Physical performance and school physical education in overweight Spanish children.

AIMS: To evaluate the effect of physical performance and extracurricular organized physical activities (EOPA) in normal- and overweight children. METHODS: A random sample of 1,068 schoolchildren (7-12 years old) representative of the region of Aragon (Spain) was selected and divided into normal-, overweight and obese groups based on previously published body mass index reference standards. Physical performance was assessed by the European physical test battery. EOPA were estimated when children performed at least 3 h per week during the previous year in addition to school physical education. RESULTS: Overweight and obese subjects had lower performances on all tests requiring propulsion or lifting of the body mass (standing-broad jump, sit-ups, bent-arm hangs, speed shuttle run and endurance shuttle run) when compared with normal-weight counterparts (p < 0.001). The overweight and obese children showed greater hand grip strength measures than the normal-weight ones (p < 0.001). Plate tapping and sit reach test scores were similar in both groups. The participation in EOPA was similar in normal- and overweight or obese groups; however, a significant increase with age was observed (p < 0.01). CONCLUSION: In this age group, overweight was not related to EOPA participation. Overweight children had poorer results on weight-bearing tasks. The good results in static strength, coordination and speed of limb movements in overweight children should be considered in the promotion of physical activity programs for overweight children.

Changes in the proteolytic activities of proteasomes and lysosomes in human fibroblasts produced by serum withdrawal, amino-acid deprivation and confluent conditions.

The contribution of the main proteolytic pathways to the degradation of long-lived proteins in human fibroblasts grown under different conditions was investigated. The effects of various commonly used pharmacological inhibitors of protein degradation were first analysed in detail. By choosing specific inhibitors of lysosomes and proteasomes, it was observed that together both pathways accounted for 80% or more of the degradation of cell proteins. With lysosomal inhibitors, it was found that serum withdrawal or amino-acid deprivation strongly stimulated macroautophagy but not other lysosomal pathways, whereas confluent conditions had no effect on macroautophagy and slightly activated other lysosomal pathways. Prolonged (24 h) serum starvation of confluent cultures strongly decreased the macroautophagic pathway, whereas the activity of other lysosomal pathways increased. These changes correlated with electron microscopic observations and morphometric measurements of lysosomes. With proteasomal inhibitors, it was found that, in exponentially growing cells in the absence of serum, activity of the ubiquitin-proteasome pathway increases, whereas under confluent conditions the contribution (in percentage) of proteasomes to degradation decreases, especially in cells deprived of amino acids. Interestingly, in confluent cells, the levels of two components of the 19 S regulatory complex and those of an interchangeable beta-subunit decreased. This was associated with a marked increase in the levels of components of PA28-immunoproteasomes. Thus confluent conditions affect proteasomes in a way that resembles treatment with interferon-gamma. Altogether, these results show that the activity of the various proteolytic pathways depends on the growth conditions of cells and will be useful for investigation of the specific signals that control their activity.

Role of proteasomes in the degradation of short-lived proteins in human fibroblasts under various growth conditions.

Degradation of proteins in the cells occurs by proteasomes, lysosomes and other cytosolic and organellar proteases. It is believed that proteasomes constitute the major proteolytic pathway under most conditions, especially when degrading abnormal and other short-lived proteins. However, no systematic analysis of their role in the overall degradation of truly short-lived cell proteins has been carried out. Here, the degradation of short-labelled proteins was examined in human fibroblasts by release of trichloroacetic acid-soluble radioactivity. The kinetics of degradation was decomposed into two, corresponding to short- and long-lived proteins, and the effect of proteasomal and lysosomal inhibitors on their degradation, under various growth conditions, was separately investigated. From the degradation kinetics of proteins labelled for various pulse times it can be estimated that about 30% of newly synthesised proteins are degraded with a half-life of approximately 1h. These rapidly degraded proteins should mostly include defective ribosomal products. Deprivation of serum and confluent conditions increased the degradation of the pool of long-lived proteins in fibroblasts without affecting, or affecting to a lesser extent, the degradation of the pool of short-lived proteins. Inhibitors of proteasomes and of lysosomes prevented more than 80% of the degradation of short-lived proteins. It is concluded that, although proteasomes are responsible of about 40-60% of the degradation of short-lived proteins in normal human fibroblasts, lysosomes have also an important participation in the degradation of these proteins. Moreover, in confluent fibroblasts under serum deprivation, lysosomal pathways become even more important than proteasomes in the degradation of short-lived proteins.