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Whey protein hydrolysate (WPH) is capable of increasing muscle glycogen reserves and of concentrating the glucose transporter in the plasma membrane (PM). The objective of this study was to determine which WPH components could modulate translocation of the glucose transporter GLUT-4 to the PM of animal skeletal muscle. Forty-nine animals were divided into 7 groups (n=7) and received by oral gavage 30% glucose plus 0.55 g/kg body mass of the following WPH components: (a) control; (b) WPH; (c) L-isoleucine; (d) L-leucine; (e) L-leucine plus L-isoleucine; (f) L-isoleucyl-L-leucine dipeptide; (g) L-leucyl-L-isoleucine dipeptide. After receiving these solutions, the animals were sacrificed and the GLUT-4 analysed by western blot. Additionally, glycogen, glycaemia, insulin and free amino acids were also determined by standard methods. Of the WPH components tested, the amino acid L-isoleucine and the peptide L-leucyl-L-isoleucine showed greater efficiency in translocating GLUT-4 to the PM and of increasing glucose capture by skeletal muscle.

Whey protein has been suggested to be potential protective agent against various forms of stress. The heat shock protein HSP70 confers greater cellular tolerance against stressors. The present study evaluated the effects of whey protein intake on HSP70 expression. Forty-eight male Wistar rats were divided into sedentary and exercised groups, and each group was fed as a protein source casein (CAS), whey protein (WP) or whey protein hydrolysate (WPH) for 3weeks. Exercise on a treadmill was used as the source of stress in the animals from the exercised group. The results showed a larger increase in HSP70 expression in the soleus, gastrocnemius and lung of the WPH-fed rats than WP or casein-fed rats. HSP70 expression in the sedentary rats was very low, independent of the diet or tissue. Protein carbonyls were lower in the group that consumed WPH. These data suggest that the consumption of WPH enhances HSP70 expression.