Abstract
Background: Patients with transfusion-dependent thalassemia (TDT) show
disorders in calcium metabolism. The α-Klotho protein is predominantly expressed in
tissues that are involved in calcium homeostasis, and lowered levels are associated with
bone disease. The aim of the study is to examine the associations between low α-Klotho
status and calcium metabolism in relation to iron status in children with TDT.
Methods: Calcium, α-Klotho, parathyroid hormone (PTH), calcyphosin, vitamin D3,
phosphorous, fibroblast growth factor receptor 2 (FGFR2), as well as iron and erythron
biomarkers were measured in 60 children with TDT and 30 healthy control children.
Results: A meaningful part of TDT patients showed lowered α-Klotho levels, and those
children also showed low serum total and ionized calcium concentrations. TDT patients
showed increased PTH, FGFR2, and calcyphosin and lowered vitamin D3 as compared
with healthy children. The α-Klotho levels were significantly correlated with total and
ionized calcium (positively) and with iron overload and transfusions biomarkers
(inversely). Partial Least Squares path analysis showed that 40.1% of the variance in
serum total calcium could be explained by the regression on α-Klotho, vitamin D3 (both
positively), and calcyphosin (inversely) and that the effects of the latter are mediated by
iron overload and the number of blood transfusions.
Conclusion: In conclusion, the iron overload in TDT and its consequences may induce
lowered levels of α-Klotho which in turn may lead to lower calcium thereby explaining at
least in part the effects of TDT on bone metabolism including spontaneous pathological
fractures, osteoporosis, osteopenia, and skeletal deformities.
Keywords:
Calcium, α-Klotho, inflammation, oxidative stress, antioxidants, biomarkers.
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