Equivalent Increases in Circulating GLP-1 Following Jejunal Delivery of Intact and Hydrolysed Casein: Relevance to Satiety Induction Following Bariatric Surgery

BACKGROUND: Both Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) decrease the latency of food delivery to the proximal small intestine. This is implicated in exaggerated post-prandial release of glucagon-like peptide 1 (GLP-1), which provokes early satiety and reductions in food intake. Altered stomach anatomy also creates a deficit in enzymatic pre-processing. The impact of this state effect as a modulator of gut hormone responses remains underexplored. METHODS: A double-blind cross-over trial study was conducted in 13 healthy subjects assigned to receive in the fasted state and in random order at 1 week apart, a direct jejunal infusion of either intact casein or a casein hydrolysate. Downstream effects on GLP-1 release, ratings of hunger and fullness and food and water intake on each study day were recorded when an ad libitum meal was provided 30 min after the infusion. RESULTS: Circulating GLP-1 was increased 25 min after infusions and peaked to a similar degree at 15 min post-meal initiation. The hormone surge had no impact on ratings of hunger and fullness ahead of the ad libitum meal. The kinetic and magnitude of satiation following each infusion was not significantly different. Food and water intake were likewise not differentially impacted by the two infusion types. CONCLUSIONS: Protein macronutrient state upon arrival in the small intestine does not in isolation impact upon GLP-1 responses and subsequent onset of satiety. This potentially points to rate of delivery being the dominant factor in exaggerated post-prandial GLP-1 responses in patients post-RYGB and VSG.