sRANKL and its correlation with metabolic syndrome parameters in children

LMS-based continuous pediatric reference values for soluble receptor activator of nuclear factor kappa B ligand (sRANKL) and osteoprotegerin (OPG) in the HARP cohort

Soluble RANKL (sRANKL) and osteoprotegerin (OPG) are regulators of osteoclast differentiation and activation, but adequate pediatric reference values are lacking. Here we provide LMS (Lambda-Mu-Sigma)-based continuous pediatric reference percentiles for sRANKL, OPG and sRANKL/OPG ratio that will allow calculation of standardized patient z-scores to assess bone modeling in children.

PURPOSE

Soluble receptor activator of nuclear factor kappa B ligand (sRANKL) and osteoprotegerin (OPG) are regulators of osteoclast differentiation and activation and thus bone metabolic turnover in children. Adequate pediatric reference values for their serum/plasma concentrations are lacking. The development of Lambda-Mu-Sigma (LMS)-based continuous reference percentiles for laboratory parameters allow improved data interpretation in clinical practice.

METHODS

A total of 300 children aged 0.1-18 years (166 boys) were enrolled in the HAnnover Reference values for Pediatrics (HARP) study. sRANKL and OPG were assessed by ELISA. LMS-based continuous reference percentiles were generated using RefCurv software.

RESULTS

LMS-based percentiles were established for sRANKL, OPG and sRANKL/OPG ratio, which were all found to be age-dependent. sRANKL and sRANKL/OPG associated with sex. In boys, sRANKL percentiles were highest during infancy, followed by a continuous decline until the age of 7 years and a second peak around age 12-13 years. In girls, a continuous, slow decline of sRANKL percentiles was noticed from infancy onwards until the age of 13 years, followed by a rapid decline until adulthood. OPG percentiles continuously declined from infancy to adulthood. The percentiles for sRANKL/OPG ratio paralleled those of sRANKL. Serum concentrations of sRANKL correlated with OPG and serum phosphate z-scores, while OPG concentrations inversely associated with standardized body weight, BMI, and urinary phosphate to creatinine ratio (each p < 0.05).

CONCLUSION

This is the first report of LMS-based continuous pediatric reference percentiles for sRANKL, OPG and sRANKL/OPG ratio that allows calculation of standardized patient z-scores to assess bone metabolic turnover in children.

Decreased level of soluble receptor activator of nuclear factor-κβ ligand (sRANKL) in overweight and obese children

INTRODUCTION

Childhood obesity contributes to the development of cardiovascular diseases. The molecular pathway - receptor activator of nuclear factor-κβ ligand (RANKL), its receptor RANK and osteoprotegerin (OPG) - takes part not only in bone metabolism but is also involved in the atherosclerosis process. RANKL stimulates osteogenic differentiation and calcification of vascular smooth cells. The associations between the OPG-sRANKL system and various cardiovascular risk factors were displayed. We aimed to evaluate the relationships between serum sRANKL (soluble RANKL) levels and the OPG/sRANKL ratio with cardiometabolic risk factors in overweight and obese children.

MATERIAL AND METHODS

The study included 70 children with overweight and obesity (mean age 13.0 ± 2.8) and 35 age-matched normal weight, healthy peers as a control group. In all patients, anthropometric measurements and laboratory tests were performed. Additionally, an oral glucose tolerance test (OGTT) was made only in overweight and obese children. Atherogenic and insulin resistance indices were calculated.

RESULTS

Overweight and obese children had lower sRANKL levels compared to the control group (median 276.95 vs 325.90, p=0.011), and consequently a higher OPG/sRANKL ratio (0.02 vs 0.01, p = 0.013). The studied children in the lowest quartile of sRANKL levels had higher body weight, Body Mass Index, waist circumference and increased glucose and insulin levels 60 minutes after OGTT and higher uric acid values compared to children in the highest quartile. In multivariable linear regression analysis sRANKL negatively correlated only with uric acid (β = - 0.508, p = 0.041). No association was found for the OPG/sRANKL ratio.

CONCLUSION

Excess fat mass seems to alter the OPG/RANKL ratio mainly by reducing serum sRANKL levels. The correlation between sRANKL and uric acid may suggest a contribution of the OPG-sRANKL system in the cardiometabolic process, but that observation should be confirmed in future studies.

Low Serum Levels of Soluble Receptor Activator of Nuclear Factor κ B Ligand (sRANKL) Are Associated with Metabolic Dysregulation and Predict Long-Term Mortality in Critically Ill Patients

Soluble receptor activator of nuclear factor κ B ligand (sRANKL) is a member of the tumor necrosis factor receptor superfamily, and therefore, involved in various inflammatory processes. The role of sRANKL in the course of bone remodeling via activation of osteoclasts as well as chronic disease progression has been described extensively. However, the potential functional importance of sRANKL in critically ill or septic patients remained unknown. Therefore, we measured sRANKL serum concentrations in 303 critically ill patients, including 203 patients with sepsis and 100 with non-sepsis critical illness. Results were compared to 99 healthy controls. Strikingly, in critically ill patients sRANKL serum levels were significantly decreased at intensive care unit (ICU) admission (p = 0.011) without differences between sepsis and non-sepsis patients. Inline, sRANKL was correlated with markers of metabolic dysregulation, such as pre-existing diabetes and various adipokines (e.g., adiponectin, leptin receptor). Importantly, overall mortality of critically ill patients in a three-year follow-up was significantly associated with decreased sRANKL serum concentrations at ICU admission (p = 0.038). Therefore, our study suggests sRANKL as a biomarker in critically ill patients which is associated with poor prognosis and overall survival beyond ICU stay.

Quantifying RANKL and OPG levels in healthy children: A large cross-sectional analysis

BACKGROUND

There have been new advances in understanding bone remodeling on a molecular level including the RANKL-OPG pathway, leading to advancements in targeted therapeutic intervention. There is however limited data in pediatrics with little known on normative values in healthy children. This is the largest cohort to quantify RANKL, OPG, and RANKL: OPG levels in healthy children as well as study the influence of age, gender, Tanner stage, and BMI in this population.

METHODS

Healthy subjects, 1-21 years of age, were recruited from general pediatric clinics affiliated with CHLA and in collaboration with samples stored from a previously completed study. Healthy children were defined as those with no chronic disease, daily medication, or fractures in the past six months. Free soluble RANKL and OPG levels were quantified using a sandwich ELISA.

RESULTS

Three hundred samples were collected with overall serum concentrations of RANKL, OPG and RANKL: OPG of 0.28 pmol/L, 3.56 pmol/L and 0.08 pmol/L, respectively. Serum RANKL and RANKL: OPG concentrations were significantly different by age (p = 0.0001 and 0.0027, respectively). There was an overall downward trend by age except in the 11-15-year age group where a slight increase was noted. RANKL concentrations were also significantly different between Tanner stages, with highest concentrations seen at Tanner 3 (p = 0.0481), and zBMI (p = 0.001). OPG was inversely correlated with zBMI, but not influenced by gender, age, or Tanner stage.

CONCLUSION

We showed significant difference in RANKL levels by age, Tanner stage, and zBMI. OPG was inversely correlated with zBMI. Insight into circulating levels of RANKL, OPG and RANKL: OPG in healthy children may be a potential tool to better understand disease states in pediatrics. Future studies are needed to evaluate the clinical significance of RANKL and OPG levels for diagnostic and therapeutic purposes in this population.

Effects of Sweet Cherry Polyphenols on Enhanced Osteoclastogenesis Associated With Childhood Obesity

Childhood obesity is associated with the development of severe comorbidities, such as diabetes, cardiovascular diseases, and increased risk of osteopenia/osteoporosis and fractures. The status of low-grade inflammation associated to obesity can be reversed through an enhanced physical activity and by consumption of food enrich of anti-inflammatory compounds, such as omega-3 fatty acids and polyphenols. The aim of this study was to deepen the mechanisms of bone impairment in obese children and adolescents through the evaluation of the osteoclastogenic potential of peripheral blood mononuclear cells (PBMCs), and the assessment of the serum levels of RANKL and osteoprotegerin (OPG). Furthermore, we aimed to evaluate the in vitro effects of polyphenol cherry extracts on osteoclastogenesis, as possible dietary treatment to improve bone health in obese subjects. High RANKL levels were measured in obese with respect to controls (115.48 ± 35.20 pg/ml vs. 87.18 ± 17.82 pg/ml; p < 0.01), while OPG levels were significantly reduced in obese than controls (378.02 ± 61.15 pg/ml vs. 436.75 ± 95.53 pg/ml, respectively, p < 0.01). Lower Ad-SoS- and BTT Z-scores were measured in obese compared to controls (p < 0.05). A significant elevated number of multinucleated TRAP⁺ osteoclasts (OCs) were observed in the un-stimulated cultures of obese subjects compared to the controls. Interestingly, obese subjects displayed a higher percentage of CD14⁺/CD16⁺ than controls. Furthermore, in the mRNA extracts of obese subjects we detected a 2.5- and 2-fold increase of TNFα and RANKL transcripts compared to controls, respectively. Each extract of sweet cherries determined a dose-dependent reduction in the formation of multinucleated TRAP⁺ OCs. Consistently, 24 h treatment of obese PBMCs with sweet cherry extracts from the three cultivars resulted in a significant reduction of the expression of TNFα. In conclusion, the bone impairment in obese children and adolescents is sustained by a spontaneous osteoclastogenesis that can be inhibited in vitro by the polyphenol content of sweet cherries. Thus, our study opens future perspectives for the use of sweet cherry extracts, appropriately formulated as nutraceutical food, as preventive in healthy children and therapeutic in obese ones.