title: A novel mechanism regulating insulin secretion involving Herpud1 in mice.
abstract: OBJECTIVE
  Type 2 diabetes results from beta cell dysfunction after prolonged physiological stress, which causes oversecretion of insulin. We recently found that insulin hypersecretion is mediated by at least two genes. Among mouse models of type 2 diabetes, the DBA/2 mouse strain is more susceptible to diabetes than is the C57BL/6J (B6J) strain. One distinctive feature of the DBA/2 mouse is that it hypersecretes insulin, independent of changes in insulin sensitivity; we identified Nnt as a gene responsible for this trait.
  
  
  METHODS
  To identify the other gene(s) affecting insulin hypersecretion, we tested a panel of recombinant inbred BXD strains, which have different combinations of B6 and DBA/2 alleles.
  
  
  RESULTS
  We found that 25% of the BXD strains hypersecreted insulin in response to glucose. Microarray profiling of islets from high- and low-secretor strains showed that at least four genes were differentially expressed. One gene was consistently underexpressed in islets from both DBA/2 and the high-secretor BXD strains. This gene (Herpud1 or Herp) encodes the 54 kDa endoplasmic reticulum stress-inducible protein (HERP) that resides in the integral endoplasmic reticulum membrane. To test directly whether Herpud1 can interact with Nnt, Herpud1 was either knocked down or overexpressed in MIN6 cells. These results showed that when Herpud1 was suppressed, Nnt expression was reduced, while overexpression of Herpud1 led to increased Nnt expression. Furthermore, Herpud1 suppression resulted in significantly decreased glucose-stimulated insulin secretion in the DBA/2 islets but not B6J islets.
  
  
  CONCLUSIONS
  We conclude that Herpud1 regulates insulin secretion via control of Nnt expression.
authors.affiliation: Department of Medicine (Austin Health), Austin Hospital, University of Melbourne, Heidelberg Heights, Melbourne, Victoria, 3084, Australia. wongn@unimelb.edu.au
authors.forename: N
authors.initials: N
authors.lastname: Wong
authors.forename: G
authors.initials: G
authors.lastname: Morahan
authors.forename: M
authors.initials: M
authors.lastname: Stathopoulos
authors.forename: J
authors.initials: J
authors.lastname: Proietto
authors.forename: S
authors.initials: S
authors.lastname: Andrikopoulos
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D007328:Insulin; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D061087:NADP Transhydrogenase, AB-Specific / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: C415829:Herpud1 protein, mouse; D007328:Insulin; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D061087:NADP Transhydrogenase, AB-Specific; C556048:Nnt protein, mouse