Milk whey proteins and leucine supplementation: influence on biochemical and body compositional parameters, and on the physical performance of exercising wistar rats

Abstract

Under special health conditions it is essential to stimulate anabolism and reduce catabolism. The milk whey proteins are known to have an amino acid balance favorable to anabolism, while leucine supplementation is involved in the inhibition of protein catabolism and exercise has been also known as an important anabolic stimulus. Leucine supplementation, however, has not been studied in association with physical activity, for long periods of time, or in multiple doses. Objective: with this work we intend to develop a strategy to stimulate anabolism, while reducing catabolism, by testing a combination of dietary milk whey protein with leucine supplementation, combined with physical exercise in young rats in 30-day feeding trials. We expect to obtain a dose-response curve on body composition of rats fed three different basal proteins and supplemented with leucine: a group of animals will be consuming intact milk whey proteins (WPI), or hydrolyzed whey proteins (WPH), or the standard casein, all of which being either exercised or sedentary. Methods: 96 male Wistar (21 days) rats will be divided into 16 [n=6] groups and receive either the AIN93 diet with casein (C), or that but with WPI, or WPH, instead of the casein as protein sources, and supplemented with either: 0, 3.0, 4.5, or 6.0% L-leucine. Each of the diet groups [n=12] will still be subdivided into exercised and sedentary, making up the 24 groups. Therefore, as an example, the diet groups for the WPI can be defined as: WPI; WPI + 3% leucine, WPI; WPI + 4.5% leucine; and WPI + 6% leucine. Each of these groups will be divided into exercised and sedentary. Following the same rationale for each source of dietary protein and applying a standard exercise protocol, the parameters to be analyzed are: food intake, weight gain, time to exhaustion; profile of amino acids in plasma and muscle, body composition of the animals, activities of CK, LDH, ALT, AST, mTOR and plasma insulin biomarkers. (AU)