ESSENTIAL FATTY ACIDS: FUNCTIONS, IMPORTANCE, NOMENCLATURE, EXAMPLES - BIOLOGY - 2024

The essential fatty acids are those fatty acids without which human beings can not live. They cannot be synthesized by your body and, therefore, must be obtained from food consumed daily.

The concept of "essential fatty acid" was first introduced by Burr and Burr in 1930, referring to linoleic acid (cis, cis -9, 12-octadecadienoic acid). However, a short time later it was also used for linolenic acid (cis, cis, cis -9, 12, 15-octadecatrienoic acid).

Linoleic acid, an essential fatty acid (Source: Jü / CC0, via Wikimedia Commons)

The reason: both fatty acids had the same effects when they were given to experimental rats grown on diets deficient in fat, which had certain abnormalities in their growth and development.

From previous studies, it was generalized that essential fatty acids are usually unsaturated fatty acids belonging to the ω-6 and ω-3 series, which include, respectively, cis-linoleic acid (LA, from English Linoleic Acid) and α-linolenic acid (ALA, from English α-Linolenic Acid).

Essential fatty acids can be used directly by cells or they can act as precursors for other molecules of great importance, such as eicosanoids, for example, which participate in the synthesis of many hormones and in the control of different systemic processes.

It has been shown that the deficiency of these fatty acids contributes many times to the appearance of some cardiovascular diseases, as well as defects in growth and cognitive development.

Functions of essential fatty acids

The different functions of essential fatty acids depend on their participation in the formation of cellular structures, in cellular signaling and / or communication or in other determined "tasks" within the cells of the human body.

- As structural elements

Essential fatty acids are important components of all cell membranes, since they are part of the phospholipids that constitute the lipid bilayers of both the plasma membrane and the internal organelles of all cells.

As part of cell membranes, depending on their degree of saturation, essential fatty acids can alter the fluidity of the membranes and also the behavior of the proteins that associate with them, that is, they regulate the most relevant membrane functions.

- As intracellular messengers

These molecules and their long-chain metabolites have actions as second messengers, since many hormones and growth factors activate an enzyme called phospholipase A that induces the release of these fatty acids from the membranes.

The essential fatty acids that are released by hormonal action are used intracellularly for the synthesis of eicosanoids and other hormones.

- As antibiotic agents

Some essential fatty acids have antibiotic-like activities. Linolenic acid, for example, acts on Staphylococcus aureus cultures, and hydrolyzed flaxseed oil (rich in linoleic and linolenic acid) can inactivate methicillin-resistant members of the S. aureus species.

Linolenic acid promotes the adhesion of Lactobacillus casei to mucosal surfaces and, therefore, favors its growth. This species of bacteria inhibits the growth of other pathogenic bacteria such as Helicobacter pylori, Shigella flexneri, Salmonella typhimurium, Pseudomonas aeruginosa, Clostridium difficile, and Escherichia coli.

- As anti-inflammatory agents

In addition, essential fatty acids can act as endogenous anti-inflammatory molecules, since these and their derivatives suppress the production of some interleukins by T cells (T lymphocytes).

- As substrates for obtaining energy

On the other hand, essential fatty acids, like the rest of the fatty acids that make up cellular lipids, represent a useful source of obtaining large amounts of metabolic energy in the form of ATP through their oxidation.

- As mediators of other activities

They are necessary for the absorption, transport and function of fat-soluble vitamins (vitamins A, D, E, and K).

- As precursors of other molecules

It is important to note that another of the functions of essential fatty acids is that they function as precursors to other fatty acids, which are just as useful for the cells of the human body.

Importance

Essential fatty acids are vitally important to the human body, but they are particularly important for brain, eye, liver, kidney, glandular, and gonadal tissues.

Numerous studies have revealed that essential fatty acids, by themselves, have significant roles in the "pathobiology" of many clinical conditions such as:

- Vascular diseases related to collagen (connective tissue diseases)

- hypertension

- Mellitus diabetes

- Metabolic syndrome X

- Psoriasis

- Eczema

- Atopic dermatitis

- Coronary heart disease

- Arteriosclerosis

- Cancer

In recent years, in addition, it has been shown that the fatty acids of the ω-3 series are essential for the normal development and growth of the human being, and that they work in the prevention and treatment of the aforementioned diseases.

Its importance also lies in the fact that:

- Reduce oxidative stress

- Suppress the production of pro-inflammatory substances and compounds

- Provide cardiovascular protection

- Facilitate the loss of body fat

- They are positively associated with peaks in bone density in young people

Deficiencies in these molecules can decrease mental health, increase the chances of depression, and even trigger aggressive behavior tendencies.

Nomenclature

Essential fatty acids are polyunsaturated fatty acids, that is, they are monocarboxylic acids composed of an aliphatic chain (carbons and hydrogens) in which more than two carbon atoms are linked to each other by means of a double bond (they are not saturated with atoms hydrogen).

These compounds are classified mainly according to the number of carbon atoms they possess, as well as according to the position of the first double bond in relation to the methyl group (-CH3) present at one of the ends of the chain, known as "methyl ω ", or" terminal methyl ".

So, the fatty acids of the "ω-3" or "ω-6" series, for example, are fatty acids of varying lengths that have the first CC double bond at carbon atom number 3 and carbon atom number 6 relative to terminal methyl group, respectively.

Alpha-linolenic acid, an essential fatty acid (Source: Jü / CC0, via Wikimedia Commons)

In addition to these two “families” of polyunsaturated fatty acids, there are two more: ω-7 and ω-9 fatty acids; although these are not considered essential, since the body has the metabolic routes for their synthesis and production.

The fatty acids of the ω-3 series are derived from linolenic acid (18: 3), those of the ω-6 series are derived from cis-linoleic acid (18: 2), those of the ω-7 series are derived from palmitoleic acid (16: 1) and those of the ω-9 series are derived from oleic acid (18: 1).

Metabolism

Thanks to the action of the enzyme ∆6 desaturase (d-6-d), cis-linoleic acid is converted into γ-linoleic acid (18: 3). This new product is elongated to form dihomo γ-linolenic acid (20: 3), which is the precursor of series 1 prostaglandins.

Dihomo γ-linolenic acid can also be converted to arachidonic acid (20: 4) through the action of another enzyme, ∆5 desaturase (d-5-d). This fatty acid is a precursor of series 2 prostaglandins, thromboxanes, and leukotrienes.

- Prostaglandins are hormone-like lipid substances that have many functions in the body: they help to control the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, inflammatory processes, etc.

- Thromboxanes and leukotrienes are eicosanoid lipids that also have hormonal-like activity. They are vasoconstrictors and powerful hypertensive agents, also facilitate the aggregation of platelets during the coagulation process, participate in chronic inflammation processes, among others.

Α-linolenic acid is converted into eicosapentaenoic acid (20: 5) by the action of the same enzymes that act on cis-linoleic acid (d-6-d and d-5-d). This acid participates in the formation of the precursor of series 3 prostaglandins and series 5 leukotrienes.

Examples of essential fatty acids

The most representative examples of essential fatty acids are the two that have been mentioned repeatedly throughout the text:

• Linoleic acid, a fatty acid from the omega-6 series.
• Linolenic acid, a fatty acid from the omega-3 series.

Linoleic acid is a fatty acid that has two unsaturations in cis configuration. It has 18 carbon atoms and, as can be understood from the series to which it belongs, it has the first double bond at the sixth carbon atom with respect to the terminal methyl group of the molecule.

Linolenic acid, on the other hand, is a fatty acid with three unsaturations, also with 18 carbon atoms, but belonging to the omega-3 series, which is understood to have the first of the three double bonds on the carbon in position 3 to the terminal methyl.

Foods with essential fatty acids

In both Europe and North America, the average amount of essential fatty acids consumed in the diet daily is around 7 and 15 g, and the main dietary sources of these fatty acids, depending on their type, are:

Acid

Cereals, eggs, meats and most oils of vegetable origin. Whole grain breads made with "whole grains", margarine, and most baked goods. Sunflower, corn and rice oils are also rich in cis-linoleic acid.

Α-linolenic acid (ALA)

Canola, flax, and linseed oil, as well as walnuts and green leafy vegetables are rich in α-linolenic acid.

Similarly, breast milk is rich in this essential fatty acid, which newborns feed on during the lactation period.

Fish and fish oil are rich in eicosapentaenoic acid and docosahexaenoic acid, derived from linolenic acid.

Image by Christine Sponchia at www.pixabay.com

It is important to mention that many foods (both of animal and vegetable origin) are also rich in the metabolic intermediates of the two essential fatty acids described above. These include:

- Eicosapentaenoic acid

- Docosahexaenoic acid

- Gamma linoleic acid

- Dihomo gamma linoleic acid

- Arachidonic acid

References

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