Author(s): ALVES DE FONTES-JÚNIOR, A., SIERRA, A.1, DE OLIVEIRA, L.1, DE SOUSA, C.1, CURY-BOAVENTURA, M., Institution: UNIVERSIDADE CRUZEIRO DO SUL , Country: BRAZIL, Abstract-ID: 2432

INTRODUCTION:
The magnitude of physical exertion possibly represents a significant regulator of the secretion of several myokines. It has been reported that acute exercise increases the activity of PPARδ and PGC-1α through the release of myokines, as IL-15, stimulating mitochondrial biogenesis, lipid oxidation and browning of white adipose tissue (WAT) and benefiting the cardiometabolic system. However, few studies have evaluated the role of IL-15 in cardiometabolic function in different exercise loads. The present study investigated the correlation between IL-15 plasma concentration and cardiometabolic parameters at the three thresholds of a cardiopulmonary exercise test (CPET) in endurance runners.

METHODS:
Seventy-two endurance athletes, between 30 and 55 years old (mean ± 41.4), healthy and with no history of cardiovascular diseases, participated in this study. Blood samples were collected at rest to determine the plasma levels of interleukin (IL)-15 by enzyme immunosorbent assay. The CPET test was performed using a treadmill protocol (TEB Apex 200, TEB, São Paulo, Brazil), with a fixed inclination of 1% and the speed starting at 8km/h increasing 1km/h per minute until the runners maximum exhaustion. The analysis of expired gases was performed in a breath-by-breath system (CPET Quark, Cosmed, Rome, Italy) at the first, second and third thresholds (anaerobic threshold, AT, respiratory compensation, RC, and Peak, respectively). Correlations between the parameters IL-15 and CPET were performed using Spearmans test. Statistical significance was accepted at p < 0.05 in all analyses.

RESULTS:
The data showed that IL-15 levels were positively correlated with speed (km/h) in AT, RC and Peak (r= 0.3595, p= 0.0019, r= 0.2814, p= 0.0166, r= 0.2749, p= 0.0194, respectively) and with fat oxidation (%) in AT and RC (r= 0.4618 p= <0.0001, r= 0.3007 p=0.0103,respectively). Moreover, IL-15 levels also had inverse correlation with relative quotient (RQ) in AT, RC and Peak (r= -0, 469 p= <0.0001, r= -0.4129 p= 0.0003, r= -0.2587 p= 0.0282, respectively), with VE/VO2 in AT, CR and Peak (r= -0.3993 p= 0.0005; r= -0.3661 p= 0.0016; r= -0.3669 p= 0.0015, respectively) and with CHO (%) in AT and RC (r= -0.4879 p= <0.0001; r=-0.3007 p= 0.0103).

CONCLUSION:
IL-15 is associated with greater lipid oxidation in all thresholds of a cardiopulmonary exercise test demonstrated by higher % of fat oxidation and RQ which may can sustain the exercise longer in each threshold. Our findings suggest that IL-15 is crucial to improve lipid metabolism and promote resistance in endurance runners.