Why Is Docosahexaenoic Acid Of Interest

Understanding the basis for lipid diversity remains one of the major unsolved problems in membrane biology. A plausible explanation of why biological membranes are composed of hundreds to perhaps thousands of different lipid species, when it initially appears that only a few would suffice, has not been forthcoming. Clearly, unique functions for many of the different lipids have yet to be uncovered. All phospholipids have a role in forming the lipid bilayer, providing proper membrane surface charge and supplying the appropriate hydrophobic environment in which membrane proteins flourish. Each lipid species' unique role, if one exists, must reside with some other aspect of the membrane, perhaps a role in maintaining unusual structure (e.g., nonbilayer phase, regions of high curvature, etc.), supporting specific enzyme regulation, or furnishing a specialized role (e.g., platelet-activating factor). These functions may be accomplished through the existence of unique lipid domains (i.e., specialized and diverse membrane areas created by differential affinities of phospholipids for other membrane components) (Edidin, 1993).

Of particular interest to us is understanding the membrane role for the omega-3 fatty acid, docosahexaenoic acid (DHA, 22:6A4,7,10,13,16,19), the longest chain and most unsaturated fatty acid commonly found in biological membranes (Salem et al., 1986). It represents the extreme example of an omega-3 fatty acid. Once incorporated into a membrane, DHA will become an important component of the hydrophobic interior where it will affect membrane order or fluidity, thickness, domain size and stability, permeability, lipid phase, and, through interaction with membrane proteins, even biochemical activity (Salem et al., 1986; Stubbs & Smith, 1984). The presence of DHA in membranes is necessary for normal neurologic development (Menkes et al., 1962) and vision (Neuringer et al., 1988), as well as for benefits in various diseases, including atherosclerosis

From: Fatty Acids: Physiological and Behavioral Functions Edited by: D. Mostofsky, S. Yehuda, and N. Salem Jr. © Humana Press Inc., Totowa, NJ

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