Sclerostin and osteoprotegerin: new markers of chronic kidney disease mediated mineral and bone disease in children

Background Sclerostin and osteoprotegerin (OPG) are new markers of chronic kidney disease (CKD) mediated mineral bone disease (CKD-MBD) which were extensively evaluated in adult population. We aimed to evaluate the associations between serum levels of sclerostin/OPG and parameters of bone turnover and compare the serum levels of sclerostin/OPG in different stages of CKD in children. Methods 70 children with CKD stage 1-5, aged 2-21 years were examined. Serum levels of alkaline phosphatase (ALP), creatinine, total calcium, phosphorus , intact parathyroid hormone (iPTH) and vitamin D were measured. Serum sclerostin and OPG levels were measured in children with different levels of CKD stage and their association with bone turnover parameters were noted. Results We did not observe any significant correlation between serum levels of sclerostin and OPG and stages of CKD. A negative relationship was present between serum sclerostin and 25-OH vitamin D levels. Osteoprotegerin was positively and significantly correlated with ALP but serum sclerostin was negatively correlated with ALP. Conclusion Our study, which includes only children and adolescents with a growing skeleton under uremic conditions and excluding diabetes and atherosclerosis interference, is very valuable. We couldn't find any significant relationship between either sclerostin or OPG levels among different stages of CKD. Also our study demonstared a strong negative relationship between ALP and sclerostin levels and a strong positive relationship between ALP and OPG levels, reminding the importance of ALP levels to predict the bone-mineral status of the children with CKD.

Acquired modification of sphingosine-1-phosphate lyase activity is not related to adrenal insufficiency

Background

Congenital sphingosine-1-phosphate (S1P) lyase deficiency due to biallelic mutations in SGPL1 gene has recently been described in association with primary adrenal insufficiency and steroid-resistant nephrotic syndrome. S1P lyase, on the other hand, is therapeutically inhibited by fingolimod which is an oral drug for relapsing multiple sclerosis (MS). Effects of this treatment on adrenal function has not yet been evaluated. We aimed to test adrenal function of MS patients receiving long-term fingolimod treatment.

Methods

Nineteen patients (14 women) with MS receiving oral fingolimod (Gilenya®, Novartis) therapy were included. Median age was 34.2 years (range; 21.3–44.6 years). Median duration of fingolimod treatment was 32 months (range; 6–52 months) at a dose of 0.5 mg/day. Basal and ACTH-stimulated adrenal steroid measurements were evaluated simultaneously employing LC-MS/MS based steroid panel. Basal steroid concentrations were also compared to that of sex- and age-matched healthy subjects. Cortisol and 11-deoxycortisol, 11-deoxycorticosterone and dehydroepiandrosterone were used to assess glucocorticoid, mineralocorticoid and sex steroid producing pathways, respectively.

Results

Basal ACTH concentrations of the patients were 20.8 pg/mL (6.8–37.8 pg/mL) (normal range; 5–65 pg/mL). There was no significant difference in the basal concentrations of cortisol, 11-deoxycortisol, 11-deoxycorticosterone and dehydroepiandrosterone between patients and controls (p = 0.11, 0.058, 0.74, 0.15; respectively). All patients showed adequate cortisol response to 250 mcg IV ACTH stimulation (243 ng/mL, range; 197–362 ng/mL). There was no significant correlation between duration of fingolimod treatment and basal or ACTH-stimulated cortisol or change in cortisol concentrations during ACTH stimulation test (p = 0.57, 0.66 and 0.21, respectively).

Conclusion

Modification and inhibition of S1P lyase activity by the long-term therapeutic use of fingolimod is not associated with adrenal insufficiency in adult patients with MS. This suggests that S1P lyase has potentially a critical role on adrenal development rather than the function of a fully mature adrenal gland.

Performance Evaluation of a New Coulometric Endpoint Method in Sweat Testing and Its Comparison With Classic Gibson&Cooke and Chloridometer Methods in Cystic Fibrosis

Background: The objective of the study was to assess the diagnostic efficacy of the coulometric endpoint method and compare it with classic Gibson&Cooke and chloridometer methods. Methods: This study is a prospective clinical study comparing two conventional sweat testing methods with the coulometric endpoint method in previously diagnosed cystic fibrosis (CF) patients and a non-CF control group. All individuals underwent two simultaneous sweat collections. One sample of sweat, collected by the CFΔ collector coil system, was analyzed by two methods: the titrimetric Cl^- measurement (Sherwood® Chloridometer 926S, Sherwood Scientific Ltd., Cambridge, UK) and the coulometric endpoint method (CF Δ Collection System®, UTSAT/Turkey); the second sample was collected from the other forearm by the Gibson&Cooke method and the collected sweat was analyzed by manual titration in accordance with the Schales&Schales method. Within-run and between-run imprecisions were evaluated via Cl^- concentrations of 40, 70, and 130 mmol/L samples. Results: One hundred and seventy (60 CF and 110 controls) subjects were included in the study. All three sweat test methods discriminated CF subjects from the healthy individuals. The mean difference between the coulometric endpoint and titrimetric Cl^- measurement methods was -1.5 mmol/L, (95% confidence limits of agreement, ranging from -8.9 to 15.9 mmol/L); the mean difference between manual titration vs. coulometric endpoint methods was 12.8 mmol/L, (95% confidence limits of agreement ranging from -9.7 to 45.3 mmol/L) and the mean difference between the manual titration and titrimetric Cl^- measurement methods was 11.3 mmol/L, (95% confidence limits of agreement ranging from -7.8 to 40.5 mmol/L) based on a Bland-Altman analysis. In the Receiver operating characteristic (ROC) analysis, made on the basis that Cl^- concentration values < 40 mmol/L exclude the CF diagnosis, the coulometric endpoint method resulted in 96.7% sensitivity and 100% specificity for a cut-off value of 58.5 mmol/L (AUC: 0.994; 95% CI = 0.986-1.000; p < 0.001). Conclusions: The coulometric endpoint method can be as reliable as quantitative sweat Cl^- analysis and may be considered as a definitive diagnostic tool for CF.