Effect of endogenous gastric inhibitory polypeptide (GIP) on the removal of triacylglycerol in dogs

In order to clarify the effect of endogenous gastric inhibitory polypeptide (GIP) upon lipid metabolism, the removal of intravenously administered triacylglycerol was investigated following an oral glucose or galactose load in dogs. After an overnight fast, the triacylglycerol emulsion was infused at a constant rate of 1 ml/min for 90 min, and glucose, galactose or tap water was orally administered at 30 min. Blood glucose increased after the glucose load but it did not change following the galactose load or water ingestion. Plasma insulin increased after the glucose load but did not change after galactose or tap water ingestion. Plasma glucagon did not show any discernible change in the three experimental groups. Plasma GIP increased following the glucose or galactose load to 4360 or 1653 pg/ml, respectively. Plasma triacylglycerol increased to the same levels at 30 min in the three experimental groups. The peak levels of plasma triacylglycerol and integrated plasma triacylglycerol for 150 min did not differ in the three groups. Moreover, there was no difference in the removal rate of plasma triacylglycerol following the withdrawal of the fat emulsion. It is concluded from the present study that endogenously released GIP does not elicit any effect upon triacylglycerol removal.