title: Osteoprotegerin and RANKL serum levels and their relationship with serum ghrelin in children with chronic renal failure and on dialysis.
abstract: BACKGROUND
  Osteoprotegerin (OPG) and receptor activator of the nuclear factor kappaB ligand (RANKL) constitute a complex system of mediators involved in the regulation of bone resorption process. Ghrelin, a growth hormone secretagogue, has been shown to modulate proliferation and differentiation of osteoblasts. The present study was carried out to evaluate the serum concentrations of OPG and sRANKL in children with chronic renal impairment (CRI) and on dialysis, and to establish a possible relationship between their serum levels and that of ghrelin.
  
  
  METHODS
  33 patients including 10 patients with CRI, 12 peritoneal dialysis (PD) and 11 hemodialysis (HD) patients and 22 healthy controls were enrolled into the study. OPG, sRANKL and ghrelin levels were studied with radioimmunoassay.
  
  
  RESULTS
  Serum OPG levels in CRI, PD and HD groups were significantly higher than the healthy controls (p = 0.002, p < 0.001, p < 0.001, respectively) whereas sRANKL levels were significantly lower than the healthy controls (p = 0.03, p = 0.01, p = 0.001, respectively). Ghrelin levels were significantly higher in CRI, PD and HD groups compared to healthy controls (p = 0.001, p < 0.001, p < 0.001, respectively). We observed a negative correlation between the sRANKL and OPG levels (r = -0.27, p = 0.04) as well as between sRANKL and ghrelin levels (r = -0.31, p = 0.02). OPG levels showed a positive correlation with ghrelin levels (r = 0.63, p < 0.001).
  
  
  CONCLUSIONS
  We found a lower RANKL bioactivity index in children with CRI and on dialysis. The mechanism and the role of elevated OPG and low sRANKL in uremia are unclear, but they might partly represent a compensatory mechanism to the negative balance of bone remodeling in renal bone disease in children. Additionally, we demonstrated for the first time that ghrelin and the RANKL/OPG system have a close relationship in CRF. Therefore, ghrelin may be of importance in mediating the effects of the RANKL/OPG system in renal bone disease.
authors.affiliation: Department of Pediatric Nephrology, Ondokuz Mayis University, Samsun, Turkey. ozanozkaya@yahoo.com
authors.forename: Ozan
authors.initials: O
authors.lastname: Ozkaya
authors.forename: Necla
authors.initials: N
authors.lastname: Buyan
authors.forename: Aysun
authors.initials: A
authors.lastname: Bideci
authors.forename: Sevim
authors.initials: S
authors.lastname: Gonen
authors.forename: Erol
authors.initials: E
authors.lastname: Ortac
authors.forename: Kibriya
authors.initials: K
authors.lastname: Fidan
authors.forename: Peyami
authors.initials: P
authors.lastname: Cinaz
authors.forename: O
authors.initials: O
authors.lastname: Söylemezoğlu
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D054439:Ghrelin; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy*; D008297:Male; D053244:Osteoprotegerin / Q000097:blood*; D036361:Peptide Hormones / Q000097:blood*; D011379:Prognosis; D053245:RANK Ligand / Q000097:blood*; D006435:Renal Dialysis; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013223:Statistics as Topic
chemical_list: D054439:Ghrelin; D053244:Osteoprotegerin; D036361:Peptide Hormones; D053245:RANK Ligand; C505688:TNFSF11 protein, human