A new study from Ohio State University has found that animals exposed to air pollution had more fat cells and higher blood sugar levels than animals eating the same diet but breathing clean air.
The researchers exposed mice to polluted air for six hours a day, five days a week for 10 weeks beginning when the animals were 3 weeks old. This time frame roughly matches the toddler years to late adolescence in humans. The exposure levels for the animals subjected to polluted air resemble the fine-particulate pollution that can be found in urban areas in the United States.
The mice were fed either a normal diet or a high-fat diet and exposed to either filtered air or air containing fine particulates.
After exposing the animals to polluted or filtered air for 10 weeks, the researchers analyzed the mice for a number of risk factors associated with obesity and insulin resistance, the hallmark of Type 2 diabetes.
As expected, the mice on the high-fat diet gained much more weight than those on the normal diet. But mice exposed to polluted air and eating the normal diet had more significant elevations in glucose - sugar in their blood - than did normal-diet mice that breathed clean air. They also showed more signs of insulin resistance based on an index that measures both sugar and insulin in the blood at the same time.
Mice exposed to pollution - regardless of which diet they ate - also had higher blood levels of tumor necrosis factor-alpha, a protein involved in systemic inflammation, than did mice breathing clean air.
In addition, both abdominal and subcutaneous types of fat were increased with exposure to pollution in mice, even in animals that ate the normal diet. Mice eating a high-fat diet also had more fat, but their exposure to polluted air did not exacerbate those effects.
"These findings suggest that fine particulate pollution exposure alone, in the presence of a normal diet, may lead to an increase in fat cell size and number, and also have a inflammatory effect," said Sanjay Rajagopalan, senior author of the study.
The researchers do not yet know whether these effects would be sustained over adult life if air quality circumstances were changed, or if they are otherwise reversible. The research team now plan to continue studying the effects of fine particulate pollution on health, and have designed a study in humans that will take place in Beijing, China.
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Source: Ohio State University