Most of the metabolic and behavioral processes in many organisms follow daily 24-hour oscillations known as circadian rhythms. The word “circadian” is derived from latin, with “circa” meaning around, and “diem” meaning day, translating to “circadian” in english. Out of the organisms that follow these circadian rhythms, some are diurnal, like humans, and others are nocturnal, like owls. In either case however, we see that circadian rhythms are entrained into these organisms by environmental cues that are crucial in also maintaining their circadian rhythms. Thus, for most organisms, maintaining their respective circadian rhythms is vital in keeping homeostasis in processes such as rest/activity, feeding behaviors, and metabolic processes.
In Dr. Cavanaugh’s talk, he described how maintaining circadian rhythms is crucial to the organism’s maintenance of crucial metabolic processes and overall organism homeostasis. Dr. Cavanaugh’s work shows how inconsistent circadian rhythms and things like night shift work and jetlag can have adverse effects on humans. Inconsistencies in circadian rhythms result from chronic circadian misalignment (CCM), which leads to “profound metabolic and cognitive consequences,” however the underlying mechanisms responsible for the effects of chronic circadian misalignment is unknown (Boomgarden et al., 2019). Through Dr. Cavanaugh’s findings, we see the adverse results of chronic circadian misalignment on the homeostatic processes of Drosophila melanogaster (fruit fly), and the underlying molecular mechanisms responsible for these results.
One of Dr. Cavanaugh’s major findings was that “exposing flies to CCM leads to a ~15% reduction in lifespan in both male and female flies” (Boomgarden et al., 2019). These are very profound results because they show a direct correlation between inconsistent circadian rhythms and the reduction of the organism’s lifespan. One aspect of this result that I found to be very reassuring was that he showed this to be the case with both male and female flies, showing a consistency between both sexes. Often times, researchers leave out female organisms because of their constant change in homeostasis due to their hormonal cycles which aren’t present in males, which can often make finding consistent results difficult because of this hormonal variance. However, Dr. Cavanaugh’s work shows thorough results that are consistent between both sexes, which is significant. In addition to this, Dr. Cavanaugh used “whole body RNA-sequencing to assess differences in gene transcription between control and misaligned flies”. Through this technique Dr. Cavanaugh is able to analyze the molecular mechanisms that are responsible for the physiological effects of CCM. Through this RNA-sequencing technique, Dr. Cavanaugh found that CCM on fruit flies led to “large-scale changes in gene expression” (Boomgarden et al., 2019). He found this change in gene expression to be comprised of an “upregulation of genes involved in response to toxic substances, aging and oxidative stress” along with a “downregulation of genes involved in regulation of development and differentiation, gene expression and biosynthesis” (Boomgarden et al., 2019). Thus, from his work, Dr. Cavanaugh concluded that the upregulation of those genes involved with aging, oxidative stress, and toxic substances was a result of CCM, which lead to “premature organismal decline”. He also concluded that “genes involved in lipid metabolism are overrepresented among those that are differentially regulated by CCM and aging”. This finding shows that out of all of the molecular mechanisms believed to be mediators in this process, Dr. Cavanaugh found altered lipid metabolism as a “potentially important mediator of the negative health consequences of CCM” (Boomgarden et al., 2019).
Thus, we see that maintaining regular circadian rhythms is crucial to maintaining homeostasis and having longevity. While shift work and jet lag are obvious detriments to circadian rhythms that result in CCM, the silent killer of circadian rhythms that most are unaware of is blue light exposure. In an article by Dr. Michael J. Breus in The Sleep Doctor, the effects of blue light exposure on sleep are made apparent. Dr. Breus discusses how scientific studies have shown that blue light is a type of light that is detrimental to sleep. This article talks about how this occurs as an effect of blue-light’s effect of melatonin suppression, and how it suppresses melatonin two-fold compared to the other wavelengths of light. As a result of this double suppression of melatonin it was shown that circadian rhythms were varied two-fold as well. This suppression of the circadian rhythms “can have a significant effect on health, creating problems with the cardiovascular, metabolic, and immune systems, disturbing mood, and compromising cognitive function” (Breus, 2019).
Dr. Breus then discusses how new a growing problem of blue light exposure on young adults has been brought to attention from new research. In the study, it was found that otherwise healthy young adults who were exposed to blue light from the interval of 9-11pm were found to display shortened net sleep duration, “significantly suppressed melatonin production, and diminished sleep quality” characterized with more significantly increased awakenings. In addition to this, it was found that blue light prevented the drop in body temperature, which is a “key element of the body’s progression into sleep” (Breus, 2019).
This same study observed the effects of of red light, on the opposite side of the spectrum to blue light, and observed that “red light exposure during the same two-hour evening time period did not interfere with sleep and circadian biology”. Thus Dr. Breus shows that using warmer, redder lights are favorable for sleep and circadian maintenance, while blue light exposure preceding sleep is detrimental to sleep and circadian rhythms, and result in CCM (Breus, 2019). He suggests, however, that blue light has its time and place, and that blue/cool light is beneficial for increased productivity and reaction time, and thus is good to intake in the mornings and afternoon. On the other hand, red/warm lights are more beneficial in the late evening until bedtime, as they promote relaxation and melatonin production.
All in all, going into finals week, I encourage everyone to take the extra steps to avoid blue light exposure preceding and during sleep by activating the night-shift feature for Apple users, and turning your device face-down while sleeping to ensure quality of sleep and a healthy circadian rhythm and prevent chronic circadian misalignment.
Sources:
Boomgarden, A. C., Sagewalker, G. D., Shah, A. C., Haider, S. D., Patel, P., Wheeler, H. E.,...
Cavanaugh, D. J. (2019). Chronic circadian misalignment results in reduced longevity
and large-scale changes in gene expression in Drosophila. BMC Genomics, 20(1).
doi:10.1186/s12864-018-5401-7
Breus, Michael J. “The Latest on Blue Light and Sleep.” Your Guide to Better Sleep, TheSleepDoctor, 22 Jan. 2019, thesleepdoctor.com/2017/11/06/latest-blue-light-sleep/.
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