Nutritional supplementation with some
amino acids may influence host's responses and also certain mechanism involved in
tumor progression. It is known that exercise influences
body weight and muscle composition. Previous findings from our group have shown that
leucine has beneficial effects on
protein composition in cachectic rat model as the Walker 256
tumor. The main purpose of this study was to analyze the effects of light exercise and
leucine and/or
glutamine-rich diet in body composition and skeletal muscle
protein synthesis and degradation in young
tumor-bearing rats. Walker
tumor-bearing rats were subjected to light aerobic exercise (swimming 30 min/day) and fed a
leucine-rich (3%) and/or
glutamine-rich (4%) diet for 10 days and compared to healthy young rats. The carcasses were analyzed as total water and fat body content and lean body mass. The gastrocnemious muscles were isolated and used for determination of total
protein synthesis and degradation. The chemical body composition changed with
tumor growth, increasing body water and reducing body fat content and total body
nitrogen. After
tumor growth, the
muscle protein metabolism was impaired, showing that the
muscle protein synthesis was also reduced and the protein degradation process was increased in the gastrocnemius muscle of exercised rats. Although short-term exercise (10 days) alone did not produce beneficial effects that would reduce
tumor damage, host
protein metabolism was improved when exercise was combined with a
leucine-rich diet. Only total carcass
nitrogen and
protein were recovered by a
glutamine-rich diet. Exercise, in combination with an
amino acid-rich diet, in particular,
leucine, had effects beyond reducing tumoral weight such as improving
protein turnover and carcass
nitrogen content in the
tumor-bearing host.