Increased erythrocyte aldose reductase activity in type 1 diabetic patients

Elevated erythrocyte sorbitol levels have been demonstrated in diabetic patients. In order to explain the enhanced sorbitol formation, it has been suggested that aldose reductase might be activated by hyperglycaemia. Although aldose reductase activity has been reported to be increased in some tissues of diabetic patients, the effects of varying concentrations of glucose on the enzyme activity in vivo are unknown. To determine whether or not erythrocyte aldose reductase activity is increased in diabetic patients and is affected by glucose levels, we collected blood samples from 10 Type 1 diabetic patients while fasting and 2 h after a standard meal. We measured the activity of erythrocyte aldose reductase after partial purification by column chromatography. The results showed that erythrocyte aldose reductase activity was significantly increased in diabetic patients as compared with non-diabetic subjects (7.3 +/- 0.7 (+/- SE) vs 5.2 +/- 0.3 u l-erythrocytes-1, p less than 0.05). No correlation, however, was observed between fasting plasma glucose levels and the enzyme activity, and acute elevation of the blood glucose level did not affect the enzyme activity.