The insufficient transformation of proBDNF into mBDNF due to abnormal proteolytic cleavage leads to a change in BDNF levels in the peripheral blood and CNS, and it might be involved in the pathogenesis of various diseases, such as depression, Parkinson’s disease, amyotrophic lateral sclerosis and multiple sclerosis [8]. Here, BDNF is linked to amyotrophic lateral sclerosis.