T. Xia et al., SELECTIVE RETENTION OF ESSENTIAL FATTY-ACIDS - THE ROLE OF HEPATIC MONOACYLGLYCEROL ACYLTRANSFERASE, The American journal of physiology, 265(2), 1993, pp. 180000414-180000419
In the suckling rat, chick embryo, and hibernating marmot, fatty acids
provide the major source of energy, and despite the high rate of hepa
tic beta-oxidation, these animals selectively retain long-chain polyun
saturated derivatives of C18:2n-6 and C18:3n-3. To determine whether t
he hepatic microsomal activity monoacylglycerol acyltransferase (MGAT)
(EC 2.3.1.22) could provide a mechanism to selectively acylate monoac
ylglycerols that contain essential fatty acids, we tested the ability
of MGAT activity from each of the three species to acylate sn-2-monoC1
8:1-, sn-2-monoC18:2-, sn-2-monoC18:3-, and sn-2-monoC20:4-glycerols.
Hepatic MGAT activity acylated sn-2-monoC18:3-glycerol and sn-2-monoC1
8:2-glycerol in preference to sn-2-monoC18: 1-glycerol in each of the
three different lipolytic animals. MGAT's acyl group specificity could
not be explained by invoking differences in membrane fluidity because
the apparent affinity for sn-2-monoC20:4-glycerol was not increased.
Further, sn-2-monoC18:3-glycerol remained a preferred substrate under
assay conditions when both the C18:3 and C18:1 species were present in
equal amounts. As would be predicted in the presence of high activity
of a selective MGAT, the hepatic glycerolipids from neonatal rats sho
wed increases in dienoic, trienoic, and C22:6 fatty acids and relative
decreases in monoenoic, saturated, and C20:4 fatty acids. We hypothes
ize that, during lipolysis, the reacylation of sn-2-monoacylglycerols
by MGAT may provide a mechanism by which essential fatty acids are ret
ained within specific tissues.