When female mice are exposed to bisphenol A (BPA), a chemical found in plastics, or to ethinyl estradiol (EE), the estrogen in birth control pills, their daughters exercise less and have slower metabolisms.
Both BPA and EE disrupt hormone (endocrine) systems and are thought to cause tumors, birth defects, and developmental disorders in mammals.
“Mice exposed to endocrine disruptors move around less, are more likely to sleep, and engage in less voluntary physical activity,” says Cheryl Rosenfeld, associate professor of biomedical sciences at the University of Missouri.
The findings are published in the Journal of Developmental Origins of Health and Disease.
To test the chemicals’ impact on metabolism and activity, researchers exposed mice to BPA and EE in the womb and during weaning through the mother’s diet. A third group of mice whose mothers were placed on a control diet were not exposed to either chemical. At weaning, all the mice were placed on the same control diet and the scientists measured their energy expenditure, body composition, and level of voluntary physical activity as adults.
To further test the effects of voluntary exercise, the lab rigged bicycle computers to “hamster wheels” to track how far, fast, and for how long the mice ran. Researchers monitored the mice by measuring oxygen consumption and carbon dioxide production, and tracked the rodents’ movements during the day and at night.
“Female mice exposed to BPA and EE were less active than the control mice,” Rosenfeld says. “They moved around less at night—when these mice are typically most active—and moved more slowly, drank less water, and spent more time sleeping.
“In addition, BPA-exposed females burned more carbohydrates relative to fats, as compared to control mice. This is similar to the difference between obese and slender humans. Many researchers believe that burning more carbohydrates relative to fats can lead to fats gradually accumulating in the body.”
The researchers currently are conducting follow-up studies to determine if the changes caused by exposure to BPA and EE predispose mice to obesity and other metabolic disorders.
“Our findings are significant because decreased voluntary physical activity, or lack of exercise, can predispose animals or humans to cardiovascular diseases, metabolic disorders, and even cancer,” Rosenfeld says.
Researchers from the University of Kansas collaborated on the study. The National Institutes of Health supported the work.
Source: University of Missouri