Alpha Linolenic Acid and Linoleic Acid Metabolism


Linoleic acid is a member of essential fatty acids called omega-6 fatty acids. It is an essential dietary requirement for all mammals. The other group of essential fatty acids is the omega-3 fatty acids (i.e. alpha-linolenic acid). The first step in the metabolism of linoleic acid (LA) is performed by Δ-6-desaturase, which converts LA into gamma-linolenic acid (GLA). GLA is converted to dihomo-gamma-linolenic acid (DGLA), which in turn is converted to arachidonic acid (AA). One of the possible fates of AA is to be transformed into a group of metabolites called eicosanoids. There are three types of eicosanoids are prostaglandins, thromboxanes, and leukotrienes.

α-Linolenic acid (ALA), is an essential 18:3n or omega-3 fatty acid. It is considered essential because it cannot be produced entirely within the body and must be acquired through diet. Once acquired, α-Linolenic acid can be “regenerated” endogenously by the cleavage of phospholipids into their constituent fatty acids by phospholipase A2. The resulting fatty acid can then be converted to stearidonic acid through the action of fatty acid desaturase 2. α-Linolenic acid is primarily used by the body in the synthesis of Eicosapentaenoic acid (EPA; 20:5, n−3) and docosahexaenoic acid (DHA; 22:6, n−3), two fatty acids that play a vital role in many metabolic and cell signaling processes. These fatty acids are synthesized via fatty acid desaturase 2, fatty acid desaturase 1 and several elongase enzymes (Q9GZR5) in the liver. α-Linolenic acid is also in the regulation of lipid metabolism by activation of the peroxisome proliferators-activated receptor alpha (PPARa).

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References

  1. Lehninger, A.L. (2005) Lehninger principles of biochemistry (4 th ed.). New York: W.H Freeman.
  2. Salway, J.G. (2004) Metabolism at a glance (3 rd ed.). Alden, Mass. : Blackwell Pub.
  3. Vance, D.E., and Vance, J.E. (2008) Biochemistry of lipids, lipoproteins, and membranes (5 th ed.) Amsterdam ; Boston : Elsevier.