VGF and amyotrophic lateral sclerosis: This complexity is further exemplified in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), where patients in early stages exhibit elevated plasma levels of certain VGF-derived "NERP peptides" [21] while others—such as TLQP peptides—are decreased in both early and late disease stages, alongside further reductions in advanced stages of peptides derived from the C-terminal region of proVGF [22].