Adiponectin is a hormone synthesized mainly in fatty tissue, although other cell types can also produce it. It intervenes in the metabolism of lipids and carbohydrates and has an anti-inflammatory and cardioprotective function.
Adipose tissue, or fatty tissue, is the main storehouse of lipids, which are stored primarily in the form of triglycerides. There are two types of adipose tissue:
- Adipose tissue brown or brown (brown fat), present in all mammalian species. It is fundamental for thermogenesis, that is, the production of heat. This type of fat is particularly abundant in animal species that hibernate.
- White adipose tissue or white fat, which is what concerns us.
Until a few years ago it was believed that it was a mere energy store. However, the functions that are at their charge are increasingly known. Besides of important role that has in the energy metabolism, intervenes in the sensations of hunger and satiety.
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Biochemistry of adiponectin
It's a 30 KDa molecule, structurally similar to the tumor necrosis factor alpha. It circulates in plasma either in the form of a dimer (two units similar to a clothespin), or in the form of a high molecular weight complex.
The normal plasma concentration of adiponectin is between 5 and 10 picograms / mL. In addition, these Blood levels of adiponectin are inversely proportional to the BMI.
There are two types of receptors for adiponectin. The first of them, AdipoR1, has a ubiquitous distribution, being found in greater concentration in skeletal muscle. The other, called AdipoR2, is preferably located in the liver .
Adiponectin it acts both directly, and indirectly in the metabolism of insulin . On the one hand, it affects the metabolism of fatty acids, linked in turn to that of insulin. On the other hand, it drives the cascade of intracellular reactions associated with the activation of insulin receptors.
The insulin sensitivity , that is, the capacity of the tissues to capture insulin is diminished when plasma levels of triglycerides are high. Therefore, the ability of muscle tissue to take advantage of glucose and obtain energy decreases. Nevertheless, Adiponectin acts by increasing the use of fatty acids in muscle fibers. In this way, it favors the recruitment and oxidation of these to obtain energy.
As they are used as an energy source, the triglycerides accumulated in the muscle fibers decrease. This reduction then favors the expression of molecules capable of capturing insulin. Adiponectin also has a direct function on insulin. Potentiates both the activity of its receptor and the intracellular pathway associated with it , through a process called phosphorylation .
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Effects of adiponectin on blood vessels
Adiponectin It exerts an anti-inflammatory and protective role in the cardiovascular system. First, it slows the inflammatory response that occurs in blood vessels when they are damaged mechanically. And, secondly, it intervenes in all the necessary steps for the formation of a plate of atheroma .
- Inhibits the expression of adhesion molecules.
- It prevents adhesion and activation of monocytes.
- Avoid the formation of foam cells , the key cells in the atheroma plaque.
- It blocks the migration of smooth muscle fibers to the vessels.
High levels of adiponectin are associated with a lower risk of suffering a myocardial infarction . It is likely that this is due to the protective effect of the hormone on the coronary arteries.
- Domínguez Reyes CA Adiponectin: Adipose tissue beyond the inert reserve of energy. Journal of Endocrinology and Nutrition. 2007 Vol 15. N3. P 149-155
- Elissondo N, Gómez Rosso L, Maidana P, Brites F. Adiponectin: an adipocytokine with multiple protective functions. Biochemical record Clin. Latinoam. 2008. Vol 42. N1.