Postruminal Casein Infusion and Exogenous Glucagon-Like Peptide 2 Administration Differentially Stimulate Pancreatic α-Amylase and Small Intestinal α-Glucosidase Activity in Cattle

Ronald J Trotta; Kendall C Swanson; James L Klotz; David L Harmon

doi:10.1016/j.tjnut.2023.08.009

Postruminal Casein Infusion and Exogenous Glucagon-Like Peptide 2 Administration Differentially Stimulate Pancreatic α-Amylase and Small Intestinal α-Glucosidase Activity in Cattle

J Nutr. 2023 Oct;153(10):2854-2867. doi: 10.1016/j.tjnut.2023.08.009. Epub 2023 Aug 10.

Authors

Ronald J Trotta¹, Kendall C Swanson², James L Klotz³, David L Harmon⁴

Affiliations

¹ Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States.
² Department of Animal Science, North Dakota State University, Fargo, ND, United States.
³ Forage-Animal Production Research Unit, USDA, ARS, Lexington, KY, United States.
⁴ Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States. Electronic address: david.harmon@uky.edu.

PMID: 37573014
DOI: 10.1016/j.tjnut.2023.08.009

Abstract

Background: Increasing luminal carbohydrate flow decreases pancreatic α-amylase activity but can increase jejunal maltase activity, suggesting that regulation of carbohydrase activity is perhaps uncoordinated in response to luminal carbohydrate flow. Increasing luminal casein flow increases pancreatic α-amylase activity in cattle, and exogenous glucagon-like peptide 2 (GLP-2) has been shown to increase small intestinal α-glucosidase activity in nonruminants.

Objectives: The objective was to evaluate the effects of postruminal casein infusion, exogenous GLP-2, or their combination on endogenous pancreatic and small intestinal carbohydrase activity in cattle postruminally infused with starch.

Methods: Holstein steers [n = 24; 250 ± 23 kg body weight (BW)] received a continuous abomasal infusion of 3.94 g raw corn starch/kg of BW combined with either 0 or 1.30 g casein/kg of BW. Steers received subcutaneous injections in 2 equal portions daily of excipient (0.5% bovine serum albumin) or 100 μg GLP-2/kg of BW per day. At the end of the 7-d treatment period, steers were slaughtered for tissue collection. Data were analyzed using the MIXED procedure of SAS version 9.4 (SAS Institute Inc.).

Results: Postruminal casein infusion increased (P ≤ 0.03) pancreatic mass by 12.6%, total pancreatic α-amylase activity by 50%, and postruminal starch disappearance from 96.7% to 99.3%. Exogenous GLP-2 increased (P < 0.01) total small intestinal and mucosal mass by 1.2 kg and 896 g, respectively. Relative to control, GLP-2 and casein + GLP-2 increased (P = 0.04) total small intestinal α-glucosidase activity by 83.5%. Total small intestinal maltase, isomaltase, and glucoamylase activity was 90%, 100%, and 66.7% greater for GLP-2 and casein + GLP-2 steers compared with control.

Conclusions: Casein increased pancreatic α-amylase activity, GLP-2 increased small intestinal α-glucosidase activity, and the combination of casein and GLP-2 increased both pancreatic α-amylase activity and small intestinal α-glucosidase activity. This novel approach provides an in vivo model to evaluate effects of increasing endogenous carbohydrase activity on small intestinal starch digestion.

Keywords: bovine; casein; glucagon-like peptide 2; glucoamylase; intragastric infusion; isomaltase; maltase; protein; ruminant; starch digestion.