Muscle Loss in Senior Citizens Due to Blood Vessels
Failing to Dilate; Drugs May Help
Post-meal blood vessel expansion occurs in young,
not old; Muscles of young people look 50 years older by making muscle
blood vessels behave as they do in seniors
May 20, 2010 - Why do people become physically
weaker as they age? And is there any way to slow, stop, or even reverse
this process, breaking the link between increasing age and frailty?
Researchers say they can answer both questions.
In a paper published online yesterday in the
Journal of Clinical Endocrinology & Metabolism, University of Texas
Medical Branch at Galveston researchers present evidence that answers to
both those questions can be found in the way the network of blood
vessels that threads through muscles responds to the hormone insulin.
Utah scientist reports on emerging importance of
telomeres in aging, cancer and maybe immortality; seniors with short
telomeres most likely to die – see below story
Normally, these tiny tubes are closed, but when a
young person eats a meal and insulin is released into the bloodstream,
they open wide to allow nutrients to reach muscle cells. In elderly
people, however, insulin has no such “vasodilating” effect.
“We were unsure as to whether decreased
vasodilation was just one of the side effects of aging or was one of the
main causes of the reduction in muscle protein synthesis in elderly
people, because when nutrients and insulin get into muscle fibers, they
also turn on lots of intracellular signals linked to muscle growth,”
said UTMB’s Dr. Elena Volpi, senior author of the paper.
“This research really demonstrates that
vasodilation is a necessary mechanism for insulin to stimulate muscle
protein synthesis.”
Volpi and her collaborators reached this conclusion
after an experiment in which they infused an amount of insulin
equivalent to that generated by the body in response to a single meal
into the thigh muscles of two sets of young volunteers.
One group had been given a drug that blocked
vasodilation, while the other was allowed to respond normally.
Measurements of muscle protein synthesis levels where made using
chemical tracers, while biopsies yielded data on specific biochemical
pathways linked to muscle growth.
“We found that by blocking vasodilation, we
reproduced in young people the entire response that we see in older
persons — a blunting of muscle protein response and a lack of net muscle
growth. In other words, from a muscle standpoint, we made young people
look 50 years older,” Volpi said.
Such results point the way to what could be a
powerful new therapy for age-related frailty and the health and
quality-of-life problems that come with it.
“Eventually, if we can improve muscle growth in
response to feeding in old people by improving blood flow, then we’re
going to have a major tool to reduce muscle loss with aging, which by
itself is associated with reduction in physical functioning and
increased risk of disability,” Volpi said.
Other authors of the paper were lead author and
postdoctoral fellow Kyle Timmerman, medical student Jessica Lee,
assistant professor Hans Dreyer, research scientist Shaheen Dhanani,
graduate students Erin Glynn and Christopher Fry, assistant professor
Micah Drummond, associate professor Melinda Sheffield Moore, and
professor Blake Rasmussen. Specialized metabolic studies were conducted
by the staff of the UTMB Clinical Research Center, part of the
university’s Institute for Translational Sciences. The National
Institute on Aging, the UTMB Claude D. Pepper Center Older Americans
Independence Center, the National Institute of Child Health and Human
Development and the UTMB Clinical Translational Sciences Award supported
this study.
>>
Click to Abstract online - (“Insulin Stimulates Human Skeletal
Muscle Protein Synthesis via an Indirect Mechanism Involving
Endothelial-Dependent Vasodilation and Mammalian Target of Rapamycin
Complex 1 Signaling”
ABOUT UTMB: Established in 1891, Texas’ first
academic health center comprises four health sciences schools, three
institutes for advanced study, a research enterprise that includes one
of only two national laboratories dedicated to the safe study of
infectious threats to human health, and a health system offering a full
range of primary and specialized medical services throughout Galveston
County and the Texas Gulf Coast region. UTMB is a component of the
University of Texas System.
May 20, 2010 - Why do people become physically
weaker as they age? And is there any way to slow, stop, or even reverse
this process, breaking the link between increasing age and frailty?
Researchers say they can answer both questions.