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G Bhanuprakash Reddy, A. Satyanarayana, N. Balakrishna, P. Sujatha, P. Y. Reddy, P. Suryanarayana, K. Viswanath, Radha Ayyagari; Diabetic Retinopathy: Association With Hyperhomocysteinaemia And Vitamin-B12 Deficiency. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5940.
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Multiple factors are involved in predisposing diabetic subjects to diabetic retinopathy (DR). Though, many studies have evaluated the association between homocysteine and DR, the results are inconsistent. Amongst the many determinants of homocysteine, vitamin B status has been shown to be a major confounding factor. However, very little is known about the relationship between vitamins B status and DR.
A cross-sectional case-control study was conducted with 400 type 2 diabetic (T2D) subjects with retinopathy (DR) (n=250) and without retinopathy (NDR) (n=150) along with 100 normal control subjects based on strict inclusion and exclusion criteria. Diabetic subjects on nutritional supplements, history of nephropathy and other complications were excluded. In addition to ophthalmic examination including FFA and clinical profile, the blood levels of all B-vitamins (B1, B2, B6, B12 and folic acid) and homocysteine were analyzed by HPLC and spectrophotometry.
The mean plasma homocysteine levels were higher in T2D patients compared to control subjects. Among the T2D patients, the plasma homocysteine concentration of DR group was found to be higher compared to the NDR group (p<0.05). While, the blood levels of vitamins B1 and B2 were comparable between the groups, plasma vitamin B6 and folic acid levels were significantly (p<0.05) lower in T2D group compared to the control group. However, there was no significant difference in the mean levels of vitamin B6 and folic acid between NDR and DR groups. Plasma vitamin-B12 levels were significantly lower (p<0.01) in diabetic groups compared to control group. Interestingly, a significantly lowered (p<0.05) plasma vitamin B12 levels were observed in DR patients compared to NDR patients. The prevalence of vitamin B12 deficiency was significantly higher in DR compared to NDR and control groups. Homocysteine levels were associated with vitamin B12 and folic acid but not with vitamins B1, B2 and B6. Further, homocysteine and vitamin B12 levels were not related to the age, BMI and duration of diabetes.
These results suggest, for the first time, a possible association between deficiency of plasma vitamin B12, hyperhomocysteinaemia and DR.
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