ADORA2A and Huntington disease: Several kinds of abnormalities including increased cytokines, mitochondrial dysfunction, increased oxidative stress, aberrant adenosine A2A receptor function, reduced phosphorylated serine-threonine protein kinase 1 (Akt), increased pro-catabolic serum metabolites, elevated serum 8OH2’dG, deficient fatty acid amide hydrolase activity, energy deficit, and alteration of phosphatidylcholine in peripheral blood of HD patients have been reported [9,10,27,34,47,48,49,50,51,52,53,54,55,56], whereas only a few showed a positive correlation with disease severity or stage [9,10,27,34,51,53,56,57].