Impacts of artificial light and melatonin signaling pathways on behavior and skeletal physiology in mice
[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The natural cycles of light and darkness are a major feature of the environment for most species; thus, circadian physiology is rooted in the expectation of bright days and dark nights, with biological processes and behaviors timed accordingly. Disruption of this natural pattern via exposure to artificial light at night can have negative consequences for many aspects of physiology, including bone biology. Here, a mouse model is used to explore the connections between nocturnal artificial light exposure, melatonin signaling, and skeletal phenotype. Nocturnal blue light exposure produced a combination of increased and decreased measures of bone growth in both male CBA/Ca and male C57BL/6 mice. Constant light exposure during the perinatal period was found to reduce femoral length as well as long-term activity levels in male C57BL/6 mice. Finally, MAPK signaling pathway disruption increased bone strength in female SCID mice as measured by trabecular spacing and bone volume fraction. The results suggest nocturnal artificial light exposure does impact circadian physiology and skeletal biology and have implications for human health concerns such as shift work, nocturnal electronic use, and light pollution.
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