CK is considered a central controller of cellular energy
CK is considered a central controller of cellular energy homeostasis that catalyzes the reversible transfer of a phosphoryl group from ATP to adenosine diphosphate (ADP) and creatine to produce PCr . This enzyme builds up a large pool of rapidly diffusing PCr for temporal and spatial buffering of ATP levels, playing an important role in tissues with large and fluctuating energy demands . The PCr acts as an energy source, buffer and energy transporter, shuttling energy from subcellular sites to site of energy consumption, where the cellular ATPases and ATP-dependent ion pumps are located, such as the sodium-potassium (Na+, K+-ATPase) and hydrogen (H+-ATPase) pumps [7,8]. A study conducted by Szabó et al.  demonstrated that mycotoxins-contaminated diets impairs the Na+, K+-ATPase activity in rabbits, contributing to several clinical alterations. Thus, our hypothesis is that an impairment of the CK/PCr system, i.e., of the ATP production, affects the activities of Na+, K+-ATPase and H+-ATPase, which are ATP-dependent ions pumps.
Na+, K+-ATPase is an essential membrane protein due to its role in the maintenance of cellular resting potential and osmotic balance . This enzyme requires ATP to maintain high intracellular K+ concentrations and low Na+ concentrations, which is essential to maintain adequate cellular functions, such as the resting membrane potential, regulation of cellular volume and pH, and driving the secondary Isochlorogenic acid C sale . Moreover, the H+-ATPase (also known as V-ATPase) is a complex mediating ATP-driven vectorial transport of protons across membranes, that develops an important role to maintain the ideal pH of intracellular compartments, such as the Golgi apparatus and endosomes, and an impairment in the maintenance of pH may lead to cell death . In this sense, evidences suggest that impairment in the CK/PCr system reduces the availability of ATP, compromising the good functioning of ATPases and, consequently, the ionic balance, specially of calcium (Ca+), potassium (K+), and sodium (Na+) ions [13,14]. Based on these evidences, the aim of this study was to evaluate the involvement of CK/PCr system in the impairment of energetic homeostasis in piglets fed with a diet co-contaminated with mycotoxins, as well as the effects on ATPases activities.
Material and methods
Discussion The present study demonstrated, for the first time, the involvement of CK/PCr system in the impairment of energetic homeostasis in piglets fed with a diet co-contaminated by mycotoxins. Our findings clearly show the inhibition of serum CK activity, indicating an imbalance of energetic homeostasis in piglets fed with a diet contaminated with mycotoxins, compromising serum Na+, K+-ATPase and H+-ATPase activities. As expected, piglets feed with a diet co-contaminated with mycotoxins presented a significant weight loss after 10 and 15 days of feed, in accordance to observed by Drábek et al.  after diet containing 30 and 300 μg of AFB1 per kg of fed during 26 days. Also, recent study conducted by Souza et al.  demonstrated that piglets feed with a diet containing 300 μg/kg of aflatoxins and 8000 μg/kg of fumonisins was able to reduce the weight gain after 10 and 15 days of diet exposure, in agree to observed in this present study. Moreover, is important highlight that reduction on serum protein concentration observed in animals exposed to a diet containing AFB1 and FB1 (50 and 200 μg/kg of each mycotoxin) may be contribute to impairment of weight gain, as observed by Tessari et al. . The diet co-contaminated with mycotoxins inhibited the serum CK activity on days 5, 10 and 15 of experiment, indicating a disequilibrium in the ATP/ADP and PCr/Cr ratios, which may result in a decreased availability of ATP, impairment of energy supply and weight loss, which may explain the depletion of intracellular ATP levels observed in rat pulmonary macrophage exposed to airborne mycotoxins , as well as in neural cells exposed to mycotoxins produced by Penicillium roqueforti isolated from maize and grass silage . Conversely, a study conducted by Okotie-Eboh et al.  reported a significantly increase of serum CK activity in broilers fed with a diet co-contaminated with 5 μg/g of aflatoxins, similarly to recent observed by Jiang et al.  in broilers fed with a diet contaminated with aflatoxin B1 (6.68 μg/kg), zearalenone (18.32 μg/kg), fumonisin (952.59 μg/kg) and deoxynivalenol (642.16 μg/kg). The difference in the serum CK activity between the studies may be linked with the dose, concentration, time of exposure and the presence of one or more mycotoxins in the diet, since the effects of mycotoxins are direct linked with these factors . It is important to emphasize that augmentation in serum CK is also linked with cell damage, muscle cell disruption and diseases. These cellular disturbances can lead CK to leak from cells into blood , consequently increasing its serum concentration. In our understanding, the augmentation of serum CK activity occurs essentially in higher doses of mycotoxins exposition, as well as the combination of more mycotoxins in the diet, indicating intense cell and tissue damage . In summary, the inhibition on CK activity impaired the CK/PCr system, and consequently decreased ATP availability.