FEBS Letters
Volume 579, Issue 14 , Pages 3183-3189, 6 June 2005

Microsomal triglyceride transfer protein expression in adipocytes: A new component in fat metabolism

Edited by Felix Weiland

  • Larry L. Swift

      Affiliations

    • Department of Pathology, C-3321 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
    • Corresponding Author InformationCorresponding author. Fax: +1 615 343 7023
  • ,
  • Bharati Kakkad

      Affiliations

    • Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
  • ,
  • Cordelia Boone

      Affiliations

    • Department of Pathology, C-3321 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
  • ,
  • Aneta Jovanovska

      Affiliations

    • Department of Pathology, C-3321 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
  • ,
  • W. Gray Jerome

      Affiliations

    • Department of Pathology, C-3321 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
  • ,
  • Peter J. Mohler

      Affiliations

    • Department of Pathology, C-3321 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA
  • ,
  • David E. Ong

      Affiliations

    • Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-2561, USA

Received 10 February 2005; received in revised form 29 April 2005; accepted 9 May 2005. published online 23 May 2005.

Abstract 

Microsomal triglyceride transfer protein (MTP) is a carrier of triglyceride essential for the assembly of apolipoprotein (apo)B-containing lipoproteins by the liver and the small intestine. Its role in triglyceride transfer in tissues that do not secrete lipoproteins has not been explored. In particular, MTP would seem to be a candidate for a role in triglyceride metabolism within the adipocyte. To test this hypothesis, we probed adipocytes for the presence of MTP. Immunohistochemical and biochemical studies demonstrate MTP in adipocytes from brown and white fat depots of mice and human, as well as in 3T3-L1 cells. Confocal microscopy revealed MTP throughout 3T3 cells; however, MTP fluorescence was prominent in juxtanuclear areas. In differentiated 3T3 cells MTP fluorescence was very striking around lipid droplets. In vitro lipid transfer assays demonstrated the presence of triglyceride transfer activity within microsomal fractions isolated from rat adipose tissue. In addition, quantitative rtPCR studies showed that MTP expression in mouse white fat depots was approximately 1% of MTP expression in mouse liver. MTP mRNA in differentiated 3T3 cells was approximately 13% of liver expression. Our results provide unequivocal evidence for the presence of MTP in adipocytes and present new possibilities for defining the mechanisms by which triglyceride is stored and/or hydrolyzed and mobilized.

Abbreviations: MTP, microsomal triglyceride transfer protein, HSL, hormone sensitive lipase, apoB, apolipoprotein B, VLDL, very low density lipoproteins, CM, chylomicrons

Keywords: Lipid transport, Immunohistochemistry, Differentiation, Golgi apparatus, Endoplasmic reticulum, Confocal microscopy, 3T3-L1 cells

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PII: S0014-5793(05)00584-3

doi:10.1016/j.febslet.2005.05.009

FEBS Letters
Volume 579, Issue 14 , Pages 3183-3189, 6 June 2005