Putative "Age Beneficial" Effects of Omega Oils





Lloyd A. Horrocks* and Akhlaq A. Farooqui.

Dept. of Molecular & Cellular Biochem., 1645 Neil Ave., The Ohio State Univ., Columbus, OH 43210-1218.



Most polyunsaturated fatty acids (PUFA) are either n-6 (omega-6) or n-3 (omega-3). The n-6 PUFA include arachidonic acid, 20:4 n-6, the precursor of the most common prostaglandins and leukotrienes, the eicosanoids. These have essential functions, but are also involved in inflammation and promote cell division. The dietary precursor of 20:4 n-6 is linoleic acid, 18:2 n-6. The n-3 PUFA include the dietary precursor, alpha-linolenic acid, 18:3 n-3, EPA, 20:5 n-3, and DHA, 22:6 n-3. About one-twentieth of the dietary 18:3 n-3 is converted to DHA. This conversion requires peroxisomal enzymes. EPA and DHA are also obtained from fish and eggs. EPA is anti-inflammatory because it competes with 20:4 n-6 as a substrate for the formation of a prostaglandin. The prostaglandin from EPA is not inflammatory.

DHA promotes cell differentiation and stimulates the synthesis of the peroxisomal enzymes necessary for plasmalogen synthesis. Plasmalogens are involved in signaling mechanisms in the brain. DHA turns over rapidly in the brain, but most is then recycled back into phospholipids. DHA is very concentrated in the retina where it is involved in the transduction of light to electrical signals. DHA is also enriched in the nerve-endings where it is mostly in the ethanolamine plasmalogens. Adrenoleukodystrophy (ALD) is a genetic disease of peroxisomes in which DHA, and thus plasmalogens, are not formed. The infants develop mental retardation because myelin, which requires plasmalogen, is not formed. ALD can be treated with DHA.

The first lipid changes in Alzheimer disease (AD) are decreased levels of DHA and ethanolamine plasmalogens. The breakdown of ethanolamine plasmalogens may enable the abnormal cleavage by gamma-secretase to produce Abeta. The lack of plasmalogens also leads to the loss of nerve-endings. Some success has been had with AD treatment with DHA supplements.




Key words: Omega-3, DHA, EPA, plasmalogens, eicosanoids







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