Comparison of Serum Vitamin B12 Levels in Type 2 Diabetes Mellitus Patients with and without Diabetic Retinopathy: A Case-control Study

Abstract

Introduction: Diabetes mellitus is characterised by hyperglycaemia. Chronic elevation of hyperglycaemia lead to generation of free radicals and Advanced Glycation End products (AGEs) which results in damage of many organs such as heart, kidney, eyes, nerves and blood vessels. Diabetic Retinopathy (DR) is the leading cause of blindness among diabetic patients. Vitamin B12 is a vital micronutrient that is essential for the proper functioning of the central nervous, cardiovascular and haemopoetic systems. It is also found that its deficiency is more prevalent in Type 2 Diabetes Mellitus (T2DM) and evident clinically. Aim: To compare the serum vitamin B12 levels and Glycated Haemoglobin (HbA1c) levels in patients with and without diabetic retinopathy. Materials and Methods: This was hospital based observational case-control study conducted in Biochemistry Department in collaboration with Ophthalmology Department at the Oxford Medical College, Hospital and Research Centre, Yadavanahalli, Bengaluru, Karnataka, India, from January 2018 to June 2018 with total of 90 subjects. Among 90 patients, 30 patients were with diabetes mellitus with Retinopathy (DR), 30 were with diabetes mellitus without retinopathy (NDR) and 30 were also recruited as control (healthy individuals). The mean and standard deviation were used to describe continuous data. Analysis of Variance (ANOVA) was used to statistically compare the mean difference between more than two sets of quantitative data. Results: The mean plasma blood glucose levels were higher in T2D patients with DR, Fasting Blood Glucose (FBG) (270.4±94.2 mg/dL) and Postprandial Blood Glucose (PPBG) (425.6±131.8 mg/dL) compared to control subjects FBG (95.4±10.7 mg/dL). Among the T2D patients the plasma HbA1c concentration of DR group was found to be higher (11.0±2.3%) compared to the NDR group (p-value <0.001). While, the blood levels of vitamin B12 were comparable between the groups, serum vitamin B12 levels were significantly lower (p-value <0.001) in T2DM group with DR (200.7±201.9 pg/mL) compared to the control group (1004.8±304 pg/mL). Conclusion: The patients with diabetic retinopathy showed that low serum vitamin B12 is associated with elevated Glycated haemoglobin (HbA1c) levels, as a result of poor glycaemic control, endothelial dysfunction and oxidative stress leading to development and progression of DR.