Downhill Running-Based Overtraining Protocol Improves Hepatic Insulin Signaling Pathway without Concomitant Decrease of Inflammatory Proteins

Abstract

The purpose of this study was to verify the effects of overtraining (OT) on insulin, inflammatory and gluconeogenesis signaling pathways in the livers of mice. 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). Rotarod, incremental load, exhaustive and grip force tests were used to evaluate performance. Thirty-six hours after a grip force test, the livers were extracted for subsequent protein analyses. The phosphorylation of insulin receptor beta (pIRbeta), glycogen synthase kinase 3 beta (pGSK3beta) and forkhead box O1 (pFoxo1) increased in OTR/down versus CT. pGSK3beta was higher in OTR/up versus CT, and pFoxo1 was higher in OTR/up and OTR versus CT. Phosphorylation of protein kinase B (pAkt) and insulin receptor substrate 1 (pIRS–1) were higher in OTR/up versus CT and OTR/down. The phosphorylation of IκB kinase alpha and beta (pIKKalpha/beta) was higher in all OT protocols versus CT, and the phosphorylation of stress-activated protein kinases/Jun amino-terminal kinases (pSAPK-JNK) was higher in OTR/down versus CT. Protein levels of peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PGC-1alpha) and hepatocyte nuclear factor 4alpha (HNF-4alpha) were higher in OTR versus CT. In summary, OTR/down improved the major proteins of insulin signaling pathway but up-regulated TRB3, an Akt inhibitor, and its association with Akt.

Nonfunctional overreaching and hepatic adaptations of APPL1 and APPL2

“…Taken together, these results indicated that APPL1 could be part of the molecular mechanism that contributes to the glucose homeostasis in the liver of overtrained mice. Da Rocha et al 3 using the same liver samples of the current investigation verified that mice from the OTR/down group improved some initial proteins of the hepatic insulin signaling pathway, but upregulated the TRB3 and its association with Akt, implying a limitation on this downstream point of the insulin signaling pathway. The authors also observed high levels of hepatic glycogen 3 , which leads to the hypothesis that another molecule could be responsible for this result especially in the OTR/down and OTR/up groups.…”

“…Although the other two OT protocols performed in uphill and without inclination led to similar decrements in the analyzed performance parameters 3,12,13 , they induced particular modulations of the hepatic insulin signaling pathway 3 . Thus, we also evaluated their effects on the hepatic protein levels of APPL1 and APPL2.…”

“…The resting interval between daily sessions during the eighth week was 4h. The performance evaluations were made on week 0 and 48 h after the last sessions of the OT protocols at the end of week 8 and consisted of a rotarod test 12,14,15 , the ILT 3,12,14,[16][17][18] , an exhaustive test 3,12,14,[16][17][18] and a grip force test 3,12,14,[16][17][18] . The description of these tests and their results were recently published 3 using the same sample as the current study.…”

“…Recently, da Rocha et al 3 verified that mice in NFOR, induced by an OT protocol based on downhill running sessions, presented an improvement of the hepatic insulin signaling pathway when compared to other two OT protocols with the same external load (i.e., the product between intensity and volume of training), but performed in uphill and without inclination. Also, these mice displayed high phosphorylation status of the glycogen synthase kinase 3 beta (GSK-3beta), a direct target that is phosphorylated and inactivated by the protein kinase B (Akt).…”

“…When GSK-3beta is not phosphorylated, the glycogen synthase activity is inhibited, and the glycogen storage is decreased 4 . Interestingly, these mice showed increased levels of hepatic glycogen even with high contents of tribbles-like protein 3 (TRB3), an Akt inhibitor 3 . These contradictory results may be better elucidated with the investigation of other proteins that are involved in this pathway modulation, such as the adaptor proteins APPL1 and APPL2.…”