The different fat tissues and their properties: an overview

Along with that, brown fat tissue plays an important role for humans, especially new-borns and infants. Due to their low muscle mass, new-borns and infants are only able to generate a certain quantity of heat by muscle shivering, and at the same time, they cool more quickly due to their relatively large surface area. The brown fat tissue serves as a type of “heating“ to maintain their body temperature. It can transform stored energy into heat through the oxidation of fatty acids. At the start of life, the proportion of brown fat tissue is between 2 % and 5 % of the body weight. It does however continuously decrease so that in adulthood it only occurs in rudimentary form. Brown fat tissue occurs not only in humans, but also in other animals and is vital for the survival of hibernating animals.

Despite its physiological functions, an excess of body fat can lead to illness. It appears that for metabolic health, it is less the absolute mass of fat and rather its distribution that has a vital role. It is assumed that the subcutaneous fat tissue is a predominantly passive energy store that only contributes minimally to the occurrence of illnesses. The quantity of visceral fat tissue located in the body’s core is of more significance. It is metabolically active and secretes many messenger substances which affect many processes. A higher proportion of visceral fat tissue has come to be understood as a risk factor in its own right for the occurrence of Type 2 diabetes and cardiovascular diseases.

Health is affected not only by the location but also by the composition of fat tissue. It is assumed that many small fat cells are more beneficial than a small number of larger ones. If there is an increase in weight, the fat cells reach their limit at a certain point and start to pass the stored lipids into the blood. These can then move into the liver and musculature, which increases the risk of weight-associated comorbidities.

As mature fat cells lose the ability to split, it was believed for a long time that their number was pre-determined in childhood and youth, and stays more or less constant over a lifetime. However, we now know that there are precursor cells in the fat tissue that can transform into fat cells at any age.

A new type of fat tissue has only recently been discovered by researchers from Zurich ETH. In experiments on mice and human fat tissue, they discovered a previously unknown fat cell type, which they named “Areg” (adipogenesis regulatory cell). These cells send signals to surrounding fat cells and appear to have a regulatory effect on the formation of new fat cells. More specifically, they prevent the precursor cells from maturing into fat cells. According to this, it can be assumed that the activity of the “Aregs” influence the number of fat cells and thus the build-up of the fat stores.

Accordingly, the researchers were able to prove that overweight mice, whose fat tissues consisted predominantly of few large fat cells, have a high number of “Aregs”. Furthermore, they showed with more detailed experiments that the precursor cells turned into new mature fat cells, with the removal of the “Aregs”, thus increasing their overall number.

This discovery represents a milestone in the understanding of fat tissues and could be used for treatments in future. Through the targeted influencing of “Aregs”, an increased maturity of fat cells is possible. These new storage capacities would prevent the lipid releases of over-filled fat cells and counter the deposition in the liver and musculature. A reduction in the fatty degeneration of organs can in turn prevent the complications of overweight and obesity.

Until then, a healthy diet and sustained reduction in weight remain the most effective means against metabolic and heart-circulatory illnesses.

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