Transintestinal cholesterol excretion is an active metabolic process modulated by PCSK9 and statin involving ABCB1

Arterioscler Thromb Vasc Biol. 2013 Jul;33(7):1484-93. doi: 10.1161/ATVBAHA.112.300263. Epub 2013 Apr 4.

Abstract

Objective: Transintestinal cholesterol excretion (TICE) is an alternate pathway to hepatobiliary secretion. Our study aimed at identifying molecular mechanisms of TICE.

Approach and results: We studied TICE ex vivo in mouse and human intestinal explants, and in vivo after bile diversion and intestinal cannulation in mice. We provide the first evidence that both low-density lipoprotein (LDL) and high-density lipoprotein deliver cholesterol for TICE in human and mouse jejunal explants at the basolateral side. Proprotein convertase subtilisin kexin type 9 (PCSK9)(-/-) mice and intestinal explants show increased LDL-TICE, and acute injection of PCSK9 decreases TICE in vivo, suggesting that PCSK9 is a repressor of TICE. The acute repression was dependent on the LDL receptor (LDLR). Further, TICE was increased when mice were treated with lovastatin. These data point to an important role for LDLR in TICE. However, LDLR(-/-) mice showed increased intestinal LDL uptake, contrary to what is observed in the liver, and tended to have higher TICE. We interpret these data to suggest that there might be at least 2 mechanisms contributing to TICE; 1 involving LDL receptors and other unidentified mechanisms. Acute modulation of LDLR affects TICE, but chronic deficiency is compensated for most likely by the upregulation of the unknown mechanisms. Using mice deficient for apical multidrug active transporter ATP-binding cassette transporter B1 a and b, and its inhibitor, we show that these apical transporters contribute significantly to TICE.

Conclusions: TICE is operative in human jejunal explants. It is a metabolically active process that can be acutely regulated, inversely related to cholesterolemia, and pharmacologically activated by statins.

Keywords: ATP-binding cassette transporter B1; PCSK9; lipoprotein; low-density lipoprotein receptor; transintestinal cholesterol excretion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / deficiency
  • ATP Binding Cassette Transporter, Subfamily B / genetics
  • ATP Binding Cassette Transporter, Subfamily B / metabolism*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / deficiency
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Animals
  • Biopsy
  • Cholesterol / metabolism*
  • Cholesterol, HDL / metabolism
  • Cholesterol, LDL / metabolism
  • Humans
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / pharmacology*
  • Jejunum / drug effects*
  • Jejunum / enzymology
  • Lovastatin / pharmacology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Proprotein Convertase 9
  • Proprotein Convertases / deficiency
  • Proprotein Convertases / genetics
  • Proprotein Convertases / metabolism*
  • Receptors, LDL / genetics
  • Receptors, LDL / metabolism
  • Recombinant Proteins / metabolism
  • Serine Endopeptidases / deficiency
  • Serine Endopeptidases / genetics
  • Serine Endopeptidases / metabolism*
  • Time Factors

Substances

  • ABCB1 protein, human
  • ATP Binding Cassette Transporter, Subfamily B
  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors
  • Receptors, LDL
  • Recombinant Proteins
  • Cholesterol
  • multidrug resistance protein 3
  • Lovastatin
  • PCSK9 protein, human
  • Pcsk9 protein, mouse
  • Proprotein Convertase 9
  • Proprotein Convertases
  • Serine Endopeptidases
  • Abcb1b protein, mouse