I’ll start with a quote from a biochemistry textbook edited by Severin: “Fat molecules in adipocytes are combined into large fat droplets that do not contain water, and therefore are the most compact form of storage of fuel molecules. It is estimated that if the energy stored in fats were stored in the form of highly hydrated glycogen molecules, a person’s body weight would increase by 14-15 kg.”
Another introductory quote: “The mechanism of switching energy storage mode to energy wasting mode may be a therapeutic target in the fight against obesity.”
Thermogenesis and thermogenin
Fat – effective method store energy. To lose fat, we need a way to spend/dissipate this excess energy. Mammals are lucky in that homeothermy (constant body temperature) gives us a mechanism needed to survive in cold environments by which our mitochondria can dissipate energy primarily from fats as heat. The so-called “cold thermogenesis” or non-shivering thermogenesis.
Uncoupling protein 1 (UCP1), also known as thermogenin, can dissipate energy.
Brown fat thermogenesis is associated with thermogenin (UCP1), a protein in the inner membrane of mitochondria.
UCP1 improves inner membrane conductance to H+, which dissipates the mitochondrial H+ gradient. This means that even with excess ATP, fats will continue to “burn” in the mitochondria, and the resulting energy will be dissipated as heat.
The path looks something like this:
Cold stress
Norepinephrine
Adrenergic stimulation of fat droplets in brown adipose tissue cells
Long-chain acids from the cell's fat droplet stimulate thermogenin
Thermogenin (UCP1) dissipates the H+ gradient
Fats are processed (even with excess ATP) into heat.
UCP1 is subsequently inhibited by cytosolic purine nucleotides. The mechanism by which fatty acid this is overcome remains unknown.
The mechanism of thermogenin activation is naturally more complex. We'll look at other factors a little later. The role of free fatty acids in the direct activation (join) of UCP1 was shown by Andriy Fedorenko and colleagues.
Figure 1. Free fatty acid from the fat droplet activates thermogenin (UCP1), which leads to the dissipation of energy in the form of heat.
The emergence of brown fat in the process of evolution and its role
Endogenous heat production provides mammals with a number of evolutionary advantages, but a significant part of the energy must be spent on maintaining body temperature in a colder environment. Most of the thermo-sensors in our body react to cold.
There are 2 main mechanisms of response to cold - shivering and non-shivering. Through shivering, when a cold stimulus causes muscles to contract rapidly, converting mechanical energy into heat. And thermogenesis without muscle contractions caused by burning fat for heat. This mechanism is more energy efficient. It involves brown fat and thermogenin.
The oldest traces of thermogenin date back to 400 million years BC. About 170 million years ago, monotremes separated from the mammalian lineage. They contain traces of UCP1, but UCP1-positive adipocytes have not been found in them to this day. The initial stage of UCP1 mRNA development was discovered in a South American marsupial. In the Australian fat-tailed marsupial mouse, a similarity of brown adipose tissue was found, but it did not have the adaptive function of cold-norepinephrine_stress-activation_UCP1. Afrotherium has thermogenic brown fat when low temperatures environment. In the Hottentot golden mole, brown fat thermogenesis is considered the main adaptive mechanism to cold. The evolutionary path of thermogenic brown fat is schematically shown in the figure below.
Figure 2. Emergence of cold-activated thermogenic brown fat during mammalian evolution.
Types of adipose tissue
Figure 3. Adipose tissue types and plasticity in response to temperature changes.A) Main morphological and functional differences between brown, beige and white adipocytes. B) Anatomical location of the main deposits of adipose tissue. Brown:iBAT – interscapular brown;sBAT – subscapular brown;cBAT – cervical; Subcutaneous white:asWAT – anterior subcutaneous white;ingWAT – inguinal; visceral fat:mWAT – mesenteric;rWAT – retroperitoneal;pgWAT -perigonadal. The dotted line is the peritoneum. C) Model brown/ white fat VC57BL6 male mice 13 weeks old. In the thermoneutral zone (30 degrees, 4 weeks), brown adipocytes began to resemble white ones. From 22 degrees brown fat became active. With a progressive decrease in temperature from 22 to 6 degrees, subcutaneous white fat changes and begins to resemble brown fat. Visceral fat is generally resistant to temperature influences.
Brown adipose tissue (BAT)
Brown adipose tissue is distinguished by a large number of mitochondria, a large number of small fat droplets and high expression of uncoupling protein 1 (UCP1). Without external stimulation, brown fat is less active due to purine nucleotides. Cold stress leads to both activation of UCP1 and lipolysis, providing fuel for thermogenesis needs. Active brown fat imports glucose and fatty acids to provide additional fuel to support thermogenesis.
In humans and mice, brown adipocytes are concentrated in areas of high blood flow. The largest deposits are in the interscapular, subscapular and cervical areas. Small reserves in the area of the renal scar and aorta. Post-mortem analysis of people showed that there are deposits of brown fat around carotid artery. Until 2007, science denied the presence of brown fat in adults. There is an inverse correlation between the amount/activity of brown fat and body mass index (BMI).
BAT (brown adipose tissue) can expand due to the number of cells (hyperplasia) and due to the size of the cells (hypertrophy). Hypertrophy largely depends on the environment. Without temperature stress, brown fat is less metabolically active and accumulates fats in one fat globule. But even with a slight decrease in temperature, it has a more familiar multi-chamber morphology of fat droplets. Cold reduces BAT size through lipolysis and beta-oxidation, but prolonged cold exposure can increase brown fat mass by activating adipocyte precursor proliferation and differentiation mechanisms, i.e., increasing the number of adipocytes.
Figure 4. Distribution of brown adipose tissue in adults (left) and infants (right)
White adipose tissue (WAT)
White fat is the most common type of adipocyte, containing one large fat droplet. The main function of white adipocytes is to store “fuel” and release adipokines (such as leptin, adiponectin) to regulate energy homeostasis. The expansion of white fat (including in obesity) protects organs and muscles from lipotoxicity. WAT is usually divided into subcutaneous and visceral. An excess of the latter is associated with metabolic diseases, while an excess of subcutaneous is considered protective. White fat can expand in both cell size and quantity. The main sites of subcutaneous and visceral white fat deposition are marked in Figure 3.
Beige fat(brite, brown-in-white)
There is some debate about the origin of beige fat. Whether this is a form of white fat or a completely different form of fat that is activated by an external stimulus is important from a pharmaceutical point of view, but not from a practical point of view.
"Browning" occurs during energetic stress. Our most obvious example is hardening, when the energy from muscle contraction (shivering) is not enough to maintain body temperature. But browning also occurs under other external stresses: cancer cachexia, severe burns, physical exercise and so on.
Thermogenin (UCP1) is activated along the above chain. Cells begin to store fat and burn it to produce heat. More mitochondria appear and there are more fat droplets. Visceral fat is much more susceptible to “browning” than subcutaneous white fat.
Fat cycle
It is important to understand that it is under stress (for example, cold) that brown fat becomes thermogenic, white fat turns into beige (bright). In the absence of a stimulus, brown and beige fat begin to resemble white fat.
Figures 5. Conversions of fat types into each other in the presence/absence of an external stimulus (in particular cold).
Factors influencing the activation of brown and beige fat
Endogenous factors directly associated with cold
Figure 6. Endogenous factors influencing brown/beige fat activation. Neurons and macrophages secrete noadrenaline; the heart secretes natriuretic peptides; liver and brown fat secreteFGF21; muscles secrete irisin; thyroid T4, which is converted to T3; brown fat secretesbmp8b andvegf, which enhances thermogenic function in an autocrine manner. Orexin andBmp7 promotes brown fat formation, although its cellular source is unknown;
These and other factors are more important for researchers looking for ways pharmaceutical activation of brown fat. Trials of β3-AR agonists have not yet yielded the expected results in humans. For us, the most important activator is cold, which, among other things, promotes the growth of blood vessels in adipose tissue, which promotes oxygen delivery and heat exchange.
For further work with the literature, it is a good idea to remember the transcript coactivator PCG-1α, which is directly related to mitochondrial biogenesis and is the central transcript effector of adrenergic (stress) activation of thermogenic adipocytes.
PPAR-γ receptors, which play a role in the adipogenic mechanism.
FGF21 factor will be found in the literature on metabolic health (diabetes in particular), this factor affects the improvement of insulin sensitivity, glucose uptake by peripheral cells, and weight loss.
Natriuretic peptides reduce blood volume and pressure, promote sodium excretion by the kidneys, and promote lipolysis. It is logical to assume that there must be a dialogue between cardiomyocytes and adipose tissue to protect the heart muscle during cold weather.
Those who are very concerned should google the factors KLF11, PRDM16, EBF2, EWS/YBX1/BMP7 axis, IRF4, ZFP516 or read about them at the link below.
All of the above factors are modulated by cold as well as pharmacological intervention. Therefore, from a practical point of view, it is not worth spending too much time on them.
Exogenous factors that complement cold well
Sympathetic stimulation of β3-adrenergic receptors is more important for the conversion of white fat to beige (or activation of beige) than for brown fat.
Hot peppers and stress are additional stress, with this at the level of formal logic everything is clear.
Kim and colleagues write that fish fat activates the sympathetic nervous system, increases oxygen consumption (read fat oxidation) and rectal temperature with activation of β3-AR and thermogenin (UCP1). As a meat lover, I want to note that the fats of grass-fed beef (read DHA, omega-3) and grain-fed beef (omega-6, unsaturated fatty acids) are very different not only in taste, but also in color. When grass-fed, the fat is brown, and while texturally it is not as tender as its less healthy counterpart, it is much tastier. Grain-fed fat is white.
I don’t want to consider pharmacological exogenous agents for two reasons: the scientific side has not yet come to guaranteed working solutions and there are proven and effective means, which do not require farm support.
The ketogenic diet and brown fat
What is brown fat? What functions does it perform? We will answer these and other questions in the article. There are two types of fatty substance in the human body: brown (BAT - provides thermogenesis and creates heat) and white (WAT - intended for energy storage). Obese people tend to have less brown fat and more white fat.
Brown fat allows the body to maintain a constant temperature. This mechanism is called thermogenesis. There are two types of thermogenesis: contractile (shivering), in which the formation of heat occurs due to the contraction of skeletal muscles (a particular phenomenon is muscle cold tremors), and non-contractile (the activity of brown fat).
For effective fight With some illnesses, the human body independently increases its temperature. If someone suffers from a fever, their thermoregulatory system quickly reorganizes, activates, and becomes more effective. high level. That is why you should not lower your body temperature to 38.5 degrees.
Brown fat was first found in animals. In those animals that hibernate in winter, this substance is best developed, since in this period metabolism slows down. Because of this, it is impossible to maintain body temperature by muscle contractions.
Brown fat is also important when animals awaken in the spring: with the help of the heat it generates, body temperature increases significantly, which is why the animal wakes up.
Quite recently it became known that only children have brown lard. It helps them get used to their new environment after they are born. In newborns, this substance is located in the kidneys, neck, along the upper back, on the shoulders, and makes up about 5% of body weight.
Also, in babies' bodies, brown fat is sometimes mixed with white fat. For babies, the brown substance is of great importance, as it protects them from hypothermia, due to which premature babies often die. Thanks to this component, newborns are less sensitive to cold than older people.
Brown cells have a unique quality - they contain a huge number of mitochondria (organelles that contribute to the accumulation of energy). Thanks to them, they essentially have their own color. Mitochondria contain a specific protein, UCP1, which, bypassing the stage, instantly transforms fatty acids into heat.
Triglycerides (lipids) found in fat are the material from which heat (ATP) can be produced. When a baby needs a lot of energy (for example, to stay warm), fats undergo lipolysis. As a result, fatty acids appear, which UCP1 transforms into heat in brown fat cells. As a result, there is a decrease in fat deposits. First, triglycerides in the brown substance are consumed, and when the lipid reserves begin to melt, then in the cold white substance.
As a result, the body reduces its weight. However, for the process to be effective, the baby who is born must eat well (energy is needed to activate lipolysis) and breathe normally (oxygen is required to transform fatty acids).
Unfortunately, in adults this mechanism gradually weakens. Already a couple of weeks after birth, trembling (a reaction to hypothermia) replaces the action of the brown substance, especially if the babies are warmly dressed and kept in a hot room.
Today it was discovered that adults have brown fat. For a long time it was believed that this substance loses its significance by the end of the first year of human life. However, in 2008, experts determined that brown not only resides in the body of adults (this became known back in 1908), but is also activated by cold.
This discovery was made using new technology visualization of active metabolism in tissue. Positron emission and computed tomography, which showed that in the body of an adult there are about 20-30 grams (so little) of brown functional fat, mainly in the supraclavicular area.
PET-CT is known to capture the metabolic activity of tissue. Physiologist Wouter van Marken Lichtenbelt reported that a group of young people (24 people) were given a precise dose of radioactive glucose. This was done in order to further be able to detect active brown fat using a specific device.
After this, the study participants were led into a room in which the temperature did not exceed 16 degrees. CT scans showed that under the skin of the chest, neck and abdomen of 23 people there is fatty “useful” tissue that works to warm people in a cold room.
The physiologist said that the specialists were very surprised to see that there was so much of it and in such large number of people. When three participants were examined at room temperature, no brown substance was found. Experts believe that the fabric did not disappear, but simply stopped working.
So, you know where brown fat is located in humans. It is equal to no more than 1-2% of body weight. And yet, when this tissue is stimulated in hypothermic mammals accustomed to the cold, it increases its heat production. The energy generated in this way can reach one third of all additionally created heat in the body. When brown fat is activated, it expends up to 300 watts (some say 400 watts) per kilogram of adult body weight.
It is known that a person of average weight burns approximately 1 kW of energy at rest. By activating brown fat, you can lie on your bed and expend twenty times more energy than before.
What functions does brown fat perform? It helps eliminate fat. If it is activated, fatty acids from white adipose tissue are pumped into brown adipose tissue. A white substance is deposited in capsules and omentums internal organs, under the skin. Brown, instead of storing energy, burns it in huge quantities. As a result, heat is released. This process is called thermogenesis, which begins its work due to excess consumption food.
White and brown fat are two different substances. The oxidizing capacity of the brown substance is 20 times greater than that of the white substance. In brown tissue, during thermogenesis, the protein thermogenin acts, which promotes the uncoupling of respiration and oxidative phosphorylation.
So, we found out what brown fat is. How to increase its quantity in human body to effectively combat obesity? To solve this problem, scientists use not only drugs, but also surgical means: Using liposuction, they extract ordinary white fat, transform it into brown fat, and implant it back into the person.
Theoretically, in order to lose weight, you need to either increase the activity of the brown substance when normal temperature, either increase its quantity, or do both the first and second.
Experts from the US Diabetes Association believe that brown fat contains very important reserves for patients suffering from diabetes and obesity. It is also known that full man Brown fat activity is suppressed and its amount is reduced. Therefore, in the near future, new medicinal and other methods of accumulating and activating this “useful” substance in adults may emerge.
Brown fat– adipose tissue present in the body of mammals along with white fat. Thermoregulation function – converts calories into heat. Contains many capillaries, since the need for oxygen saturation is higher than that of the fat layer white. The brown (brown) color comes from iron located in the mitochondria. Brown fat is natural fat burner, as it converts white fat lipids into energy.
In a newborn's body, brown fat makes up 5%. Due to their small body size, infants spend heat intensively; the body does not regulate temperature sufficiently (children do not know how to shiver when they feel cold). Hypothermia is dealt with by islands of brown fat, which are concentrated around the neck, on the back and shoulders.
As you get older, this type of fat decreases, making it more difficult to lose weight. Therefore, problems with overweight occur in middle-aged and older people more often than in young people. The amount of brown fat is affected genetic predisposition, gender (men have less than women), glucose balance and insulin sensitivity (the lower the sugar level, the thicker the “useful” adipose tissue), taking beta blockers, content, irisin production due to physical activity (increases) .
A decrease in body temperature causes brown fat to become more active, replacing white fat more intensively and producing heat to restore balance. This property is used to build subcutaneous brown fat, which helps fight excess weight. Metabolism accelerates due to cold, excess reserves are burned.
Perform procedures to cool the body gradually, otherwise you will catch a cold instead of losing weight. Receptors that inform the brain about a decrease in ambient temperature function on the surface of the skin. Hypothermia of the core of the body is dangerous.
Melatonin– a hormone responsible for regulating circadian rhythms. Slows down aging, affects immunity, endocrine processes, digestion, blood pressure. An increase in this substance in the body has a beneficial effect on the formation of brown fat deposits. The deficiency of the hormone is compensated by dietary supplements. Obesity ( interesting fact, those with obesity of 2nd degree and above are not accepted into the army) - a direct consequence insufficient production melatonin. A natural way to cope with a lack of melatonin is to normalize your sleep. . This will help you lose weight and cope with other problems that insomnia leads to. The importance of melatonin in the fight against excess weight is important for people over forty, since the amount of fat Brown decreases and needs to be replenished.
Measures for natural recovery sleep
Irisin converts white fat deposits into brown ones. This is a hormone released during exercise that prevents obesity. During sports or other strength activities, energy is consumed more intensely than necessary to achieve results.
Attempts to create a miracle drug for people based on irisin have not yet yielded tangible results. Human brown fat has a different composition than mouse fat; under the influence of the hormone, individual cells of “harmful” fat are replaced with “good” ones. Forced acceleration of metabolism is a gross interference in the functioning of the body; side effects outweigh the benefits. Irisin injections and brown fat transplantation as ways to combat obesity are the topic of further research and experimentation.
Brown fat is a natural aid in the fight against obesity. Increasing and activating this type of subcutaneous tissue with the help of a thermal diet, physical exercise, and normalizing sleep - natural way keep your weight normal. Proper nutrition and healthy image life will strengthen and consolidate the results.
No tags for this post.Kirill Stasevich
Doctors have every reason to believe that being overweight is not a good thing. As a rule, a whole range of disorders are associated with increased body weight: from cardiovascular to metabolic. And the number of people with one form or another of obesity is constantly growing.
How can you keep your weight within normal limits? The answer, it would seem, could not be simpler - eat less, move more. No one doubts the effectiveness of these remedies, but they do not help everyone. Some people have metabolic characteristics such that fat accumulates with any diet. Sometimes we simply cannot resist the feeling of hunger: the brain requires calories without regard to excess weight. Follow instructions regarding physical activity It’s also not always possible, especially for city residents.
Therefore, obesity has become one of the most studied topics in modern medicine, and the efforts of many researchers are aimed at finding a remedy that would help prevent fat accumulation. You can, for example, try to change eating behavior through the brain and neuroendocrine system. Another way to prevent fat accumulation is by targeting intestinal microflora, since it largely depends on it what from food will be absorbed into the blood and what not. Finally, excess lipids can simply be burned, that is, they can be broken down in some metabolic processes.
Meanwhile, fat is different from fat. What is deposited on the buttocks and waist is white adipose tissue, consisting primarily of white adipocytes (fat cells). Their function is to store a variety of lipids, and they look like a huge drop of fat. They have cytoplasm, nucleus and other components of the cell, but they huddle somewhere between the lipid mass and the membrane. Brown fat cells look different: they have several fat droplets, and in the cytoplasm there are a lot of mitochondria, which, thanks to iron-containing proteins, give the cells a darker, brown color.
From a biochemical point of view, brown fat cells are arranged in a senseless way at first glance. In their mitochondria, the connection between the oxidation of organic molecules (that is, lipids) and the synthesis of energy molecules ATP is broken. As is known, during the oxidation of molecules in mitochondria, a proton gradient is created on their internal membranes: there are more protons on one side of the membrane than on the other. This gradient is necessary for the enzyme built into the membrane to work for the synthesis of ATP: the energy stored in the chemical bonds of ATP is easily released and used in the vast majority of molecular processes in the cell. But in brown fat, the energy from oxidized products is almost not stored in ATP. But it is not wasted either, but goes into warmth.
All cells, to one degree or another, allow some portion of the energy they receive to leak into heat, but brown fat cells are specialized for this very function - creating heat from stored lipids. It is easy to guess that brown adipocytes serve important element thermoregulation systems in warm-blooded animals. In fact, zoologists have long noticed that brown fat is especially developed in animals that hibernate. “Sleeping” animals cannot maintain body temperature using other mechanisms, such as shivering, and brown fat comes in handy.
Brown fat also protects infants from hypothermia - in them it constitutes up to 5% of body weight. In adults, as was believed until recently, brown adipocytes cease to perform their function, lose mitochondria and turn into something like ordinary white fat cells.
However, a few years ago, brown fat was also found in adults. It turned out that some part of it remains in the area of the neck, shoulders and upper part chest. Moreover, it turned out that the amount of brown fat in adults increases in the cold, which is understandable, because brown fat is needed specifically for heating.
And since the “furnace” of brown fat works on lipids, the idea arose: is it possible to use it to get rid of overweight? But then we need some kind of “switch” that would activate brown adipose tissue when needed. To realize this idea, it is required, firstly, to understand the molecular and cellular mechanisms, which ensure the appearance of brown fat in the body, and secondly, make sure that it really helps against obesity and related problems with metabolism.
Although brown fat cells were found not only in special “depots”, but also in the thickness of white fat, it was believed that they still had their own special precursors, which then developed into brown adipocytes. However, researchers from ETH Zurich have found that white fat and brown fat can directly convert into each other. The experiments were carried out on mice in which individual white fat cells were monitored: when the temperature decreased, these cells “turned brown”, and when the temperature increased, they “turned white.” It turns out that brown fat can be formed directly from white fat.
Brown adipose tissue is densely permeated blood vessels; they not only bring her fuel, but also take heat with them. It was even possible to find nerve cells that give a signal for the breakdown of fats - they turned out to be some neurons of the hypothalamus. They controlled specifically the metabolic activity of brown fat cells. That is, appetite and food consumption remained the same, but more calories were burned in the brown fat “furnace”.
The brain can control brown fat not only through neural signals itself, but also through neuropeptide hormones called orexins. These neuropeptides are synthesized again in the hypothalamus, participate in the regulation of sleep-wake cycles and influence energy metabolism and appetite. It turned out that orexins directly act on white fat cells, promoting their transformation into brown adipocytes. (It is possible that the matter is not limited to direct influence alone, since orexins are included in complex system several neuropeptides that control metabolism and can act on brown fat through their “influencing agents.”) If the orexin genes were turned off in mice, the animals gained weight even with a moderate diet.
However, you should not think that brown fat is under the care of just a couple of neuropeptides and a group of nerve cells. The most active participant in the transformation of one adipose tissue into another takes the immune system. Several years ago, researchers from the University of California, San Francisco (USA) discovered that macrophages present in white fat cause fat cells to turn brown when the temperature drops. Macrophages are usually spoken of as “cleaner” cells that eliminate the consequences of “ immune wars", and their active role in metabolism has only recently been elucidated. Under the influence of special signaling proteins, macrophages force adipose tissue to burn its reserves. And just recently it was possible to link the immune signals that control macrophages with muscle function. During physical exercise and again when the ambient temperature drops, a special hormone (called meteorin-like hormone) is released from the muscles, which, through the immune signaling proteins interleukins, acts on macrophages located in adipose tissue, and then everything unfolds according to the scenario described above.
Deciphering the mechanisms that control brown fat usually involves searching for molecular “magic buttons”—regulatory proteins that can be used to activate the appearance of new brown cells or enhance their activity. Thus, recently researchers from Virginia Commonwealth University (USA) published an article in which they proposed the enzyme Tyk2 kinase to play the role of the brown fat switch. Until now, this enzyme has been studied as one of the promising anticancer proteins. (It may be recalled here that obesity often develops along with oncological diseases.) There are many such examples; reports of brown fat activator proteins appear regularly. Naturally, in each such work their effect on excess weight is tested. So far, anything that activates brown fat helps with excess weight get rid of. But does brown fat help reverse the metabolic problems that accompany obesity?
Researchers from the Dana-Farber Cancer Institute (USA) answered this question in the affirmative. They found a protein that links heat-burning calories to inflammation that begins in overgrown fat tissue. It is inflammation that is believed to provoke resistance of tissues and organs to insulin, which is a direct path to type 2 diabetes. It turned out that the TRPV4 protein, contained in white adipocytes, interferes with fat burning and promotes inflammatory processes in adipose tissue. If the synthesis of TRPV4 was suppressed, then there was no obesity or inflammation in the experimental animals, although they ate high-calorie fatty foods. In fact, other studies have also noted a connection between the activation of brown fat and the disappearance of signs of diabetes, but it was necessary to find a specific molecular link. It turned out to be TRPV4. However, it must be taken into account that research of this kind is not limited to just one link, and usually molecular biologists extract a whole signal chain by catching a link, each member of which can become a target for drugs.
Basically, such experiments are carried out on mice, so it would be reasonable to ask the question to what extent the results obtained can be extrapolated to humans. But literally in July of this year, an article was published in the magazine “Diabetes” in which employees medical department University of Texas at Galveston (USA) write about a clear connection between the amount of brown fat in a person, the level of glucose in the blood and the response of cells to insulin. The more active brown fat was, the more it was, the more calories were burned and the more actively glucose was absorbed from the blood into tissue cells. So brown fat could really be a good medical tool in the fight against obesity and diabetes, and it is not in vain that scientists are looking for a means with which they can quickly and effectively activate brown adipose tissue.
Most of these searches are aimed at target molecules involved in the management of brown fat. Different approaches differ here in effectiveness and probability side effects. For example, employees of the biotechnology company Genetech claim that they can activate brown adipocytes and normalize metabolism with just one injection of antibodies that activate cellular receptors for the hormone FGF21 (fibroblast growth factor 21). In diabetic mice that received the injection, their glucose levels remained normal for a whole month, and the mice themselves lost 10% weight. However, these antibodies have so far only been tested on animals. On the other hand, researchers from Cambridge (UK) believe that preference should be given to “their” protein called BMP8B, which not only activates brown fat, but does it very specifically - that is, by acting on BMP8B with some drug, we almost We do not risk affecting another molecular cellular process. It is also worth mentioning the recently discovered hormone irisin - it saves against obesity and diabetes by turning white fat into brown, and at the same time promotes the growth of muscle tissue. That is, the effect of this hormone is similar to going to the gym: minus fat, plus muscles.
Among different advice, how to activate brown fat, the proposal to use Viagra looks original. The fact that this legendary drug also helps against obesity was reported by researchers from the University of Bonn (Germany), who published an article last year in The Journal of the Federation of American Societies for Experimental Biology. Viagra, or sildenafil, increased the amount of brown fat in mice, and also suppressed inflammatory processes in white adipose tissue.
Well, can a person himself help increase the proportion of brown fat in the body, without waiting for medications to appear? There is such a way, and it is sports and physical education. We have already mentioned above about the meteorin-like hormone, which is released from the muscles during physical stress. Also muscle loads increase the synthesis in muscles of the transcription factor PGC-1α, which turns on genes in white fat cells that convert them into brown adipocytes. (The protein factor PGC-1α works in a signaling chain associated with the TRPV4 protein, which has been used to “link” brown fat with diabetes.)
If you don’t want to spend time on physical exercise, your friends will help you lose weight. In 2011, researchers from Ohio University (USA) found that increased social activity helps fat mice lose weight, and protects thin ones from obesity, even if fed fatty foods. Communication with other mice increased the proportion of brown fat in the animals’ bodies, and the connecting molecular link was a fairly well-known protein called “brain-derived neurotrophic factor” (BDNF), the level of which increased in nerve cells during an intense social life.
Finally, another way to activate brown fat, which naturally suggests itself, is cold. Indeed, if the activity of brown fat cells is increased by cold, then why not freeze for therapeutic purposes for those who are overweight? Employees of the University of Maastricht (Netherlands) tried to evaluate the effectiveness of this method. For 10 days, they forced volunteers to sit for six hours every day in a room with an air temperature of 15 o C. The brown fat of the experiment participants was actually activated, they stopped freezing, and their energy expenditure increased by 30%. However, it is still unclear whether such activation is enough for truly significant weight loss.
But if brown fat alone is not enough, white fat will help - it, as it turns out, can also break down fat with the release of heat if it gets cold around. Researchers from Harvard (USA) found that white adipocytes themselves, without intervention nervous system and independent of brown fat, can sense cold and participate in thermoregulation.
To be fair, there is some evidence associated with brown fat that may dampen enthusiasm for it. For example, oddly enough, in some experiments it increased the risk of atherosclerosis, provoking an increase in the proportion of “bad” fats - low-density lipoproteins - in the blood. However, these results still need to be confirmed in clinical studies.
It is possible that the diversity of lipid tissues is not limited to white and brown fat. Two years ago, employees of the Dana-Farber Cancer Institute (USA) discovered that there is also beige fat in the human body. Its cells are similar to brown fat cells and also burn excess lipids to produce heat, but differ in some significant biochemical and genetic characteristics. It is possible that those adipocytes that are considered brown in humans are actually beige. However, even if adult brown fat is indeed fake, researchers just need to switch to beige fat,” which can also be used to regulate metabolism and prevent obesity.
Fat in the human body varies in structure. Distinguishing it by color, scientists distinguish white, brown and beige fat. How to lose weight, knowing their features, read the article.
I have already written that, depending on the origin and location, there are three types of fat in the body: visceral, subcutaneous and gender-specific fat. But fat can also be classified according to its structure. According to this criterion, there are three types.
A white fat cell consists of one large fat globule. This fat is located on the hips, buttocks, around the waist, i.e. by location - this is fat, determined by gender. Subcutaneous fat is also white fat. That is, this is exactly the adipose tissue that our body stores for Emergency and which we don’t like so much.
To get rid of white fat, it is necessary, as in the case of subcutaneous fat and gender-specific fat, to simultaneously use proper nutrition and physical activity.
Brown fat cells are made up of several fat droplets. They contain many mitochondria, thanks to which these cells can consume significant amounts of oxygen. And without oxygen, fat cannot be used as an energy source.
The main function of brown fat is. That is, it comes into operation when it is necessary to “warm” the body. The most brown fat is found in animals that hibernate and, accordingly, cannot increase their temperature through physical activity.
In humans, brown fat is found in newborns and accounts for up to 5% of the total weight. It helps children support required temperature bodies until other mechanisms are developed. Localization of brown fat– area of the neck, shoulder blades, collarbones. However, very quickly children develop a more advanced mechanism for maintaining temperature - shivering, and gradually brown fat stops performing its function.
From the point of view of people watching their figure, this fat is preferred, since brown adipose tissue in the human body “voluntarily” strives to be used for the benefit of our “warmth”. The question is different:
Science has been looking for the answer to this for quite a long time. For a long period of time, it was believed that brown adipose tissue was absent in adults. Then, at the beginning of the 20th century, it was still discovered in very small quantities in the area of the collarbones, neck and shoulder blades, but they did not figure out how to influence this fat and, ultimately, decided that due to the small amount it was impossible to activate it. They forgot about brown fat for quite a long period of time.
But the turning point occurred in 2008. The topic of brown fat became relevant, as often happens in science, completely by accident. Studies were carried out using positron emission tomography and discovered not only, as was then thought, brown fat in the body of an adult, but also an increase in the number of its cells with decreasing temperature.
Another feature was that the more “slender” a person’s body type was, the more brown fat was found in his body. From the point of view of everyday logic, this is not surprising, because brown fat provides the body with the function of maintaining temperature, and it is much more difficult for thin people to stay warm.
It is not at all surprising that these features were not discovered earlier. It just never occurred to anyone to conduct research in low temperature conditions.
After these discoveries, it was decided that brown adipose tissue cells are capable of being synthesized from white adipose tissue when the temperature decreases. Maybe it was then that recommendations appeared: if you want to lose weight, you need to be in a cool room.
Later, it turned out that the fat found during research in the body of adults has a structure different from brown. This kind connective tissue called beige fat. The functions of beige fat are the same as brown fat - heat generation. In principle, everything that was said about brown fat in an adult is correct, they simply call it beige now and some clarifications have appeared regarding the mechanisms of its work. It was because of the introduction of the new concept that great confusion began in the sources of information, because Many people still talk about only two types of fat – white and brown. And of course, you will have to wait a long time for a complete update of information.
The myth that (now) beige adipose tissue can be formed from white adipose tissue has also been dispelled. In reality, beige fat has precursor cells that sit among the white fat cells and simply lie dormant until a factor appears that activates them. After which they quickly “wake up”, “grow” and begin to perform their functions.
Based on all of the above, we can conclude that in order to lose weight, you need to activate beige fat cells, which will produce heat, and therefore spend a lot of energy. Accordingly, it is necessary to create conditions with a lower temperature. However, freezing in order to lose weight is not the wisest decision. But no one talks about living in a refrigerator. A temperature of +19° is already considered not very comfortable for the body and requires more heat generation. That is why, starting in autumn, we usually want to eat more - more energy is spent on heating the body. Work out outside whenever possible and your energy expenditure will increase.
Of course, you won’t lose much weight just by ventilating the premises :) But we still have the opportunity to train to get rid of fat!
Relatively recently, scientists discovered the hormone irisin. It is assumed that it activates fat metabolism and triggers thermogenesis processes, which means the work of beige fat cells. And most importantly, irisin begins to be produced in response to physical activity.
It must be recognized that to date, the bulk of research on brown/beige fat has been carried out on mice and rats. But since scientists consider their results to be equivalent for humans, perhaps we should trust them :)
