The influence of weight loss on fibrinolytic and metabolic parameters in obese children and adolescents

We studied i) whether short-term weight loss alters plasminogen activator i nhibitor-1 antigen (PAI-1-Ag) and tissue-type plasminogen activator antigen (tPA-Ag) in obese children, and ii) whether changes in body composition an d/or abdominal adiposity are responsible for changes in PAI-1 and tPA-Ag. 2 0 obese boys (mean age 11.9 yr) and 40 obese girls (mean age 12 yr) were st udied before and after three weeks of low-caloric diet and physical activit y. Body composition was assessed by means of bioelectrical impedance, and t he waist-to-hip ratio (WHR) was measured. Blood samples were determined for insulin, glucose, triglycerides, PAI-1-Ag, tPA-Ag, and the fasting insulin resistance index (FIRI) was calculated. Boys had a greater WHR, higher lev els of glucose, and a slightly greater FIRI than girls. Estimates of adipos ity, insulin, and triglycerides were correlated with PAI-1 and tPA-Ag. WHR was significantly correlated with fibrinolytic parameters only in girls. In sulin and tPA-Ag contributed to PAI-1 (adj. R-2 = 0.36, p <0.0001), whereas percentage fat mass and triglycerides contributed to tPA-Ag (adj. R-2 = 0. 469, p <0.0001). The weight loss program significantly reduced adiposity, a bdominal adiposity, and lowered fibrinolytic and metabolic parameters. Init ial levels of PAI-1 and changes in body mass contributed to the fall in PAI -1 (adj. R-2 = 0.18, p = 0.0016) and initial levels of tPA-Ag contributed s ignificantly to changes in tPA-Ag (adj. R-2 = 0.57, p <0.0001). The results suggest that changes in fibrinolytic parameters are associated with the lo ss in body mass but can occur independently of a concomitant reduction in f atness. Although initial PAI-1 and tPA-Ag predict the changes of these fibr inolytic parameters, the results do not exclude the possibility that the im provement in metabolic state and changes in unmeasured parameters related t o physical activity and low-caloric diet could have influenced our findings .