Sco2 deficient mice develop increased adiposity and insulin resistance

Area of Science:

• Mitochondrial biology
• Metabolic disorders
• Genetics

Background:

• Cytochrome c oxidase (COX) complex IV is crucial for mitochondrial respiration.
• Mutations in COX assembly genes cause severe human metabolic disorders.
• Surf1-/- mice exhibit beneficial metabolic phenotypes despite reduced COX activity.

Purpose of the Study:

• To investigate if reduced COX activity from different mutations leads to similar metabolic changes.
• To compare the molecular and physiological effects of Surf1 and Sco2 mutations on metabolism.

Main Methods:

• Generation and analysis of Sco2 knock-in/knock-out (KI/KO) mice with reduced COX activity.
• Assessment of metabolic parameters including insulin sensitivity, fat mass, glucose uptake, and lipid profiles.
• Evaluation of mitochondrial function, including COX activity, oxygen consumption, and UPRmt pathway activation.

Main Results:

• Sco2 KI/KO mice display increased fat mass, insulin resistance, and hepatosteatosis, contrasting with Surf1-/- mice.
• Reduced COX activity in Sco2 KI/KO mice is associated with decreased beta-oxidation and impaired mitochondrial function in adipose tissue.
• Sco2 KI/KO mice do not upregulate the mitochondrial unfolded protein response (UPRmt), unlike Surf1-/- mice.

Conclusions:

• The metabolic consequences of COX dysfunction are mutation-specific, not solely dependent on reduced COX activity levels.
• Sco2 mutations lead to detrimental metabolic changes, highlighting a distinct role for Complex IV in metabolic regulation.
• Mitochondrial dysfunction has complex and varied impacts on physiology, underscoring the need for precise understanding of specific genetic defects.