Positional distribution of n-3 fatty acids in triacylglycerols from rat adipose tissue during fish oil feeding.

The present study was designed to investigate the metabolism of the n-3 polyunsaturated fatty acids (PUFA) in adipose tissue and its dependence upon dietary factors. Changes in the positional distribution of the fatty acids in triacylglycerols from retroperitoneal adipose tissue were studied as a function of time on rats fed for 4 wk a diet enriched with fish oil. The stereospecific analysis of triacylglycerols by Grignard degradation. This was followed by synthesis of rac-phosphatidic acids and treatment with phospholipase A2. In the triacylglycerols of the fish oil diet, 57% of the total n-3 fatty acids were in position 3, i.e., two-thirds of 20:5n-3 and 22:5n-3 were esterified in sn-3 position, whereas 22:6n-3 was equally distributed in positions 2 and 3. After 4 wk of feeding fish oil, the fatty acid composition of adipose tissue triacylglycerols reached a steady state. Half of the n-3 fatty acids were found in position 3, namely 75% of 22:5n-3, 50% of 20:5n-3 and 18:4n-3 and 45% of 22:6n-3, the latter being equally distributed in positions 2 and 3. This pattern of distribution resembled that found in triacylglycerols of the fish oil diet, except for a higher proportion of 20:5n-3 in adipose tissue in position 1 at the expense of position 3. Throughout the 4-wk period of fish oil feeding, the distribution pattern of minor n-3 fatty acids (18:4n-3 and 22:5n-3) in adipose tissue triacylglycerols remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)