High Glucose Suppresses Human Islet Insulin Biosynthesis by Inducing miR-133a Leading to Decreased Polypyrimidine Tract Binding Protein-Expression

Rikard G. Fred, Claus Heiner Bang-Berthelsen, Thomas Mandrup-Poulsen, Lars G. Grunnet, Nils Welsh, Mick F. Tuite (Editor)

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Abstract

Background: Prolonged periods of high glucose exposure results in human islet dysfunction in vitro. The underlying mechanisms behind this effect of high glucose are, however, unknown. The polypyrimidine tract binding protein (PTB) is required for stabilization of insulin mRNA and the PTB mRNA 3'-UTR contains binding sites for the microRNA molecules miR-133a, miR-124a and miR-146. The aim of this study was therefore to investigate whether high glucose increased the levels of these three miRNAs in association with lower PTB levels and lower insulin biosynthesis rates.Methodology/Principal Findings: Human islets were cultured for 24 hours in the presence of low (5.6 mM) or high glucose (20 mM). Islets were also exposed to sodium palmitate or the proinflammatory cytokines IL-1 beta and IFN-gamma, since saturated free fatty acids and cytokines also cause islet dysfunction. RNA was then isolated for real-time RT-PCR analysis of miR-133a, miR-124a, miR-146, insulin mRNA and PTB mRNA contents. Insulin biosynthesis rates were determined by radioactive labeling and immunoprecipitation. Synthetic miR-133a precursor and inhibitor were delivered to dispersed islet cells by lipofection, and PTB was analyzed by immunoblotting following culture at low or high glucose. Culture in high glucose resulted in increased islet contents of miR-133a and reduced contents of miR-146. Cytokines increased the contents of miR-146. The insulin and PTB mRNA contents were unaffected by high glucose. However, both PTB protein levels and insulin biosynthesis rates were decreased in response to high glucose. The miR-133a inhibitor prevented the high glucose-induced decrease in PTB and insulin biosynthesis, and the miR-133a precursor decreased PTB levels and insulin biosynthesis similarly to high glucose.Conclusion: Prolonged high-glucose exposure down-regulates PTB levels and insulin biosynthesis rates in human islets by increasing miR-133a levels. We propose that this mechanism contributes to hyperglycemia-induced beta-cell dysfunction.
Original languageEnglish
Article numbere10843
JournalP L o S One
Volume5
Issue number5
Number of pages9
ISSN1932-6203
DOIs
Publication statusPublished - 2010
Externally publishedYes

Keywords

  • Agricultural and Biological Sciences (all)
  • Biochemistry, Genetics and Molecular Biology (all)
  • Medicine (all)
  • gamma interferon
  • glucose
  • insulin
  • interleukin 1beta
  • microRNA
  • microRNA 124a
  • microRNA 133a
  • microRNA 146
  • polypyrimidine tract binding protein
  • saturated fatty acid
  • unclassified drug
  • cytokine
  • messenger RNA
  • MIRN133 microRNA, human
  • MIRN146 microRNA, human
  • palmitic acid
  • RNA precursor
  • article
  • cell culture
  • controlled study
  • down regulation
  • human
  • human cell
  • immunoprecipitation
  • insulin synthesis
  • isotope labeling
  • pancreas islet cell
  • protein expression
  • real time polymerase chain reaction
  • RNA analysis
  • RNA isolation
  • biosynthesis
  • drug effect
  • gene expression regulation
  • genetics
  • metabolism
  • pancreas islet
  • Cytokines
  • Gene Expression Regulation
  • Glucose
  • Humans
  • Insulin
  • Islets of Langerhans
  • MicroRNAs
  • Palmitic Acid
  • Polypyrimidine Tract-Binding Protein
  • RNA Precursors
  • RNA, Messenger
  • MULTIDISCIPLINARY
  • MESSENGER-RNA STABILITY
  • HUMAN PANCREATIC-ISLETS
  • BETA-CELL APOPTOSIS
  • GENE-EXPRESSION
  • 3'-UNTRANSLATED REGION
  • CHRONIC EXPOSURE
  • RIN-5F CELLS
  • FATTY-ACIDS
  • TRANSLATION
  • MICRORNAS
  • Hyperglycemia
  • Diabetes Mellitus, Non-Insulin-Dependent
  • Brain Death
  • Cytology - Animal
  • Cytology - Human
  • Genetics - General
  • Genetics - Human
  • Biochemistry studies - Nucleic acids, purines and pyrimidines
  • Biochemistry studies - Proteins, peptides and amino acids
  • Biochemistry studies - Carbohydrates
  • Metabolism - General metabolism and metabolic pathways
  • Metabolism - Metabolic disorders
  • Endocrine - General
  • Endocrine - Pancreas
  • Nervous system - Pathology
  • sodium palmitate
  • Animals, Chordates, Humans, Mammals, Primates, Vertebrates

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