Mouse Study May Help Explain Fish Oil's
FRIDAY, Sept. 3 (HealthDay News) -- Feeding obese mice omega-3
fatty acids reduced inflammation that can lead to diabetes, a new
Fish oil supplements that contain high levels of omega-3 fatty
acids are one of the most popular dietary supplements in the United
States. While omega-3 fatty acids are widely believed to be
beneficial, exactly how they work hasn't been well understood, said
study co-author Saswata Talukdar, a post-doctoral fellow at
University of California, San Diego.
By studying fat tissue in the mice consuming fish oil,
researchers found omega-3 fatty acids seem to act on a particular
receptor on cells, GPR120, which, when activated, blocks
Chronic inflammation can lead to insulin resistance, a precursor
Therefore, "if we can fix the inflammation part, it's possible
that we could prevent insulin resistance or even ameliorate
diabetes," Talukdar explained.
The study was published in the Sept. 3 issue of the journal
Fat tissue contains macrophages, immune system cells that gobble
up bacteria, clear out cellular debris and help rid the body of
infection. But macrophages found in fat can also have a downside.
When macrophages "go rogue," Talukdar said, they produce cytokines
and other pro-inflammatory proteins.
A build up of cytokines can result in a "signaling cascade,"
that eventually leads to low-grade, chronic inflammation and
insulin resistance, Talukdar said. In people with insulin
resistance, cells are unable to properly utilize insulin, which
regulates blood sugar levels. That can lead to type 2 diabetes,
which is often linked to obesity.
While studying fat tissue, researchers found that omega-3 fatty
acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic
acid (EPA), acted on the specific receptor, GPR120 (for G
protein-coupled receptor), found on the surface of macrophages.
The GPR120 receptor is found only on pro-inflammatory
macrophages in mature fat cells, according to the study.
Exposure to omega-3 fatty acids activates the receptor, which
reduces the runaway pro-inflammatory cascade.
When researchers fed obese mice omega-3 fatty acids,
inflammation subsided and insulin sensitivity improved. Blood
glucose levels also dropped significantly, Talukdar said.
But in obese mice that had their GPR120 receptor "knocked out"
through genetic modification, omega-3 fatty acids had no effect --
thus underscoring the researchers' findings.
"Prior to this point, people have always suspected omega-3s are beneficial. That's why people have been taking them," Talukdar said. "What we decided to ask was why omega-3 fatty acids can be anti-inflammatory. This shows when you give omega-3 fatty acids to an inflamed model, it might help battle insulin resistance."
This study focused on diabetes, but omega-3 fatty acids may also
help with other diseases in which inflammation plays a role,
including cancer and cardiovascular disease, researchers said.
The question that may first come to consumers' minds is: Should
I be taking fish oil supplements?
Experts note that a positive (or negative) finding in animal
research doesn't guarantee the same result in people. Mice are
often used in animal experiments because of their remarkable
genetic similarity to humans, they say, but the majority of mice
and other animal research fails to produce rewards for humans.
Dr. Jacob Warman, chief of endocrinology at The Brooklyn
Hospital Center, called the results "impressive," but he said
subsequent studies in people are needed.
Still, there's really no downside to taking fish oil -- and lots
of people already do, Warman said.
Fish oil supplements are available over the counter, as well as
by prescription. Doctors can also prescribe the drug Lovaza, made
from fish oil, to help lower triglycerides in those with very high
levels, Warman said.
However, to prevent diabetes and many other chronic diseases,
your best bet is still to lose weight if you're obese, exercise and
eat a healthy diet, Warman said.
"But patients with a history of diabetes in the family or patients who have metabolic syndrome, including obesity, high triglycerides, elevated blood pressure, elevated uric acid and low HDL levels," might want to try fish oil supplements, Warman said. "There is no downside."
The U.S. National Institutes of Health has more on
omega-3 fatty acids.
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