Circadian clocks are found in nearly all living organisms, and regulate behavioral and physiological processes to be synced up to a specific time in the day. It has been known for a while that the hypothalamus contains a sort of “master clock” that regulates sleep-wake cycles in response to the Earth’s exposure to the sun. This clock runs on a 24-hour schedule.
In the New York Times article, “When We Eat, or Don’t Eat, May Be Critical to our Health” the author discusses the science behind eating and how time of day plays a role in our overall metabolism. During the daytime, the pancreas produces the most insulin, a hormone that regulates glucose levels in the body. Other organs, such as the gut, also follow this clock, and have optimal times of function in the 24-hour time frame. Humans have evolved greatly since our conception, but a constant that the entire species has had is the rising and setting of the sun at roughly the same schedule forever. There is much evidence suggesting that our blood sugar control is at peak function during the morning, and weakest in the evening. This would then suggest that we should have larger meals earlier in the day and just a light evening meal, for a most advantageous schedule. During late evening, when there isn’t any sunlight, the brain produces melatonin which tells our body to sleep. However, if we are eating late at night, this signal conflicts with the melatonin, and potentially disrupts our sleep patterns.
Jet lag is a common known phenomenon. We are plagued with fatigue, and our brains feel almost foggy. On a less drastic scale, eating when our bodies aren’t programmed to digest and absorb nutrients from food will work our organs when they aren’t supposed to, which increases the risk of disease, according to Paolo Sassone-Corsi, the director of the Center of Epigenetics and Metabolism at the University of California, Irvine. He goes on to list shift workers as an example of those more susceptible to obesity, heart disease, some cancers, and heart disease. Thought we shouldn’t discount socioeconomic factors as a major cause, studies definitely show that circadian disruption can lead to poor health.
This relates very well to Dr. Cavanaugh’s research which we saw in class. However, according to Dr. Cavanaugh’s research, chronic circadian misalignment (CCM) results in reduced longevity and can lead to changes in gene expression in Drosophila, the common fruit fly. Drosophila possess a powerful genetic toolkit that can be relatively easily manipulated for scientific purposes. They are extremely useful model organisms because their homeostatic system is functionally conserved with the mammalian one. So his research on Drosophila can be translated over to mammals. CCM can be induced by the altered schedule shift workers are accustomed to, aberrant sleeping patterns, and eating schedules. This has a great effect on cognitive and metabolic activities, which was also summarized by Anahad O’Connor in the aforementioned article. Dr. Cavanaugh and his team of researchers found flies to have approximately a 15% reduction in the average lifespan in both male and female flies when they faced a 4-hour phase delays in their light-dark schedule. CCM also caused large scale changes in general gene expression, which was seen by the upregulation of genes that regulate toxic substances, aging, and oxidative stress, and downregulation of genes that are involved with regulating development, gene expression and biosynthesis.
The changes that this lab made to the schedules of the Drosophila are consistent with changes that many shift workers and even those with aberrant sleeping and eating patterns already experience. They concluded that CCM can lead to premature organismal decline. Dr. Cavanaugh plans to do further research regarding this subtopic in neuroscience, and we look forward to what he and his team will find.
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