Part of the show Keeping Your Eyes Healthy with Fish
Scientists have confirmed what your grandmother always told you - oily fish really can keep you healthier. And although epidemiologists had shown there was an association, the scientific mechanism underlying the effect remained obscure.
Now an ingenious paper in Science Translational Medicine by Harvard ophthalmologist Lois Smith has identified how a regular intake of omega-3 fatty acids, rich in fish like mackerel, can prevent age-related and diabetes-induced retinal deterioration.
By developing a mouse model of the condition, which is associated with the formation of new blood vessels in the retina, the team were able to selectively deactivate genes linked to the metabolism of fatty acids to see which ones were linked with the disease process and the protective effect of the omega-3 fatty acids.
Now they've identified the cellular and biochemical pathway involved: it's an enzyme called lipoxygenase (5-LOX). When this acts on omega-6 fatty acids, it produces pro-inflammatory mediators called leucotrienes. But when it acts on omega-3 fatty acids, such as those from oily fish, it instead produces a substance called 4-hydroxy-docosahexaenoic acid (4HDHA), which has anti-inflammatory properties and also inhibits the growth of new blood vessels in the eye, an effect achieved by activating a gene called PPAR-gamma (peroxisome proliferator-activated receptor gamma).
Reassuringly, this pathway is not affected by the use of anti-inflammatory drugs like aspirin, confirming that patients using these drugs can also benefit from increasing their dietary intake of omega-3 fatty acids.
More importantly, because the team have now identified the biochemical pathway underlying the "oily fish effect", it should be feasible to produce molecules designed specifically to exploit this chemical effect and hence provide effective treatment for a disease process that affects over 15% of people over 80.