Biochemical Regulation of Carbohydrate Metabolism in Hibernating Bats
Glycolysis is the core pathway of carbohydrate metabolism in cells; it is strongly regulated to mediate the use of sugar fuels for energy production (especially when oxygen is limiting) and biosynthesis as well as to allow opposite carbon flow during gluconeogenesis. Control of glycolysis should be a central part of metabolic suppression during torpor. Regulatory enzymes of carbohydrate catabolism (glycogen phosphorylase, 6-phosphofructo-1-kinase [PFK-1], pyruvate kinase, pyruvate dehydrogenase) were evaluated, along with levels of fructose-2,6-P2, a potent PFK-1 activator, in tissues of little brown bats (Myotis lucifugus) comparing aroused and torpor states of winter-collected animals. The data show substantial changes in enzyme activities and properties indicating differential regulation via reversible protein phosphorylation between aroused and torpid states. Torpor also triggered strong increases at the mRNA and protein level of the hypoxia-inducible transcription factor (HIF-1) (that regulates several glycolytic enzymes) in bat skeletal muscle and liver and the study documented for the first time the involvement of microRNA (miR-106b) and antisense RNA in the regulation of a transcription factor in a hibernating species.
KeywordsPyruvate Kinase Glycogen Phosphorylase Pyruvate Dehydrogenase Kinase Active Glycogen Phosphorylase Carbohydrate Catabolism
I am forever grateful to Dr. D.W. Thomas, Université de Sherbrooke for bat collection and use of his laboratory for experimental hibernation studies. Thanks to students from my laboratory (R. Whitwam, J. Duncan, M. de la Roche, Y. Maistrovski, K. Biggar) for their contributions to the bat research reported here and to J.M. Storey for editorial review of the manuscript. Supported by the N.S.E.R.C. Canada and the Canada Research Chairs program.
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