Serum sclerostin in acute kidney injury patients

Many of the mineral metabolite abnormalities encountered in chronic kidney disease (CKD) patients were found also associated with acute kidney injury (AKI). In the last decade, sclerostin was found to intimately affect bone mineral metabolism in CKD patients. Nothing is known about sclerostin in AKI.

We looked for serum level of sclerostin in AKI patients in comparison to normal control subjects and if there is an impact on metabolic derangement, endothelial function or clinical outcome.

This is a cross sectional case control observational study of 219 AKI cases (group I) beside 219 age matched normal control subjects (group II). All cases of group I were in the intensive care because of sepsis; 86 had acute on CKD (group Ib), while 133 had de novo AKI (group Ia). All studied subjects underwent estimation of serum sclerostin, parathyroid hormone (PTH), 25 hydroxy vitamin D (25 OH vit D), fibroblast growth factor 23 (FGF23), C-reactive protein (CRP), interleukin 6 (IL6), Homeostatic Model Assessment for Insulin Resistance (Homa IR), beside the routine CBC, kidney and liver function tests, serum calcium, and phosphorus, and flow mediated vasodilation of brachial artery (FMD). Follow-up of group I cases was done till they recovered or passed away.

Serum sclerostin, PTH, FGF23, phosphorus, CRP, IL6, HOMA IR, creatinine, urea, uric acid, ALT, AST and white blood cell count (WBC) were significantly higher while serum calcium, 25 OH vit D, hemoglobin, platelet count and FMD were significantly lower in group I compared to group II (P<0.001 in all). On the other hand, there was no significant difference in serum sclerostin, PTH, FGfF23, 25 OH vit D, CRP, IL6, Homa IR and FMD between group Ia and Ib. Survivors were younger in age (median 55.5 vs. 60 years, P<0.04), had lower AST (30.5 vs. 58 units, P<0.001), had higher platelet count (206 vs 162×10⁹/L, P<0.001), otherwise, there was no significant difference in any of the other parameters between survivors and patients that were lost. Serum sclerostin had strong correlation with FGF23 in group I (r=0.99, P<0.001) and group II (r=1, P<0.001). Homa IR had positive correlation with serum sclerostin (r=0.148, P=0.014) and serum FGF23 (r=0.142, P=0.018) in group I.

Sclerostin is intimately related to FGF23. Sclerostin level increases in AKI patients. Both sclerostin and FGF23 might increase insulin resistance but have no impact on FMD. Neither sclerostin nor FGF23 interfere with AKI outcome.