Measuring Mitochondrial Function: From Organelle to Organism.

Area of Science:

• Biochemistry and Molecular Biology
• Physiology
• Medical Research

Background:

• Mitochondrial energy production is vital for cellular function and overall health.
• Deficits in mitochondrial function are linked to various diseases, including cardiovascular, cardiopulmonary, diabetes, and metabolic syndrome.
• Current methods often measure maximal oxidative capacity, which may not reflect physiological conditions.

Purpose of the Study:

• To outline methods for delineating mitochondrial function through ATP production and oxygen consumption measurements.
• To propose a new paradigm focusing on submaximal mitochondrial fluxes and ADP sensitivity.
• To establish ADP sensitivity as a key indicator of mitochondria's role in ATP homeostasis.

Main Methods:

• Quantifying aerobic ATP production using phosphorus magnetic resonance spectroscopy (³¹PMRS) in vivo.
• Measuring mitochondrial oxygen consumption via oxygen polarography in isolated mitochondria, cultured cells, and permeabilized fibers.
• Employing graded levels of ADP to assess submaximal mitochondrial fluxes and ADP sensitivity.

Main Results:

• The study outlines the logic and execution of two primary measurement classes for mitochondrial function.
• A focus on submaximal fluxes and ADP sensitivity is proposed as a more physiologically relevant approach.
• This approach maps mitochondrial function in relation to cellular energy demands.

Conclusions:

• Mitochondrial ADP sensitivity is proposed as a critical function for sensing and matching cellular ATP demands.
• Deficits in this mitochondrial sensing role contribute to pathologies seen in metabolic and cardiovascular diseases.
• The described measurement strategies provide a framework for assessing mitochondrial bioenergetics in health and disease.