Glucagon-like peptide-1 affects gene transcription and messenger ribonucleic acid stability of components of the insulin secretory system in RIN 1046-38 cells.
It has been previously demonstrated that the enteric hormone glucagon-like peptide-1 (7-36 amide) (GLP-1) has acute effects on glucose-induced insulin secretion by RIN 1046-38 cells. In this study, we investigated the effects of extended exposure of RIN 1046-38 cells to GLP-1 and examine the mechanism by which GLP-1 synergizes with glucose in stimulating insulin secretion. Compared with cells cultured with glucose alone, incubation of cells with glucose plus 1 or 10 nM GLP-1 for 12 or 24 h significantly increased insulin release by about 3-fold, intracellular insulin content by 1.5-fold, and insulin messenger RNA (mRNA) by almost 2.5-fold. The insulinotropic effects of GLP-1 on RIN 1046-38 cells were accompanied by an up-regulation of both glucose transporter-1 (GLUT-1) and hexokinase I mRNA by about 2-fold. mRNA levels of GLUT-2 and glucokinase, which were low in controls, were unchanged by GLP-1 treatment. Treatment of cells with a transcription inhibitor, actinomycin D, demonstrated that elevated insulin mRNA levels after a GLP-1 exposure are mainly due to stabilization of the mRNA. In contrast, the elevated mRNA levels of GLUT-1 and hexokinase I are the result of increased transcription stimulated by GLP-1 exposure. Actinomycin D blunted the GLP-1 effect on insulin release but did not affect GLP-1 mediated elevation of insulin mRNA. This suggests that actinomycin D inhibits the transcription of the proteins necessary for insulin biosynthesis and insulin release, such as GLUT-1 and hexokinase I. Our study suggests that the mechanisms by which extended exposure of RIN 1046-38 cells to GLP-1 increases glucose-stimulated insulin secretion include significant up-regulation of glucose-sensing elements.
Wang
Y
Y
Laboratory of Clinical Physiology, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA.
Egan
J M
JM
Raygada
M
M
Nadiv
O
O
Roth
J
J
Montrose-Rafizadeh
C
C
D000818:Animals; D017077:Culture Media, Conditioned; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004355:Drug Stability; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000494:pharmacology; D051272:Glucose Transporter Type 1; D006593:Hexokinase / Q000235:genetics; D007328:Insulin / Q000235:genetics* / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D010190:Pancreatic Neoplasms; D010446:Peptide Fragments / Q000494:pharmacology*; D011498:Protein Precursors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D017077:Culture Media, Conditioned; D051272:Glucose Transporter Type 1; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D010446:Peptide Fragments; D011498:Protein Precursors; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; D003609:Dactinomycin; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D003513:Cycloheximide; D006593:Hexokinase; D005947:Glucose