Researchers in the US have developed a form of the omega-3 fatty acid docosahexaenoic acid (DHA) that is capable of crossing into the eye’s retina to ward off visual declines related to Alzheimer’s disease, diabetes and other disorders.
The DHA found in fish oil capsules and other supplements is usually in a form called triacylglycerol (TAG) DHA.
Although TAG-DHA has benefits in other parts of the body, it does not reach the eyes because it cannot move from the bloodstream into the retina.
In the study, researchers created a new lysophospholipid form of DHA, or LPC-DHA.
In studies using mice, LPC-DHA successfully increased DHA within the retina and reduced eye problems associated with Alzheimer’s-like processes.
Sugasini Dhavamani, a research assistant professor in the Department of Medicine at the University of Illinois at Chicago, said:
“Dietary LPC-DHA is enormously superior to TAG-DHA in enriching retinal DHA and could be potentially beneficial for various retinopathies in patients.”
“This approach provides a novel therapeutic approach for the prevention or mitigation of retinal dysfunction associated with Alzheimer’s disease and diabetes.”
In healthy eyes, DHA is concentrated within the retina, where it helps maintain photoreceptors, the cells that convert light into signals that are sent to the brain.
DHA deficiency in the retina is associated with sight loss.
Individuals with Alzheimer’s disease, as well as those with diabetes, retinitis pigmentosa and age-related macular degeneration frequently have abnormally low levels of retinal DHA, and visual impairments are common as a result.
While boosting DHA can help to prevent such declines, increasing retinal DHA content has been challenging with currently-available supplements.
For a dietary supplement to deliver DHA to the retina, the DHA must first be able to be absorbed from the intestine into the bloodstream and then cross from the bloodstream into the retina.
Dhavamani said:
“Increasing the retinal DHA at clinically feasible doses has not been possible until now because of the specificity of the blood–retinal barrier that is incompatible with the specificity of the intestinal barrier.
“This study uses the novel approach of dietary LPC-DHA that overcomes both intestinal and blood–retinal barriers and improves retinal function.”
The researchers tested their LPC-DHA supplement in mice bred to exhibit processes similar to those found in people with early-onset Alzheimer’s disease.
After six months, mice that were fed LPC-DHA daily showed a 96 per cent improvement in retinal DHA content as well as preserved retinal structure and function.
In contrast, TAG-DHA supplements had no effect on either retinal DHA levels or function.
The findings suggest that LPC-DHA supplements could help to prevent Alzheimer’s-related declines in visual function.
Researchers believe that the approach should also be helpful for other disorders in which DHA deficiency and vision impairment are common.
