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High glucose suppresses human islet insulin biosynthesis by inducing miR-133a leading to decreased polypyrimidine tract binding protein-expression
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
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2010 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 5, no 5, e10843- p.Article in journal (Refereed) Published
Abstract [en]


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.


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-1beta 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.


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.

Place, publisher, year, edition, pages
2010. Vol. 5, no 5, e10843- p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-130038DOI: 10.1371/journal.pone.0010843ISI: 000278221500029PubMedID: 20520763OAI: oai:DiVA.org:uu-130038DiVA: diva2:345961
Available from: 2010-08-29 Created: 2010-08-29 Last updated: 2014-10-29Bibliographically approved
In thesis
1. The Role of RNA Binding Proteins in Insulin Messenger Stability and Translation
Open this publication in new window or tab >>The Role of RNA Binding Proteins in Insulin Messenger Stability and Translation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the reason for insufficient release of insulin in diabetes mellitus may vary depending on the type and stage of the disease, it is of vital importance that an amplified insulin biosynthesis can meet the increased need during periods of hyperglycemia. The insulin mRNA is highly abundant in beta cells and changes in insulin mRNA levels are, at least in part, controlled by altered rates of mRNA degradation. Since the mechanisms behind the control of insulin messenger stability and translation are still largely obscure, the work presented in this thesis therefore aimed to further investigate the role of insulin mRNA binding proteins in the control of insulin mRNA break-down and utilization for insulin biosynthesis.

To clarify how glucose regulates insulin mRNA stability and translation we studied the correlation between polypyrimidine tract binding protein (PTB) gene expression and insulin mRNA levels. It was found that an increase in PTB mRNA and protein levels is paralleled by an increase in insulin mRNA levels. It was also found that PTB binds to the 5’-untranslated region of the insulin mRNA and that insulin mRNA can be translated through a cap-independent mechanism in human islets of Langerhans, possibly due to the interaction with PTB. Further it was discovered that the suppressed insulin biosynthesis in human islets during glucotoxicity is partly due to an induction of the microRNA miR-133a. This induction leads to decreased levels of PTB and insulin biosynthesis rates in human islets. Finally, we were able to identify two proteins, hnRNP U and TIAR, that bind specifically to the insulin mRNA in vitro, and show that the stability and translation of insulin mRNA is oppositely affected by these proteins.

In conclusion, insulin producing cells seem to be able to regulate insulin messenger stability and translation by a control mechanism in which the binding of specific proteins to the insulin messenger dictates the outcome. A better understanding of the events leading to insulin production may in the future aid in optimal diagnosis and treatment of type 2 diabetes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 44 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 596
National Category
Cell and Molecular Biology
Research subject
Medical Cell Biology
urn:nbn:se:uu:diva-130234 (URN)978-91-554-7885-8 (ISBN)
Public defence
2010-10-15, B22, BMC, Husargatan 3, Uppsala, 13:15 (English)
Available from: 2010-09-23 Created: 2010-09-05 Last updated: 2011-03-04

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