Lack of β2-AR improves exercise capacity and skeletal muscle oxidative phenotype in mice.
β(2)-adrenergic receptor (β(2)-AR) agonists have been used as ergogenics by athletes involved in training for strength and power in order to increase the muscle mass. Even though anabolic effects of β(2)-AR activation are highly recognized, less is known about the impact of β(2)-AR in endurance capacity. We presently used mice lacking β(2)-AR [β(2)-knockout (β(2) KO)] to investigate the role of β(2)-AR on exercise capacity and skeletal muscle metabolism and phenotype. β(2) KO mice and their wild-type controls (WT) were studied. Exercise tolerance, skeletal muscle fiber typing, capillary-to-fiber ratio, citrate synthase activity and glycogen content were evaluated. When compared with WT, β(2) KO mice displayed increased exercise capacity (61%) associated with higher percentage of oxidative fibers (21% and 129% of increase in soleus and plantaris muscles, respectively) and capillarity (31% and 20% of increase in soleus and plantaris muscles, respectively). In addition, β(2) KO mice presented increased skeletal muscle citrate synthase activity (10%) and succinate dehydrogenase staining. Likewise, glycogen content (53%) and periodic acid-Schiff staining (glycogen staining) were also increased in β(2) KO skeletal muscle. Altogether, these data provide evidence that disruption of β(2)-AR improves oxidative metabolism in skeletal muscle of β(2) KO mice and this is associated with increased exercise capacity.
School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil.
V A
VA
Voltarelli
A V N
AV
Bacurau
L R G
LR
Bechara
C R
CR
Bueno
L H M
LH
Bozi
K C
KC
Mattos
V M C
VM
Salemi
P C
PC
Brum
D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D017079:Exercise Tolerance / Q000502:physiology; D006003:Glycogen / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018656:Muscle Fibers, Fast-Twitch; D018657:Muscle Fibers, Slow-Twitch; D018482:Muscle, Skeletal / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*; D010084:Oxidation-Reduction; D010641:Phenotype; D010807:Physical Endurance / Q000235:genetics / Q000502:physiology*; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000502:physiology*; D013385:Succinate Dehydrogenase / Q000378:metabolism
D018343:Receptors, Adrenergic, beta-2; D006003:Glycogen; D013385:Succinate Dehydrogenase; D002950:Citrate (si)-Synthase