Lack of beta(2)-AR improves exercise capacity and skeletal muscle oxidative phenotype in mice

beta(2)-adrenergic receptor (beta(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 beta(2)-AR activation are highly recognized, less is known about the impact of beta(2)-AR in endurance capacity. We presently used mice lacking beta(2)-AR [beta(2)-knockout (beta(2) KO)] to investigate the role of beta(2)-AR on exercise capacity and skeletal muscle metabolism and phenotype. beta(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, beta 2KO 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, beta 2KO 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 beta 2KO skeletal muscle. Altogether, these data provide evidence that disruption of beta(2)AR improves oxidative metabolism in skeletal muscle of beta 2KO mice and this is associated with increased exercise capacity.

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo, Sao Paulo SP (FAPESP)

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo, Sao Paulo - SP (FAPESP) [2008/56483-1]

Conselho Nacional de Pesquisa e Desenvolvimento Brasil (CNPq PIBIC)

Conselho Nacional de Pesquisa e Desenvolvimento - Brasil (CNPq - PIBIC) [110792/2005-0]

FAPESP

FAPESP [2010/50048-1]

Conselho Nacional de Pesquisa e Desenvolvimento (CNPq)

Conselho Nacional de Pesquisa e Desenvolvimento (CNPq) [302201/2011-4]