Cutting Calories Could Limit Muscle Wasting In Later Years

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Cutting Calories Could Limit Muscle Wasting In Later Years

http://www.medicalnewstoday.com/articles/121719.php

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.

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. "