Estrogen's role in fat loss

[Guest guest]

Revealing Estrogen's Secret Role In Obesity

http://www.sciencedaily.com/releases/2007/08/070820145348.htm

Science Daily - New research on the effects of the female sex hormone

estrogen

in the brain lend credence to what many women have suspected about the

hormonal

changes that accompany aging: Menopause can make you fat.

In a demonstration of estrogen's role in controlling body weight and fat

distribution, these adult female rats both received surgery to induce

post-menopausal conditions. The smaller one received estrogen supplements

following surgery while the obese rat did not. (Credit: Courtesy of

Min Liu,

University of Cincinnati Academic Health Center)

Scientists long have sought to understand how changes in hormones during

menopause could account for the increase in appetite and accompanying

weight

gain that often occurs among aging women.

In a series of animal experiments described August 20 at the 234th

national

meeting of the American Chemical Society, researchers showed how estrogen

receptors located in the hypothalamus serve as a master switch to

control food

intake, energy expenditure and body fat distribution. When these

receptors are

destroyed, the animals immediately begin to eat more food, burn less

energy and

pack on pounds.

This research seems to support a link between estrogen and regulation of

obesity, especially the dangerous accumulation of abdominal fat linked

to heart

disease, diabetes, and cancer, says Deborah J. Clegg, Ph. D., assistant

professor of psychiatry at the University of Cincinnati Academic

Health Center,

who is directing the studies.

The findings may also help scientists develop more targeted hormone

replacement

therapies, capable of stimulating estrogen receptors in one part of

the brain or

body while dampening it in the next, Clegg says.

Estrogen receptors are located on cells throughout a woman's body.

Previous

studies have shown that one type of estrogen receptor, known as estrogen

receptor alpha or ER-alpha, plays a role in regulating food intake and

energy

expenditure. But scientists have been unable to pinpoint exactly where

these

fat-regulating receptors reside or how they work to govern these

behaviors.

To determine the effect of dwindling estrogen levels in the brain,

Clegg and her

colleagues are focusing on two ER-alpha rich regions located in the

hypothalamus, an area of the brain that controls body temperature,

hunger and

thirst. The first region, called the ventromedial nucleus or VMN, is a key

center for energy regulation.

Using a relatively new gene-silencing technique called RNA

interference, the

researchers in earlier research deactivated the alpha-receptors in the

VMN. The

estrogen receptors in other regions of the brain maintained their normal

capacity.

When estrogen levels in the VMN dipped, the animals' metabolic rate

and energy

levels also plummeted. The findings show the animals quickly developed an

impaired tolerance to glucose and a sizable weight gain, even when

their caloric

intake remained the same. What's more, the excess weight went straight

to their

middle sections, creating an increase in visceral fat.

The findings suggested that the ER-alpha in this region plays an

essential role

in controlling energy balance, body fat distribution and normal body

weight.

Clegg now plans to perform a similar experiment to deactivate ER-alpha

in the

arcuate nucleus region of the hypothalamus. This region contains two

populations

of neurons: one puts the brake on food intake and the other stimulates

food

intake. Clegg anticipates that a loss of estrogen in this region may

create an

increase in the animals' appetites as well as their weight.

Clegg says her studies address an area that is sorely needed given the

incidence

and impact of gender differences in obesity and its complications.

" The accumulation of abdominal fat puts both men and women at a

heightened risk

of cardiovascular disease, diabetes, and insulin resistance, " she

says. " Women

are protected from these negative consequences as long as they carry their

weight in their hips and saddlebags. But when they go through

menopause and the

body fat shifts to the abdomen, they have to start battling all of

these medical

complications. "

By identifying the critical brain regions that determine where body fat is

distributed, Clegg says her findings may help scientists design hormone

replacement therapies to better manage and manipulate estrogen levels.

" If we could target those critical regions and estrogen receptors

associated

with weight gain and energy expenditure, we could perhaps design

therapies that

help women sidestep many of the complications brought on by the onset of

menopause, " she says.

Note: This story has been adapted from a news release issued by American

Chemical Society.