Buzz about insulin, genes and food choice

Photo credit: Adam Siegal

An article in U.S. News and World Report highlights ASU scientists' findings that "insulin signals from fat cells in the bees’ abdomens help determine whether they forage for high-protein pollen or sugar-filled nectar." The feature was based on the ASU study that examines food-choice behavior in honey bees, published April 1 in the open-access journal PLoS Genetics.

ASU scientists identified a gene involved in bees’ decisions to bring protein or nectar back to the colony. By taking control of the Insulin Receptor Substrate gene (IRS), an insulin partner gene in the bees' fat cells, researchers in ASU's School of Life Sciences and the Norwegian University of Life Sciences made the insects forego carbohydrates (sugar-containing nectar) and favor protein (pollen).

Food decisions are responsible, in part, for the epidemic of metabolic disorders in humans, such as diabetes and obesity. IRS partner genes are found in people where deficiencies in the insulin pathway have caused metabolic disease. Insulin is thought to change eating behavior by signaling to its IRS partner in the brain. In contrast, the results from Associate Professor Gro Amdam’s research group, which included postdoctoral fellows Ying Wang, Navdeep Mutti, faculty research fellow Osman Kaftanoglu, and doctoral students Adam Siegel, Adam Dolezal and Kate Ihle, show that IRS outside of the brain can also modify food-choice behavior.

Most fat cells in honey bees are located in the abdomen. Researchers found that the experimental bees with normal IRS in the brain, but artificially reduced IRS in abdominal fat, returned to their colonies with less nectar than control bees. These bees' increased attraction to pollen and diminished interest in carbohydrates suggested an alteration in sensitivity to sugar. However, further testing determined that these bees gave up nectar without losing their taste for sugar.

While IRS affects the food choices of bees, it is not the only gene involved. Previous studies identified vitellogenin, a gene that also is active in fat cells. Its effect on the bees' loading of protein and carbohydrates is opposite to that of IRS. The researchers could not, in the present study, find a direct connection between the two genes.

Amdam is a Pew Scholar in the Biomedical Sciences, Pew Charitable Trusts, and a Young Outstanding Researcher, chosen by the Research Council of Norway in 2007. Starting out as a theoretician who built computer simulations of social interactions, Amdam has moved on to make key discoveries in the genetic, physiological and behavioral mechanisms underlying division of labor, caste development and has advanced understanding around the evolution of social life strategies, including aging, in social insects. Her work produced the first “knockdown” adult bee where gene expression was experimentally changed, and her research team in Norway discovered how honey bee aging can be a function of behavior, rather than age itself. She has published 46 articles since her first paper appeared in 2002.

Her work, primarily using the honey bee as a model organism, has been published in professional journals as varied as Nature, Science, Experimental Gerontology, Proceedings of the National Academy of Science (PNAS), Behavioural Brain Research, Public Library of Science (PLoS) Biology, PLoS ONE, Animal Behavior and Advances in Cancer Research. Amdam has been selected as a Fellow at the Wissenschaftskolleg zu Berlin (2010), with her focus on the role of epigenetic mechanisms in social behavior.

This work was supported by Norwegian Research Council, U.S. National Science Foundation, The PEW Charitable Trust, and the Wissenschaftskolleg zu Berlin.

CITATION: Wang Y, Mutti NS, Ihle KE, Siegel A, Dolezal AG, et al. (2010) Down-Regulation of Honey Bee IRS Gene Biases Behavior toward Food Rich in Protein. http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.