Here's a Science summary:
Friday, 3 January 1997, 6:00 p.m.
Hormone Offers Mice Fat Chance at Puberty
Leptin, a hormone that became famous in 1994 for its potential antiobesity effects, may
also play a
key role in the onset of puberty in mice, says a report in today's Science magazine.
Scientists have assumed that girls must achieve a threshold fat level in order to enter
puberty. The
new findings build on that hypothesis, says Farid F. Chehab, a researcher at the
University of
California, San Francisco (UCSF), and lead author of the study. Chehab suggests that
leptin
released by adipose tissue tells the body it has sufficient fat reserves to enter puberty
and the
reproductive years.
Chehab's work on prepubescent, healthy female mice was spurred by his observation
that leptin
could restore fertility in obese mice that had previously been sterile. After injecting 13
mice daily with
leptin and administering a saline solution daily to 12 control mice, the UCSF
researchers found that
the leptin group entered its first estrous cycle sooner, had more advanced reproductive
tracts, and
reproduced up to 9 days earlier than the control mice. Similar results were reported
late last year at
the Society for Neuroscience meeting by endocrinologist Jeffrey Flier and colleagues at
Beth Israel
Hospital in Boston. (See ScienceNOW, 20 November.)
The results confirm that leptin "can initiate the cascade of events that leads to
reproduction," Chehab
says. The next question, he says, is understanding its relationship to the other factors in
the
reproductive cycle.
That question is controversial. While Chehab speculates that leptin acts directly on the
brain, other
researchers are looking elsewhere in the body. Scientists at Progenitor Inc., a
Columbus, Ohio,
biotechnology firm, for example, have found leptin receptors on the reproductive
organs. "If the
receptors are there, they should be doing something," says Joseph Cioffi, the
company's director of
genomics.
Leptin researchers are now exploring the possible routes by which the hormone
influences
reproductive maturity. In the meantime, says Robert Steiner, a leptin researcher at the
University of
Washington, the Chehab study offers "compelling testimony that leptin is certainly more
than a simple
satiety factor." |
