obese people large fat 311 (R).
(photo credit: Reuters)
If you are very overweight and always thought it was something in your head, you
were right – but it is not just psychological; it is something in a small part
of the brain. Weizmann Institute of Science researchers have added another piece
to the obesity puzzle, showing how and why a certain brain protein contributes
to weight gain. Their work was published in Cell Metabolism.
Elson and his team in the Rehovot institute’s molecular genetics department made
the discovery when working with female mice that were genetically engineered to
lack protein tyrosine phosphatase epsilon (PTPe). As the scientists had
originally intended to investigate osteoporosis, they also removed the rodents’
ovaries. Oophorectomy typically causes mice to gain weight to the point of
obesity – so the scientists were surprised to find that the weight of the
genetically-engineered mice remained stable. Working with Dr. Alon Chen and his
group in the neurobiology department and Prof. Hilla Knobler, head of the unit
of metabolic disease and diabetes of Kaplan Medical Center in Rehovot, the
researchers fed these mice a high-fat diet, yet the PTPe-deficient mice
maintained their svelte figures; they burned more energy and had more stable
glucose levels as well.
To find out how the lack of this protein could
keep mice slim and healthy, the scientists looked at the hypothalamus – a region
of the brain that takes in assorted stimuli, including a wide variety of
hormones, and sends out messages of its own in the form of new hormones and
nerve signals. The hypothalamus plays a vital role in regulating body mass – a
complex balancing act that involves, among other things, controlling appetite
and physical activity.
Elson and his team found that PTPe blocks the
messages from a now-well-known hormone called leptin – a key player in body mass
regulation. They revealed exactly how it does this: PTPe responds to the leptin
signal in the hypothalamus, inhibiting certain molecules, which in turn dampens
Among leptin’s activities is that it reduces appetite and
increases physical activity. Paradoxically, obese people often have a surfeit of
leptin in their blood. This is because, while their bodies produce the hormone
normally, their cells become resistant to its effects, and more leptin is
generated to compensate. The new research shows that PTPe plays a role in this
resistance. The team found that mice lacking the protein were highly sensitive
to leptin; and they remained so despite aging, ovary removal or high-fat diets.
This suggests that in obese humans with leptin insensitivity, inhibiting PTPe
might, conceivably, help reestablish the leptin response and induce weight loss.
This, however, requires further research to ensure that it acts in the same way
in humans, with no dangerous side-effects.
Elson noted: “Interestingly
enough, the effect seems to be gender-specific. Male mice hardly benefitted from
the lack of PTPe compared with female mice. This finding could open up whole new
lines of inquiry in obesity studies.”
HELPING AIDS CARRIERS BECOME
PARENTS Having HIV, which is serious but has become a chronic disease, is not
the end of the world. In fact, it could lead to the beginning of life. Four
successful pregnancies were recently produced for still-healthy carriers by
doctors at Jerusalem’s Hadassah University Medical Center . So far, 45 couples
have registered for the new project for fertility in HIV carriers.
JPOST VIDEOS THAT MIGHT INTEREST YOU:
Keren Olstein, who coordinates it and follows up couples through the whole
process, said success “is a dream-come-true for us” as well as the
The women are healthy; their male partners are HIV carriers. To
be accepted by the project, the couples must have taken the HIV drug cocktail of
protease inhibitors for at least six months and present at least two tests with
documentation of a low viral load in their immune systems. Then, the man gives a
semen sample that is carefully rinsed in a Hadassah lab to remove all signs of
the potentially deadly virus. If virology tests show there is no HIV in the
semen, it is injected into the woman’s womb when she has ovulated. Prof. Shlomo
Ma’ayan, head of the hospital’s AIDS clinic, initiated the project and receives
assistance from staff of the IVF Center and of the Virology Lab.
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