Learning How Muscles Weaken With Age May Lead to
Other Answers About Aging
Unexpected change of ‘set
point’ in nervous system tied to loss of motor function; may explain
other aging changes
Feb. 6, 2014 – The
mystery of why our muscles just get weaker as we age seems to have an
answer that involves the “set points” in our nervous system. For
example, the set point for body temperature is 98.6 degrees. These
points are not as set as we assumed. A new study finds they can be reset
with age, and the researchers observed a set point that resulted in
significantly diminished motor function in aging fruit flies.
Scientists from the
School of Medicine at The University of Texas Health Science Center at
San Antonio have found this clue as to why muscles weaken with age. In a
study published today in The Journal of Neuroscience. They report
the first evidence that “set points” in the nervous system are not
inalterably determined during development but instead can be reset with
“The body has a set
point for temperature (98.6 degrees), a set point for salt level in the
blood, and other homeostatic (steady-state) set points that are
important for maintaining stable functions throughout life,” said study
senior author Ben Eaton, Ph.D., assistant professor of physiology at the
Health Science Center.
“Evidence also points to the existence of set
points in the nervous system, but it has never been observed that they
change, until now.”
Dr. Eaton and lead
author Rebekah Mahoney, a graduate student, recorded changes in the
neuromuscular junction synapses of aging fruit flies. These synapses are
spaces where neurons exchange electrical signals to enable motor
functions such as walking and smiling. “We observed a change in the
synapse, indicating that the homeostatic mechanism had adjusted to
maintain a new set point in the older animal,” Mahoney said.
The change was nearly
200 percent, and the researchers predicted that it would leave muscles
more vulnerable to exhaustion.
Aside from impairing
movement in aging animals, a new functional set point in neuromuscular
junctions could put the synapse at risk for developing neurodegeneration
— the hallmark of disorders such as Alzheimer’s and Parkinson’s
diseases, Mahoney said.
“Observing a change in
the set point in synapses alters our paradigms about how we think age
affects the function of the nervous system,” she said.
It appears that a
similar change could lead to effects on learning and memory in old age.
An understanding of this phenomenon would be invaluable and could lead
to development of novel therapies for those issues, as well.
Joel Rawson, Ph.D., of
the University of Alaska at Anchorage, formerly a postdoctoral fellow in
Dr. Eaton’s lab, is a study co-author.
The University of
Texas Health Science Center at San Antonio, one of the country’s
leading health sciences universities, ranks in the top 3 percent of all
institutions worldwide receiving National Institutes of Health funding.
The university’s schools of medicine, nursing, dentistry, health
professions and graduate biomedical sciences have produced more than
29,000 graduates. The $765 million operating budget supports eight
campuses in San Antonio, Laredo, Harlingen and Edinburg. For more
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