Hormone-related, muscle-specific changes in protein metabolism and fiber type profile after faba bean intake

Abstract

Male growing Wistar rats were fed, over 15 days, isoenergetic (16.72 ± 0.49 MJ) and isoproteic (11%) diets containing either lactalbumin or raw Vicia faba L. (Vf) as the sole source of protein. Compared with pair-fed controls (PF), soleus muscles of Vf-fed rats showed increased ( P < 0.05) synthesis and breakdown rates. In addition, the soleus of Vf-fed rats displayed a decrease ( P < 0.05) in type I and an increase ( P < 0.01) in type IIc fibers compared with that of PF animals. On the contrary, extensor digitorum longus muscles of both Vf-fed and PF rats showed an increase ( P < 0.01) in type I and a reduction ( P < 0.05) in type IIb fibers together with a decrease ( P < 0.05) in the cross-sectional area of the latter fibers. Vf-fed rats exhibited a significant decrease in serum insulin ( P < 0.05) and thyrotropin ( P < 0.01) levels, together with an increase in plasma glucagon ( P < 0.05) and 3,5,3′-triiodothyronine ( P < 0.01) concentrations, compared with the PF group. Both Vf-fed and PF rats experienced an increase in corticosterone concentrations ( P < 0.01 vs. control; P < 0.05 vs. PF). The muscle-specific changes in both protein metabolism and fiber type composition may partly depend on the hormonal changes that were observed after Vf intake.