Meat hydrolysate and essential amino acid-induced glucagon-like peptide-1 secretion, in the human NCI-H716 enteroendocrine cell line, is regulated by extracellular signal-regulated kinase1/2 and p38 mitogen-activated protein kinases.
Glucagon-like peptide-1 (GLP-1) is a potent insulin secretagogue released from L-cells in the intestine. Meat hydrolysate (MH) is a powerful activator of GLP-1 secretion in the human enteroendocrine NCI-H716 cell line, but the mechanisms involved in nutrient-stimulated GLP-1 secretion are poorly understood. The objective of this study was to characterize the intracellular signalling pathways regulating MH- and amino acid-induced GLP-1 secretion. Individually, the pharmacological inhibitors, SB203580 (inhibitor of p38 mitogen-activated protein kinase (MAPK)), wortmannin (inhibitor of phosphatidyl inositol 3-kinase) and U0126 (inhibitor of mitogen activated or extracellular signal-regulated protein kinase (MEK1/2) upstream of extracellular signal-regulated kinase (ERK)1/2) all inhibited MH-induced GLP-1 secretion. Further examination of the MAPK pathway showed that MH increased the phosphorylation of ERK1/2, but not p38 or c-Jun N-terminal kinase over 2-15 min. Incubation with SB203580 resulted in a decrease in phosphorylated p38 MAPK and a concomitant increase in the phosphorylation of ERK1/2. Phosphorylation of ERK1/2 was augmented by co-incubation of MH with SB203580. Inhibitors of protein kinase A and protein kinase C did not inhibit MH-induced GLP-1 secretion. In contrast to non-essential amino acids, essential amino acids (EAAs) increased GLP-1 secretion and similar to MH, activated ERK1/2. However, they also activated p38-suggesting type of protein may affect GLP-1 secretion. In conclusion, there appears to be a crosstalk between p38 and ERK1/2 MAPK in the human enteroendocrine cell with the activation of ERK1/2 common to both MH and EAA. Understanding the cellular pathways involved in nutrient-stimulated GLP-1 secretion has important implications for the design of new treatments aimed at increasing endogenous GLP-1 release in type-2 diabetes and obesity.
Reimer
Raylene A
RA
Department of Biochemistry and Molecular Biology, Faculties of Kinesiology and Medicine, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4 Canada. reimer@ucalgary.ca
D000601:Amino Acids, Essential / Q000378:metabolism / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D003864:Depression, Chemical; D020895:Enterocytes / Q000201:enzymology* / Q000378:metabolism; D004789:Enzyme Activation; D052216:Glucagon-Like Peptide 1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008460:Meat; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009570:Nitriles / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011492:Protein Hydrolysates / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000601:Amino Acids, Essential; D000730:Androstadienes; D002070:Butadienes; D007093:Imidazoles; D009570:Nitriles; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011492:Protein Hydrolysates; D011725:Pyridines; D012333:RNA, Messenger; C113580:U 0126; D052216:Glucagon-Like Peptide 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; D000077191:Wortmannin