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
Докторанд
Slavić, Vjeroslava G.Ментор
Kamenov, BorislavЧланови комисије
Ilić, StevanRadovanović, Dragan
Nikolić, Goran
Метаподаци
Приказ свих података о дисертацијиСажетак
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.