Please use this identifier to cite or link to this item:
Scopus Web of Science® Altmetric
Type: Journal article
Title: Rapidly alternating photoperiods disrupt central and peripheral rhythmicity and decrease plasma glucose, but do not affect glucose tolerance or insulin secretion in sheep
Author: Varcoe, T.
Gatford, K.
Voultsios, A.
Salkeld, M.
Boden, M.
Rattanatray, L.
Kennaway, D.
Citation: Experimental Physiology, 2014; 99(9):1214-1228
Publisher: Wiley
Issue Date: 2014
ISSN: 1469-445X
Statement of
Tamara J. Varcoe, Kathryn L. Gatford, Athena Voultsios, Mark D. Salkeld, Michael J. Boden, Leewen Rattanatray and David J. Kennaway
Abstract: Disrupting circadian rhythms in rodents perturbs glucose metabolism and increases adiposity. To determine whether these effects occur in a large diurnal animal, we assessed the impact of circadian rhythm disruption upon metabolic function in sheep. Adult ewes (n = 7) underwent 3 weeks of a control 12 h light-12 h dark photoperiod, followed by 4 weeks of rapidly alternating photoperiods (RAPs) whereby the time of light exposure was reversed twice each week. Measures of central (melatonin secretion and core body temperature) and peripheral rhythmicity (clock and metabolic gene expression in skeletal muscle) were obtained over 24 h in both conditions. Metabolic homeostasis was assessed by glucose tolerance tests and 24 h glucose and insulin profiles. Melatonin and core body temperature rhythms resynchronized within 2 days of the last photoperiod shift. High-amplitude Bmal1, Clock, Nr1d1, Cry2 and Per3 mRNA rhythms were apparent in skeletal muscle, which were phase advanced by up to 3.5 h at 2 days after the last phase shift, whereas Per1 expression was downregulated at this time. Pparα, Pgc1α and Nampt mRNA were constitutively expressed in both conditions. Nocturnal glucose concentrations were reduced following chronic phase shifts (zeitgeber time 0, -5.5%; zeitgeber time 12, -2.9%; and zeitgeber time 16, -5.7%), whereas plasma insulin, glucose tolerance and glucose-stimulated insulin secretion were not altered. These results demonstrate that clock gene expression within ovine skeletal muscle oscillates over 24 h and responds to changing photoperiods. However, metabolic genes which link circadian and metabolic clocks in rodents were arrhythmic in sheep. Differences may be due to the ruminant versus monogastric digestive organization in each species. Together, these results demonstrate that despite disruptions to central and peripheral rhythmicity following exposure to rapidly alternating photoperiods, there was minimal impact on glucose homeostasis in the sheep.
Keywords: Muscle, Skeletal
Chronobiology Disorders
Disease Models, Animal
Body Weight
Blood Glucose
Glucose Tolerance Test
Gene Expression Regulation
Body Temperature Regulation
Circadian Rhythm
Time Factors
Circadian Rhythm Signaling Peptides and Proteins
Rights: © 2014 The Authors. Experimental Physiology © 2014 The Physiological Society
DOI: 10.1113/expphysiol.2014.080630
Published version:
Appears in Collections:Aurora harvest 7
Paediatrics publications

Files in This Item:
File Description SizeFormat 
hdl_89600.pdfAccepted version591.15 kBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.