In this study we report that, unlike the case of obese or high-fat fed animals, consumption of a whey protein hydrolyzate can have a min imal impact on skeletal muscle metabolic gene exp ression in sedentary eutrophic rats and still a moderate effect on body fat. Male Wistar rats were fed diets with either whey-protein concentrate (WPC), a whey-protein hydrolyzate (WPH) o r casein (CAS), during two weeks. Gastrocnemius and blood were withdrawn for analysis of the expression of the PPARα, PPA

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... PGC-1α, CPT-1β and myostatin genes, classical serum parameters, non-esterified fatty acids (NEFA ), triacylg lycerols (TA G), albu min, alanine and aspartate aminotransferases (ALT, AST), in addit ion to muscle and serum free amino acid profiles. The diet appeared to have no effect on the expression of any of the muscle genes besides, no significant changes being observed in serum NEFA, TA G or creatinine. Co mpared to CAS, the animals fed either WPC or WPH exh ibited lower activ ities of A LT, AST, together with higher seru m albu min levels in the WPC g roup. It was also observed that the diets containing the whey proteins produced increased levels of serum glycine, whereas in the muscle several amino acids were increased in the animals that consumed WPH. Although the whey protein d iets did have an effect on the profile of free muscle amino acids and improved the outcome of classical enzy me bio markers, consumption did not result in the exacerbation of such parameters of normal an imals consuming normo lip idic d iets.