Effect of islet transplantation on neuroelectrophysiological abnormalities in diabetic inbred Lewis rats: comparison of primary versus secondary prevention.

Background: Neuroelectrophysiological abnormalities in diabetes indicate nervous function failure. Restoration of euglycemia by islet transplantation may prevent or reverse these abnormalities.

Methods: Pancreatic islets were transplanted in inbred Lewis rats after 15 days (Ta12, primary prevention) or 8 months (Tb12, secondary prevention) from streptozotocin-induced diabetes. Transplanted and control (normal and diabetic) rats were followed for a total period of 12 months. Metabolic parameters, somato-sensory, brain-stem auditory, and visual evoked potentials were determined at the beginning and at the end of the study and before transplantation for secondary prevention.

Results: The metabolic parameters in transplanted animals were similar to those of normal animals. Ta12 and normal group somato-sensory conduction velocities did not vary and were always significantly higher than those of diabetic animals. By contrast, Tb12 group conduction velocities showed only a partial improvement, values lying between those of diabetic and normal rats. Brain-stem auditory (waves I, II, and III) latencies in Ta12 group were similar to those of normal rats and significantly lower than those of diabetic animals (wave I: P<0.01; waves II and III: P<0.05). Tb12 group wave I and II latency values remained altered (P<0.005 and P<0.01 versus normal values respectively). Visual evoked potentials-P1 wave latencies in transplanted rats were always higher than those of normal and diabetic animals.

Conclusions: After primary prevention, central and peripheral neurological alterations were abolished. After secondary prevention, transplantation beneficial effects were partial, occurring mainly at peripheral level. These results highlight the importance of early transplantation to prevent hyperglycemia-dependent neuroelectrophysiological alterations.