How endogenous biological rhythms work

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The article is devoted to the work of circadian rhythms - endogenous biological rhythms with a period of about 24 hours, characteristic of most organisms, including humans. This is an overview of the latest scientific research, not a collection of helpful tips, even though the article does talk about a potential lifestyle change. This review is not exhaustive; we will continue to update it as new research studies emerge.

The main thing:

→ Consistent and healthy circadian rhythms can help improve overall health as well as effective prevention of chronic disease.

→ Remember to sleep: diet, exercise, and other factors affect how circadian rhythms work.

→ Study the peculiarities of the work of circadian rhythms, determine your "chronotype", then apply the knowledge gained to the methodological recommendations indicated in scientific research.

Before incorporating any of the advice in this article into your daily routine, check with your healthcare professional.

Before reading the article: a short glossary

1. Circadian: a naturally recurring cycle with a period of about 24 hours, regardless of the length of daylight hours; from the Latin circa ("o") and diem ("day").
2. Rhythm sensor: an environmental signal, such as a change in light or temperature; from the German zeit ("time") and geber ("giver").
3. Endogenous: a pathological process in the body caused by internal factors, and not caused by external influences (root cause).
4. Circadian rhythm adjustment: occurs when rhythmic, physiological, or behavioral tasks match changes in the environment; interaction of circadian rhythms with the environment.
5. Daily: every day; from the Latin dies (day) and and diurnus (daily).
6. Master Clock: A pair of cell populations found in the hypothalamus, also known as the suprachiasmatic nucleus (SCN); These cells contain genes that control the circadian rhythms.
7. Mutant gene: permanent change in the DNA sequence; used by chronobiologists to recognize the mechanism of clock genes by identifying a mutant gene in animals with arrhythmic circadian syndrome.

Imagine a plant trying to photosynthesize at night: a short drama in the dark. “Plants deal with life and death,” says Sally Yu, assistant professor of biochemistry and cell biology at the University of Texas at Houston Health Sciences Center (UTHealth), grimly. "If they don't follow circadian rhythms, they will die." But for a person, the forecast will not be so bleak. “Even if you remove the clock gene (an important gene that regulates the work of circadian rhythms), you will not die right away,” says Yu. “But you will suffer.” Likely problems? Persistent psychological problems and, among other things, an increased risk of chronic diseases. Life is hard when everything is out of sync.

Yu's colleague, Jake Chen, an assistant professor in the same department, says differently: “We often say that everything needs to be done on schedule. But this is an exaggeration. But the phrase "everything has its time" is not. And this is directly related to the human body. In every single cell, tissue or organ, physiological processes occur at a specific time. The biological clock is a kind of timer - a mechanism by which we can make sure that everything is working properly. This is a fundamental function.”

Chen and Yu study circadian rhythms - the biological rhythms of the body with a period of about 24 hours, which are followed every day by all living things on our planet. Circadian rhythms or circadian rhythms are directly related to the millions of years of development of life on our planet. It is a product of the interaction of the body's internal biological clock and the environment - not only sunlight, but many other factors determine behavior, regulate hormone levels, sleep, body temperature and metabolism.

The so-called "master clock" or suprachiasmatic nucleus (SCN), the master clock that controls circadian rhythms, is a pair of cell populations filled with genes (including Clock, Npas2, Bmal, Per1, Per2, Per3, Cry1, and Cry2), located in the hypothalamus. At the molecular level, clock gene traces are found in the kidneys, liver, pancreas and other organs. SCN acts as CEO instructing the body to adhere to schedule and process environmental signals. Howard Hughes Medical Institute.)

As we will see later, paying attention to circadian rhythms improves the daily (physiological and psychological) functioning of the body and, ultimately, affects the state of health, both in the long term and in the short term. Taking care of circadian rhythms keeps them working while maintaining what Sally Yu calls a "reliable watch."

“I cannot say for sure how important circadian rhythms are in preventing chronic disease, what impact it has on health in the long term, whether it is beneficial and ultimately affects life expectancy.”

Information about experts:

Scientist: Zheng "Jake" Chen

Education: PhD, Columbia University, New York

Position: Assistant Professor in the Department of Biochemistry and Cell Biology at the University of Texas Health Sciences Center at Houston

Last published article: The small molecule Nobiletin targets the molecular oscillator to enhance circadian rhythms and protect against metabolic syndrome.

Research area: Small molecule probes for chronobiology and medicine.

Scientist: Seung Hee "Sally" Yoo

Education: PhD, Korea Institute of Science and Technology

Position: Associate Professor, Department of Biochemistry and Cell Biology, University of Texas Health Sciences Center at Houston

Last published article: Period2 3'-UTR and microRNA-24 regulate circadian rhythms by repressing PERIOD2 protein accumulation. Also Development and Therapeutic Potential of Small-Molecule Modulators of Circadian Systems.

Research area: Fundamental cellular mechanisms in circadian rhythms and deciphering physiological and pathological roles of the clock.

HISTORY: MAIN STAGES OF BIOLOGICAL DEVELOPMENT OF CIRCADIC RHYTHMS

The first thing to know about the study of circadian rhythms (chronobiologists do this) is that, with rare exceptions, all organisms follow their circadian rhythms. From daffodils to sparrows, from zebras to humans, virtually all living organisms on the planet follow the solar cycle. In 1729, the French scientist Jean-Jacques de Meran recorded the first observation of endogenous or embedded diurnal leaf movements of the Mimosa pudica plant. Even in complete darkness, the plant continued to follow its daily rhythm. The scientist concluded that the plant relies not only on external signals or a rhythm sensor, but also on its own internal biological clock.

Chronobiology flourished two hundred years later, in the middle of the 20th century. Affected by the contribution of a number of scientists, in particular Colin Pittendry, "the father of the biological clock." Pittendry studied fruit flies, or Drosophila, and shed light on how circadian rhythms interact or synchronize with the cycle of day and night. Jurgen Aschoff, a friend of Pittendry, also studied interaction with the cycle of day and night, but scientists came to different conclusions about how the interaction occurs (parametric and nonparametric, you can read more about it here and here). John Woodland Hastings and his colleagues made fundamental discoveries about the role of light in circadian rhythms by studying bioluminescent dinoflagellates (algae, a species of plankton). Botanist Erwin Bunnig also contributed to basic research on interaction modeling, describing the relationship between organisms and cut-off cycles.

The next stage of discoveries in chronobiology connected the specific molecular and genetic mechanisms of the work of circadian rhythms. This follows from the work of Ron Konopka and Seymour Benzer, who in the early 1970s sought to identify specific genes that control the circadian rhythms of fruit flies. Konopka and Benzer are credited with the discovery of a mutated gene, which they called a period that disrupts the circadian clock of fruit flies. This is how the genetic determinant of behavioral rhythms was first discovered. Jeffrey S. Hall, Michael Rosbash, and Michael W. Young have successfully complemented the work of Konopka and Benzer by showing the work of the period gene at the molecular level. Hall, Rosbash and Young received the Nobel Prize in Physiology or Medicine in 2017. They isolated the period gene and then showed how the daily clock system works at the molecular level.

While conducting research on fruit flies and mice in 1994, Joseph Takahashi and his team discovered clock genes in mammals and called them clocks, describing them as "an evolutionarily conserved feature of the circadian clock mechanism." The discovery of the clock gene, along with the work of Hall, Rosbash, Young, and scientist Michael Greenberg, was a watershed moment in chronobiology. Within a few years, genes were discovered that ensure the work of circadian rhythms in lower organisms.

Science is advancing steadily, and many studies in fruit flies and mice have demonstrated the remarkable persistence of clock genes within species, which means that there are similar genes that control circadian rhythms in more complex organisms, including humans.

"Sunrise and sunset are still the main factors affecting circadian rhythms, but other factors are continually monitored in scientific research."

LATEST RESEARCH: DETERMINING THE ROLE OF CIRCADIUM RHYTHMS IN HUMAN HEALTH AND DISEASES

It is important to note that the biology of circadian rhythms is incredibly complex - there are many scientific journals dedicated to this area of research. As a result, our understanding of the role of the biological clock in human health is the result of epidemiological studies as well as animal studies. Studies on lower organisms help to reveal the work of molecular and genetic mechanisms in action, after which it can be seen how, for example, sleep disturbance leads to an increased risk of type 2 diabetes, obesity, and a number of cardiovascular diseases.

Indeed, one of the most promising areas of research is sleep. Scientists today associate lack of sleep and subsequent disruption of circadian rhythms with the development of obesity and depression, as well as most chronic diseases. Research has shown that lack of sleep can lead to unexpected side effects, such as an inability to recognize faces.

Understanding how circadian rhythms work has also gone far beyond interacting with the cycle of day and night. “There are social cues, signals to eat and exercise - they are very diverse,” says Y. Sunrise and sunset still have a major influence on circadian rhythms, but other factors are being investigated. A large body of work has shown that diet is a key external signal that interacts with the internal clock, including Dr. Satchidananda Panda's work on time-limited eating (how eating time affects health).

In general, it is now clear that circadian rhythms play a systemic role to organize the work of all physiological aspects of the human body, including the work of vital organs, metabolism, immunity, thought processes, etc. Dr. Yu's work expands the area of research - she collaborates with a specialist chronic pain study to study pain rhythms in patients. Also, work is underway to study the role of the cut-off cycle in disturbances in the work of circadian rhythms (the effect of changing time zones on the growth of cancer cells). Research like this provides us with important new insights that can be used to make lifestyle changes - knowing what time to eat and go to bed in general is important to health; and with illness, the knowledge gained can be applied to the search for drugs that regulate the work of circadian rhythms. Scientists still have a lot of research to do in almost all areas related to health and disease.

BASIC THOUGHT: WHY IS IT IMPORTANT TO KNOW ABOUT CIRCADE RHYTHMS?

Awareness of how circadian rhythms work can have both short-term and long-term health effects. “Lifestyle changes are the best gift you can give yourself,” says Chen. “If you manage your lifestyle, technology and medicine can become secondary factors throughout your life.” In the short term, animal and human studies show that lifestyles that support healthy circadian rhythms can support alertness, motor coordination, cardiovascular health, immune function, gut health, thought and sleep. There is evidence to support a long-term reduction in the risk of chronic disease.

"The effects of lifestyle changes may not be apparent for several days, but over time, the benefits will be enormous."

So what kind of lifestyle do you need to lead in order to sync with your circadian rhythms? The first thing to do is to pay attention to your biorhythms. Circadian rhythms, although built on the same foundation, vary from person to person due to age, genetic, and environmental differences. Larks like the morning better. Owls prefer the night. You need to pay attention to the natural tendencies of your body (“chronotype”) in order to successfully apply the knowledge of the latest scientific research. Also, do not forget that there is no one-size-fits-all approach.

The second is to stick to a consistent, routine schedule every day, seven days a week. Dr. Yu talks about "jet lag" (social jet lag) - when people break their schedule with atypical habits, such as eating and going to bed later, waking up later, and exercising on different days of the week at different times. All these actions can lead to the same negative consequences as changing time zones. The more and more consistently you follow the regimen, the better your body will help you with this.

Third - applying the knowledge gained from scientific research - the data on nutrition, sleep and exercise are detailed below. Many of the lifestyle changes that research has shown involve changes in eating habits - for example, eating a bad idea before bed. It is fraught with negative health consequences. Eat small meals early and late in the day, which is easy enough to try. The same applies to sleep - you must follow the regime and sleep at least 7-8 hours. At worst, you will feel rested, and at best, you will improve your prospects for a healthy life.

The main thing: sleep, food and sports are the basis of a healthy lifestyle.

DREAM

The most important thing you can do is maintain a consistent sleep and wake schedule and get enough sleep - 7-9 hours of sleep is considered normal for an adult. Research findings on sleep deprivation and sleep disturbances indicate that sleep deprivation and sleep disturbances negatively affect mood, concentration, and are associated with chronic illness. What's more, some scientists speculate that circadian mismatch caused by social jetlag may be widespread in Western society and contribute to health problems.

So what time should you go to bed? Typically, the body starts producing melatonin at 9:00 pm. This is a signal - you need to finish everything and go to rest. The secretion of melatonin ends around 7:30 in the morning, and during the day, melatonin is practically not present in the body. Adjusting personal preferences based on your natural tendencies is key to avoiding sleep disturbances (such as waking up during sleep) and maintaining optimal health.

And finally, light. The cycle of day and night is not the only factor affecting the human body, as we are constantly faced with artificial lighting, and yet it plays a primary role. Getting enough natural light early in the day and avoiding unnatural lighting (such as blue light from a smartphone screen) in the evenings helps keep your circadian rhythms healthy.

Key points: Get enough sleep and make sure your sleep and wake time stay the same seven days a week. If you are sleep deprived, immediately start restoring your regimen, otherwise you risk jeopardizing your health in the long term.

NUTRITION

Generally speaking, research shows that eating high-calorie foods is best in the morning. Try to have your evening meal well before bed and less high in calories. If you can get everything done around 6:00 pm or 7:00 pm and give your body 12-14 hours to rest, you will see short-term and long-term health benefits.

In part, the fact is that your liver's internal clock does not work at night. The liver stops producing enzymes to convert calories into energy; instead, it produces enzymes to store energy. If you eat a lot before bed, your liver is forced to work overtime and you end up conserving more energy than you expend.

Another important decision you can make (besides eating healthy) is timing your daily meal. While data is still limited, animal studies and Dr. Panda's work suggest that “time-limited eating” is an easy and potentially beneficial lifestyle change. The optimal solution depends on your goal. But if the goal is to improve your overall health, then it is better to start at 8-9 hours. But, in terms of long-term compliance, it may be advisable to start at 10-12 hours.

Key point: Eat more during the day, not before bed. To improve your health, start eating at 10-12 hours.

SPORT

While some studies show that anaerobic performance peaks in the afternoon, there is no consensus among experts on the link between circadian rhythms and exercise - with the exception of the presence of a molecular clock in skeletal muscle.

And, just like the effects of lighting and meal times, exercise timing also plays an important role in maintaining healthy circadian rhythms.

The main thing: exercise regularly, and leave anaerobic activity for the afternoon.

CONCLUSION

Research into how circadian rhythms work is fairly straightforward.“Your internal clock is designed to burn energy during the day and to restore energy during the night,” says Y. The better the timing, the less wear and tear on the circadian clock. Although the internal clock is stable, consistent disruption to the regimen can lead to long-term health problems.

“When we are young, the body can handle a lot,” says Yu. “But that doesn't mean everything is okay. It is like fuel consumption: you expend too much energy on arrhythmic activities, which will lead to problems with the functioning of circadian rhythms in the future.”

You will not shorten your life by five years by eating late, but there are dedicated hours in your body to protect your health and minimize disruption to your physiology. Be kind and considerate to yourself and you will see the result.