In order to elucidate whether sorbitol accumulation in cells including Schwann's cells as well as erythrocytes (RBC), might be responsible for diabetic neuropathy, the sorbitol content (SOR-RBC, nmole/gHb), glyceraldehyde reductase activity (GAR-RBC, mU/ml) and sorbitol dehydrogenase activity (SDH-RBC, mU/ml) in RBC were determined concomitant with the motor nerve conduction velocity (MCV) in 98 diabetic patients (46men and 52 women, mean age 51.4 years old, mean duration 7.5 years). SOR-RBC levels (38.0±1.9 (SD) nmole/gHb) in diabetics were significantly higher than in normal controls (22.2±4.2). Diabetics with clinical neuropathy showed higher, but not significantly, higher, levels of SOR-RBC (47.2±5.7) as compared to those in diabetics without neuropathy (37.8±4.0). The duration of diabetes did not show any correlation with any of these three parameters, SOR-RBC, GAR-RBC or SDH-RBC. However SOR-RBC was positively correlated with fasting plasma glucose (r=0.628, n=91, p<0.01), as well as HbAi (r=0.335, n=98, p<0.05), suggesting its relatively rapid fluctuation possibly depending on plasma glucose levels. In addition, the MCV in the median and ulnar nerve was negatively correlated with SOR-RBC (p<0.05 to 0.01).
The results suggest that SOR-RBC, which fluctuates depending on plasma glucose levels during a relatiely short period, might be responsible for diabetic neuropathy.
