Key Points
This study explores the potential role of omega-3 and other classes of monounsaturated and polyunsaturated fatty acids on peripheral neuropathy. Rats were fed a high-fat diet for 16 weeks followed by 32 weeks of diet enriched in oleic acid (olive oil; 18:1, n-9), linoleic acid (safflower oil; 18:2, n-6), γ-linolenic acid (evening primrose oil; 18:3, n-6), α-linolenic acid (flaxseed oil; 18:3, n-3), or eicosapentaenoic/docosahexaenoic acids (menhaden oil; 20:5 and 22:6, n-3).
Treating DIO rats with the omega-6 polyunsaturated fatty acid, γ-linolenic acid, derived from evening primrose oil, or the omega-3 polyunsaturated fatty acid, α-linolenic acid, derived from flaxseed oil, was more effective than safflower oil in improving glucose clearance, vascular reactivity of epineurial arterioles to acetylcholine, cornea nerve fiber length and cornea sensitivity, and motor nerve conduction velocity. α-Linolenic acid has been reported to improve glucose tolerance in obese rats and insulin sensitivity/glycemic control in human subjects with prediabetes or type 2 diabetes. It has also been reported to prevent endothelial dysfunction in type 2 diabetic rats by enhancing endothelial nitric oxide synthase activity and reducing oxidative/nitrative stress. Increasing the concentration of omega-3 fatty acids reduces the omega-6 to omega-3 ratio, thereby reducing inflammatory stress. In this study, there was a significant increase in eicosapentaenoic acid but no change in docosahexaenoic acid levels in the liver of DIO rats treated with flaxseed oil. This study showed that treating DIO rats, after vascular and nerve pathology have developed, with oils enriched in oleic acid and linoleic acid did not improve vascular or neural function. Treating these rats with either γ-linolenic acid or α-linolenic acid, derived from evening primrose oil or flaxseed oil, respectively, provided moderate benefit.
ABSTRACT
Purpose: This study aimed to determine the effect of dietary oils (olive, safflower, evening primrose, flaxseed, or menhaden) enriched in different mono unsaturated fatty acids or polyunsaturated fatty acids on peripheral neuropathies in diet-induced obese Sprague-Dawley rats. Materials and methods: Rats at 12 weeks of age were fed a high-fat diet (45% kcal) for 16 weeks. Afterward, the rats were fed diets with 50% of the kilocalories of fat derived from lard replaced by the different dietary oils. In addition, a control group fed a standard diet (4% kcal fat) and a high fat fed group (45% kcal) were maintained. The treatment period was 32 weeks. The endpoints evaluated included motor and sensory nerve conduction velocity, thermal sensitivity, innervation of sensory nerves in the cornea and skin, and vascular relaxation by epineurial arterioles. Results: Menhaden oil provided the greatest benefit for improving peripheral nerve damage caused by dietary obesity. Similar results were obtained when we examined acetylcholine-mediated vascular relaxation of epineurial arterioles of the sciatic nerve. Enriching the diets with fatty acids derived from the other oils provided minimal to partial improvements. Conclusion: These studies suggest that omega-3 polyunsaturated fatty acids derived from fish oil could be an effective treatment for neural and vascular complications associated with obesity.
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