Do chemicals make us couch potatoes?
A University of Missouri study has found that when pregnant mice are exposed to environmental chemicals, their daughters have a decreased metabolism expressed as a lack of physical activity conducted later in life.
Endocrine disruptors contaminate and interfere with our hormones. They can cause tumors, birth defects and developmental disorders in mammals. And often, we find them in a variety of our consumer products, such as water bottles, dental fillings, and resins used to line metal food and beverage containers.
Now, a University of Missouri study finds strong evidence that these disruptors are essentially creating "couch potatoes" among female mice and could predict more metabolic complications. The work is published in the Journal of Developmental Origins of Health and Disease, Cambridge University Press, September 2015.
"We found that if we exposed mice to one of two common endocrine disruptors — bisphenol A (BPA) or ethinyl estradiol (EE), the estrogen in birth control pills — during development of the fetus, it later caused disruptions in voluntary physical activity once the mice became adults. Mice exposed to endocrine disruptors move around less, are more likely to sleep and engage in less voluntary physical activity."
Cheryl Rosenfeld PhD, Associate Professor of Biomedical Sciences, College of Veterinary Medicine, researcher in the Bond Life Sciences Center at University of Missouri.
To test the chemicals' impact on metabolism and activity, Rosenfeld's lab 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 and were thus not exposed to either chemical. At weaning, the scientists then placed all the mice on the same control diet and 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's energy expenditure 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. They moved around less at night — when 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, and many researchers believe that burning more carbohydrates relative to fats can lead to fats gradually accumulating in the body."
Cheryl Rosenfeld PhD, associate professor of biomedical sciences, College of Veterinary Medicine and Bond Life Sciences Center at University of Missouri.
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 adds.
Endocrine disrupting chemicals (EDC) have received considerable attention as potential obesogens. Past studies examining obesogenic potential of one widespread EDC, bisphenol A (BPA), have generally focused on metabolic and adipose tissue effects. However, physical inactivity has been proposed to be a leading cause of obesity. A paucity of studies has considered whether EDC, including BPA, affects this behavior. To test whether early exposure to BPA and ethinyl estradiol (EE, estrogen present in birth control pills) results in metabolic and such behavioral disruptions, California mice developmentally exposed to BPA and EE were tested as adults for energy expenditure (indirect calorimetry), body composition (echoMRI) and physical activity (measured by beam breaks and voluntary wheel running). Serum glucose and metabolic hormones were measured. No differences in body weight or food consumption were detected. BPA-exposed females exhibited greater variation in weight than females in control and EE groups. During the dark and light cycles, BPA females exhibited a higher average respiratory quotient than control females, indicative of metabolizing carbohydrates rather than fats. Various assessments of voluntary physical activity in the home cage confirmed that during the dark cycle, BPA and EE-exposed females were significantly less active in this setting than control females. Similar effects were not observed in BPA or EE-exposed males. No significant differences were detected in serum glucose, insulin, adiponectin and leptin concentrations. Results suggest that females developmentally exposed to BPA exhibit decreased motivation to engage in voluntary physical activity and altered metabolism of carbohydrates v. fats, which could have important health implications.
Sarah A. Johnson, a graduate student in Rosenfeld's lab, Charles Wiedmeyer, an associate professor in the Department of Veterinary Pathobiology in College of Veterinary Medicine at MU, and John Thyfault, an associate professor of molecular and integrative physiology at the University of Kansas Medical Center, collaborated on the study.
Editor's Note: For more on this story, please see: https://decodingscience.missouri.edu/2015/09/18/chemicals-and-couch-potatoes/
The study was supported by the National Institutes of Health NIH (Grants 5R21ES023150 and R01DK088940). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.
For a video on this story, please see: https://www.youtube.com/watch?v=P11GSN55AnI
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Sep 28, 2015 Fetal Timeline Maternal Timeline News News Archive