Beneficial Effect of Ursodeoxycholic Acid in Patients with ACOX2 Deficiency-Associated Hypertransaminasemia
Marta Alonso-Peña 1 2 , Ricardo Espinosa-Escudero 1 , Elisa Herraez 1 3 , Oscar Briz 1 3 , Maria Luisa Cagigal 4 , Jesus M Gonzalez-Santiago 5 , Aida Ortega-Alonso 6 , Conrado Fernandez Rodriguez 7 , Luis Bujanda 8 3 , Marta Calvo Sanchez 9 , Delia D Avola 10 , Maria-Carlota Londoño 11 3 , Moises Diago 12 , Jose C Fernandez-Checa 13 14 3 , Carmen Garcia-Ruiz 13 14 3 , Raul J Andrade 6 3 , Frank Lammert 15 16 , Jesus Prieto 10 3 , Javier Crespo 2 , Javier Juamperez 17 , Alvaro Diaz-Gonzalez 2 , Maria J Monte 1 3 , Jose J G Marin 1 3
Background: A variant (p.Arg225Trp) of peroxisomal acyl-CoA oxidase 2 (ACOX2), involved in bile acid (BA) side-chain shortening, has been associated with unexplained persistent hypertransaminasemia and accumulation of C27-BAs, mainly trihydroxycholestanoic acid (THCA).
Aims: To investigate the prevalence of ACOX2 deficiency-associated hypertransaminasemia (ADAH), its response to ursodeoxycholic acid (UDCA), elucidate its pathophysiological mechanism and identify other inborn errors that could cause this alteration.
Methods & results: Among 33 patients with unexplained hypertransaminasemia from 11 hospitals, and 13 of their relatives, 7 individuals with abnormally high C27-BA levels (>50% of total BAs) were identified by HPLC-MS/MS. The p.Arg225Trp variant was found in homozygosity (exon amplification/sequencing) in 2 patients and 3 family members.
Two additional non-related patients were heterozygous carriers of different alleles: c.673C>T (p.Arg225Trp) and c.456_459del (p.Thr154fs). In ADAH patients, impaired liver expression of ACOX2, but not ACOX3, was found (immunohistochemistry).
Treatment with UDCA normalized transaminases levels. Incubation of HuH-7 liver cells with THCA, which was efficiently taken up, but not through BA transporters, increased ROS production (flow cytometry), ER stress biomarkers (GRP78, CHOP and XBP1-S/XBP1-U ratio), and BAXα expression (RT-qPCR and immunoblot), whereas cell viability was decreased (MTT). THCA-induced cell toxicity was higher than that of major C24-BAs and was not prevented by UDCA.
Fourteen predicted ACOX2 variants were generated (site-directed mutagenesis) and expressed in HuH-7 cells. Functional tests to determine their ability to metabolize THCA identified six with the potential to cause ADAH.
Conclusion: Dysfunctional ACOX2 has been found in several patients with unexplained hypertransaminasemia. This condition can be accurately identified by a non-invasive diagnostic strategy based on plasma BA profiling and ACOX2 sequencing. Moreover, UDCA treatment can efficiently attenuate liver damage in these patients.