Post-oral fat-induced satiation is mediated by endogenous CCK and GLP-1 in a fat self-administration mouse model

Triacylglycerol is the most abundant dietary lipid, and a strong stimulator of satiation. Absorption of triacylglycerol in the small intestine occurs in the form of free fatty acids and 2-monoacylglycerol, a process known to trigger not only the release of cholecystokinin (CCK) but also glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). It remains controversial, however, whether endogenously released GLP-1 and PYY are required for fat-induced satiation. Using a self-administration model where mice are trained to self-administer Intralipid 30% intragastrically, we show that blocking the CCK₁ receptors with intraperitoneal devazepide diminishes the post-oral satiation effect of ingested fat. Similarly, s.c. administration of a GLP-1 receptor antagonist with a prolonged half-life (Jant4-C16) also reduced the post-oral satiation effect of ingested fat. Importantly, coadministration of the GLP-1 antagonist together with devazepide increased fat self-infusions to a level equal to the combined blockade of each individual peptide action alone, indicating an additive effect of endogenous CCK and GLP-1 in fat satiation signaling. Blocking the PYY Y₂ receptor did not further enhance the fat intake in devazepide-treated mice. Consistent with the above, we show that voluntary post-oral ingestion of fat increases CCK and GLP-1 plasma levels and is correlated positively with CCK and GLP-1 plasma concentrations. Taken together, our results support the role of endogenous GLP-1 in the regulation of fat intake and suggest that both CCK and GLP-1 are required for the fat satiation signaling.