APP and Parkinson disease: Elevated levels of lactate are associated with many neurodegenerative diseases, such as PD, HD, AD and ALS (Liguori et al., 2016; Martin et al., 2007; Siciliano et al., 2002; Yamamoto et al., 1997), and previous studies have shown that aggregation of amyloid beta peptides is increased in the presence of lactate at pH levels below 7 (acid) (Su and Chang, 2001; Xiang et al., 2010).