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  • Author: Adelino S R da Silva x
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Bruno C Pereira, Alisson L da Rocha, Ana P Pinto, José R Pauli, Leandro P de Moura, Rania A Mekary, Ellen C de Freitas and Adelino S R da Silva

The main aim of this investigation was to verify the effects of overtraining (OT) on the insulin and inflammatory signaling pathways in mice skeletal muscles. Rodents were divided into control (CT), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up), and overtrained by running without inclination (OTR) groups. Rotarod, incremental load, exhaustive, and grip force tests were used to evaluate performance. Thirty-six hours after the grip force test, the extensor digitorum longus (EDL) and soleus were extracted for subsequent protein analyses. The three OT protocols led to similar responses of all performance evaluation tests. The phosphorylation of insulin receptor beta (pIRβ; Tyr), protein kinase B (pAkt; Ser473), and the protein levels of plasma membrane glucose transporter-4 (GLUT4) were lower in the EDL and soleus after the OTR/down protocol and in the soleus after the OTR/up and OTR protocols. While the pIRβ was lower after the OTR/up and OTR protocols, the pAkt was higher after the OTR/up in the EDL. The phosphorylation of IκB kinase alpha and beta (pIKKα/β; Ser180/181), stress-activated protein kinases/Jun amino-terminal kinases (pSAPK-JNK; Thr183/Tyr185), factor nuclear kappa B (pNFκB p65; Ser536), and insulin receptor substrate 1 (pIRS1; Ser307) were higher after the OTR/down protocol, but were not altered after the two other OT protocols. In summary, these data suggest that OT may lead to skeletal muscle insulin signaling pathway impairment, regardless of the predominance of eccentric contractions, although the insulin signal pathway impairment induced in OTR/up and OTR appeared to be muscle fiber-type specific.

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Ana P Pinto, Alisson L da Rocha, Eike B Kohama, Rafael C Gaspar, Fernando M Simabuco, Fabiani G Frantz, Leandro P de Moura, José R Pauli, Dennys E Cintra, Eduardo R Ropelle, Ellen C de Freitas and Adelino S R da Silva

The endoplasmic reticulum (ER) stress and inflammation relationship occurs at different levels and is essential for the adequate homeostatic function of cellular systems, becoming harmful when chronically engaged. Intense physical exercise enhances serum levels of interleukin 6 (IL-6). In response to a chronic exhaustive physical exercise protocol, our research group verified an increase of the IL-6 concentration and ER stress proteins in extensor digitorium longus (EDL) and soleus. Based on these results, we hypothesized that IL-6-knockout mice would demonstrate a lower modulation in the ER stress proteins compared to the wild-type mice. To clarify the relationship between exercise-induced IL-6 increased and ER stress, we studied the effects of an acute exhaustive physical exercise protocol on the levels of ER stress proteins in the skeletal muscles of IL-6-knockout (KO) mice. The WT group displayed a higher exhaustion time compared to the IL-6 KO group. After 1 h of the acute exercise protocol, the serum levels of IL-6 and IL-10 were enhanced in the WT group. Independent of the experimental group, the CHOP and cleaved caspase 12/total caspase 12 ratio in EDL as well as ATF6 and CHOP in soleus were sensitive to the acute exercise protocol. Compared to the WT group, the oscillation patterns over time of BiP in EDL and soleus as well as of peIF2-alpha/eIF2-alpha ratio in soleus were attenuated for the IL-6 KO group. In conclusion, IL-6 seems to be related with the ER stress homeostasis, once knockout mice presented attenuation of BiP in EDL and soleus as well as of pEiF2-alpha/EiF2-alpha ratio in soleus after the acute exhaustive physical exercise protocol.