Molecular evidence of autophagy impairment as serum level of ATG13 is elevated in patients with myalgic encephalomyelitis and chronic fatigue syndrome: two independent case-control studies

Myalgic Encephalomyelitis and chronic fatigue syndrome is a multisystem illness characterized with extreme muscle fatigue associated with pain, neurocognitive impairment, and chronic inflammation. Despite intense investigation, the molecular mechanism of this disease is still unknown. Here we report two independent case-control studies to demonstrate that autophagy proteins are strongly upregulated in the serum of ME/CFS patients indicative of severe impairment in metabolic events of autophagy. Serum samples collected from two healthy and two age-matched patients were assayed for protein aggregation, screened for autophagy-related factors via an antibody array, quantified with densitometric analyses, and finally reconfirmed with ELISA analyses. Based on that double-blinded and gender-balanced study, the levels of ATG13, p62, and alpha-synuclein (α-syn) were found to be consistently elevated in the serum samples of these two ME/CFS patients. Moreover, our microglia-based oxidative stress response study and nitrite analyses indicated that serum samples of ME/CFS patients evoked the production of reactive oxygen species (ROS) and nitrite in human HMC3 microglial cells, whereas neutralization of ATG13 was shown to strongly diminish the production of ROS and nitrite demonstrating the de novo effect bloodborne autophagy factors on inducing the stress response in microglial cells. Collectively, our results indicate that the impairment of autophagy followed by upregulations of autophagy markers especially ATG13 in serum could be a pathological hallmark in ME/CFS.