Wednesday, January 4, 2012

The fast-fattening arctic ground squirrel may hold clues to why and how humans become obese

U.S. obesity rate, 1960-2004, CDC
Obesity is a concern in most industrial nations, and especially in the United States where 74.1 percent of the population is either overweight or obese.  This condition can be a prelude to some serious illnesses, including type 2 diabetes, hypertension and cardiovascular disease.

The medical costs are astounding, estimated at $117 billion in direct and indirect costs, half of that borne by Medicare and Medicaid. Did someone mention out-of-control health care costs?

So how can the humble little arctic ground squirrel help with such a serious health issue?

Khrys Duddleston, an associate professor in the Department of Biological Sciences at UAA, is finding that out in her lab, examining the microbial community in the intestinal tract of Urocitellus parryii. These squirrels are good for this study because they fatten up fast for hibernation  -- in only about three weeks time.

Duddleston, along with her collaborators Dr. Loren Buck and Dr. Fred Rainey, and her graduate and undergraduate students Tim Stevenson and Brian Quinlan, are curious whether the squirrel’s gut microbial community assists the host animal in putting on weight.  Using “next generation” genetic sequencing and other methods, they are mapping changes in the gut-microbial community during pre-hibernation fattening.

How does this work relate to humans and obesity?

In humans, microbes live within the human digestive system and contribute to immunity, synthesize vitamins and help digest fiber. Studies have shown that the gut microbial community in lean individuals is different from that of obese individuals, and that gut microbes may send signals to the host that predispose them to deposit fat. Duddleston and her colleagues contend that the arctic ground squirrel, due to its rapid fattening, is the ideal organism in which to further study the potential role the gut microbial community plays in obesity.

“We are doing basic science, using genetic sequencing to identify members of the gut-microbial community and how the community makeup changes as the squirrels deposit fat in preparation for hibernation,” Duddleston said.

Duddleston’s project received INNOVATE seed funds, which she is linking to start-up funding she received from INBRE (IDeA Networks for Biomedical Research Excellence, sponsored by NIH). This work has been supported by funds from the U.S. Department of Defense, and her undergraduate and graduate students have successfully applied for grants and fellowships from NIH-INBRE, the UAF Center for Global Change and the Alaska Hearth Institute that they used in this early work.

“INNOVATE funding will allow us to use next generation sequencing to get a deeper look at the gut microbial community,” she said. The results will enable her graduate student to publish his master's thesis with better, more specific information in a top-flight science journal. This, in turn, will strengthen Duddleston's application over the next one to two years for larger grants from the National Institutes for Health and the National Science Foundation.

Duddleston says a logical next step is to consider the use of antibiotics to manipulate the community of gut microbes to see how this affects pre-hibernation fattening in the squirrels. Could the growing propensity of humans to become obese be shut down by adjustments to our own digestive microbes?


Khrys Duddleston teaches microbiology in the Department of Biological Sciences at UAA. She graduated from Virginia Tech with a bachelor's and master's in Biology, and earned her doctorate in Microbiology from Oregon State University.  She is an INBRE (IDeA Networks for Biomedical Research Excellence) faculty affiliate. She joined UAA in 1998 as a post-doctoral research associate. (That Kenai king, by the way, weighed 42 pounds.)

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