METABOLISM OF EMULSIONS CONTAINING MEDIUM-CHAIN AND LONG-CHAIN TRIGLYCERIDES OR INTERESTERIFIED TRIGLYCERIDES

This study compares the clearing and metabolism of three different lip id emulsions. They had the same phospholipid emulsifier and similar pa rticle sizes. In one (LLL) the core component was long-chain triglycer ides (TG), the second (MMM/LLL) contained equal molar amounts of mediu m- and long-chain TG, the third (MLM) contained synthetic TG with medi um-chain (M) fatty acids in the 1,3-positions and a long-chain (L) fat ty acid in the 2-position. In model experiments with bovine lipoprotei n lipase, the MMM component was hydrolyzed preferentially in the MMM/L LL emulsion so that the initial products were M fatty acids and M mono glycerides. The MLM emulsion, in contrast, gave M fatty acids and form ation of LMG (monoglyceride) throughout hydrolysis. For in vivo studie s [H-3]oleic acid was incorporated into the emulsion TG as marker for the long-chain component. After bolus injection to rats, the MMM/LLL a nd MLM emulsions were cleared more rapidly than the LLL emulsion. This was true at all TG loads studied (4-64 mg for a 200 g rat). The label ed oleic acid was oxidized somewhat more rapidly when administered in the MLM emulsion compared to the MMM/LLL emulsion. There were only sli ght differences in tissue distribution of label. Hence, differences in in vivo metabolism of the long-chain fatty acids were small compared to the marked differences in TG structure and in patterns of product r elease during in vitro lipolysis.