Anyone who has experienced jet lag or worked the night shift knows the frustration of dealing with the outside concept of time. Although our eyes can see the change in the light and dark cycle of the Earth, our bodies continue to function as if we are in another time zone. It can be best described as being in a state of physiological confusion.
The effects of jet lag and shift work arise due to a naturally occurring process called the circadian rhythm. As the Latin name implies, our bodies tend to function in a cyclical pattern around a twenty-four hour period. This phenomenon has been dated back billions of years and appears to be a fundamental part of all living creatures on the planet. Yet, when the harmony between the outside and inside worlds is shifted, that infamous inability to function sets in.
For some, the internal clock may seem pointless, yet there is a good reason for its existence. Our immune system needs to take a break and rejuvenate. The clock helps to ensure our bodies get that rest during the lowest times of the twenty-four hour cycle, when it's night. During this enforced down time, immunity slows, allowing our natural defenses to reset and prepare for the coming day.
Other functions also benefit from the clock's hold on internal time, such as metabolism, regeneration of cells, and even the feeling of sleepiness.
Though the circadian rhythm is hard to control directly, researchers have learned it can be trained indirectly through diet. By switching the timing and content of meals, we can change that inner clock to better reflect the world outside. How exactly food can change our rest patterns happens has been difficult to figure out yet over the past few years, one particular culprit has been identified: our microbial population.
Back in 2014, researchers wondered whether the trillions of bacteria living inside of us would also be affected by a switch in circadian rhythm. The answer was found to be yes, at least in mice. When the animals changed their awake and rest cycles, there was a significant shift in the microbial population. Unfortunately for the animals, those species known to cause inflammation gained in number. The end result was a lack of rest for the immune system.
In the following year, another team of researchers revealed a rather unwelcome side effect of this circadian shift. The change in bacterial population led to health problems such as weight gain and other metabolic disorders. The same study revealed similar troubles in humans suggesting the mouse model could be extrapolated to us. Essentially, anyone who regularly travelled or performed shift work was at risk for bacteria-induced problems in the future.
At the time of these studies, the focus of the microbial consequences was immunity. However, last week, an international group of researchers revealed the impact of a shift in gut microbes may have even greater implications for our health. Their results suggest microbes are doing far more than affecting our immunity; they may be controlling our entire bodily function.
In previous experiments, the studies looked primarily at cell types. But for this study, the group decided to go deeper into the cells themselves. The hope was to examine a fundamental cellular activity, known as transcription, to see if microbes could affect this important aspect of a cell's life. If they were right, changes in the microbial population could in theory lead to changes in the body's natural rhythm.
The group used mice for their studies so they could gain perspective on a number of different cellular functions. As for the experimental procedure, it was relatively straightforward. Some mice were fed as normal - they were the controls. Others were fed large doses of antibiotics in the hopes of removing as much of the microbial composition as possible. After a few weeks, transcription was examined to see if there were any differences between the groups.
When the results came back, the researchers saw the expected changes in transcription in the intestine. This revealed the gut's circadian rhythm had been altered and was not working according to a normal 24 hour cycle. But this was only the start of the investigation.
The team also examined the liver for any changes in transcription. Although not connected to the intestine and having no contact with microbes, a difference was noted between the two mice groups. The changes affected the way the organ dealt with metabolism and also how it detoxified the body. Essentially, there was a risk for long term harm due to a lack of proper liver function,
For the authors, the results reveal microbes may have a much wider impact on the body's internal clock than previously believed. Not only is there an effect on immunity, but also there seems to be an effect on metabolism in the form of transcription alterations. This one-two punch to the system could make dealing with circadian disruptions even more troublesome for those who experience jet lag and shift work.
While the authors did not offer possible options to deal with microbial control of our rhythm, there is one possible silver lining. We may be able to control bacterial populations through diet in the same way we can reduce the effects of jet lag. By sticking to foods rich in fibre and including fermented products -- or probiotics -- the microbial population can be partially maintained. This may help to reduce the chance for unwanted alterations in metabolism. They may also make that jet lag or that graveyard shift a little more bearable.
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