title: Caffeine lengthens circadian rhythms in mice.
abstract: Although caffeine alters sleep in many animals, whether or not it affects mammalian circadian clocks remains unknown. Here, we found that incubating cultured mammalian cell lines, human osteosarcoma U2OS cells and mouse fibroblast NIH3T3 cells, with caffeine lengthened the period of circadian rhythms. Adding caffeine to ex vivo cultures also lengthened the circadian period in mouse liver explants from Per2::Luciferase reporter gene knockin mice, and caused a phase delay in brain slices containing the suprachiasmatic nucleus (SCN), where the central circadian clock in mammals is located. Furthermore, chronic caffeine consumption ad libitum for a week delayed the phase of the mouse liver clock in vivo under 12 h light-dark conditions and lengthened the period of circadian locomotor rhythms in mice under constant darkness. Our results showed that caffeine alters circadian clocks in mammalian cells in vitro and in the mouse ex vivo and in vivo.
authors.affiliation: Food Function Division, National Food Research Institute (NFRI), National Agriculture and Food Research Organization (NARO), 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan. oike@affrc.go.jp
authors.forename: Hideaki
authors.initials: H
authors.lastname: Oike
authors.forename: Masuko
authors.initials: M
authors.lastname: Kobori
authors.forename: Takahiro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Norio
authors.initials: N
authors.lastname: Ishida
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D045744:Cell Line, Tumor; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects*; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D041681:NIH 3T3 Cells
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine