Phosphocreatine (also known as creatine phosphate) plays a key role in cellular energy metabolism, particularly within muscle cells and neurons, by acting as a rapid reserve for the regeneration of adenosine triphosphate (ATP). While mitochondria are the primary site of ATP production via oxidative phosphorylation, the phosphocreatine system provides a buffer to maintain cellular ATP levels during periods of high energy demand. Scientific studies have demonstrated that the phosphocreatine shuttle facilitates the transport of high-energy phosphates from mitochondria to sites in the cytosol where ATP is needed, such as the contractile apparatus in muscle cells. This shuttle involves the enzyme creatine kinase, which rapidly converts phosphocreatine and ADP back into creatine and ATP.

Supplementation with creatine (which increases phosphocreatine stores) has been shown in numerous peer-reviewed studies to improve high-intensity exercise performance and recovery, and there is emerging evidence for neuroprotective effects related to mitochondrial function, particularly in neurodegenerative diseases. Some preclinical and small clinical studies indicate that enhanced phosphocreatine availability may help maintain mitochondrial integrity and function under metabolic stress. However, while the mechanistic link between phosphocreatine and mitochondrial support is well-established, the direct clinical outcomes related specifically to mitochondrial diseases or dysfunction are still an ongoing area of research.

In summary, there is strong mechanistic and some clinical evidence supporting phosphocreatine's role in supporting mitochondrial energy metabolism, justifying its use for this purpose.