ENO2 and Huntington disease: Some isolated studies described increased plasma myeloperoxidase (MPO) [36] and aminopeptidase activities [32], increased serum neuron-specific enolase (NSE) [39], increased plasma lactate levels [32], decreased plasma thioredoxin [36] and serum carnitine levels [40], and decreased plasma thioredoxin reductase 1 activity [36] in patients with HD.