Penn State researchers have found that obesity impair normal muscle function in rats, which they say could have significant implications for humans too.
"Our findings demonstrate that obesity involves more than accumulating excess fat and carrying excess weight," 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 body weight. Consequently, the muscles of obese mammals are not properly 'tuned' to the higher body weight they carry," he said.
Schilder and his colleagues examined whether normal mammalian skeletal muscle 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 might be affected in obesity, as obese mammals typically suffer from reduced mobility and muscle function.
The study 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 showed 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 muscle strength and locomotion are impaired in obese humans, and hence perhaps why it is so difficult to lose excess weight and recover from obesity," said Schilder.
The study has been published in a recent issue of the Journal of Experimental Biology.