title: Altering β-cell number through stable alteration of miR-21 and miR-34a expression.
abstract: OBJECTIVE
  An insufficient functional β-cell mass is a prerequisite to develop diabetes. Thus, means to protect or restore β-cell mass are important goals in diabetes research. Inflammation and proinflammatory cytokines play important roles in β-cell dysfunction and death, and recent data show that 2 miRNAs, miR-21 and miR-34a, may be involved in mediating cytokine-induced β-cell dysfunction. Therefore, manipulation of miR-21 and miR-34a levels may potentially be beneficial to β cells. To study the effect of long-term alterations of miR-21 or miR-34a levels upon net β-cell number, we stably overexpressed miR-21 and knocked down miR-34a, and investigated essential cellular processes.
  
  
  METHODS
  miRNA expression was manipulated using Lentiviral transduction of the β-cell line INS-1. Stable cell lines were generated, and cell death, NO synthesis, proliferation, and total cell number were monitored in the absence or presence of cytokines.
  
  
  RESULTS
  Overexpression of miR-21 decreased net β-cell number in the absence of cytokines, and increased apoptosis and NO synthesis in the absence and presence of cytokines. Proliferation was increased upon miR-21 overexpression. Knockdown of miR-34a increased net β-cell number in the absence of cytokines, and reduced apoptosis and NO synthesis in the absence and presence of cytokines. Proliferation was decreased upon miR-34a knockdown.
  
  
  CONCLUSIONS
  As overexpression of miR-21 increased proliferation, but also apoptosis and NO synthesis, the potential of miR-21 as a therapeutic agent to increase β-cell survival is doubtful. Knockdown of miR-34a slightly decreased proliferation, but as apoptosis and NO synthesis were highly reduced, miR-34a may be further investigated as a therapeutic target to reduce β-cell death and dysfunction.
authors.affiliation: a Section of Endocrinological Research; Department of Biomedical Sciences; Faculty of Health Sciences; University of Copenhagen; Copenhagen, Denmark.
authors.forename: Marie Balslev
authors.initials: MB
authors.lastname: Backe
authors.forename: Guy Wayne
authors.initials: GW
authors.lastname: Novotny
authors.forename: Dan Ploug
authors.initials: DP
authors.lastname: Christensen
authors.forename: Lars Groth
authors.initials: LG
authors.lastname: Grunnet
authors.forename: Thomas
authors.initials: T
authors.lastname: Mandrup-Poulsen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D002452:Cell Count; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D009569:Nitric Oxide / Q000378:metabolism; D051381:Rats; D014162:Transfection
chemical_list: D016207:Cytokines; C560944:MIRN34 microRNA, rat; D035683:MicroRNAs; C546082:mirn21 microRNA, rat; D009569:Nitric Oxide
keywords: apoptosis; cytokines; diabetes mellitus; micro RNA; proliferation