title: IL-15 receptor deletion results in circadian changes of locomotor and metabolic activity.
abstract: Interleukin-15 (IL-15) is a cytokine produced in the normal brain that acts on its specific receptor IL-15Ralpha and co-receptors IL-2Rbeta and IL-2Rgamma in neuronal cells. The functions of the cerebral IL-15 system, however, are not yet clear. To test the hypothesis that IL-15Ralpha regulates metabolic activity and body temperature, we quantified the specific metabolic phenotype of IL-15Ralpha knockout mice. These normal-appearing mice were leaner with lower fat composition. During the entire circadian cycle, the knockout mice had a significantly higher acrophase in locomotor activity and heat dissipation. During the light phase, there was significantly greater food intake, oxygen consumption, and carbon dioxide production. The difference in the dark and light phases suggests that IL-15Ralpha participates in circadian rhythm regulation. The higher oxygen consumption in the light phase indicates adaptive thermogenesis in the knockout mice. The body temperature of the receptor knockout mice was significantly higher than the control in the light phase, and this was mainly caused by a large difference occurring between 0600 and 0900 h. In addition to the metabolic chamber studies and circadian rhythm analyses, qPCR of hypothalamic homogenates indicated higher mRNA expression of orexin and transient receptor potential vanilloid 4 cation channels. Consistent with a direct role of IL-15Ralpha in the hypothalamus, IL-15 treatment of the wild-type mice induced c-Fos expression in the preoptic area. We conclude that activation of hypothalamic neurons by IL-15 in mice contributes to thermoregulation and modifies the metabolic phenotype.
authors.affiliation: Pennington Biomedical Research Center, LSU System, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wu
authors.forename: Reas S
authors.initials: RS
authors.lastname: Khan
authors.forename: Abba J
authors.initials: AJ
authors.lastname: Kastin
authors.forename: Germaine G
authors.initials: GG
authors.lastname: Cornelissen-Guillaume
authors.forename: Hung
authors.initials: H
authors.lastname: Hsuchou
authors.forename: Barry
authors.initials: B
authors.lastname: Robert
authors.forename: Franz
authors.initials: F
authors.lastname: Halberg
authors.forename: Weihong
authors.initials: W
authors.lastname: Pan
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004435:Eating; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism; D019409:Interleukin-15 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D000068797:Orexins; D010101:Oxygen Consumption; D010641:Phenotype; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053647:Receptors, Interleukin-15 / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism
chemical_list: D019409:Interleukin-15; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D053647:Receptors, Interleukin-15; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C486576:Trpv4 protein, mouse