Circadian rhythms allow for the coordination between behavioral and physiological processes that synchronize themselves to their external environment, usually via the signaling of core clock neurons that travel downstream to other tissues. Such that circadian rhythms can be entrained by cues in the environment like light and temperature, but these daily rhythms also persist in the absence of cues. Though circadian rhythms are inherent and essential for proper function, the exact mechanisms behind this are still not quite yet well understood. Because of this, many researchers tend to utilize the model organism, Drosophila melanogaster, which has been essential in discovering novel regulators of circadian rhythms due to their low genetic redundancy and functional simplicity. In increasing the mechanistic understanding of circadian rhythms, its implications and impact on human health and daily functioning may also be better realized.
Because it is still unclear as to how the central clock modulates certain circadian outputs, in the article, “A circadian output center controlling feeding: fasting rhythms in Drosophila,” by Dreyer et. al, the researchers specifically focused on the contributions of two neuronal populations in the pars intercerebralis (PI), a functional homolog to the mammalian hypothalamus, on circadian feeding times. Using a fly liquid-food interaction counter, the impact of DILP+ and SIPa+ cells on circadian feeding regulation was tested by continuously monitoring feeding behaviors while selectively activating or silencing each subset of PI cells. Thermogenetic manipulations of PI neurons expressing the neuropeptides, SIFamide and DILPs, were made, from which the rest: activity rhythms were monitored. These manipulations to the SIFa neuropeptide and mutations to the SIFa gene was found to cause a degradation of the feeding: fasting rhythms and also resulted in an elevated feeding amount. However, the manipulations to DILPs affected the amount of food consumption independently of feeding rhythms. Not only does this contribute to the current understandings of the PI’s control of circadian outputs, but also these findings also highlight how disruptions may cause circadian misalignment (Dreyer et al., 2019).
This notion of circadian misalignment is particularly applicable when considering individuals who partake in shift work, which often is at odds with our endogenous circadian system. Understanding shift work and its effect on humans has become increasingly relevant due to the COVID-19 pandemic, in which healthcare workers worked around the clock caring for the large influx of patients. In the article, “Effects of circadian misalignment on cognition in chronic shift workers,” by Chellapa et. al., the cognitive performance of individuals was evaluated after being subjected to various sleep schedules that simulated either day or night shifts. In addition to completing multiple cognitive tasks including the Psychomotor Vigilance Task and the Digit Symbol Substitution Task, the researchers assessed subjective sleepiness and recorded participant sleep via polysomnography. From this, their results suggested that the cognitive performance of chronic shift workers was dramatically affected because of circadian misalignment, which can not only pose a safety risk but also may have serious consequences on overall health and wellbeing (Chellapa et al., 2019).
Through the usage of animal models and human studies to uncover information regarding circadian rhythms, there is much potential in gaining an understanding of the mechanisms controlling circadian rhythms and their implications within various aspects, such as feeding and cognition. The research by Dr. Cavanaugh and Dr. Chellapa suggests that there is much more to be discovered regarding circadian outputs and the effects of disruptions on normal circadian-driven behaviors. Studying circadian rhythms not only aids in understanding the human body but also allows for treatments to be made for jetlag, sleep disorders, obesity, and mental health disorders, and improved methods for adjusting to nighttime shift work.
No comments:
Post a Comment