Recoveries of rat lymph FA after administration of specific structured¹³C‐TAG

Abstract

The potential of the specific structured TAG MLM [where M = caprylic acid (8:0) and L = linoleic acid (18:2n-6)] is the simultaneous delivery of energy and EFA. Compared with long-chain TAG (LLL), they may be more rapidly hydrolyzed and absorbed. This study examined the lymphatic recoveries of intragastrically administered L*L*L*, M*M*M*, ML*M, and ML*L* (where * = 13C-labeled FA) in rats. Lymph lipids were separated into lipid classes and analyzed by GC combustion isotope ratio MS. The recoveries of lymph TAG 18:2n-6 8 h after administration of L*L*L*, ML*M, and ML*L* were 38.6, 48.4, and 49.1%, respectively, whereas after 24 h the recoveries were approximately 50% in all experimental groups. The exogenous contribution to lymph TAG 18:2n-6 was approximately 80 and 60% at maximum absorption of the specific structured TAG and L*L*L*, respectively, 3-6 h after administration. The tendency toward more rapid recovery of exogenous long-chain FA following administration of specific structured TAG compared with long-chain TAG was probably due to fast hydrolysis. The lymphatic recovery of 8:0 was 2.2% 24 h after administration of M*M*M*. This minor lymphatic recovery of exogenous 8:0 was probably due to low stimulation of chylomicron formation. These results demonstrate tendencies toward faster lymphatic recovery of long-chain FA after administration of specific structured TAG compared with long-chain TAG.

Lymphatic recovery of exogenous oleic acid in rats on long chain or specific structured triacylglycerol diets

“…The lymphatic recovery of the exogenous fatty acids can be determined by isotope labeling. In support of the above-mentioned lymphatic transport studies we recently found a faster lymphatic recovery of 13 Clabeled 18:2n-6, when incorporated in MLM (M = caprylic acid [8:0], L = 18:2n-6) compared with long-chain triacylglycerols (18). In contrast, the lymphatic recovery of long-chain fatty acids after continuous infusion of 14 C-labeled LLL was significantly higher than after infusion of two 14 C-labeled structured triacylglycerols, MLM and MML (L = 18:2n-6, M = 8:0) (19).…”

“…This is in line with earlier results from our laboratory, where the lymphatic transport of docosahexaenoic acid (22:6n-3) and eicosapentaenoic acid (20:5n-3) was higher during the first hours after administration of an MLM bolus compared with randomized oil, but after 24 h, the accumulated lymphatic transport was similar without differences in regard to triacylglycerol structure (15). Likewise, a faster lymphatic recovery of 13 C-labeled 18:2n-6 was observed in rats after consumption of MLM compared with LLL, but the accumulated recovery after 24 h was the same in both groups (18).…”

“…Our results show that the MLM bolus provided a better absorption of 18:1n-9 compared with the LLL bolus in rats on the MLM diet. Studies without adaptation to specific structured triacylglycerols for a longer period have demonstrated higher (14)(15)(16)18) or lower (19,20) lymphatic transport of long-chain fatty acids after administration of MLM compared with LLL or randomized oils.…”

Organ-specific dietary fatty acid uptake in humans using positron emission tomography coupled to computed tomography

“…Chylomicrons are then secreted and transported in the splanchnic lymphatic circulation to the thoracic duct and reach the circulation in the left subclavicular vein. Although short-and medium-chain fatty acids may be absorbed and transported directly into the portal circulation for efficient oxidative metabolism in the liver (31,36,37), this process is probably very limited for long-chain fatty acids, except perhaps in conditions associated with portal hypertension (5). The present study clearly demonstrates very poor direct absorption of 18 FTHA into the portal circulation and preferential uptake and secretion into chylomicrons.…”

Postprandial lipid responses of butter blend containing fish oil in a single‐meal study in humans

“…Correct determinations of sample 13 C/ 12 C ratios were checked by standard samples with known d values. The calculations were done as previously described [24].…”