Propionylcarnitine possesses three characteristics that distinguish this acylcarnitine from other members of the carnitine pool. First, it has a unique vasodilatory

effect which is specific to this compound. This may be the reason that PC has been shown to have a high affinity for both skeletal and cardiac muscle tissue. Secondly, PC provides a source of propionyl units which are easily transformed into succinate for mitochondrial utilization in the citric acid cycle as a source of anaplerotic energy. In this way, PC supplies an active energy substrate even during periods of limitations in localized oxygen availability, ie muscle ischemia. Finally, PC provides a replenishment of free carnitine in cases of Sapitinib molecular weight deficiency with intense exercise or disease. Propionyl-L-carnitine, being a prescription medication in both Europe and the SC79 cost United States, has been examined primarily as a treatment in clinical populations with apparent Quisinostat muscle carnitine deficiencies. Controlled clinical trials indicated that PLC provides enhanced work capacity in persons with congestive heart failure [27] and peripheral vascular disease [28]. Glycine propionyl-L-carnitine (GPLC) is a novel nutrient consisting of a molecularly bonded combination of PLC and the amino acid glycine. Glycine is considered

as a glucogenic amino acid in that it helps to regulate blood sugar levels and is also very important in the formation of creatine. Interestingly, glycine has been shown to have its own independent vasodilatory effects [29]. Limited research has examined the effects of GPLC on exercise performance within the general population or athletes. An ishchemic-reperfusion

model was used by Bloomer, Smith, isothipendyl and Fisher-Wellman to examine blood nitrite/nitrate levels as an indication of NO production [13]. This model provides a means to assess physiological measures such as blood flow and increased levels of NO in response to occlusive stresses similar to those exhibited during high intensity resistance training. Those studies indicated that GPLC supplementation at 4.5 g per day for one week produced dramatically greater blood nitrite/nitrate levels both at rest and in response to the occlusion/reperfusion stress. Those findings are particularly notable as GPLC is the first and only nutritional supplement product proven to increase NO synthesis. Smith and associates [30] reported findings related to a group of previously inactive persons, who for eight weeks performed stationary cycling and/or walking with GPLC supplementation. Study participants were randomized to receive placebo, 1 or 3 g GPLC per day. The exercise testing, performed prior to and following the eight weeks of training, consisted of the standard Bruce protocol treadmill test and standard 30 sec Wingate test. Thus, the testing procedures introduced a high degree of variability which may have limited measurable performance effects with GPLC.