Scientists in the US and Sweden have shown that Omega 3 polyunsaturated fatty acids stopped mice from getting retinopathy, a condition where the retina deteriorates and results in blindness.
The study appears in the July edition of the journal Nature Medicine.
The researchers were from the Children’s Hospital Boston (affiliated to Harvard Medical School), Brigham and Women’s Hospital, Massachusetts General Hospital, the University of Göteborg in Sweden,and the National Eye Institute (NEI) and National Institute on Alcohol Abuse and Alcoholism (NIAAA) of the National Institutes of Health (NIH), all in the US.
The team was led by Dr Lois E. H. Smith, associate professor of ophthalmology at Children’s Hospital Boston, who said that the purpose of the study was to:
“Discover and describe the scientific basis for any possible protective role of omega-3 fatty acids against retinopathy.”
Director of the NEI, Dr Paul A. Sieving said that the study gives scientists a “better understanding of the biological processes that lead to retinopathy and how to intervene to prevent or slow disease.”
Retinopathy is a condition where the retina deteriorates. The retina is the light-sensitive part of the eye where nerves pick up the “image” that is conveyed into the eye (a little bit like the film in a camera).
The researchers said the study’s findings will help in three areas of human health: retinopathy of prematurity (ROP) which affects prematurely born infants, diabetic retinopathy, and age-related macular degeneration (AMD).
ROP is where the blood vessels in the retina of the premature baby increase and branch excessively, and this can sometimes cause bleeding and scarring and in severe cases, blindness. The musician Stevie Wonder was a premature baby and reports say that he became blind from ROP because he was given too much oxygen in his incubator.
Diabetic retinopathy is where the blood vessels swell and leak fluid, or they grow abnormally on the retina’s surface.
AMD is a disease of the macula, the part of the retina responsible for central vision. AMD is the main cause of vision loss in older people in America.
“Our study results suggest that increasing omega 3 fatty acid intake in premature infants may significantly decrease the occurrence of ROP. This changing of lipids by dietary means may also translate to AMD and diabetic retinopathy,” said Smith.
“If clinical trials find that supplementing with omega-3 fatty acids is as effective in protecting humans against retinal disease as demonstrated by the findings of this study, this cost effective intervention could benefit millions of people,” she added.
Omega 3 fatty acids contain “bioactive mediators” which protect against abnormal growth of blood vessels, the main characteristic of some retinopathies. It is thought that the bioactive mediators suppress an inflammatory protein called tumour necrosis factor alpha (TNF-alpha) which is found in cells that are closely related with blood vessels in the retina.
Smith and her team examined the effect of two omega 3 fatty acids, EPA and DHA, derived from fish oil, and arachidonic acid, an omega 6 fatty acid, on the loss of blood vessels, regrowth of healthy blood vessels, and the growth of abnormal vessels in mice. They induced retinopathy in the mice using oxygen.
They found that omega 6 fatty acid is linked to growth of abnormal blood vessels in the retina, and an increase in omega 3 and a decrease in omega 6 fatty acids in the diet of the mice reduced the area of blood vessel loss that eventually led to growth of the abnormal vessels and blindness.
To confirm the benefit of omega 3, they fed one group of mice a Japanese-style diet (more omega 3 than omega 6 fatty acids) and another group of mice a Western-style diet (less omega 3). They also studied a group of mice where the gene that helps mammals to convert omega 6 fatty acid into omega 3 was switched off.
The results showed a 50 per cent decrease in retinopathy in the mice that had higher levels of omega 3.
Lead author of the study and NEI fellowship recipient, Dr Kip M. Connor, who is also a postdoctoral research fellow at Children’s Hospital Boston, explained that:
“The retina has one of the highest concentrations of omega 3 fatty acids in the body.”
“Given this, it is remarkable that with only a two percent change in dietary omega 3 intake, we observed an approximate 40-50 percent decrease in retinopathy severity,” added Connor.
NEI staff scientist and the other lead author of the study, Dr John Paul SanGiovanni said this was a major advance in the effort to “identify modifiable factors that may influence inflammatory processes implicated in the development of common sight-threatening retinal diseases”.
SanGiovanni said the results also give a reasonable biological explanation for the findings from a number of other human studies on the link between diet and retinal disease. They also show there is a low cost and widely available nutrient that could form the basis of a treatment.
The NET will be assessing the effect of omega 3 fatty acids DHA and EPA on the progression of AMD in part of its Age-Related Eye Disease Study 2 (AREDS2).
Another trial at the Children’s Hospital Boston will also be testing the effect of omega 3 dietary supplements on premature babies.
“Increased dietary intake of omega-3-polyunsaturated fatty acids reduces pathological retinal angiogenesis.”
Kip M Connor, John Paul SanGiovanni, Chatarina Lofqvist, Christopher M Aderman, Jing Chen, Akiko Higuchi, Song Hong, Elke A Pravda, Sharon Majchrzak, Deborah Carper, Ann Hellstrom, Jing X Kang, Emily Y Chew, Norman Salem, Jr, Charles N Serhan and Lois E H Smith.
Nature Medicine Published online: 24 June 2007.
doi:10.1038/nm1591
Written by: Catharine Paddock
Writer: Medical News Today