Circulating Fatty Acid Binding Protein 4 Concentration Increases with an Acute Maximal Exercise Independently of Exercise Training Status

Limited data on the response of fatty acid binding protein 4 (FABP4) to acute exercise are available. The purpose of this study was to determine the response of FABP4 to incremental maximal exercise in exercise-trained and untrained men. Eleven exercise-trained young men (T group; age, 20.4 ± 1.2 years) and 9 untrained young men (UT group; age, 20.7 ± 0.5 years) performed an incremental maximal exercise after a 12-h fasting period. Before and immediately after the incremental maximal exercise, venous blood was drawn to measure circulating FABP4, free fatty acid, and glycerol concentrations. Body composition, and aerobic capacity were also assessed. Glycerol concentration significantly increased during the exercise in the T group (group × time interaction: p = 0.034; group effect, p = 0.088; and time effect, p = 0.003), and the percentage increase in glycerol concentration was greater in the T group than in the UT group ( p = 0.046; ES( r ): 0.45). Although circulating FABP4 concentration significantly increased in the two groups (group × time interaction: p = 0.766; group effect, p = 0.114; and time effect, p = 0.001), the percentage increase in FABP4 concentration was similar ( p = 0.210; ES( r ): 0.28). Additionally, the change of FABP4 concentration was not correlated with that of glycerol (r = -0.04, p =0.872). These results indicated that circulating FABP4 concentration increased during incremental maximal exercise regardless of difference in lipolysis and exercise training status in healthy young men. circulating FABP4 concentration to an incremental maximal exercise in exercise-trained and untrained men. Our data demonstrated that despite that exercise-trained men had a greater lipolysis during the incremental maximal exercise, circulating FABP4 concentration increased similarly during this exercise in both exercise-trained and untrained men. Moreover, the change in circulating FABP4 concentration during the incremental maximal exercise was not correlated with that of FFA and glycerol. These findings suggest that circulating FABP4 concentration increases during high-intensity acute exercise regardless of the exercise training status, and the increase in circulating FABP4 concentration during high-intensity acute exercise is accompanied by the increases in blood level of glycerol in the trained but not in the untrained men. that circulating FABP4 during acute incremental maximal exercise in both exercise-trained and untrained an increase in circulating FABP4 concentration was observed in all participants. Thus, high- intensity acute exercise is more likely to increase circulating FABP4 concentration in healthy young individuals. Our findings provide further evidence of the response of circulating FABP4 men. This suggests that suppression of macrophage functions leads to attenuation of the secretion of FABP4 from macrophages in exercise-trained men. However, lack of the data specified for macrophages do not allow us a deeper discussion regarding their roles in FABP4 release during acute exercise. Further studies are required to the of circulating during increment maximal