Physical activity is essential to fighting obesity, and scientists are constantly working to make this activity more effective and beneficial.
A $450,000 grant from the National Institutes of Health will help Biology Professor Colleen Novak, Ph.D., from Â鶹ĘÓƵ’s College of Arts and Sciences better understand how the body allocates energy and burns fat.
In her project, “Mechanisms Underlying Contextual Induction of Muscle Thermogenesis,” Novak is studying the biological phenomenon known as thermogenesis — how the body burns caloric energy, turning it into heat.
“We are going to look at a specific aspect of that, which is the heat put off by skeletal muscle as a way to dissipate energy,” Novak says. “We’ve found a way to make rats engage muscle thermogenesis, and this grant allows us to study the mechanisms behind that.”
The biological systems and processes in rats are very similar to those in humans, so the rodents are commonly studied in research with the potential for human applications.
“We have to figure that out if we want to be able to hijack the process to replicate the phenomenon in humans somewhere down the line,” Novak says. “Thermogenesis burns energy in general, and hopefully some of that energy will be fat.”
She said the project will test the importance and potential of thermogenesis for inducing weight loss, separate muscle from other sources of thermogenesis in animal models, and allow researchers to eventually understand the brain’s role in the process.
Novak’s research has previously shown that obese animals have lower rates of muscle thermogenesis, burning fewer calories during activity and not increasing their muscle temperature as much as lean rats.
“We’ll be testing some ideas on what brain mechanisms are involved in controlling this,” Novak says. “We’ll be able to develop the tools to tap into some existing theories.”
Novak says it is believed the brain communicates with skeletal muscle through the sympathetic nervous system — the part responsible for the “fight-or-flight” response — based on two key observations.
“We know other brain regions are involved in turning on other types of thermogenesis through the sympathetic nervous system, so it logically follows that the brain region we study would use a similar pathway,” Novak says.
More decisive, though, are Novak’s observations of the rats’ responses to certain stimuli.
“The best result comes when we expose them to predator odor,” Novak says.
When she introduces the scent of a ferret — a natural predator to rats — the rats’ leg muscle temperature rises by a full degree Celsius within two minutes, and as much as 1.5 to 2 degrees within 10 to 15 minutes.
In essence, what could lead animals — and eventually humans — to engage skeletal muscle thermogenesis, and burn energy less efficiently during exercise, is the reaction to a perceived threat, or at least tricking the body into triggering the corresponding biological response.
Novak says that in the context of weight loss, burning energy less efficiently is good because it means the body is using more calories. She likened the phenomenon to an inefficient car engine.
“We think this process changes how muscle cells handle energy, and it can make them less efficient,” she says. “Like an engine, you can tell when it’s not running efficiently, because it will lose power to heat. The energy has to go somewhere.”
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