Effects of the beta2 agonist formoterol on atrophy signaling, autophagy, and muscle phenotype in respiratory and limb muscles of rats with cancer-induced cachexia

Muscle mass loss and wasting are characteristic features of patients with chronic conditions including cancer. Beta-adrenoceptors attenuate muscle wasting. We hypothesized that specific muscle atrophy signaling pathways and altered metabolism may be attenuated in cancer cachectic animals receiving treatment with the beta2 agonist formoterol. In diaphragm and gastrocnemius of tumor-bearing rats (intraperitoneal inoculum, 108 AH-130 Yoshida ascites hepatoma cells, 7-day study period) with and without treatment with formoterol (0.3 mg/kg body weight/day/7days, subcutaneous), atrophy signaling pathways (NF-κB, MAPK, FoxO), proteolytic markers (ligases, proteasome, ubiquitination), autophagy markers (p62, beclin-1, LC3), myostatin, apoptosis, muscle metabolism markers, and muscle structure features were analyzed (immunoblotting, immunohistochemistry). In diaphragm and gastrocnemius of cancer cachectic rats, fiber sizes were reduced, levels of structural alterations, atrophy signaling pathways, proteasome content, protein ubiquitination, autophagy, and myostatin were increased, while those of regenerative and metabolic markers (myoD, mTOR, AKT, and PGC-1alpha) were decreased. Formoterol treatment attenuated such alterations in both muscles. Muscle wasting in this rat model of cancer-induced cachexia was characterized by induction of significant structural alterations, atrophy signaling pathways, proteasome activity, apoptotic and autophagy markers, and myostatin, along with a significant decline in the expression of muscle regenerative and metabolic markers. Treatment of the cachectic rats with formoterol partly attenuated the structural alterations and atrophy signaling, while improving other molecular perturbations similarly in both respiratory and limb muscles. The results reported in this study have relevant therapeutic implications as they showed beneficial effects of the beta2 agonist formoterol in the cachectic muscles through several key biological pathways.The authors are thankful to Dr. Ester Puig-Vilanova for her technical assistance with part of the biological experiments and to Mr. Xavier Duran for his support with all the statistical analyses and study design. The current research has been supported by Instituto de Salud Carlos-III, contract grant numbers, CIBERES, FIS 14/00713 (FEDER); Spanish Ministry of Science and Innovation, contract grant number SAF 2011-26091; Spanish Respiratory Society (SEPAR), contract grant numbers, SEPAR 2013 and SEPAR 2016; Catalan Foundation of Pulmonology (FUCAP), contract grant numbers, FUCAP 2011, FUCAP 2012, and 2016