Adaptive changes in insulin secretion by islets from neonatal rats raised on a high-carbohydrate formula.
Artificial rearing of neonatal rats on a high-carbohydrate (HC) milk formula resulted in the immediate onset of hyperinsulinemia. This study examines, in islets of 12-day-old HC rats, adaptive changes that support the hyperinsulinemic state. Increases in plasma glucagon-like peptide-1 (GLP-1) levels and islet GLP-1 receptor mRNA supported increased insulin secretion by HC islets. Isolated HC islets, but not mother-fed (MF) islets, secreted moderate amounts of insulin in a glucose- and Ca(2+)-independent manner. Under stringent Ca(2+)-free conditions and in the presence of glucose, GLP-1 plus acetylcholine augmented insulin release to a larger extent in HC islets. Levels of adenylyl cyclase type VI mRNA and activities of protein kinase A, protein kinase C, and calcium calmodulin kinase II were increased in HC islets. A tenfold increase in norepinephrine concentration was required to inhibit insulin secretion in HC islets compared with MF islets, indicating reduced sensitivity to adrenergic signals. This study shows that significant alterations at proximal and distal sites of the insulin secretory pathway in HC islets may support the hyperinsulinemic state of these rats.
Srinivasan
M
M
Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 14214, USA.
Aalinkeel
R
R
Song
F
F
Lee
B
B
Laychock
S G
SG
Patel
M S
MS
D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000502:physiology; D005934:Glucagon / Q000097:blood; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D005947:Glucose / Q000494:pharmacology; D006946:Hyperinsulinism / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000201:enzymology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010446:Peptide Fragments / Q000097:blood; D011247:Pregnancy; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011498:Protein Precursors / Q000097:blood; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018027:Receptors, Glucagon / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D015220:Calcium Channels; D004040:Dietary Carbohydrates; D004791:Enzyme Inhibitors; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; D012333:RNA, Messenger; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D005947:Glucose; D002118:Calcium; D009638:Norepinephrine