Forces, Fluxes, and Fuels: Tracking mitochondrial metabolism by integrating measurements of membrane potential, respiration, and metabolites.

Assessing mitochondrial function in cell-based systems is a central component of metabolism research. However, the selection of an initial measurement technique may be complicated given the range of parameters that can be studied as well as the need to define the mitochondrial (dys)function of interest. This methods-focused review compares and contrasts the use of mitochondrial membrane potential measurements, plate-based respirometry, and metabolomics and stable isotope tracing. We demonstrate how measurements of (i) cellular substrate preference, (ii) respiratory chain activity, (iii) cell activation, and (iv) mitochondrial biogenesis are enriched by integrating information from multiple methods. This manuscript is meant to serve as a perspective to help choose which technique might be an appropriate initial method to answer a given question, as well as provide a broad 'roadmap' for designing follow-up assays to enrich datasets or resolve ambiguous results.