Fish oil may protect preemies' eyesight

Perhaps nowhere in the body is the adage "you are what you eat" so true as in your eyes, a link scientists are banking on in a novel bid to save premature babies' vision.

Doctors are about to begin testing whether fish oils could prevent a disease that can silently attack behind preemies' tiny eyelids, one that strikes about 16,000 U.S. infants a year and blinds hundreds.

It's part of research into a trio of apparently eye-healthy compounds that babies born too early miss absorbing from their mothers _ research gaining increasing attention as more and babies are born premature and at risk.

"We're trying to mimic what would happen in utero," explains Dr. Lois Smith, an opthalmologist at Children's Hospital Boston who is leading the work. "Rather than give drugs, we're doing replacement treatment."

Preventing the disease _ called retinopathy of prematurity, or ROP _ is a major goal, because there's no sure way to save vision once it strikes. Laser therapy decreases but doesn't eliminate the chance of blindness, and many babies who don't go blind still suffer serious damage.

It's not just an issue for preemies. The same abnormal growth of blood vessels behind ROP triggers two leading causes of blindness in adults: diabetic retinopathy and age-related macular degeneration. Already, scientists are studying if these omega-3 fatty acids _ the same kind touted for heart health _ could protect adult eyes, too.

Why might they? These diseases destroy the retina, the eye's innermost layer, which harbors a higher percentage of certain fats than other organs. Eat lots of salmon, rich in omega-3s, and your retina will show it. Eat mostly hamburgers, and your retina will harbor more of a different fatty acid, omega-6s. The retina's composition actually changes with diet.

Mothers pass omega-3s to their unborn children mostly during the third trimester, when the eyes develop most rapidly. Preemies not only miss out on some or all of that transfer, but omega-3s aren't added to the intravenous feeding that many require, either.

Premature babies have still forming retinas; blood vessels necessary to nourish them haven't finished growing. ROP forms when something spurs those blood vessels to grow abnormally _ too many form, and they leak.

But do omega-3s play a role? Smith and colleagues at Harvard and the National Eye Institute first turned to mice to find out.

They harmed the mice retinas in a way that mimics ROP, and then fed them different foods: Half ate the rodent version of a typical Western diet, high in omega-6s and low in omega-3s. Half ate the equivalent of a Japanese diet, with a 2 percent higher omega-3 content.

That simple change cut in half the retinal disease among the omega-3-nibbling mice, Smith reported last month in the journal Nature Medicine.

More intriguing, the omega-3s didn't just block bad blood vessels from forming. They also helped normal, healthy blood vessels grow. They appeared to work by blocking well-known inflammation-causing pathways in the body _ while mice fed more of the omega-6s experienced extra inflammation.

Now, Smith is about to begin a study in premature babies at her Boston hospital to see if adding omega-3s to their IV feedings _ feedings that today contain omega-6s instead _ decreases their risk of eye damage.

"This could be a very simple and safe treatment," says Dr. Rafael Ufret-Vincenty, a retina specialist at the University of Texas Southwestern Medical Center.

Indeed, omega-3s have long been known to be important for newborn brain development; they're in breast milk and are added to some formulas for older babies. When it comes to preemies' IV feeding, a version rich in omega-3s is available in Germany but hasn't spread to North America, says Dr. Sylvain Chemtob, an ROP specialist at Sainte-Justine University Health Centre in Montreal.

"It makes a lot of biological sense," he says.

These are the same fish oils sold as over-the-counter dietary supplements for heart health, and a nationwide study already is recruiting adults with macular degeneration to test if high doses could slow their vision loss.

For preemies, omega-3s aren't the only missing-from-mom player generating attention. A drug combination sold to treat hormone-deficient children grow taller is being studied, too _ a growth hormone called IGF-1 and a "binding protein" that helps regulate it.

Smith already knew babies with ROP lacked the growth hormone, but last month she and colleagues at Sweden's University of Goteborg reported they also have less binding protein than healthy babies. Studies in mice suggest that protein helps ROP-stricken retinas develop more normally, the Swedish team and University of Florida researchers reported, apparently by calling on stem cells to help build strong blood vessels.

Stay tuned: the Swedish scientists have begun a pilot study of the drug combo, Insmed Inc.'s Iplex, in preemies.

___

EDITOR'S NOTE _ Lauran Neergaard covers health and medical issues for The Associated Press in Washington.