Cellular bioenergetics is impaired in patients with chronic fatigue syndrome

Abstract

Chronic fatigue syndrome (CFS) is a highly debilitating disease of unknown aetiology. Abnormalities in bioenergetic function have been cited as one possible cause for CFS. Preliminary studies were performed to investigate cellular bioenergetic abnormalities in CFS patients. A series of assays were conducted using peripheral blood mononuclear cells (PBMCs) from CFS patients and healthy controls. These experiments investigated cellular patterns in oxidative phosphorylation (OXPHOS) and glycolysis. Results showed consistently lower measures of OXPHOS parameters in PBMCs taken from CFS patients compared with healthy controls. Seven key parameters of OXPHOS were calculated: basal respiration, ATP production, proton leak, maximal respiration, reserve capacity, non-mitochondrial respiration, and coupling efficiency. While many of the parameters differed between the CFS and control cohorts, maximal respiration was determined to be the key parameter in mitochondrial function to differ between CFS and control PBMCs due to the consistency of its impairment in CFS patients found throughout the study (p≤0.003). The lower maximal respiration in CFS PBMCs suggests that when the cells experience physiological stress they are less able to elevate their respiration rate to compensate for the increase in stress and are unable to fulfil cellular energy demands. The metabolic differences discovered highlight the inability of CFS patient PBMCs to fulfil cellular energetic demands both under basal conditions and when mitochondria are stressed during periods of high metabolic demand.

Fig 1

A. Profile of the key parameters of mitochondrial respiration measured during a mitochondrial stress test. B. Key parameters measured during a glycolysis stress test. Based on images found in the XF report generator user guide [44].

Fig 2. Example extracellular flux traces of a mitochondrial stress test performed on fresh and frozen PBMCs isolated from CFS patients and controls.

Fig 3. Results from a mitochondrial stress test conducted using fresh and frozen CFS and control PBMCs.

A. Basal respiration. B. ATP production. C. Proton leak. D. Maximal respiration. E. Reserve capacity. F. Non-mitochondrial respiration. G. Coupling efficiency. Control fresh n = 3; CFS fresh n = 25; Control frozen n = 12; CFS frozen n = 38. * denotes p ≤ 0.05; *** denotes p ≤ 0.005. Groups were compared using a two-way ANOVA with LSD test and post-hoc Bonferroni correction for multiple comparisons.

Fig 4. Example trace of a mitochondrial stress test performed in control and CFS PBMCs incubated for 24 hours in high (10mM) glucose.

Fig 5. Results from a mitochondrial stress test conducted using CFS and control PBMCs incubated for 24 hours in low (1mM) and high (10mM) glucose.

A. Basal respiration. B. ATP production. C. Proton leak. D. Maximal respiration. E. Reserve capacity. F. Non-mitochondrial respiration. G. Coupling efficiency. Control low glucose n = 12; CFS low glucose n = 39; Control high glucose n = 12; CFS high glucose n = 38. * denotes p ≤ 0.05; *** denotes p ≤ 0.005. Groups were compared using a two-way ANOVA with LSD test and post-hoc Bonferroni correction for multiple comparisons.

Fig 6. Assessment of cellular glycolytic function in CFS and control PBMCs.

A. Results from a glycolysis stress test in PBMCs. B. Glycolysis, C. glycolytic capacity, and D. glycolytic reserve calculated from glycolysis stress test results. Control n = 16; CFS n = 19.