Journal of Energy Bioscience 2025, Vol.16, No.1, 42-52 http://bioscipublisher.com/index.php/jeb 45 3.3 Regulatory mechanisms at the molecular level The operation of the creatine phosphate system is also regulated by some molecular mechanisms. The activity of CK is affected by several factors, such as the amount of ATP and creatine, as well as the current energy state of the cell (Bonilla et al., 2021a; 2021b). In thermogenic adipocytes, there is a special regulation method, which is the decomposition of PCr by an enzyme called TNAP. This reaction will start a repeated "dephosphorylation and rephosphorylation" process, thereby activating thermogenic respiratory activity (Sun et al., 2021). Different types of CK enzymes appear in different locations in the cell. This distribution helps energy to be effectively used and transmitted locally (Puurand et al., 2018; Branovets et al., 2020). This "spatial arrangement" allows cells to distribute energy more reasonably according to the needs of different regions. 4 Physiological Functions of the Creatine Phosphate System 4.1 Role in muscle contraction and athletic performance The phosphocreatine system is important for muscle movement, especially when fast and large amounts of energy are needed. For example, in high-intensity, short-duration exercises such as sprinting or weightlifting, the body's demand for ATP exceeds the rate at which the aerobic system can provide it. At this time, phosphocreatine (PCr) in the muscle will immediately give a phosphate group to ADP to quickly generate ATP. This can help the muscle continue to contract and delay fatigue (Stockebrand et al., 2018; Hao et al., 2021; Vulturar et al., 2021). Vulturar et al. (2021) found through research that creatine supplementation can increase the reserves of PCr in the muscle. This not only helps increase lean body mass, but also improves anaerobic and aerobic exercise performance. 4.2 Functions in the brain, heart, and other high-energy-demand organs Not only muscles, but also organs such as the brain and heart cannot do without the creatine phosphate system. Creatine in the brain is important for maintaining normal thinking and nerve cell development. If the brain lacks creatine, intellectual problems and behavioral abnormalities may occur (Stockebrand et al., 2018; Balestrino and Adriano, 2019; Bonilla et al., 2021a). In the heart, the PCr system mainly maintains ATP stability and can also play a protective role when the heart is ischemic (Hao et al., 2021; Farr et al., 2022) (Figure 2). Creatine also plays a role in adipose tissue, regulating thermogenesis and energy consumption (Kazak and Cohen, 2020). 4.3 Adaptations in different types of muscle fibers and tissues Because different types of muscles use different amounts of energy, the PCr system will adjust accordingly. Fast-twitch muscle fibers (those with strong explosive power) contain more creatine phosphate than slow-twitch muscle fibers (responsible for endurance activities) (Stockebrand et al., 2018; Vulturar et al., 2021). This shows that creatine is very important for muscle health. If muscles lack creatine transporter (CT1), their PCr levels will decrease, and muscles may become weak or even atrophy (Stockebrand et al., 2018). The creatine system will also adjust with changes in physiological state. For example, with age, changes in creatine kinase activity and PCr levels will affect muscle function and energy metabolism (Mosher et al., 2022). 4.4 Therapeutic potential and clinical applications Creatine is not just a sports supplement, it also shows potential in the treatment of some diseases. Studies have found that creatine supplementation may be helpful for muscular dystrophy, muscle problems caused by statins, and even refractory depression. For vegetarians and vegans, because they do not consume creatine in their diet, their muscle creatine levels will be low. Creatine supplementation can improve their muscle state and psychological performance (Balestrino and Adriano, 2019). The role of creatine in cancer is also being studied. It may affect the survival of cancer cells and may also regulate the immune system (Kazak and Cohen, 2020). 5 Pathophysiological Implications 5.1 Alterations in creatine metabolism in muscle disorders People with muscle diseases, such as muscular dystrophy and myopathy, often experience significant changes in creatine metabolism. Normally, creatine helps muscle cells store and regulate energy and maintain ATP levels. But when people develop muscle diseases, problems arise in the energy system of muscle cells. A study by Balestrino
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