Effects of light on the circadian rhythm of diabetic rats under restricted feeding
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ORIGINAL PAPER
Effects of light on the circadian rhythm of diabetic rats under restricted feeding Tao Wu & Fen ZhuGe & Yali Zhu & Nan Wang & Qianru Jiang & Haoxuan Fu & Yongjun Li & Zhengwei Fu
Received: 16 April 2013 / Accepted: 5 August 2013 / Published online: 17 August 2013 # University of Navarra 2013
Abstract The aim of this study was to investigate whether the entrainment of light cue is affected or not in diabetic animals. We found that the individual light/ dark (LD) reversal showed a tissue- and gene-specific effect on the circadian phases of peripheral clock genes, which was generally similar between the control and diabetic rats. In the liver and heart, the peak phases of examined clock genes (Bmal1, Rev-erbα, Per1, and Per2) were slightly shifted by 0∼4 h in the liver and heart of control and diabetic rats. However, we found that the peak phases of these clock genes were greatly shifted by 8∼12 h after the LD reversal for 7 days in the pineal gland of both control and diabetic rats. However, the activity rhythm was greatly different between two groups. After the individual LD reversal, the activity rhythm was completely shifted in the control rats but retained in the diabetic rats. These observations suggested that the behavioral rhythm of diabetic rats may be uncoupled from the master clock after the individual LD reversal. Moreover, we also found that Tao Wu and Fen ZhuGe contributed equally to this study. Electronic supplementary material The online version of this article (doi:10.1007/s13105-013-0281-4) contains supplementary material, which is available to authorized users. T. Wu : F. ZhuGe : Y. Zhu : N. Wang : Q. Jiang : H. Fu : Y. Li : Z. Fu (*) College of Biological and Environmental Engineering, Zhejiang University of Technology, No.6 District, Zhaohui, Hangzhou, Zhejiang 310032, China e-mail: [email protected]
the serum glucose levels of diabetic rats kept equally high throughout the whole day without any shift of peak phase after the individual reversal of LD cycle. While the serum glucose levels of control rats were tightly controlled during the normal and LD reversal conditions. Thus, the impaired insulin secretion induced uncontrollable serum glucose level may result in uncoupled activity rhythm in the diabetic rats after the individual LD reversal. Keywords Clock genes . Type 2 diabetes . Pineal gland . Liver . Heart
Introduction According to the rotation of the earth on its axis, most organisms living in this world exhibit daily rhythms in physiology and behavior. In mammals, the circadian rhythms are organized by a circadian timing system that is comprised of a hierarchy of circadian clocks [6, 15, 35]. The master clock is localized in the hypothalamic suprachiasmatic nucleus (SCN), which controls the ∼24-h periodicity of mammalian behavior and physiology. The molecular core of the master clock is composed of a set of interlocking transcription/translation feedback loops involving multiple clock genes Clock, Bmal1, Per(s), Cry(s), Dec(s), and their proteins [13, 20]. The core clock
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