The effect of mixed bovine brain gangliosides on hypoxic conduction block in control and streptozotocin-diabetic rats

Interleukin-6 attenuates the development of experimental diabetes-related neuropathy

Neuropathy is the most severe and the least understood complication of diabetes. We investigated the potential neuroprotective effect of IL-6 therapy in an experimental model of diabetic neuropathy. A single i.v. injection of streptozotocin (STZ, 55 mg/kg) was used to induce experimental diabetes in adult males. IL-6 (1, 10 or 30 microg/kg) was administrated either intraperitoneally on a daily basis or subcutaneously (s.c.) on a daily, on a three times or one time per week basis, starting at day 10 post-STZ. A decrease in sensory nerve conduction velocity (SNCV), indicative of neuropathy, is seen in STZ rats as early as day 10 post-STZ, a time at which blood glycaemia is already maximal. At later time points, this electrophysiological impairment became severe and clinically apparent by affecting tail flick latency. Motor dysfunction defined by a significant increase in compound muscle action potential (CMAP) latency was also recorded. At the completion of the study (day 40 post-STZ), histological examination revealed significant axonopathy and myelin loss, along with an increase in the proportion of fibers with abnormal appearance in sciatic nerves of STZ rats. These changes were not observed in non-diabetic rats and were significantly prevented by IL-6 treatment. The optimal dose appeared to be 10 microg/kg s.c. three injections per week, which showed a better effect in most of the parameters studied than 4-methylcatechol, a NGF-like neuroprotective compound. Once weekly and three times weekly administrations of IL-6 were as effective as daily treatment. Taken together, these results support the potential neuroprotective actions of IL-6. The fact that the half-life of IL-6 is only approximately 5 h while weekly dosing was neuroprotective strongly suggests activation by IL-6 of effector molecule(s) with longer duration of action.

Potential therapeutic approaches to the treatment or prevention of diabetic neuropathy: evidence from experimental studies

Recent investigations using experimental models of diabetes mellitus have emphasized the importance of impaired blood flow for the development of nerve dysfunction. Other observations suggest that this may also be the case for patients. A number of studies have revealed that several types of vasodilators can prevent or successfully treat early conduction abnormalities in diabetic rodents. These include alpha 1-adrenoreceptor antagonists, calcium channel blockers, agents that inhibit the renin-angiotensin system, and vasomodulator prostanoids. Other treatments applied to animal models, such as omega-6 essential fatty acids, aldose reductase inhibitors, aminoguanidine which prevents the formation of advanced glycation end-products, and anti-oxidants all appear to have vascular-related effects that lead to improvements in nerve conduction. These findings suggest that endothelial dysfunction and oxidative stress could be important factors in the aetiology of diabetic neuropathy. Studies have also focused on deficits in axon growth and regeneration, their relation to impaired neuronal synthesis and transport of growth-related chemicals, and neuronotrophic abnormalities. Taken together, the data give rise to the notion that an optimal therapeutic strategy could consist of improving the microenvironment of damaged nerve fibres by manipulating nerve blood flow while concurrently encouraging repair with trophic agents.