Quantifying variability associated with high-resolution respirometry in human permeabilized skeletal muscle fibers

Abstract

Rates of skeletal muscle mitochondrial respiration are often measured using an Oroboros Oxygraph-2K (O2K) high-resolution respirometer. The purpose of this investigation was to determine the coefficients of variation (CV) and technical error of measurement (TEM) for rates of mitochondrial respiration obtained from two permeabilized skeletal muscle fiber bundles from a single biopsy (intra-biopsy) and on two experimental visits (inter-biopsy) using an O2K high-resolution respirometer. We hypothesized that our CV and TEM values would be similar to those reported by other research groups. We also hypothesized that there would be no statistically significant differences between rates of mitochondrial respiration obtained on two experimental visits separated by one week. Biopsies of the vastus lateralis were obtained from 14 healthy young individuals (female: 10; male: 4; age: 23 ± 3 years; height: 1.73 ± 0.1 m; body mass: 73.3 ± 20.4 kg) from the same leg on two experimental visits separated by an average of 6 ± 2 days. We examined rates of pyruvate and malate-supported, adenosine diphosphate (ADP)-stimulated mitochondrial respiration in the presence and absence of 20 mM creatine. Mean average intra- and inter-biopsy CVs for maximal complex I+II-supported, ADP-stimulated mitochondrial respiration were 11.5 % and 9.7 %, respectively. Mean average intra- and inter-biopsy TEM values for maximal complex I+II-supported, ADP-stimulated mitochondrial respiration were 10.6 pmol/s/mg wet weight and 8.6 pmol/s/mg wet weight, respectively. Statistically significant differences for rates of mitochondrial respiration were not observed between experimental visits regardless of creatine condition (non-creatine or 20 mM creatine). Our data are consistent with previously reported CV and TEM values and demonstrate that changes in maximal mitochondrial respiration of approximately 15 % can be reliably detected with a sample size of ∼10 participants.