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Previous studies have shown that hydrolyzed proteins exhibit antioxidant properties and may confer physical and physiological advantages when consumed by the exercising rat. The purpose of this study was to compare the effects of feeding either intact (I) and partly hydrolyzed (H) milk whey proteins on gastrocnemial DNA contents and protein metabolism in exercising Wistar rats. Protein synthesis and degradation, protein and DNA contents, and concentration of the serum insulin-like growth factor-1 (IGF1) were determined in six experimental groups according to the type of protein consumed [casein (C), whey protein isolate (I), hydrolyzed whey protein (H) and level of physical activity (sedentary (S) and trained (T)]. H produced significantly lower rates of protein synthesis and degradation and DNA contents in the gastrocnemius, while no differences were observed in the total muscle protein content and serum levels of IGF1. These results indicate that consumption of prehydrolyzed whey protein alters muscle metabolism resulting in less DNA, but maintains the muscle protein levels constant and sustain or improves physical performance, compared to the unhydrolyzed protein.

Background: Skeletal muscle atrophy occurs in several pathological conditions such as cancer, a condition termed cancer cachexia. This condition is associated with an increase in morbidity and poor treatment response, decreasing quality of life, and increased mortality in cancer patients. A leucine-rich diet could be used as a coadjutant therapy preventing muscle atrophy in cancer cachexia hosts. Besides muscle atrophy, muscle function loss is even more important to the patient’s quality of life. Therefore, this study aimed to evaluate the effects of leucine-rich diet on muscle function activity of cachectic Walker 256 tumor-bearing rats and to correlate such effects with molecular pathways of muscle atrophy. Methods: Adult Wistar rats were randomly distributed into four experimental groups. Two groups were fed with a control diet: Control (C) and Walker 256 tumor-bearing (W), and two other groups were fed with a leucine-rich diet: Leucine Control (L) and Leucine Walker 256 tumor-bearing (LW). The functional analysis (walking, behavior, and strength tests) was measured and before and after tumor inoculation. Cachexia parameters such as body weight loss, muscle and fat mass, pro-inflammatory cytokine profile, and molecular and morphological aspects of skeletal muscle were also performed. Results: Walker 256 tumor growth led to muscle function decline, cachexia manifestation symptoms, muscle fiber cross-section area reduction, associated with the altered morphological pattern and classical muscle protein degradation pathway activation, with up-regulation of FoXO1, MuRF1, and 20S proteins. On the other hand, a leucine-rich diet improved muscle strength while reducing the decline of walking and behavior, partially improving the cachexia manifestations and preventing muscle atrophy and protein degradation in Walker 256 tumor-bearing rats. Conclusions: A leucine-rich diet diminished muscle protein degradation and enhanced oxidative pathways, leading to better muscle functional performance.

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