Aldose reductase inhibition ameliorates pupillary light reflex and F-wave latency in patients with mild diabetic neuropathy

OBJECTIVE - The present study was conducted to investigate the effect of an aldose reductase inhibitor, epalrestat, on autonomic and somatic neuropath y at an early stage in type 2 diabetic patients by assessing the pupillary light reflex and minimum latency of the F-wave. RESEARCH DESIGN AND METHODS - A total of 30 diabetic patients with subclini cal or mild diabetic neuropathy were randomly allocated to a control group (n = 15) and epalrestat (150 mg/day) group (n = 15). After 24 weeks, the pu pillary light reflex test, cardiovascular autonomic function tests, and ner ve conduction study were performed. RESULTS - The beneficial effect of epalrestat on the pupillary light reflex was observed in the minimum diameter after light stimuli (P = 0.044), cons triction ratio (P = 0.014), and maximum velocity of constriction (P = 0.008 ). Among cardiovascular autonomic nerve functions, the ratio of the longest expiratory R-R interval to the shortest inspiratory R-R interval during de ep breathing was significantly improved by epalrestat (P = 0.037). Minimum latencies of F-wave of median and tibial motor nerves were significantly sh ortened by epalreslat (P = 0.002 and P = 0.001, respectively); however, no significant effects were observed in motor or sensory nerve conduction velo city. CONCLUSIONS - These observations suggest that epalrestat may have therapeut ic value at the early stage of diabetic neuropathy and that the pupillary l ight reflex and minimum latency of F-wave may be useful indicators of diabe tic neuropathy.