Abstract
In mammals, polyunsaturated fatty acids (PUFAs) such as linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3) cannot be synthesized de novo, and therefore are essential fatty acids (EFAs). EFAs and their downstream long-chain PUFAs (LC-PUFAs) such as arachidonic acid (20:4n-6), EPA (20:5n-3), and DHA (22:6n-3) are localized to cell membranes as phospholipid esters and play critical roles in regulating membrane structures, fluidity and permeability. In addition, the certain classes of PUFAs are precursors of eicosanoid such as prostaglandins and leukotrienes, and thus mediate numerous physiological processes. Essential fatty acid deficiency (EFAD) occurs when less than 1% of total calories are provided from EFA such as linoleic acid. EFAD has been related to various clinical features such as skin lesions, impaired growth, infertility and steatosis. In the EFA-deficient state, Mead acid (20:3n-9) is endogenously synthesized from oleic acid (18:1n-9). Although the significance of mead acid in an EFAD state is not well understood, Mead acid is thought to be used as a substitute for essential PUFAs in biological membranes. This article introduces the metabolism and function of dietary and endogenous PUFA including recent studies.
