PhD Scientific Days 2023

Pathology - Posters C

Supraphysiological Concentrations of Choline Oxidized in Mitochondria Support the Forward Operation of Adenine Nucleotide Translocase When Complex I is Inhibited

Text of the abstract

Introduction
The oxidation of choline to betaine aldehyde leads to the transfer of electrons to ubiquinone in mitochondria that express choline dehydrogenase (Cdh). This electron transfer supports complexes III and IV, thus generating the protonmotive force. Further catabolism of betaine aldehyde depends on CI activity due to NAD+ requirement.

Aims
Our aim was to investigate the effect of the choline catabolism on the mitochondrial membrane potential and its effect on the ANT and F1Fo-ATPase directionality in isolated mouse liver mitochondria

Method
In complex I-inhibited, mouse liver mitochondria, the directionalities of adenine nucleotide translocase (ANT) and F1Fo-ATPase were estimated by the instantaneous effect of their respective inhibitors, carboxyatractyloside vs oligomycin, on membrane potential. In addition, matrix NADH levels were also recorded.

Results
Choline, at concentrations higher than those reported in physiological contexts in the literature, generated a sufficiently high mitochondrial membrane potential to sustain ANT operation in the forward mode in CI-inhibited mouse liver mitochondria. This was not observed when either CIII or CIV were inhibited. The directionality of the F1Fo-ATPase was unaffected by choline catabolism.

Conclusion
The data show that Cdh-mediated choline catabolism could generate sufficient CIII and CIV proton pumping, thus supporting ANT operation in forward mode even under CI inhibition, but only if used at supraphysiological levels.