Adrenoreceptors

What are adrenoreceptors?

Adrenoreceptors are organic receptors that couple to catecholamines. They work in different functions of the sympathetic nervous system.

These receptors can be found in many cells throughout the human body. Upon contact with catecholamines, stimulation of the nervous system occurs.

There are two types of adrenergic receptors in the body, each of which consists of subtypes.

Alpha-adrenergic receptors

• Alpha 1 receptors: this type of adrenergic receptors are activated by the hormone adrenaline and the neurotransmitter noradrenaline, released by the nervous system. When alpha 1 receptors are activated, they produce various effects in the body. These adrenergics are found in tissues of the prostate, urinary tract, intestine and in the piloerector muscles and smooth muscles of blood vessels. Several studies have also associated them with various diseases.
• Alpha 2 receptors: this type of receptor is located in the central nervous system and in the tissues of the pancreas, adipose cells and smooth muscles of blood vessels. They are activated by the release of the hormone adrenaline and the neurotransmitter noradrenaline in the sympathetic nervous system. They are involved in decreasing sympathetic nervous activity, reducing the heart rate and relaxing the smooth muscles of the blood vessels, resulting in dilation of the blood vessels. And they are related to appetite regulation, insulin release and cognitive function.

Beta-adrenergic receptors

• Beta 1 receptors: found in different tissues of the human body, in the heart, kidneys and fat cells. They cause an increase in heart rate, stimulation of renin release by the kidneys and release of fatty acids from adipose cells. They participate in the regulation of the cardiovascular system.
• Beta 2 receptors: these adrenergic receptors are located in body tissues, in the smooth muscles of the bronchi, blood vessels and gastrointestinal tract, in the cells of the salivary and sweat glands. They cause relaxation of the smooth muscles of the bronchi (bronchodilation), dilation of the blood vessels and relaxation of the gastrointestinal tract.
• Beta 3 receptors: this type of beta receptor is found in the fat cells of the human body and also in tissues of the urinary tract, liver and heart muscle. They are involved in stimulating thermogenesis and decreasing lipogenesis.

How adrenoreceptors work

These receptors become active when activated by catecholamines, which include adrenaline, dopamine, cortisol, noradrenaline and epinephrine.

How do they influence fat accumulation?

Adrenergic receptors located in adipocytes can be of several types, but the main ones are beta-2 and alpha-2.

In a standard adipocyte, we would have an equal amount of alpha 2 and beta 2 receptors. However, there are adipocytes with more receptors of one type than another, making fat loss sequential.

When catecholamines bind to the beta-2 receptor, they activate lipolysis. When beta-2 receptors are activated, triglycerides stored in fat cells are broken down.

In this way, the glycerol molecule is released, fatty acids are released into the bloodstream, these are used as a source of energy and fat oxidation increases.

Whereas, when they bind to alpha-2 receptors, they activate lipogenesis.

The areas of the body where we accumulate the most fat are those where there is the highest concentration of alpha-2 receptors. That is why it is so difficult to eliminate this fat, although it is possible with caloric deficit, high intensity exercise and the use of substances that activate organic lipolysis.

Catecholamines

Lipolysis

Fat