An Exploratory Study of the Role of Dietary Proteins in the Regulation of Intestinal Glucose Absorption

Abstract

Several studies have demonstrated that high protein diets improve glucose homeostasis. Nevertheless, the mechanisms underlying this effect remain elusive. This exploratory study aims to screen and compare the acute effects of dietary proteins from different sources on intestinal glucose absorption. Six dietary proteins from various sources were thus selected and digested thanks to the INFOGEST static gastrointestinal digestion protocol. The digested proteins were able to decrease intestinal glucose absorption in vitro and ex vivo. Moreover, acute ingestion of casein and fish gelatin led to improved glucose tolerance in Wistar rats without significant effect on insulin secretion. In parallel, GLUT2 mRNA expression in enterocytes was decreased following short-term incubation with some of the digested proteins. These results strengthen the evidence that digested protein-derived peptides and amino acids are key regulators of glucose homeostasis and highlight their role in intestinal glucose absorption.

In Vivo and In Vitro Comparison of the DPP-IV Inhibitory Potential of Food Proteins from Different Origins after Gastrointestinal Digestion

“…However, the mechanism(s) of action behind the role of dietary proteins in glucose homeostasis is not yet fully understood. Currently, researchers are focusing on mechanisms involving the direct effect of protein-derived peptides and amino acids on (i) the stimulation of insulin secretion by pancreatic cells [ 19 ], (ii) the stimulation of incretin secretion (GIP, GLP-1) and cholecystokinin by enteroendocrine cells [ 20 , 21 , 22 , 23 ], (iii) the inhibition of intestinal glucose uptake [ 24 ], and (iv) the inhibition of the enzymes involved in the regulation of the glucose level (i.e., DPP-IV and α-glucosidase) [ 25 ]. As a consequence, many studies have focused on natural DPP-IV inhibitors originating from the hydrolysis of dietary proteins [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”

Digested casein phosphopeptides impact intestinal calcium transport in vitro

“…30 Simulated fluid composition and the method are described in a previous study. 31 Briefly, 2 grams of CPP-preparation solubilized in 8 mL of water were first mixed with 8 mL simulated salivary fluid for 5 minutes, at pH 7.0. Then, simulated gastric fluid containing pepsin from Sigma-Aldrich (St Louis, MO, USA, P6887, 6500 U mL −1 ) was added volume to volume in the reactor and incubated for 2 h, at pH 3.0.…”

In vitro comparison of whey protein isolate and hydrolysate for their effect on glucose homeostasis markers

“…26 The simulated fluid composition and the different digestion steps were described previously. 27 Briefly, the samples previously solubilized in water (8 mL) were added to the simulated salivary fluid (8 mL) for 5 minutes at pH 7.0. In the second step, simulated gastric fluid containing pepsin (SIGMA, P6887, 6500 U mL −1 ) was added (volume to volume) to the incubator, and the whole mixture was incubated for 2 hours at pH 3.0.…”

“…Then, the supernatants were frozen at −80 °C until the day of analysis. Secreted GLP-1 was measured using the Glucagon-Like Peptide-1 7–36 Amide EIA kit, EK-028-11CE (Phoenix Pharmaceuticals, Burlingame, USA). The viability of the cells (>95%) was verified for each condition using the cell counting kit-8 (CCK-8, Tebu-Bio, Le Perray en Yvelines, France).…”

“…WPI and WPH (2 grams of protein) were digested in vitro according to the harmonized static INFOGEST protocol (25), which was adapted for protein alone (26). The simulated fluid composition and the different digestion steps were described previously (27). Briefly, the samples previously solubilized in water (8 mL) are added to the simulated salivary fluid (8 mL) for 5 minutes at pH 7.0.…”