Jefferson Researchers Develop Blood Test to Determine Hormone Levels
Associated With Obesity
Researchers at Jefferson Medical College have created a blood
test to determine the level of leptin in humans. Leptin is the hormone product
of the obesity gene. Their findings, published in the January 31, 1996 New
England Journal of Medicine, indicate that obese individuals have higher
levels of leptin than persons who are lean. This research suggests that
obese persons who have high levels of leptin may have a decreased sensitivity
"We were able to make the association between leptin levels and obesity
by using a newly developed blood test, which enabled us to track leptin
in humans. This research is an important next step to narrowing down the
mechanisms that lead to obesity," explained José F. Caro, MD,
chairman of Jefferson's department of medicine and senior author of the
study. "By the same token, this information is equally important to
understanding why some people remain lean, while others develop obesity
later in life."
In the article, the Jefferson investigators report that several factors
may contribute to the elevation of leptin in obese individuals, but the
values were most closely correlated with the percentage of body fat. They
concluded that, at least in humans, leptin levels reflect the amount of
fat tissue in the body.
According to Dr. Caro, the human obesity gene appears to be involved in
the mechanism by which the increase in body fat translates into an increase
in leptin. Researchers found a significantly greater amount of the obesity
messenger protein in the fat cells of obese subjects than in normal-weight
Because this study concludes that many obese persons do have higher levels
of leptin, it appears that human obesity is more likely caused by errors
in the central mechanisms regulating food intake and energy expenditure.
Animal studies previously had indicated that human obesity could be caused
by a defect in the signals that are put forth by fat cells. However, this
study reconfirms that, in humans, the signal is working properly, but that
for reasons yet unknown, the brain is not adequately reading the signals.
Since leptin concentrations in the blood are related to body fat, this blood
test may help predict who will become obese.
Additionally, for people who are overweight, but whose leptin levels are
normal, treatment with additional leptin may become a therapy option, and
may be available within three years, Dr. Caro explained. For obese persons
whose leptin levels are high, researchers will need to pursue treatment
options that will allow the "stop eating" message to be properly
read by the brain.
"The blood test eventually will be available to the public," noted
Dr. Caro. "But the relationship between leptin and obesity certainly
needs further reference and study."