CONTRASTING EFFECTS OF TREATMENT WITH OMEGA-3 AND OMEGA-6 ESSENTIAL FATTY-ACIDS ON PERIPHERAL-NERVE FUNCTION AND CAPILLARIZATION IN STREPTOZOTOCIN-DIABETIC RATSN

Essential fatty acid metabolism is impaired by diabetes mellitus and this may be important in the aetiology of peripheral nerve dysfunction. The effects of gamma-linolenic acid (omega-6) and fish oil (omega-3) alone, and in combination, on nerve function and capillarization were examined in 2-month streptozotocin-diabetic rats. Diabetes resulted in approximately 15 % and 23 % decreases in saphenous sensory and sciatic motor nerve conduction velocities, respectively (p < 0.001). Motor and sensory conduction velocities were in the non-diabetic range after both preventive and reversal omega-6 treatment of diabetic rats (p < 0.001). No significant changes occurred in omega-6 treated non-diabetic rats. Preventive omega-3 treatment was largely ineffective. Reversal treatment with a combination of omega-6 and omega-3 fatty acids was marginally effective and improved motor (p < 0.05), but not sensory conduction velocity. In vitro measurement of sciatic nerve resistance to hypoxic conduction failure in diabetic rats revealed a 56 % increase in the time taken for the compound action potential amplitude to be reduced by 80 % (p < 0.01) compared to non-diabetic rats. This was partially prevented by omega-6 treatment (29 % increase, p < 0.01). Reversal omega-6 treatment had a lesser effect (37 % increase, p < 0.05 compared to untreated diabetic rats). Omega-3 treatment had no significant effect on conduction failure time. Sciatic endoneurial capillary density increased by 11 % with preventive omega-6 treatment (p < 0.05), but was unaffected by reversal omega-6 and by omega-3 treatments. These results demonstrate the specificity of omega-6 essential fatty acids in improving diabetic nerve function and highlight an antagonism exerted by omega-3 components, which may have therapeutic implications.