Differential expression of Akt, PPARgamma, and PGC-1 during hibernation in bats.
The effects of hibernation on the expression of Akt (protein kinase B), the peroxisome proliferator-activated receptor gamma isoform (PPARgamma), and the PPARgamma coactivator PGC-1 were assessed in seven tissues of the little brown bat, Myotis lucifugus. Western blotting revealed that the levels of active phosphorylated Akt were strongly reduced in brain, kidney, liver, and white adipose during torpor as compared with aroused animals and that total Akt protein was also reduced in white adipose during torpor. By contrast, both total and phospho-Akt were elevated in brown adipose tissue, the thermogenic organ. PPARgamma and PGC-1 levels showed parallel changes in all organs. Both were strongly suppressed in brain, but levels increased significantly in all other organs during hibernation (except for PGC-1 in heart). Reduced Akt activity is consistent with a probable reduced insulin response during torpor that facilitates the mobilization of lipid reserves for fuel supply and is further supported by increased gene expression of enzymes and proteins involved in lipid catabolism under the stimulation of enhanced PPARgamma and PGC-1 levels.
Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Sean F
SF
Eddy
Kenneth B
KB
Storey
D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D002685:Chiroptera / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006605:Hibernation / Q000502:physiology*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D051057:Proto-Oncogene Proteins c-akt; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis*; D014157:Transcription Factors / Q000096:biosynthesis*
D011518:Proto-Oncogene Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt