Study of Serum Fibroblast Growth Factor 23 as a Predictor of Endothelial Dysfunction among Egyptian Patients with Diabetic Kidney Disease

Endothelial dysfunction in patients with diabetic nephropathy is caused by nontraditional factors in addition to common risk factors (e.g., hypertension) in people with normal kidney function. These nontraditional factors include factors involved in mineral bone disease in these patients. One of these factors is fibroblast growth factor 23 (FGF-23). We aimed to evaluate the relationship between flow-mediated dilatation (FMD) as a measure of endothelial dysfunction and FGF-23. This was a cross-sectional observational study that was conducted on 100 diabetic patients (Group I: 50 patients with nephropathy; Group II: 50 patients without nephropathy) and 50 healthy volunteers (Group III). Serum levels of intact FGF-23, interleukin-6, intact parathyroid hormone, and 25-hydroxyvitamin D (25-(OH)Vit D); estimated insulin resistance; and FMD were evaluated. FGF-23 was significantly higher in Group I (median: 101 pg/mL) and Group II (median: 101 pg/mL) than in Group III (median: 4 pg/mL) (P <0.001), but FGF-23 was not significantly different between Groups I and II. A significant positive correlation was found between serum levels of FGF-23 and phosphorus in Group I. A significant negative correlation was found between serum levels of FGF-23 and 25-(OH)Vit D in Group II. However, FGF-23 failed to show a significant correlation with FMD in patients with diabetic nephropathy. Our data suggest another factor that rises earlier than FGF-23 in diabetic nephropathy and causes endothelial dysfunction.