Adipocitokines and physical activity during growth

Adipocitokines and physical activity during growth Cicchella A*, Jürimäe J°, Jürimäe T°, Lätt E, Haljaste K°, Purge P°, Hamra J^, von Duvillard SP^. *Faculty of Exercise and Sport Sciences University of Bologna, Italy ° Institute of Sport Pedagogy and Coaching Sciences, Center of Behavioral and Health Sciences, University of Tartu, Estonia. ^ Department of Health and Human Performance, Texas A&M University, Commerce, TX, USA Two hormones are primarily responsible for regulating the body's energy balance, telling the body when it is hungry and when it is full. Ghrelin, a peptide secreted by the stomach, stimulates appetite and increases before meals. Leptin, which affects body weight and is secreted primarily by fat cells, signals the hypothalamus regarding the degree of fat storage in the body; decreased leptin tells the body there is a calorie shortage and promotes hunger, while increased levels promote energy expenditure. In the first study, our aim was to: 1) study the effect of regular physical activity on plasma ghrelin concentration after onset of puberty in girls; 2) to examin the association of fasting plasma ghrelin concentration with various plasma biochemical, body composition, and aerobic capacity variables in healthy adolescent girls; In the second study, to examine the influence of elevated energy expenditure on ghrelin and BMD in young male competitive swimmers advancing from prepubertal to pubertal maturation levels. Fifty healthy schoolgirls ages 11 to 16 yr were divided either into a physically active (N = 25) or a physically inactive (N = 25) group. The physically active group consisted of swimmers who had trained on an average of 6.2 +/- 2.0 h.wk(-1) for the last 2 yr, whereas the inclusion criterion for the physically inactive group was the participation in physical education classes only. RESULTS: Physically active girls had significantly higher (P < 0.05) mean plasma ghrelin levels than the physically inactive girls (maturation I: 1152.1 +/- 312.9 vs 877.7 +/- 114.8 pg.mL(-1); maturation II: 1084.0 +/- 252.5 vs 793.4 +/- 164.9 pg.mL(-1)). Plasma ghrelin concentration was negatively related to percent body fat, fat mass, peak oxygen consumption per kilogram of body mass, leptin, estradiol, insulin, and insulin-like growth factor-I (IGF-I) (r > -0.298; P < 0.05). Multivariate linear regression analysis to determine the predictors of ghrelin concentration using the variables that were significantly associated with ghrelin concentration demonstrated that plasma IGF-I was the most important predictor of plasma ghrelin concentration (beta = -0.396; P = 0.008). CONCLUSION: Regular physical activity influences plasma ghrelin concentrations in girls with different pubertal maturation levels. Plasma IGF-I concentration seems to be the main determinant of circulating ghrelin in healthy, normal-weight adolescent girls. The second study included 19 healthy swimmers (pubertal stage 1) aged between 10 and 12 years. The participants were at the pubertal stages 2 and 3, and 3 and 4 at the second and third year, respectively. CONSLUSION: Ghrelin was decreased only after the first year. No changes were observed in leptin during the study period. Testosterone increased according to the pubertal development at each measurements. IGF-I was increased at the third measurement compared to the first two measurements. Total and lumbar spine BMDs increased according to the pubertal development in all boys at each measurements, while no changes in femoral neck BMD were observed. Ghrelin was not related to BMD after adjusting for pubertal status. We conclude that ghrelin was decreased at onset of puberty, while no further changes in ghrelin were seen with advancing pubertal stage. Total and lumbar spine BMD increased, while no changes in femoral neck BMD occurred. Ghrelin did not appear to have a direct influence on BMD in young male competitive swimmers. Jürimäe J, Lätt E, Haljaste K, Purge P, Cicchella A,...