THE FIBROBLAST GROWTH FACTOR-23/KLOTHO AXIS IN HEALTHY AND HOSPITALIZED FOALS

摘要

Hyperphosphatemia, hypocalcemia, increased parathyroid hormone (PTH), and reduced vitamin D metabolite concentrations were recently documented in critically ill foals by our group. However, information on fibroblast growth factor-23 (FGF-23) and klotho, two factors that regulate vitamin D activation and PTH secretion, and their association with calcium, phosphorus, PTH, and vitamin D concentrations in healthy and hospitalized foals is lacking. FGF-23 is released by osteocytes in response to increased1,25(OH)_2D_3, PTH, and phosphorus concentrations. FGF-23 suppresses renal 1a-hydroxylase activity and PTH synthesis. Klotho is secreted by the kidneys and acts as a co-receptor for FGF-23. The goal of this study was to determine the relevance of FGF-23and klotho in calcium, phosphorus, PTH, and vitamin D regulation, including their association with clinical and laboratorial findings, disease severity and outcome in hospitalized foals. We hypothesized that elevated FGF-23 and reduced klotho concentrations will be frequent, associated with calcium and phosphorus dysregulation, PTH and vitamin D metabolite (25(OH)D_3, 1,25(OH)_2D_3) concentrations, severity of illness, and mortality in critically ill foals.