Blood Sampling From Rat Ileal Mesenteric Vein Revealed a Major Role of Dietary Protein in Meal-Induced GLP-1 Response.

Tohru Hira,Hiroshi Hara,Madoka Sekishita

doi:10.3389/fendo.2021.689685

Tohru Hira, Hiroshi Hara + Show 1 more

Open Access

https://doi.org/10.3389/fendo.2021.689685

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Abstract

The present study was conducted to examine region-dependent glucagon-like peptide-1 (GLP-1) responses to “meal ingestion” under physiological (conscious and unrestrained) conditions using rats with a catheter inserted into either the portal vein (PV) or the ileal mesenteric vein (ILMV). After recovery from the cannulation surgery, blood samples were collected from either PV or ILMV catheter before and after the voluntary ingestion of test diets. After an AIN-93G standard diet ingestion, GLP-1 concentration was higher in ILMV than in PV, and postprandial responses of peptide-YY (PYY) had similar trend, while that of glucose dependent-insulinotropic polypeptide showed an opposite trend to GLP-1/PYY responses. In a separated experiment, a protein-enriched diet containing casein at 25% wt/wt transiently increased GLP-1 concentration only in ILMV; however, a protein-free diet did not increase GLP-1 concentrations in PV or ILMV. These results indicate that postprandial GLP-1 is immediately released from the distal intestine under physiological conditions, and that dietary protein has a critical role in the enhancement of postprandial GLP-1 response.

Highlights

Gut hormones are considered to be locally produced in specific regions of the gastrointestinal tract [1, 2]
In experiment 1, rats consumed more than 95% of the diet (2.80 ± 0.05 g in the portal vein (PV) group and 2.75 ± 0.04 g in the ileal mesenteric vein (ILMV) group) provided at the dose of 10 g/kg, within 15 min
The concentration of active glucagon-like peptide-1 (GLP-1) increased in the ILMV group immediately (15 min) after ingesting the meal, whereas it showed no increment in the PV group (Figure 2C)

Summary

Introduction

Gut hormones are considered to be locally produced in specific regions of the gastrointestinal tract [1, 2]. GLP-1 and PYY production in the proximal small intestine [3,4,5] could contribute to a rapid response of these hormones [6, 7] after a meal. The primary purpose of the present study was to demonstrate regional gut hormone responses to voluntary meal ingestion under physiological (conscious and unrestrained) conditions, in a rat model. For this purpose, we developed surgical model rats by inserting a catheter into the mesenteric vein of the distal small intestine (ileal mesenteric vein, ILMV). We firstly compared gut hormone concentrations in the plasma samples collected from the ILMV to those from the portal vein (PV) of another group of rats with a portal catheter [8, 9]

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