Eating
Disorders
Weighty Research Links Hormone to the Drive to Eat
(April 3, 2004) - Scientists are a step closer to understanding why it is so
hard to lose weight.
In papers published in Science, two research teams describe newly discovered
powers of leptin, the mysterious hormone that helps govern
hunger and satiety.
It appears that the substance plays a crucial role in establishing the brain's
circuitry before birth, and retains the ability to subtly rewire those neural
connections throughout life.
Those observations, made in mice but thought to apply also to human beings,
offer a peek at the cellular workings of the
drive to eat. They also
shed light on why many people seem to have a physical "set point" - a weight
their body seeks to maintain despite a person's efforts to change it.
When leptin is released by fat cells into the bloodstream, it works to
suppress appetite. A deficiency of the hormone leads to
overeating
and obesity.
Scientists at Rockefeller University in New York examined two brain pathways
in adult mice: one increases appetite and another decreases it.
They looked at so called NPY cells, brain cells that stimulate feeding. In
normal animals there were more inhibiting than stimulating connections to these
cells from other cells. In mice that are genetically incapable of making leptin,
that situation was reversed.
The effect of this was to make the leptin-deficient mice eat more and make
more fat cells in a futile effort to make leptin.
In a second study, scientists at Oregon Health & Science University found
exposure to leptin early in life affected brain structures involved in weight
regulation.
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