Metabolic features of chronic fatigue syndrome

Abstract

More than 2 million people in the United States have myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We performed targeted, broad-spectrum metabolomics to gain insights into the biology of CFS. We studied a total of 84 subjects using these methods. Forty-five subjects (n = 22 men and 23 women) met diagnostic criteria for ME/CFS by Institute of Medicine, Canadian, and Fukuda criteria. Thirty-nine subjects (n = 18 men and 21 women) were age- and sex-matched normal controls. Males with CFS were 53 (±2.8) y old (mean ± SEM; range, 21-67 y). Females were 52 (±2.5) y old (range, 20-67 y). The Karnofsky performance scores were 62 (±3.2) for males and 54 (±3.3) for females. We targeted 612 metabolites in plasma from 63 biochemical pathways by hydrophilic interaction liquid chromatography, electrospray ionization, and tandem mass spectrometry in a single-injection method. Patients with CFS showed abnormalities in 20 metabolic pathways. Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome. Pathway abnormalities included sphingolipid, phospholipid, purine, cholesterol, microbiome, pyrroline-5-carboxylate, riboflavin, branch chain amino acid, peroxisomal, and mitochondrial metabolism. Area under the receiver operator characteristic curve analysis showed diagnostic accuracies of 94% [95% confidence interval (CI), 84-100%] in males using eight metabolites and 96% (95% CI, 86-100%) in females using 13 metabolites. Our data show that despite the heterogeneity of factors leading to CFS, the cellular metabolic response in patients was homogeneous, statistically robust, and chemically similar to the evolutionarily conserved persistence response to environmental stress known as dauer.

Keywords: cell danger response; chronic fatigue syndrome; dauer; metabolomics; mitochondria.

Fig. 1.

Metabolomic diagnosis of CFS. (A) Males. (B) Females. Multivariate analysis using PLSDA clearly distinguished controls and patients with chronic fatigue in both males and females. (C) Biochemical pathway impact analysis—males, The top five pathway disturbances in males were responsible for 82% of the metabolic impact. These were sphingolipids (49%); phospholipids (16%); P5C, Arg, and proline (Pro) (7%); glycosphingolipids (6%); and cholesterol (4%). (D) Females. The top six pathway disturbances in females were responsible for 83% of the metabolic impact. These were sphingolipids (35%); phospholipids (26%); glycosphingolipids (9%); purines (5%); microbiome (5%); and P5C, Arg, and Pro (3%). (E) Metabolic pathways disturbed in CFS. A total of 20 pathways were disturbed in males and females with CFS. Nine of these were common to both, and 11 showed gender differences. (F) Diagnostic and individualized metabolite abnormalities—females. The number of abnormal metabolites that were diagnostic for CFS, as determined by multivariate analysis, is indicated in green. The number of metabolites that are abnormal (≥2 SD above or below the control mean) but are not specifically characteristic of CFS is indicated in red.

Fig. 2.

The diagnostic performance of targeted metabolomics in CFS; AUROC curve analysis. (A) Males. Eight metabolites were selected and tested by bootstrap resampling as an example of one possible multianalyte diagnostic classifier. Training set overfitting was minimized by using RF decision tree analysis (61). The eight metabolites selected were phosphatidyl choline PC(16:0/16:0), glucosylceramide GC(18:1/16:0), 1-P5C, FAD, pyroglutamic acid (also known as 5-oxoproline), 2-hydroxyisocaproic acid (HICA), l-serine, and lathosterol. The diagnostic accuracy measured as the AUROC curve was 0.94 [95% confidence interval (CI), 0.84–1.0]. (B) Females. Thirteen metabolites were selected as a diagnostic classifier in females as described above. The 13 metabolites were THC(18:1/24:0), phosphatidyl choline PC(16:0/16:0), hydroxyproline, ceramide(d18:1/22:2), lathosterol, adenosine, phosphatidylinositol PI(16:0/16:0), FAD, 2-octenoylcarnitine, phosphatidyl choline plasmalogen PC(22:6/P18:0), phosphatidyl choline PC(18:1/22:6), 1-P5C, and CDCA. The diagnostic accuracy measured as the AUROC curve was 0.96 (95% CI, 0.86–1.0). n = 18 control males and 22 CFS males, and n = 21 control females and 23 CFS females.