Omega-7 fatty acid

Omega-7 fatty acids are a class of unsaturated fatty acids in which the site of unsaturation is seven carbon atoms from the end of the carbon chain. The two most common omega-7 fatty acids in nature are palmitoleic acid and vaccenic acid.[1] They are widely used in cosmetics due to their moisturizing properties.  Diets rich in omega-7 fatty acids have been shown to have beneficial health effects, such as increasing levels of HDL cholesterol and lowering levels of LDL cholesterol.

Types of fats in food
See also

Rich sources include macadamia nut oil, and sea buckthorn oil(berries) in the form of palmitoleic acid, while dairy products are the primary sources of vaccenic acid and rumenic acid.[2] A lesser but useful source of palmitoleic acid is avocado fruit (25,000ppm).[3]

The monounsaturated omega-7 fatty acids have the general chemical structure CH3-(CH2)5-CH=CH-(CH2)n-CO2H.

Common name Lipid name Chemical name
none 12:1 (n−7) 5-Dodecenoic acid
none 14:1 (n−7) 7-Tetradecenoic acid
Palmitoleic acid 16:1 (n−7) 9-Hexadecenoic acid
Vaccenic acid 18:1 (n−7) 11-Octadecenoic acid
Rumenic acid 18:2 (n−7) Octadeca-9,11-dienoic acid
Paullinic acid 20:1 (n−7) 13-Eicosenoic acid
none 22:1 (n−7) 15-Docosenoic acid
none 24:1 (n−7) 17-Tetracosenoic acid

Metabolism

16- and 18-carbon omega-7 unsaturated fatty acids are known to be converted into 18- or 20-carbon highly unsaturated fatty acids in the body by nonselective desaturating enzymes.[4]  The same enzymes also act on omega-3, omega-6, and omega-9 fatty acids.  As a result, while proportions of individual highly unsaturated fatty acids may vary greatly in different tissue types due to factors such as diet, the overall concentration of highly unsaturated fatty acids is kept stable in a living organism.  These individual concentrations are highly influential in determining what fatty acids will be used by a given tissue type in phospholipid synthesis such as that required for the maintenance of the cellular membrane.[4]

Research

Diabetes

Omega-7 fatty acids, especially palmitoleic acid, have been shown in vitro to decrease glucose-sensitive apoptosis in beta cells in the pancreas, a condition associated with diabetes.[5][6]  In adult organisms, new beta cells are most commonly the result of replication rather than from direct stem cell differentiation, meaning that preventing apoptosis of beta cells is crucial for maintaining a stable population of beta cells.  The cytoprotective effect of omega-7 fatty acids makes them a candidate for diabetes treatment.[5]  Omega-7 fatty acids have also been found to improve insulin sensitivity, and a diet rich in omega-7 fatty acids is correlated with a greatly decreased incidence of diabetes.[7]

Cholesterol

In an animal study, dietary omega-7 fatty acids were found to result in an increase in HDL cholesterol in comparison to a diet rich in coconut or canola oils.[8]

Production

In cows

Dairy products are one of the primary sources of dietary omega-7 fatty acids.  However, the production of omega-7 fatty acids in cows is heavily diet-dependent.[9]  Specifically, a reduction in the proportion of herbage consumed by a cow is correlated with a significant decrease in the omega-7 fatty acid content of the cow’s milk. Rumenic and vaccenic acid concentrations declined significantly within one week of removing herbage from the cow’s diet, suggesting that modern dairy farming methods may lead to decreases in beneficial fatty acid content of dairy products.[9]

Algal extraction

Traditional sources of omega-7 fatty acids such as macadamia nuts have proved expensive on the industrial scale, prompting the discovery of new omega-7 rich sources such as algae.  Alterations to algal growing conditions such as carbon dioxide or dipotassium phosphate enrichment have been shown to potential bias algal biosynthesis towards lipids.[10]  Up to 90% of their dry weight may be harvested as lipids. In this process, raw algae is dewatered to yield algal oil.  Algal oil gets degummed, typically via washing with acid, to removing polar lipids and metals.  Degummed algal oil is then transesterified and purified to yield a mixture of omega-7 esters and eicosapentaenoic acids, which can be hydrodeoxygenated to form algae jet fuel and algae green diesel, respectively. These products are then crystallized and separated to yield the desired omega-7 fatty acid.

See also

References
  1. Mukherjee KD, Kiewitt I (October 1980). "Formation of (n-9) and (n-7) cis-monounsaturated fatty acids in seeds of higher plants". Planta. 149 (5): 461–3. doi:10.1007/BF00385748. PMID 24306473. S2CID 22892828.
  2. Destaillats F, Buyukpamukcu E, Golay PA, Dionisi F, Giuffrida F (February 2005). "Vaccenic and rumenic acids, a distinct feature of ruminant fats". Journal of Dairy Science. 88 (2): 449. doi:10.3168/jds.S0022-0302(05)72705-3. PMID 15653508.
  3. Duke, James A. (1992). Handbook of phytochemical constituents of GRAS herbs and other economic plants. Boca Raton, Florida.: CRC Press.
  4. Lands WE (May 1992). "Biochemistry and physiology of n-3 fatty acids". FASEB Journal. 6 (8): 2530–6. doi:10.1096/fasebj.6.8.1592205. PMID 1592205. S2CID 24182617.
  5. Morgan NG, Dhayal S (April 2010). "Unsaturated fatty acids as cytoprotective agents in the pancreatic beta-cell". Prostaglandins, Leukotrienes, and Essential Fatty Acids. 82 (4–6): 231–6. doi:10.1016/j.plefa.2010.02.018. PMID 20206490.
  6. Acosta-Montaño P, García-González V (March 2018). "Effects of Dietary Fatty Acids in Pancreatic Beta Cell Metabolism, Implications in Homeostasis". Nutrients. 10 (4): 393. doi:10.3390/nu10040393. PMC 5946178. PMID 29565831.
  7. Mozaffarian D, Cao H, King IB, Lemaitre RN, Song X, Siscovick DS, Hotamisligil GS (December 2010). "Trans-palmitoleic acid, metabolic risk factors, and new-onset diabetes in U.S. adults: a cohort study". Annals of Internal Medicine. 153 (12): 790–9. doi:10.7326/0003-4819-153-12-201012210-00005. PMC 3056495. PMID 21173413.
  8. Matthan NR, Dillard A, Lecker JL, Ip B, Lichtenstein AH (February 2009). "Effects of dietary palmitoleic acid on plasma lipoprotein profile and aortic cholesterol accumulation are similar to those of other unsaturated fatty acids in the F1B golden Syrian hamster". The Journal of Nutrition. 139 (2): 215–21. doi:10.3945/jn.108.099804. PMC 4274120. PMID 19106316.
  9. Elgersma A, Ellen G, Tamminga S (2004). Rapid decline of contents of beneficial omega-7 fatty acids in milk from grazing cows with decreasing herbage allowance. vdf Hochschulverlag. ISBN 9781351442121. OCLC 1019033379.
  10. US Patent 9200236B2, Shinde, Sandip & Kale, "Omega 7 rich compositions and methods of isolating omega 7 fatty acids", published 2015-12-01, assigned to Heliae Dev LLC.
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