Dynamics of Fat Absorption and Effect of Sham Feeding on Postprandial Lipema

BACKGROUND & AIMS: Given the importance of postprandial hyperlipidemia to increase risk for atherosclerosis, in the present study, stable isotope-labeled meals were fed to healthy subjects (7 males and 3 females) to investigate the kinetics chylomicron synthesis and the effect of sensory exposure to lipid on metabolism. METHODS: Subjects performed two, 24-hour inpatient studies that entailed consumption of a liquid formula evening meal containing 30 g of oil (+ C-13(2) triolein) on day 1. Breakfast (day 2) consisted of triacylglycerols (TAGs) fed as capsules (30 g oil + C-13(7) triolein) to avoid activation of mouth taste receptors. Next, modified sham feeding of cream cheese occurred over 2 hours. In the 2 trials, the stimulus was either higher fat (HF) or lower fat (LF) cream cheese. A liquid meal was consumed at lunch. Blood sampling occurred intermittently, and chylomicron particles S-f > 400 TAGs were analyzed by gas chromatography-mass spectrometry. RESULTS: C-13(2)-Label was found in fasting-state lipoproteins, and persons with higher body fat percentages showed greater dilution of meal TAGs from endogenous sources. For both trials, 13% +/- 4% of lipoprotein TAGs oleic acid was derived from the previous evening meal. Incremental area under the curve for TAGs during HF was similar to 2.5 times higher than after LF exposure (46 +/- 15 vs 17 +/- 5 mu mol/L/h; P = .04). The greater HF morning lipemia occurred with elevated glucose, insulin, and nonesterified fatty acids peak after lunch. CONCLUSIONS: These data support a connection between enteral lipid metabolism and oral fat exposure, resulting in elevated postprandial lipemia. The results suggest that the intestine may participate in a mechanism coordinating oral fat signaling with control of subsequent macronutrient disposal in the body.