A DRUG that can make the body burn off calories without the need for
excessive exercise may be on its way.
Robert Dow of the pharmaceuticals company Pfizer鈥檚 laboratories in Groton,
Connecticut, told last week鈥檚 meeting of the American Chemical Society in San
Francisco that his team has made a molecule that can boost the metabolism of
rats by almost a third without increasing their appetites.
The molecule, called CP-331679, mimics one effect of adrenaline. This hormone
binds to three types of receptors: one in the heart, which boosts the heart
rate; another in blood vessels, which causes them to dilate; and the third on
the surface of fat storage cells, which causes fats to be broken down for
energy.
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Dow鈥檚 team targeted the third type, called beta-3 adrenergic receptors,
reasoning that this would help to burn fat without affecting the cardiovascular
system. The researchers tinkered with molecules known to stimulate adrenaline
receptors until they came up with one that affected just the beta-3
receptors.
Dow has not yet tested the molecule in humans, but if its effects on rats
were translated into human terms, people would shed just over a kilogram a week.
However, human fats occur in different proportions to those of rats, which could
limit the molecule鈥檚 effect. Dow鈥檚 molecule works on the brown fat of rats, of
which adult humans have very little.
David Kreutter, a member of the Pfizer team, stresses that overweight people
will always need to exercise. 鈥淣o drug should be considered a substitute for
lifestyle changes,鈥� he says.
Other drugs companies are also betting that beta-3 adrenergic stimulators
will improve on today鈥檚 diet pills. Merck of Rahway in New Jersey, for instance,
has a beta-3 adrenergic stimulator under development.