Scientists find
potential protein biomarkers for growth hormone
SAN FRANCISCO – Ohio University scientists have identified several
proteins in mice that might act as biomarkers for growth hormone.
The research could be the first step to finding a more reliable way
to detect recombinant human growth hormone (rhGH), which some
athletes and teenagers use illegally to boost muscle and reduce fat.
 At
the Endocrine Society annual meeting in San Francisco on Tuesday
June 17, scientists John Kopchick and Juan Ding presented a new
study
that pinpointed four proteins that significantly decreased or
increased in the blood after exposure to bovine growth hormone,
which is similar to human growth hormone.
The researchers injected six 6-month-old male mice with growth
hormone
for seven days. They studied blood samples from the mice and
compared the results to six control animals. Kopchick and Ding
scanned hundreds of plasma proteins and found four—apoA1,
transthyretin, clusterin and albumin—that showed a strong reaction
to growth hormone.
“They’re in the blood, but we don’t know if they’re coming from
liver, fat, muscle or the kidneys,” said Kopchick, Goll-Ohio
Professor of Molecular Biology with Ohio University’s Edison
Biotechnology Institute and College of Osteopathic Medicine.
Kopchick and Ding, a graduate student in biological sciences, are
hopeful that the proteins could be viable biomarkers for growth
hormone activity in humans as well.
“In mice we can control the variables and the environment, but
humans are genetically diverse and have different lifestyles that
impact growth hormone. So the results may point to future study in
humans, but may not necessarily apply to humans yet,” said Ding, who
also is studying how to identify protein biomarkers for human aging.
Growth hormone is hard to detect because it has a serum half life of
only 15 minutes. RhGH, an approved drug for individuals with growth
hormone deficiency, also is identical to human growth hormone. The
current method of detecting growth hormone, analyzing levels of
insulin-like growth factor (IGF-1), isn’t always accurate, the
researchers said, as it is age and gender sensitive.
“If you have an 18-year-old Olympic athlete and a 38-year-old
athlete, the IGF-1 values may look very different,” said Kopchick,
whose research is funded by the National Institutes of Health, World
Anti-Doping Agency, Ohio Eminent Scholars program and Ohio
University’s Edison Biotechnology Institute.
Because identification of rhGH misuse or abuse has high stakes – it
can make or break an athletic career – the current method has too
many variables to depend on, he said.
It’s still early to tell whether these protein markers have the same
age limitations, as the mice in the study live to only 2 years. But
the markers may have longer half lives of several days, which would
offer a wider testing window, he said.
Kopchick already is exploring how to detect rhGH in human blood and
tissues through a project with Danish scientist J.O. Jorgensen. The
team received a three-year grant from the World Anti-Doping Agency
to look for protein markers in blood and tissues of human subjects
exposed to rhGH or exercise, as well as patients with growth hormone
disorders. |
