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Cutting Calories Could Limit Muscle Wasting In Later Years
Cutting Calories Could Limit Muscle Wasting In Later Years
Iron accumulation in muscle cells of aging rats set in motion a series
of cellular events that causes muscle wasting. Iron levels were
maintained at more normal levels in rats on 40% CR.
Link:
http://www.scienced aily.com/ releases/ 2008/09/08091621 5209.htm
Text:
Cutting Calories Could Limit Muscle Wasting In Later Years
ScienceDaily (Sep. 19, 2008) — Chemical concoctions can smooth over
wrinkles and hide those pesky grays, but what about the signs of aging
that aren't so easy to fix, such as losing muscle mass? Cutting
calories early could help, say University of Florida researchers who
studied the phenomenon in rats.
A restricted-calorie diet, when started in early adulthood, seems to
stymie a mitochondrial mishap that may contribute to muscle loss in
aging adults, the researchers reported recently in the journal PLoS One.
In rats, the scientists found pockets of excess iron in muscle cell
mitochondria, the tiny power plants found in every cell. The excess
iron affects the chemistry inside the mitochondria, sparking the
formation of harmful free radicals that can lead a mitochondrion
straight to the emergency exit, said Christiaan Leeuwenburgh, Ph.D., a
UF professor of aging in the UF College of Medicine and the Institute
on Aging. Leeuwenburgh was the senior author of the study and of a
related report published online this month in Aging Cell that details
the damage done by excess iron in mitochondria.
"We become less efficient at an old age and we need to understand why
this is," Leeuwenburgh said. "One thing, maybe, is the accumulation of
redox-active metals in cells. If the mitochondria become unhappy or
are ready to kick the bucket, they have proteins in the inner and
outer membranes that they can open up and commit suicide. They're
tricky beasts."
The suicidal mitochondria can damage the rest of the muscle cell,
leading to cell death and perhaps to muscle wasting, a big problem for
adults as they reach their mid-70s, Leeuwenburgh added.
"Muscle is critical for your overall well-being," Leeuwenburgh said.
"As you walk, muscle functions partly as a pump to keep your blood
going. Muscle is an incredible source of reserves."
The researchers found increasing amounts of iron in the muscle cells
of aging rats fed a typical unrestricted diet. The older the rats got,
the more iron accumulated in the mitochondria and the more damage was
done to its RNA and DNA. Rats of the same ages that were kept on a
calorie-restricted diet — about 60 percent of the food typically
ingested — seemed to maintain more normal iron levels in mitochondria,
the researchers reported.
"The novel thing here is that iron is accumulating in places it does
not normally accumulate," said Mitch Knutson, Ph.D., a UF assistant
professor of food science and human nutrition and a study co-author.
"Such iron accumulation in muscle was quite unexpected. This may be of
concern because more people are genetically predisposed to developing
iron overload than we originally thought."
The problem occurs when metals such as iron accumulate in the
mitochondria and react with oxygen. Iron can change the chemical
structure of oxygen, triggering its metamorphosis into a free radical,
an unstable atom that can upset the delicate balance inside the
mitochondria. The result? Leeuwenburgh describes it sort of like
internal rust.
"Not all free radicals are harmful," Leeuwenburgh said. "To just use
antioxidants to neutralize all free radicals is a huge misconception
because some radicals are helpful. You just need to try and target
very specific free radicals that form in specific parts of the body."
Researchers don't know exactly what causes iron to accumulate in
mitochondria in aging animals, but a breakdown in how iron is
transported through cells could be one reason why, Leeuwenburgh said.
Understanding how caloric restriction limits the problem in rats could
help researchers better understand how to combat it, he added.
Russell T. Hepple, Ph.D., an associate professor of kinesiology and
medicine at the University of Calgary in Canada, said the findings are
another step forward in linking iron to muscle cell death, but there
are more questions researchers must answer.
"They've shown that apoptosis (cell death) goes up in aging muscle but
where does that happen?" Hepple asked. "There are more than muscle
cells in muscle. (For example) in older adults there are inflammatory
cells."
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