Scientists at the Weizmann Institute have discovered a protein in the brain that contributes to obesity, in a study whose findings appeared this week in the journal Cell Metabolism.
The protein primarily affected females, rather than males, according to Professor Ari Elson and his team of researchers at the Institute's Molecular Genetics Department.
Without it, female mice became slim and healthy. Males were unaffected.
The protein, tyrosine phosphatase epsilon (PTPe), blocks the messages from a hormone called leptin, a key player in body mass regulation.
PTPe responds to the leptin signal in the hypothalamus, a region of the brain that takes in assorted stimuli, including a wide variety of hormones, and which sends out messages of its own in the form of new hormones and nerve signals.
The hypothalamus also plays a vital role in regulating body mass – a complex balancing act that involves, among other things, the control of appetite and physical activity.
Leptin reduces appetite and increases physical activity – but people who are obese often have too much leptin circulating in their blood. According to the scientists, this happens because although the body produces the hormone at a normal level, cells in obese people become resistant to the hormone's effects – and more leptin is then generated to compensate.
The new research shows that PTPe plays a role in this resistance. Mice that were lacking the protein were highly sensitive to leptin.
“Interestingly enough,” said Elson, “the effect seems to be gender-specific. Male mice hardly benefited at all from the lack of PTPe, compared with the female mice.”
He added the finding could open up “whole new lines of inquiry in obesity studies.”