Understanding the importance of your body’s circadian clock and how it shapes your eating and sleeping habits can be one of the most important things in living a healthy life. Many scientists have spent years researching the body’s circadian clock, some even taking it a step further to study the circadian clock in animals. Specifically, the circadian programming in Drosophila, also known as fruit flies, has been investigated in a lab in the Department of Neurobiology at Northwestern University. Tomas Andreani and his team have worked to determine the way in which the circadian clock and R5 sleep homeostat work together to regulate sleep in Drosophila. Their work, Circadian Programming of the Ellipsoid Body Sleep Homeostat in Drosophila, described how they scheduled 2.5 hour periods of sleep deprivation and assessed the sleep rebound for 4.5 hours at different times throughout the day, over a 7 day period, until all 24 hours of the day had been assessed. Comparisons were made to flies’ baseline sleep in order to determine the level of rebound sleep that had occurred. Overall, it was noted that homeostatic regulation was influenced by the circadian clock. In parallel, a recent news article, Your Body Has an Internal Clock that Dictates When you Eat, Sleep and Might Have a Heart Attack, All Based on Time of Day, written by Dr. Shogo Sato, outlines some of the major hormones and daily actions that affect your circadian rhythm. Furthermore, Sato describes his analysis of tissue samples harvested from mice in the early morning and late evening using mass spectrometry to look at exercise metabolism. Let us look deeper into what your circadian rhythm is and how it affects both the internal cycle of humans and Drosophila.
Let’s begin with the first study, Circadian Programming of the Ellipsoid Body Sleep Homeostat in Drosophila by Tomas Andreani and his colleagues: Clark Rosensweig, Shiju Sisobhan, Emmanuel Ogunlana, William Kath, and Ravi Allada. In contrast with the news article, this paper discussed how the circadian clock works independently of one’s sleep homeostat to regulate sleep. We can characterize sleep, as the period of time in which changes in neuronal activity and increased arousal thresholds are observed and circadian and homeostatic regulation takes place. One’s sleep homeostat operates in a feedback loop that consists of 4 stages: wake, factor, sensor, outputs. When one is sleep deprived, a decrease in motor function, memory, and efficiency can be observed in addition to an increased chance of developing Alzheimer’s disease or depression. In this study, Drosophila were used because they are a well-established model for studying circadian rhythms and sleep. They were exposed to 7-hour sleep deprivation and recovery cycles and underwent homeostatic testing every hour. The results found that sleep rebound remains consistent throughout the entire trial indicating that fruit flies make a full recovery in the allotted rebound time. Furthermore, rebound was significantly higher in the morning compared to the evening in which rebound was observed to be suppressed. In the news article, Sato observed a similar pattern in the tissue samples obtained from mice in the early morning. These differences in the Drosophila were observed in correlation to increases in calcium levels. Extended wakefulness in Drosophila was tied to elevated calcium levels and the inhibition of calcium allowed for reduced rebound which supports the role of calcium signaling in behavioral output. In conclusion, although the two operate independently of one another, the effects of one can influence the other and sleep deprivation can lead to a higher rebound in the morning compared to the afternoon.
Shifting focus to Dr. Shogo Sato’s article in Eat This, Not That, Your Body Has an Internal Clock that Dictates When you Eat, Sleep and Might Have a Heart Attack, All Based on Time of Day, Sato elaborates on the impacts of your daily routine on your circadian cycle and vice versa. In his own work, Sato used mass spectrometry to analyze tissue samples from mice who had exercised in the early morning or late evening to try and determine if metabolic rates varied depending on the time of day exercise occurred. His data led to the formation of the “atlas of exercise metabolism”, which revealed a common pattern. Similar to the findings surrounding rebound rates in the first study, the tissue of the mice who exercised in the morning showed higher metabolic rates than those who exercised in the evening. Specifically, the tissues from the morning showed reduced blood glucose levels. Nonetheless, evening exercise also had its own benefit in the fact that mice were able to utilize stored energy from their meals throughout the day to boost their endurance. Another main point of Sato's article was that your daily routine impacts your circadian cycle, by way of the body’s endocrine system. The pineal gland in humans is the site of melatonin release and this release can be altered by the presence of artificial blue light before bed. Another hormone, leptin, which controls the body’s appetite is regulated by sleep. When your sleep cycle is off, your appetite shifts and you may find yourself craving food at abnormal times throughout the day or experiencing a lack of appetite. Overall, Sato proposes that regular sunlight exposure, daily activity, and abstinence from late night coffee or artificial light before bed can all help improve your body’s circadian clock.
Both studies emphasize the strong correlation between the body’s circadian cycle and one’s sleeping and eating patterns. Tomas Andreani and Dr. Shogo Sato highlight just some of the numerous studies surrounding circadian cycles and the body’s internal homeostatic regulation systems. Evidence supports that your body’s circadian cycle impacts many things including sleep rebound, appetite, and increased risk of mood disorders and degenerative diseases. Going forward, the study of sleep cycles and one’s circadian rhythm should be considered a key component in further understanding the mechanisms behind an individual’s internal homeostatic control.
Works Cited
Andreani, Tomas, et al. “Circadian Programming of the Ellipsoid Body Sleep Homeostat in Drosophila.” ELife, vol. 11, 2022, https://doi.org/10.7554/elife.74327.
Sato, Dr. Shogo. “Your Body Has an Internal Clock That Dictates When You Eat, Sleep and Might Have a Heart Attack, All Based on Time of Day.” Eat This Not That, 2 Dec. 2022, https://www.eatthis.com/your-body-has-an-internal-clock/.
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