The effect of vitamin-D on the diabetic rethinopathy

R. Selvinaz Erol¹, S. Sayid Zuhur², F.Yener Ozturk¹, Esra Cil Şen¹, Ayşegul Mavi Yıldız³, M. Masum Canat¹, Dilek Guven⁴, Yüksel Altunta S¹, M. Kazim Erol⁵

¹University of Health Sciences, Sisli Hamidiye Etfal Training and Research Hospital, Department of Endocrinology and Metabolism, Turkey - ²Department of Endocrinology and Metabolism, Faculty of Medicine, Namik Kemal University, Tekirdag, Turkey - ³Bursa Retina Eye Hospital, Department of Ophthalmology, Bursa, Turkey ^{- 4}University of Health Sciences, Sisli Hamidiye Etfal Training and Research Hospital, Department of Ophthalmology, Turkey - ⁵University of Health Sciences, Antalya Trainning and Research Hospital, Antalya, Turkey

Background: To determine the relationship between grade of diabetic retinopathy and serum vitamin D levels in diabetic patients.

Methods: The study included a total of 173 diabetic patients consisting of patients without retinopathy ( n=67), patients with non proliferative diabetic retinopathy (NPDRP group n=47), patients with proliferative diabetic retinopathy (PDRP group n=59). Age and sex-matched 55 healthy subjects was taken as a control group. Patients with type 1 DM, those taking vitamin D, multivitamin including vitamin D, drug affecting vitamin D metabolism like rifampin, phenytoin was excluded from the study. Patients with chronic renal failure was also excluded. Dilated fundoscopic examination of all subject was done and serum creatinine, Hb A1c, 25 hydroxyvitamin D (25 (OH) D) level of all subject were measured between may 2012 and September 2012 

Results: There were no statistical difference in age, sex, systolic tension, diastolic tension and body mass index between groups. Serum creatinine level was also not statistically different between groups (p = 0.11). Serum fasting glucose and HbA1c level were significantly lower in the control group than diabetic groups (p <0.001).

The mean 25 (OH)D levels of PDRP group, NPDRP group, diabetic patients without retinopathy and control group were 11,9 ± 6,4 ng/ml, 18,8 ± 10,2 ng/ml, 16,6 ± 7,5 ng/ml and 20,1 ± 9,2 ng/ml respectively. There was statistically significant difference between the PDRP group and other groups in univariate analysis (p < 0.001). When 173 diabetic patients, were compared, with control group, 25 (OH) D levels were significantly lower in diabetic patients than control group regardless of retinopathy status (p = 0.004).

Conclusions: Diabetic patients especially, patients with proliferative diabetic retinopathy had lower serum vitamin D levels than healthy subjects. Additionally randomized, controlled, prospective studies are necessary to determine whether vitamin D treatment will stop or slow the progression of diabetic retinopathy in diabetic patients.