title: Localization of lipoprotein lipase and GPIHBP1 in mouse pancreas: effects of diet and leptin deficiency.
abstract: BACKGROUND
  Lipoprotein lipase (LPL) hydrolyzes triglycerides in plasma lipoproteins and enables uptake of lipolysis products for energy production or storage in tissues. Our aim was to study the localization of LPL and its endothelial anchoring protein glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) in mouse pancreas, and effects of diet and leptin deficiency on their expression patterns. For this, immunofluorescence microscopy was used on pancreatic tissue from C57BL/6 mouse embryos (E18), adult mice on normal or high-fat diet, and adult ob/ob-mice treated or not with leptin. The distribution of LPL and GPIHBP1 was compared to insulin, glucagon and CD31. Heparin injections were used to discriminate between intracellular and extracellular LPL.
  
  
  RESULTS
  In the exocrine pancreas LPL was found in capillaries, and was mostly co-localized with GPIHBP1. LPL was releasable by heparin, indicating localization on cell surfaces. Within the islets, most of the LPL was associated with beta cells and could not be released by heparin, indicating that the enzyme remained mostly within cells. Staining for LPL was found also in the glucagon-producing alpha cells, both in embryos (E18) and in adult mice. Only small amounts of LPL were found together with GPIHBP1 within the capillaries of islets. Neither a high fat diet nor fasting/re-feeding markedly altered the distribution pattern of LPL or GPIHBP1 in mouse pancreas. Islets from ob/ob mice appeared completely deficient of LPL in the beta cells, while LPL-staining was normal in alpha cells and in the exocrine pancreas. Leptin treatment of ob/ob mice for 12 days reversed this pattern, so that most of the islets expressed LPL in beta cells.
  
  
  CONCLUSIONS
  We conclude that both LPL and GPIHBP1 are present in mouse pancreas, and that LPL expression in beta cells is dependent on leptin.
authors.affiliation: Department of Medical Biosciences/Physiological Chemistry, Umeå University, Umeå, Sweden.
authors.forename: Rakel
authors.initials: R
authors.lastname: Nyrén
authors.forename: Chuchun L
authors.initials: CL
authors.lastname: Chang
authors.forename: Per
authors.initials: P
authors.lastname: Lindström
authors.forename: Anastasia
authors.initials: A
authors.lastname: Barmina
authors.forename: Evelina
authors.initials: E
authors.lastname: Vorrsjö
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Ali
authors.forename: Lisa
authors.initials: L
authors.lastname: Juntti-Berggren
authors.forename: André
authors.initials: A
authors.lastname: Bensadoun
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Young
authors.forename: Thomas
authors.initials: T
authors.lastname: Olivecrona
authors.forename: Gunilla
authors.initials: G
authors.lastname: Olivecrona
mesh_terms: D000818:Animals; D002196:Capillaries / Q000378:metabolism; D059305:Diet, High-Fat / Q000379:methods; D042783:Endothelial Cells / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D050416:Glucagon-Secreting Cells / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006493:Heparin / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism; D020738:Leptin / Q000172:deficiency* / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010179:Pancreas / Q000378:metabolism*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D018110:Receptors, Lipoprotein / Q000378:metabolism*
chemical_list: C472779:GPI-HBP1 protein, mouse; D017261:Glycosylphosphatidylinositols; D007328:Insulin; D020738:Leptin; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D018110:Receptors, Lipoprotein; D006493:Heparin; D005934:Glucagon; D008071:Lipoprotein Lipase