Increased DNA-glycation in type 2 diabetic patients: the effect of thiamine and pyridoxine therapy.

It is well known that advanced glycation plays an important role in the progression of diabetic complications. Although several studies have been done on protein glycation, studies related to DNA glycation is limited. The aim of this study is primarily to investigate DNA glycation in diabetes mellitus and secondarily to observe the effects of vitamins B 1 and B 6 . Patients with diabetes (n=31) were divided into 2 groups as patients with nephropathy (n=17) and without nephro­pathy (n=14). The control group was recruited from age and sex matched healthy individuals (n=30). In the experimental groups, DNA glycation was measured in DNA isolated from leukocytes. HbA 1c , thiamine pyrophosphate (TPP) and pyridoxal 5-phosphate (PLP) levels were determined in whole blood; glucose and insulin levels in plasma. Patients with nephropathy were further divided into 2 groups and were administered either vitamins B 1  + B 6 (n=6) or B 6 (n=11), for 5 months. All the measurements were performed both before and after the vitamin administration period. AGE-DNA levels were found significantly higher in diabetic patients (p 1 and B 6 caused a significant decrease in AGE-DNA values (p This study shows that the combined administration of vitamins B 1 and B 6 to diabetic nephropathy patients causes a decrease in DNA glycation in leukocytes. Importantly the administration of vitamin B 6 alone did not have such an effect. To our knowledge, these are the first reported findings related to glycation of leukocyte nuclear DNA in diabetic nephropathy.