Diabetes, Vol 40, Issue 5 532-539, Copyright © 1991 by American Diabetes Association
Essential fatty acid diet supplementation. Effects on peripheral nerve and skeletal muscle function and capillarization in streptozocin-induced diabetic rats
NE Cameron, MA Cotter and S Robertson
Division of Physiology, School of Biomedical Sciences, University of Aberdeen, Scotland, United Kingdom.
Effects of essential fatty acids on nerve conduction, hypoxic resistance,
skeletal muscle contractile properties, and capillary density were examined
in streptozocin-induced diabetic rats. Nondiabetic and diabetic controls
and three diabetic groups treated with 10% supplements of corn oil, evening
primrose oil (Efamol), or a mixture of 80% evening primrose oil and 20%
fish oil (Efamol Marine) for 2 mo were used. Efamol and Efamol Marine
increased plasma gamma-linolenic acid levels, but arachidonic acid was
elevated only with Efamol. Diabetes resulted in 15-29% reductions in
sciatic motor and sensory saphenous nerve conduction velocity. Efamol
prevented conduction deficits more effectively than Efamol Marine, and corn
oil had no effect. In vitro measurement of sciatic nerve hypoxic resistance
revealed a 49% increase in the time taken for action potential amplitude to
decline by 50% with diabetes. Corn oil had no significant effect. With
Efamol, hypoxic resistance was within the nondiabetic range. Efamol Marine
produced intermediate results. Functional improvements may relate to
enhanced vasa nervorum perfusion, because endoneurial capillary density
increased by 22% with Efamol, angiogenesis perhaps resulting from
eicosanoid production from arachidonic acid. Soleus muscle contractions
were prolonged by diabetes. This was partially corrected by treatment,
Efamol being most effective. Extensor digitorum longus muscle had reduced
tetanic tension with diabetes, and this was prevented by all treatments.
Soleus showed a modest increase in capillarization with Efamol, which may
have contributed to reduced susceptibility to fatigue. The data suggest
involvement of abnormal fatty acid metabolism in the etiology of diabetic
neuropathy and myopathy.