New study illuminates how estrogens help regulate eating, drinking

BUFFALO, N.Y. – A research study by behavioral neuroscientists at the University at Buffalo offers new information about how ovarian hormones, in particular the powerful estrogen estradiol, help to regulate eating and drinking behaviors.

The study also offers new information about biological processes that underlie sex differences in obesity and cardiovascular disease and has implications for research on treatments for many other estrogen-related maladies.

The study, “Activation of Membrane-Associated Estrogen Receptors Decreases Food and Water Intake in Ovariectomized Rats,” is published in the current issue of the journal Endocrinology (Vol. 154, no. 1, Jan. 2013).

The authors are members of the Behavioral Neuroscience Program in the UB Department of Psychology: Postdoctoral Fellow Jessica Santollo, PhD; Research Specialist Anikó Marshall; and Derek Daniels, PhD, associate professor of psychology and director of the behavioral neuroscience doctoral program.

They point out that eating and body weight ebb and flow with other changes in estrogen, such as those that occur during and after menstruation, pregnancy and menopause in women using certain kinds of birth control, and in patients undergoing estrogen therapy.

Daniels says, “Estrogens have well-known influences not only on mood and sexual function, but also on appetite, eating and where we store fat.”

One form of estrogen – estradiol (E2) – has especially powerful estrogenic effects, one of which is that it decreases water and food intake in a variety of species, including rats.

Santollo points out that this process is mediated by genomic mechanisms most often attributed to intracellular nuclear estrogen receptors (ERs).

“Recent studies indicate that other receptors – membrane-associated estrogen receptors (mERs) – located on the surface of cells also can influence gene expression,” she says, “but it has been unclear whether these receptors also mediate the appetite and water-intake suppression effects of E2.

“This study found that they do,” she says.

“Although we do not yet have the tools to put into the brains of humans estrogens that activate only the membrane ERs,” Daniels says, “studies like these in rats are an important step toward developing drugs that are more selective for different groups of receptors. This could lead to new treatments for the many, many disorders that involve estrogens.”

Although the present study provides support for a role of mER in ingestive behavior, further research is necessary to determine which membrane-associated receptor type is responsible for the observed effects, the researchers say.

“The more we understand how estrogen affects the nervous system,” says Santollo, “the more accurately we can guide the development of new estrogen therapies, to deal with weight gain in women, particularly women in menopause.

“Our study focused only on female rats so we don’t know if these results would apply to males as well,” she adds.

“Men have estrogen receptors and we know that treating male rodents with estradiol decreases their eating, but some studies demonstrate important differences in how membrane estrogen receptors work in males and females, so this is an area for future study.”