A role for omega-3 polyunsaturated fatty acid supplements in diabetic neuropathy

Diabetes results in an insulin-related disorder of lipid metabolism that reduces production of long-chain polyunsaturated fatty acids (PUFAs; e.g., docosahexanoic acid, DHA). This study considers the role that this lipid change has on retinal function.

From conception, rats (n = 56) were fed diets either balanced (n = 32) in PUFAs or deficient in omega-3 (n = 24). Half were assigned to control (n = 28) or streptozotocin (STZ: n = 28) treatment at 7 weeks of age. Key metabolic indices were assayed at 19 weeks, and retinal function was determined by electroretinogram (ERG) at 20 weeks. Retinal anatomy and lipid assays of 20-week-old animals were used to identify structural changes and tissue PUFA content.

The systemic indices of diabetic rats were not affected by diet. Lipid composition of retinal membranes reflected the dietary manipulation, and diabetes amplified some fatty acid changes consistent with reduced desaturase activity. Diabetes produced significant reduction in rod function (-33%) only in the absence of fish oil, whereas cone responses (-46%) and inner retinal oscillatory potentials (-47%) showed either no effect of diet or a partial diet effect with a significant diabetes effect. Anatomic analysis revealed no disorder in the retinal neurons, although changes in the Müller glia were noted in diabetes, regardless of diet.

A diet balanced in long-chain PUFAs modifies retinal lipid membranes in diabetes and prevents rod dysfunction. Dietary modification was not found in the cone or glial response but a partial improvement was evident in the OPs, most likely secondary to the larger photoreceptor output.