AGRN and sarcopenia: Importantly, the C-terminal 22 kDa agrin cleavage fragment (CAF) is increasingly being investigated as a biomarker of age-related sarcopenia (Feng and Ko, 2008; Lin et al., 2008a; Hettwer et al., 2013; Rudolf et al., 2014; Kalinkovich and Livshits, 2015; Landi et al., 2016).