How circadian rhythms, sleep and the endocrine system are connected
circadian rhythms – These are cyclical changes in biological processes in the body associated with the change of day and night. This is the way our planet is organized: the Earth, rotating around the sun, causes daily fluctuations in illumination. All living things – bacteria, fungi, animals, people – have had to adapt to this characteristic of the Earth.
The work of circadian rhythms support cellular internal clock – genes that influence not only a trait, but the behavior of the whole organism. The main driver of circadian rhythms in mammals is suprachiasmatic nucleus of the hypothalamus (SHG). It receives information from the photosensitive cells of the retina and from other receptors about external light signals. At night, the SHG gives the command pineal gland produce the hormone melatonin. As morning comes and light levels rise, melatonin secretion decreases. This is how the sleep-wake rhythm is formed.
Per day for one adult product about 30 mcg of melatonin, but at night its concentration is ten times higher than during the day. With a reduction in sleep duration, melatonin production during the night decreases significantly and approaches daytime levels. This hormone plays a huge role in the life of the body. Melatonin strengthens immunity, acts as an antioxidant and fights oxidative processes in the body caused by free radicals.
It also affects the functioning of the endocrine system. Melatonin informs information about the rhythms generated in the SCN to other organs, including the endocrine glands.
Normally, the cyclical nature of all processes in the body, including the production of hormones, conjugated with the sleep-wake rhythm. In people with deprivation and sleep disorders, this rhythm is disturbed, which leads to malfunction of the endocrine glands, abnormal hormone levels and the development of endocrinopathies.
Lack of sleep is one of the causes of obesity
TRAIN called Obesity is the main threat to human health in 2022. According to the organization, more than 1.9 billion adults worldwide are overweight. Of these, around 650 million are obese. The situation of childhood obesity is no better: in the European region, one in three children between the ages of 6 and 9 It has overweight or obesity. Scientists suggest that one reason for global obesity rates is the high prevalence of sleep deprivation.
The less a person sleeps, the faster they gain weight. Clinical research showthat sleep duration of 5 hours or less per day increases the likelihood of developing obesity in men by 3.7 times, in women by 2.3 times.
Lack of sleep promotes childhood development and obesity. Eleven cohort studies in children and adolescents found a significant association between sleep deprivation and weight gain.
Sleep deprivation increases the risk of obesity in children more than in adults. Children’s bodies are very sensitive to lack of sleep. Scientists suggest that sleep deprivation can alter the functioning of the hypothalamus in children, which regulates eating behavior and energy expenditure.
There are mechanisms that explain the link between sleep deprivation and obesity:
- Lack of sleep interferes with synthesis leptin And ghrelin. Leptin is produced by adipose tissue and is responsible for appetite suppression. Ghrelin is synthesized in the gastrointestinal tract and is intended to stimulate the appetite. Clinical studies show that sleep deprivation significantly reduces leptin levels and increases ghrelin levels. This leads to a constant feeling of hunger and increased appetite. A person starts eating more often and gains weight. Additionally, the increased production of ghrelin increases the craving for high-calorie foods, which also increases the risk of obesity.
- It also stops production somatotropin (growth hormone), which promotes the breakdown of fat and an increase in the ratio of muscle mass to fat. Growth hormone is produced by the pituitary gland around the clock, but its highest concentration occurs at night. With sleep deprivation, growth hormone synthesis is dramatically reduced. This leads to the accumulation of fat in the body with a simultaneous decrease in muscle mass.
- Lack of sleep contributes to a sedentary lifestyle. American scientists at Cleveland University Hospital conducted A 16-year study of over 68,000 nurses. Every two years, using a questionnaire, the scientists tracked sleep duration, weight, physical activity and other indicators. At the end of the study, the data analysis showed an inverse relationship between sleep duration and weight gain. One of the reasons was the lack of physical activity. If a person does not sleep regularly enough, they lack the strength and motivation to lead an active lifestyle. With lack of sleep, two desires dominate: eating and lying down.
Some sleep disorders make it difficult to lose weight. At the National Medical Research Center of Endocrinology It was carried out study of 200 obese people enrolled in a weight loss program. Insomnia (insomnia) was detected in 17% of subjects, in a third – obstructive sleep apnea (AS WELL AS). A quarter of the patients had both diseases.
Insomnia leads to mental disorders, increased anxiety, emotional overeating, frequent evening and night snacks. All this reduces the effectiveness of obesity treatment.
Sleep apnea had no effect on mental health, eating behavior, or the effectiveness of obesity treatment. But patients with this disease had various endocrine disorders:
- low testosterone levels in men;
- low levels of IGF-1 – a hormone that stimulates the growth of bones and tissues, contributes to increase muscle mass;
- high insulin levels between meals;
- high concentration of cortisol in urine at night.
Sleep disturbances and DM 2
Type 2 diabetes mellitus (DM 2) is another plague of our time. According to the WHO, type 2 diabetes suffering nearly 250 million people in the world and by 2025 their number will increase by 1.5 times.
Meta-analysis of 36 studies shownthat sleep disturbances are as strong a trigger for type 2 diabetes as traditional risk factors, which include being overweight, heredity, and a sedentary lifestyle.
The determinant of DM 2 is obstructive sleep apnea. Clinical research to demonstratethat 15-40% of people with OSAS develop diabetes over time. And the more pronounced a person’s breathing disorders during sleep, the higher the likelihood of type 2 diabetes.
One of the mechanisms by which OSAS leads to diabetes is sleep fragmentation. Due to the regular pauses of nighttime breathing, sleep is disrupted. As a result, a person does not go through all stages of sleep and does not get the right amount slow sleep.
During sleep fragmentation, the number of macrophages in adipose tissue increases and other processes characteristic of oxidative stress are observed, in which cells are destroyed under the influence of reactive oxygen species (free radicals). Oxidative stress leads to insulin resistancewhich, in turn, contributes to the development of type 2 diabetes.
It increases the risk of developing type 2 diabetes and sleep deprivation. With short sleep, the risk of obesity increases, and obesity is a major cause of developing type 2 diabetes. In addition, with lack of sleep, the level inflammatory cytokinesactivated sympathetic nervous systemwhich negatively affects metabolism.
Sleep disturbances and metabolic syndrome
metabolic syndrome (SM) is a chronic metabolic disorder, which is accompanied by the development of various pathological conditions. Its main clinical sign is abdominal obesity. Additional diagnostic criteria:
- hypertension;
- high amount of triglycerides in the blood;
- low levels of “good” cholesterol;
- elevated blood sugar on an empty stomach and / or two hours after a meal.
The diagnosis of MS is established in the presence of abdominal obesity and two or more additional features.
According to the INTERHEART study, more than a quarter of adults worldwide suffer from metabolic syndrome. In Russia, 40% of the population has two diagnostic signs of MS, 11% – three or more signs. Metabolic syndrome is detected in one in two people with obesity and in 80% of people with type 2 diabetes.
Clinical research show: The risk of developing metabolic syndrome in people with a normal sleep duration is lower than in those with little sleep. At the same time, oversleeping also increases the risk of developing the disease.
Scientists supposethat prolonged sleep reduces energy expenditure, which is associated with obesity and its consequences, including metabolic syndrome.
Exists link between social jet lag and metabolic syndrome. social jetlag – a mismatch of the human circadian rhythm with the natural daily rhythm, caused by a work or study schedule. It is similar to jetlag that occurs after a long flight, but is not associated with the time difference in different parts of the Earth, but with the mismatch of biological clocks with social needs. Clinical studies show that social jet lag lasting ≥ 2 hours increases the risk of developing metabolic syndrome as well as prediabetes and diabetes.
Shift work negatively affects the metabolism, which often leads to the fact that a person sleeps during the day and eats at night. At night, leptin levels drop, so your appetite goes up. This leads to overeating, weight gain and thus impaired glucose tolerance, insulin resistance.
Many cross-sectional studies show a significant association between insomnia and MS. This relationship persists even with normal sleep duration. Insomnia leads to a violation of blood sugar, a decrease in the level of “good” cholesterol and an increase in the content of triglycerides in the blood. All this contributes to the development of the metabolic syndrome.
How to improve sleep and reduce the risk of endocrinopathies
Restoring normal sleep allows you to improve eating behavior, reduce the risk of obesity and other endocrinopathies. You can get rid of sleep disorders not only with the help of drug therapy, which often leads to side effects. There is a safer way: respect for sleep hygiene.
University of Chicago Scholars conducted A 3-week study of overweight young adults who slept less than 6.5 hours. Each subject was given individual recommendations for improving sleep hygiene. After following the recommendations, the experiment participants started sleeping an average of 1.6 hours more, which reduced their overall appetite by 14% and the craving for sweet and salty foods by 62%.
Similar results have been received and in a study by researchers at King’s College London, an increase in short sleep reduced the amount of fat and carbohydrates consumed.
Therefore, the restoration of normal sleep duration helps to reduce the calorie content of the diet and thus reduces the risk of obesity and other endocrine disorders associated with it.
Researchers at the Free University of Brussels conducted study among men with sleep deprivation. After improving sleep hygiene and increasing its duration by 1 hour, participants in the experiment increased their tissue sensitivity to insulin and decreased the likelihood of type 2 diabetes.
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