To date, 14 studies have investigated GSH, GSSG, GSH/GSSG and/or tGSH levels in the plasma of healthy adults (Andriollo-Sanchez et al., 2005, Chillemi et al., 2005, Giustarini et al., 2006, Hernanz et al., 2000, Houze et al., 2001, Jones et al., 2002, Kretzschmar et al., 1991, Maciejczyk et al., 2019, Michelet et al., 1995, Nuttall et al., 1998, Paolisso et al., 1998, Rea et al., 2004, Samiec et al., 1998, Yang et al., 1995), with the majority using HPLC (N = 10, 71%) (Chillemi et al., 2005, Giustarini et al., 2006, Hernanz et al., 2000, Houze et al., 2001, Jones et al., 2002, Michelet et al., 1995, Paolisso et al., 1998, Rea et al., 2004, Samiec et al., 1998, Yang et al., 1995), and the remaining using colorimetry (N = 2, 14%) (Kretzschmar et al., 1991, Maciejczyk et al., 2019), enzyme-rate essay (Nuttall et al., 1998) (N = 1, 7%), and spectrophotometry (N = 1, 7%) (Andriollo-Sanchez et al., 2005) (Table 3)

Repeated muscle contractions in our faces, such as frowning, squinting, raising eyebrows, etc cause the skin to furrow and fold
The authors suggested that the observed age-specific increases in regional brain GSH levels may point to a compensatory response to elevation in ROS production to prevent a state of OS (Hupfeld et al., 2021)
doi: 10.1128/mBio.02781-18 92 HeumelSde Rezende RodovalhoVUrienCSpecqueFBrito RodriguesPRobilCet al