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Muscle - ‘hard to build, easy to lose’ as you age

Visit  The University of Nottingham website

9 September 2009

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 funded by BBSRC is showing how this happens – and what to do about it.

A team of Nottingham researchers has already shown that when they 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 Michael Rennie, Professor of Clinical Physiology, and Dr Emilie Wilkes, and their colleagues at The University of Nottingham. BBSRC funded the research as part of ongoing work on age-related muscle wasting and how to lessen that effect.

Research published today in The American Journal of Clinical Nutrition compared 1 group of people in their late 60’s 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 analyzing blood in the 2 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 Phillips, 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.”

ENDS

Notes to editors

The team’s research, published in The American Journal of Clinical Nutrition (AJCN), can be accessed online. More information about “Blunting of insulin inhibition of proteolysis in legs of older subjects may contribute to age-related sarcopenia” by Emilie A Wilkes, Anna L Selby, Philip J Atherton, Rekha Patel, Debbie Rankin, Ken Smith, and Michael J Rennie, 2009 AmJ Clin Nutr (In press), see the AJCN website: www.ajcn.org/papbyrecent.dtl. A text file of the paper can be obtained from Simon Butt (see External contacts below).

The award-winning poster Beth Phillips presented at the summer meeting of The Physiological Society entitled “In middle aged and old individuals 20 weeks of resistance training restores the increases of leg blood flow after acute exercise and feeding to values seen in young subjects” by Bethan Phillips, Wulf Hildebrandt, Ken Smith, Margaret Baker, Amanda Gates, Paul Greenhaff, Ian A Macdonald and Michael J Rennie.

About The Physiological Society

A learned society founded in 1876,with over 2,800 Members from over 50 countries. It is a charity with the aims to 'promote, for the benefit of the public, the advancement of physiology, and facilitate the intercourse of physiologists both at home and abroad, and thereby contribute to the progress and understanding of biomedical and related sciences and the detection, prevention and treatment of disease, disability and malfunction of physical processes in all forms of life.' It does this by among other things sponsoring scientific meetings like the one at Beth Phillips won the prize.

The grants from BBSRC were “Equipment to measure leg blood flow and tissue amino acids in determining the molecular basis of nutrient sensitivity of human muscle protein turnover, £72,270 to Michael J Rennie and Kenneth Smith; and “Overcoming the blunted response to food to maximize muscle maintenance in the elderly”, £1,305,715 to Michael Rennie, Kenneth Smith, Ian Macdonald, Paul Greenhaff and Henning Wackerhage.

About The University of Nottingham

The University of Nottingham is ranked in the UK’s Top Ten and the World's Top 100 universities by the Shanghai Jiao Tong (SJTU) and Times Higher Education (THE) world university rankings.

More than 90% of research at The University of Nottingham is of international quality, according to RAE 2008, with almost 60% of all research defined as ‘world-leading’ or ‘internationally excellent’. Research Fortnight analysis of RAE 2008 ranks the University 7th in the UK by ‘research power’. In 27 subject areas, the University features in the UK top ten, with 14 of those in the top five.

The University provides innovative and top quality teaching, undertakes world-changing research, and attracts talented staff and students from 150 nations. Described by The Times as Britain’s “only truly global university”, it has invested continuously in award-winning campuses in the United Kingdom, China and Malaysia. Twice since 2003 its research and teaching academics have won Nobel prizes.

The University has won the Queen’s Award for Enterprise in both 2006 (International Trade) and 2007 (Innovation – School of Pharmacy), and was named ‘Entrepreneurial University of the Year’ at the Times Higher Education Awards 2008.

Nottingham was designated as a Science City in 2005 in recognition of its rich scientific heritage, industrial base and role as a leading research centre. Nottingham has since embarked on a wide range of business, property, knowledge transfer and educational initiatives ( www.science-city.co.uk) in order to build on its growing reputation as an international centre of scientific excellence. The University of Nottingham is a partner in Nottingham: the Science City.

About BBSRC

The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £450 million in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports a number of important industrial stakeholders including the agriculture, food, chemical, healthcare and pharmaceutical sectors. BBSRC carries out its mission by funding internationally competitive research, providing training in the biosciences, fostering opportunities for knowledge transfer and innovation and promoting interaction with the public and other stakeholders on issues of scientific interest in universities, centres and institutes.

The Babraham Institute, Institute for Animal Health, Institute of Food Research, John Innes Centre and Rothamsted Research are Institutes of BBSRC. The Institutes conduct long-term, mission-oriented research using specialist facilities. They have strong interactions with industry, Government departments and other end-users of their research.

External contact

Professor Michael Rennie, Professor of Clinical Physiology

tel: 01332 724603
mob: 07766 662383

Simon Butt, Media Relations Manager

tel: 0115 951 5793

Contact

Matt Goode, Head of External Relations

tel: 01793 413299

Tracey Jewitt, Media Officer

tel: 01793 414694
fax: 01793 413382