Intragastric infusion of pea-protein hydrolysate reduces test-meal size in rats more than pea protein

Because protein hydrolysates are digested faster than the corresponding proteins, they may increase or hasten the acute eating-inhibitory effect of protein. Potential mediating mechanisms include accelerated or greater release of satiating gut peptides and activation of metabolic signals that inhibit eating. We tested these hypotheses in adult male rats that were surgically equipped with intragastric (IG) cannulas and adapted to 30-min test meals at dark onset after 14-h food deprivation. Equiosmotic 12 ml loads of saline-urea control (C), 13.6% pea protein (PP), or 13.6% PP hydrolysate (PPH, DSM/DFS, Delft, The Netherlands) solutions were IG infused in 1 min just before test meals. PPH reduced test-meal size compared to C more than PP (-3.8±0.3 g vs. -2.6±0.4 g; P<0.0001). Plasma glutamate increased more after PPH than PP (P<0.0001). Plasma lactate, alanine, insulin, glucagon, GLP-1 and paracetemol (an index of gastric emptying) all increased similarly, and glucose decreased similarly, after PPH or PP. Finally, PPH still reduced test-meal size more than PP (-4.6±0.3 g vs. -3.1±0.4 g; P<0.001) in rats after subdiaphragmatic vagal deafferentation, indicating that abdominal vagal afferents are not necessary for the eating-inhibitory effects of PP and PPH and, by extension, that gut peptides whose satiating effects depend on intact vagal afferents (e.g., CCK and glucagon) do not play crucial roles. Thus, PPH reduced short-term food intake more than PP under our conditions, but the mechanism(s) involved remain unclear.