title: Daily cytokine fluctuations, driven by leptin, are associated with fatigue severity in chronic fatigue syndrome: evidence of inflammatory pathology.
abstract: BACKGROUND
  Chronic fatigue syndrome (CFS) is a debilitating disorder characterized by persistent fatigue that is not alleviated by rest. The lack of a clearly identified underlying mechanism has hindered the development of effective treatments. Studies have demonstrated elevated levels of inflammatory factors in patients with CFS, but findings are contradictory across studies and no biomarkers have been consistently supported. Single time-point approaches potentially overlook important features of CFS, such as fluctuations in fatigue severity. We have observed that individuals with CFS demonstrate significant day-to-day variability in their fatigue severity.
  
  
  METHODS
  Therefore, to complement previous studies, we implemented a novel longitudinal study design to investigate the role of cytokines in CFS pathophysiology. Ten women meeting the Fukuda diagnostic criteria for CFS and ten healthy age- and body mass index (BMI)-matched women underwent 25 consecutive days of blood draws and self-reporting of symptom severity. A 51-plex cytokine panel via Luminex was performed for each of the 500 serum samples collected. Our primary hypothesis was that daily fatigue severity would be significantly correlated with the inflammatory adipokine leptin, in the women with CFS and not in the healthy control women. As a post-hoc analysis, a machine learning algorithm using all 51 cytokines was implemented to determine whether immune factors could distinguish high from low fatigue days.
  
  
  RESULTS
  Self-reported fatigue severity was significantly correlated with leptin levels in six of the participants with CFS and one healthy control, supporting our primary hypothesis. The machine learning algorithm distinguished high from low fatigue days in the CFS group with 78.3% accuracy.
  
  
  CONCLUSIONS
  Our results support the role of cytokines in the pathophysiology of CFS.
authors.affiliation: Department of Anesthesiology, Stanford University School of Medicine, Stanford, CA 94304, USA.
authors.forename: Elizabeth Ann
authors.initials: EA
authors.lastname: Stringer
authors.forename: Katharine Susanne
authors.initials: KS
authors.lastname: Baker
authors.forename: Ian R
authors.initials: IR
authors.lastname: Carroll
authors.forename: Jose G
authors.initials: JG
authors.lastname: Montoya
authors.forename: Lily
authors.initials: L
authors.lastname: Chu
authors.forename: Holden T
authors.initials: HT
authors.lastname: Maecker
authors.forename: Jarred W
authors.initials: JW
authors.lastname: Younger
mesh_terms: D000328:Adult; D000465:Algorithms; D015415:Biomarkers / Q000378:metabolism; D015992:Body Mass Index; D016022:Case-Control Studies; D016207:Cytokines / Q000378:metabolism*; D005221:Fatigue / Q000175:diagnosis / Q000378:metabolism*; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000378:metabolism*; D005260:Female; D006801:Humans; D007249:Inflammation; D020738:Leptin / Q000097:blood / Q000378:metabolism*; D008137:Longitudinal Studies; D008875:Middle Aged; D015203:Reproducibility of Results; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D016207:Cytokines; D020738:Leptin