Fish oil supplements don’t affect lung function in CF rat study

Changes in dietary fat intake did not affect mucus content or lung function in a study involving a rat model of cystic fibrosis (CF).

The researchers said the findings suggest that fish oil supplements do not meaningfully affect lung outcomes in CF. The study also suggests that CF may alter how the body processes fats — which can affect both how fats are absorbed in the diet, and how fats are managed in the body following infection with Pseudomonas aeruginosa.

The study, “Cystic fibrosis restricts systemic and local lipid modulation during lung infection,” was published in Lipids in Health and Disease.

CF is a genetic disorder marked by abnormally thick and sticky mucus, which builds up in organs to drive most CF symptoms. In the digestive tract, mucus can block the release of digestive enzymes and make it harder for the body to absorb certain types of nutrients, particularly fats. Meanwhile, in the lungs, thick mucus can impair respiratory function and also provide a fertile breeding ground for infectious bacteria. P. aeruginosa is a common cause of problematic lung infections in people with CF.

Mucus is mostly water, but it also contains a number of fat molecules that are essential to its function. This has led some researchers to speculate that changing dietary fat intake — for example, by taking dietary supplements of fish oil, which is rich in polyunsaturated fatty acids (PUFAs), a type of fat molecule — might lead to mucus changes in CF.

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Rat study aims to shed light on CF and dietary fat

A team of scientists in Australia conducted a series of tests in rats aiming to better understand how CF affects the body’s response to changes in dietary fat. Wild-type (healthy) and CF rats were given diets supplemented with either fish oil or lard, and some rats on each diet were also exposed to P. aeruginosa infection.

As expected, the dietary fat modifications led to changes in the rats’ blood; for instance, rats given fish oil had higher levels of PUFAs. However, the changes in blood fat content were notably less pronounced in CF rats than in wild-type rats.

“Overall, alterations in [blood] fatty acids were observed following dietary intervention and infection,” the researchers wrote. “However, these fatty acid changes were significantly dampened in the [CF] rats.”

Results also indicated that P. aeruginosa infection led to changes in fat content in the blood, lungs and liver, which play important roles in processing fat. But these changes were more dramatic in wild-type mice compared with their CF counterparts.

Among CF rats, changing the fatty acid content of diet did not produce significant differences in lung function or in the lungs’ response to infection, suggesting that changes in dietary fat are likely not an effective strategy to achieve meaningful changes in the lungs of people with CF.

“These findings suggest that, if dietary fatty acid composition influenced [mucus] function, the effects were likely subtle … and did not result in measurable impairment of global lung mechanics under the conditions studied,” the researchers wrote. “Consequently, while changes in [mucus] composition remain a plausible biological mechanism, our data do not support a major effect of dietary fatty acid supplementation on [lung] function.”