Fatty-acid

History

1769 : discovered Cholesterol in gallstones by François Poulletier of the Room;
1804 : Nicolas Theodore de Saussure carries out an experiment showing that oxygen can condense with the linseed oil. This is a first step towards the discovery of the unsaturated fatty-acids;
1813 : Eugene Chevreul describes the concept of Fatty-acid.
1818 : Eugene Chevreul names “cholestérine” the lipid discovered by Poulletier of the Room;
1823 : Eugene Chevreul publishes his “chemical Research on the greasy substances of animal origin” where it describes for the first time of many fatty-acids of which butyric acids, caproic, stearic and oleic;
1827 : William Prout is the first to recognize the grease S like an important nutrient in the food, as well as the Protéine S or the Sucre S;
1847 : Nicolas Theodore Gobley isolates the Lécithine from the egg yolk. It is in fact the discoverer of the Phospholipide S;
1869 : Hippolyte Mège-Mouriès invents the Margarine after Napoleon III launched a contest in order to find a substitute with the Beurre;
1903 : Wilhelm Normann deposits a patent for the “conversion of the unsaturated fatty-acids or their glycérides into compounds saturated” by a hydrogenizing process;
1909 : discovered acid arachidonic by Percival Hartley;
1913 : McCollum and Davis show the need for certain lipids in the food at the time of the growth;
1930 : George and Mildred Burr discover that certain polyinsaturé fatty-acid are essential;
1957 : Keys, Anderson and Grande show a relation between the blood cholesterol level and the food catch of grease;
1964 : Konrad Bloch and Feodor Lynen receives the Nobel Prize of medicine for “their discovery concerant the mechanism of regulation of the metabolisms of the Cholestérol and the fatty-acids”;
1972 : Bang and Dyerberg show that the Eskimo S of Greenland have a low rate of Cholestérol, of LDL and of Triglycéride S in blood east correlates at the low risk of Myocardial infarction, in comparison with the Danish population;
1982 : Sune K. Bergström, Bengt I. Samuelsson and John R. Vane receive the Nobel Prize of medicine for “their discovery concerant the associated Prostaglandine S and biologically active substances”;
1985 : Michael S. Brown and Joseph L. Goldstein receive the Nobel Prize of medicine for “their discovery relating to the regulation of the metabolism of cholesterol”.

Saturated fatty-acids

Unsaturated fatty-acids

Role of the fatty-acids

metabolic Role : the fatty-acids are an important energy source for the organization. They are stored in the form of Triglycéride S in the fat Tissus. At the time of an effort, in particular at the time of an effort of long life, the organization will draw from these stocks and will degrade the fatty-acids in order to produce energy in the form of ATP
structural Rôle : the fatty-acids are used for the synthesis of other lipids, in particular the Phospholipide S which form the membranes around the cells and of the Organite S. the composition in fatty-acids of these phospholipides give to the membranes physical properties (elasticity, Viscosité) particular
Rôle of messenger : the fatty-acids are the precursors of several messenger intra- and extracellular. For example, the arachidonic Acide is the precursor of the Eïcosanoïde S, Hormone S intervening in the Inflammation, the blood Coagulation, etc .
Other roles: the fatty-acids are stored in the form of triglycerides in the bumps of the Chameau and Dromadaire. Their degradation brings to the formation of water. In this manner, the fatty-acids constitute a water reserve for these animals.

Metabolism of the fatty-acids

The metabolism of the fatty-acids includes/understands two components:

the Lipogenesis , or synthesis of novo which consists in synthesizing an fatty-acid by condensation of acetic molecule of Acid (or unit acétyl) with two carbons by consuming energy in the form of Adénosine triphosphate (ATP). It should be noted that the units acétyl are in the form of Acétyl-coenzymeA (acétyl-CoA). ;
the Lipolysis , or β oxidation, which consists in degrading fatty-acids in units acétyl by producing energy in the form of ATP.

Lipogenesis

The lipogenesis allows the synthesis of fatty-acid saturated by condensation with molecules with Acétate 2 carbons. in the mammals This process takes place in the Cytoplasme cells, pricipalement of the Foie, fat fabrics and glands mammaires. However, it does not make it possible to synthesize fatty-acids saturated with more than 16 carbons (palmitic acid) or unsaturated fatty-acids. The whole of the synthesis is carried out on the level of an multi-enzymatic complex called fatty-acid synthase . The palimitic summary balance of the acid is:

8 acétyl-CoA + 7×ATP + 14 (NADPH + H⁺) → palmitic acid (C16: 0) + 8 CoA + 7 (ADP + pi) + 14NADP⁺ + 6

This synthesis is consuming energy in the form of ATP and requires as cofactor of the Coenzyme has (CoA) and of the Nicotinamide Adénine Dinucléotide Posphate (NADP). CoenzymeA makes it possible to facilitate the use of acetate by the cell. The acétyl-CoA comes mainly from the Mitochondrie where it is synthesized starting from the Pyruvate at the time of the Cycle of Krebs. The NAPD is the reducing agent of the synthesis of the fatty-acids. In fact, it is oxidized at the end of the reaction and must be regenerated.

The elongation of the fatty-acids saturated beyond 16 carbons is carried out in the endoplasmic Réticulum and the Mitochondrie. In the first case, the elongation implies fatty-acid élongases . In the second case, the elongation implies paradoxically certain enzymes of the lipolysis.

The synthesis of the unsaturated fatty-acids starting from the saturated fatty-acids takes place on the levels of the membrane of the endoplasmic reticulum by fatty-acid désaturases . The desaturation is consuming molecular oxygen () and uses as cofactor of the Nicotinamide Adénine Dinucléotide (NAD):

stearic acid + 2 (NADH + H⁺) + → acid oleic + NAD⁺ + 2

It should be noted that all the organizations do not synthesize all the possible saturated and unsaturated fatty-acids inevitably. For example, the man cannot synthesize the Linoleic acid . This fatty-acid is known as essential and must be brought by the food.

Fatty-acids, nutrition and cardiovascular diseases

The food is an important source of fatty-acids. This contribution is vital to maintain a stable Lipidémie and to provide to the body the essential fatty-acids. The qualified fatty-acids of essential include the Omega-3 and Omega-6. The human body not knowing to synthesize them, or synthesizing them in insufficient quantity, a minimal and regular contribution by the food is necessary.

On the other hand, of many studies showed that an excess of fatty-acids (in particular saturated and unsaturated trans ) could have consequences on health and in particular increase in a very significant way the cardiovascular risks of problems. Certain studies carry on the excessive consumption of unsaturated fatty-acids trans resulting from industrial processes like hydrogenation partial of fatty-acids of vegetable origin (oils).

In an opinion published in 1992, American Heart Association (AHA) made the following recommendations:

the daily energy contribution coming from the fat contents should not exceed 30% of the daily Apport recommended;
these fat contents should contain

of 50% of fatty-acid monoinsaturés of type omega-9
of 25% of fatty-acid polyinsaturés of type omega-3 and omega-6
of 25% of saturated fatty-acids;

part of the saturated fatty-acids can be replaced by fatty-acids mono-unsaturates

Nb: For the analyzes realized within the framework of the repression of the frauds, one determines the origin of the fat contents according to the profile in fatty-acids, and sterols (insaponifiables). It should be known that for the plants, the fatty-acids with odd carbonaceous chain do not exist.

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