Studying Systemic Metabolic Remodeling and Abnormal Mitochondrial Signaling in Primary Biliary Cholangitis

• Author / Creator

  Sun, Ning

• Primary biliary cholangitis (PBC) is linked with the production of anti-mitochondrial antibodies (AMA) targeting pyruvate dehydrogenase complex-E2 subunit (PDC-E2). Cholangiocytes from PBC patients express increased PDC-E2, which is thought to result in loss of tolerance to mitochondrial proteins. We have previously shown that a human betaretrovirus resembling mouse mammary tumor virus (MMTV), leads to increased expression of PDC-E2 in cholangiocytes. To better understand these changes, we have studied the metabolism in PBC cholangiocytes and found evidence of increased glycolysis linked with altered mitochondrial function, as well as increased mitochondrial DNA and proteins in cholangiocytes from patients with PBC.

  Herein, we addressed the hypothesis that a glycolytic-shift and metabolic remodeling occurs systemically both in cholangiocytes and the peripheral blood of PBC, which in turn leads to an increased PDC-E2 expression linked with mitochondrial biogenesis. We first used immunofluorescence to investigate whether HIF1 α pathway activation was involved in metabolic remodeling of cholangiocytes. Then, we used RNA-seq to compare transcriptomic changes in PBC patients’ whole blood versus healthy controls to gain a wider perspective of the systemic changes in PBC patients’ metabolism. Specifically, we focused on evaluating the mitochondrial-DNA replication and mitochondrial function by using quantitative PCR, flow cytometry, and immunocytochemistry.

  We found specific biliary epithelium cells from PBC patients’ were characterized by activated HIF1 α signalling that was not observed in other liver diseases. We also found that the peripheral blood of PBC showed increased glycolytic metabolism with an upregulated mitochondrial encoded OXPHOS gene expression and a downregulated nuclear encoded gene expression as compared to healthy subjects. These changes of gene expression were accompanied by increased mt-DNA replication and hyperpolarized mitochondria in PBC peripheral blood. Finally, the overexpression of the mitochondrial autoantigen PDC-E2 was predominantly observed with hyperpolarized mitochondria in PBMC of patients with PBC. These findings support the hypothesis that the abnormal mitochondrial signalling characterized by hyperpolarized mitochondria induces a compensatory mitochondrial biogenesis linked with the overexpression of mitochondrial autoantigens in PBC.

• Subjects / Keywords

  • Primary biliary cholangitis
  • Metabolic remodeling
  • Mitochondrial autoantigen

• Graduation date

  Fall 2024

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-b06d-hr73

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.