The Effects of Fasting and Feeding on Preproinsulin Messenger RNA in Rats
Overview
Authors
Affiliations
The purpose of these experiments was to determine whether alterations in preproinsulin messenger (m)RNA activity could account for changes in insulin biosynthesis during fasting and refeeding. Rats were fasted 4 d and then fed for 6, 8, 24, or 48 h. With fasting, body weight decreased 25%, plasma glucose decreased from 6.1 to 2.2 mM, and pancreatic insulin content fell to 40% that of fed animals. Islet RNA decreased to 50% and protein to 55% that of control animals, while islet DNA content remained unchanged. After 6 h of refeeding, islet RNA content increased and was not significantly different from controls. Total islet and preproinsulin mRNA activity was estimated with an mRNA-dependent wheat germ cell-free protein synthesizing system. Preproinsulin and total protein synthesis was linearly dependent upon added RNA at concentrations up to 3 mug. Preproinsulin was identified by its mobility on SDS polyacrylamide gel electrophoresis and by hybrid arrested translation of preproinsulin mRNA. After an 18-h fast, islet mRNA activity decreased 33%; after 4 d mRNA activity decreased to 66% below that of control fed animals. Preproinsulin mRNA activity was decreased, but to a lesser extent, accounting for 20% of total islet protein in fed animals and 46% in the 4-d fasted animals. Total mRNA activity returned to control values after 8 h of refeeding and increased to 150% of controls at 24 and 48 h. Preproinsulin mRNA activity increased more rapidly on refeeding. By 8 h it was 160% of controls.To determine whether changes in preproinsulin mRNA activity were associated with changes in the amount of preproinsulin mRNA, nucleic acid hybridization analysis was performed. Pancreatic RNA from fed and fasted animals was electrophoresed on agarose gels, transferred to diazophenylthio paper, and hybridized to (32)P-labeled preproinsulin complementary (c)-DNA. This analysis demonstrated that changes in mRNA activity were associated with changes in the amount of hybridizable mRNA present. These studies are the first to demonstrate alterations of preproinsulin mRNA under any conditions, and the changes correlate with alterations in rates of insulin biosynthesis.
TFEB and TFE3 control glucose homeostasis by regulating insulin gene expression.
Pasquier A, Pastore N, DOrsi L, Colonna R, Esposito A, Maffia V EMBO J. 2023; 42(21):e113928.
PMID: 37712288 PMC: 10620765. DOI: 10.15252/embj.2023113928.
Phagocytosis in the retina promotes local insulin production in the eye.
Etchegaray J, Kelley S, Penberthy K, Karvelyte L, Nagasaka Y, Gasperino S Nat Metab. 2023; 5(2):207-218.
PMID: 36732622 PMC: 10457724. DOI: 10.1038/s42255-022-00728-0.
β-Cell Control of Insulin Production During Starvation-Refeeding in Male Rats.
Boland B, Brown Jr C, Alarcon C, Demozay D, Grimsby J, Rhodes C Endocrinology. 2017; 159(2):895-906.
PMID: 29244064 PMC: 5776497. DOI: 10.1210/en.2017-03120.
Direct autocrine action of insulin on β-cells: does it make physiological sense?.
Rhodes C, White M, Leahy J, Kahn S Diabetes. 2013; 62(7):2157-63.
PMID: 23801714 PMC: 3712043. DOI: 10.2337/db13-0246.
Proinsulin intermolecular interactions during secretory trafficking in pancreatic β cells.
Haataja L, Snapp E, Wright J, Liu M, Hardy A, Wheeler M J Biol Chem. 2012; 288(3):1896-906.
PMID: 23223446 PMC: 3548498. DOI: 10.1074/jbc.M112.420018.