Newswise — Even at very low doses, endocrine-disrupting chemicals (EDCs) that mimic the action of naturally occurring estrogens impair the body's secretion of glucagon, according to a study accepted for publication today by the peer-reviewed journal Environmental Health Perspectives.
Glucagon is released by alpha cells in the pancreas. It provides the major counter-regulatory mechanism for insulin by stimulating the liver to produce glucose and maintaining proper glucose levels in the blood. It also has a crucial role in inducing the breakdown of fat and the release of fatty acids from tissue when blood glucose is low. Glucose is needed by the body to produce energy; when glucose metabolism is impaired, obesity and type 2 diabetes mellitus may result.
Earlier studies found that insulin-releasing beta cells were affected by low concentrations of the EDCs bisphenol A (BPA) and diethylstilbestrol (DES); the present study found a similar impact on glucagon-releasing alpha cells. The study found that the EDCs binds to a nonclassical membrane estrogen receptor and acts the same as naturally occurring estrogens.
BPA is found in polycarbonate plastic, the lining of food cans, and dental sealants. A bill introduced recently in the California legislature seeks to ban the use of BPA in plastic products made for babies and toddlers, while the plastics industry maintains that it is safe. DES is a synthetic estrogen used between the 1940s and the 1970s to prevent miscarriages. This study shows the first evidence of a disruption of pancreatic alpha cells by these endocrine disruptors.
In the study, researchers collected freshly isolated whole islets of Langerhans, which are the physiological unit of the endocrine pancreas that produces both insulin and glucagon. The researchers evaluated the islets with fluorescent calcium-sensitive dye using laser scanner confocal microscopy. While the tests were done in vitro using extracted cells, the researchers expect the same levels of BPA and DES to have similar response in vivo.
This suggests that glucagon levels in the bloodstream could be affected by low levels of BPA and DES, which in turn may "connect BPA with obesity through the disruption of alpha cells," said study coauthor Angel Nadal.
The lead author of the study was Paloma Alonso-Magdalena of the Institute of Bioengineering at Miguel Hernandez University in Alicante, Spain. Other authors included Nadal, Ouahiba Laribi, Ana B. Ropero, Esther Fuentes, Cristina Ripoll, and Bernat Soria. Funding sources for the research as reported by the authors included grants from the Spanish Ministry of Education and Science and the Instituto de Salud Carlos III. The article is available free of charge at http://ehp.niehs.nih.gov/docs/2005/8002/abstract.html.
EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org/. Brogan & Partners Convergence Marketing handles marketing and public relations for the publication, and is responsible for creation and distribution of this press release.
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Environmental Health Perspectives (May-2005)