Incorporation, metabolism and positional distribution of trans-unsaturated fatty acids in developing and mature brain. Comparison of elaidate and oleate administered intracerebrally.

Mixtures of [1-14C]elaidic acid and [9,10-3H]oleic acid, as well as [1-14C]elaidic or [1-14C]oleic acid alone, were administered by intracerebral injection to 10-day old and adult rats to examine the relative incorporation and metabolism of trans- and cis-monounsaturated fatty acids in developing and mature brain. Rates and extents of total incorporation of label from trans- and cis-acid into complex lipids were similar. Maximum labeling of the neutral lipid, mainly triacylglycerol and cholesterol, occurred prior to 4 h after injection whereas phospholipid, mainly choline phosphoglyceride, was maximally labeled at 4--8 h after injection. The decrease in labeled phospholipid from 24 to 90 h was greater with elaidate than with oleate. At 8 h labeled elaidic acid was preferentially esterified in the 1-position of all phosphoglycerides whereas labeled oleic acid, in contrast to the positional distribution of endogenous oleate, was randomly distributed. Label from elaidate found in palmitate increased with time to 26% of the total recovered label by 48 h. Thus, although some of the trans-fatty acid is oxidized and its labeled carbon is redistributed, most is incorporated unaltered into complex lipid of brain at rates similar to those for its cis-isomer. The developing central nervous system, therefore, does not metabolically exclude the trans-acid, elaidic acid, from membrane lipids.