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Diabetic retinopathy, or DR, is a leading cause of blindness that occurs when blood sugar blocks the tiny vessels that supply blood to the retina. Researchers know that docosahexaenoic acid, or DHA, an omega-3 fatty acid found in the eyes in high concentration, supports eye and vision health, but do not yet fully understand its relation to DR.

In this ball-and-stick model of the docosahexaenoic acid molecule, C22H32O2, carbon is black, hydrogen is white and oxygen is red.

In a recent functional study, researchers at the University of Illinois at Chicago examined the correlation between DHA levels and the development of diabetic retinopathy. Sugasini Dhavamani, a research assistant professor, and Poorna Chandra Rao Yalgala, a researcher, led the study.

“We showed for the first time that reduced retinal DHA levels in humans and mice models of diabetes,” Dhavamani said.

The team determined DHA levels, activity and function in the retina using gas chromatography–mass spectrometry, optical coherence tomography and electroretinography, respectively. They found that DHA levels in mice that were genetically modified to have diabetes were 9% to 11% and in diabetic humans were 8% to 10%, whereas DHA levels of nondiabetic mice and humans were 15% to 18%, meaning they observed a 40% to 50% reduction of DHA in diabetic mice and humans.

The observed difference correlated with variations in the levels of fatty acid elongation, metabolism and inflammation markers. The researchers also reported reduced retinal thickness and function in diabetic mice and humans.

While oily fish is a major dietary source of DHA, clinical trials with fish oil have not improved visual function. “This is due to the specificity of blood–retinal barrier that is incompatible with the specificity of the intestinal barrier,” Dhavamani said.

Left to right, researcher Poorna C.R. Yalagala and research assistant professor Sugasini Dhavamani did this study at the University of Illinois at Chicago.

The researchers previously tested whether this limitation could be overcome using a lysophospholipid form of DHA to improve retinal function. They that it is possible to increase retinal DHA by almost 100% in a normal adult mouse with a low dose of lysophosphatidylcholine-DHA.

The UIC team believes this form of DHA could be used therapeutically to prevent or mitigate retinal dysfunction associated with diabetes and Alzheimer’s disease, as well as age-related macular degeneration. Moreover, it could pave the way for a safe, cost-effective nutraceutical strategy to prevent diabetes-associated visual sensitivity decline in a majority of the population.