Koichi Sato1, Fumikazu Okajima1, Kazuya Miyashita2, Shigeyuki Imamura3, Junji Kobayashi4, Kimber L Stanhope5, Peter J Havel5, Tetsuo Machida6, Hiroyuki Sumino6, Masami Murakami6, Ernst Schaefer7, Katsuyuki Nakajima8. 1. Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan. 2. Immuno-Biological Laboratories, Fujioka, Gunma, Japan. 3. Imamura Enzyme Technology Laboratory, Shizuoka, Japan. 4. Department of General Medicine, Kanazawa Medical University, Ishikawa, Japan. 5. Department of Molecular Biosciences, School of Veterinary Medicine, Department of Nutrition, University of California, Davis, CA, USA. 6. Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan. 7. Lipid Metabolism Laboratory, Human Nutrition Research Center on Aging, Tufts University, Tufts University School of Medicine, Boston, MA, United States. 8. 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.
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.
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: Julio Alejandro Lamprea-Montealegre; Natalie Staplin; William G Herrington; Richard Haynes; Jonathan Emberson; Colin Baigent; Ian H de Boer Journal: Clin J Am Soc Nephrol Date: 2019-12-12 Impact factor: 8.237
Authors: Anne P Beigneux; Christopher M Allan; Norma P Sandoval; Geoffrey W Cho; Patrick J Heizer; Rachel S Jung; Kimber L Stanhope; Peter J Havel; Gabriel Birrane; Muthuraman Meiyappan; John E Gill; Masami Murakami; Kazuya Miyashita; Katsuyuki Nakajima; Michael Ploug; Loren G Fong; Stephen G Young Journal: Proc Natl Acad Sci U S A Date: 2019-03-08 Impact factor: 11.205