PhD Scientific Days 2024

Poster Session A - Molecular Medicine 1.

Significant mitochondrial malfuntions in KGDH double-heterozygous KO mice are associated with minor behavioural and metabolic abnormalities but decreased tolerance to forced movement

Text of the abstract

Introduction: α-ketoglutarate dehydrogenase complex (αKGDHc, or oxoglutarate dehydrogenase complex) is the rate limiting enzyme in the tricarboxylic acid (TCA) cycle catalysing the oxidative decarboxilation of the α-ketoglutarate, while producing NADH for oxidative phosphorylation and succinyl-CoA for the substrate level phosphorylation (SLP); thus, being a crucial point in the mitochondrial ATP production. Additionally, αKGDHc is a major producer of reactive oxygen species (ROS). The complex is built up by three types of subunits: α-KGDH (E1), dihydrolipoyl succinyltransferase (E2), and dihydrolipoyl dehydrogenase (E3).
Aims: E2 and E3 heterozygous knock-out (DKO) male middle-aged (200-250 day old) mice have been used to examine the in vitro and in vivo effects of this mutation. Of note, homozygous KO mice die in utero emphasizing the important role of αKGDHc in oxidative metabolism.
Methods: The mRNA levels of mitochondrial enzymes were determined from liver samples. Histological studies were carried out on skeletal muscle samples. Mitochondria isolated from brain and kidneys were used to measure mitochondrial ATP production, oxygen consumption, ROS generation and aconitase activity. In vivo experiments included metabolic experiments in metabolic cage, behavioural tests and endurance test.
Result: Our in vitro results show that in DKO animals both oxygen consumption and ATP production were decreased with α-ketoglutarate as substrate compared to the WT animals. DKO mice produced less ROS during succinate-induced reverse electron transfer (RET). In line with that, higher aconitase activity was measured in DKO brain mitochondria. In the in vivo metabolic experiments, there were some trends and also in the behavioural tests, small differences were detectable between the two groups indicating a minor metabolic and cognitive decline. Importantly, DKO animals showed a decreased performance in the trademill fatigue test, which could not be explained by fibrotic alterations in the skeletal muscle.
Conclusion: Taken together, these data show that heterozygous DKO mice have significant in vitro changes compared to the WT animals, which is not reflected in significant differences in the phenotype. This is the first study analysing the phenotype of the αKGDHc DKO mice.
Funding: EFOP-3.6.3-VEKOP-16-2017-00009