Bioactivity of food peptides: biological response of rats to bovine milk whey peptides following acute exercise

Abstract

Background: Several physiologically beneficial effects of consuming a whey protein hydrolysate (WPH) have been attributed to the greater availability of bioactive peptides. Aims: The aim was to investigate the effect of four branched-chain amino acid- (BCAA-)containing dipeptides, present in WPH, on immune modulation, stimulation of HSP expression, muscle protein synthesis, glycogen content, satiety signals and the impact of these peptides on the plasma free amino acid profiles. Methods: The animals were divided in groups: control (rest, without gavage), vehicle (water), L-isoleucyl-L-leucine (lle-Leu), L-leucyl-L-isoleucine (Leu-lle), L-valyl-Lleucine (Val-Leu), L-leucyl-L-valine (Leu-Val) and WPH. All animals were submitted to acute exercise, except for control. Results: lle-Leu stimulated immune response, hepatic and muscle glycogen and HSP60 expression, whereas Leu-Val enhanced HSP90 expression. All dipeptides reduced glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, no changes were observed on leptin. All peptides inhibited NF-kB expression. The plasma amino acid time-course showed peptide-specific and isomer-specific metabolic features, including increases of the BCAAs. Conclusion: The data indicate that lle-Leu was effective to attenuate immune-suppression exercise-induced, promoted glycogen content and stimulated anti-stress effect (HSP). Furthermore, Leu-Val increased HSP90, p-4EBP1, p-mTOR and p-AMPK expression. The data suggest the involvement of these peptides in various beneficial functions of WPH consumption.

Keywords: Bioactive peptides; HSP; glycogen; immune; whey protein hydrolysate.

Figure 1.

Means (± SEM) of the Western blot analysis (n = 8): HSP90 (a), HSP60 (b), OGT (c), NF-kB p65 (d), BCKDH (e), p-AMPK (f), p-mTOR (g), p-4EBP1 (h), IDE (i), p-AKT (j), p85 (k). Different letters represent significant differences (p < 0.05). GAPDH is loading control. Groups: control (rest, without gavage), vehicle (water), L-isoleucyl-leucine (lle-Leu), L-leucyl-isoleucine (Leu-lle), L-valyl-leucine (Val-Leu), L-leucyl-valine (Leu-Val) and whey protein hydrolysate (WPH).

Figure 2.

Means (± SEM) for glycogen content: (a) liver (b) heart (c) muscle (d) kidney. Means (± SEM) for serum biochemical parameters: (e) insulin, (f) C-peptide, (g) GIP, (h) GLP-1, (i) leptin, (j) IL-1β, (k) IL-10, (l) free glutamine (μmol/L). Different letters represent significant differences (p < 0.05). Groups: Control (rest, without gavage), vehicle (water), L-isoleucyl-leucine (lle-Leu), L-leucyl-isoleucine (Leu-lle), L-valyl-leucine (Val-Leu), L-leucyl-valine (Leu-Val) and whey protein hydrolysate (WPH).

Figure 3.

Plasma free amino acids profile (μmol/L) showing the time-course: (a) plasma leucine, (b) Leucine area under the curve (AUC), (c) plasma glutamate levels, (d) Glutamate AUC, (e), plasma isoleucine levels, (f) Isoleucine AUC, (g) plasma serine, (h) Serine AUC, plasma valine (i), Valine AUC (j), glycine levels (k), Glycine AUC (l), plasma tryptophan (m), tryptophan AUC (n), plasma taurine (o), Taurine AUC (p), plasma cystine (q), cystine AUC (r), plasma arginine (s), arginine AUC (t), plasma lysine levels (u), lysine AUC (v), plasma alanine (x), Alanine AUC (z). Different letters represent significant differences (p < 0.05). Groups: vehicle (water), L-isoleucyl-leucine (lle-Leu), L-leucyl-isoleucine (Leu-lle), L-valyl-leucine (Val-Leu), L-leucyl-valine (Leu-Val) and whey protein hydrolysate (WPH). The time-course was done up to 60 minutes because the values of amino acids mostly returned to baseline levels. The vehicle (water) group for this analysis was used as control.