Everywhere we read that body fat, where body fat usually means white fat, where beige and brown fat have different functions, is sensitive to the action of insulin. And therefore insulin is a “fattening” hormone.
But a new and revolutionary discovery by a group of Swedish scientists, who have managed to “map” white fat cells, called white adipocytes, with a special technology, could reverse what we knew about the role of insulin in the formation of fat. bodily.

INSULIN AND BODY FAT: THE REVOLUTIONARY DISCOVERY

Researchers from the Karolinska Institutet mapped white adipose tissue for the first time thanks to a tissue-specific spatial transcriptome analysis. In essence, they used a new “space” technology to analyze the mRNA of white adipocytes and thus discover the identity and organization of individual cells.
Until now, in fact, the study of white fat was of the vascular type, but there has never been a study that was able to identify the different classes of cells and their spatial architecture. And above all, understand what activates them and study their behavior.
However, this study indirectly dispels a very important myth, namely that of the role of insulin in the formation of body fat and its responsibility in obesity.

We often read, even from doctors, that insulin is a kind of bad hormone, responsible for obesity and other diseases. Insulin is a hypoglycemic hormone whose main purpose is to feed glucose and amino acids to cells that are sensitive to its action. It used to be said to be employees . Among these cells there are also those of adipose tissue.
Hence, the harmful simplification of saying that insulin is a fattening hormone.

But this mapping by Swedish researchers reveals that, as usual, things are much more complex than that.
Let’s try to understand why.

BODY FAT: ORDERED ORGANIZATION VS DISORDER

Fat cells are plastic. What does it mean? It means that they shrink or expand depending on whether they free or incorporate material. They can also grow to double.
When white fat cells expand, they do so by organizing in two ways. Either they organize themselves in an orderly way, for example through hyperplasia, or they organize themselves in a disordered way, becoming hypertrophic and becoming inflamed. Only this disorganization is linked to an immune dysfunctional tissue, and to an increased risk of diabetes, insulin resistance and cardiovascular disease. Therefore, white adipose tissue is not harmful in itself, it is only harmful in the second case.

BODY FAT: HETEROGENEITY = SENSITIVITY TO INSULIN

The researchers succeeded in creating an atlas of human fat cells for the first time. There are twenty classes of them. The more heterogeneous the adipose tissue, the more sensitive we are to the action of insulin. To understand, the opposite of insulin sensitivity is insulin resistance.

BODY FAT: ONLY ONE CLASS OF CELLS ARE ACTIVATED WITH INSULIN

Of these twenty classes, only three classes are represented by genetically distinct mature cells. They have given the names of Adipo ^LEP , Adipo ^PLIN and Adipo ^SAA . The first is sensitive to leptin, the second and third regulate the metabolism of glucose and fat, although the third has more adipokines and is enzymatically more complex while the second is characterized by smaller cells in diameter. The first class is the most abundant.
This composition changes between subjects, and it is the organization of these cells and in what percentage they are that differentiates a thin subject from an obese one.
Obese subjects have less PLIN ^Adipus than lean subjects. But they have more Adipo ^LEP.
We have seen that the former are the smallest.
All these cells are plastic, but the risk of obesity is not related to the size of the cells, but to their organization and proportionate quantity.
Different individuals will have different fat cells and that this distinction is primarily genetic.
We do not have the same type of fat in common.

• But the most interesting discovery is another.

  That only the PLIN ^Adipo cells , which we have seen to be in a lower percentage in the obese, are those that are really sensitive to insulin both in relation to body fat and in relation to the whole body, whereas the third class is to a lesser extent. That is, it is from these that we understand how sensitive a subject is or not to insulin, both in the formation or reduction of body fat and in general.

• This also means that if you get fat, the fault is not solely and exclusively insulin.

  The relationship between insulin and body fat is not that unique.