Hard To Build And Easy To Lose: How Aging Affects Muscle

[Guest guest]

Hard To Build And Easy To Lose: How Aging Affects Muscle

http://www.medicalnewstoday.com/articles/163821.php

Have you ever noticed that people have thinner arms and legs as they get older?

As we age it becomes harder to keep our muscles healthy. They get smaller, which

decreases strength and increases the likelihood of falls and fractures. New

research is showing how this happens - and what to do about it.

A team of Nottingham researchers has already shown that when older people eat,

they cannot make muscle as fast as the young. Now they've found that the

suppression of muscle breakdown, which also happens during feeding, is blunted

with age.

The scientists and doctors at The University of Nottingham Schools of Graduate

Entry Medicine and Biomedical Sciences believe that a 'double whammy' affects

people aged over 65. However the team think that weight training may

" rejuvenate " muscle blood flow and help retain muscle for older people.

These results may explain the ongoing loss of muscle in older people: when they

eat they don't build enough muscle with the protein in food; also, the insulin

(a hormone released during a meal) fails to shut down the muscle breakdown that

rises between meals and overnight. Normally, in young people, insulin acts to

slow muscle breakdown. Common to these problems may be a failure to deliver

nutrients and hormones to muscle because of a poorer blood supply.

The work has been done by Rennie, Professor of Clinical Physiology, and

Dr Emilie Wilkes, and their colleagues at The University of Nottingham. The

research was funded by the UK's Biotechnology and Biological Sciences Research

Council (BBSRC) as part of ongoing work on age-related muscle wasting and how to

lessen that effect.

Research just published in the American Journal of Clinical Nutrition compared

one group of people in their late 60s to a group of 25-year-olds, with equal

numbers of men and women. Professor Rennie said " We studied our subjects first -

before breakfast - and then after giving them a small amount of insulin to raise

the hormone to what they would be if they had eaten breakfast, of a bowl of

cornflakes or a croissant. "

" We tagged one of the amino acids (from which proteins are made) so that we

could discover how much protein in leg muscle was being broken down. We then

compared how much amino acid was delivered to the leg and how much was leaving

it, by analysing blood in the two situations.

" The results were clear. The younger people's muscles were able to use insulin

we gave to stop the muscle breakdown, which had increased during the night. The

muscles in the older people could not. "

" In the course of our tests, we also noticed that the blood flow in the leg was

greater in the younger people than the older ones, " added Professor Rennie.

" This set us thinking: maybe the rate of supply of nutrients and hormones is

lower in the older people? This could explain the wasting we see. "

Following this up led Beth , a PhD student working with Professor

Rennie, to win the Blue Riband Award for work she presented at the summer

meeting of The Physiological Society in Dublin. In her research Beth confirmed

the blunting effect of age on leg blood flow after feeding, with and without

exercise. The team predicted that weight training would reduce this blunting.

" Indeed, she found that three sessions a week over 20 weeks 'rejuvenated' the

leg blood flow responses of the older people. They became identical to those in

the young, " said Professor Rennie.

" I am extremely pleased with progress, " he said. " Our team is making good

headway in finding more and more out about what causes the loss of muscle with

age. It looks like we have good clues about how to lessen it with weight

training and possibly other ways to increase blood flow. "

The team's research, published in the American Journal of Clinical Nutrition,

can be accessed online at http://www.ajcn.org/papbyrecent.dtl " Blunting of

insulin inhibition of proteolysis in legs of older subjects may contribute to

age-related sarcopenia " by Emilie A Wilkes, L Selby, Philip J Atherton,

Rekha Patel, Debbie Rankin, Ken , and J Rennie, 2009 AmJ Clin Nutr

(In press).