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The Effect of β-GPA on the Markers of Anabolic and Catabolic Signaling Pathways in Rat Soleus Muscle at the Initial Stage of Hindlimb Unloading
Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology  (IF),  Pub Date : 2020-01-01, DOI: 10.1134/s1990747819060102
N. A. Vilchinskaya, E. P. Mochalova, I. I. Paramonova, S. P. Belova, T. M. Mirzoev, B. S. Shenkman

Abstract — Molecular mechanisms initiating the development of atrophic changes in a mammalian postural muscle remain unclear. We have suggested that AMP-activated protein kinase (AMPK) may play an important role in the regulation of anabolic and catabolic signaling pathways in postural muscle at the initial stage of mechanical unloading, since skeletal muscle inactivation can lead to changes in the balance of intramuscular high-energy phosphates. Beta-guanidinopropionic acid (β-GPA) can act as a modulator of the balance of high-energy phosphates, application of which can reduce the content of intracellular high-energy phosphates. The purpose of this study was to assess signaling pathways of protein synthesis and degradation in rat soleus muscle after preliminary treatment with β-GPA followed by 1-day hindlimb unloading. The experiments were performed on male Wistar rats, which were divided into the following groups: (1) vivarium control (C); (2) vivarium control + β-GPA (C + GPA); (3) 1-day hindlimb unloading (HU); and (4) 1-day hindlimb unloading + β-GPA (HU + GPA). β-GPA was administered daily by intraperitoneal injections (400 mg/kg). The content of the key signaling proteins (AMPK, ACC, p70S6K, 4E-BP1, and FOXO3) was determined by gel electrophoresis followed by immunoblotting. The expression of mRNA of ubiquitin ligases (MuRF1 and MAFbx) was evaluated by real-time PCR. A prevention of reduction in phosphorylation of AMPK, ACC and 4E-BP1 and the return to control values of the increased level of p70S6K phosphorylation were observed in the group with 1-day unloading and β-GPA pretreatment. The phosphorylation of AKT and FOXO3, as well as the expression levels of MuRF1 and MAFbx in the HU + GPA group did not differ from the HU group. The obtained data indicate that the AMPK activity may play an important role in the modulation of anabolic mTORC1-signaling in rat soleus muscle at the early stage of simulated microgravity.