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Research at Mass General
The research team from the Laboratory for Lipid Medicine and Technology (LLMT) in Massachusetts General Hospital sought to determine if omega-3 fatty acids can alleviate pulmonary and systemic inflammation induced by ambient PM2.5 airborne pollution in urban environments throughout the world.
PM2.5, defined as fine particles with diameter smaller than 2.5 mm, are mainly produced from combustions such as industrial process, power plants and motor vehicles, etc.
Long-term exposure to high levels of PM2.5 is linked to various adverse health effects, including respiratory-related diseases, cardiovascular diseases, diabetes neurodegeneration and cancer.
The key underlying mechanism by which PM2.5 cause detrimental health outcomes in the whole body is still not well understood.
Researchers from the Laboratory for Lipid Metabolism and Technology (LLMT) at Massachusetts General Hospital hereby investigated how PM2.5 caused damage to the body, and whether omega-3 could have any beneficial effects against PM2.5-induced health problems.
They firstly exposed mice to non-toxic, fluorescent PM2.5 particles and observed their distribution in the body. They showed, for the first time, direct evidence that PM2.5 particles could penetrate pulmonary barrier and travel to other major organs, including brain, liver, spleen, kidneys and testes.
Consequently, mice exposed to PM2.5 exhibited a remarkable increase in inflammation and oxidative stress, compared to mice without PM2.5 inhalation.
Next, they probed into whether omega-3 could reduce PM2.5–induced inflammation and oxidative stress using two experimental approaches:
1.) Omega-3 supplementation as a therapeutic treatment following PM2.5 exposure;
2.) Utilization of the transgenic fat-1 mouse model with endogenously elevated levels of tissue omega-3 to examine their preventative potential for PM2.5-induced pathological changes.
Results showed that omega-3 supplemented mice and fat-1 transgenic mice showed a significant reduction in inflammation and oxidative stress compared to their PM2.5 exposed controls.
Together, these novel findings demonstrated that inhaled PM2.5 could distribute in the whole body, subsequently inducing chronic inflammation and oxidative stress, and omega-3 may serve as an immediate and effective dietary approach to protect against PM2.5-induced health consequences.
Four major questions were addressed in this study:
We used fluorescent-labeled synthetic particles to mimic PM2.5 inhalation, which allowed us to track their distribution in the body.
Tissue levels of omega-3 were elevated by both dietary supplementation and utilization of fat-1 transgenic mouse models (a unique transgenic strain that is capable to endogenously produce omega-3 from omega-6).
Both preventative and therapeutic effects of omega-3 on pulmonary and systemic inflammation as well as oxidative stress were examined.
This research showed for the first time, direct evidence that accumulated PM2.5 particles could penetrate lungs and translocate to other organs.
A novelty of the study is the utilization of non-toxic, fluorescent, synthetic PM2.5 particles as an experimental model, which allowed us to eliminate the influence of toxins and contaminants and thus to emphasize the pathological impact of the particle size alone.
Another aspect of the study is utilization of fat-1 mouse model to increase tissue levels of omega-3 endogenously and thus eliminating dietary confounding factors commonly found in nutrition research.
PM2.5 not only precipitate in lungs, but also can translocate to other organs, consequently inducing both pulmonary and systemic inflammation and oxidative stress.
Mice with a balanced ratio of tissue omega-6/omega-3 (either from endogenous production or dietary supplementation) exhibited a significant reduction of inflammation and oxidative stress, the two underlying pathological factors for chronic diseases.
These findings suggest that omega-3 supplementation can be a safe and highly effective means for prevention and treatment of PM2.5-induced health problems.
Given that air pollution nowadays is increasingly prevalent and severe, while to curb air pollution is a long-term project, this study is very meaningful in that it not only provides a strong rationale for the systemic adverse effects of PM2.5, but also suggests omega-3 supplementation as a safe and effective method for reducing risk of PM2.5-induced health problems.
Future translational studies can be done in human to test the utility of omega-3 in the management of air pollution-induced diseases.
The results of this study can also help establish nutrition guidelines for the public to reduce risk of air pollution-induced diseases by increasing tissue levels of omega-3 through daily consumption of more oily fish, leafy vegetables, and nuts and seeds—specifically walnuts, chia seed and flaxseed.
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