Teaching Old Muscles New Tricks

Exercise is good for young and old alike, but different biochemical pathways kick in when seniors work out. SFU kinesiologist Wade Parkhouse studies these differences.

Wade Parkhouse did not start out as a biochemist. He began with a Bachelors of Physical Education but soon became interested in the physiology of athletic performance. His PhD in Zoology examined the regulation of metabolic pathways in exercising rainbow trout. Parkhouse has studied the performance of thoroughbreds, greyhounds, marlin, Peruvian Quechua natives and athletes but he says, "Increasing one athlete's chance of winning a gold medal is not as rewarding for me as enhancing the quality of life for a huge segment of the population--the elderly." For the past 5 years, instead of focusing on understanding how metabolic pathways are turned on, Parkhouse has switched his research to discovering what suppresses energy and growth-related pathways in the body.

Wade Parkhouse and Doreen Player at the Confederation Community Centre For the Retired in Burnaby, BC help Barb Godman, a volunteer subject in an experiment to determine how exercise affects the biology of aging in the elderly.

"When a press release went out last August calling for seniors to volunteer for our exercise experiments it was so popular we had to hire someone to field the calls," says Parkhouse.

Until your late teens your body produces large amounts of IGF-1, a hormone that promotes growth whose chemical structure is similar to insulin. While insulin primarily affects the body's metabolic system--fuel delivery and consumption--IGF-1 is part of the body's mito-genic system that helps regulate cell growth. After your teens IGF-1 production slowly falls off in concert with reduced growth hormone secretion. Production can be stimulated by exercise in the young, but not in the elderly.

However, IGF-1 circulates bound to specific proteins that affect its bioavailability a bit like a timed-release drug. Recent research from Parkhouse's lab has demonstrated that exercise increases the bioavailability of IGF-1 in the elderly. In addition they have shown that exercise reverses IGF-1 resistance in the elderly partially by increasing the number of IGF-1 receptors and their affinity for IGF-1.

Parkhouse is currently investigating structural changes in the IGF-1 receptor which may account for this increased binding affinity as well as how IGF-1 initiates mitogenic pathways (the ? in the diagram above). The ultimate goal: to understand how signalling pathways are turned on and off. Such a discovery is also relevant for diseases like cancer and especially diabetes. Contact Parkhouse at 291-4109 or parkhous@sfu.ca.

Parkhouse's research has shown how exercise in the elderly makes the hormone IGF-1 more available to muscle cells. The presence of IGF-1 at receptor sites triggers signal pathways involving numerous intermediates that stimulate the nucleus to transcribe proteins for growth or metabolism.

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