title: Effects of Daytime Exposure to Light from Blue-Enriched Light-Emitting Diodes on the Nighttime Melatonin Amplitude and Circadian Regulation of Rodent Metabolism and Physiology.
abstract: Regular cycles of exposure to light and dark control pineal melatonin production and temporally coordinate circadian rhythms of metabolism and physiology in mammals. Previously we demonstrated that the peak circadian amplitude of nocturnal blood melatonin levels of rats were more than 6-fold higher after exposure to cool white fluorescent (CWF) light through blue-tinted (compared with clear) rodent cages. Here, we evaluated the effects of light-phase exposure of rats to white light-emitting diodes (LED), which emit light rich in the blue-appearing portion of the visible spectrum (465-485 nm), compared with standard broadspectrum CWF light, on melatonin levels during the subsequent dark phase and on plasma measures of metabolism and physiology. Compared with those in male rats under a 12:12-h light:dark cycle in CWF light, peak plasma melatonin levels at the middark phase (time, 2400) in rats under daytime LED light were over 7-fold higher, whereas midlight phase levels (1200) were low in both groups. Food and water intakes, body growth rate, and total fatty acid content of major metabolic tissues were markedly lower, whereas protein content was higher, in the LED group compared with CWF group. Circadian rhythms of arterial plasma levels of total fatty acids, glucose, lactic acid, pO2, pCO2, insulin, leptin, and corticosterone were generally lower in LED-exposed rats. Therefore, daytime exposure of rats to LED light with high blue emissions has a marked positive effect on the circadian regulation of neuroendocrine, metabolic, and physiologic parameters associated with the promotion of animal health and wellbeing and thus may influence scientific outcomes.
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA. rdauchy@tulane.edu.
authors: Robert T
authors: RT
authors: Dauchy
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: Melissa A
authors: MA
authors: Wren-Dail
authors: Departments of Epidemiology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: Aaron E
authors: AE
authors: Hoffman
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: John P
authors: JP
authors: Hanifin
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: Benjamin
authors: B
authors: Warfield
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: George C
authors: GC
authors: Brainard
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: Steven M
authors: SM
authors: Hill
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: Victoria P
authors: VP
authors: Belancio
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: Erin M
authors: EM
authors: Dauchy
authors: Departments of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, Pennsylvania, USA.
authors: David E
authors: DE
authors: Blask
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000528:radiation effects; D002940:Circadian Rhythm / Q000528:radiation effects*; D003345:Corticosterone / Q000097:blood; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D020738:Leptin / Q000097:blood; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017440:Photoperiod; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001786:Blood Glucose; D007328:Insulin; D020738:Leptin; D019344:Lactic Acid; D008550:Melatonin; D003345:Corticosterone