EMBARGOED FOR RELEASE UNTIL OCTOBER 10, 2006
Contact:
Christine Guilfoy
Office: (301) 634-7253
cguilfoy@the-aps.org
Longer-Lived Rodents Have
Lower Levels Of Thyroid Hormone
Virginia Beach,
Va (October 10, 2006) – The thyroid may play an important role in
longevity, with longer-lived rodents showing significantly lower levels of a
thyroid hormone that speeds metabolism, a new study has found.
The study further strengthens the theory that the
faster an animal’s metabolism, the shorter its life, and vice versa, said
Mario Pinto, the study’s lead author. The thyroid releases hormones that
regulate metabolic rate.
“Thyroid hormones are key regulators of metabolism and
have been widely implicated to influence longevity,” the authors wrote.
Pinto will present the study “Differential thyroid hormone activity in
rodents with different life spans” at a poster session Oct. 9 at
Comparative Physiology 2006: Integrating Diversity. The study was
carried out by Pinto and Rochelle Buffenstein, City College of New York.
Thyroid key to metabolic
rate
The thyroid gland produces thyroxine (T4)
which converts to triiodothyronine (T3) in the presence of
iodine. T3 is the active component of T4 and is the
key hormone in regulating metabolism, Pinto said. When an animal becomes
cold, for example, its body converts T4 to T3 to speed
metabolism and warm the body, he explained.
“Mice strains that exhibit extended longevity tend to
have lower thyroid hormone concentrations than shorter living strains,” the
authors wrote. “Significant declines in thyroid hormone correlate well with
enhanced maximum lifespan.”
The study compared the levels of these thyroid hormones
among four groups of rodents with different life spans: mice, guinea pigs,
Damara mole-rats and naked mole-rats. Mice live to about three and a half
years; guinea pigs live to six years; Damara mole-rats to 15 years; and
naked mole-rats to 28 years.
The animals were of different ages, but at comparable
points in their life spans. For example, the mole-rats, which live 28 years,
were two years old. The mice, which live about 3.5 years, were six months
old. The study determined the levels of T3 and T4 for
each animal.
T4 levels vary
There was a significant difference in T3
levels between the naked mole-rats and the guinea pigs, but not between any
of the other groups, Pinto reported. T4 levels varied
significantly between all of the groups. For example, the mice had twice as
much T4 as the Damara mole-rats and had and three times more than
that of the naked mole-rats, Pinto said.
“These hormone concentration differences correlate with
maximum species lifespan and suggest an important regulatory role of thyroid
hormone in longevity,” the researchers concluded.
Although the comparison between the longest-lived and
shortest-lived groups showed a difference in hormone concentrations in T4,
the non-active hormone, it did not show these results across the board in T3,
the active form of the hormone. Further research in this area using
larger sample sizes (numbers of rodents in each group) is needed to clarify
the role of these hormones in longevity, Pinto said.
* * *
The
American Physiological Society was founded in 1887 to foster basic and
applied bioscience. The Bethesda, Maryland-based society has 10,500 members
and publishes 14 peer-reviewed journals containing almost 4,000 articles
annually.
* * *
APS
provides a wide range of research, educational and career support and
programming to further the contributions of physiology to understanding the
mechanisms of diseased and healthy states. In 2004, APS received
the Presidential Award for Excellence in Science,
Mathematics and Engineering Mentoring.
|
