potentially modifiable risk factor for the development and progression of kidney disease, both in adults and children. We aim to study the association of obesity and renal function in children, by comparing estimated glomerular filtration rate (eGFR) in nonoverweight and overweight/obese children. Secondarily, we aim to evaluate the accuracy of equations on eGFR estimation when compared to 24-h urinary creatinine clearance (CrCl).

METHODS

Cross-sectional study of 313 children aged 8-9 y, followed in the birth cohort Generation XXI (Portugal). Creatinine and cystatin C, GFR estimated by several formulas and CrCl were compared in 163 nonoverweight and 150 overweight/obese, according to World Health Organization growth reference.

RESULTS

Overweight/obese children had significantly lower eGFR, estimated by all methods, except for CrCl and revised Schwartz formula. Despite all children having renal function in the normal range, eGFR decreased significantly with BMI z-score (differences ranging from -4.3 to -1.1 ml/min/1.73 m(2) per standard deviation of BMI). The Zappitelli combined formula presented the closest performance to CrCl, with higher correlation coefficients and higher accuracy values.

CONCLUSION

Young prepubertal children with overweight/obesity already present significantly lower GFR estimations that likely represent some degree of renal impairment associated with the complex deleterious effects of adiposity.

Perioperative outcomes of adolescents undergoing bariatric surgery: the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study

IMPORTANCE

Severe obesity in childhood is a major health problem with few effective treatments. Weight-loss surgery (WLS) is being used to treat severely obese adolescents, although with very limited data regarding surgical safety for currently used, minimally invasive procedures.

OBJECTIVE

To assess the preoperative clinical characteristics and perioperative safety outcomes of severely obese adolescents undergoing WLS.

DESIGN, SETTING, AND PARTICIPANTS

This prospective, multisite observational study enrolled patients from February 28, 2007, through December 30, 2011. Consecutive patients aged 19 years or younger who were approved to undergo WLS (n = 277) were offered enrollment into the study at 5 academic referral centers in the United States; 13 declined participation and 22 did not undergo surgery after enrollment, thus the final analysis cohort consisted of 242 individuals. There were no withdrawals.

MAIN OUTCOMES AND MEASURES

This analysis examined preoperative anthropometrics, comorbid conditions, and major and minor complications occurring within 30 days of operation. All data were collected in a standardized fashion. Reoperations and hospital readmissions were adjudicated by independent reviewers to assess relatedness to the WLS procedure.

RESULTS

The mean (SD) age of participants was 17.1 (1.6) years and the median body mass index (calculated as weight in kilograms divided by height in meters squared) was 50.5. Fifty-one percent demonstrated 4 or more major comorbid conditions. Laparoscopic Roux-en-Y gastric bypass, vertical sleeve gastrectomy, and adjustable gastric banding were performed in 66%, 28%, and 6% of patients, respectively. There were no deaths during the initial hospitalization or within 30 days of operation; major complications (eg, reoperation) were seen in 19 patients (8%). Minor complications (eg, readmission for dehydration) were noted in 36 patients (15%). All reoperations and 85% of readmissions were related to WLS.

CONCLUSIONS AND RELEVANCE

In this series, adolescents with severe obesity presented with abundant comorbid conditions. We observed a favorable short-term complication profile, supporting the early postoperative safety of WLS in select adolescents. Further longitudinal study of this cohort will permit accurate assessment of long-term outcomes for adolescents undergoing bariatric surgery.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00474318.

Retinol-binding protein 4 levels are associated with measures of liver and renal function and oxidant/antioxidant status in obese children

Serum retinol-binding protein 4 (RBP4) has been proposed as a metabolic risk factor in obesity. We found that RBP4 levels also were associated with liver enzymes and cystatin C. Oxidant stress is a significant feature in obese children with greater values of RBP4 that can mediate the development of comorbidities.

Cystatin C in children on chronic hemodialysis

BACKGROUND

Cystatin C (CyC) concentration has been suggested as a marker of middle-molecule accumulation, hemodialysis (HD) adequacy and for estimating residual renal function (RRF), but it has not been studied in pediatric HD. High CyC is associated with increased cardiovascular disease (CVD). We investigated CyC kinetics and the effect of RRF on CyC in a pediatric HD population.

METHODS

A total of 21 HD sessions and 20 interdialytic periods were analyzed in seven patients, age 5-19 years, of whom four were anuric (A) and three were non-anuric (NA). CyC was measured before (preHD) and after (postHD) three standard HD sessions in 1 week and prior to the first session of the following week.

RESULTS

We found no difference (p=0.67) in CyC concentration between preHD CyC (9.85 ± 2.15 mg/l; A vs. NA, p=0.37) and postHD CyC (10.04 ± 2.83 mg/l; A vs NA, p=0.28). The weekly average preHD CyC median concentration was 10.14 mg/l (A vs. NA, p=0.87) and correlated with age (r=0.808, p=0.03) and height measurement (r=0.799, p=0.03), but not with RRF, single-pool Kt/V, ultrafiltration, HD duration or blood liters processed.

CONCLUSIONS

Cystatin C is very elevated in children on HD. It does not rise between HD sessions, is not removed by standard HD and remains at steady state; therefore, elimination is extrarenal. Low RRF does not affect CyC elimination. CyC increases with age and height. If a high CyC concentration can be proven to have a causative role in the development of CVD, routine intensified HD regimens in children may be indicated for its removal.