Brown fat in humans: a description, functions and features

What is brown fat? What functions does it perform? These and other questions will be answered in the article. In the human body there are two kinds of fatty substance: brown (BAT - due to the burning of fat provides thermogenesis and creates heat) and white (WAT - is designed for energy storage). In obese people, as a rule, brown lard is less, and white - more.

Function

Brown fat allows the body to maintain a constant temperature. This mechanism is called thermogenesis. There are two types of thermogenesis: contractile (znobit), in which the formation of heat occurs due to the reduction of skeletal muscles (a particular phenomenon is muscular cold tremor), and non-reduced (brown lard activity).

To effectively combat certain ailments, the body of a person raises its temperature on its own. If someone suffers a fever, his thermoregulation system is quickly reorganized, activated and begins to operate at a higher level. That's why the body temperature to 38.5 degrees is not worth knocking over.

Anatomy

Previously, brown fat was found in animals. In those animals that fall into hibernation in winter, this substance is best developed, since in this period the metabolism slows down. In view of this, it is impossible to maintain body temperature with muscle contractions.

Also, brown fat is important when waking the animals in the spring: with the help of the heat generated by it, the body temperature increases significantly, which causes the animal to wake up.

Owners

Quite recently it became known that brown lard is only available to children. It helps them to get used to the new environment after they are born. In newborns this substance is located in the area of the kidneys, neck, along the upper back, on the shoulders, and is about 5% of the body weight.

Also in the body of infants, brown fats are sometimes mixed with white. For babies, the brown substance is of great importance, since it protects them from hypothermia, because of which premature babies often die. Due to this component, newborns are less sensitive to cold than older people.

Cells of brown fatty deposits have a unique quality - they contain a huge amount of mitochondria (organelles that contribute to the accumulation of energy). Thanks to them they, in essence, have their own color. Mitochondria contain a specific protein UCP1, which, bypassing the stage of ATP synthesis, instantly transforms fatty acids into heat.

Triglycerides (lipids) found in fat are a material from which heat can be produced (ATP). When a baby needs a lot of energy (for example, to keep warm), fats undergo lipolysis. As a result, fatty acids appear, which UCP1 in brown fat cells transform into heat. As a result, there is a decrease in the stock of fatty deposits. First, triglycerides are consumed in the brown substance, and when the lipid stocks begin to melt, then in the hateful white.

As a result, the body reduces its weight. However, for the effectiveness of the process, the baby born in the world should eat well (activation of lipolysis requires energy) and breathe normally (oxygen is required for the transformation of fatty acids).

Unfortunately, in the adult this mechanism is gradually weakening. Already a couple of weeks after birth, a shiver (reaction to hypothermia) replaces the effect of the brown substance, especially if the kids are warmly dressed and kept in a hot room.

Adults

Today it was found that brown fat in an adult man is available. For a long time it was believed that this substance loses its significance by the end of the first year of people's life. However, in 2008, experts determined that brown adipose tissue does not just stay in the body of adults (this became known back in 1908), but is also activated by cold.

This discovery was made using a new technology to visualize active metabolism in tissues. Emission-positron and computed tomography were used, which showed that in the adult body there are about 20-30 grams (so little) of brown functional fat, mainly in the supraclavicular zone.

It is known that PET-CT fixes metabolic activity of the tissue. Physiologist Wouter van Marken Lichtenbelt reported that a group of young people (24 people) were given the exact dose of radioactive glucose. This was done in order to further be able to detect active brown fat using a specific device.

After that, the study participants were led into a room, the temperature in which did not exceed 16 degrees. CT scan showed that under the skin of the chest, neck and abdomen of 23 people is located a fat "useful" tissue that works by warming people in a cold room.

The physiologist said that the specialists were very surprised to see that there were so many of them and so many people. When, at room temperature, three participants were examined, no brown substance was found. Experts believe that the fabric has not disappeared, but just stopped working.

Efficiency

So, you know where a person has brown fat. It is equal to no more than 1-2% of body weight. And yet, when the sympathetic nervous system stimulates this tissue in supercooled mammals, accustomed to cold, it increases its heat production. The energy generated in this way can reach one-third of all the additional heat created in the body. When brown fat is activated, it spends up to 300 watts (some called 400 watts) per kilogram of adult weight.

It is known that a man of average weight at rest burns about 1 kW of energy. Activating brown fat, you can lie on the bed and spend twenty times more strength than before.

Fat Burning

What are the functions of brown fat? It helps to eliminate fat. If it is activated, fatty acids from white adipose tissue are pumped into the brown one. The white substance is deposited in capsules and glands of internal organs, under the skin. Brown, instead of accumulating energy, burns it in huge quantities. As a result, heat is released. This process is called thermogenesis, which begins its work because of excessive consumption of food.

conclusions

White and brown fat are two different substances. Oxidizing capacity of brown matter is 20 times greater than that of white matter. In brown tissue thermogenesis is affected by the protein thermogenin, which promotes the separation of respiration and oxidative phosphorylation.

So, we found out what brown fat is. How to increase its number in the human body to effectively fight obesity? To solve this problem, scientists use not only medicinal, but also surgical means: with the help of liposuction they take the usual white fat, transform it into brown, and again implant the person.

Theoretically, in order to lose weight, you must either increase the activity of the brown substance at normal temperature, or increase its number, or perform both the first and second.

Specialists of the Diabetes Association of the United States believe that brown fat contains very important reserves for patients suffering from diabetes and obesity. It is also known that in a full person, the activity of brown fat is suppressed, and its quantity is reduced. Therefore, in the near future, the emergence of new medicamental and other methods of accumulation and activation of this "useful" substance in adults.