Objective: Diacylglycerol (DAG)-rich oil has been suggested to suppress postprandial hyperlipidemia and promote negative caloric balance by increasing energy expenditure (EE), due to small intestine physiochemical dynamics that differ from triacylglycerol (TAG). We studied the effect of DAG on postprandial glucose/insulin metabolism by loading of carbohydrate with oil. Further, to reveal the mechanism for increased EE by DAG, we measured plasma serotonin, which is mostly present in the small intestine and mediates peripheral sympathetic thermogenesis.
Methods and procedures: Randomized crossover study with 2-week wash-out interval between differing fat ingestion. Seven male, lean, Japanese students ingested DAG or TAG oil with 40 g of carbohydrate. Measurements of metabolic parameters were performed before and at 2, 4, and 6 h after fat ingestion. Plasma serotonin levels and cholesterol concentration in each lipoprotein were measured using high-performance liquid chromatography (HPLC).
Results: The substitution of DAG for TAG decreased very-low-density lipoprotein-cholesterol (VLDL-C) by 45.6% at 2 h, and decreased serum insulin by 41.3% at 4 h after ingestion. The incremental area under the curve (IAUC) for VLDL-C was positively correlated with the IAUC for insulin. Concurrently, DAG elevated plasma serotonin levels by 47.3% at 2 h, while TAG did not influence.
Discussion: This study indicates that the substitution of DAG for TAG suppresses the postprandial increase in serum VLDL-C and insulin. This study also demonstrates that DAG ingestion increases plasma serotonin, proposing a possible mechanism for a postprandial increase in EE by DAG.