Interaction between oxidative stress and gamma-linolenic acid in impaired neurovascular function of diabetic rats.

Nerve conduction and perfusion deficits in diabetic rats depend on increased oxidative stress and impaired n-6 essential fatty acid metabolism, which are corrected by free radical scavenger and gamma-linolenic acid (GLA)-rich oil treatments, respectively. We investigated the interaction between these mechanisms on conduction velocity and endoneurial blood flow by use of low-dose antioxidant (BM15.0639) and GLA treatments, alone and in combination. After 8 wk of streptozotocin-induced diabetes, sciatic motor conduction velocity was 20.9% reduced. Treatment with GLA or BM15.0639 for the final 2 wk corrected this deficit by 18.5 and 20.0%, respectively; however, joint treatment caused 71.5% improvement, corresponding to a 7.5-fold amplification of individual drug effects. A 48.3% deficit in sciatic nutritive endoneurial blood flow was corrected by 34.8 and 24.8% with GLA and BM15.0639 treatments, respectively. With joint treatment, the flow improvement of 72.5% was greater than expected from individual drug effects, indicating a facilitatory interaction. Thus the synergistic effect of combined antioxidant and n-6 essential fatty acid treatment could potentially provide increased therapeutic power against diabetic neuropathy.