title: The majority of lipoprotein lipase in plasma is bound to remnant lipoproteins: A new definition of remnant lipoproteins.
abstract: BACKGROUND
  Lipoprotein lipase (LPL) is a multifunctional protein and a key enzyme involved in the regulation of lipoprotein metabolism. We determined the lipoproteins to which LPL is bound in the pre-heparin and post-heparin plasma.
  
  
  METHODS
  Tetrahydrolipstatin (THL), a potent inhibitor of serine lipases, was used to block the lipolytic activity of LPL, thereby preventing changes in the plasma lipoproteins due to ex vivo lipolysis. Gel filtration was performed to obtain the LPL elution profiles in plasma and the isolated remnant lipoproteins (RLP).
  
  
  RESULTS
  When ex vivo lipolytic activity was inhibited by THL in the post-heparin plasma, majority of the LPL was found in the VLDL elution range, specifically in the RLP as inactive dimers. However, in the absence of THL, most of the LPL was found in the HDL elution range as active dimers. Furthermore, majority of the LPL in the pre-heparin plasma was found in the RLP as inactive form, with broadly diffused lipoprotein profiles in the presence and absence of THL.
  
  
  CONCLUSIONS
  It is suggested that during lipolysis in vivo, the endothelial bound LPL dimers generates RLP, forming circulating RLP-LPL complexes in an inactive form that subsequently binds and initiates receptor-mediated catabolism.
authors.affiliation: Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Sato
authors.affiliation: Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Okajima
authors.affiliation: Immuno-Biological Laboratories, Fujioka, Gunma, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Miyashita
authors.affiliation: Imamura Enzyme Technology Laboratory, Shizuoka, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Imamura
authors.affiliation: Department of General Medicine, Kanazawa Medical University, Ishikawa, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Kobayashi
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, Department of Nutrition, University of California, Davis, CA, USA.
authors.forename: Kimber L
authors.initials: KL
authors.lastname: Stanhope
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, Department of Nutrition, University of California, Davis, CA, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Havel
authors.affiliation: Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Machida
authors.affiliation: Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sumino
authors.affiliation: Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Lipid Metabolism Laboratory, Human Nutrition Research Center on Aging, Tufts University, Tufts University School of Medicine, Boston, MA, United States.
authors.forename: Ernst
authors.initials: E
authors.lastname: Schaefer
authors.affiliation: Department of General Medicine, Kanazawa Medical University, Ishikawa, Japan; Department of Molecular Biosciences, School of Veterinary Medicine, Department of Nutrition, University of California, Davis, CA, USA; Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan; Lipid Metabolism Laboratory, Human Nutrition Research Center on Aging, Tufts University, Tufts University School of Medicine, Boston, MA, United States. Electronic address: nakajimak05@ybb.ne.jp.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Nakajima
mesh_terms: D000328:Adult; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D005260:Female; D006801:Humans; D007783:Lactones / Q000494:pharmacology; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors / Q000097:blood* / Q000378:metabolism*; D008074:Lipoproteins / Q000097:blood* / Q000302:isolation & purification / Q000378:metabolism*; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood; D008875:Middle Aged; D000077403:Orlistat; D055815:Young Adult
chemical_list: D007783:Lactones; D008074:Lipoproteins; D000077403:Orlistat; D008071:Lipoprotein Lipase
keywords: Chylomicron remnants (CM-R); Lipoprotein lipase (LPL); Remnant-like lipoprotein particles-cholesterol (RLP-C); Tetrahydrolipstatin (THL); Very low density lipoprotein remnants (VLDL-R)