Dragonflies may have to put down the Doritos and lay off the ice cream -- researchers at Penn State discovered that dragonflies exhibit the same metabolic dysfunction as humans that may lead to obesity and type-2 diabetes.

The metabolic dysfunction that leads to obesity might not be only a characteristic of humans and mammals, but also non-mammals such as dragonflies and other insects, said Ruud Schilder, post-doctorate research associate at University of Nebraska and former Penn State graduate student.

One of the molecules associated with dragonflies' symptoms of metabolic syndromes, such as diabetes and high blood pressure, is also found in humans with metabolic syndrome, Jim Marden, professor of biology, said.

The pair examined dragonflies infected with noninvasive gut bacteria. Schilder analyzed muscle performance and blood-sugar levels.

"Types of fuels used are associated with certain types of behavior," Schilder said.

Insect flight muscles that use carbohydrates are for the short-burst pattern of flying, and muscles that use fats are for sustained and migratory flight, he said. The dragonflies that were infected with the bacteria used only carbohydrates, building up fat around the body.

"That is how the obesity comparison comes in," Schilder said. "It is the same type of phenomena that you see in other animals like humans."

The team also discovered a possible link to insulin resistant, type-2 diabetes, Schilder said.

The infected dragonflies also had a two-fold increase in blood sugar, he added.

"When we look in the musculature of dragonflies there is a molecule marker of inflammation and stress that is on in chronically infected individuals, and in healthy [dragonflies] they're not on," Schilder said.

Inflammation and fat accumulation in the body are precursors for metabolic syndrome, obesity and type-2 diabetes, Marden said.

As fat increases in the body it begins to send an inflammatory response because it is not receiving sufficient oxygen, Marden said. The inflammation causes incorrect signaling about metabolism, leading to dysfunction and disease, he said

Inflammatory responses can also be the result of an infection in the mouth, he added.

"People with type-2 diabetes have too much insulin, and it is noticed with periodontal diseases like gum disease," Marden said.

The paper will be published in today's issue of the Proceedings of the National Academy of Sciences.

"I think this is a great paper," Daniel Hahn, assistant professor of entomology and nematology at the University of Florida said. "It is really very interesting."

Insects are useful human models, Hahn said.

"Insects have many of the same underlying physiological processes as a human, like insulin to control blood sugar, growth and reproduction," he said. "Looking at which parts are the same and which parts are slightly different we can learn a lot more about how human systems work. This is a great fresh perspective on these problems."