Prevention role for omega-3 in diabetes

Omega-3 fatty acids could one day play an important role in preventing diabetes complications.

OMEGA-3 fatty acids, found in cold water fish, do not just protect against heart disease, arthritis and depression – research now suggests that they can also prevent diabetic retinopathy, and US investigators may have identified how they do this. 

An animal model has shown that omega-3 fatty acids can protect against blindness in two different ways: by promoting growth of healthy blood vessels in the eye and simultaneously inhibiting the growth of abnormal blood vessels.

Harvard University researchers isolated the specific compound responsible for the action  – a metabolite of the omega-3 fatty acid DHA, known as 4-HDHA – and the enzyme that produces it (5-lipoxygenase, or 5-LOX). 

Although preliminary, the  new findings add to a previous study that found mice fed diets rich in omega-3 fatty acids had almost half the amount of abnormal blood vessel growth and a reduction in inflammatory messaging in the eye.

The finding might also reduce concerns that aspirin and anti-inflammatory drugs might hinder the body’s ability to break down omega-3 fatty acids. 

The authors say that is unlikely, since COX enzymes do not appear to be involved in the breakdown process.

This isn’t the first time Harvard researchers have linked fatty acids with the circumvention of the ill effects of diabetes.

In December, researchers identified that a fatty acid found in milk, cheese, yogurt, and butter is linked to a lower risk of type 2 diabetes. 

Researchers looked at 3736 participants in the National Heart, Lung and Blood Institute-funded Cardiovascular Health Study who had been followed for 20 years. 

Trans-palmitoleic acid, a fatty acid that is not produced by the body, was associated with healthier levels of blood cholesterol, inflammatory markers, insulin levels and insulin sensitivity. 

Moreover, participants who had higher circulating levels of trans-palmitoleic acid had a much lower risk of developing diabetes – the risk of those in the highest quintile was about 60% lower than those in the lowest quintile.

“We wonder whether this naturally occurring trans fatty acid may partly mimic the normal biological role of cis-palmitoleic acid, a fatty acid that is produced in the body,” says lead author Associate Professor Dariush Mozaffarian. 

“In animal experiments, cis-palmitoleic acid also protects against diabetes… Unfortunately, with modern diets, synthesis of cis-palmitoleic acid is driven by high amounts of carbohydrate and calories – which might limit its normal protective function.

“We wonder whether trans-palmitoleic acid may be stepping in as a ‘pinch hitter’ [substitute] for at least some of the functions of cis-palmitoleic acid,” Mozaffarian says.

Sci Transl Med 2011; 3:69ra12Ann Intern Med 2010 153:I-56