Vitamin D and Hypoxia-Inducible Factor (HIF-1α) Serum Levels as Markers for Progression of Nephropathy in Type 2 Diabetic Patients.

Background: Vitamin D is a locally acting hormone, which plays a major role in skeletal health. Previous studies reported an important role of vitamin D in modulation of inflammatory response. We aimed to investigate the role of vitamin D deficiency and hypoxia-inducible factor (HIF-1α) as markers for the progression of diabetic nephropathy in Saudi patients with type 2 diabetes mellitus (T2DM).

Methods: We included 174 Saudi patients with T2DM in addition to 60 healthy control subjects. Patients were classified according to urinary Albumin to Creatinine Ratio (ACR) into three groups: Group AI: ACR < 30 µg/mg, Group AII: ACR levels of 30 - 300 µg/mg and Group AIII: ACR > 300 µg/mg. We estimated fasting blood glucose, HbA1c, lipid profile, serum creatinine, hemoglobin concentration (Hb), estimated glomerular filtration rate (eGFR), urine albumin/creatinine ratio, serum 25 hydroxyvitamin D, calcium, parathyroid hormone (PTH), tumor necrosis factor (TNF-α), C- reactive protein (CRP), and hypoxia-inducible factor (HIF-1α).

Results: There was a significant difference among studied groups regarding serum levels of vitamin D, calcium, PTH, TNF-α, CRP, and HIF-1α levels. The level of vitamin D was lower in diabetic patients in comparison to the controls and was significantly related to the severity of renal nephropathy as indicated by the level of albumin in urine. Moreover, vitamin D levels showed significant negative correlation with the inflammatory markers: TNF-α, CRP, and HIF-1α levels.

Conclusions: Vitamin D deficiency and elevated HIF-1α serum levels showed a significant correlation to progression of nephropathy in Saudi patients with T2DM.