Hello! I have been working as a doctor for 22 years. My name is Georgy Olegovich Sapego. In this article I will tell you about brown fat, and why it is brown.
We are mammals. And mammals have two main types of fat: white and brown. So brown fat is literally brown. Have you ever met one like this?
Brown fat specializes in heat production. This brown fat is very scarce in adults, but it is abundant in newborns and other small mammals. Every small fry needs it so as not to freeze in the cold.
Newborns cannot shiver from the cold and cannot quickly generate warmth from white fat. Their small body has a small heat capacity, so they need brown fat as an autonomous heater.
If an adult is lucky and has a noticeable amount of brown fat, then he will be able to regulate his weight very well. This can be considered a gift from nature. Such people are much less likely to have any diseases associated with excess fat.
Where to find brown fat
Usually brown fat in an adult is located in the neck, above the collarbones, under the arms, next to the spine and somewhere in the upper abdomen.
In 1981, scientists discovered that people working outdoors have a lot of brown fat in the neck. Then it became clear that brown fat is used as a heater.
Brown fat was also found by positron emission tomography. This method is used in the diagnosis of malignant tumors. It is based on the detection of labeled glucose. The tumor greedily swallows glucose, and the tomograph sees it.
The problem is that brown fat also greedily swallows glucose. On a positron emission tomogram, it may look like a tumor.
It is also scary that tumor metastases are often found in the lymph nodes near the collarbones and next to the spine. For a very long time, brown fat frightened oncologists and their patients in this way. But then we figured it out.
Even brown fat lit up where there is a lot of adrenaline. This was very clearly seen in people with adrenal tumors. It turned out that the fat around the kidneys is very similar to brown fat.
It turns out that brown fat is activated in the cold and under the influence of adrenaline.
How the stove works
Brown adipose tissue does not give its fat to anyone. She burns it inside her own cells. For this, there are many mitochondria in the cells of brown adipose tissue. These are our power plants.
Mitochondria are like little ovens in which fat is burned in oxygen.
Colour
The cells of ordinary white adipose tissue are large and have a drop of fat inside them. There are few mitochondria around this drop. Many of these cells with individual fat droplets are very similar to the fat droplets in milk. Therefore, our white adipose tissue is similar in color to milk.
With brown fat, everything is more complicated. The cells of brown fat themselves are not too large, but the fat in them does not lie in one place, but is rationally packed in separate small drops, which are prepared for the fastest insertion into the oven.
To supply this farm with oxygen and nutrients, many blood vessels are laid in the brown adipose tissue.
It turns out that in a small cell of brown fat, heaps of mitochondria with fat droplets are tightly packed, and outside this case is entangled in red blood vessels.
It is believed that due to blood and a large number of mitochondria, adipose tissue looks brown.
It is clear that we will not see a separate mitochondria, but large clusters of them will be visible as a brown color.
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