Жировые клетки необходимы для здоровья организма

Questions about how much weight is considered overweight or normal, what functions adipose tissue performs in the human body and what is its role in ensuring the health of the body, are constantly in the focus of attention of scientists. One of the recent studies showed that the cells present in adipose tissue are important for immunity and protect us from infections, many of which are very dangerous.

What is our adipose tissue made of? The bulk of the cells that make up it — These are adipocytes, or fat cells. Adipose tissue is widely distributed in the body: normally, it accounts for about 15 & ndash; 20% of body weight in men and 20 & ndash; 25% — among women. There are two types of adipose tissue — white and brown. Adipocytes perform many functions: accumulating fats, they play the role of energy reservoirs; provide thermal insulation and protection of organs from mechanical damage; participate in endocrine regulation.

Previously, it has been suggested that adipocytes are also immunologically active cells. A recent study by scientists from the USA showed that adipocytes can protect the body from the development of dangerous skin and invasive infections caused by Staphylococcus aureus.

Fat cells as protection against bacteria

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In general, several types of cells are involved in the body's defense against harmful microbes. Since the microbe divides very quickly, it is necessary to provide an equally rapid local immune response to infection. Epithelial cells, mastocytes (mast cells) and tissue leukocytes are involved in this process. It is also important to have time to limit the spread of infection until other protective cells arrive in time to help — neutrophils and monocytes.

The main mechanism for limiting pathogen growth is the secretion of antimicrobial peptides by cells. Antimicrobial peptides play a critical role in limiting the spread of bacteria across the skin and mucous surfaces, as well as preventing their spread to deep tissues where infection can develop.

Staphylococcus aureus, or Staphylococcus aureus, — it is one of the most famous and dangerous microbes. It is the main cause of most human skin and soft tissue infections, causing focal and systemic diseases. Often this microbe is the cause of septic shock — deadly complication of serious infectious diseases.

So what makes adipocytes remarkable as cells that help our body fight bacteria? Researchers have found that, on the one hand, already mature adipocytes present in the host at the time of infection respond to infection. On the other hand, infection accelerates the synthesis of new adipocytes.

Exploring Staphylococcus aureus and infecting the skin of mice with them, scientists noticed one interesting feature — in response to infection, the subcutaneous fat layer of the mouse increased markedly. The number of adipocytes also increased. After infection with Staphylococcus aureus, adipocytes begin to gradually increase in size, that is, the increase in adipose tissue is partly caused by hypertrophy of already mature adipocytes.

Skin cells isolated from a bacterium-infected area have been shown to have greater adipogenic potential (i.e., adipocyte cells there divide faster than usual) compared to cells from an uninfected area. There is also an increase in the number of transcription factors necessary for the differentiation of preadipocytes (predecessors of fat cells) into adipocytes.

To identify proliferating (that is, actively dividing) preadipocyte cells, scientists used bromodeoxyuridine (NDU, BrdU). BDU is able to replace thymidine during DNA replication, thus integrating into new DNA. Subsequent immunohistochemical staining with antibodies to bromodeoxyuridine allows detection of the incorporated modified nucleoside, and thereby reveals proliferating cells.

It turned out that mice infected with staphylococcus aureus significantly increased the number of cells with nuclei containing BrdU. This supported the idea that some of the adipocytes were synthesized de novo in response to an infectious agent. It has also been found that impaired adipogenesis is accompanied by increased sensitivity to staphylococcal infection and causes systemic bacteremia (bacteria circulation in the blood).

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Increase in the number of adipocytes during infection with staphylococcus aureus. And — staining of mouse skin with hematoxylin and eosin. Ctrl — control, day 1 and day 3 — demonstrating an increase in the adipocyte layer after infection with S. aureus; B— the number of adipocytes in mice of the control group (Ctrl) and mice infected with staphylococcus aureus (SA).

What makes adipocytes strong against infections

The next question that interested scientists, — How can adipocytes protect the body from infection? It was found that in differentiated adipocytes, the amount of the antimicrobial cathelicidin peptide (cathelicidin antimicrobial peptide, Camp) sharply increased, while the amount of other antimicrobial peptides remained the same. Similar experiments on cell culture of human adipocytes also showed the presence of a cathelicidin precursor in them.

It turned out to be interesting that if Staphylococcus aureus is sown on the same nutrient medium where cathelicidin-secreting adipocyte precursors had previously grown, the growth of bacteria is greatly slowed down. Mice specifically inhibited in fat cell growth showed reduced resistance to staph, and this directly correlated with a decrease in cathelicidin in their body fat.

Thus, it can be said that the local increase in subcutaneous adipocytes is an important process in the body's response to skin infection. Previously, it was known that adipocytes are able to secrete bioactive substances — adipokines and cytokines that mediate various post-traumatic immune responses. This study only confirms these facts.

Local thickening of subcutaneous fat provides cathelicidin synthesis in response to infection. Also, this reaction may have indirect benefits for immune defense, for example, promote the formation of reactive oxygen species, radicals and nitric oxide, which have bactericidal activity (induce the so-called oxidative burst).

However, all this does not mean that now it is urgent to gain weight. There are two reasons for this:

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1. A sharp local increase in the level of cathelicidin more effectively provides antimicrobial functions than a small increase in systemic cathelicidin as a result of obesity. For obese mice, the data was depressing — the antimicrobial peptides they produced were "defective", making these mice more susceptible to infection.

2. Cathelicidin — pro-inflammatory substance, that is, it contributes to the process of inflammation. That is why people who are obese often have chronic inflammation reactions in the body.

The output is simple — everything is a good measure, and you need to look for some kind of golden mean. Of course, exhausting your body with diets cannot lead to anything good. Just like obesity does not contribute to overall health.

Eat right, stay healthy and don't worry if you have an extra wrinkle — perhaps right now the body is helping you. So support him in this endeavor, eat some vitamin fruit and say "thank you" to your useful adipocytes.

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