A Human Cellular Model for Studying the Regulation of Glucagon-Like Peptide-1 Secretion

Abstract

GLP-1 (glucagon-like peptide-1) is a potent insulin secretagogue released from L cells in the intestine. The regulation of GLP-1 secretion has been described both in vivo and in vitro in several animal species, but data from human cellular models are lacking. For this purpose, factors and cell-signaling pathways regulating GLP-1 secretion were investigated in the NCI-H716 human intestinal cell line. After differentiation, these cells homogeneously produced 16.8 pmol GLP-1/mg protein with a basal release of 4.2% during a 2-h incubation period. Nutrients, such as palmitic acid, oleic acid, and meat hydrolysate, stimulated GLP-1 secretion in a dose-dependent manner, as did the cholinergic agonist carbachol and the neuromediator gastrin-releasing peptide. Along with stimulating GLP-1 release, gastrin-releasing peptide, like ionomycin, increased intracellular calcium levels. Activators of PKA and PKC were able to increase GLP-1 secretion in NCI-H716 cells. However, neither PKA activators nor meat hydrolysate increased proglucagon mRNA levels. These findings indicate that the NCI-H716 cell line constitutes a unique model to study the cellular mechanism of GLP-1 secretion in humans and suggest potential interspecies divergence in the regulation of proglucagon gene expression in enteroendocrine cells.

Dairy protein and leucine alter GLP-1 release and mRNA of genes involved in intestinal lipid metabolism in vitro

“…This sort of range is meaningful to examine not only for understanding physiologic responses to meals but also to determine any potential for therapeutic doses. Furthermore, no toxic effects on cells in vitro have been reported for concentrations up to 3% in previous studies [17,18,28].…”

“…The methods used for the intestinal cell culture have been published [18]. Briefly, human NCI-H716 cells were obtained from the American Type Culture Collection (Rockville, MD, USA).…”

“…On the day of the experiment, supernatant was replaced by Krebs-Ringer bicarbonate buffer containing 0.2% bovine serum albumin (w/v) with or without BCAA or dairy protein. Four different concentrations (0.5%, 1.0%, 2.0%, and 3.0%, wt/vol) were selected based on our previous work [17,18] and others [28] to determine the dose-response effect of isoleucine, valine, skim milk, casein, and whey. For leucine, however, 0.5%, 1.0%, 1.5%, and 2.0% (wt/ vol) were chosen in this study because leucine is poorly soluble in a 3.0% or higher solution.…”

“…Total RNA (1 μg) was reverse-transcribed using Superscript II Reverse Transcriptase (Invitrogen, Carlsbad, CA, USA) with oligo-d(T) [12][13][14][15][16][17][18] as primer. After reverse transcription, the same batch of diluted cDNA was subjected to real-time polymerase chain reaction (PCR) to amplify target genes.…”

“…We previously demonstrated in vivo and in vitro that dietary fiber and meat hydrolysate increase the secretion of glucagon-like peptide-1 (GLP-1), a key satiety hormone, and modulate proglucagon gene expression [17][18][19][20][21][22]. Distinct from alterations in satiety, additional mechanisms may also play a role in body weight regulation by dairy and BCAAs.…”