Warburg-like effect is a hallmark of complex I assembly defects

Area of Science:

• Biochemistry
• Cell Biology
• Mitochondrial Medicine

Background:

• Mitochondrial Complex I (CI) is vital for cellular energy production (ATP synthesis) and NADH oxidation.
• The assembly of CI, involving nuclear and mtDNA-encoded subunits, is crucial for its function.
• The metabolic consequences of CI assembly defects versus functional defects are not well understood.

Purpose of the Study:

• To investigate the relationship between CI structure, function, and cellular metabolism in patients with CI deficiency.
• To differentiate metabolic adaptations in CI assembly defects versus CI functional defects.
• To elucidate the mechanisms underlying metabolic reprogramming in CI deficiency.

Main Methods:

• Analysis of patient fibroblasts (n=29) representing various CI mitochondrial diseases.
• Assessment of CI function, structure, and cellular metabolic profiles.
• Investigation of reactive oxygen species (ROS) production and AMPK signaling pathways.

Main Results:

• CI deficiency does not always induce a glycolytic switch (Warburg effect); this is specific to CI assembly defects.
• Functional CI defects without disassembly promote higher catabolism to support oxidative metabolism.
• ROS overproduction by CI assembly intermediates and AMPK-dependent Pyruvate Dehydrogenase inactivation mediate metabolic reprogramming.

Conclusions:

• A two-way model of metabolic responses to CI deficiency is proposed, distinguishing between assembly defects and functional defects.
• Understanding these distinct metabolic pathways is critical for developing targeted therapeutic strategies for mitochondrial diseases.
• This research sheds light on metabolic adaptations in various pathophysiological conditions involving CI dysfunction.