Obesity creates wimpy rats

May 9, 2011

(Medical Xpress) -- Obesity appears to impair normal muscle function in rats, an observation that could have significant implications for humans, according to Penn State researchers.

"Our findings demonstrate that obesity involves more than accumulating excess fat and carrying ," said Rudolf J. Schilder, American Physiological Society postdoctoral fellow in physiological genomics, Penn State College of Medicine. "We show that, during the development of obesity, skeletal muscles fail to adjust their molecular composition appropriately to the increasing . Consequently, the muscles of obese mammals are not properly 'tuned' to the higher body weight they carry."

Schilder and his colleagues examined whether normal mammalian perceives the amount of weight it is carrying, and whether it makes physiological adjustments to compensate for more or less weight. They theorized that this ability of muscle may be affected in obesity, as obese mammals typically suffer from reduced mobility and .

The study, published in a recent issue of the , used both healthy and genetically obese rats to determine how the expression of troponin T -- a gene that codes for a protein essential to muscle function -- varied as rats gained weight.

The research shows that the regulation of troponin T expression in a way appropriate for given body weights is impaired in obese rats.
"These results may explain why and are impaired in obese humans, and hence perhaps why it is so difficult to lose excess weight and recover from obesity," said Schilder.

The researchers first demonstrated that troponin T expression varied with body weight during normal growth. Then they artificially increased the body weight of one group of rats by 30 percent using a custom-made weighted vest. Externally applied weight caused a shift in the muscle troponin T expression, matching that of animals whose actual body weight was 30 percent higher. In contrast, troponin T expression did not respond to a similar increase in body weight in the obese rats.

Troponin T expression was examined in the muscles from a total of 68 rats. Nine were genetically obese, 19 were weight loaded and the rest of the rats served as controls. The weight-loaded wore the vests for five days.

"Our study is likely to stimulate a quest to determine the pathways and mechanisms that sense body weight and control muscle , as this could ultimately provide new therapeutic approaches to alleviate these obesity-associated problems," said Schilder.

Also working on this research were Scot R. Kimball, professor of cellular and molecular physiology; Leonard S. Jefferson, Evan Pugh Professor of cellular and molecular physiology and chair, both at Penn State College of Medicine; and James H. Marden, professor of biology, Penn State Eberly College of Science.

The National Institutes of Health, the National Science Foundation and the American Physiological Society supported this research.

Related Stories

Recommended for you

New 'Tissue Velcro' could help repair damaged hearts

August 28, 2015

Engineers at the University of Toronto just made assembling functional heart tissue as easy as fastening your shoes. The team has created a biocompatible scaffold that allows sheets of beating heart cells to snap together ...

Fertilization discovery: Do sperm wield tiny harpoons?

August 26, 2015

Could the sperm harpoon the egg to facilitate fertilization? That's the intriguing possibility raised by the University of Virginia School of Medicine's discovery that a protein within the head of the sperm forms spiky filaments, ...

Research identifies protein that regulates body clock

August 26, 2015

New research into circadian rhythms by researchers at the University of Toronto Mississauga shows that the GRK2 protein plays a major role in regulating the body's internal clock and points the way to remedies for jet lag ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.