Glikogen fosforilaza tip bb i hit šok protein 27 - indikatori miokardnog stresa kod vaterpolista
Glycogen phosphorylase type bb and heat shock protein 27- indicators of myocardial stress in water polo players
AuthorSlavić, Vjeroslava G.
Committee membersIlić, Stevan
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Introduction: In recent years, there is an evidence of many sudden cardiac deaths among elite athletes. The risk of myocardial damage in long-term exercise has been much debated because it has been reported that exercise increased serum concentration of cardiac biomarkers in elite athletes but also in people who were involved in recreational sports. Although numerous studies have been performed, it is still unclear whether the increase in these markers in healthy athletes is clinically significant or is a part of the physiological response to prolonged exercise. Glycogen phosphorylase type bb (GP-BB) is segregated as an enzyme with high specificity to myocardial cells and high sensitivity for clinical diagnosis of early myocardial ischemia. GP-BB is a glycolytic enzyme responsible for the mobilization of intracellular glucose from glycogen depots under conditions of ischemia to compensate “hunger” tissue for energy. In the process of glycogenolysis, GP-BB is converted to soluble, mono...meric cytoplasmatic structure with consequent creation of a concentration gradient that is necessary for the release of protein in the blood. Since it is a metabolically active enzyme, its release from cardiac cells does not require a cell death and/or necrosis. Heat shock proteins (Hsp) are evolutionarily conserved protein structures with an important role in monitoring and/or supervising of the process of synthesis of structural and functional cellular proteins. They are present in all human cells and make 5 to 10% of total intracellular protein content. After cell exposure to stressor, their content increases to 15%. Hsp27 is responsible for cytoprotective processes which inhibit apoptosis. The expression and synthesis of Hsp27 transiently increase in response to stressor and upon the cessation of stress its concentration rapidly returns to baseline value, which makes it a very sensitive indicator of acute events at the cellular level. In recent years, numerous in vitro and in vivo studies have confirmed a strong protective effect of Hsp27 on ischemic myocardial cell damage. The aim of this study was to determine an importance of GP-BB and Hsp27 as sensitive and specific markers for the assessment of early myocardial stress in water polo players. Materials and Methods: A prospective and experimental study included 20 male water polo players, randomly divided into two groups that matched for gender, age, length of active practicing water polo and level of physical stamina: (1) group exposed to a strenuous exercise training (experimental group, n = 10), (2) group that was not trained (control group, n = 10). Blood samples for testing were obtained at the following time points: baseline, 1, 30 and 60 minutes following the exercise. The control blood samples were obtained at equivalent timepoints. The concentrations of GP-BB and Hsp27 were determined by immunosorbent tests associated with enzymes (sandwich ELISA) using commercial quantitative kits (Diagenics, USA for GP-BB, Calbiochem, USA for Hsp27). The color intensity was read at 450 nm on the spectrophotometer (Microplate Manager Bio-Rad Laboratories, Inc.). The results were statistically analyzed using the statistical package for Windows, version 17.0 (Statistical Package for Social Science-SPSS Inc., IL, USA). Statistically significant differences were considered as the values of p <0.05 and p <0.001. Results: Serum concentrations of GP-BB before training/basal were within the normal range in all water polo players. After training, higher concentrations of GP-BB occurred in 40% of subjects after the first and thirtieth and 10% after the sixtieth minute. In the control group, the concentrations of this enzyme were unchanged, but there were a certain dynamic in the time intervals and significant difference in serum concentrations between the groups of water polo players only at the last time point (p <0.025). Serum levels of Hsp27 were elevated in all water polo players before training/baseline. However, after training increased concentrations of Hsp27 were observed in 50% water polo players after the first, 60% after the thirtieth and 80% after the sixtieth minute. In the control group of water polo players, higher concentrations were detected in 30% of the subjects after the first, 70% after the thirtieth and 20% after the sixtieth minute. At the observed time intervals, there were no significant differences in the concentrations of Hsp27 between the groups. Serum concentrations of GP-BB and Hsp27 were significantly positively correlated after the first (p <0.05) and thirtieth minutes (p <0.01). Conclusion: The increase in serum concentrations of GP-BB in water polo players by strenuous training point to the existence of metabolic exhaustion of myocardial cells which is reversible. It is accompanied by an increased proteolytic activity in these cells through a decrease in serum concentrations of Hsp27 after exertion. Damage of the protein structure in the myocardial cells, structural and functional, is reversible because the serum concentrations of GP-BB and Hsp27 were significantly correlated in the first and thirtieth minutes after effort. Our results suggest that the GP-BB and Hsp27 could be important indicators of the risk assessment and prevention of developing heart damage in water polo players, but with athletes at all.