Background: Many cellular, preclinical and observational studies support a role for vitamin D (VD) in the pathogenesis of type 2 diabetes. VD is suggested to be an inhibitor of angiogenesis. A growing body of evidence suggests an association between VD inadequacy and diabetic retinopathy.
Objective: To study the relation between 25 (OH) vitamin D level and diabetic retinopathy (DR) in patients with type 2 diabetes mellitus and to evaluate for any relation between 25 (OH) vitamin D level and different stages of diabetic retinopathy.
Subjects and methods: 50 Type 2 diabetic patients and 50 healthy volunteers (control group) matched by age and sex participated in the study. Based on their ophthalmic findings, the type 2 diabetic patients were divided into two groups: group (I) 25 patients with DR and group (II) 25 patients without DR. Fluorescein angiography was done for group (I) and accordingly the patients were further classified into three subgroups: moderate NPDR, severe NPDR and PDR. Each subgroup is then divided according to presence or absence of clinically significant macular edema (CSME). Fasting blood sugar, HbA1c, renal functions, liver functions, lipid profile, serum calcium, serum phosphorous, intact parathyroid hormone (iPTH) and serum 25 hydroxyvitamin D3levels were done to all participants in the study.
Results: Mean 25(OH) VD level was lower in type 2 diabetic cases than in control group (P<0.01). Mean 25(OH) VD level was lower in type 2 diabetic cases with DR than type 2 diabetic cases without DR (P<0.05). Patients with PDR have the lowest mean 25(OH) vitamin D level compared to patients with moderate NPDR and severe NPDR (P<0.05). 25(OH). VD level was inversely correlated with age, duration of type 2 diabetes mellitus, stages of diabetic nephropathy, fundus findings, BMI, SBP, DBP, glycemic parameters, urinary ACR, total cholesterol, triglycerides, LDL-C (P<0.01) and iPTH level (P<0.05). 25(OH) VD level was positively correlated with GFR, HDL-C and total calcium level.
Conclusions: There is an association between 25 (OH) vitamin D insufficiency and DR among patients with type 2 diabetes mellitus. Low serum 25 (OH) vitamin D might be a risk marker of development or progression of DR. Measurement of serum 25 (OH) vitamin D concentrations could become a useful biochemical marker related to the severity of DR. The effect of vitamin D replacement in patient with DR should be evaluated.