Omega-3 polyunsaturated fatty acids

The synthesis of omega-3 polyunsaturated fatty acids

Within omega-3 (ω-3) polyunsaturated fatty acid family:

are important fatty acids.

Omega-3 polyunsaturated fatty acids and α-linolenic acid

Omega-3 Polyunsaturated Fatty Acids: Omega-3 Fatty Acid Metabolism
Fig. 1 – Omega-3 Fatty Acid Metabolism

Like linoleic acid (omega-6 fatty acid), alpha-linolenic acid or ALA is a primary product of plant polyunsaturated fatty acid or PUFA synthesis and is the precursor of all the omega-3 polyunsaturated fatty acids.
It is produced de novo from linoleic acid only by plants (by the chloroplasts of marine phytoplankton and land plants) in a reaction catalyzed by Δ15-desaturase, i.e. the enzyme that forms the omega-3 polyunsaturated fatty acid family from omega-6 one catalyzing the insertion of the double bond between carbon atoms 3 and 4, numbered from methyl end of the molecule.
Note: while many land plants lack the ability to synthesize omega-3 polyunsaturated fatty acids, aquatic ones and planktons in colder water produce abundant amounts of them.
Animals, lacking Δ15-desaturase, can’t synthesize alpha-linolenic acid, and all the omega-3 polyunsaturated fatty acid family de novo, and they are obliged to obtain it from plant foodstuff and/or from animals that eat them; for this reason omega-3 polyunsaturated fatty acids are considered essential fatty acids, so called EFA.

Omega-3 polyunsaturated fatty acids: from α-linolenic acid to EPA and DHA

Omega-3 Polyunsaturated Fatty Acids: Foods Rich in Omega-3 Fatty Acids
Fig. 2 – Foods Rich in Omega-3 Fatty Acids

Animals are able to elongate and desaturase dietary alpha-linolenic acid in a cascade of reactions to form very long polyunsaturated omega-3 fatty acids but terrestrial animals have limited ability to do it. The efficiency of synthesis decreases down the cascade: conversion of alpha-linolenic acid to EPA is limited (the activity of Δ6-desaturase is the rate limiting in humans) and to DHA is even more restricted than that of EPA. This metabolic pathway occurs mainly in the liver and cerebral microvasculature of the blood brain barrier, but also in the cerebral endothelium and astrocytes.

Fish and shellfish, unlike terrestrial animals, are able to convert efficiently alpha-linolenic acid, obtained from chloroplast of marine phytoplankton, in EPA and DHA (the last one is present in high concentration in many fish oils but pay attention: many fish oils are also rich in saturated fatty acids).
It should be noted that polyunsaturated fatty acids of the ω-3 family, and of any other n-families, can be interconverted by enzymatic processed only within the same family, not among families.

EPA and DHA are primarily found in marine algae (in genetically engineered algae DHA represents approximately 50% of the total fatty acids), fish, shellfish, and marine products (particularly oil from cold-water marine fish).

Some functions of omega-3 polyunsaturated fatty acids

  • Omega-3 polyunsaturated fatty acid are capable of increasing high-density lipoprotein (HDL), “good cholesterol”, and of interleukin-2 levels. On the other hand, they decrease the levels of low-density lipoprotein (LDL), “bad cholesterol“, and very low density lipoprotein cholesterol (VLDL) and of interleukin-1 levels.
  • They are essential for the normal functioning of the brain and retina, especially in premature borns.
  • They are essential for growth and development throughout the life; for example if in children diet there is not enough omega-3 polyunsaturated fatty acids they may suffer dermatitis, growth retardation, neurological and visual disturbances.
  • C-20 polyunsaturated fatty acids, belonging to omega-3 and also omega-6 polyunsaturated fatty acid families, are the precursors eicosanoids (prostaglandins, prostacyclin, thromboxanes, and leukotrienes), potent, short-acting, local hormones.
  • While the omission in the diet of omega-6 polyunsaturated fatty acids results in a manifest systemic dysfunction, the deprivation of omega-3 polyunsaturated fatty acids causes dysfunction in a wide range of behavioral and physiological modalities.
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Rosenthal M.D., Glew R.H. Mediacal biochemistry. Human metabolism in health and disease. John Wiley & Sons, Inc. 2009

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Published by Dr. Nicola Tazzini

Nicola Tazzini, MS in Biology Sciences Doctor Tazzini graduated "Summa cum Laude" at the University of Pisa on Nov. 11th, 1996 after 1½ year, carried out in the laboratory of Biochemistry of the Department of Biochemistry and Physiology of the Faculty of Natural, Physical and Mathematical Sciences. The subject of his thesis was "Studies about the mechanism of cytotoxicity of the combination of deoxyadenosine and deoxycoformicine on a cell line derived from a human colon carcinoma" (see References). He registered as a Biologist at the University of Pisa on May 10th, 1998. He specialized "Summa cum Laude" in "Biochemistry and Clinical Chemistry" in Oct. 30th, 2001 at the Department of Biological Chemistry of the Faculty of Medicine and Surgery of the University of Parma. The subject of his thesis was: "Analyses of ematochemical, enzymatic and non-enzymatic parameters with antioxidant activity in young professional athletes". He has started his activity of Nutritionist on Feb. 02nd, 2002. He attended the following courses related to the activity of Nutritionist. 2000 1. Pasta in human nutrition. Associazione Biologi Nutrizionisti Italiani. 2. Course of forming and updating in nutrition and health: roll of Biologist. Associazione Scientifica Biologi Pisa. 2001 1. Elements of nutrition. Associazione Scientifica Biologi Pisa. 2002 1. Nutrition as healthy factors, professional update. Associazione Biologi Nutrizionisti Italiani. 2003 1. Nutrition as healthy factors- first part. Associazione Biologi Nutrizionisti Italiani. 2004 1. Nutrition as healthy factors- second part. Associazione Biologi Nutrizionisti Italiani. 2. Nutrition in childhood. Associazione Biologi Nutrizionisti Italiani. 3. Sport activity, growth and correct nutrition. Associazione Biologi Nutrizionisti Italiani. 4. Nutrition and tumor. PLANNING congressi Srl. 2005 1. Doping: guidelines and diagnostic assessments: legal, biochemical, medical and toxicological aspects. Restless Architech of Human Possibilities S.a.s. 2. Nutrition in the third age: nutritional issues and proper nutritional habits. Associazione Biologi Nutrizionisti Italiani. 3. Technical legislation evolution and ethics in development of the profession. Ordine Nazionale dei Biologi. 2006 1. Sport and nutrition. Syntonie S.r.l. 2. Nutrition and prevention: choose to stay healthy. Ordine Nazionale dei Biologi. 3. Pathology nutrition and legislation aspects. Syntonie S.r.l. 4. Nutrition: guidelines. Ordine Nazionale dei Biologi. 2007 1. Nutrition topics: food as welfare tool: physiological and pathological balance factors. Ordine Nazionale dei Biologi. 2008 1. Outdoor and indoor environment. Resources and balances. Ordine Nazionale dei Biologi. 2. Biologist ’profession in the current technical legislation evolution. Ordine Nazionale dei Biologi. 3. Prevention of childhood obesity: nutritional strategies from pregnancy to school age. Ordine Nazionale dei Biologi. 2009 1. Nutrition, the cornerstone. Nutritional and health needs in the era of the genome. S.I.N.U. 2010 1. The evolution of food safety. Ordine Nazionale dei Biologi. 2. Food safety and correct nutrition. Associazione Scientifica Biologi Pisa and Ordine Nazionale dei Biologi. 2011 1. Role of coffee in physiological and pathological states. CMGRP Italia S.p.A. Reference 1. Bemi V., Tazzini N., Banditelli S., Giorgelli F., Pesi R., Turchi G., Mattana A., Sgarrella F., Tozzi M.G., Camici M. Deoxyadenosine metabolism in a human colon-carcinoma cell line (LoVo) in relation to its cytotoxic effect in combination with deoxycoformycin. Int J Cancer 1998;75(5):713-20. doi:https://doi.org/10.1002/(SICI)1097-0215(19980302)75:53.0.CO;2-1 2. Cassandra Studio . Nutraceuti e cibi funzionali. Youcanprint, 2015 3. Singh A.N., Baruah M.M. & Sharma N. Structure based docking studies towards exploring potential anti-androgen activity of selected phytochemicals against prostate cancer. Sci Rep 2017;7(1):1955. doi:10.1038/s41598-017-02023-5 4. Wee T.T., Lun K.R. Teaching science in culturally relevant ways: ideas from Singapore teachers. World Scientific, 2014

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