Overview of methods that determine mitochondrial function in human disease

Abstract

Cellular metabolism has a key role in the pathogenesis of human disease. Mitochondria are the organelles that generate most of the energy needed for a cell to function and drive cellular metabolism. Understanding the link between metabolic and mitochondrial function can be challenging due to the variation in methods used to measure mitochondrial function and heterogeneity in mitochondria, cells, tissues, and end organs. Mitochondrial dysfunction can be determined at both the cellular and tissue levels using several methods, such as assessment of cellular bioenergetics, levels of mitochondrial DNA (mtDNA), mitochondrial membrane potential (MMP), mitochondrial reactive oxygen species (mito-ROS), and levels of mitochondrial enzymes. Recent advances involving novel radiotracers in combination with PET imaging have allowed for the determination of mitochondrial function in vivo with high specificity. Understanding the barriers in existing methodologies used to study mitochondrial function may help further establish the assessment of mitochondrial function as a biologically and clinically relevant biomarker for human disease severity and prognosis. Herein, we critically review the existing literature regarding the strengths and limitations of methods that determine mitochondrial function, and we subsequently discuss how emerging research methods have begun to overcome some of these hurdles. We conclude that a combination of techniques, including respirometry and mitochondrial membrane potential assessment, is necessary to understand the complexity and biological and clinical relevance of mitochondrial function in human disease.

Keywords: Biomarkers; Human disease; Metabolism; Mitochondria; Mitrochondrial function.

Fig. 1.

PBMCS can be used to study different aspects of mitochondrial structure and function at the cellular level. Respirometry, electrode measurements of Δψm, cardiolipin assays, spectrophotometry of the ETC, mtDNA quantification, and florescence analysis of Δψm and mito-ROS are all used to distinguish proper mitochondrial function from dysfunction.

Fig. 2.

Mitochondrial function at the tissue level can be measured by a variety of experimental techniques. A diverse range of tissues from muscle to skin biopsies can be analyzed using techniques such as flow cytometry, respirometry, positron emission tomography (PET) imaging, levels of circulating mitochondrial proteins (i.e.. Peroxiredoxin), and Magnetic Resonance Spectroscopy (MRS) to determine mitochondrial function.