Blood thiamine pyrophosphate concentration and its correlation with the stage of diabetic retinopathy.

PURPOSE: To assess the possible relationship between blood thiamine pyrophosphate (TPP) concentration and stage of diabetic retinopathy (DR). METHODS: This comparative cross-sectional study included 80 patients with type 2 diabetes mellitus (T2DM) and 20 age- and gender-matched healthy controls. Diabetic patients were subclassified into four groups each consisting of 20 subjects: no DR, mild-moderate non-proliferative DR (mild-moderate NPDR), severe NPDR, and proliferative DR (PDR). Blood TPP concentration was assessed with high-performance liquid chromatography (HPLC) assay and was correlated with the stage of DR. RESULTS: Mean blood TPP concentration was 80.2 ± 14.8 nmol/L in control group. It was, respectively, 69.85 ± 18.1, 64.95 ± 13.4, 61.9 ± 13.4 and 60.75 ± 14.3 nmol/L in no DR, mild-moderate NPDR, severe NPDR and PDR groups. For mild-moderate NPDR, severe NPDR and PDR groups, TPP concentrations were significantly lower compared with controls (p: 0.014, 0.002, 0.001, respectively). Mean TPP concentration for NPDR patients was higher than for PDR patients, but the difference was not significant (p: 0.478). ANOVA revealed a significant difference between TPP concentrations of groups (p: 0.001). Mean TPP concentration decreased with the stage of DR, and number of patients with thiamine deficiency increased gradually with the stage of DR. A negative correlation was found between the TPP level and occurrence of DR (p: 0.000). CONCLUSION: The results suggest that lower blood TPP concentrations were associated with higher risk of DR. Thiamine might play an important role in the pathophysiology and progression of DR. Thiamine and its derivatives might represent an approach to the prevention and/or treatment of early DR.