Inflammatory status in adolescents : the impact of health determinants such as overweight and fitness

Overweight prevalences are rising among youth and the prevention of associated chronic diseases is priority concern in public health. Inflammatory processes are involved in the pathogenesis of cardiovascular diseases and may also play an important initiating role in the development of the cardiovascular lesion.

The overall aim of this thesis was to establish reference values of body fat composition in adolescence and to investigate the association between chronic low-grade inflammation and overweight, and further to examine if fitness counteracts this possible association. In total 2160 13 to 18 year-old Spanish adolescents were studied and a subsample of 493 subjects were randomly selected for blood sampling and the study of inflammatory status. Studied parameters were: detailed anthropometry, fitness and for the evaluation of inflammatory status, serum acute phase proteins (C-reactive protein, ceruloplasmin and complement factors C3 and C4), as well as in vitro production of interleukin-6 and tumor necrosis factor-cc by peripheral blood mononuclear cells.

The main result of this thesis was that overweight adolescents had moderately raised inflammatory markers, which indicates that this population is in a state of chronic low-grade inflammation. Correlations between most body fat estimates and acute phase proteins suggest a proinflammatory action of the adipose tissue. Moreover, central obesity seems to be an independent determinant of C3 concentrations. Overweight was associated with low-grade inflammation independently of fitness status, suggesting that the modulation is mediated by body fat rather than fitness status. C3 however, was independently associated with fitness and could be a new biomarker or involved in the mechanisms of the health benefits of fitness.

Whether low-grade inflammation is predicting future diseases or is merely a practical marker of body fat, is beyond the possible answers of this thesis, but nevertheless, this outcome points to the importance of maintaining an appropriate body weight to keep inflammatory status low which could eventually contribute to improve the health status of the next generation's adult population.

List of scientific papers

I. Moreno LA, Mesana MI, Gonzalez-Gross M, Gil CM, Fleta J, Warnberg J, Ruiz JR, Sarria A, Marcos A, Bueno M; The AVENA Study Group (2006). Anthropometric body fat composition reference values in Spanish adolescents. The AVENA Study. Eur J Clin Nutr. 60(2): 191-6.
https://doi.org/10.1038/sj.ejcn.1602285

II. Warnberg J, Moreno LA, Mesana MI, Marcos A; AVENA group (2004). Inflammatory mediators in overweight and obese Spanish adolescents. The AVENA Study. Int J Obes Relat Metab Disord. Suppl 3: S59-63.
https://doi.org/10.1038/sj.ijo.0802809

III. Warnberg J, Nova E, Moreno LA, Romeo J, Mesana MI, Ruiz RJ, Ortega FB, Sjostrom M, Bueno M, Marcos A, the AVENA study group (2006). Inflammatory proteins are related with total and abdominal adiposity in a healthy adolescent population. The AVENA study. [Submitted]

IV. Warnberg J, Sjostrom M, Ruiz J, Moreno LA, Nova E, Ortega FB, Mesa JL, Romeo J, Montero A, Marcos A, the AVENA study group (2006). Association of fitness and fatness to low-grade systemic inflammation in adolescents. The AVENA study. [Manuscript]