▁G ly c ine ▁prop ion yl - L - c arn it ine ▁( G PL C ) ▁is ▁a ▁prop ion yl ▁est er ▁of ▁car nit ine ▁that ▁includes ▁an ▁additional ▁g ly c ine ▁component . ▁Due ▁to ▁t issues ▁est er ases ▁en zym es , ▁G PL C ▁should ▁act ▁as ▁a ▁prod rug ▁and ▁lead ▁to ▁g ly c ine , ▁car nit ine ▁and ▁prop ionic ▁acid ▁in ▁the ▁body . ▁ ▁N it ric ▁ox ide ▁stim ul ant ▁ ▁G PL C ▁has ▁been ▁shown ▁in ▁two ▁studies ▁to ▁result ▁in ▁an ▁increase ▁in ▁blood ▁levels ▁of ▁nit rate / nit rite ▁( a ▁sur rog ate ▁marker ▁of ▁nit ric ▁ox ide ; ▁not ▁a ▁direct ▁measure ▁of ▁nit ric ▁ox ide ), ▁when ▁used ▁at ▁a ▁daily ▁do se ▁of ▁ 4 . 5   gram s . ▁In ▁one ▁study , ▁G PL C ▁was ▁provided ▁to ▁previously ▁sed ent ary ▁men ▁and ▁women ▁who ▁were ▁also ▁assigned ▁to ▁super vised ▁aer ob ic ▁exercise ▁for ▁eight ▁weeks . ▁ ▁A ▁significant ▁increase ▁in ▁rest ing ▁levels ▁of ▁blood ▁nit rate / nit rite ▁was ▁noted ▁for ▁subjects ▁receiving ▁G PL C ▁compared ▁to ▁place bo ▁( in ▁a ▁double ▁blind ▁design ). ▁Sub ject s ▁who ▁received ▁G PL C ▁were ▁also ▁noted ▁as ▁having ▁lower ▁levels ▁of ▁mal ond ial de hy de , ▁a ▁li pid ▁per ox id ation ▁bi om ark er ▁indicating ▁free ▁radical