[Reduction of erythrocyte sorbitol by ascorbic acid in patients with diabetes mellitus]

The content of erythrocyte sorbitol could be reduced by ascorbic acid (AA). To confirm the effect of AA on human erythrocyte sorbitol accumulation and explore its mechanism of the action, we studied in vitro the effects of ascorbic acid on the contents of both sorbitol and glucose in human erythrocytes. The effect of AA on the ratio of sorbitol to glucose in erythrocyte (S/EG) which was referred to as a marker of aldose reductase (AR) activity was observed. Both the accumulation of erythrocyte sorbitol and S/EG were reduced by the addition of ascorbic acid (AA) during in vitro incubations. The sorbitol content in the erythrocyte and S/EG were reduced by a maximum of 87.3%, 83.4% and 93.8%, 63.9% when the medium's AA concentration was at its peak in the 5.6 mmol/L and 28 mmol/L glucose concentration of medium respectively. These suggested that the activity of polyol pathway could be inhibited effectively by AA which might directly act on the activity of AR. The results of a double-blind cross-over trial using AA tablets or inert inositol tablets in 8 diabetic patients showed that the supplementation of 1,000 mg AA/day continued for 2 weeks resulted in reductions of 12.2% and 21.8% in both erythrocyte sorbitol and red cell sorbitol: plasma glucose (S/PG) ratio, respectively (P < 0.05). The fasting plasma glucose levels measured coincidently revealed no changes (P > 0.05). This suggests that the supplementation of moderate AA (1,000 mg/day) might provide a simple, safe and effective means of preventing and ameliorating chronic complications of diabetes.