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2005/06/11
Leptin is a hormone produced
by fat that appears to play an important role in keeping
food intake and energy expenditure
in balance, so weight is maintained at a steady level.
It is
released when a person has eaten enough food to meet their
needs, suppressing appetite and producing the feeling of "satiety",
or fullness.
It does this by bonding with receptors in an area
of the brain called the hypothalamus.
Injections
Injections
of the hormone given to morbidly obese people have helped them
to shed weight.
However, research has also shown that some
obese people appear to be resistant to the hormone's effects,
despite having high concentrations in their bloodstream.
Evidence
has also suggested that a neonatal surge of leptin, which occurs
early in the life of newborns, may play an important role in
the formation of energy-regulating brain circuits in the hypothalamus.
In the latest study, mice born of mothers who ate 30% less
than normal were small at birth and had less fat.
However,
the under-nourished newborns caught up with normal mice after
10 days and, when fed a high-fat diet, developed pronounced
weight gain and increased leptin levels compared to normal
mice on the same diet.
The under-nourished mice had lower body
temperatures than normal mice - suggesting they had been programmed
to conserve energy.
Early surge
Analysis showed that the surge
in leptin levels occurred six to eight days earlier than normal
in the under-nourished animals.
When the researchers mimicked
that premature leptin surge by administering the hormone to
normally-fed mice, those animals also became prone to obesity
upon eating a diet high in fat.
The researchers found premature
exposure to a leptin surge seemed to impair the body's ability
to transport the hormone around the brain.
They also found
these mice were more likely to have abnormalities in the hypothalamus.
Researcher Dr Shingo Fujii said: "The present study suggests
that a premature surge of leptin as a result of foetal under-nourishment
can alter energy regulation by the brain and contribute to
developmental origins of health and disease."
Dr Simon Langley-Evans,
an expert in human nutrition at Nottingham University, said: "This
theory is very feasible. There is now quite a lot of data to
show that prenatal under-nutrition does have a long-term impact
on many disease states."
He said animal studies had shown that
the pre-natal diet had a profound impact on later eating behaviour.
For instance, rats fed a low protein diet in the womb showed
a heightened desire to eat fat.
Other research had shown that
a low protein diet led to changes in the density and type of
cells in the hypothalamus.
Story from BBC NEWS
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