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.
The Washington Post, The New York Times, Reuters