Metabolic syndrome and obesity in an insect
- Department of Biology, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802
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Edited by David L. Denlinger, Ohio State University, Columbus, OH, and approved October 12, 2006 (received for review April 18, 2006)
Abstract
Dragonflies infected with noninvasive gregarine gut parasites (Microsporidia, Apicomplexa) have reduced flight-muscle performance, an inability to metabolize lipid in their muscles, twofold-elevated hemolymph carbohydrate concentrations, and they accumulate fat in their thorax in a manner analogous to mammalian obesity. Gregarine infection is associated with inappropriate responses of hemolymph carbohydrate concentration to insulin and with chronic activation in the flight muscles of p38 MAP kinase, a signaling molecule involved in immune and stress responses. Short-term exposure to gregarine excretory/secretory products caused elevated blood carbohydrate and p38 MAPK activation in healthy individuals. These characteristics comprise a set of symptoms and processes that are known in mammals as metabolic syndrome but which have not previously been described in other animal taxa. In addition to expanding the known taxonomic breadth of metabolic disease, these results indicate that insects may be useful experimental models for studying its underlying biology and mechanisms.
Footnotes
- *To whom correspondence should be addressed. E-mail: rschilder2{at}unlnotes.unl.edu
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Author contributions: R.J.S. and J.H.M. designed research, performed research, analyzed data, and wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS direct submission.
- Abbreviations:
- ESP,
- excretory–secretory products;
- MS,
- metabolic syndrome;
- RQ,
- respiratory quotient.
- © 2006 by The National Academy of Sciences of the USA
