Gut emptying affects dietary fat contribution to postprandial lipemia following sequential meals in healthy subjects

Objective The present study examined the kinetic of plasma triacylglycerol (TAG) and gut emptying after sequential ingestion of breakfast and lunch, and the contribution of dietary fat ingested at breakfast to subsequent TAG after lunch. Methods Nine subjects ingested a breakfast (0730 h) and a lunch (1200 h) containing 25 and 44 g of fat, respectively. [1-13C] palmitate was added in breakfast only. Plasma TAG and chylomicron-TAG (CM-TAG) concentrations and [1-13C] palmitate enrichment were sequentially measured. On a consecutive day, an identical breakfast labeled with 123I-Lipiodol was ingested, followed by a lunch for three controls. 123I-Lipiodol dynamics was followed in vivo by scintigraphic imaging focused on the stomach, small bowel, and thoracic duct arch. Results An early rise in plasma and CM-TAG was observed after lunch ingestion. After breakfast, [1-13C] palmitate enrichment was maximal 150 and 210 min in plasma TAG and CM-TAG, respectively, decreased thereafter, and increased rapidly (50 min for plasma TAG and 30 min for CM-TAG) after lunch ingestion. Scintigraphic imaging appeared to show that fat ingested at breakfast was retained in part within the gut at lunch time. For the three subjects who ingested a lunch, a decrease of activity in the stomach and small bowel and a tendency for increased activity in the thoracic arch were observed. Conclusion Contribution of fat ingested at breakfast to lipemia after lunch is confirmed. Fat ingested at breakfast was partly retained within the gut and was mobilized after lunch ingestion, as assessed by acceleration of gut emptying and thoracic duct flow after lunch.