UCLA study reveals leptin’s effect on human health and development
By Emily Leung
Aug. 11, 2002 9:00 p.m.
Since its discovery almost a decade ago, the believed benefits
of the “anti-obesity hormone” called leptin has
fluctuated back and forth.
The hormone first caused a stir when scientists announced they
could cause fat mice to lose weight by injecting them with the
weight-regulating hormone.
But then, as a panacea for human obesity, it failed.
Now, new evidence from a study conducted by a team of doctors
headed by Dr. Julio Licinio, a professor of medicine at the David
Geffen School of Medicine at UCLA shows leptin to be even more
important to human health and development than previously
believed.
“This was a small study, but it produced striking results
and exponentially increased our knowledge of leptin and its role in
the human body,” said Licinio.
“The best way to do this is to see what leptin does to
(the leptin deficient patients’) bodies because it would tell
us what leptin does to my body and your body,” he added.
Injecting the leptin protein-hormone to normal humans would do
nothing since humans naturally produce this hormone already,
according to Licinio.
The study conducted by Licinio focused on three patients, one
man and two women, who are the only known adults in the world who
possess a rare genetic mutation that prevents their bodies from
naturally producing leptin.
Secreted by adipocyte tissue, leptin tells the brain when humans
are full and to stop eating.
Typically, obese individuals are insensitive to the hormone
because they have up to four times the levels of leptin than
non-obese individuals and become insensitive to the hormone.
In these patients, the doctors found important results and few
side effects ““ just a minor rash at the injection site.
Ten months after the study began, the patients lost half of
their body weight ““ more than 150 pounds each.
The leptin therapy also resulted in dramatic outcomes beyond
their weight loss, including psychological and personality
changes.
“The patients’ personality changes suggest that
there is a relationship between fat and how we feel,” said
Licinio.
The researchers noticed the patients grew noticeably more
assertive and independent. Other findings involved leptin’s
association to sexual maturity and homeostatic regulation.
The effects of leptin for one 27-year-old patient in the study
only served to solidify the optimism the hormone therapy
induced.
“The man was sexually immature ““ no beard, no facial
or body hair,” Licinio said, referring to the male patient.
“But he basically underwent puberty at the age of
27.”
“I feel wonderful,” said the patient, speaking
through an interpreter. “I feel very light and everything is
beautiful to me right now.”
He went from 313 pounds to 165 pounds.
Prior to the leptin treatment, the patient said he “was
unhappy and very, very heavy and I couldn’t carry my own
body. I’m very happy someone found out about this
medicine.”
The other two female patients in the study had sporadic
menstrual cycles prior to treatment. After the 10-month treatment,
their cycles came at regular intervals.
In addition to playing a role in sexual development and
regulating hormones, this is the first known instance of brain
growth in adults. MRI scans showed very small, but still
significant size increase.
However, it should be cautioned that treatment for obesity down
the line is still “unknown”, according to Anthony
Wagner, Ph.D, of Amgen Inc, the pharmaceutical company which
developed and provided leptin for the UCLA study.
“By doing these types of studies … we’re able to
understand the mechanism and action of leptin in a better way,
which would then translate into what would determine an appropriate
application,” Wagner said.
The role that leptin plays in the cause of obesity remains its
most lucrative and offers great potential in medication for
treating obesity.
According to the U.S. Centers for Disease Control and
Prevention, more than 22 percent of Americans are obese.
In addition, weight-loss products and services make up a $33
billion-a-year industry said the CDC.
There are currently 15 drugs for treating obesity which are in
human clinical trials or about to begin, according to a recent
study by Marketdata Enterprises Inc., a market research firm.
One of these hormones is PYY3-36 ““ secreted by the
intestines ““ which was recently determined to reduce
long-term appetite in humans after a 12-person study in
England.
Although the expanding discovery and knowledge of appetite
hormones has led to much anticipation concerning obesity
treatments, there are still “many hurdles” to
overcome.
The UCLA study’s patients are in a very specific subset of
the obese population, but they had tremendous medical benefit.
“Further research would be needed to broaden the
application and more time are always a good idea,” said
Wagner.
